Bacteriological and physicochemical analyses of the raw and treated water of a university water treatment plant, Zaria-Nigeria.
Water and sanitation condition is generally poor in developing countries including Nigeria. Although Nigeria is known to be endowed with abundant water resources, the availability of potable water is a problem in many parts of the country (1). The Nigerian Government has long considered the provision of water supply services to be the domain of the Federal, State and Local Governments. The public sector on the other hand has not been successful in meeting more than a small portion of the demand for water of residential and commercial users and thus water services are in critically short supply (2). Drinking water quality has always been a major issue in many countries, especially in developing countries (3). The World Health Organization in its "Guidelines for drinking water quality" publication highlighted at least seventeen different major genus of bacteria that may be found in tap water which are capable of seriously affecting human health (4). The proportion of waterborne disease outbreaks associated with water distribution system failures has been increasing over the years (5).
Ahmadu Bello University Water Treatment Plant (ABUWTP) is a surface water treatment plant. The kubanni dam is the source of the raw water for the plant. Different treatment processes like prechlorination, coagulation, filtration and disinfection are used at ABUWTP. ABUWTP supply potable water to over 70,000 residents (staff and students) within the University main campus in Zaria with an average 1,840,000,000 liters of potable water per day.
The quality of water is defined in terms of its physical, chemical and biological parameters, and ascertaining its quality is important before use for various intended purposes such as potable, agricultural, recreational and industrial water usages (6). A supply of clean water is an essential requirement for the establishment and maintenance of a healthy community (7). Safe drinking water has been one of the greatest achievements of developed countries and an important milestone that developing countries are trying to achieve (8). One way to achieve this is through regular monitoring of water sources. Thus the aims of the present investigation were to assess the bacteriological and physicochemical parameters of the raw as well as treated water of ABUWTP to determine its potability.
Materials and Methods
The study was conducted during the period of 6 weeks (mid September through October) in the rainy season of 2009. Water samples, from inlet point (raw water from Kubanni dam) and outlet point (treated water) of ABUWTP, Samaru-Zaria, were collected in sterile glass bottles for weekly bacteriological and physicochemical analyses. Samples, kept at 4[degrees]C, were analysed within few hours. They were divided into two parts. One part was used for immediate bacteriological analyses, and the second part was used for physicochemical analyses.
Bacteriological examination of the water sample carried out includes Most Probable Number (MPN) of presumptive coliforms (MPN/100 ml water) using the Multiple Tube Fermentation Technique (4, 9). Suspected colonies of coliform groups were also identified on the basis of morphological, cultural and biochemical characteristics (10, 11)
Water temperature was determined with a mercury thermometer, pH and electrical conductivity by using conventional meters (12). TDS was analyzed following standard methods (9). P[O.sub.4]-P and N[O.sub.3]-N using spectrophotometer while DO, BOD, total hardness, total alkalinity and chloride were evaluated by burette titration.
Results and Discussion
Figure 1 depicts weekly variations of fecal coliforms of the raw and treated water of Ahmadu Bello University Water Treatment Plant (ABUWTP) during the period of investigation. The fecal coliforms isolated from the water samples were identified as E.coli, Entrobacter sp and Klebsiella sp. A high population and number of species of fecal coliforms encountered during at the commencement of investigation, diminished at the 6th week when the rains ceased. The source of the raw water of ABUWTP was the Kubaani dam that receives domestic sewage as well as agricultural effluents from the adjacent arrears of Samaru town and the University community. Coliforms were detected in both the raw and treated water over the study period, though higher densities were encountered in the raw water than in the treated water. This indicates that the treatment system of ABUWTP was not completely effective in removal of harmful water-borne pathogens. The mean values of total coliforms for the raw and treated waters were 845 [+ or -] 410.15 cfu/100ml and 19.33 [+ or -] 4.22 cfu/100ml respectively (Table 1). The presence of total coliforms and fecal colifroms in both raw and treated waters has also been reported (4, 5,13). To simplify the interpretation of the high coliform counts measured in open wells of developing countries, (3), proposed a division into three categories corresponding to the relative quality of the water: >100 fecal coliforms/100ml should be considered satisfactory; between 100 and 1000 col./100ml suggests a strong contamination and risks to health; and above 1000 col./100ml, the water should be considered seriously pathogenic.
