Controlling water pollution through technology

07 Jun 2021

Opinion: Sanjib Pohit Soumi Roy Chowdhury and Supratik Guha

Using tech to monitor river water quality real-time will help.

India is a home to 4 per cent of the world’s freshwater resources and it ranks among the top 10 water-rich countries of the world. In spite of being home to the major river systems both perennial and non-perennial India is a designated water stressed region (NITI Aayog 2019). The river basins suffer from the pressure of an ever-growing population and rapid industrialisation and urbanisation across the country. All these factors make the basins vulnerable to the incessant release of effluents in the form of sewage and large volumes of solid and industrial wastes. Over the years this discourse on water pollution has made their way into policy-making. 

In the mid-1980s Rajiv Gandhi launched Ganga Action Plan I (GAP-I) with the main objective to improve the water quality of the Ganga to acceptable standards by preventing the pollution load reaching the river. In 1987 the objective of GAP was recast as restoring the river water quality to the ‘Bathing Class’ standard. 

Subsequently the programme of river cleaning was extended to other major rivers of the country under two separate schemes of GAP; the Phase-II and the National River Conservation Plan (NRCP). Yamuna and Gomati Action Plans were approved in April 1993 under the Ganga Action Plan Phase-II. Programmes of other major rivers were subsequently approved in 1995 under NRCP. In recent times Prime Minister Narendra Modi announced the launch of the Namami Gange Clean-up programme with a budget of ₹20000 crore during the period 2015-2020.

The overarching action plans launched under these programmes has introduced multiple interventions. One construction of sewerage treatment plants in towns along the rivers so that untreated sewerage are not dumped into the rivers. Two the large polluting industries along the rivers have been retrofitted with treatment plants or were closed down if the water was not cleaned before dumping to the city sewerage or to the river. 

Three government/municipal authorities took initiatives to construct common effluent treatment plants in industrial clusters to clean discharged water. Fourth slums on the river bed along with their inhabitants are relocated so that their daily usage in the river bed do not lead to pollution of water. These steps have been implemented in the major rivers of India particularly in

Ganga/Yamuna. In spite of all these efforts in 2017 the National Green Tribunal stated that “not a single drop of river Ganga has been cleaned so far.” By and large the same view holds for other rivers of India where investment has been undertaken under the National River Conservation Plan (NRCP).

Who is to blame?

Who is to be blamed for this sad state of affairs? The industries or the industrial clusters located in the cities claim they have installed treatment plants to discharge clean water in the urban drains. The inspectors visit them regularly to check whether these are being operated or not. An adverse report from them lead to penalty or closure of the plant till the problem is sorted out. So where is the problem? 

The crux of the issue lies with the capacity/quality of urban sewerage treatment plants which are unable to cope with the ever increasing sewerage load due to the population pressure in the cities. There is a logic in this argument. Most of the cities in the Ganga basin are in a catch-22 position with respect to their capacity of sewerage treatment plant. They end up discharging polluted drain water in the Ganga river since the capacity of the plant falls short of the sewerage load. This is true also for other cities lying beside other principal rivers like Yamuna Godavari etc. 

However the pandemic related industrial lockdown provided once in a lifetime opportunity to identify the principal contributor of pollution in a river like the Ganga. The nationwide lockdown was imposed on March 25 2020 and within 10 days signs of improvement in water quality started surfacing. According to the real-time water monitoring data of the CPCB out of the 36 monitoring units placed at various points of the Ganga river the water quality around 27 points was found suitable for bathing and propagation of wildlife and fisheries.

On April 4 at Varanasi’s Nagwa Nala the Dissolved Oxygen (DO) values were found increased to 6.8 milligram/litre against 3.8 mg/l on March 6showcasing an extraordinary improvement of 79 per cent in DO values. Ganga water at Haridwar and Rishikesh was reported fit for drinking due to 500 per cent decrease in sewage and industrial effluents. 

This improvement was unprecedented. Given non-industrial pollutant loads are unlikely to change in a short period of time we can safely assume that it is the industrial pollutants that have always been the principal culprit for polluted river water. When most polluting industries are not even allowed to function without treatment plants is it really possible to blame the industries? Or can we assume that there is a nexus between the inspectors and the factory owners to look out for other ways in lieu of a monthly remuneration (speed money)? It may well be that the factory owners get prior information before a surprise raid by higher authorities so that the treatment plants can be kept operational else they keep it switched off to save operation cost.

 Automated sensors

This calls for a continuous in-situ sewerage water quality monitoring systems without human intervention which will provide real-time data on water quality’s health. With advances in technology this is now a possibility and is cost effective.

Recently Water-to-Cloud study of University of Chicago’s Tata Centre for Development ( in collaboration with NCAER has demonstrated that multiple submersible automated sensors attached to a boat can be used to gather high-resolution spatially and temporally varying water data. Dynamic mapping of the river water quality using this high-frequency spatial and temporal data is helping to understand how the water quality is changing with weather pollution fishing and general use.

This mapping can help pinpoint pollution sources and ensure regulatory compliance. Through powerful visualisation the heatmaps can help identify pollution sources that can even contribute in controlling infectious diseases. This type of sensors can be easily attached at the discharge point of polluting industries to measure pollutant loads at real-time basis. This may turn out to be cheaper and more effective than the present system of human-based intervention which often leads to rent-seeking activities.

Sanjib Pohit and Soumi Roy Chowdhury are respectively Professor and Associate Fellow at NCAER. Supratik is Professor Pritzker School of Molecular Engineering University of Chicago. Views are personal.