1. Kanu, Ijeoma and Achi, O.K., 2011. Industrial Effluents and Their Impact on Water Quality of Receiving Rivers in
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Journal of Applied Technology in Environmental Sanitation, 1 (1): 75-86.
Practical Case Study
INDUSTRIAL EFFLUENTS AND THEIR IMPACT ON WATER QUALITY OF
RECEIVING RIVERS IN NIGERIA
KANU, IJEOMA and ACHI, O.K.*
Department of Microbiolog, Michael Okpara University of Agriculture, Umudike, PMB 7267, Abia State,
Nigeria.
*Corresponding Author: Phone/Fax: +23408068750963; Email: omekachi@yahoo.com
Received: 15th April 2011 Revised: 9th May 2011; Accepted: 9th May 2011
Abstract: Industrial wastewaters entering a water body represent a heavy source of
environmental pollution in Nigerian rivers. It affects both the water quality as well as the
microbial and aquatic flora. With competing demands on limited water resources,
awareness of the issues involved in water pollution, has led to considerable public
debate about the environmental effects of industrial effluents discharged into aquatic
environments. Industrial effluents are characterized by their abnormal turbidity,
conductivity, chemical oxygen demand (COD), total suspended solids (TSS), biological
oxygen demand (BOD), and total hardness. Industrial wastes containing high
concentration of microbial nutrients would obviously promote an after-growth of
significantly high coliform types and other microbial forms. Organic pollution is always
evident and the pollution is made worse by land-based sources such as the occasional
discharge of raw sewage through storm water outlets, and industrial effluents from
refineries, oil terminals, and petrochemical plants. Waste effluents rich in
decomposable organic matter, is the primary cause of organic pollution. Waste waters
from textile, brewery, food and beverages, paper, pulp and palm oil industries, the
cases chosen, are believed to give a broad outline of industrial wastes as well as
disposal problems.
Keywords: Industrial effluents, water quality, BOD, COD, TSS
INTRODUCTION
One of the most critical problems of developing countries is improper management of vast
amount of wastes generated by various anthropogenic activities. More challenging is the unsafe
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© T2011 Department of Environmental Engineering
Sepuluh Nopember Institute of Technology, Surabaya
& Indonesian Society of Sanitary and Environmental Engineers, Jakarta
O p e n A c c e s s h t t p : / / w w w . t r i s a n i t a . o r g / j a t e s
This work is licensed under the Creative Commons Attribution 3.0 Unported License, which permits
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2. Kanu, Ijeoma and Achi, O.K., 2011. Industrial Effluents and Their Impact on Water Quality of Receiving Rivers in
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disposal of these wastes into the ambient environment. Water bodies especially freshwater
reservoirs are the most affected. This has often rendered these natural resources unsuitable for
both primary and/or secondary usage [1].
Industrial effluent contamination of natural water bodies has emerged as a major challenge
in developing and densely populated countries like Nigeria. Estuaries and inland water bodies,
which are the major sources of drinking water in Nigeria, are often contaminated by the activities
of the adjoining populations and industrial establishments [2].
River systems are the primary means for disposal of waste, especially the effluents, from
industries that are near them. These effluent from industries have a great deal of influence on the
pollution of the water body, these effluent can alter the physical, chemical and biological nature of
the receiving water body [3]. Increased industrial activities have led to pollution stress on surface
waters both from industrial, agricultural and domestic sources [4].
Wastes entering these water bodies are both in solid and liquid forms. These are mostly
derived from Industrial, agricultural and domestic activities. As a result, water bodies which are
major receptacles of treated and untreated or partially treated industrial wastes have become
highly polluted. The resultant effects of this on public health and the environment are usually
great in magnitude [5].
Over the last years, in many African countries a considerable population growth has taken
place, accompanied by a steep increase in urbanization, industrial and agricultural land use. This
has entailed a tremendous increase in discharge of a wide diversity of pollutants to receiving
water bodies and has caused undesirable effects on the different components of the aquatic
environment and on fisheries [6]. As a result, there is growing appreciation that nationally,
regionally, and globally, the management and utilization of natural resources need to be improved
and that the amount of waste and pollution generated by human activity need to be reduced on a
large scale.
