Surveillance of the chemical and microbial quality of drinking water for safe water supply in an urban area

Drinking water supply and sanitation are critical water uses for human survival, health and prosperity (WHO 2004; Marobhe et al. 2007). Almost 900 million people lack access to an improved water supply and 2.6 billion to basic sanitation (WHO & UNICEF 2010). The adverse impacts on public health from poor water supply have long been recognized in both developing and developed countries, and take the form of disease outbreaks (Esrey et al. 1991; Ford 1999; Payment & Hunter 2001). Water supply access in most developing countries is complex compared with access in developed countries (Howard & Bartram 2005). Initiatives to manage the safety of water not only support public health, but also often promote socioeconomic development and well-being (WHO 2013). The main problems related to drinking water quality are associated with the conditions of the water supply network (Lehtola et al. 2004; Karavoltsosa et al. 2008; Farooq et al. 2008) during collection and storage (Andrew et al. 2005), poor operational management and unsatisfactory sanitary practices, so it becomes obligatory to monitor water quality at each stage of delivery (Khadse et al. 2011a, 2011b, 2011c). Surveillance of drinking water quality (SDWQ) is the continuous and vigilant public health assessment and overview of the safety and acceptability of drinking water supplies (WHO 1993). SDWQ is necessary to avoid risks from chemical and bacteriological pollutants and to assure consumers that drinking water is safe and can be consumed without any risk (Leeuwen 2000). SDWQ programmes identify those interventions that will result in improvements in water supply that will be protective of public health (Lloyd & Bartram 1991; Lloyd et al. 1991, WHO 1997; Howard 2002). In the present paper, the intake water quality of treatment plants, water quality at different treatment stages and at the consumer end was monitored for three different seasons to assess the drinking water quality status of Bhopal city.

The Kolar WTP has an installed capacity of 160 MLD and treats water through a conventional treatment process with rapid sand filters, with the addition of potassium permanganate along with alum to remove manganese. Treated water is pumped up at a distance of 3.2 km with the help of five centrifugal pumps into a BPT (break pressure tank), after which it flows under gravity. A prestressed concrete pipeline of 1,450 mm diameter was provided for clear water transmission. Water flows under gravity from the BPT through pipes of 1,500 mm diameter and 24.6 km length to the Arera hills reservoir. Two feeder mains also branch off the gravity main, which supply different ground service reservoirs, overhead tanks and sumps. Raw water from Upper Lake is extracted from seven different points, from where it is treated and pumped to the distribution network. Most of the distribution pipes are cast iron or galvanized iron. The distribution network in this part of the city is around 80 years old. Pilferage and physical losses are reported to be very high in this area.

Piped water supply in the city covers about 67% of the population; the rest have to depend on handpumps and private borewells. Until 2005, out of Bhopal's 97,092 water connections, 95,808 were domestic. The operations and maintenance (O&M) of the WTPs and distribution system was undertaken by the Bhopal Municipal Corporation, with assistance from engineering staff deputed from the Public Health Engineering Department (PHED). Although sufficient water is being produced in the WTPs of Bhopal to satisfy the prescribed per capita supply rate, the actual supply is limited to barely 2–3 hours daily at low pressure.

About 40% of Bhopal has a sewerage network, which covers about 28–30% of the population. Of the 66 wards within municipal limits, 10 are fully sewered and 18 are partially sewered. Of the 193 MLD officially generated sewage, only 39 MLD was carried through the sewerage network for treatment in the city's eight sewage treatment plants. The remaining sewage was disposed of into water sources such as the Upper Lake. The treated waste was disposed of downstream of Bhopal's lakes and into the drains, from where it flowed into the Patra, Halali and Betwa rivers. Many of the city's septic tanks are in a dilapidated state. According to the 2005 City Development Plan, they had not been cleaned in several years, and many of them did not have soak pits. As a result, raw sewage finds its way to nearby stormwater drains. A large number of households in slum areas have to use dry latrines or resort to open defecation.

