Real Estate | Treated wastewater could mitigate rising construction costs

Buying a house is now even more expensive. A recent study across eight Indian cities, including Bengaluru, found that prices increased by 5 percent in April-June, with the increasing rates of building cited as one of the reason.

Without compromising on quality of construction, it is possible to target one important part of this industry — water — and phase towards the more financially-viable alternative of treated wastewater. This also holds tremendous potential in terms of saving freshwater as cities grapple with rising demand, and depleting aquifers.

The construction sector consumes large quantities of freshwater; however, there is little research in India that specifies the quantity required. A 2011 study by Jadavpur University estimated that typical urban constructions in India require about 27 kilolitres (KL) per square metre. An official with the Bangalore Water Supply and Sewerage Board (BWSSB) says a house constructed on 1,000 square feet would require between 50,000 to 70,000 litres.

Freshwater is mainly sourced from on-site borewells, and private tankers that bring water pumped from elsewhere. These activities account for a large portion of Bengaluru’s overall groundwater consumption. In the harsh summer of 2019, the state government even considered a five-year ban on construction of apartments. Finding suitable water alternatives will be key for the city to avoid facing a water deficit.

Currently, builders pay between Rs 450 and Rs 1,100 per tanker-load of 6,000 litres or 6 KL (which works out to be at least Rs 75/KL) depending on the location of the construction site, and the season — prices spike during the summer, and price depends on distance between site and source. For construction of a mid-sized apartment, builders need at least five tanker loads of water every day. Even if we assume the lower estimate (Rs 450), they will need to spend at least Rs 65,000 per month on water.

The BWSSB is selling secondary treated water at Rs 15/KL, and tertiary treated water for Rs 20/KL from State-run centralised plants. Builders will be able to save considerably even if the BWSSB accounted for additional transportation charges. These tanker rates could be further reduced if a network is established linking the over 2,500 decentralised sewage treatment plants (STPs) in Bengaluru with nearby construction sites. Based on analysis of the BWSSB dashboard and the KSPCB's masterlist of around 2,500 STPs, we estimate that, currently, around 550 million litres of treated wastewater from centralised and decentralised STPs in Bengaluru winds up in stormwater channels every day.

Moreover, there are policies in place that eases the process of mainstreaming the use of treated wastewater. The Bruhat Bengaluru Mahanagara Palike (BBMP) made it mandatory to use treated water from centralised STPs for construction and directed all zonal commissioners not to approve building plans unless the applicant submits a treated water utilisation plan for construction, and proof of payment to the BWSSB for availing the facility. Further, the BBMP will provide no-objection certificates (NOC) to buildings only if they submit an undertaking about the use of treated water during construction. Building owners failing to use treated water for construction will not be given an occupation certificate.

In 2019, the BWSSB also permitted private players to sell treated water for construction. These rules underline there is a policy-level push to make treated wastewater the norm in the construction industry. But there are constraints that must be addressed to ensure that this transition can be carried out safely, and effectively.

For one, there is a lack of published standards or prescribed safety protocols for reusing treated wastewater for non-potable construction activities. This has deterred many builders from using wastewater as they are worried about it compromising their buildings' structural integrity. Moreover, water quality testing should be conducted frequently; the real-time monitoring options currently recommended by the state pollution control board are considered too expensive by apartment residents.

Finding sources of wastewater, and working out financially-viable transportation are other concerns. Since laying down pipelines is very hard to do in areas that are already developed, conveyance through tankers is more likely.

Despite these challenges, this is not a pipe dream. The case of Celeste Apartment in Mira Bhayandar near Mumbai, testifies the viability of reusing treated wastewater transported by tankers. The builder was able to save around 50 percent on the water bills and the residents could ensure ‘zero discharge’ of treated wastewater from their apartment STP.

Scaling this model in cities across India could cut down on construction costs. It serves a critically-important function of conserving freshwater when the threat of scarcity looms large.