Wastewater: The key to meeting Delhi’s drinking water demand

Out of 530 million gallons of treated wastewater produced by Delhi’s 20 sewage treatment plants every day, the city is currently able to utilise less than 20% (90-95 MGD) in areas such as Sanjay Van and Bhalswa golf course, and as a coolant in power plants.

A senior Delhi Jal Board (DJB) official said that while water utility is obligated to release 267 MGD of the treated wastewater into the Yamuna to maintain the return e-flow, the utilisation of the rest of the water will shape the course towards a water-sustainable city.

“We are planning to re-utilise the highly treated sewage water to plug the demand-supply gap through four key projects — through water exchange with neighbouring states Uttar Pradesh and Haryana, by deploying the Singapore new water model in Palla, and through the revival of dying water bodies,” the official said.

Ankit Srivastava, the technical adviser to the Delhi government in the water sector, said that most of the wastewater re-utilisation projects are expected to start yielding results in two to three years.

“Wastewater re-use will be crucial in meeting the city’s demand, and many projects are in the advanced stages of negotiation and implementation. In the case of the Singapore model project, permission from the Upper Yamuna River Board has been secured, and the consultant is finalising the project. It should be up and running in three years. A large number of lakes are also being revived using wastewater, and extraction can be carried out when groundwater levels become high,” he added.

A pioneer: Singapore’s NEWater model

Singapore is a pioneer in re-utilising its treated sewage water. A tiny city-state with an area of only 710 sq km and 5.6 million people, it has become a world leader in harnessing new technologies to deal with its scant raw water resources.

Singapore mainly relies on its neighbour Malaysia for water consumption. Anticipating a crunch, the Singapore water reclamation study was initiated in 1998. The re-use of highly purified wastewater into high-grade drinkable water after a three-stage filtration process — microfiltration, RO, and UV filtration — came to be known as the Singapore NEWater model.

The country currently has five operational NEWater plants which cater to a large chunk of the water demand. A Memorandum of Understanding (MoU) was signed between Singapore and Delhi in 2012 to study the feasibility of a similar project in the Capital.

In 2015, the government tried to initiate the “Toilet to Tap” project in Keshopur, but it could not yield the desired results due to a “cultural” problem in re-using sewage water. DJB officials hope that putting the water back into the river will help overcome this hurdle.

In 2018, chief minister (CM), Arvind Kejriwal — who also held the DJB chairman portfolio — announced that, following Singapore’s NEWater model, highly purified water from the upcoming modern Coronation Pillar wastewater plant will be taken to Palla and deposited in the Yamuna.

The diluted water will undergo natural purification in the river course, then be re-lifted 11 km downstream in Wazirabad, and re-used in augmenting the water supply. Now, after being held by the Upper Yamuna River Board for two years, the work on the ambitious project of reusing highly treated wastewater for augmenting Delhi’s water supply is back on track.

Haryana objected and stonewalled the proposal based on concerns such as social acceptability. “The norms followed all over the country for releasing treated effluent [sewage/liquid waste] in the river is 20:20 BOD:TSS (bio-chemical oxygen demand and total suspended solids). We will put further treatment plants to improve water quality to BOD:TDS 3:3 level,” a DJB official overseeing the project explained. The water utility plans to add 95 MGD of raw water to its currently available resources through this project by December 2024.

Water exchange with Uttar Pradesh

Shashank Shekhar, a water sector expert and professor of geology at Delhi University said that Delhi will have to rely on treated wastewater to meet its growing needs.

“There is no doubt that this is the future. But we will have to be honest about this process, and the process of purification will have to be vigilantly guarded. Despite so many sewage treatment plants [STPs], a large portion of the Yamuna still flows as an untreated sewage canal. Putting plans in place is good, but the real test will lie in implementation,” he added. Shekhar said that process needs to be audited by civil society.

Besides re-using the treated sewage within the city, Delhi also plans to barter its treated resource with its neighbours.

Under the ₹6,931 crore project, the national Capital is planning to implement a project to exchange 140 MGD treated wastewater in return for freshwater from neighbouring Uttar Pradesh.

A feasibility report commissioned by the Uttar Pradesh irrigation department found that 270 cusecs of water (one cubic foot per second) from Ganga can be shared from Murad Nagar regulator, while the treated effluent can be released from Okhla.