[FIGURE 1 OMITTED]
Physicochemical factors are very important aspects of potable of water. Certain range of these factors enhances the bacterial growth and also determines the sanitary quality of water (13). Statistical summary of variation in physicochemical factors of raw and treated water of ABUWTP is summarized in Table 1. Temperature fluctuated between 24.26 to 29.00[degrees]C for raw water and 26.63 to 29.00[degrees]C for treated water respectively. Temperature and pH are essentially important for some of the reactions that take place in water (7). An ideal temperature ([less than or equal to] 25[degrees]C) is essential to maintain the rate of disinfection during water treatment and also to prevent the toxicity of probable metals that may be found in the water (14). Similarly,an ideal basic pH of 6-9 in the water is essential for chemical reactions e.g., coagulation (7). Although, on the average, pH values were within the recommended limits for water treatment processes, values outside the recommended limits were recorded during this study; values below 6 for pH and above 25[degrees]C for temperature (Table 1). The electrical conductivity of both treated and raw waters of ABUWTP ranges from 52.68 [+ or -] 14.71 to 70.06 [+ or -] 3.87 [micro]S/cm respectively. The TDS trend closely follows the fluctuations of electrical conductivity. The variation in the TDS is an indication of the varying contributions of allochthonous and autochthonous inputs to the dam. However, both TDS and EC are below the WHO (4) guideline value for TDS in drinking water of 1000mg/L (electrical conductivity of about 1400.00[micro]S/cm). Thus, with respect to electrical conductivity, the dam water and the treated water are both portable.
The mean total hardness values for raw and treated waters are 48.50 [+ or -] 8.91 and 35.00 [+ or -] 8.34 mg/LCaC[O.sub.3] respectively. Total hardness is an indicator for the presence of health-related chemical characteristics (7). This may reflect the potential for water to cause corrosion as both very soft and very hard water can interact with piping materials (4). The hardness of both raw and treated water conforms to the Nigerian Standard (200-500 mg/L as CaC[O.sub.3]). According to Lind (12), the expected total alkalinity in natural water usually ranges from 20.00 to 200.00mg/LCaC[O.sub.3]. Alkalinity is not a pollutant but it is a total measure of the substances in water that have "acid-neutralizing" ability (9). Thus the raw water with an alkalinity of 51.85 [+ or -] 9.01mg/LCaC[O.sub.3] has a higher acid-neutralizing ability than the treated water which had and alkalinity of 28.31 [+ or -] 21.9 mg/LCaC[O.sub.3].
A high DO level in a community water supply is good because it makes drinking water taste better. However, high DO levels speed up corrosion in water pipes (9). Water used in very low pressure boilers have no more than 2.0mg/L. Thus the mean DO values obtained for raw (5.97mg/L) and treated (7.71mg/L) waters are within the optimum for drinking waters. Depletion of dissolved oxygen in water supplies can encourage the microbial reduction of nitrate to nitrite and sulphate to sulphide, giving rise to odour problems (6,8). Based on BOD classification of waters: unpolluted [BOD < 1.0mg/L], moderately polluted [BOD between 2-9 mg/L] and heavily polluted [BOD>10.0mg/L]( modified from 15 and 16). The raw and treated waters with mean BOD values of 1.64 [+ or -] 1.04 and 0.89 [+ or -] 0.72 mg/L could be regarded as unpolluted and moderately polluted respectively.
Correlation coefficient between BOD and P[O.sub.4]-P was positively significant (P <0.05) while that between P[O.sub.4]-P and N[O.sub.3]-N was also positive but highly significant (P < 0.01). Phosphates and nitrates are important parameters to assess water quality (6). These nutrients were relatively higher in raw water than in treated water (Table 1). Both the mean P[O.sub.4]-P obtained for raw water (0.90 [+ or -] 0.13 mg/L) and treated water (0.58 [+ or -] 0.08 mg/L) during this investigation were higher than the drinking water limit (0.2mg/L) set by Canada (11). However, the N[O.sub.3]-N means for both raw and treated waters (Table 1) were below the standard of 10.00mg/L N[O.sub.3]-N (45.00mg/L N[O.sub.3]-) for drinking water. The chloride value obtained ranged between 46.2 - 48.80 mg/L and 38.95 - 41.10 mg/L for raw and treated waters respectively. However, these ranges were below the permissible criteria (250.00mg/L) for raw water (4).
