Sunday, July 17, 2011

The Industrial Waste Management


Nigeria with its population of 182,091,542,140 million (2007 release) is urbanizing at an astonishing pace with increasing industrialization, Over 5000 process industries are concentrated in major urban centers such as Lagos, Sango-Ota, Port Harcourt, Ibadan, Aba, Kaduna, and Kano to name a few. These industries vary from textile plants, breweries, slaughterhouses, refineries, pulp and paper, tarpaulin, rubber and plastics. Nigeria’s urban population increased from 20 per cent in 1970 to about 38 per cent in 1993. There are over 40 million people now living in cities and the urban population is increasing at 5.5 per cent per annum. It was observed that almost every industry dumps its waste on the backyard without concern for the environment around. Some of these wastes along with their leachates are seen mixed with hazardous wastes and joining streams and rivers through a network of open drains. This environmental degradation is felt in every walk of life. Though a large volume of literature is available on the quality of wastes generated and their dispersion into the environment, very little information is available on the quantity of wastes, their fate and the management practices in Nigeria. Most of the industries dispose their wastes without any treatment only to be removed and dumped elsewhere. There has been an environmental policy on ground but the implementation strategy is weak or ineffective in most of the States. This paper examines the broad groups of industries, the nature of wastes (both liquid and solid) generated by them and the technological options for effective management.

Industrial wastes

Industrial wastes may be grouped into 2 broad categories: Process wastes and chemical wastes. The process wastes depend on the nature of the industry, the raw materials processed and nature of the process itself. Some of the manufacturing methods that generate such wastes are:
• sedimentation,
• flocculation,
• washing,
• filtering,
• evaporation,
• distillation,
• electrolysis,
• absorption,
• crystallization,
• screening,
• burning, and
• centrifuging,
to name a few. These wastes cause pollution of water, soil, and air depending on the nature of the pollutant, the concentration and the magnitude of the discharge (Box 1). The industrial wastes may be solid, liquid or gaseous. Some may be thermal in nature.

The common pollution problems threatening the environment include oxygen depletion of water bodies, fish kills emission of noxious gases and change in flora and fauna leading to biodiversity loss. In water they contribute to high pollution load, colour changes, turbidity, odour, heat, particulate matter, dissolved solids, BOD, COD, various inorganic elements, volatile organic compounds, toxic chemicals and others.

Similarly, the solid wastes and their leachates entering the water and food chains may effect the environment and health. At the moment, a majority of the industries either treat their wastes minimally or do not treat at all. There is no segregation of wastes and as a result hazardous and non-hazardous, and infectious mix together and go in the waste stream.

Some of the major industries and their waste characteristics are given in Box 2. The options for industrial waste disposal are to discharge into surface waters, coastal waters, land and sewers, if available. Depending on where they are disposed, the effluent quality has to be maintained. The flow rates, weather conditions, the characteristics of the receiving body, and the waste characteristics over a time scale are required before planning a treatment technology.

Developments in waste water management

There is a need to treat industrial wastes whether they are hazardous or not as they contain pollutants above the national specified limits. Hazardous components have to be detoxified and others have to be brought back into the cycle of life. Several developments have taken place during the last century to manage the wastes.

In the earlier days it was thought that “solution to pollution is dilution” and this approach never yielded any positive result. The chemical coagulation using lime, ferric salts and alum did not yield any significant results and on the other hand the rivers have deteriorated to a great extent due to the dissolved impurities which can escape the chemical methods.

The available technologies for treating liquid wastes are:
• Primary treatment: Sedimentation tanks, pH control, Floatation, etc.;
• Secondary treatment: Trickling or percolating filters, Activated sludge process, Oxidation pond, Oxidation ditches, Root Zone Technology, Sludge digestion, Aerobic and anaerobic lagoon;
• Tertiary treatment: Physico-chemical methods, filtration using granular activated carbon, diatomaceous earth etc., reverse osmosis, membrane filtration, Phyto-techniques,
Balancing of various streams and pretreatment are essential before sending for secondary / biological treatment.

In the wastewater treatment, the technology option depends on the goal. One should find out which element or substance is to be reduced or eliminated from the effluents. BOD, SS, Volatile organics, some specific chemicals such as P, N, S, or heavy metals or toxic chemicals have to be addressed. On certain situations adsorbents such as activated charcoal, clays (kaolin or bentonite) may be very useful particularly for colour, heavy metals and volatile organics.

Solid wastes and their management

Indiscriminate disposal of solid wastes (including the hazardous or infectious wastes) which is the normal practice in many urban centres, causes damage to the environment and affect health of the communities. Environmental damage may occur in the form of ecological disturbances such as:
- Blockage of drains and stream flows resulting in flood disasters
- Fire hazards when the wastes are dry
- Obnoxious smell, gaseous and smoke emissions
- Breeding site for rats, flies and other vectors of public health importance
- Harbours and act as reservoir of infectious agents
- Offers a venue for stray animals, destitutes, and lunatics
- Eutrophication of water bodies,
- Death of useful flora and fauna of aquatic or terrestrial systems
- Biodiversity loss
- Morbidity or mortality of populations due to injuries and infections

The solid wastes, particularly the municipal solid wastes, crop residues from agro-based industries, and livestock dung are rich in organic matter and other essential nutrients such as nitrogen, phosphorus and potassium and micronutrients. They are highly putrescible and favour breeding of flies, and harbour pathogens that cause tetanus, Clostridium that produces toxins in foods, and other infectious agents which may enter water, soil and food.

The leachates are particular concern a they may be toxic and high in BOD and COD, particulate matter and dissolved matter. Hey may also promote mosquito breeding when stagnant or contaminate ground water and land. The solid wastes in developing countries are normally mixed with other wastes from human and developmental activities, such as metals, glass, plastics and a host of human utilities. Some of these have great potential for recycling if properly segregated, collected and utilized.

In waste management practice, various steps are involved. Collection, storage, transportation and hygienic disposal are the major phases of waste management. Most often we fail at the proper collection stage. There is need for appropriate tools and equipment for all the stages involved. Wherever possible, one should think of using appropriate materials, tools and technology. As much as possible, one should aim at waste minimization, reuse, and recycling before dumping the wastes into a dustbin. Recycling the non-biodegradables will help the environment, individual and the local industry which needs cheaper raw material for pruduction. If this has to be successful, separation should start at source. There are many industries that recycle these materials. The Shaki Township has metal recyclers, numbering over 3000. There are over 100 plastic recyclers in Lagos, in Ibadan and practically every city in Nigeria. There is money in it both for the householder, the picker and even the industry, which gains through the use of recycled raw materials.

For final disposal, some of the accepted methods include:
• sanitary landfill,
• composting,
• incineration
• fixing in inert materials such as glass and buried under deep soils or abandoned mines (e.g. toxic and radioactive wastes);

Various Governments have in recent years banned the practice of sea disposal, as the seas all around are grossly polluted resulting in the kill of fish, whales and other animals. The ultimate objective of waste treatment is to fully oxidize the basic elements (Carbon, Nitrogen, Phosphorus, and Sulphur) so that they will not deteriorate the water, soil or air around us. It is wiser to recycle the organic wastes to benefit the barren agricultural land, which is vast in the country. Organic fertilizer / manure or compost is very helpful even in controlling desertification as it can promote greening the deserts. The Pace Setter Fertilizer plant at Bodija market in Ibadan has received the attention of various people and establishments all over the world. Recently the UN and Dubai Municipality have awarded the “Best Practice Award” to this venture. Organic manure has helped Denmark in reviving the contaminated land in a fishing village where an industry polluted groundwater and soil with mercury arising from a pesticide industry. Integrated waste management is economical and viable. In Nigeria today, there are 7 waste recycling plants developed by us for waste recycling.

One of the best methods of industrial waste management is found in Denmark at ‘Komunikemi’. Here the Government provided the facility and the industries send their hazardous wastes and pay for the treatment or disposal. Incineration, landfill and composting activities are put at a common place in an integrated manner. Private sector brings the wastes and pay for the facility services. Appropriate technology is used depending on the nature of waste. Payment of fee depends on the nature and quantity of the waste being processed. Certain emerging wastes such as radioactive and electronic wastes (e-wastes) have to be treated in a different way and some level of pretreatment / special treatment is required. Nigeria has also brought out Healthcare waste management policy. There are colour codes and specifications for various phases of waste handling and management.

Conclusions and Recommendations

Hitherto, in Nigeria the emphasis in waste management has been limited to assessment including EIA, EAR and Risk assessment. Proper handling practices and treatment are not practiced in many industries in the country. The regulatory bodies on the other hand have been very sympathetic and have been giving ‘holiday’ for not implementing any treatment facilities. Almost after 13 years of its creation, FEPA (Ministry of Environment where appropriate) have to go into action on enforcing effective treatment and adhering to the stipulated standards.
• There is need to strengthen Federal, State and selective private laboratories to cope with the needs and demand of waste characterization;
• At the moment many unqualified ‘touts’ have entered into the field as ‘Environmental Consultants’; there is need to screen and weed them out;
• Quality assurance, Quality control, inter-laboratory standardization and periodic training and retraining of all ‘Environmental Practitioners’ should be made mandatory;
• Environment is multidisciplinary and in tackling the problems, a team effort is more beneficial; where necessary other disciplines should join hands in solving the problems;
• A National ‘Green Peace’ Group should be formed and encouraged to monitor the industries, communities and regulatory bodies in keeping the environment clean and habitable; and
• There is need to take stock of the availability of technologies and the expertise within the country through proper screening and draft them to address the environmental challenges.

Pollution of water bodies due to solid wastes – an environmental threa




1.1 The association between poor Environmental Sanitation and ill health can be explained in terms of the miasmic theory- bad smells transmitted diseases, but their solution did improve public health. It is on record that improvement in mortality rates from infectious diseases such as typhoid, diarrhea, malaria, tuberculosis, etc, was more of as a result of improved standard of environmental sanitation, than to the knowledge of microbiology or the development of antibiotics. This underscores the importance of sound environmental sanitation in disease prevention and promotion of quality of life.

1.2 There cannot be a healthy nation without healthy environment, and wide raging actions are therefore required to solve environmental sanitation problems in order to reduce and avert their consequential effects. Scientists have been warning over years that an unhealthy population and damaged environment will hinder progress towards developmental goals.

