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Introduction

Rivers have been used by man since the dawn of civilization as a source of water, for food, for transport, as a defensive barrier, as a source of power to drive machinery, and as a means of disposing of waste. Rivers water finds multiple uses in every sector of development like agricultural, industry, transportation, aquaculture, public water supply etc. The growing problem of degradation of our river ecosystem has necessitated the monitoring of water quality of various rivers all over the country to evaluate their production capacity, utility potential and to plan restorative measures.(Dataret al.,1992, Daset al.,1993) The Ganga River is one of the most sacred river in India is being polluted by many sources. The main sources of pollution of river Ganga at Varanasi are industrial effluents, domestic sewage and cremation of dead bodies (Tripathiet al.,1986). At Varanasi 190 MLD of domesticsewage and 80 MLD untreated sewage and industrial effluent along with excreta by human being and various warm blooded animal are directly or indirectly discharged into the river ganga which have adversely affects the physicochemical and biological quality of river. Approximately 60,000 human dead bodies and about 15,000 incomplete burnt dead human and animal bodies annually dumped in the river. In addition to this variety of other human activities also contributes significantly increase the bacterial concentration in the river. Many of these bacteria are pathogenic and spread the disease like typhoid, paratyphoid, gastroenteritis. Surface waters may play an important role in the transmission of pathogenic agents discharged through feces.

Prevention of river pollution requires effective monitoring of physicochemical and microbiological parameters (Bonde, 1977, Ramtekeet al.,1994). DO and BOD is used to state thepollution status of aquatic system. Nevertheless, the concentration of DO in water always is a reliable factor to indicate the pollution state of aquatic system (Voznaya, 1983). Redox potential (E_h) and Oxidation Reduction Index (rH₂) is one of the important indicators of pollution state of river. Redox potential is considerably influenced by the ambient temperature and hydrogen ion concentration. A positive E_hvalue results from a state tending towards oxidation, while a negative E_hindicates a system causing reduction (Sinha, 1995). The E_hconsidered as useful physical parameters that governs several microbial processes (Lynchet al.,1988). Water with an E_hlower than the0.1 to 0.2 V is generally called reducing (Mortimer, 1942). In natural water and mud, the apparent potential difference is usually between -0.1V (oxygen free) and +0.5V (oxygen saturated). Water saturated with oxygen should have a value of about 0.8V. (Golterman,et al .,1978) The oxidation-reduction index (rH₂) used to assess the pollution status in aquatic system. Negative correlation between the rH₂and the BOD (Gautamet al.,1989) showed the higher pollution state in the river.

Oxidation-reduction index (rH₂) is calculated by computing the E_hand pH of the water bodies following the equation

rH₂= E_h/0.029 + 2pH

The neutral point of rH₂is assumed 28.00(Voznaya, 1983). Low than 28.00 indicate a pollution state. In aquatic body, low values of E_h和rH₂values increase the growth and multiplication of aerobic microorganism. Detection and enumeration of indicator organism are of primary importance for the monitoring of sanitary and microbiological quality of water (Gunnison, 1999: Katariaet al.,1997).

Table 1: Variation in different physicochemical characteristics in different seasons Click here to view table

The bacterial growth also regulated by physico-chemical quality of water. The elevated turbidities are often associated with the possibility of microbiological contamination as high turbidity makes it difficult to disinfect water properly (Van Loon, 1982; Quality of Domestic Water Supplies, 1998). Coliforms are the major microbial indicator of monitoring water quality (Brenner et al, 1993, Grant, 1997). Total Coliform (TC) and fecal coliform (FC) counts are the most widely used bacteriological procedures for assessment of the quality of drinking and surface waters (Mcdaniels. et al, 1985).The TC bacteria test is a primary indicator of potability, suitability for consumption of drinking water. It measures the concentration of TC bacteria associated with the possible presence of disease causing organisms(Craun,1978) FC are selected members of the coli form group of bacteria are fairly specific for the feces of warm blooded animals and are commonly used as indicators of feacal pollution in waters such as waste water effluents, rivers and raw sources of drinking water supplies (Geldraich,1978) Variety of human activities contributes significantly to raising the bacterial concentration in the river. Many of these bacteria are pathogenic and agents of diseases like typhoid, paratyphoid, gastroenteritis, dysentery, diarrhea, etc (LeChevellier and Mc Feters, 1985, Kumar, 1992). In the present study, an attempt has been made to assess the impact of seasonal changes on concentration of pathogenic and nonpathogenic bacteria and impact of the different pollutants discharged into river water, as well as to explore the relative pollution states of the river Ganga.

