A system and its surrounding are inseparable entities; both exert good and adverse effects on each other. Man as a system cannot be divorced from its surrounding (environment).
The quest of man to exploit his environment to his desired sophisticated standard of living has made him to continuously withdraw and add to his environment. This anthropogenic phenomenon has resulted in the environment deteriorating vastly everyday. The effect is hazardous to mans health and this is becoming a thing of a great concern for man.
The federal government of Nigeria through its agency made it mandatory that effluents be treated to acceptable standards and returned to the watercourse from where the water was originally obtained. Effluent discharge investigation is one of the water quality management tools adopted by Federal Environmental Protection Agency (FEPA) now Ministry of Environment for the management of point-source effluent.
Low pH could be expected from a battery factory wastewater since one of the major raw materials is tetraoxosulphate (IV) acid (H2SO4). Low pH values in a river adversely affect aquatic life and impair recreational uses of water (DWAF, 1996a). A change in pH from that normally encountered in unimpaired stream affects the biota (DWAF, 1996a). High pH values could also alter toxicity of water pollutants in the water body. A decrease in pH could also decrease the solubility of certain essential elements. Low pH also increases the solubility many other elements such as Al, B, Cu, Cd, Hg, Mn and Fe (DWAF, 1996a).
Conductivity of water is used as a measure of the total concentration of ionic species or salt content. Wastewater effluents often contain high amounts of dissolved salts. Sources of dissolved salts include windblown sea salt, municipal storm, water drainage and industrial effluent discharges (Morrison et al., 2001). Salts such as NaCl and K2SO4 pass through conventional water and wastewater treatment plants unaffected (Hammer, 1975). High salt concentrations in waste effluents can increase the salinity of the receiving water, which may result in adverse ecological effects on aquatic biota (Fried, 1991).
The advantage of the BOD parameter is that it is supposed to reflect the presence of materials, which will be oxidized biologically in the receiving water. BOD can be taken as a measure of the concentration of organic matter present in that kind of water (Ademoroti, 1986). The greater the decomposable matter present the greater the oxygen demand and the greater the BOD value. Continuous discharge of the effluent with high BOD into the river may have negative effects on the quality of the fresh water and can as well cause harm to the aquatic life especially fish down streams (Morrison et al., 2001).
The accumulation of metals in an aquatic environment has direct consequences to man and to the ecosystem. Some metals like Zn and Cu are needed for metabolism in organisms. Interest in such metals lies in the thin line between their toxicity and essentiality (Spear, 1981). Some metals (e.g., Al, Cd and Pd) are extremely toxic even at trace levels (Merian, 1991).
Cadmium has been found to be toxic to man, fish and other aquatic organisms
(Woodworth and Pascoe, 1982). Cadmium has been reported to induce kidney damage
in man (Herber et al., 1988). It is carcinogenic, mutagenic and causes
pains in bones (Kjellstroem, 1986; Fischer, 1987; Kazantzis, 1987; Heinrich,
Copper has been reported to be toxic at very low concentration in water and induces brain damage in mammals (DWAF, 1996a).
Lead is a suspected pollutant in a battery factory effluent because is also a major raw material in the manufacture of lead acid accumulated batteries. Lead at very low concentrations is toxic and hazardous to most forms of life (USEPA, 1986). The chronic effect of Pb on man includes neurological disorders, especially in the foetus and in children. This can lead to behavioral changes and impaired performance in IQ tests (Lansdown, 1986; Needleman, 1987). Though Zinc has low toxicity to man, it has relatively high toxicity to fish (Alabaster and Lloyd, 1980).
The presence of Mn and Fe in water affects aesthetic value of such water because of the colour (Fatoki et al., 2002).
The objective of this study is to investigate possible impact of pollution from a battery factory wastewater on ambient environment using physico-chemical parameters-pH, temperature, conductivity, Biochemical Oxygen Demand (BOD) and trace elements as indicators of pollution.
MATERIALS AND METHODS
Wastewater samples were collected from a battery manufacturing factory in southwestern Nigeria. Samples were collected from two points; settling tank and final discharge point. Samples for BOD analysis were collected in BOD bottles and equivalent size white bottles. Wastewater samples for pH, conductivity were collected in 1-litre polyethylene plastic bottles. Samples for trace metal analysis were collected in 100 mL polyethylene plastic bottles. The samples were tightly sealed and kept in the refrigerator before analysis. Three samplings were done for a period of nine months at intervals of three months.