1.3 Environmental Sanitation as crucial as it is, to ensuring a healthy nation, is yet to receive adequate attention it deserves. This trend has contributed significantly to the high prevalence of communicable diseases that have continued to ravage the populace with grave health and economic consequences. Most of these diseases, which include malaria, cholera, typhoid, diarrhoea, pneumonia, tuberculosis and helminthic infestations account for majority of hospital admissions in the country. These diseases are responsible for morbidity, mortality and absenteeism in schools and at work. In addition to this, the Infant Mortality Rate and Child Mortality Rate have continued to rise at figures of 105 and 178 per 1000 live births respectively as of 1999. (FMOH). Majority of the deaths are attributable to communicable diseases. This scenario, is also closely linked with ignorance, wide spread poverty and deprivation as well as moral decadence to the environment. This situation therefore calls for self-discipline, personal hygiene and health promotion.
1.4 The Environmental Sanitation Policy and Programmes have been developed in line with contemporary realities and challenges. The challenges faced by EHOs today are different and more complicated than before. The training, retraining and reorientation of the EHOs to face these modern day challenges are therefore critical to the successful implementation of the Policy and Programmes. It is no gain saying that human resources are the most vital part of the programme implementation. (What are the contemporary issues?) NEEDS, MDGS,etc.

2. The Policy defined Environmental Sanitation as “The principles and practice of effecting healthful and hygienic conditions in the environment to promote public health and welfare, improve quality of life, reduce poverty and ensure a sustainable environment. 1

3. The essential components of environmental sanitation include:
• Housing sanitation including House – to – House Sanitary Inspection of Premises.
• Collection and sanitary disposal of wastes including, solid and liquid wastes.
• Food sanitation.
• Cleaning of streets and drainages.
• Abattoir and markets sanitation including street trading.
• Pest control.
• School sanitation.
• Control of reared and stray of animals.
• Disposal of the dead (man and animals).
• Environmental education.
• Inspection, Monitoring and Enforcement of sanitary regulations.



3.1.1 Sanitary duties mainly by organised sanitary inspection were carried out by the sanitary assistants trained by the then colonial masters during the colonial era of 19th century. (NEHOA, 2001)

3.1.2 The colonial masters executed the sanitary duties of our environment in Nigeria and were known as sanitary Inspectors while the Africans/Nigerians attached to them, as their assistants were known as sanitary attendants. These attendants acted as aides to their masters during which time they under-studied them. They were used by the masters to discharge various sanitary inspection activities like marking of tall trees, that were close to residential buildings, identification and elimination of vector borne diseases, service of abatement notices, identification of infectious disease cases, disinfections and disinfestations, liaison between the colonial masters and communities, verification of notices issued by Sanitary Inspectors, retention of daily, weekly and monthly returns etc. under their masters directives and close supervision.

3.1.3 The colonial masters however introduced public health, particularly of the environmental sanitation and immunization as a coercive system using Sanitary Inspectors whom the people dreaded. The people were not made to realize that these sanitary measures were in their own self-interest. The Sanitary Inspection system achieved effective disposal of refuse, water hygiene, food hygiene and some measure of immunization against diseases like small pox and yellow fever.

3.1.4 The first problem that faced the modern day Nigerian Sanitary Inspectors as early as the 1920s was the bubonic plaque out-break of in 1924. They were actively involved in the control of the plague epidemic. They were also involved in other activities and most especially the Ships inspection, a vital instrument for the control of communicable diseases. One of the well-known achievements recorded was the eradication of such diseases as small pox and yaws. (NEHOA 2001).

3.1.5 Furthermore, the typical rural Nigerian community in the past kept the environments around their houses clean. This is done by daily early morning sweeping, particularly by the women. In view of overwhelming literacy and poor health education, many other health-related activities and issues in the environment were poorly handled. They swept refuse and garbage were disposed of in nearby bushes. The causal association between the various environmental factors, vectors, microbial world, diseases cycles and means of transmission could not be understood by the people.
3.1.6 Regrettably, with the oil boom and increase in urbanisation, sanitation situation of our various urban centres started to deteriorate. The urban dweller abandoned his personal responsibilities and surrendered them to the government. He obtained water from the municipal water system or a dug well and disposed of his faecal waste either through a dug pit latrine, or Ventilated Improved Pit latrine system and occasional Water Carriage (W.C) system. His refuse and garbage including the cleaning of drains became the responsibility of Councils. The large size of the population and distance from safe disposal sites made it impossible to have an effective city management structure. The city worker left home early and returned late and thus had little time to look after his environment. With the growing size of urban population and dwindling economic resources, the city management system gradually became incapable of matching available resources with needs. To complicate issues, the absence of the Sanitary Inspectors and their coercive measures, the city steadily started to suffer from environmental decay, (Ashley-Dejo 1995).

3.1.7 Furthermore, the military regimented, environmental sanitation programme of 1983 to 1998 with varying degrees of success. Task forces, Sanitation Corps complemented with various edicts and military tribunals to try sanitary offenders were put in place. It was during this period that the monthly environmental sanitation exercise was introduced. The effects of environmental sanitation exercise were very conspicuous within the era of 1984 to 1985. This however brought about some successes, but could not be sustained. The edicts covered most components of environmental sanitation but Environmental Health Officers (EHOs) were compromised in the enforcement rather various Task Forces and Sanitation Corps, were used at various times for enforcement and arrests of offenders as well as to implement the provisions of the edicts. However this also marked the gradual taken over of EHOs duties by non professional.


The Federal government established the Federal Ministry of Environment with the overall mandate of ensuring a healthy environment for her citizenry. Environmental sanitation, being a part of the Ministry’s mandate has been receiving attention till date. In order to sustain the programme, sanitation experts drawn from other Ministries were transferred to the new ministry. Currently, the environmental sanitation situation in the country is as follows:

4.1 Waste Management: In Nigeria, with urbanisation, waste products increase in volume and in composition, and its impact upon man’s environment and health has intensified. The unplanned urban development results into accumulation of wastes and other unsanitary conditions. The waste products often contain materials that are toxic and not readily degradable. Such materials include various types of chemical wastes produced by industries and these can contaminate soil and ground water sources indefinitely if not properly disposed of.
Hazardous wastes, including medical and infectious wastes pose potential hazard to human and environment when improperly disposed of. The improper handling and disposal of these wastes are major threats to refuse collectors and scavengers resulting in infections such as HIV/AIDS, tetanus etc.
In Nigeria, recycling of wastes is negligible, while collection, transportation, compaction and final disposal are very unsatisfactory. Technology is daily contributing to the change in composition of municipal wastes. The use refuse house, mammoth bins are no longer available therefore contributing to wastes from households, markets, institutions, and offices being dumped on streets where they cause environmental degradation through blocked public drains as well as unsightly and malodorous mountains of refuse. The community should be sensitized on the use and importance of the 3Rs (Reduce, Reuse and Recycle).

Health hazards associated with poor solid waste management:

• Provides breeding sites for flies, mosquitoes, cockroaches, rodents and other vermin of public health importance as well as vectors of disease with consequent high prevalence and spread of malaria, diarrhoea, cholera, typhoid, yellow fever.
• Leacheats from dumpsites contaminate surface water and under ground water sources; and may render streams, shallow wells and rivers unfit for domestic use (drinking, cooking and washing) recreation or fishing.
• Alteration of the physical, chemical and microbiological properties of soil with negative effects such as death of microfauna, loss of vegetation susceptibility to erosion.
• Air pollution by methane and related hydrocarbons emitted during biodegradation as well as toxic gases (carbon monoxide, oxides or nitrogen, sulphur dioxide, polynuclear aromatic hydrocarbons etc.) and particulate (ash, toxic heavy metals etc.), which are produced during uncontrolled incineration. The health effects include chronic respiratory infections, bronchitis and exacerbation of asthmatic attacks.
• Fire hazards and spontaneous combustion.

Available record showed that 41.53% of the populace dispose their refuse within their premises, 37.8% dispose into the bush and only 13% use sanitary dustbin. In all, 79.4% of Nigerians used one method or the other adjudged as insanitary, (NDHS 2003). The alarming rate at which heaps of solid wastes are occupying our cities, coupled with the fact that 79.4% of Nigerians used method adjudged as insanitary has not only constituted visual blight and odour nuisance but also encourages the breeding of rodents and mosquitoes and other pests of public health importance, with attendant disease outbreaks.

Box 1
Government 4.88
Private collection 7.68
Government bin 1.98
Disposal within compound 41.5
Unathorised heap 40.46
Others 3.45
Total 100
Source: FOS (Bureau of Statistics): Nigeria Poverty Profile 2004

Box 1 depicts refuse disposal system in the country.

The above picture calls for promotion of public /private partnership for effective wastes management in the country. This will require adequate capital investment in plants; vehicles; essential equipments; acquisition of enough and suitable land; employment and deployment of adequate technical, administrative and other supporting staff; adequate recurrent budget. With these, appropriate technology will be chosen for the proper disposal of solid and liquid wastes including hazardous or special wastes.

4.2 Poor Excreta and Sewage Management

Human excreta are important sources of pathogenic organisms especially the causative agents of cholera and other diarrhoea diseases, as well as helminths infections such as ascariasis, hookworm, teaniasis. The high endermicity of these diseases in Nigeria is related to the poor excreta and sewage management. Studies have shown that Nigeria households without a toilet, gastroenteritis was about three times higher than in households where toilets was properly used. It is also common sight to find raw sewage being piped into the public drains. Studies have equally shown that lack of adequate, functional and sanitary facilities in school diminishes the motivation of children for school attendance, with a potential depressive effective of school enrolment and attendance especially for girls. In addition, recurrent sanitation related illness leads to school absenteeism, which in turn affects learning, and developmental achievements of affected school children.

4.3 Food Hygiene and Safety
The level food hygiene in our society leaves much to be desired. These practices in Nigeria are generally known as not being of a high standard, and this, to a large extent, plays a significant role in the aetiology of food borne diseases prevalent in the country. Surveillance data from the Federal Ministry of Health shows increasing trend in the number of cases of food-borne diseases such as cholera, food poisoning and typhoid/paratyphoid fevers. For example, while in 1994, 3,173 and 22,525 cases of cholera and typhoid/paratyphoid fevers respectively were reported, these figures increased to 9,254 and 68,846 cases, respectively by 1998. Surveillance data for 2001 showed that these figures had further increased to 10,294 and 73,949 cases respectively.

Moreover, findings from a survey conducted by the Federal Ministry of Environment in 2005 indicated that food-borne illnesses due to contamination by micro-organisms such as Vibrio cholerae, Salmonella and Shigella species, etc, were still responsible for significant ill-health among all age groups in the country. The report of the survey also showed that most of the reported illnesses resulted from basic sanitation failures that occurred during food production, processing, retailing and handling. The report also highlighted that achieving sound food sanitation was hampered by lack of basic sanitation infrastructure in many areas of the country.

Food-borne diseases are a leading cause of illness, death, food insecurity and poverty in Africa. Some 700,000 deaths occur annually on the continent as a result of food and water-borne diseases according to WHO estimates, many more are likely to go unreported. Food-borne diseases have a negative impact on public health and food security, exacerbating the effects of diseases like HIV/AIDS and malaria, and reducing the overall availability of food. Concerns related to food safety and quality reduce consumer confidence in the domestic food supply and cause millions of dollars in lost export earnings, limiting opportunities to stimulate economic development through trade in food and agricultural products. Food control systems in many African countries including Nigeria are unable to ensure a supply of safe food for domestic consumers and comply with sanitary and phytosanitary requirements for food and agricultural exports.