Industries are the major sources of pollution in all environments. Based on the type of
industry, various levels of pollutants can be discharged into the environment directly or indirectly
through public sewer lines. Wastewater from industries includes employees’ sanitary waste,
process wastes from manufacturing, wash waters and relatively uncontaminated water from
heating and cooling operations [7]. High levels of pollutants in river water systems causes an
increase in biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved
solids (TDS), total suspended solids (TSS), toxic metals such as Cd, Cr, Ni and Pb and fecal
coliform and hence make such water unsuitable for drinking, irrigation and aquatic life. Industrial
wastewaters range from high biochemical oxygen demand (BOD) from biodegradable wastes
such as those from human sewage, pulp and paper industries, slaughter houses, tanneries and
chemical industry. Others include those from plating shops and textiles, which may be toxic and
require on-site physiochemical pre-treatment before discharge into municipal sewage system [8-
10].
Organic pollution of inland water systems in Africa, in contrast to the situation in developed
countries of the world, is often the result of extreme poverty and economic and social under-
development. According to Tolba [11], it is in these countries that the quality of water, and often
the quantity, is lowest, sanitation and nutrition the worst and disease most prevalent.
Unfortunately, there are very few water quality studies for most African inland waters. In general,
the available data come from scattered investigations, which were carried out by individuals and
by very few scientific projects concerned with African waters. Few reviews exist on the state of
pollution of African inland waters [12-14].

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With competing demands on limited water resources, industrial pollution remains one of the
major problems facing Nigerian cities. As societies throughout the world become more aware of
the issues involved in water pollution, there has been considerable public debate about
environmental effects of effluents discharged into aquatic environments [15].
Effluent discharge practices in Nigeria are yet too crude and society is in danger, especially
in the industrialized part of the cities. The Federal Environmental Protection Agency (FEPA)
established to check these environmental abuses has had little or no impact on pollution control
in our cities [16]. The aim of this review is to assess the impact of industrial wastewater pollution
on aquatic environments in Nigeria.
THE USE OF WATER BODIES AS SINK FOR INDUSTRIAL EFFLUENTS
Population explosion, haphazardous rapid urbanization, industrial and technological
expansion, energy utilization and wastes generation from domestic and industrial sources have
rendered many water resources unwholesome and hazardous to man and other living resources.
Water pollution is now a significant global problem [17].
Industrial effluents are a main source of direct and often continuous input of pollutants into
aquatic ecosystems with long-term implications on ecosystem functioning including changes in
food availability and an extreme threat to the self-regulating capacity of the biosphere. These
industrial discharge or wastes include heavy metals, pesticides, polychlorinated biphenyls
(PCBs), dioxins, poly-aromatic hydrocarbons (PAHs), petrochemicals, phenolic compounds and
microorganisms [1], [18-21]. These wastes are usually discharged into water bodies and the
cumulative hazardous effects it has on the environment have received much attention. Industrial
wastes containing high concentration of microbial nutrients would obviously promote an after-
growth of significantly high coliform types and other microbial forms. Some heavy metals
contained in these effluents have been found to be carcinogenic while other chemicals equally
present are poisonous depending on the dose and duration of exposure. Undoubtedly,
wastewaters from industries and residential areas discharged into another environment without
suitable treatment could disturb the ecological balance of such an environment [21].
Historically, the availability of water supplies has long been a dominant criterion in citing
towns or cities and the development of great civilizations. The Egyptians civilization flourished
around the river Nile. In Nigeria, cities like Kaduna, Lagos and Aba depend very much on its
rivers. However, the rush by African countries to industrialize has resulted in discharge of
partially treated or raw wastes into the surrounding bodies of water since the development of
treatment facilities cannot keep pace with the rate at which the wastes are generated by the
industries [22].
The industrial discharge, therefore contribute a larger portion of the flow of the river during
the dry season, with the result that the water quality of the river is further deteriorated. Uses, for
which the river is employed involving body contact, expose serious hazards to users due to the
bacterial situation. Many bodies of water in Nigeria experience seasonal fluctuations, leading to a
higher concentration of pollutants during the dry season when effluents are least diluted [23].
NATURE AND CHARACTERISTICS OF EFFLUENTS
Wastewaters are generated by many industries as a consequence of their operation and
processing. Depending on the industry and their water use, the wastewaters contain suspended

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solids, both degradable and nonbiodegradable organics; oils and greases; heavy metal ions;
dissolved inorganics; acids, bases and colouring compounds (Table 1)[24].
