Two years ago, I visited the Central Park South apartment complex in Old Mahabalipuram Road (OMR) to observe and write about its in-house Sewage Treatment Plant (STP). While large apartment complexes are required to have the facility to treat their sewage, many in Chennai lack one. Unlike other buildings in OMR, Central Park South had little choice, as the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) has yet to provide essential services like drinking water and underground drainage.

I revisited the apartment this month, eager to see how the sewage treatment system had evolved. While it has had a functional STP for quite some time, the residents have stepped up their efforts in the last two years — optimising their online monitoring system to minimise human intervention and taking proactive steps in maintenance. This has helped them save more than 1.9 crore litres of fresh water every year.

Keeping an STP self-sustaining isn’t an easy task for residents. So, how did they do it? Here’s what they learnt and how their journey can help other apartment complexes achieve the same success.

Here is a guide to set up a self-sustaining STP in your apartment.

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Maintenance is the key

Challenge:

As highlighted in our 2023 article, the major challenge of managing an STP lies in its maintenance, which can be expensive. This involves a continuous power supply, hiring staff, and budgeting for their salaries. 

Rakesh Ohri, President of the Central Park South Owners Association, emphasises that understanding the STP’s functioning is crucial. Many resident welfare associations (RWAs) outsource the task of managing the STP and overlook the importance of understanding its components and operational needs.

Solution:

As a solution to this challenge, he says, “We have made an effort to understand how the STP functions, its components and other materials required to keep it running. We do not cut corners on maintenance or compromise on the quality of the materials used,” he says.

One common mistake many apartment complexes make is trying to save money by turning off essential systems. For instance, the aeration tanks in STPs require blowers to keep bacteria alive during the night when wastewater inflow decreases. Turning off the blowers to save electricity can delay the bacterial process and affect the overall treatment efficiency the following morning. Though this approach increases power consumption, that extra rupee spent to not disturb the process is where the key to maintenance lies, adds Rakesh.

As per the GST rules, if the monthly maintenance exceeds ₹7,500 per member, and the RWA’s total turnover is over ₹20 lakh, GST of 18% is levied on the full amount. However, Rakesh, who is also one of the co-founders of Federation of OMR Resident Associations (FOMRRA), notes that these societies are non-profit bodies and the office bearers work as pure agents (meaning they work without any pay). Thus he urges the government to exclude essential services like electricity, water, and diesel (for generators) from the GST calculation in maintenance charges for RWAs.

The challenge in hiring qualified staff

Challenge:

Another significant challenge faced by many RWAs is retaining qualified staff and contractors.

Solution:

Rakesh says that they have not faced many issues in retaining staff as they pay their staff well and take care of them. Approximately, the apartment complex spends ₹4 lakhs per month, including all costs of salary and maintenance for the STP.

To ensure quality, he says, “We do not involve any middlemen. We also keep a direct relationship with the vendors for purchasing all the materials needed for operating the STP.”

Moreover, their hands-on approach to understanding the STP has enabled them to closely monitor contractors and intervene when necessary.

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The financial and environmental benefits of STP

All the recycled water is used for flushing and gardening purposes. For residents, the most tangible benefit of the STP is the quality of water. According to B Barathan, a resident of Central Park South and secretary of the Owners Association, the treated water is of excellent quality, with no complaints about discolouration.

In terms of cost savings, the apartment complex has seen substantial financial and environmental benefits. Here’s what they save:

By recycling their wastewater, Central Park South saves approximately ₹9.16 lakh annually. The biggest benefit is that all the grey water is diverted from being dumped into water bodies.

Optimising the online monitoring system of STP

In addition to ensuring the STP’s physical maintenance, Central Park South has also optimised its online monitoring system. Though they had the system even during my last visit in 2023, they have taken measures to optimise and include more components in their online monitoring system.

This improved monitoring system allows the apartment complex to manage its STP more effectively, with minimal human intervention. As Rakesh puts it, “The key is to have the right people in the right roles to manage the system effectively.”

Also read:

• Within GCC limits since 2011, Thoraipakkam still waiting for piped water and sewage system
• Explained: Metro Water’s new plans for using treated water from TTRO plants