DJB likely to tap contaminated groundwater to bridge Delhi’s supply gap

With Delhi facing a water supply deficit of around 250 million gallons per day (MGD) during summer, the Delhi Jal Board (DJB) is exploring advanced treatment technologies to tap into contaminated groundwater aquifers for supplying potable water, particularly in areas along the Najafgarh drain, Garhi Mandu and other areas where total dissolved solids (TDS), heavy metals and levels of other contaminants are significantly high.The proposed technology should be capable of treating groundwater with TDS levels of up to 10,000 mg/l or higher. (File photo)The DJB has floated an expression of interest (EoI) inviting technology providers and research institutions to install and operate treatment systems capable of removing high concentrations of dissolved salts, heavy metals and other contaminants from groundwater extracted through tubewells.Groundwater quality and treatment standardsAccording to the October 16 project report, groundwater in several parts of Delhi, including areas along the Najafgarh drain and groundwater-rich locations such as Garhi Mandu, contains high levels of TDS, fluoride, nitrate, iron, manganese and heavy metals, including arsenic, lead and mercury, making it unsuitable for direct human consumption.Also Read:Delhi Jal Board approves ₹17,969 crore sewer overhaul plan, to divide network into 8 zonesThe TDS concentration in these areas generally ranges between 1,500 and 3,000 milligrams per litre, and may exceed 10,000 mg/l in some locations, according to the report.“The proposed technology should be capable of treating groundwater with TDS levels of up to 10,000 mg/l or higher and producing drinking water conforming to World Health Organization (WHO) and Bureau of Indian Standards (BIS) norms,” DJB has mandatedPlan to supplement Delhi’s water supplyThe initiative to tap into contaminated aquifers comes as the DJB plans to install 300-400 tubewells across Delhi to tap groundwater and supplement the city’s existing water supply. Officials have identified 26 tubewells near the Najafgarh drain, where groundwater quality assessments have found high TDS levels.As part of the plan, the DJB proposes to establish treatment units on an available land parcel at the Ujwa underground reservoir (UGR), where around 20,000 square metres of land is vacant. The treated groundwater is proposed to be blended with the existing water supply of 1.40 million gallons per day at the Ujwa reservoir.Also Read:Delhi Jal Board identifies 43 points of sewage contaminating Defence Colony, Barapullah stormwater networkProposed technologiesDJB has invited proposals for treatment capacities ranging from 10 MGD to 50 MGD or more, with modular designs that can be scaled up. Suggested technologies include high-recovery reverse osmosis and nanofiltration, although agencies may propose other proven solutions or a combination of technologies, DJB officials said.“Besides removing dissolved salts and heavy metals, the treatment systems will be required to reduce water wastage, maximise recovery and provide a plan for managing the concentrated reject water generated during treatment”, the officials added.