Table 1: Examples of Waste Effluents Generated by Selected Industries
Type of waste Type of plant
Oxygen-consuming Breweries, Dairies, Distillers, Packaging houses, Pulp and Paper,
Tanneries, Textiles
High Suspended Solids Breweries, Coal washeries, Iron and Steel Industries, Distillers, Pulp
and Paper mills, Palm oil mills
High dissolved solids Chemical plants, Tanneries, Water softening
Oily and grease Laundries, Metal finishing, Oil fields, Petroleum refineries, Tanneries,
Palm oil mills
Coloured Pulp and Paper mills, Tanneries, Textile dyehouses, Palm oil mills
High acid Chemical plants, Coal mines, Iron and Steel, Sulfite pulp
High alkaline Chemical plants, Laundries, Tanneries, Textile finishing mills
High Temperature Bottle washing plants, Laundries, Power plant, Textile[24]
Industrial effluent characteristics provide basic information about the integrity of the aquatic
habitat within such rivers and streams into which they are discharged. Most of these effluents
pose inestimable harm to which the microbial entity is the most adversely affected. In Nigeria,
there are many small to large cottage industrial establishments that discharge such harmful
wastewater effluents. Although, the physicochemical analysis of the effluents indicates that most
of these industries conform to the recommended FEPA [25] guidelines, however, exceptions
occur in the total dissolved solids (TDS) and Nitrate (NO3-) contents. These are found to be very
high in most of the effluents sampled to which humans and the aquatic habitat are adversely
affected. It is known that the pH analysis of such effluents shows that effluents from food and
beverage industries tend to be abnormally very acidic [26]. An important pollution index of
industrial wastewaters is the oxygen function measured in terms of chemical oxygen demand
(COD), and biological oxygen demand (BOD5), while the nutrient status of wastewater are
measured in terms of nitrogen and phosphorus. In addition, other important quality parameters
include pH, temperature and total suspended solids [27].
Industrial effluents are characterized by their abnormal turbidity, conductivity, chemical
oxygen demand (COD); total suspended solids (TSS) and total hardness. The effluent total
hardness concentrations of a chemical-biological treatment plant were found greater than the
influents. The results are presented in terms of the relative flux as a function of time related to
hydrodynamic conditions and pollution characteristics of wastewater [28]. The dominant soluble
nitrogen form in a typical industrial effluent is NO3-N followed by Kjeldahl-N, NO1-N and non-ionic
ammonia Mean values of NO3-N, NO2-N, Kjeldahl-N and non-ionic ammonia ranged from 0.50
to 2.37 mg L-1, 0.022 to 0.084 mg L-1, 0.33 to 0.99 mg L-1 and 0.007 to 0.092 mg L-1 respectively.
Mean values of P-PO4 at most sampling sites were higher than 0.1 mg L-1 for subject to
eutrophication and the characteristics of rivers and the nearby soils near them affect the
equilibrium concentrations of N and P between the soil and the overlying water Industrial effluents
are also known to exhibit toxicity toward different aquatic organisms.
The coastal residential environment in any industrial effluent site is always under
considerable stress due to the prevailing harsh environmental conditions, especially high
temperature and salinity, restricted benthic fauna diversity and overall development of a fragile

5. Kanu, Ijeoma and Achi, O.K., 2011. Industrial Effluents and Their Impact on Water Quality of Receiving Rivers in
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intertidal ecosystem. The fauna inhabiting the intertidal zone is most likely dominated by a few
species probably living at their limit of tolerance [29]. Organic pollution is always evident and the
pollution is made worse by land-based sources such as the occasional discharge of raw sewage
through storm water outlets, and industrial effluents from refineries, oil terminals, and
petrochemical plants [30].
Wastes produced by the textile industries have characteristically high concentration of
chemicals. The net effect is a variation of the acid or basic nature of the water. Textiles industries
produce chemicals with high concentration of caustic chemicals resulting in high pH values
varying between 10.0 -11.0. The discharge from the textiles, also bear intense colouration derived
from the dyes fibrous materials.