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* J.A. Adakole and I.O. Jonah
Department of Biological Sciences, Ahmadu Bello University, Zaria, Nigeria
* Corresponding Author
Table 1: Summary of raw and treated water characteristics of ABUWTP Parameter Raw water Min Max Mean [+ or -] SD Temperature ([degrees]C) 24.3 29 27.57 [+ or -] 1.85 pH 5.68 7.52 6.87 [+ or -] 0.86 TDS (mg/L) 32.2 37.7 27.73 [+ or -] 15.64 Elect conductivity 64.3 75.3 70.06 [+ or -] 3.87 ([micro]S/cm) Tot hardness 35 57 48.50 [+ or -] 8.91 (mg/LCaCO3) Tot alkalinity 34.3 60.4 51.85 [+ or -] 9.01 (mg/LCaCO3) Dissolved oxygen 5.06 7.03 5.97 [+ or -] 0.78 (mg/L) B.O.D (mg/L) 0.93 3.55 1.64 [+ or -] 0.99 PO4-P (mg/L) 0.8 1.12 0.9 [+ or -] 0.13 NO3-N (mg/L) 4.6 7.2 6.13 [+ or -] 0.96 Chloride (mg/L) 46.2 48.8 47.88 [+ or -] 1.3 Tot coliforms(MPN 500 1600 845 [+ or -] 410.15 index/100ml) Escherichia coli 20 30 24.5 [+ or -] 3.88 (cfu/100ml) Enterobacter sp 10 14 11.66 [+ or -] 1.36 (cfu/100ml) Klebsiella sp 10 18 13.88 [+ or -] 2.92 (cfu/100ml) Parameter Treated water Min Max Mean [+ or -] SD Temperature ([degrees]C) 26.63 29 27.33 [+ or -] 0.87 pH 5.45 7.19 6.33 [+ or -] 0.69 TDS (mg/L) 27 33.67 29.04 [+ or -] 0.93 Elect conductivity 28 67.23 52.68 [+ or -] 14.71 ([micro]S/cm) Tot hardness 29 39 35.00 [+ or -] 8.34 (mg/LCaCO3) Tot alkalinity 18.7 73 28.31 [+ or -] 21.9 (mg/LCaCO3) Dissolved oxygen 5.9 9.13 7.71 [+ or -] 1.05 (mg/L) B.O.D (mg/L) 0.27 1.98 0.89 [+ or -] 0.72 PO4-P (mg/L) 0.48 0.68 0.58 [+ or -] 0.08 NO3-N (mg/L) 3 6.2 4.23 [+ or -] 1.89 Chloride (mg/L) 38.95 41.1 40.50 [+ or -] 0.86 Tot coliforms(MPN 14 26 19.33 [+ or -] 4.22 index/100ml) Escherichia coli 2 6 3.5 [+ or -] 1.64 (cfu/100ml) Enterobacter sp 0 4 1.5 [+ or -] 1.76 (cfu/100ml) Klebsiella sp 0 4 2.16 [+ or -] 1.32 (cfu/100ml) Parameter Highest Maximum desirable desirable Temperature ([degrees]C) -- -- pH 7-8.5 6.5-9.2 TDS (mg/L) 500 1500 Elect conductivity ([micro]S/cm) Tot hardness 100 500 (mg/LCaCO3) Tot alkalinity -- -- (mg/LCaCO3) Dissolved oxygen -- -- (mg/L) B.O.D (mg/L) -- -- PO4-P (mg/L) -- -- NO3-N (mg/L) 10 12 Chloride (mg/L) 200 600 Tot coliforms(MPN 0/100ml 0/100ml index/100ml) Escherichia coli 0/100ml 0/100ml (cfu/100ml) Enterobacter sp 0/100ml 0/100ml (cfu/100ml) Klebsiella sp 0/100ml 0/100ml (cfu/100ml)