Criteria for selecting sampling locations were chosen with a view to examining water quality from raw water at source to the consumer end, including all the intermediate stages of treatment units and distribution network. Samples of raw water, settled water, filtered water and treated water after chlorination were collected during three seasons for seven consecutive days during 2002–2003 from the selected WTPs in order to examine the plant performance. The raw water and treated water samples were collected and analysed for physicochemical and bacteriological parameters. The settled water was collected from the overflow of the settling tank of the WTPs and examined for turbidity and sulfate. The filtered water was collected from the combined channel of the filters after filtration and analysed for turbidity, sulfate and bacteriological quality. Final treated water after chlorination was collected from the sump of each WTP. To assess the en route bacteriological contamination in distribution and supply, representative samples from 10 elevated service reservoirs (ESRs) and 22 samples from the consumer end were collected. The water analysis was carried out according to Standard Methods (1998). A knowledge, attitude and practice (KAP) survey was conducted which pertains to defined specific and measurable campaign objectives based on the problems identified by the Bhopal Municipal Corporation.

The analytical results for the physicochemical and bacteriological parameters of the water samples collected at the WTPs are reported in Tables 2–4 for winter, summer and monsoon seasons, respectively.

During winter there was no significant change in raw water quality on a day-to-day basis (Table 2). Turbidity of raw and settled water was in the range of 1.2–3.0 NTU and 0.5–1.6 NTU, respectively. As the raw water turbidity was very low, alum was not added during the study period. The total coliform (TC) and faecal coliform (FC) counts were in the range of 20–50 CFU/100 ml and up to 4 CFU/100 ml, respectively. Filtered water quality showed that TC and FC were totally removed in the treatment process. Overall unit-wise performance of the plant was satisfactory. During summer, the turbidity of raw, settled and filtered water was in the range of 0.6–1.9 NTU, 0.3–2.1 NTU and 0.2–0.6 NTU, respectively. In raw water manganese content was in the range of 0.3–0.4 mg/L. To remove the manganese from the water KMnO₄ was added along with lime and alum in the treatment. Finished water showed the removal of manganese completely. In raw water, TC and FC counts were in the range of 20–220 CFU/100 ml and up to 50 CFU/100 ml, respectively, whereas in filtered water TC and FC counts were up to 36 CFU/100 ml and 2 CFU/100 ml. During monsoon the turbidity of raw, settled and filtered water was in the range of 7.5–120 NTU, 5.0–12 NTU and 0.2–2.0 NTU, respectively (Table 4). Manganese content was not observed. TC and FC in raw water were in the range of 300–680 CFU/100 ml and 40–80 CFU/100 ml, respectively. The TC and FC counts for filtered water were in the range of 20–130 CFU/100 ml and up to 60 CFU/100 ml, respectively.

The treated water quality of the plant during all three seasons was within the desirable limits according to the CPHEEO guidelines (Central Public Health and Environmental Engineering Organisation, Government of India). Disinfection of filtered water is achieved using chlorine gas. Residual chlorine in the finished water was in the range of 0.8–1.0 mg/L, 0.8–2.0 mg/L and 0.2–1 mg/L during winter, summer and monsoon seasons, respectively.

Pre-chlorination of raw water is carried out at the WTP year-round with a view to improving the alum coagulation, controlling algal growth, decreasing organic load to the filters and ensuring effective post-chlorination. The chlorine gas is added in the main raw water channel at 2–2.5 kg/h (2–2.5 mg/L) depending on raw water quality. During winter the raw water turbidity was in the range of 1.1–1.6 NTU. The alum dose was 12 mg/L. The turbidity of filtered water was 0.8–1 NTU. During summer the raw water turbidity was 2.2–3.5 NTU. On occasions, high turbidity values of up to 15 NTU were observed due to channelling the raw water towards the pumping station. The alum dose was 12 mg/L. The turbidity of settled and filtered water was in the range of 1.8–7.3 NTU and 1.7–4.3 NTU, respectively. Filtered water was chlorinated at the end of the combined filter water channel at 2 kg chlorine gas per hour (2 mg/L). The post-chlorination dose was decided considering leakage of chlorine from the chlorinators. Finished water residual chlorine was in the range of 0.4–0.6 mg/L during winter, 0.1–2.0 mg/L during summer and 1.5 mg/L during monsoon.