This lack of capacity negatively impacts on food security, public health, and economic development. Delegates at the FAO/WHO Regional Conference on Food Safety for Africa in Harare, Zimbabwe in October 2005, acknowledged the seriousness of this situation and unanimously adopted a resolution recommending a Five-year Strategic Plan for Food Safety in Africa for adoption by FAO, WHO and the African Union (OAU). This Plan puts forward concrete actions to improve the safety of food produced and consumed in the region based on a food chain approach and the involvement of all the relevant stakeholders from farm to table. It seeks to provide African solutions to the challenges inherent in improving food safety while recognizing the issues and trends at the international level that affect national food control systems. This proposal has now been developed by FAO and with Members of the Bureau of the Regional Food Safety Conference, to support the implementation of this Strategic Plan for Food Safety in Africa.

Some common food hazards
Food hazards refer to the presence of biological, chemical or physical agents in food or the condition of food with the potential to cause an adverse health effect. Common food contaminants include:
i. biological agents: bacteria, viruses, parasites, yeast, mould, etc
ii. chemical agents: pesticides residues, agro-chemical residues, traces of cleaning chemicals, etc
iii. physical agents: sand, wood, metal nails, hair, food debris, radiation, etc
In developing countries including Nigeria, biological organisms, especially bacteria constitute most of the food hazards, which give rise to food-borne illnesses, food poisoning and spoilage.
Food-borne illnesses
Food hazards usually give rise to food-borne illnesses, food-poisoning and food spoilage. There are two types of food borne illnesses:
i. Food poisoning
ii. Food-borne diseases
Food poisoning
Food poisoning refers to sudden illness that develops soon after ingestion of food or drink contaminated with living bacteria, their toxins (chemical substances), or other inorganic chemical substances. Symptoms and signs of food poisoning usually develop, within 72 hours, after the contaminated food or drink is consumed and the ill person frequently experiences abdominal pain, diarrhoea, vomiting, or nausea. Food poisoning also tends to affect many persons at the same time and majority of those affected would have consumed the same food or drink and will manifest similar symptoms and signs.

Bacterial food poisoning
Food poisoning due to bacteria is the most common and poisoning frequently occurs as a result of the toxins that the bacteria produce as they multiply in the food. Bacteria that cause food poisoning include Salmonella, Staphylococcus and Clostridium species. Storage of cooked food contaminated by bacteria between 4 ˚C and 60 ˚C (temperature danger zone) encourage the growth of these bacteria and hence the likelihood of food poisoning.

Salmonella food poisoning
This is the most common form of bacterial food poisoning and the species of Salmonella commonly incriminated as causing food poisoning in man include: S. typhimurium, S. cholera-suis and S. enteritidis, etc. Many of the Salmonella species causing food poisoning are primarily agents that affect animals (zoonoses) but man gets infected from farm animals and poultry through contaminated meat, milk, milk products, etc. Rats and mice are also important in the transmission of these bacterial agents as they are frequently heavily infected and may contaminate food and foodstuffs through their urine or faeces.
Poisoning occurs when the organisms multiply in the intestine causing local inflammation (enteritis and colitis). The incubation period is usually from 12 to 24 hours and symptoms include chills, fever, nausea, vomiting and a profuse watery diarrhoea lasting 2 to 3 days. Control of salmonella food poisoning relies heavily on meat inspection before and after slaughter, proper storage of meat and meat products, proper handling of food to prevent cross-contamination between cooked and raw food, adequate cooking of food and control of pests and rats.
Staphylococcal food poisoning

Almost as common as salmonella food poisoning, staphylococcal food poisoning is caused by enterotoxins produced by some strains of coagulase-positive Staphylococcus aureus. The organism is widely distributed in man and animals and is commonly found on the skin, in the nose and throat. It is usually responsible for most boils and abscesses in man and animals. Cows suffering from inflammation of the breasts have been known to cause outbreaks involving milk and milk products. Poisoning occurs as a result of “preformed” toxins that accumulate in the food as the organism multiplies; being heat resistant, the toxins persist in food even after the organisms have been killed by heat.
Incubation period for staphylococcal food poisoning is usually from 1 to 6 hours and the illness becomes manifest by sudden onset of vomiting, abdominal cramps and diarrhoea. In severe cases, there may be blood and mucus in the stool. The most frequently incriminated food is salad and contamination is through improper handling and storage at temperatures that encourage the growth of bacteria before the food is consumed. Optimal temperature for growth of Staphylococcus is between 35 ˚C and 37 ˚C. The main steps in the control of staphylococcal food poisoning rest on proper food handling and storage and the exclusion of persons suffering from obvious staphylococcal infections such as boils, skin lesions and abscesses from handling food.

Clostridial food poisoning

Many species of Clostridium cause food poisoning. The most serious but fortunately rare is food poisoning due to Clostridium botulinum called botulism. The organism itself is widely distributed in soil, dust and the intestinal tract of animals and usually enters food as spores. Multiplication of the organism under favourable anaerobic conditions results in formation of powerful neurotoxins that act on the parasympathetic nervous system. Unlike other forms of food poisoning, botulism rarely manifests with symptoms of gastro-intestinal tract but rather the patient presents with signs related to disturbance of the parasympathetic nervous system such as dysphagia (inability to swallow), diplopia (double vision), ptosis drooping of the upper eye-lid), dysarthria (difficulty in speech articulation), blurring of vision, muscle weakness and quadriplegia (paralysis of the limbs). Death occurs in 6 - 7 out of 10 cases usually within 4 –8 days from onset of symptoms. Most frequently incriminated food include home preserved food such as home-canned vegetables, smoked or pickled fish, home-made cheese or similar low acid foods. The toxin is fortunately thermolabile, hence it is destroyed by heating of the food to 100 oC for a few minutes. Other causes of clostridial food poisoning include Cl. welchii and Cl. perfringens.

Chemical food poisoning

Although rare, chemical food poisoning does occur and there have been unsubstantiated reports of chemical food poisoning in Nigeria “killer bean episode” or sudden deaths of entire families after consumption of a meal of “eba” made from improperly processed cassava and believed to be due to the cyanide content. Recently, sudden deaths of a family of six after consumption of “eba” in Abuja was reported by NAFDAC to have been contaminated by chemical rat poison “ota- piapia”. Chemical food poisoning may occur when food is improperly processed to remove naturally occurring poison as is the case with some varieties of cassava; or from fertiliser or pesticide residues, as was suspected in the case of the “killer bean episode”. There have also been reported cases of mushroom poisoning. Chemicals such as lead, aluminium, arsenic, cadmium, mercury etc, may get into food from the water that is used in food preparation, or from cooking utensils. Cross contamination may occur when food is kept close to chemical substances such as fertilisers, pesticides, herbicides, or cleaning agents. Food poisoning may also result from the consumption of food with unacceptably high levels of chemicals such as lead, aluminium, pesticides and veterinary drug residues.

Food-borne diseases
Food-borne diseases are caused by micro-organisms, including bacteria and viruses, when they gain access into the body through the ingestion of contaminated food. Food-borne diseases occur when such micro-organisms multiply within the body of a susceptible person. These micro-organisms may not necessarily multiply in the food to cause the diseases for example; salmonella thyphii will not multiply in ice cream contaminated by the organism due to lowered temperature but may cause typhoid fever when the ice-cream is consumed. Other media, such as water, contaminated hands and fomites, etc, may also serve to spread food-borne diseases. Some well-known examples of food-borne diseases include acute diarrhoea (especially among children under 5 years), cholera, typhoid, dysentery, etc.

Acute diarrhoea
Diarrhoea is defined as the passage of 3 or more loose stools within 24 hours. Diarrhoea accounts for 1 out of every 5 deaths in children below the age of five years in Nigeria. A wide range of organisms has been found to be associated with diarrhoea, but the most frequently incriminated are viruses such as rotaviruses, adenoviruses, coronaviruses and bacteria including Campylobacter jejuni, Escherichia coli, Shigella species, Salmonella species, etc. Diarrhoea among the under-fives usually occurs after 6 months of age when the child has started complementary feeding. The unhygienic handling of the child’s food is an important risk factor.


Cholera is a disease of rapid onset characterised by vomiting, profuse dehydrating diarrhoea, toxaemia and muscular cramps. Suppression of urine and shock may occur later. Cholera is caused by Vibro cholerae, 01 and 0139 (Classical or El Tor biotypes). Each of these biotypes has three serotypes: inaba, ogawa and hikojima. The incubation period ranges from 1 to 7 days (more frequently 3-4 days). The reservoir of infection is man and transmission is from a sick person, convalescent patient or a carrier. Transmission is usually through contaminated water or food, particularly seafood and contaminated inanimate objects. Poor environmental and food sanitation and overcrowding are important risk factors for cholera transmission.


Typhoid is a systemic infection caused by Salmonella typhi. Typhoid is exclusively a disease of man and transmission is from a sick person or carrier to other persons through consumption of contaminated water, ice-cream, milk, etc. Carriers are of particular importance in typhoid transmission and it is of utmost importance that food handlers are screened to ensure they are not infected with the organism.

Food spoilage

Food may be considered spoilt when its natural state changes to a point that it becomes undesirable to eat. Food crops start to deteriorate after harvesting, and animals after they are slaughtered. The rate of deterioration varies from food to food and also depends on handling. It is important to note that, not all changes that occur in food after harvesting or slaughtering are undesirable. However, most of the changes impair the acceptability of the food and may be dangerous to health. Apart from being a potential health hazard, food spoilage also results in economic losses for the food business, thus worsening poverty. All efforts must therefore be made to prevent spoilage. In addition, it is illegal and unethical to sell spoilt food.

Control of food hazards
Food sanitation cannot be left to chance. Guidelines for personal hygiene, cleaning, disinfection, pest control, etc, must be established to promote sound food sanitation. In this regard, suitable guidelines and control measures shall therefore be put in place to protect the safety of food. Control measures vary from those that do not change frequently, e.g. the design of equipment and structure of premises, to practices that require frequent monitoring such as personal hygiene and pest control. The module deals with specific areas designed to contribute to sound food sanitation in the food handling chain.

4.4 Housing Sanitation
Available record showed that 41.53% of the populace dispose their refuse within their premises, 37.8% dispose into the bush and only 13% use sanitary dustbin. In all, 79.4% of Nigerians used one method or the other adjudged as insanitary. The alarming rate at which heaps of solid wastes are occupying our cities, coupled with the fact that 79.4% of Nigerians used method adjudged as insanitary has not only constituted visual blight and odour nuisance but also encourages the breeding of rodents and mosquitoes and other pests of public health importance, with attendant disease outbreaks.
It is a common sight for one to find houses without latrines in both villages and urban centres including Abuja. Public places such as motor parks, bus stations, markets etc. without these conveniences.