The temperature of wastewater was determined in situ using thermometer. The
pH of wastewater was measured with a Griffin model 40 pH meter; the pH meter
was standardized before use. BOD values were determined by titrimetric method
using standard method. Initial 2% dilution of the wastewater was done prior
to incubation. The period of incubation of the BOD tests was 5 days. A Hanna
HI 8333 conductivity meter was used to measure the conductivity values of samples.
The instrument was calibrated with 0.001 M KCl at 25°C. Trace metals analysis
was done using atomic absorption spectrophotometer. The data of the analysis
were retrieved from Gateway PC 2000 system using appropriate software.
RESULTS AND DISCUSSION
The results of the effluent analyses for first sampling (Table 1) showed that pH values range from 2.18 to 2.65 at the settling tank and 1.68 to 2.25 at the final discharge point. Temperature maintains a constant value of 26°C at the settling tank and 26.5°C at the final discharge point. Conductivity varies from 200 to 1200 μS m-1 and 1020 to 4500 μS m-1 at the settling tank and at the final discharge point, respectively. BOD value of 5.96 mg L-1 was obtained at the settling tank while 3.40 mg L-1 was obtained at the final discharge point. The values of Pb, Fe and Zn range from 2.17-5.32, 0.044-0.68 ppm and 0.18-7.27 ppm, respectively at the settling tank and 1.89-4.11, 0.028-11.52 and 0.12-4.85 ppm, respectively at the final discharge point. Concentrations of Mn, Cu and Cd were very low both the settling tank and the final discharge point.
The results of the effluent analyses for second sampling (Table 2) revealed that pH values vary from 3.15-3.75 and 2.20-2.65 at the settling tank and the final discharge point, respectively. Temperature values range from 25.8-26.5°C at the settling tank and 24.00-26.5°C at the final discharge point. Conductivity ranges from 230-448 μS m-1, 1000-2900 μS m-1 at the settling tank and the final discharge point, respectively. BOD values of 16.2 and 11.2 mg L-1 were obtained at the settling tank and the final discharge point, respectively. The values of Pb, Fe and Zn vary from 5.38-6.82, 0.36-2.17, 0.037-0.107 ppm, respectively at the settling tank and 1.72-2.52, 1.96-11.3, 0.083-0.138 ppm, respectively at the final discharge point. Concentrations of Mn, Cu and Cd were very low at both settling tank and final discharge point.
The results of effluent analyses for the third sampling (Table 3) showed that pH values range from 2.75-3.25, 2.62-2.86 at the settling tank and the final discharge point, respectively. Temperature values vary from 2.80-29.00°C, 26.00-28.8°C at the settling tank and the final discharge point, respectively. Conductivity values vary from 250-500 μS m-1 at the settling tank and 1350-3500 μS m-1 at the final discharge point. BOD values of 57.2 and 99.0 mg L-1 were obtained at the settling tank and the final discharge point. Pb, Fe, Zn and Mn concentrations range from 1.94-2.95, 0.20-1.73, 0.14-4.64, 0.13-0.402 ppm, respectively at the settling tank and 1.79-3.62, 2.72-3.15, 0.065-0.106, 0.55-0.111 ppm, respectively at the final discharge point. Concentrations of Cu and Cd were still very low.
|| Effluent analyses for the first sampling data
|| Effluent analyses for the second sampling data
|| Effluent analyses for the third sampling data
|| Summary of the battery factory wastewater analyses
The averaged pH values at the settling tank and at the final discharge point
(Table 4) indicate that the effluents are highly acidic, with
their pH values being much below the FEPA limit of 6-9 for battery factory effluents.
Since pH is a function of hydrogen ion concentration (i.e., pH = -log [H+]).
The high acidity was probably due to the high concentration of hydrogen ion
[H+] in the effluent, sourced mainly by Sulphuric acid-one of the
major raw materials in lead acid battery manufacture. The aquatic life in the
receiving stream will be adversely affected at low pH. Figure
1 is the histogram of parameters analyzed for in the first sampling.
|| Histogram representation of the analytes in first sampling
|| Histogram representation of the analytes in second sampling
|| Histogram representation of the analytes in third sampling
It revealed that averaged pH value at settling tank is higher than at final
discharge point. The results of second and third samplings (Fig.
2 and 3) have the same trend. This suggests that the treatment
plant is not effective for reduction of acidity of the effluent.
The averaged temperature values of the effluents at the settling tank and at the final discharge point (Table 4) are less than FEPA limit of 40°C.