The finished water quality was within the desirable limits according to CPHEEO guidelines. During winter, the TC and FC counts in raw water were in the range of 290–2,050 CFU/100 ml and 10–270 CFU/100 ml, respectively. In filtered water, the TC and FC count was absent. During summer, the TC and FC counts in raw water were in the range of 304–900 CFU/100 ml and 35–180 CFU/100 ml, respectively. In filtered water, the TC and FC counts were up to 396 CFU/100 ml and 22 CFU/100 ml, respectively. During the monsoon, the TC and FC counts in raw water were 2,000 CFU/100 ml and 540 CFU/100 ml, respectively. In filtered water, the TC count was 130 CFU/100 ml and FC count was absent.

During winter, raw water turbidity was in the range of 1.4–14.0 NTU. Alum is used at 20 mg/L as a coagulant. The settled water and filtered water turbidity was in the range of 0.5–0.9 NTU and 0.4–0.6 NTU, respectively. All the units of the plant were in good working condition. During summer raw water for the WTP is drawn through a dug canal in the Upper Lake fetching water from a location nearly 1 km away from the intake point. This resulted in an increase in raw water turbidity. The raw water turbidity was in the range of 177–371 NTU. The applied alum dose was 35–45 mg/L. The settled water and filtered water turbidity were in the range of 0.25–1.6 NTU and 0.4–1.0 NTU, respectively. During monsoon, turbidity of raw, settled and filtered water were in the range of 95–340 NTU, 0.5–1.5 NTU and 0.1–0.5 NTU, respectively. The applied alum dose was 40–60 mg/L. The finished water quality met CPHEEO guidelines. The water after filtration was disinfected by chlorine gas. Applied chlorine dose during winter was 2 mg/L, and the residual chlorine was 0.4–1.0 mg/L. During summer, the applied chlorine dose was 2 mg/L and residual chlorine was 0.1–1.5 mg/L. During the monsoon, the applied chlorine dose was 2.5 mg/L and the residual chlorine was 0.3–2 mg/L.

Bacterial quality of raw water during winter indicated the presence of TC and FC as 190–300 CFU/100 ml and up to 18 CFU/100 ml, respectively. In filtered water, the TC count was up to 160 CFU/100 ml, and FC was absent. During summer, the raw water TC and FC counts were 120–1,200 CFU/100 ml and up to 155 CFU/100 ml, respectively. In filtered water, the TC and FC counts were 12–88 CFU/100 ml and up to 30 CFU/100 ml, respectively. During the monsoon, the TC and FC counts in raw water were 160–2,180 CFU/100 ml and up to 135 CFU/100 ml, respectively, whereas in filtered water these counts were 20–380 CFU/100 ml and up to 600 CFU/100 ml, respectively. Finished water after disinfection was free from bacterial contamination in all seasons.

During winter, the turbidity of raw water was 1.4–2 NTU. Alum solution is added as a coagulant in the raw water channel. Water is then diverted to three individual units comprising a flocculator, settling tank and filter beds. The uncontrolled doses of alum coupled with inefficient working of all units were found to result in poor coagulation, flocculation, sedimentation and filtration. The turbidity of settled and filtered water was in the range of 2.3–3.2 NTU and 0.6–2.0 NTU, respectively, indicating poor performance of the WTP. During summer, the turbidity of raw water was 15–53 NTU. The applied alum dose was 40–50 mg/L. The alum bricks were put in the raw water channel and this uncontrolled alum dose, coupled with inefficient working of all units, was found to result in poor performance of the plant. The turbidity of settled and filtered water was 4–30 NTU and 0.8–14.3 NTU, respectively. During the monsoon, turbidity of raw, settled and filtered water was in the range of 1.5–5.5 NTU, 0.1–2.0 NTU and 0.1–0.8 NTU, respectively. Alum dose was 35 mg/L. However, the finished water met the potable water quality according to CPHEEO guidelines.

