High Concentration of Fecal coliform in stream, drinking water is safe

Tenzin Lhaden

According to the water sample collected from Motithang stream, Thimphu on September 9, 2022 showed the concentration of Fecal coliform to be at 108(CFU/100ml). The concentration of Fecal Coliform exceeding 50 is categorised as grossly polluted water for human consumption.

The presence of fecal coliform bacteria in aquatic environments indicates that the water has been contaminated with the fecal material of humans or other animals. At the time this occurred, the source water may have been contaminated by pathogens or disease-producing bacteria or viruses which can also exist in fecal material.
Some waterborne pathogenic diseases include typhoid fever, viral and bacterial gastroenteritis, and hepatitis A. The presence of fecal contamination is an indicator that a potential health risk exists for individuals exposed to this water. Fecal coliform bacteria may occur in ambient water as a result of the overflow of domestic sewage or nonpoint sources of human and animal waste.

For safe drinking water the concentration of Fecal coliform should be 0(zero). Since the stream water contain high concentration of fecal coliform, the Thimphu Thromde (city cooperation) carry out drinking water testing for similar contamination as and when required although the Thromde does not carry out individual quality tests for all residents and institutions within Thromde. The disinfection (chlorination) is done at the Water Treatment Plants (WTP) and also at water reservoirs to make sure residual chlorine at the water meter point (households) is 0.2ppm. If meter point chlorine content is 0.2ppm, there is no contamination of water and it is safe for drinking without boiling.

According to Thimphu Thromde, “We do daily disinfection at various stages so that, we can assure that residual chlorine is there at tap points. But if residents don’t clean their respective water storage tanks, it is more likely that water is contaminated at the storage tank due to prolonged storage of water.”

The water source is in Motithang which has 3 rivulets that are treated at Motithang Water Treatment Plant(WTP). From Mothithang WTP, water is distributed to reservoirs and further distributed to residents of upper and lower Motithang, Changangkha, Kawajangsa, Norzin Lam tag, NPPF colony and Changgidaphu areas.

The raw water quality from the source is safe but it requires treatment for turbidity i.e filtration of sediments. However, the causes of pollution may be due to lack of proper and timely cleaning of respective storage tanks. There are also chances of vacuum suction at pipe joints when there is no water in the pipes.

As soon as the thromde was notified of the motithang stream test result, testing was carried out to find the point of contamination. Tests on the quality of raw water for other sources were carried out and also after treatment of water at WTPs. Thromde also test quality if there is a request from other stakeholders, and share their test reports.

If contamination has occurred after Thromde’s water meter point, then it is the responsibility of the residents – for timely cleaning of their storage tanks, according to Thromde. “We will be coordinating with Royal Center for Disease Control to discuss the case,” thromde added.

Thromde is further planning to improve watersource/water and to make intermittent supply of water 24/7 with proper District Metering Areas with rehabilitation and restoration of existing haphazard water distribution networks and household connections and ensure that all residents are metered and reduce of water losses and illegal connections (Non-revenue water). Thromde will also integrate water sources tapped by communities and other stakeholders and make sure that there is full cooperation from residents and every individual to stop overflowing storage tanks and internal leakages.