Material and Methods

Sampling Area

Study area covered in the urban fringe area of Varanasi city, situated in the Eastern Gangetic plain (82° 15’E to 84° 30’E and 24° 35 ’N to 25° 30’N) of Northern India. Total five sites, namely Raj Ghat (site1), Assi ghat (site2), Harischandra Ghat (site3), Shiwala Ghat (site4) and Samne Ghat ( site5) were selected for river quality monitoring. Each site was reasonably representing the water quality of the river system. The first site is most polluted and receives much of the sewage of the town. Site 2, 3, and 4 are fall in midstream region. Site 5 is located in the area of relatively low river pollution and upstream of the Varanasi city.

Sampling

Water samples were collected in Jan, March, May, July, Sept, Nov across in the river width at all the 5 sites with a view to monitor changes caused by anthropogenic sources. Sampling, preservation and transportation of the water samples to the laboratory were as per standard methods (APHA, 1998). All samples were transported in cold packs to the laboratory and were analyzed within 7h of collection. The pH was determined by a portable pH meter at a collection site immediately after sampling since the biological and chemical reactions between the atmosphere and the sample could readily alter the pH (Hutton, 1983). The E_hwas determined through the following equation.

嗯= E₀–0.058 pH + 0.0145 logp_o2 where E₀is the standard electrode potential and a function of pH; PO2 is the partial pressure of the oxygen dissolved in water (Voznaya, 1983).

Table 2: Average monthly and seasonally variation in different bacterial parameters at different sampling sites at Varanasi Click here to view table

Enumerations and Isolation of Bacterial Species

细菌分析样本中收集的年代terile bottles at each site and were kept cold ice packed cooler boxes in the field where, possible, being returned to laboratory for analysis as soon as possible. In bacterial analysis, Hi media were used. Qualitative analysis was carried by multiple tube fermentation technique (APHA, 1998) for members of the coliform group. Coliform were detected by presumptive inoculation into tubes of MacConkey broth and their incubation at 37±2⁰C for 48h Gram characters were also observed by gram staining. MPN of coliform were found in terms of index/100 ml by using standards tubes. For confirmation of indicator bacterial species other test tubes like IMVic, fermentation, VP, nitrate, reductase, oxidase, catalase, citrate, H₂S tests etc were performed by using specific media and indicators( Sirockin and Cullimore, 1969, WHO 1985, APHA, 1998).