Chlorination is done at the end of the combined filtered water channel which led to the sump. The applied chlorine dose was 1.5–2 mg/L and residual chlorine was 0.8–1 mg/L during winter. In raw water TC and FC counts were 450–1,300 CFU/100 ml and 6–70 CFU/100 ml, respectively. In filtered water TC count was up to 90 CFU/100 ml and FC were absent. During summer the raw water TC and FC counts were 240–850 CFU/100 ml and up to 150 CFU/100 ml, respectively. In filtered water TC and FC counts were up to 120 CFU/100 ml and 18 CFU/100 ml, respectively. The applied chlorine dose was 2 mg/L. The residual chlorine in finished water was 0.4–1.0 mg/L. Bacterial count in treated water was absent. During monsoon the raw water TC and FC counts were in the range of 380–1,160 CFU/100 ml and 90–160 CFU/100 ml, respectively. In filtered water bacterial counts for TC and FC were 40–190 CFU/100 ml and 12–36 CFU/100 ml, respectively. Significant TC and FC counts in filtered water indicated malfunctioning of filter beds. However in finished water, after chlorination, TC and FC were absent.

The raw water turbidity during winter was in the range of 1.4–1.6 NTU. The applied alum dose was 12 mg/L. The dose of alum was not regulated properly as the solution dosing system was defunct and the dose was controlled manually. The turbidity of settled water and filtered water was in the range of 1.1–1.4 NTU and 0.35–0.45 NTU, respectively, indicating satisfactory performance of filters. During summer the raw water turbidity was in the range of 1.6–8 NTU. The applied alum dose was 10–12 mg/L. The settled and the filtered water turbidity was in the range of 0.9–2.5 NTU and 1.1–2.8 NTU, respectively. The filtered water turbidity was observed to be more than settled water turbidity, indicated inefficient working of filter beds and poor maintenance. During monsoon turbidity of raw, settled and filtered water was in the range of 1.4–2.4 NTU, 0.8–1.5 NTU and 0.1–0.5 NTU, respectively. Alum dose applied was 15–20 mg/L. Overall functionality of the plant during the study period was satisfactory. The finished water quality conformed to the potable water quality as per CPHEEO guidelines. Disinfection of water was done at the combined filtered water channel, which leads to the sump. The residual chlorine of sump water was in the range of 0.8–2 mg/L during the winter and summer seasons while during monsoon it was 1.5–2 mg/L.

During winter, the TC and FC counts in raw water were in the range of 10–410 CFU/100 ml and up to 38 CFU/100 ml, respectively. In filtered water TC and FC counts were up to 40 CFU/100 ml and 2 CFU/100 ml, respectively. During summer TC and FC counts in raw water were in the range of 130–400 CFU/100 ml and up to 150 CFU/100 ml, respectively. The filtered water showed TC and FC counts ranged from 12–416 CFU/100 ml and up to 54 CFU/100 ml, respectively. During the monsoon, the TC and FC counts of raw water were 180–1,040 CFU/100 ml and 80–560 CFU/100 ml, respectively. In filtered water, the TC and FC counts were 30–640 CFU/100 ml and up to 85 CFU/100 ml, respectively. However, finished water after chlorination was free from bacterial contamination in all seasons.

During winter, the raw water turbidity was 1.6–3.5 NTU. The alum dose was 20 mg/L. The settled water turbidity was 2.1–2.5 NTU, reflecting that the turbidity removal was marginal due to poor floc formation and improper settling of flocs. The filtered water turbidity was 1.0–1.4 NTU. The presence of mud balls in the filters indicates that the backwash was inadequate and ineffective. During summer, the availability of raw water in the Upper Lake was critical, and the required quantity of raw water was not available therefore the plant was operated only for 4–5 hours. The raw water turbidity was 10–15 NTU. As per requirements, the alum dose was 20–30 mg/L. The turbidities of settled water and filtered water were 2.5–4.2 NTU and 0.7–4.4 NTU, respectively. Filtered water was disinfected at the end of the combined filter water channel by chlorine gas at 3.5 mg/L. The residual chlorine in sump water during winter and summer was 2–2.5 mg/L and 0.8–1 mg/L, respectively. During monsoon the plant was not in operation due to non-availability of raw water from Upper Lake. The finished water quality was within the desirable limit as per CPHEEO guidelines.

