No clarity on the long-term effects of treated sewage

No clarity on the long-term effects of treated sewage

A view of the plant in Bengaluru where primary treatment of sewage is done. (DH Photo/Sathish Badiger)

The state government has committed a blunder in not looking at the long-term effects of a project which seeks to supply the treated sewage of Bengaluru to the lakes in Kolar and Chikkaballapur districts.

The government is yet to acknowledge the problem of chemicals, surfactants, detergents and heavy metals in the water. Every year, more than 30,000 new chemicals are getting
added to sewage. This is due to the increase in the number of chemicals used in our daily life. As a result, the sewage is not the same as what it was a few years earlier. And the long-term biological effects of this development are not known.

A complete analysis, including speciation of organic and inorganic chemicals, needs to be done to get a clear picture. The government should not have jumped into this kind of experimentation without involving prior scientific study. Analysis should be done to know the specific chemicals causing high levels of chemical oxygen demand and total organic carbon, which will destroy the lakes if not treated.

The assumption that heavy metal levels below detectable levels are fine is wrong. We should realise that such elements will accumulate in the soil. Over a period of time, the soil and the lake bed will be contaminated due to accumulation and absorption of chemicals and metabolites.

Lacks analysis

Moreover, how does the government plan to prevent the use of surface water by people or cattle? When these things accumulate in the body of an animal, will it not get transferred to humans over time? We have not even begun to make an analysis of the effect of treated sewage on agricultural land.

The government convinced the Supreme Court to lift the stay on the KC Valley project. But my concern is about the idea of groundwater recharge itself. First, the sewage is not treated properly. More importantly, a proper procedure is not followed. Whenever you want to recharge a lake, it must flow for 20 km in natural circumstances and water should fall from a 20 ft height, as per the guidelines issued in the ‘Manual on sewage and sewage treatment systems, Part A’ 2013.

The concept of discharging sewage to lakes after secondary treatment is not envisaged in the urban water reuse policy of the state government. A clear framework would have helped guide the project implementation in the best interest of its beneficiaries.

The government should set up a continuous monitoring mechanism and a scientific and technical body that also has stakeholders from Kolar and Chikkaballapur committees on board. When we showed the presence of dangerous amounts of heavy metals and chemicals, the government said it was the result of a breach. Such a breach should not be a ruse for a Rs 1,300 crore project.

Proactive measures like online monitoring will help avoid the situation of people falling sick due to contaminated water. All these are issues that do not require cutting-edge technology as much as the sincere efforts from officials. It’s not just a question of one department or official doing it. It should be a collective effort, and scientists and administrators should be a part of the proactive machinery.

We need studies and analysis. Natural water has classifications but we have no classification of treated sewage, which is crucial to know how safe it is. 

Most of the sewage treatment plants are handled by civil engineers who have no practical approach to the complexity of the new-age chemicals. The foam in Bellandur has remained a challenge. A third agency should monitor the sewage before it enters the lake.

With this project, Bengaluru is setting an example for other cities, let the example be more about substance. At present, there is no transparency in the project.

(The writer is Chief Research Scientist, Department of Chemical Engineering, Indian Institute of Science, Bengaluru)