The relevance to health of the immediate human environment – house, has long been appreciated and health professionals have before now, given guidelines on the ideal characteristics of that most important of environments, the house. Poverty and over-crowding are two variables used in analysing disease and its prevention and both are specifically related to housing. Housing influences health. Studies have equally shown that various building materials such as wood, particleboard and pressed wood products, currently being used in the housing industry which may contain volatile organic compounds like formaldehyde or other wood preservatives cause respiratory and dermal irritant, Children Environmental Health). Good housing is to provide basic quality of life requirements, which include ventilation, lighting, warmth, privacy, sanitary conveniences as well as adequate space index per occupant. Unmet housing needs affect the health of about 60% urban resident in Nigeria. This situation increase susceptibility to cerebrospinal meningitis, tuberculosis and other diseases related to such conditions. Residents of low-income periurban settlements are also at higher risks of suffering from drug abuse, violence and accidents, as well as the mental strain of over crowding, noise and lack of privacy which leads to increased psychological and social stress. Direct health threats come from exposure to disease pathogens and pollutants.

4.5 Pest/ Vector Management

There is no doubt whatsoever that, cockroaches, flies, termites, mice, rats and other pests post health risks and property damage risks to schools structures. Therefore, in the interest of maintaining a healthy and well-functioning school, use of pesticides chemical is employed against such threats. It is a well known fact that rodent play an important role in transmission of diseases. They excrete organism such as salmonellae. Their droppings, urine, gnaw as well as hair can contaminate food.

Improper use of pesticides can put children and the environment in danger. Pesticide poisoning may be a consequence of improper pesticide use. Pesticides are poison not only to pest but also the school children. Therefore, they can pose health risks for both children and staff at school. Children are however the biggest concern because their developing bodies are less able to tolerate high pesticides exposures. Also, pesticides are often used in areas of the school where exposure risks are heightened. Pesticides used in the hostels, dining hall / cafeteria could end up on the food the children eat. Pesticides on the grass and plants in outdoors and around school can unnecessary expose school children to toxins.
It is mandatory on school authority to provide information as regards the potential effects of the chemical pesticides to be used, post signs or warn students before and after application of pesticides.

It is therefore imperative to introduce in the schools the use of Integrated Pest Management (IPM). Integrated Pest Management involves the use of various control measures to reduce pest populations. This includes managing the pest problem with a variety of physical, biological, and cultural practices, and if necessary, by use of a pesticide. By using one or more of these measures, control can be achieved with minimal impact on human safety and the environment.
There are a variety of control measures that can help reduce pest populations while protecting human health and the environment. For example good house keeping is one of the most important factor preventing and controlling cockroaches’ population. Cockroaches cannot live without food, water and shelter. The cockroaches can also be controlled with the combination of use of trap, chemical and good sanitary practices. Take steps to prevent the pest population from increasing to a level where control is necessary. Some general control methods include using barriers and traps, removing attractive conditions for the pest, changing the environmental conditions (temperature, humidity) and attracting natural predators. These and other alternative controls are all fairly simple to do and will reduce pest populations. This will help to reduce heavy reliance on pesticides.
Pollution arising from use of pesticides to control pests and maximize the yield of farm product farmers introduces or lavishly sprays the plants with various pesticides. Improper use of pesticides can put the environment and human in danger. Evidence has shown that the use of chlorinated hydrocarbon based chemicals such as diazinon, nuvan are effective in controlling pests of public health importance thereafter residues from the spraying find their way into the sources of drinking water and render it unfit for consumption. Also pesticides used in areas of the school where exposure risks are heightened. Pesticides used in hostels, dinning hall/ cafeteria could end up on the food the children eat.
4.6 Poor Drainage System

Poor surface water drainage in urban area leads to stagnant pools where mosquitoes and other disease carrying vectors breed. The prevalence of diseases such as malaria in many towns and cities is partly resulting from poor drainage maintenance system. Most of the drains especially in Lagos areas, shops and stalls are built over public drains and this often become substitutes for toilets, waste disposal facilities, lack of maintenance. All these are threat to environment and health; the major threats arising from the above scenario include flooding, erosion, and landslides destroying homes built on marginal land.

4.7 Markets and abattoirs

Markets and abattoirs are built without proper layouts, and where such layouts exist, they have been distorted. Besides, provision of adequate water supply, proper drainage, and adequate waste disposal sites are inadequate. The proliferation and licensing of abattoirs should be controlled in various States and Local Governments Areas to ensure sound food sanitation. Transportation of meat from the abattoirs in passenger vehicles or motorcycles is a common practice in most towns and cities. Contamination can occur during transportation especially while using vehicles not designated for this purpose. . It is also a common practice to see meat hawked on the streets, in traffic etc. This practice exposes meat in the environment to contaminants such as dust, flies and other pathogens

4.8 School Sanitation

The sanitation standards in most of our schools are very poor. Toilets when available are not functional due to lack of water to flush the toilets and this leads to defecation at corners and nearby bushes by pupils. In other instances where toilets are provided pupils vandalize them. In the schools, general environmental sanitation is poor. Overcrowding is a major threat to the children’s health in most of our schools. Most of the infectious diseases occurring in the schools are closely linked with overcrowding and dirty environment. These factors have a serious health impacts with attendant social and economic consequences including school absenteeism.



• Produce and circulate Policy and Guidelines;
• Advocacy through a formal launch of the policy documents;
• Implement Approval Policy and Guidelines;
• Print and distribute relevant forms;
• Produce IEC materials for community education and awareness;
• Mobilise and empower all Stakeholders for effective Policy takeoff.


• Implement the provisions of the Policy on institutional arrangements;
• Encourage adherence to the provisions of the Policy Guidelines on programme coordination and inter-agency cooperation;
• Establish Technical Committees on Environmental Sanitation at all tiers of Government in programme implementation;
• Develop Procedural Guidelines on Environmental Sanitation Service Delivery;
• Establish a Data Bank on Environmental Sanitation;
• Review and harmonise existing Environmental Sanitation Legislation, State laws, Bye-laws, etc.;
• Enact relevant legislation at all tiers of Government to give legal backing to Policy implementation;
• Establish appropriate legal institutions and mechanisms, including Mobile Courts, for enforcement of Environmental Sanitation laws.


• Embark on recruitment, training and retraining of Environmental Health Officers (EHOs);
• Enforce the provisions of the Policy Guidelines on the employment of Environmental Health Practitioners for Professional Environmental Sanitation Services, by the private sector;
• Organize public and private sector collaborative research, technical training seminars and exchange programmes on Environmental Sanitation;
• Seek technical support and assistance from bilateral and multilateral Agencies for Environmental Sanitation.


• Promote partnership amongst Stakeholders through dialogue and organisation of periodic Stakeholders’ Forum;
• Involve the private sector progressively in Environmental Sanitation service delivery through creation of enabling environment and incentives;
• Set criteria for private sector participation at all tiers of Government;
• Provide technical assistance packages to promote Stakeholders’ participation;
• Develop and implement the provisions of the Policy Guidelines on equipment and material supplies and maintenance.


• Advocacy through sensitisation and mobilization of all Stakeholders at all tiers of Government;
• Declare annual National Environmental Sanitation Day;
• Review school curricula on hygiene education to include Environmental Sanitation;
• Introduce and enforce the use of environment friendly packaging material;
• Encourage establishment of neighbourhood Environmental Sanitation Committee;
• Develop appropriate Information, Education and Communication (IEC) packages for target groups;
• Institutionalise sound Environmental Sanitation consciousness as a life style;
• Strict enforcement of Environmental Sanitation laws and penalise defaulters so as to deter other citizens;
• Create enabling environment to facilitate behavioural change.


• Comply with Policy Guidelines on Sanitary Inspection of Premises;
• Control reared and stray animal;
• Comply with Policy Guidelines on Excreta and Sewage Management;
• Ensure the free flow and adequacy of the drainage system;
• Comply with Policy Guidelines on Solid Waste Management;
• Ensure sanitary disposal of the dead;
• Comply with Policy Guidelines on Pest and Vector Control;
• Comply with Policy Guidelines on Market and Abattoir Sanitation;
• Comply with Policy Guidelines on Food Sanitation;
• Comply with Policy Guidelines on School Sanitation;
• Review and evaluate performance of set criteria.


• Advocate for increased budgetary allocation in favour of Environmental Sanitation at all tiers of Government;
• Compile a compendium of potential sources of funding and seek assistance for programme implementation;
• Organise Donors’ Forum to provide opportunities for ESAs and Philanthropists to support programme implementation;


• Assess performance based on set indicators and criteria for each activity and task;
• Set standards for delivery of Environmental Sanitation services based on local conditions, customs and practices;
• Set standards for equipment and material procurement and maintenance in Environmental Sanitation;
• Evolve criteria for programme performance and evalution;
• Collate, analyse and review M&E reports;
• Institute annual summit on Environmental Sanitation.


5.1 The current Public Health Laws stem from enactments as far back as 1862 and beyond. They were originally modeled on the nineteenth century concepts and ideas on public health, modified and adapted to suit the colonial style of Government, living and circumstances. In many ways, Public Health Laws no longer conform to the current perception and challenges in view of vast developments in practically all fronts of relevant knowledge and technology. The public health field is no longer the exclusive domain of the medical doctor and his sanitary inspector of nuisances. Many scientific and arts discipline have major and vital roles to play.

5.2 Since these laws were not revised, there had evolved considerable legal instruments from the Military, Civilians, and Constitutional and Administrative changes. Along with this, the economic development and population growths had been phenomenal. There exist no considerable plans for the immediate and long term environmental problems. Even where attempts were made to ascertain the impacts on these effects on the environment, the authorities had little or no statutory instruments and capabilities to implement the corrective measures.

5.3 In the light of the present trend on scientific and technological advancements affecting public health and environment, there is the need to develop the capacity of Environmental Health Officers to effectively cope with the current challenges in enforcement and monitoring.
The urban drift has put considerable strain on public health services and facilities in the urban areas. Efforts to increase these amenities have not kept pace with the demand hence the various undesirable chaotic developments and lack of essential needs noticed in all our urban centres.