The averaged conductivity values at the settling tank and at the final discharge
point are high. Though, there is no FEPA specified guideline for conductivity
value, the South African guideline for conductivity in effluent that will be
discharged into the river is 250 μS m-1. The effluent conductivity
values are above this acceptable limit. Conductivity of water is an easy indicator
of its salinity or total salt content (Morrison et al., 2001). The high
conductivity values (i.e., high salt concentrations) in the effluents can increase
the salinity of the receiving river, which may result in adverse ecological
effects on the aquatic biota. Such high salt concentrations hold potential health
hazard (WHO, 1979). There is a slight reduction of conductivity values (Fig.
4-9) at both settling tank and final discharge point.
||Relative abundance of the analytes at settling tank in first
||Relative abundance of the analytes at final discharge point
in first sampling
||Relative abundance of the analytes at settling tank in second
This indicates that the treatment plant is not efficient for significant removal
of total salt content.
There was a progressive increase in the BOD values (Table 1-3,
Fig. 1-3) from first sampling through the
||Relative abundance of the analytes at final discharge point
in second sampling
||Relative abundance of the analytes at settling tank in third
||Relative abundance of the analytes at final discharge point
in third sampling
Though, the averaged values at the settling tank and at the final discharge
point are below FEPA limit of 50 mg L-1 for industrial effluents,
it is still considered high and hazardous for survival of the aquatic biota
in the receiving stream (Alloway and Ayres, 1993). The BOD values at the third
sampling were ten (10) times higher than the values in the first sampling. This
indicates that biodegradable substances in the effluent have increased considerably.
The histogram representations (Fig. 1-3)
of the analytes in the wastewater samples indicate that there is a reduction
of biodegradable substances from settling tank to final discharge point in the
first and second samplings. It was vice versa in the third sampling. It is quite
coincidental that the treatment plant became inefficient for the removal of
biodegradable substances when the load of these substances suddenly increased
The averaged lead levels in the effluent at the settling tank and at the final discharge point (Table 4) are above FEPA limit of 0.01 mg L-1. At levels greater than 100 μg L-1, possible neurological damage in foetus and young children may occur (DWAF, 1996b). These levels were exceeded in the effluent; direct use of water from the receiving river for domestic purposes without treatment could be detrimental to young children in the vicinity of the catchments. The receiving river also would not be suitable for maintenance of the aquatic ecosystem (Fatoki et al., 2002).
Concentrations of Fe at the settling tank and at the final discharge point exceeded FEPA limit for Fe of 0.02 mg L-1 in industrial effluent. This implies that the receiving river may have taste, colour and other aesthetic problems (DWAF, 1996a; Fatoki et al., 2002).
The averaged levels of Zn at the settling tank and at the final discharge point (Table 4) exceeded specified South African limit for Zn in water for aquatic ecosystem of 2 μg L-1. Thus, the receiving river will not be suitable for the maintenance of the aquatic ecosystem.
There is no FEPA specified limit for Mn in industrial effluent. The averaged values of Mn at the settling tank and at the final discharge point exceeded the South Africa guideline for Mn 0.05 mg L-1 in water for domestic use (DWAF, 1996a).
The concentrations of Cu at the settling tank and at the final discharge point are low (Table 4). This shows that the treatment process is effective for the removal of Cu.
The levels of Cd at the settling tank and at the final discharge point are low (Table 4). The shows that the treatment plant is also effective for the removal of Cd.
The concentrations of the metals except Fe were more at settling tank than at final discharge point (Fig. 1-3) for the first and second samplings. This indicates that the treatment plant was slightly effective for the removal of these metals up to the time of the second sampling. At the third sampling the efficiency of the treatment plant for the removal of Pb, Fe and Mn has reduced to near zero, but was still efficient for the removal of Zn, Cu and Cu.
Temperature, Mn, Cu and Cd levels were below guideline values. However, high
levels were observed for Pb, Fe and Zn, which may be hazardous to the health
of the receiving aquatic ecosystem. The high levels of Pb and Zn may have adverse
effects on the health of the community in the vicinity of the receiving river
that uses the river water directly for domestic use without treatment. The treatment
technique employed in the factory is not effective for pH, conductivity, Pb,
Fe and Zn. The treatment plant needs to be overhauled and upgraded to improve
its treatment performance.
Battery factory effluents pose environmental risk if not properly treated before discharge to the receiving stream.