SOURCES OF INDUSTRIAL EFFLUENTS
Pharmaceutical industry
Pharmaceutical and personal care products (PPCPs) industries suffer from inadequate
effluent treatment due to the presence of recalcitrant substances and insufficient carbon sources
and nutrients. A large number of pretreatment systems are employed to remove these pollutants
to prevent a host of problems that may otherwise arise in the biological process, and reduce the
efficiency of the treatment plant. Problems caused by excessive PPCPs in the environment
include possible inhibition on microorganisms, a reduction in the cell-aqueous phase transfer
rates, a sedimentation hindrance due to the development of filamentous microorganisms,
development and flotation of sludge with poor activity, clogging and the emergence of unpleasant
odours. Therefore, it is not surprising that research efforts have been directed towards the
development of efficient treatment technologies including various physicochemical and biological
processes. Some of the most representative pharmaceutical and personal care products found in
receiving waters include antibiotics, lipid regulators, antiinflammatories, antiepileptics,
tranquilizers, and cosmetic ingredients containing oil and grease with very different chemical
structures [31]. Conventional biological processes (activated sludge, trickling filters) can
effectively accomplish carbon and nitrogen removal, as well as microbial pollution control.
However, pharmaceutical and personal care products contain many different compounds for
which conventional technologies have not been specifically designed. Their removal efficiencies
are influenced, apart by the chemical properties of specific compounds, by microbial activity and
environmental conditions. The application of a pretreatment to hydrolyze the effluents and
bioaugmentation, may improve the biological degradation.
Soap and detergent Industry
Alkyl sulfates (AS) are anionic surfactants widely used in household and personal cleansing
applications. Aquatic toxicity of AS under laboratory conditions indicated effects at relatively low
concentrations (50-230 µg L-1) for some sensitive species. Belanger et al, [32] conducted a
comprehensive study of an AS mixture composed of tetra-C14) and pentadecyl (C15) chain
lengths to better understand effects on microbial and macroinvertebrate populations and
communities. A 56-d exposure of AS was performed at concentrations ranging from 57 to 419 µg
L-1 (analytically confirmed exposures) and was accompanied by detailed investigations of
periphyton community function (autotrophy, heterotrophy, and metabolism of test chemical).
Periphyton structure (algal population and community dynamics based on taxonomic identity),
invertebrate structure (benthic abundance, drift), and insect emergence patterns based on

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taxonomic identity were also studied. A no-observed-effect-concentration (NOEC) of 222 µg L-1
was concluded for several individual algal and invertebrate species based on univariate statistical
analyses. An apparent energetic subsidy from C14-15AS at the highest concentrations of 222 to
419 µg L-1 was observed and tied to changes in microbial community processing of AS when
added at these high concentrations. A multivariate analysis based on principal response curves
(PRC) indicated that communities in streams exposed to 222 to 419 µg L-1 were significantly
different from the controls leading to an overall conclusion that 106 µg L-1 was the ecosystem
NOEC [32].
Industrial effluents from soap manufacturing industries are known to contain complex
chemicals most of which are very toxic and capable of destroying the microbial habitats in a
serious adverse way. For example, characterization of the composite wastewater from both soap
and food processing plants indicated that the waste was highly contaminated with organic
compounds as indicated by COD and BOD values [33].
In a study to assess the seasonal variation in bacterial heavy metal biosorption in a receiving
river as affected by industrial effluents, Kanu et al. [23] observed an overall seasonal variation of
heavy metals such as lead, Zinc and Mn in the rainy season as compared to other metals for dry
season. The concentrations of heavy metals were also, generally low in some samples and no
similar trends were observed in the control samples. Except for iron and zinc, the concentrations
of the other heavy metals were relatively low. Moreover, effluent from the soap manufacturing
plant contained significant concentrations of oil and grease amounting to 563 mg L-1. Soap
manufacturing effluent and the combined wastes discharged from an industrial complex were
subjected to different treatment processes, namely dissolved air flotation, chemical coagulation-
sedimentation, and biological treatment via a completely mixed activated sludge process.
Although coagulation using alum followed by sedimentation removed 52% of COD, residual
values did not comply with the regulatory standards. Biological treatment of the composite
combined wastewater significantly removed the organic contaminants in wastewater. Average
residual BOD, COD, oil and grease values were 30, 92 and 8.3 mg L-1 respectively [34].
Paper mill industry
Process water in paper and board mills contains a lot of sugars and lignocelluloses, which
support the growth of bacteria, mold and some yeast. Effluent from fertilizer plants contain a high
concentration of potentially toxic wastes rich in ammonia-nitrogen, urea, nitrate-nitrogen
orthophosphate-phosphorus which support the growth of algae, yeast and cyanobacteria.