5.4 Most of the 36 States and the substantial numbers of the Local Government Areas/Councils still operate laws of the former northern, western and eastern Nigeria despite their autonomy. It is expedient therefore to have a unified Environmental Health Laws with modified fines to reflect economic peculiarities of each State and LGA.
The National Environmental Sanitation Policy enhances the effectiveness of the Public Health Laws. In Chapter 2 Strategy 2: Development of Administrative and Legal framework of the National Environmental Sanitation Action Plan deals with the objectives of this strategy which are to ensure compliance with the provisions of the National Environmental Sanitation Policy on institutional arrangements and develop the legal instruments on Environmental Sanitation. Specific tasks to be carried out include:

i. Establishment of Technical Committees at National, State and LGA levels;
ii. Creation of Departments of Environment at the LGA level for effective management;
iii. Evaluation and harmonization of existing Legislation on Environmental Sanitation with a view to ensuring their adequacy and effective enforcement;
iv. Definition of jurisdictional boundaries for enacting appropriate and specific Legislation on Environmental Sanitation.
v. Establishment of appropriate Legal institutions and mechanisms, including mobile courts for effective enforcement and sanctions of Environmental Sanitation Legislation.

The Laws Reviewed: The laws which deal with public health in one way or the other that come under review are:-

i) The laws of the Federation of Nigeria & Lagos 1958 & 1959
ii) The laws of Northern Nigeria 1963
iii) The laws of Eastern Nigeria 1963
iv) The laws of the Western Nigeria 1959
v) The various Lagos State Public Health laws 1999 &2000
vi) Environmental Pollution Control Laws (Lagos State) 1989
vii) State edicts of various States


6.1 Section 3 of Chapter 165 defines what us a “Premises”. This definition covers all human habitations from static, mobile and movable.

Section 7 of Chapter 165 defines a “nuisance” and includes every imaginable act by omission which may injure or endanger health in any way. Section 8 through to 12 details the legal procedures for the abatement of a nuisance.

6.2 From long term experience, it has been found out that the procedure for the abatement of a nuisance is too long and cumbersome. In practice, many enforcing officers are reluctant to initiate abatement actions. It is therefore recommended that the procedure should be swift and effective with due regard, of course, to both parties’ interests – namely, the author and the sufferer.

6.3 Sections 17and 18 enumerate the obligation of the Police to furnish every assistance to the health officer in effecting the evacuation of any infected area and in the necessary measures pertaining thereto. Sections 17 and 18 should remain and all States should have them reinstated into their respective Public Health Laws.

6.4 Part II Section 30 through to 35 details the registration, licensing as well as the obligation of the operators to ensure the cleanliness and removal of the al such blood, offal filth, rubbish in the slaughter house.

6.5 Sections 40 and 42 empower various authorities to make rules and regulations pertaining to general sanitation amongst other things. Comprehensive rules have been made under section 40, 41 and 42 and on the whole they are good and should be retained and updated as regards penalties to take account of the current monetary value.

6.6 Sections 45 – 49 deal succinctly with the issue of refuse (solid waste) and the obligation of individual to provide sanitary dustbin as well as to ensure the disposal of same.

6.7 Rule 54 empowers Medical Officer of Health to inspect factories, work-places, and other buildings used for public amenities to ascertain that essentials like drainages are effective and adequate and other basic health requirements.

6.8 Section 55 through to 65 of Cap 165 deal succinctly with issues of Food Premises inspection, registration, licensing, and revocation of license including closing order. The obligation of operators of such premises to ensure sound food sanitation practices.

6.9 The Lagos Public Health (Meat) By – Laws made under section 41 of the Public Notice 155 of 1942 which the establishment of butchers shop and sale of meat, cleanliness of slaughterhouse including meat shops, handling of meat, transportation of meat as well as inspection of all vehicles use in the transportation of meat should be reviewed and incorporated in the proposed Environmental Health Laws.

7.0 Every Local Government Council should enact a bye law on the establishment of Public Conveniences to ensure standards as regards to siting, construction, landscaping, sanitation etc.

7.1 Factories and Places of Work: The present Factories Act Chapter 66 needs to be thoroughly overhauled and given a much wider scope. The new act should protect the health and welfare of workers in each and every work place. The Ministry of Health must naturally play a very important part in the drafting of this law and bring up to date the requirements in the standards of occupational health and safety. The Ministry must equally take a major responsibility in the enforcement of this new law as regards the monitoring of health hazards both on individuals and the entire work places precincts. Conflicts and duplications between the enforcing agencies should be avoided. In the light of rapid industrial development the enactment of this law is of a very high priority.

7.2 Sections 17 and 18 of Cap.165 deal effectively with those aspects of environmental sanitation which include wastes disposal. The then Military Administrator of Lagos State made an Edict in 1978 which dealt with the subject of environmental sanitation covered in the sections mentioned above. This Edict is still in the statute book to date in addition to the sections mentioned above.
Subsidiary legislation made under section 42(c) (i) – (iv) of Chapter 165 (Public Health Laws – Federal and Lagos) dealing with wastes disposal. The rules are fairly comprehensive for day to day application.


Pollution can be described as “man-made or man-aided alteration of chemical, physical or biological quality of the environment.” The above is the Scientists’ approach to defining the word. Thus according to this definition, there is pollution once there is introduced into the environment of any substance or thing which results in a change or alteration of the physical, chemical or biological composition of the particular environment. For example, our entering into this hall has resulted in the change of the air content by the breathing of more carbon dioxide and taking in of oxygen. Also an old tree that decayed and got decomposed into the land has definitely polluted the land; so also is the dumping of domestic or human waste into the lagoon or stream would amount to polluting the lagoon or stream.

8.1 In dealing with this aspect I will content myself with a few examples. In 1970, two scientists conducted a research into 9 existing wells in Shomolu area of Lagos. They reported that water from these wells contain average iron content of 1.09 ppm whereas the permissible safe limit is 0.3 ppm. Hence we have in many of our houses brown stain upon sinks, baths, laundry and cutlery.

Also in excess of the safety limit is the nitrate concentration (about 8,000 times). The study revealed the coliform content to be about 18 whereas treated water ought not to contain 3 coliform per 100 millitres; the presence of these substances we are told, have deleterious effects on human beings especially children. Another study conducted in the Surulere area revealed that about 4% of reported cases of disorders were due to poor sanitation and that of this figure about 52.8% involved children under 15%. Even potable or pipe borne water is no exception. It has been reported that samples of water supply to Ile-Ife taken at various locations contained on the average of 5.0 – 9.0 coliforms bacteria per 100 militres and that on a particular day a staggering figure of 79.0 coliforms was reported.

On March 10, 1977 the Daily Times reported that 4 people died as a result of their inhaling fertilizers fumes, and only last Sunday June, 10 1984 the Sunday New Nigeria reported at its back page that the country’s only super-phosphate factory has been causing a lot of pollution in the Makera village of Kaduna State. On February 27, 1984 the Concord Newspaper reported the discovery of ‘crude oil’ in water well in the Oshodi area of Lagos Metropolis which was later said to have been a result of some seepage of petroleum oil from nearby petrol station and/or mechanic workshop. On March 31, 1977 the Daily Times reported that a group of children playfully set fire on a heap of refuse in the premises of Leventis Stores in Kaduna and aided by breeze, the fire destroyed within minutes, goods worth thousands of naira. And on April 17, 1984, the Concord as well as many other newspapers reported that a family of five died as a result of inhaling fumes that emanated from a nearby generator; I think we all remember the fire that gutted the Lagos State ferries at the Festac Village end of the Lagos-Badagry Road ferry route. That fire was caused as a result of spilled oil on the lagoon. The Concord of 11/6/84 carried the report that the persistent noise created by a steel discs manufacturer in a strictly residential part of Ikeja had forced residents to look for solace elsewhere far away from their homes in order to keep away from incessant and irritating noise emanating from welding operations at the firm. The list is endless. The occurrences I have listed here are not isolated but common place occurrences till today unabated.

I have gone at length to give these examples just to refresh our thoughts about the problems facing this country in the area of environmental pollution.

8.2 The Guidelines and Standards for Environmental Pollution Control in Nigeria as published by the Federal Environmental Protection Agency (FEPA) now the Federal Ministry of Environment are still very much relevant and enforceable.
However, there still exist the following regulations:
• S.I.8 National Environmental Protection (Effluent Limitation) Regulations 1991
• S.I.9 National Environmental Protection (Pollution Abatement in Industries and Facilities generating wastes) regulations 991
• S.I. 15 National Environmental Protection Management of Solid and hazardous Wastes Regulations 1991.
These regulations deal effectively with effluent discharges, limitations, spills, generations and transportation of solid waste including hazardous and medical wastes.

8.3 AIR POLLUTION: Air pollution is the presence in the atmosphere or substance which are not normally (naturally) present in the air or the presence of substances which normal present in air but of concentration in excess of the normal or acceptable concentrations of such substances.
This is illustrated in the box 2 below.

S/N Pollutants Time of Average Limit
1. Particulates Daily average of daily values1 hour 250 ug/m3

2 Sulphur oxides
(Sulphur dioxide) Daily average of hourly values1 hour 0.01ppm (26ug/ m3)

0.1ppm(26ug/ m3)
3. Non Methane
Hydrocarbon Daily average of 3 hourly values 160ug/ m3
4. Carbon monoxide Daily average of hourly values

8hourly average 10ppm(11.4ug/ m3)

20ppm (22.8ug/ m3)
5. Nitrogen oxides
(Nitrogen dioxide) Daly average of hourly values hourly (range) 0.04ppm-0.6 pp,
(75.0ug/ m3) -113ug/ m3)
6. Photochemical oxidant Hourly values 0.06ppm

Quality parameter Significance General Method of Analysis; Expression of Results
S/N Type
Aerosol Gases Vapour
1 Combustion process Dust, fume SO2 Organics, acids
2 Automotive engines Fume, smoke SO2, NO2, Co, ACIDS
3 Chemical process Dust, mist, fume, spray CO2, SO2, NH3
H2S Odour,acids, solvents, organics
4 Petroleum Operations Dust,fume SO2, CO, NH3
H2S Hydrocarbons, mercaptans
5 Food and feed operations Dust - odours
6. Biological decay sewage and refuse Fume, mist, CH4, H2S Odours
7. Cement Dust SO2, NO2, flouride
8. Kraft pulp Dust SO2, CO, H2S Methly, sulphides, methyl mercaptans
9 Metallurgical coke dust SO2, CO, NO2 hydrocarbons
10 Petroleum refining Hydrocarbons SO2, CO, NO2,
NH3 Aldehydes, hydrocarbons
11 Steel mills Dust particulates, fluoride SO2, CO, NH3
gaseous flourides

Various air pollutants have been identified and the principal ones are:

• Sulphur dioxide,
• Carbon monoxide
• Hydrocarbous
• Nitrogen oxides
• Ozone
• Particulates (e.g. dusts)

All the above have adverse effects on peoples health, vegetation, animals, and property.


This is the presence in water (river, stream, lagoon, sea or ocean) of chemical substances which naturally are not present in the water in question. These chemicals substances alter the natural composition and behaviour of the water and are also injurious to fish and other aquatic lives. The chemical substance could be in elemental or compound form.


This is the presence of a sudden change in temperature in air or water, and this is mostly caused by the discharge of very hot fluid into the medium. In water containing aquatic life, this can lead to heat stroke.