“The treated water can be used for irrigation purposes while Delhi’s raw water availability will significantly improve if the project goes through. Several rounds of field inspections have been undertaken by Uttar Pradesh irrigation department and the DJB, and the proposal is now stuck with UP irrigation ministry,” a DJB official added.

The wastewater exchange with Uttar Pradesh has been placed in medium-term projects with 2026 fixed a tentative deadline. A project report prepared by the DJB states that the exchange project will require ₹3,000 crore to develop infrastructure and pump-houses to carry treated effluent to Uttar Pradesh, and another ₹2,261 crore to create a 31 km-long pipeline network between Murad Nagar in western Uttar Pradesh to east Delhi’s Sonia Vihar.

The DJB will be required to set up a 140 MGD water treatment plant at Sonia Vihar, which is estimated to cost ₹1,161.4 crore.

Water exchange with Haryana

Similar water exchange of 20 MGD wastewater with Haryana is also being pursued. The board has submitted a detailed proposal regarding 20MGD wastewater substitution for irrigation purposes at Auchandi and Jaunti regulator with Haryana.

“If the project goes through, the same amount of fresh raw water may be released to the city through Carrier Lined Canal and Delhi Sub Branch canals,” an official said.

“The matter is being pursued at Upper Yamuna River board and a joint inspection by all parties was carried out in January. If the board grants an in-principal approval, it can be completed in 1.5 years,” DJB officials said.

Environmentalist Manoj Misra from Yamuna Jiye Abhiyan said that reusing wastewater is good in principle, but Delhi should also focus on maintaining e-flow in the Yamuna.

“Without the river, the city will have no future. We should work on reducing the per capital demand as current projections are outlandish. We can achieve a water consumption of 140 litres per person per day. We have enough water, if we can manage our available resources,” he added.

Misra said that raw water resources in Delhi are mismanaged. “We lose a lot of water in the supply network. We also witness urban flooding every year. The excess run-off water during monsoons can be enough to restore water-bodies and eco-systems around them,” he opined.

Lake rejuvenation and groundwater extraction

Besides planning to use 255 MGD water for major projects, the city administration plans to divert 46.5 MGD to revive water bodies and improve groundwater levels in the city’s parched areas.

Under the city of lakes project, the DJB has taken up the work of revival of 240 water bodies to recharge groundwater. The project of ₹376 crore to revive 155 water bodies was approved by the DJB in December 2018. Of this, work for 50 water bodies has been awarded.

“We are also creating artificial lakes using treated sewage water at Pappankalan STP, Dwarka treatment plant, Timarpur oxidation pond, Rohini STP, and Nilothi STP. About 46.5 MGD of treated effluent will be utilised after due treatment to fill the lakes for recharge of groundwater. It is estimated that about 50% of 23.25 MGD of water will be available as raw water source from the extraction of groundwater by the installation of tube-wells in the surrounding areas of these artificial lakes,” a DJB official associated with the city of lakes project explained.

Delhi currently re-utilises less than 20% of its treated wastewater resources. In its report submitted for draft Master Plan of Delhi (MPD) 2041, the water utility has proposed to increase this usage to 466 MGD by 2024-25.

Jyoti Sharma, head of FORCE — a Delhi-based water conservation and sanitation organisation — said they carried out focus group discussions on the re-utilisation of treated wastewater for drinking purposes in Delhi.

“We found that people are much more agreeable to using the treated wastewater if it has been first used for groundwater recharge. Moreover, the DJB will find technical difficulties in the reverse transportation of water against the slope to Palla. The project is technically difficult,” Sharma said.

RO plants and floodplain tube wells

While the one hand, Delhi is aiming to re-use its treated wastewater, a lot of interest has also been generated in tapping the saline groundwater resources to augment the water supply.

Last month, water minister, Satyendar Jain, announced that the DJB plans to install reverse osmosis (RO) plants in areas where groundwater levels are high, but water is not usable due to high salinity. The government intends to install RO plants with a total capacity of 80 MGD in areas with saline groundwater such as Okhla, Dwarka, Nilothi-Nangloi, Chilla and Najafgarh.

“The tender for the first RO plant has been recently issued. The first phase of the installations will be completed by February 2022, while the rest of the plants should be ready before the onset of the summer season,” a DJB official said.

A series of 200 tubewells is also being installed in the Palla floodplain area to extract an additional 25 MGD water. All the 200 units will be installed by October 2022.