Cellulolytic bacteria such as Klebsiella pneumonia and Enterobacter have been isolated from
spent water from the paper and pulp industries. The occurrence of these microbes in the effluents
lead to excessive oxygen demand loading and also disturb the ecological equilibrium of the
receiving waters with much loss of aquatic life and intense consequences [15].
Textile mill effluent
The textile industry is distinguished by raw material used and this determines the volume of
water required for production as well as waste generated. Heavy metals have been associated
with the textile effluents [35]. The nature of the processing exerts a strong influence on the
potential impacts associated with textile manufacturing operations due to the different
characteristics associated with these effluents (Table 2).

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Table 2 Effluent Characteristics From Textile Industry
Process Effluent composition Nature
Sizing Starch, waxes, carboxymethyl cellulose(CMC),
polyvinyl alcohol(PVA), wetting agents
High in BOD, COD
Desizing Starch, CMC,PVA, fats, waxes, pectins
Bleaching Sodium hypochlorite, Cl2, NaOH, H2O2, acids,
Surfactants, NaSiO2 sodium phosphate
High alkalinity, high SS
Mercerizing Sodium hydroxide, cotton wax High pH, low BOD, high DS
Dyeing Dyestuffs urea, reducing agents, oxidizing
agents, acetic acid, detergents, wetting agents
Strongly coloured, high BOD,
DS, low SS, heavy metals
Printing Pastes, urea, starches, gums, oils, binders,
acids, Thickeners, cross-linkers, reducing
agents, alkali
Highly coloured, high BOD,
oily appearance, SS slightly
alkaline, low BOD.
Brewery industry
Wastewater from Brewery Industry originates from liquors pressed from grains and yeast
recovery and have the characteristic odour of fermented malt and slightly acidic [23].
Brewery effluents are high in carbohydrates; nitrogen and the cleaning and washing
reagents have been proved water pollutants. The introduction of wastewater, high in organic
matter and essential nutrients bring about changes in the microflora. Ekhaise and Anyansi [33]
reported high counts of bacterial population in Ikpoba River in Benin City Nigeria receiving a
brewery industrial effluent. Similar results were reported by Kanu et al, [23] of the effect of
brewery discharge into Eziama River, Aba, Nigeria.
Tannery industrial effluent
The wastewater effluents from tannery industries were studied to determine the chromium
(II) contamination levels.Three aqueous oxidants, hydrogen peroxide, sodium hypochlorite and
calcium hypochlorite were employed independently in oxidizing chromium (III) containing tannery
wastewaters to solubilize chromate (CrO42-) under alkaline conditions. The amount of chromate
recovered was determined via spectrophotometry. Hydrogen peroxide was potentially a suitable
oxidant as it could recover chromate (CrO42-) up to 98% (from synthetic Cr3+ solution) and 88%
(from effluent I). The percentage recoveries by the hypochlorites were lower than with those by
hydrogen peroxide. For example, with NaOCl, the recovery was up to 94% (from synthetic Cr3+
solution) and 67% from effluent I). Similarly, with Ca(OCl)2, recovery was 90% from synthetic Cr3+
solution and 49% from effluent I. For all three oxidants, complete (100%) recovery could not be
achieved despite different experimental conditions (temperatures and oxidation time). The results
clearly indicate that hydrogen peroxide is the most efficient among the three oxidants.
Onwuka et al., [36] studied eighty-eight (88) samples of the groundwater near industrial
effluent discharges in Enugu in order to evaluate its potability. The parameters of interest are
common waste-derivable chemical constituents such as nitrate (NO3-), chloride (Cl-) and sulphate
(SO42-), and indicator microorganisms, like Escherichia coli. The study showed that about twenty-
two percent (22%) of the samples had concentrations of NO3- higher than the WHO permissible
level (45mg/l) while eight out of the ten samples analyzed to test the bacteriological quality of the
groundwater showed evidence of sewage and industrial effluent contaminations. The
identification of E. coli in the water indicates faecal contamination. Improvement in the
management of domestic wastes, such as the use of a central sewer, will preserve the aquifer,
and consequently improve the quality of the groundwater [36].