Chemical pollution is regarded as the presence of unwanted chemicals in the environment. The presence of these unwanted chemicals can contribute to various hazards.

Most of the problems of environmental pollution we have today are results of man’s activities. By adequate consciousness and careful planning, the different types of environmental pollution mentioned above could be drastically reduced. It is therefore necessary to examine some of our practices and activities in Nigeria to guide us towards better environment care.


Movement about the cities by the use of Cars, Buses, and Motor Cycles has become the norm of the day, especially in big cities. These vehicles either use petrol or diesel fuel as their source of energy. The bye-products of the combustion process is ejected into the atmosphere through the exhaust. Studies conducted outside Nigeria have shown that the exhaust contains air pollutants such as Sulphur dioxide, Nitrogen Oxides, Hydrocarbons, and carbon Monoxide. All the air pollutants mentioned about are harmful to human health in a way. In many countries, anti-pollution devices are installed in the vehicles as standards. Vehicles on Nigerian roads do not have pollution control devices installed in them and with the large number of vehicles moving about in our big cities the contribution to the air pollution problem from the vehicles are very high.


Since the discovery of oil in Nigeria, millions of barrels of this mineral had been extracted from the ground. Accompanying this oil is large quantities of natural gas.

Up till now, larger volumes of the natural gas are being flared. This practice is not only wasteful, but the large amount of heat generated by this flaring constitute significantly to the thermal pollution of that environment. The continuously flaring in these communities affect the roofing sheets , resulting to acid rain, including possible ozone depletion and other health effects The Federal Government realizing the thermal effects on the environment and human health is partnership with Shell Petroleum to annex the Liquefied Gas thereby setting a date for zero gas flaring by end 2008 in Nigeria.


The existence of various industries is vital to maintaining the high standard of living in many countries. In Nigeria, efforts had been laid on industrialization. As mentioned above, the establishment of the industries is sources of environmental deterioration if adequate step is not taken to control wastes from the processes of the industries. Some of the steps could involve that control devices be installed on the waste effluent path or that partial treatment of these wastes to acceptable level should be done before they are finally released into the environment. Whatever approach a company adopts for pollution control constitute an additional cost to the operating cost. The savings made by the companies by not controlling the various pollution is negligible when compared to what its effect will cost the nation in terms of medical bills, damage to vegetation and properties. Some of our major industries are the breweries, textile, cement, iron and steel, petroleum, food and beverages and mining. Studies on some of the wastes from these industries on environmental pollution had proved unsatisfactory. The concentration levels of most of the waste effluents from these industries are above the recommended standards.

In some parts of the country, industries are sited without adequate assessment of their environmental impact. If this practice is not checked, the effect in the future could be very disastrous.

The small-scale industries are on the increase due to the down turn in the economy. They form about 85% of the industries in Nigeria. Despite that they contribute to the development and economic growth they are menace to the community where they are located. Most of these industries are located within residential areas. They contribute about i/3 to the pollution in terms of fumes, wastes (solid and liquid) as well as noise. They have no regard for the environment

By considering the practices of individuals, small groups, and corporate bodies, it is possible to state that the ‘The State of The Environment In Nigeria’ is not satisfactory. This is particularly true if we compare our level of industrialization with that of developed and truly industrialised nations who have more industries but less pollution. A particular group of sector of the community cannot be blamed for this situation. However, it is encouraging that we are all conscious of the problems of past neglect of adequate environmental care and that good care is a joint responsibility of everyone. There should be cooperation with government bodies charged with the responsibility of environmental care and any other group who are concerned about the quality of our environment.

The issue of garbage collection and disposal was not mentioned above because emphasis has been laid on this in the past by various state and local government. Moreover people’s awareness about this aspect of environmental sanitation is very deep. Everyone is however encouraged to still ensure that their immediate surroundings are kept clean and should desist from practices contributing towards having a cleaner and unpolluted environment for Nigeria is very vital.
The environmental impact of oil industry results from activities and processes necessary for successful operation of oil industry. The extent of damage produced by oil pollution depends on the severity of the spillage, the toxicity of the oil, and type of environment. Generally, the discharge of oil into water environment would prevent natural aeration processes and lead to death of aquatic organisms under oil films. Effluents from refineries contain a wide range of organic and inorganic pollutants; such as phenols, hydrogen sulphide, ammonia, oil and grease phosphates and toxic metals. It is a well known fact that these environmental impacts which have resulted in hostile reactions from the community include: -

a) Destruction of vegetation and farm lands, during exploration for siting of wells as well as laying of oil pipes;
b) Continuous presence of light, heat, noise, and in some cases soot emission from flares;
c) Oil pollution of the environment through accidental blow outs, oil pipe line leakages, vandalisation, failure of storage effluents from production and refinery operations;
d) Studies have shown environmental impacts are closely associated with some health problems in the oil producing communities.

8.9 Indoor Air Quality

Exposure to air pollutants and chemicals trigger asthma, a principal cause of school absenteeism. Lead (Pb) in particular put children at risk of diminished intelligence, school failure, delinquency and diminished achievement. The vulnerability of children to these environmental factors also makes these actions imperative, considering that school children are most vulnerable to environmental health hazards because exposures which may be relatively harmless to adults can be potentially devastating to them. Studies have shown that indoor levels of air pollutants are frequently as much as five times, and sometimes more than 100 times, higher than outdoor levels – and most people spend about 90% of their time indoors. One way to clear the air in most homes is to reduce the use of chemicals with harsh or even toxic fumes. Pesticides are one of the bigger culprits. Dust in the air, particles from lead-based paint, mold resulting from dampness and crumbling masonry etc. All these and more can pollute the air in homes. Dust in the air particles lead-based paint, carpet mildew, mold resulting from dampness, road dust, harsh cleansers, pesticides, and fragrances in overcrowded homes.

1. Federal Ministry of Environment 2005, National Environmental Sanitation Policy.
2. Federal Ministry of Environment 2005, Policy Guidelines on Sanitary Inspection of Premises
3. Federal Ministry of Environment 2005, Policy Guidelines on Solid Waste Management
4. Federal Ministry of Environment 2005, Policy Guidelines on Market and Abattoir Sanitation
5. Federal Ministry of Environment 2005, Policy Guidelines on Pest and Vector Control
6. Federal Ministry of Environment 2005, Policy Guidelines on Excreta and Sewage Mangement
7. Federal Ministry of Environment 2005, Policy Guidelines on School Sanitation
8. Federal Ministry of Environment 2005, report of Needs Assessment Survey on Food Sanitation in Nigeria, Federal Government of Nigeria, Abuja.
9. Federal Ministry of Environment 2006, Policy Guidelines on Food Sanitation.
10. Federal Ministry of Environment 2006, Training Manuals for EHPs on Food Sanitation
11. Federal Ministry of Environment 2006, Training Manuals for Food Handlers
12. Guidelines and Standards for Environmental Pollution Control in Nigeria by Federal Environmental Protection Agency (FEPA) Federal Ministry of Environment 1991.
13. S.I.8 National Environmental Protection (Effluent Limitation) Regulations 1991
14. S.I.9 National Environmental Protection (Pollution Abatement in Industries and Facilities generating wastes) regulations 1991
15. S.I. 15 National Environmental Protection Management of Solid and hazardous Wastes Regulations 1991.
16. National Demographic Health Survey 2003 (NDHS)
17. Pediatric Environmental Health 2nd edition, American Academy of Pediatrics

Sewage, and Sullage/Greywater

1.0 Sewage, and Sullage/Greywater

In Nigeria, the major liquid wastes comprise of sullage or grey water and industrial effluents. As the human excreta are separately managed through a large number of practices, the waste water is supposed to be devoid of it. The only exception is when people defecate indiscriminately into drains. Sullage is domestic wastewater other than that which comes from the toilet. It results from food preparation, personal washing, and washing of cooking and eating utensils and clothes. It is also called greywater (to distinguish it from blackwater which describes wastes containing human excreta. Grey water is a Priced Resource. It is being used in urban agriculture. Salad crops which are widely grown on sullage and any available waste water can transmit pathogens. The common favoured crops are: Lettuce, Greens, Carrots, Cabbage, Cucumbers, Tomatoes, and Pepper.

The health hazards posed by sullage are not as serious as those associated with other wastewater containing excrete or septic tank effluent. Counts of faecal indicator bacteria have been reported to be significantly lower in sullage than in septic tank effluent, but the washing of babies' clothes and pappies (diapers) is likely to increase the count substantially. Some data suggest that bacteria grow well in sullage. A substantial danger from pathogens is posed by careless tipping of greywater on the ground. If one particular area is always used, its continual moistness will favour the survival of helminths, such as hookworm, and the breeding of flies and mosquitos. In addition, such an area is more likely to be regarded as a waste dump and so be used for defecation, and this practice will increase the number of parasites. Faeces are not easily seen when the ground is muddy. The main hazard to public health is posed by mosquitos, especially Culex quinquefasciatus, which breed in polluted pond water and may spread bancroftian filariasis. Ponding of sullage is caused by excessive discharge on to the ground, by blockage of surface drains, or by unsatisfactory construction or maintenance of open channels to carry the sullage. Pollution of groundwater by sullage may be of less concern than the pollution threat from other wastewater, because the bacterial and nitrate contents are relatively low.

Sewage or Wastewater originates mainly from domestic, industrial, groundwater, and meteorological sources and these forms of wastewater are commonly referred to as domestic sewage, industrial waste, infiltration, and storm-water drainage, respectively. Domestic sewage results from people's day-to-day activities, such as bathing, body elimination, food preparation, and recreation, averaging about 227 litres (about 60 gallons) per person daily. The quantity and character of industrial wastewater is highly varied, depending on the type of industry, the management of its water usage, and the degree of treatment the wastewater receives before it is discharged. A steel mill, for example, might discharge anywhere from 5700 to 151,000 liters (about 1500 to 40,000 gallons) per ton of steel manufactured. Less water is needed if recycling is practiced. A typical metropolitan area discharges a volume of wastewater equal to about 60 to 80 percent of its total daily water requirements, the rest being used for washing cars and watering lawns, and for manufacturing processes such as food canning and bottling.

2.0 Sewage Disposal – Historical Perspective

The issue of sewage disposal assumed increasing importance in the early 1970s as a result of the general concern expressed in the United States and worldwide about the wider problem of pollution of the human environment, the contamination of the atmosphere, rivers, lakes, oceans, and groundwater by domestic, municipal, agricultural, and industrial waste.

Methods of wastewater disposal dates back to ancient times, and sanitary sewers have been found in the ruins of the prehistoric cities of Crete and the ancient Assyrian cities. Storm- water sewers built by the Romans are still in service today. Although the primary function of these was drainage, the Roman practice of dumping refuse in the streets caused significant quantities of organic matter to be carried along with the rainwater runoff. Toward the end of the Middle Ages, below-ground privy vaults and, later, cesspools were developed. When these containers became full, sanitation workers removed the deposit at the owner's expense. The wastes were used as fertilizer at nearby farms or were dumped into watercourses or onto vacant land.