During winter, the TC and FC counts in raw water were 30–150 CFU/100 ml and up to 16 CFU/100 ml, respectively, while at the filter outlet of the phase I plant the TC and FC counts were up to 30 CFU/100 ml and 14 CFU/100 ml, respectively. In the filter outlet of the phase II plant, the TC and FC counts were in the range of 50–970 CFU/100 ml and up to 54 CFU/100 ml, respectively. Sufficient residual chlorine was present in the sump water. During summer, the TC and FC counts in raw water were 128–900 CFU/100 ml and 30–60 CFU/100 ml, respectively. At the filter outlet of the phase I plant, TC and FC counts were in the range of 60–440 CFU/100 ml and up to 24 CFU/100 ml, respectively. At the filter outlet of phase II plant, TC and FC counts were in the range of 24–256 CFU/100 ml and up to 8 CFU/100 ml respectively. The occurrence of TC and FC counts at the filter outlet showed the foul condition of the filter beds. During the study period, sufficient residual chlorine was present in sump water.

The water quality data for bacteriological parameters at the ESRs and the consumer end during the three seasons are reported in Tables 5 and 6, respectively. Residual chlorine was absent during winter in the ESRs located at Badal Mahal, Anand Nagar and Dussehra Maidan; therefore the TC counts were up to 150 CFU/100 ml, 80 CFU/100 ml and 300 CFU/100 ml, respectively, and the FC count was nil, up to 24 CFU/100 ml and 4 CFU/100 ml, respectively. At Jawahar Chowk ESR, the TC and FC counts were 20 CFU/100 ml and 10 CFU/100 ml, respectively. The presence of coliforms in these samples may be attributed to inadequate chlorination, insufficient contact time and poor maintenance of the ESR. Water samples from the ESRs located at Shahapura, Arera Colony, Char Imali, Govindpura, Sant Hirdaram Nagar and Shahajahanabad were free from bacterial contamination. This may be due to the proper chlorination and adequate contact period.

During winter, it was observed that nine samples from the distribution network were not contaminated with bacteria, indicating that there was no en route contamination of the water line. At these locations, residual chlorine was in the range of 0–0.4 mg/L. The remaining locations were occasionally contaminated with TC, but FC was absent. The residual chlorine present in the samples was in the range of trace–0.2 mg/L. The TC and FC counts present in contaminated water samples were 120–980 CFU/100 ml and 16–120 CFU/100 ml, respectively. The residual chlorine estimated for these samples was 0–0.2 mg/L. The presence of TC and FC counts in the samples may be due to leakages, insanitary conditions around the distribution system and sampling locations. During summer, TC were present in all the samples collected from ESRs, whereas FC count was found occasionally. At the consumer end, all the samples were contaminated by TC and FC, as residual chlorine was absent at most of the sampling points. During the monsoon, with some exceptions, all the samples from the ESRs and the consumer end were bacteriologically contaminated. This may be attributed to intermittent water supply, leakages in the distribution line, local insanitary conditions and insufficient contact period for chlorine.

• Perceived state of drinking water pollution: 40% of respondents opined that the water quality supplied in Bhopal city is good, 30% showed displeasure and another 30% were not able to give an opinion.

• Awareness of the SDWQ and information on drinking water standards: Awareness of the SDWQ programme was 25% among the general public, 56% among water works personnel, and 62% among health agencies' personnel. Awareness of information on drinking water quality standards was 25% among the general public, 55% among water works personnel and 70% among health agencies.

• Information on private water supply: Among the general public, 15% of the respondents indicated the use of private tube wells to meet their water demand.

• Accountability for the efficient and effective delivery of water supply: 50% of the respondents among the general public indicated that the water supply is satisfactory; 80% of respondents among water works personnel indicated 90% supply efficiency and effective delivery of finished water.