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Soft drink effluent
Ibekwe et al., (37) analyzed the wastewater in the accumulation pond and final discharge
point of Nigerian Bottling Company PLC in Owerri, Nigeria to determine their bacteriological and
physico-chemical characteristics. Species of organisms isolated included Staphylococcus,
Bacillus, Lactobacillus, and Streptococcus. Others include Klebsiella, Escherichia, Proteus and
Serratia. However, species of Lactobacillus and Proteus were isolated from the final discharge
point only. Bacterial count after 72 hours was higher with a maximum count of 6 x 107 cfu/ml in
the final discharge point. The waste water from both points were clear and had the same residual
chlorine (1ppm) and iron (1ppm) concentration, while the accumulation pond showed more acidity
with a pH of 6.6±1.2. The final discharge contained more dissolved solids (20±1.8ppm) which
was double that of the accumulation pond (10±2.2ppm). It was also found that dissolved oxygen
was slightly higher (6.0±0.26mg/ml) in the final discharge point than accumulation pond
(5.0±0.33mg/ml). Although, these findings were found to be within the permissible limits of
effluent discharge specified by the Federal Ministry of environment in Nigeria[25], the consequent
long-term bioaccumulation effects on microbial ecosystem were not reported.
Chemical industry
The toxicity of benzene, hydroxylbenzene (phenol), chlorobenzene, methylbenzene (toluene)
and dimethylbenzene (xylene) to four chemolithotrophic bacteria (Nitrosomonas, Nitrobacter,
Thiobacillus and Leptothrix isolated from the New Calabar River water were investigated by
Odokuma and Oliwe, [38]. The static method of acute toxicity assessment was employed.
Mortality within a period of 5 hours exposure to toxicant was the index of assessment. Toxicity of
the chemicals to the bacteria decreased in the following order: phenol > xylene > benzene >
chlorobenzene > toluene for Nitrosomonas, chlorobenzene > phenol > benzene > toluene >
xylene for Nitrobacter, phenol > chlorobenzene > benzene > xylene > toluene for Thiobacillus,
while phenol > chlorobenzene > xylene > toluene > benzene was for Leptothrix, The toxicity of
the chemicals to the test organisms decreased in the order phenol > chlorobenzene > benzene >
xylene > toluene. Sensitivity of the bacteria to the test chemicals decreased in the order;
Nitrosomonas > Leptothrix > Thiobacillus > Nitrobacter. Toxicity of the methyl and dimethyl
substituted derivatives of benzene was probably a function of the genetic make up of the bacteria.
The toxicity generally decreased with increased methyl substitution in the case of Nitrobacter and
Thiobacillus, but increased with increased methyl substitution in the case of Nitrosomonas and
Leptothrix. Hydroxyl and halogenated substituted derivatives were more toxic than methyl
substituted derivatives. These results indicate that wastes containing hydroxyl and
chlorosubstituted derivatives of benzene may pose a greater toxicity problem to microbiota than
wastes containing methyl-substituted derivatives. The nitrification stage of the nitrogen cycle will
also be greatly impaired in the presence of these groups of chemicals in a river [38].
Impact of organic wastes
Contributing to the menace of indiscriminate discharges of industrial effluents in receiving
water bodies is the improper disposal of domestic wastes, particularly in urban centres of most
developing countries. Open and indiscriminate dumping of solid wastes in drainages and
riverbanks is one of the most critical problems facing the city of Ibadan [39]. Sewage effluents rich
in decomposable organic matter, is the primary cause of organic pollution. Domestic wastes in
the country like in many other developing countries may now contain modern environmental
health hazardous substances thus posing additional risk to public health [40-42].

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Due to population and industrial growth, inland waters (rivers, lakes, etc.) become often the
recipient of organic matter in amounts exceeding their natural purification capacity, while in the
past, natural purification and dilution were usually sufficient (5).
Secondary organic pollution is defined as the surplus of organic matter, which is the sum of
undecomposed organic material introduced into the water body with primary pollution and of the
material resulting from an extremely increased bioproductivity within the polluted ecosystem itself
[40]. Organic wastes mineralize in the receiving water bodies and the resulting nutritive elements
stimulate plant production, leading to eutrophication. In this situation, the biomass increases
considerably and goes beyond the assimilation limit by herbivores. This secondary organic
pollution is considerably greater than the primary organic load. The excessive production of
organic matter leads to the build up of “sludge” and the mineralization process consumes all
dissolved oxygen from the water column, which causes fish kills[5]. Consequently, organic
pollutants are called oxygen-demanding wastes. The relatively high temperatures in tropical
countries accelerate this process.