A few centuries later, there was renewed construction of storm sewers, mostly in the form of open channels or street gutters. At first, disposing of any waste in these sewers was forbidden, but by the 19th century it was recognized that community health could be improved by discharging human waste into the storm sewers for rapid removal. Development of municipal water-supply systems and household plumbing brought about flush toilets and the beginning of modern sewer systems. Despite reservations that sanitary sewer systems wasted resources, posed health hazards, and were expensive, many cities built them; by 1910 there were about 25,000 miles of sewer lines in the United States.

At the beginning of the 20th century, a few cities and industries began to recognize that the discharge of sewage directly into the streams caused health problems, and this led to the construction of sewage-treatment facilities. At about the same time, the septic tank was introduced as a means of treating domestic sewage from individual households both in suburban and rural areas. Because of the abundance of diluting water and the presence of sizable social and economic problems during the first half of the 20th century, few municipalities and industries provided wastewater treatment.

During the 1950s and 1960s, the U.S. government encouraged the prevention of pollution by providing funds for the construction of municipal waste-treatment plants, water-pollution research, and technical training and assistance. New processes were developed to treat sewage, analyze wastewater, and evaluate the effects of pollution on the environment. In spite of these efforts, however, expanding population and industrial and economic growth caused the pollution and health difficulties to increase. In response to the need to make a coordinated effort to protect the environment, the National Environmental Policy Act (NEPA) was signed into law on January 1, 1970. In December of that year, a new independent body, the Environmental Protection Agency (EPA) was created to bring under one roof all of the pollution-control programs related to air, water, and solid wastes. In 1972 the Water Pollution Control Act Amendments expanded the role of the federal government in water pollution control and significantly increased Federal funding for construction of waste-treatment works. US Congress has also created regulatory mechanisms and established uniform effluent standards.

3.0 Sewer Lines

Wastewater is carried from its source to treatment facility pipe systems that are generally classified according to the type of wastewater flowing through them. If the system carries both domestic and storm-water sewage, it is called a combined system, and these usually serve the older sections of urban areas. As the cities expanded and began to provide treatment of sewage, sanitary sewage was separated from storm sewage by a separate pipe network. This arrangement is more efficient because it excludes the voluminous storm sewage from the treatment plant. It permits flexibility in the operation of the plant and prevents pollution caused by combined sewer overflow, which occurs when the sewer is not big enough to transport both household sewage and storm water. Another solution to the overflow problem has been adopted by Chicago, Milwaukee, and other U.S. cities to reduce costs: instead of building a separate household sewer network, large reservoirs, mostly underground, are built to store the combined sewer overflow, which is pumped back into the system when it is no longer overloaded.

Households are usually connected to the sewer mains by clay, cast-iron, or polyvinyl chloride (PVC) pipes 8 to 10 cm (3 to 4 in) in diameter. Larger-diameter sewer mains can be located along the centerline of a street or alley about 1.8 m (about 6 ft) or more below the surface. The smaller pipes are usually made of clay, concrete, or asbestos cement, and the large pipes are generally of unlined or lined reinforced-concrete construction. Unlike the water-supply system, wastewater flows through sewer pipes by gravity rather than by pressure. The pipe must be sloped to permit the wastewater to flow at a velocity of at least 0.46 m per sec (1.5 ft per sec), because at lower velocities the solid material tends to settle in the pipe.

4.0 Composition of Waste Water

The composition of wastewater is analyzed using several physical, chemical, and biological measurements. The most common analyses include the measurements of solids, biochemical oxygen demand (BOD5), chemical oxygen demand (COD), and pH. The solid wastes include dissolved and suspended solids. Dissolved solids are the materials that will pass through a filter paper, and suspended solids are those that do not. The suspended solids are further divided into settleable and nonsettleable solids, depending on how many mg of the solids will settle out of 1 liter of wastewater in 1 hour. All these classes of solids can be divided into volatile or fixed solids, the volatile solids generally being organic materials and the fixed solids being inorganic or mineral matter.

Typical values of solids and BOD5 for domestic wastewater are given in the accompanying table. The organic matter in typical domestic sewage is approximately 50 percent carbohydrates, 40 per cent protein, and 10 per cent fat; the pH can range from 6.5 to 8.0. The composition of industrial waste cannot be readily characterized by a typical range of values because its makeup depends on the type of manufacturing process involved.

The concentration of an industrial waste is usually placed in perspective by stating the number of people, or population equivalent (PE), that would be required to produce the same quantity of waste. PE is most commonly expressed in terms of BOD5. An average value of 0.077 kg (0.17 lb) 5-day, 20°C BOD per person per day is used for determination of the PE. The population equivalent of a slaughterhouse operation, for example, will range from 5 to 25 PE per animal.

The concentration of organic matter is measured by the BOD5 and COD analyses. The BOD5 is the amount of oxygen used over a five-day period by microorganisms as they decompose the organic matter in sewage at a temperature of 20° C (68° F). The COD is the amount of oxygen required to oxidize the organic matter by use of dichromate in an acid solution and to convert it to carbon dioxide and water. The value of COD is always higher than that of BOD5 because many organic substances can be oxidized chemically but cannot oxidize biologically. Commonly, BOD5 is used to test the strength of untreated and treated municipal and biodegradable industrial wastewaters. COD is used to test the strength of wastewater that is either not biodegradable or contains compounds that inhibit activities of microorganisms. The pH analysis is a measure of the acidity of a wastewater.

5.0 Industrial wastes

Industrial wastes may be grouped into 2 broad categories: Process wastes and chemical wastes. The process wastes depend on the nature of the industry, the raw materials processed and nature of the process itself. The industrial wastes may pose serious problems on receiving bodies, e.g. oxygen depletion, emission of noxious gases, fish kills and change in flora and fauna. The common pollution problems include high pollution load in the form of colour, turbidity, odour, heat, suspended solids, dissolved solids, BOD, COD, various inorganic elements, volatile organic compounds, toxic chemicals and others. Similarly, the solid wastes originating from human and other activities and their leachates entering the water and food chains may effect the environment and health. At the moment, a majority of the industries either treat their wastes minimally or do not treat at all.

The options for industrial waste disposal are to discharge into surface waters, coastal waters, land and sewers, if available. Depending on where they are disposed, the effluent quality has to be maintained. The flow rates, weather conditions, and the waste characteristics over a time scale are required before planning a treatment technology.

6.0 Waste Water Management Technologies

There is a need to treat such wastes and bring them back into the cycle of life. Several developments have taken place during the last century to manage the wastes. Earlier days it was thought that “solution to pollution is dilution” and this approach never yielded any positive result. The chemical coagulation using lime, ferric salts and alum did not yield any significant results and on the other hand the rivers have deteriorated to a great extent. The available technologies are: primary treatment, secondary treatment and tertiary treatment. Sedimentation tanks, pH control, trickling or percolating filters, activated sludge process, oxidation pond, oxidation ditches, Root Zone Technology, sludge digestion, aerobic and anaerobic lagoon are some of the technologies which are used in dealing with the liquid wastes. Pretreatment is essential before going for biological treatment.

6.1 Primary Treatment

 The wastewater that enters a treatment plant contains debris that might clog or damage the pumps and machinery. Such materials are removed by screens or vertical bars, and the debris is burned or buried after manual or mechanical removal.
 The wastewater then passes through a comminutor (grinder), where leaves and other organic materials are reduced in size for efficient treatment and removal later.
 Grit Chamber- In the past, long and narrow channel-shaped settling tanks, known as grit chambers, were used to remove inorganic or mineral matter such as sand, silt, gravel, and cinders. These chambers were designed to permit inorganic particles 0.2 mm (0.008 in) or larger to settle at the bottom while the smaller particles and most of the organic solids that remain in suspension pass through. Today, spiral-flow aerated grit chambers with hopper bottoms, or clarifiers with mechanical scrapper arms, are most commonly used. The grit is removed and disposed of as sanitary landfill. Grit accumulation can range from 0.08 to 0.23 cu m (3 to 8 cu ft) per 3.8 million liters (about 1 million gallons) of wastewater.

 Sedimentation - with grit removed, the wastewater passes into a sedimentation tank, in which organic materials settle out and are drawn off for disposal. The process of sedimentation can remove about 20 to 40 percent of the BOD5 and 40 to 60 % of the suspended solids. The rate of sedimentation is increased in some industrial waste-treatment stations by incorporating processes called chemical coagulation and flocculation in the sedimentation tank. Coagulation is the process of adding chemicals such as aluminum sulfate, ferric chloride, or polyelectrolytes to the wastewater; this causes the surface characteristics of the suspended solids to be altered so that they attach to one another and precipitate. Flocculation causes the suspended solids to coalesce. Coagulation and flocculation can remove more than 80 percent of suspended solids.

 Flotation - an alternative to sedimentation that is used in the treatment of some wastewaters is flotation, in which air is forced into the wastewater under pressures of 1.75 to 3.5 kg per sq cm (25 to 50 lb per sq in). The wastewater, supersaturated with air, is then discharged into an open tank; there the rising air bubbles cause the suspended solids to rise to the surface, where they are removed. Flotation can remove more than 75 percent of the suspended solids.

 Digestion - is a microbiological process that converts the chemically complex organic sludge to methane, carbon dioxide, and an inoffensive humus like material. The reactions occur in a closed tank or digester that is anaerobic—that is, devoid of oxygen. The conversion takes place through a series of reactions. First the solid matter is made soluble by enzymes, then the substance is fermented by a group of acid-producing bacteria, reducing it to simple organic acids such as acetic acid. The organic acids are then converted to methane and carbon dioxide by bacteria. Thickened sludge is heated and added as continuously as possible to the digester, where it remains for 10 to 30 days and is decomposed. Digestion reduces organic matter by 45 to 60 percent. Digested sludge is placed on sand beds for air drying. Percolation into the sand and evaporation are the chief processes involved in the dewatering process. Air drying requires dry, relatively warm weather for greatest efficiency, and some plants have a greenhouse like structure to shelter the sand beds. Dried sludge in most cases is used as a soil conditioner; sometimes it is used as a fertilizer because of its 2 percent nitrogen and 1 percent phosphorus content.

6.2 Secondary Treatment

Having removed 40 to 60 percent of the suspended solids and 20 to 40 percent of the BOD5 in primary treatment by physical means, the secondary treatment biologically reduces the organic material that remains in the liquid stream. Usually the microbial processes employed are aerobic—that is, the organisms function in the presence of dissolved oxygen. Secondary treatment actually involves harnessing and accelerating nature's process of waste disposal. Aerobic bacteria in the presence of oxygen convert organic matter to stable forms such as carbon dioxide, water, nitrates, and phosphates, as well as other organic materials. Several alternative processes available in secondary treatment are: trickling filter, activated sludge, and lagoons.

