Assessment of microbiological and physico-chemical characterıstics of water samples in households of Bangalore city, Karnataka, India

Access to safe drinking water is one of the basic human rights and is essential to human health. The present study investigated the concentration of pathogenic microbial flora and health risk in drinking water samples in households of Bangalore city, Karnataka, India. The samples were analysed for microbiological and physico-chemical parameters. In this study, most probable number and heterotrophic plate count were used to assess the microbial load. The results of the study show that most of the household water samples were contaminated with the presence of coliform bacteria. The dominant bacterial species are Escherichia coli, Salmonella, Shigella, Klebsiella and Enterobacter. The bacteria belonging to the family Enterobacteriaceae showed maximum occurrence in water samples. The overall results of the study showed that the consumption of such contaminated drinking water at the end-user point may cause potential health hazards to the inhabitants.

health of citizens. This problem is more serious in India where the rate of urban growth is higher (George ).
The rapid growth of the urban population has resulted in increases in the need for basic services and the access to appropriate water supply and sanitation (Satterthwaite et al. ). The rapid growth of urban areas has further affected water quality due to the increase of the urban popu- In Bangalore city, the incidence of waterborne infections is consistently high due to a limited supply of drinking water (Sheeba et al. ). Many studies have been reported on the physico-chemical quality of drinking water in Bangalore but the hazard identification and health risk-associated assessments have not yet been reported.
This study was based on two aspects of water quality: one is the microbial contamination and the other is focused on physico-chemical parameters. The microbial contamination is mainly due to waterborne pathogens, especially from the members of Enterobacteriaceae. Generally, most of the microbial pathogens are transmitted via contaminated food, but waterborne transmission has been well documented for recreational and contaminated drinking water (Ashbolt ). Contaminated drinking water serves as an important vehicle for transmitting both chemical and microbial agents to cause diseases in humans (Hurst ). Increasing incidents of waterborne diseases via contaminated drinking water have become a public health problem in both developed and developing countries (Pandey et al. ).
The main objective of this research is to assess the microbial health risk generated in the households of Bangalore city and to determine the physico-chemical and microbiological quality of drinking water supply for the end-user. In view of this, an attempt was made to carry out microbiological hazard identification from the households of Bangalore city, Karnataka, India.

METHODS
This study was carried out in and around Bangalore, Karnataka, India, located at 13.0320 N, 77.6360 E. The city population mainly depends on bore well and Cauvery water sources for drinking purpose.
A survey was conducted during the study period to determine the type of water consumption (Cauvery water, bore well and bottled water). The samples were collected in pre-cleaned, sterilized polyethene bottles. They were analysed by following microbiological and physico-chemical parameters. Microbiological parameters were examined within 2 hours of sample collection. All the measurements were done in triplicate and values were expressed as mean ± standard deviation. Biochemical tests such as indole, MR-VP and urease were performed for phenotypic identification of enteric isolates.
On-site analyses of pH, conductivity, turbidity and temperature were carried out at the site of sample collection following the standard protocols and methods of the American Public Health Agency. Total hardness was measured according to the standard methods (APHA ). Winkler's method (APHA ) was used for determination of the dissolved oxygen (DO) using azide modification. All the measurements were done in triplicate and values were expressed as mean ± standard deviation. Microbiological and physico-chemical characteristics of water samples are presented in Table 2.

Microbiological water quality
The results of the study show that most of the household water samples were contaminated with coliform bacteria   The conductivity of all water samples showed ranges from 400 (μmho) to 1,120 (μmho). Dissolved oxygen (DO) concentration water samples observed were a maximum 7.4 and minimum 6.1. For all water samples, the DO values were within the permissible limit.
The total hardness was found to be 130 mg/L to 275 mg/L. For all water samples, the total hardness is within the permissible limit recommended by CPHEEO (), BIS () and WHO ().
During the study period, temperature varied from 26 C to 29 C. The minimum temperature was recorded with water sample SGW-12 and the maximum with SSW-1, SGW-4, SSW-8 and SSW-20.
In this present study, the water samples contain turbidity value ranges of 0.4 NTU (SSW-11, SSW-17 and SGW-18) to 4.2 NTU (SSW-1). Drinking water is considered to be good quality when it contains turbidity values of 1 or below (Cotruvo ). In this study, some sampling stations exceeded the limit of turbidity value WHO ().

Correlation between physico-chemical and microbiological quality
For the correlation study, a few physico-chemical parameters with microbial parameters to check the interrelationship of each parameter were used. Statistically, using Pearson's correlation coefficient TCC was found to be positively and significantly related to pH and turbidity.
The pH was found to be significantly and positively related to turbidity. Electrical conductivity was found to be significantly and positively related to DO and TH. TCC was negatively correlated to EC, DO and TH. The pH was negatively correlated with EC, DO and TH. EC, DO and TH were negatively correlated with turbidity. The rest of the