Except for a few regions, in Nigeria urban areas do not have any central sewerage system
or sanitary excreta disposal system. The wastewater from most parts of more than 186 urban
centres is carried in open drains into streams and rivers, a characteristic feature of many
developing countries [42]. Nitrogen and phosphorus are the major causes of eutrophication.
Eutrophication affects aesthetics on lakes, rivers and results in odour and appearance problems.
Open drains, carrying various pollutants, contribute to the pollution of streams, since they travel
short distances and consequently offer only limited self-purification of the wastewater.
POME as a source of wastewater
Palm oil mill effluent is an important source of inland water pollution when released without
treatment into local rivers or lakes. In Nigeria palm oil is processed locally and industrially through
the oil palm belt stretching from Cross River to Lagos State. Beside the main product i.e. the
crude palm oil (CPO), the mills also generate many by-products and liquid wastes, which may
have a significant impact on the environment if they are not dealt with properly. Palm oil mill
effluent (POME) is one of the major sources of pollutant produced during oil palm processing.
The palm oil mill effluent (POME) is generated from three major sources, namely sterilizer
condensate, hydrocyclone waste and separator sludge.. On an average 0.9–1.5m3 of POME is
generated for each ton of crude palm oil produced [43]. POME is rich in organic carbon with a
biochemical oxygen demand (BOD) higher than 20 g/L and nitrogen content around 0.2 g/L as
ammonia nitrogen and 0.5 g/L total nitrogen [44] It contains various suspended components
including cell walls, organelles, short fibres, a spectrum of carbohydrates ranging from
hemicellulose to simple sugars, a range of nitrogenous compounds from proteins to amino acids,
free organic acids and an assembly of minor organic and mineral constituents. Also, palm oil mill
wastewater treatment systems are one of the major sources of green house gases due to their
biogas emission (36 % CH4 with a flow rate of 5.4 l/min.m2) from open digester tanks and/or
anaerobic ponds [45]. POME has generally been treated by anaerobic digestion, resulting difficult
to perceive the magnitude of pollution being caused to the receiving waters by such discharges.
The characteristic problems associated with palm oil mill effluents are pH, dark color, high
levels of biochemical oxygen demand (BOD), chemical oxygen demand (COD), color, and
suspended solids. High values of COD also indicate the recalcitrance of chemicals that have
escaped biodegradation. These chemicals may be persistent in nature and may cause severe
environmental problems like bioaccumulation. The POME characteristics shown in Table 2 are
average values and actual values at a mill can be influenced by the quality of the fruits harvested.

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The wastewater is hot and this makes it more difficult to directly treat it aerobically since oxygen
transfer would be less efficient [46].
Table .3. Palm oil mill effluent (POME) characteristics[45]
Parameters Average values
BOD 23,000mg L−1
COD 55,000mg L−1
TN 650mg L−1
TP 120mg L−1
Oil 10,000mg L−1
Volatile fatty acids 1,000mg L−1
pH 4–5
Temperature 45–70oC
Approaches to pollution control
The above review of the effects of industrial effluent pollution on inland waters evidences the
need for control of this type of pollution in developing countries, which can best be achieved by
reduction or prevention at the source. Such measures do lead to raw material recovery and
reduction in effluent discharges or lower treatment costs.
Legal, administrative and technical measures are also necessary to reduce oe eliminate the
undesirable effects of industrial effluents in receiving waters. This can be controlled by standards
imposed by the authorities. Levies can be imposed to cover the cost of off-site treatment and
disposal.
CONCLUSION
The discharge of industrial effluents into receiving water bodies in Nigeria invariably result in
the presence of high concentrations of pollutant in the water and sediment. The pollutants have
been shown to be present in concentrations, which may be toxic to different organisms. The
effluents also have considerable negative effects on the water quality of the receiving water
bodies and as such, they are rendered not good for human use. It is therefore recommended that
the careless disposal of industrial wastes without pretreatment should be discouraged. Imposition
of direct charges on industrial effluents by the regulating agency, as well as continuous
monitoring and surveillance is imperative in order to ensure the protection of water resources
from further degradation.
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