 Trickling Filter- In this process, a waste stream is distributed intermittently over a bed or column of some type of porous medium. A gelatinous film of microorganisms coats the medium and functions as the removal agent. The organic matter in the waste stream is absorbed by the microbial film and converted to carbon dioxide and water. The trickling-filter process, when preceded by sedimentation, can remove about 85 % of the BOD5 entering the plant.

 Activated Sludge- This is an aerobic process in which gelatinous sludge particles are suspended in an aeration tank and supplied with oxygen. The activated-sludge particles, known as floc, are composed of millions of actively growing bacteria and protozoa bound together by a gelatinous slime. Organic matter is absorbed by the floc and converted to aerobic products. The reduction of BOD5 fluctuates between 60 and 85 %. An important companion unit in any plant using activated sludge or a trickling filter is the secondary clarifier, which separates bacteria from the liquid stream before discharge. The inventorDr Gilbert Fowler is given in th ephotograph.

Activated Sludge is modified and various designs are currently available –Conventional, Step Aration, Contact Stabilization, Plug Flow, Completely mix and other types. Oxidation Ditch is another improved design which is more economical and suitable for small scale waste treatment, e.g. poultry, piggery etc. In providing secondary treatment plants, various parameters are to be measured and computed. Some of them are: Hydraulic Retention Rate (HRT), Volumetric loading: BOD5 applied per unit volume of aeration tank, and Organic Loading Rate or F/M ratio – it is the ratio of Kg BOD5 applied per day (representing microbial feed) to Kg MLSS in aeration tank (representing microorganisms). The F/M ratio is the main factor controlling BOD removal. Lower the F/M value, the higher will be the BOD removal

 Septic Tank System - A sewage treatment process commonly used to treat domestic wastes is the septic tank: a concrete, cinder block or metal tank where the solids settle and the floatable materials rise. The partly clarified liquid stream flows from a submerged outlet into subsurface rock-filled trenches through which the wastewater can flow and percolate into the soil where it is oxidized aerobically. The floating matter and settled solids can be held from six months to several years, during which they are decomposed anaerobically.

 Stabilization Pond or Lagoon - Another form of biological treatment is the stabilization pond or lagoon, which requires a large land area and thus is usually located in rural areas. Facultative lagoons, or those that function in mixed conditions, are the most common, being 0.6 to 1.5 m (2 to 5 ft) in depth, with a surface area of several acres. Anaerobic conditions prevail in the bottom region, where the solids are decomposed; the region near the surface is aerobic, allowing the oxidation of dissolved and colloidal organic matter. A reduction in BOD5 of 75 to 85 % can be attained.

 Waste Stabilization Ponds - Perhaps one of the most ancient wastewater treatment methods known to humans are waste stabilization ponds, also known as oxidation ponds or lagoons. They're often found in small rural areas where land is available and cheap. Such ponds tend to be only a meter to a meter and a half deep, but vary in size and depth, and may be three or more meters deep. They utilize natural processes to "treat" waste materials, relying on algae, bacteria, and zooplankton to reduce the organic content of the wastewater. A "healthy" lagoon will appear green in color because of the dense algae population. These lagoons require about one acre for every 200 people served. Mechanically aerated lagoons only need 1/3 to 1/10 the land that unaerated stabilization ponds requires. It's a good idea to have several smaller lagoons in series rather than one big one; normally, a minimum of three "cells" are used. Sludge collects in the bottom of the lagoons, and may have to be removed every five or ten years and disposed of in an approved manner.

6.3 Advanced Wastewater Treatment

If the receiving body of water requires a higher degree of treatment than the secondary process can provide, or if the final effluent is intended for reuse, advanced wastewater treatment is necessary. The term tertiary treatment is often used as a synonym for advanced treatment, but the two methods are not exactly the same. Tertiary, or third-stage, treatment is generally used to remove phosphorus, while advanced treatment might include additional steps to improve effluent quality by removing refractory pollutants. Processes are available to remove more than 99 percent of the suspended solids and BOD5. Dissolved solids are reduced by processes such as reverse osmosis and electrodialysis, ammonia stripping, denitrification, and phosphate precipitation can remove nutrients. If the wastewater is to be reused, disinfection by ozone treatment is considered the most reliable method other than breakpoint chlorination. Application of these and other advanced waste-treatment methods is likely to become widespread in the future in view of new efforts to conserve water through reuse.

 Anaerobic Ponds - Anaerobic ponds are commonly 2-5 m deep and receive such a high organic loading (usually >100g BOD/m3 d equivalent to >3000 kg/ha/d for a depth of 3 m). They contain an organic loading that is very high relative to the amount of oxygen entering the pond, which maintains anaerobic conditions to the pond surface. Anaerobic ponds don’t contain algae, although occasionally a thin film of mainly Chlamydomonas can be seen at the surface. They work extremely well in warm climate (can attain 60-85% BOD removal) and have relatively short retention time (for BOD of up to 300 mg/l, one day is sufficient at temperature >20oC). Anaerobic ponds reduce N, P, K and pathogenic micro-organisms by sludge formation and the release of ammonia into the air. As a complete process, the anaerobic pond serves to separate out solid from dissolved material as solids settle as bottom sludge, dissolve further organic material, break down biodegradable organic material, store undigested material and non-degradable solids as bottom sludge, and allow partially treated effluent to pass out.

These fermentation processes and the activity of anaerobic oxidation throughout the pond remove about 70% of the BOD5 of the effluent. This is a very cost-effective method of reducing BOD5. Normally, a single anaerobic pond in each treatment is sufficient if the strength of the influent wastewater is less than 1000 mg/l BOD5. BOD removals and Nitrogen Changes in Anaerobic Ponds loaded at 250 g BOD5/m3d. In anaerobic ponds organic nitrogen is hydrolyzed to ammonia, so ammonia concentrations in anaerobic pond effluents are generally higher than in the raw wastewater (unless the time of travel in the sewer is so long that all the urea has been converted before reaching the WSP). Volatilization of ammonia seems to be the only likely nitrogen removal mechanism occurring to some extent in anaerobic ponds.

 Fluidized Bed Technique – Sridhar and his colleagues designed a modified version of this and used this technology to treat sewage in 1974 which is currently being used by Ademoroti and his colleagues at University of Benin in treating sewage and other industrial wastes. Sewage treatment using plastic beads under aeration in a reactor proved the importance of attached micro-organisms particularly ciliate protozoa- Vorticella sp. in the biological treatment.

 Root Zone Technology- Yet another technology widely studied in Nigeria (Sridhar and his colleagues 2005) , certain aquatic plants (Pistia and Water Hyacinth), and terrestrial plants (Phragmites, Canna lily, Ipomea and others) can also be effectively used for the treatment of small volumes of municipal wastewater, particularly where construction of a sewage collection system to an adjacent wastewater treatment facility would be prohibitively expensive.

 Wetlands as Wastewater Treatment Systems - Natural wetlands have been and continue to be used as wastewater disposal sites. Their ability to act as a buffer, absorbing some of the substances released, has afforded some protection to the rivers, lakes, and estuaries to which they are linked. However, a large proportion of wetlands have been destroyed for construction or agricultural purposes. Apart from the fact that wetlands are vital habitats for a large variety of phylogenetic species, the loss of their role as natural purification systems may be the most critical aspect of this destruction. In wastewater treatment, wetlands are utilized mostly as a chemical sink. In natural ecosystems, wetlands perform other important roles in the transformation of inputs and sources of chemicals for the neighbouring systems. The biogeochemical conditions and factors that define these roles of the particular wetland need to be determined in order to optimize the contaminant trapping aspect.

 Adsorption, Ultrafiltration and other Technologies - In the wastewater treatment, the technology option depends on the goal. One should find out which element or substance is to be reduced or eliminated from the effluents. BOD, SS, Volatile organics, some specific chemicals such as P, N, S, or heavy metals or toxic chemicals have to be addressed. On certain situations adsorbents such as activated charcoal, clays (kaolin or bentonite) may be very useful. Ultrafiltration is becoming more acceptable and the cost of the technology is coming down as more and more innovations are being adopted.

In addition to these treatment methods, sludge has to be disposed of hygienically. Sludge digestion is a preferred method and biogas and fertilizer are the byproducts.

7.0 Conclusions

Hitherto, in Nigeria the emphasis in waste management has been limited to solid wastes. Proper treatment is not practiced in many industries in the country. The regulatory bodies on the other hand have been very sympathetic and have been giving ‘holidays’ for industry for not implementing any treatment facilities. Almost after 13 years of its creation, FEPA (Ministry of Environment where appropriate) have to go into action on enforcing effective treatment and adhering to the stipulated standards.
• There is need to strengthen Federal, State and selected private laboratories to cope with the needs and demand of waste characterization;
• At the moment many unqualified ‘touts’ have entered into the field as ‘Environmental Consultants’; there is need to screen and weed them out;
• Quality assurance, inter-laboratory standardization and periodic training and retraining of all ‘Environmental Practitioners’ should be made mandatory;
• Environment is multidisciplinary and in tackling the problems, a team effort is more beneficial; where necessary many should join hands in solving the problems;
• A National ‘Green Peace’ Group should be formed and encouraged to monitor the industries, communities and regulatory bodies in keeping the environment clean and habitable; and
• There is need to take stock of the availability of technologies and the expertise within the country through proper screening and draft them to address the environmental challenges.

Selected References

Ademoroti, C. M. A. and Sridhar, M. K. C. (1979), Fluidized bed technique in physicochemical treatment
Effluent and Water Treatment Journal, U.K., 19: 291-297
Hammer, M. J. (1986), Water and Wastewater Technology, SI Version, Second Edition, John Wiley & Sons, New
York, pp 1-536
Peavy, H. S., Rowe, D. R. and Tchobanoglous, G. (1985), Environmental Engineering, McGraw-Hill International
Editions, Civil Engineering Series, New York, pp. 1-677
Sridhar, M. K. C. and Oyemade, O. (1987), Health risks at sewage treatment plants in Ibadan, Nigeria
Journal of Institution of Water and Environmental Management, U.K., 1: 129-135
Sridhar, M. K. C. (1991), Textile mill wastes in Nigeria--Problems and treatment options, Proceedings of a Special
Symposium on Emerging Technologies for Hazardous Waste Management, Edited by D. Willaim Tedder, , Atlanta, Georgia, Industrial and Engineering Division, American Chemical Society, pp.13 in a Volume of pp 1-431
Sridhar, M. K. C. (1995), Sullage / Waste Water in Nigeria: Problems and Solutions for Utilization for Gardening, A
report submitted to UNICEF, Lagos, Nigeria, July, pp.1-86