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

The Delhi Jal Board, or DJB, is proposing to extract groundwater from contaminated aquifers, treat it, and use it as potable water. The plan responds to Delhi’s summer supply deficit of around 250 million gallons per day. It targets areas where groundwater is plentiful but unsafe to drink without advanced treatment.

The DJB has invited technology providers and research institutions to install and operate treatment systems. These systems must handle groundwater with TDS of up to 10,000 milligrams per litre or higher. The treated water must meet World Health Organization and Bureau of Indian Standards norms. The DJB is considering high-recovery reverse osmosis, nanofiltration, or other proven combinations.

The wider plan includes 300-400 tubewells across Delhi. Twenty-six have been identified near the Najafgarh drain. Treatment units could be built on 20,000 square metres of vacant land at the Ujwa underground reservoir. Treated water would be blended with the reservoir’s existing 1.40 MGD supply, if the system proves workable.

Total dissolved solids, or TDS, measure the combined amount of dissolved substances in water. These can include salts and minerals, along with some other dissolved materials. TDS is usually reported in milligrams per litre. It gives a broad indication of how heavily mineralised the water is, but it does not identify every contaminant or prove that water is safe.

High TDS can make water taste unpleasant and can cause deposits or scaling in pipes and equipment. It may also occur alongside contaminants such as fluoride, nitrate, heavy metals and other substances. In Delhi’s affected areas, groundwater generally has 1,500 to 3,000 milligrams of TDS per litre, and some locations may exceed 10,000 milligrams per litre.

Because the groundwater also contains pollutants, the DJB says it is unsuitable for direct human consumption. Its proposed treatment must reduce dissolved salts and other contaminants, then produce water meeting WHO and BIS drinking-water norms. TDS reduction is therefore one part of a broader safety process, not the sole test of drinking quality.

Delhi’s summer water-supply deficit is around 250 million gallons per day, or MGD. That shortfall is driving the Delhi Jal Board to seek additional sources, including groundwater. The proposal is not simply to pump water directly, because several groundwater zones contain high TDS, heavy metals and other contaminants.

The DJB plans to install 300-400 tubewells across Delhi. Officials have already identified 26 tubewells near the Najafgarh drain, where assessments found high TDS levels. Groundwater from such wells would be sent through advanced treatment before being considered for potable supply.

The proposed treatment capacity ranges from 10 MGD to 50 MGD or more. Units could use modular designs, allowing expansion over time. At Ujwa, treatment facilities could occupy about 20,000 square metres of vacant land. Treated groundwater would be blended with the reservoir’s existing 1.40 MGD supply, helping supplement rather than replace Delhi’s current sources.

Groundwater in parts of Delhi, including areas near the Najafgarh drain and Garhi Mandu, contains several types of pollutants. The project report identifies high levels of total dissolved solids, fluoride, nitrate, iron and manganese. It also reports heavy metals, including arsenic, lead and mercury.

These substances matter because the groundwater is not suitable for direct human consumption. The problem is not only high salinity. The water may contain multiple contaminants at the same time, requiring treatment systems that can address dissolved salts, metals and other pollutants together.

The DJB therefore wants treatment technology capable of handling TDS levels up to 10,000 milligrams per litre or higher. Providers must show that their systems can produce water meeting WHO and BIS drinking-water norms. The proposal also requires attention to recovery and reject-water management. This makes the project a combined water-treatment and waste-management challenge, rather than a simple groundwater-extraction plan.

Reverse osmosis and nanofiltration are membrane-based treatment methods. They push water through a very fine barrier that allows treated water to pass while retaining many dissolved salts, metals and other contaminants. The exact removal performance depends on the water and system design, so the DJB is asking providers to demonstrate proven solutions.

For example, groundwater from a tubewell could enter a treatment unit with TDS as high as 10,000 milligrams per litre or higher. The membrane process would produce a treated stream and a concentrated reject stream. Additional treatment steps or a combined technology package may be proposed if needed to meet WHO and BIS drinking-water norms.

The DJB has invited capacities from 10 MGD to 50 MGD or more, using modular designs that can expand. It also wants high recovery, meaning less extracted water is lost during treatment. The proposal must include a plan for the concentrated reject water, because removing pollutants does not make them disappear.

When treatment removes dissolved salts and heavy metals, those substances collect in a smaller, more concentrated stream called reject water. It is separate from the treated water intended for supply. The article does not state that this stream will be discharged, reused or disposed of in a particular way.

The mechanism is straightforward: membrane systems allow part of the water to pass as treated output, while much of the retained material remains in the water that does not pass through. Higher recovery can reduce the volume of reject water, but the remaining stream can contain concentrated pollutants. Its handling therefore needs careful planning.

The DJB says proposals must maximise recovery and provide a plan for managing concentrated reject water. This requirement is important because a treatment plant could shift contamination from groundwater into a difficult waste stream. The article does not identify the eventual management method, site or regulatory arrangement. Those details would need to be resolved before large-scale operation.

An aquifer is an underground water-bearing formation that stores groundwater and allows it to move through connected spaces. Wells and tubewells draw water from these formations. In this proposal, the DJB wants to tap aquifers in places such as areas near the Najafgarh drain and Garhi Mandu, then treat the extracted water.

Pumping can add a source during shortages, but groundwater is not automatically unlimited. If water is removed faster than the aquifer is replenished, groundwater levels can fall. Wells may then yield less water, and pumping can become more difficult or costly. The article focuses on treatment quality, so it does not provide Delhi-specific recharge or depletion figures.

The DJB’s plan includes 300-400 tubewells, making long-term monitoring important. Authorities would need to track groundwater levels and quality while managing extraction and treatment. The proposal could help supplement supply, but its lasting value depends on whether pumping remains sustainable and whether treated water continues meeting required standards.