Results and Discussion

理化分析的进行different site during different season has been presented in Table 1. Temperature is the most important factor, which influences chemical, physical and biological characteristics of water bodies. A study revealed that temperature varied from 20.3 to 27.6 where maximum at Site 1 and minimum at Site 5. Similar pattern were observed for Electric Conductivity. The pH values did not show remarkable differences between sampling sites and ranged 7.1 to 8.3. The value of DO is remarkable in determine the water quality criteria of an aquatic system. In the system where the rates of respiration and organic decomposition are high, the DO values usually remain lower than those of the system, where the rate of photosynthesis is high. The mean value of the dissolved oxygen ranged between 1.8 to 5.9 mg/L. Highest DO at the Site 5 where minimum discharge of effluent and human activities. Lowest DO at the Site 1 where maximum discharge of sewage effluent from the town. In opposite BOD is minimum at Site 5 and maximum at Site 1 followed by Site 2, 4 and 3. The nitrate concentration were high ranging from 1.0 to 2.6 mg/L. Highest mean concentration were observed at sampling Site 1 and Site2 ( 2.6 and 1.58 mg/L respectively). Plotting the monthly values of nitrate concentration verses time, maxima at the end of winter and during the summer are obtained (Vega et al, 1998). The highest concentration was probably partially a result of rainfall, washing out nitrate from fertilizers. Same pattern were also observed for phosphate. PO₄values in river Ganga ranged between 3.56 to 5.79mg/L where maximum value in sampling site 1 followed by Site2 and 4. Average concentration of PO4 is 3.9, which is considered as the lower limit for river waters to pose a risk of Eutrophication (Mourkidas etal, 1990). Table 1 showed the value of Eh and rH2 at different Sites. In natural water might have a range from -0.1 V (oxygen free) to + 0.8V (oxygen saturated). The neutral point of Eh in natural water might be taken as +0.35V [0.5(0.8V-0.1V)] the value below this would indicate a pollution state. Present study revealed that Ganga water in a reducing state (Eh always remained above +0.2V). The rH2 is an objective characteristic of the process occurring in a given body of water (Voznaya, 1983). At almost Site values of rH2 in river Ganga, have lower than 28, which point the pollution in river. The addition of organic matter in it increased the concentration of the reduced from and lowered the ambient Eh and rH2 values. Bacteria are the chief decomposer and indicator of organic pollution. Table2. Showed the bacterial concentration (TBD, FC, EC, TC, and CP) at different Sites and season. Total bacterial density (TBD) where maximum at Site 1. Bacterial population had affected by seasonal variations. Maximum concentration of (TBD, TC, FC, EC, and CP) was found in July due to favorable temperature, high turbidity and addition of more sewage and feacal matter through surface runoff. Low bacterial concentration during January because of lowest water temperature and comparatively low input of organic matter. The irregular variation in the coliform bacteria due to seasonal change also corroborated the finding of (Legendraet al., 1984, Barcina, 1986 and Ramanibai, 1996).

Table 3: Bacterial Species isolated from Ganga Water at Varanasi Click here to view table

Total bacterial count can be a reliable indicator of water quality since the number of bacteria present depends upon the degree of contamination (Bilgrammi, 1998). The quantitative values of bacteria were invariable highest at Site 1 followed by 2, 4, 3 and 5 due to the discharge of sewage along with human and animal excreta and hospital refuge, open defecation near bank, allowing of cattle and other human activities. Bacterial population concentration has been noted to be directly related with the outbreaks of water borne diseases (Muller et al, 1977).

Coliform bacteria are reliable indicator of organic pollution because they are unable to survive in clean water beyond a limited time (Rai and Hill 1978, Hiraishiet al.,1987) Table 2 showed the different concentration range of coliform, FC, E.coli and CP at different months. FC group is supposed to be more reliable indicator of feacal pollution of water than E. coli (Kennar, 1978) because they areunable to multiply outside the body of human and other warm blooded animals(Mathur and Ramanathan 1966) and also because their survival is more prolonged in surface water than other coliform types (WHO, 1991). Clostridium perfringens is an important bacterial species, which sporulate in nature and survive in water for a comparatively longer period as compared to other feacal bacteria. Their presence in river water is an indicator of feacal contamination of remote time (Droop and Jannash, 1977, Sinha and Banerjee, 1987). Table 3. Showed the qualitatively 11 bacterial species were identified from the Ganga River at Varanasi. Maximum bacterial species were prominent in rainy season because organic matters enhance the bacterial growth and multiplication.E.coli是普遍的在每一个季节。存在of other members of FC group (Klebesiella, Enterobacter) has been reported for the nonfeacal origin (Alonso et al, 1998). Presence of pathogenic bacteria like Actinomyces, Proteus vulgaris, Pseudomonas aerogenosa, Salmonella typhi, S. paratyphi, Staphylococcus in water may cause acute to severe disease on getting suitable host and condition.

Conclusion

The river Ganga which is holiest river of India is frequently used for different purposes. Present study revealed the high level of bacterial population and E_h和rH₂indicate pollution state of river Ganga. The concentration of different physico chemical and bacterial parameters is much beyond the permissible limit prescribed by WHO. Hence, direct consumption of untreated Ganga water and bathing in the Varanasi reason is at high risk for human health

References