• Knowledge of individuals/institutions of water supply agency services: 70% of respondents among the general public were aware that water supply treatment facilities are available in the city.

• Procedure of complaints against drinking water supply: Complaints are received in the office of Bhopal Municipal Corporation; 75% of the respondents among water works personnel indicated the immediate measures for the handling of reported complaints about water quality.

• Knowledge of sanitary survey: 70% of the respondents among the general public were found to be aware of cleaning practices and health aspects related to sanitation.

• Knowledge on preventive measures and health education: 50% of the respondents among the general public were aware of the preventive measures to be taken to avoid water-borne diseases. However, there is a need to impart health education on these aspects.

It was observed that even slum-dwellers and those in economically disadvantaged areas were concerned with the water supply. Questions were promptly answered in discussion groups, and the KAP survey reflects popular opinion rather than individuals’ knowledge. Some women were shy to respond in discussion groups for sharing information. It was difficult to get responses from these women; at the same time those who wanted to narrate their experiences were highly vocal in furnishing the information. By and large, the residents were aware of water quality and sampling. The residents were very keen to provide information on distribution schedules and quantity, but had few complaints about the local staff looking after water distribution.

Discharge of wastewater into the lake/dam, municipal solid waste disposal and direct in-flow of surface runoff are prevented to protect the water quality of the Kolar dam and Upper Lake. During summer, the Upper Lake water is not sufficient to run the plants and some WTPs are closed. Laboratory facilities are provided at five WTPs, except at Idgah WTP, where water testing is carried out for pH, turbidity, alkalinity, hardness and residual chlorine. Bacteriological parameters are tested only at Kolar, Phulphukta and Laxmi Narayangiri WTPs. At Kolar WTP, iron and manganese are also tested, in addition to the above parameters, due to their occurrence in raw water during summer. There is no organized leak detection programme, and the leaks are repaired on the basis of public complaints and as noticed by water supply personnel. A SDWQ programme was not in practice. The PHED laboratory undertakes the analysis of the water samples sent by the Municipal Corporation. During the study period, some of the samples collected from the distribution system were found to be positive for TC and FC; hence there exists an urgent need to create the infrastructural facility to carry out SDWQ.

• Instruments/equipment for flow measurement and head loss indicators need to be repaired and maintained.

• Coagulant dosing needs to be monitored to avoid carryover of micro flocs.

• Backwash needs to be improved to avoid scum formation in settling tank, filter beds and the presence of mud balls in the filters of some of the WTPs.

• The requisite quantity of residual chlorine needs to be ensured with a proper chlorine dose.

• In the places where the faecal contamination was present at the consumer end, the necessary precautionary measures need to be undertaken to avoid any adverse impact on health.

• Water testing laboratories at treatment plants need to be upgraded.

• O&M of Kolar WTP is undertaken by PHED, while other WTPs and water distribution are the responsibility of Bhopal Municipal Corporation. This hinders the smooth functioning of the water supply scheme. The responsibility should be assigned to only one agency.

• It is essential to increase the water storage capacity of Upper Lake.

• All the O&M aspects of WTPs need due attention.

• The proper maintenance of the distribution network, awareness of the hygienic and sanitary conditions around the public taps, and proper storage of water will definitely help in maintaining water quality within the potable water standards.

• Surveillance of the water supply and timely measures to control contamination, along with people's participation, will lead to water safety and better health of the community.

From the present study, it is observed that the drinking water supplied is of good physicochemical and bacterial quality. No significant change in physicochemical parameters of raw water quality was observed on a day-to-day basis. The city had an intermittent water supply; therefore during non-supply hours, through back suction through leakages/damage/faulty joints in the supply lines, some insanitary material might enter the pipelines and be carried up to the consumer end when the supply resumes. Proper maintenance of the distribution network, awareness of the hygienic and sanitary conditions around the public taps, and proper storage of water will help in maintaining water quality within the potable water standards. Thus, the surveillance of the water supply and timely measures to control contamination, along with people's participation, will lead to water safety and better health of the community.