Since water and wastewater treatment processes account for 4% of global electricity consumption, it’s vital that reducing energy consumption is in focus for industrial and domestic wastewater treatment. Fortunately, there are cost-effective and energy-efficient solutions that can reduce energy consumption in the water sector, especially at wastewater treatment plants.

Even in the best conditions, wastewater treatment requires energy-intensive processes. At the Koyambedu wastewater treatment plant in Chennai, India, this includes aeration for removing dissolved organic matter and nutrients. Because of that, aeration is the principal energy-guzzling process in wastewater treatment, representing half the cost of total wastewater treatment, followed by biosolids processing and pumping.

Due to the high pumping requirement of the plant, energy consumption is already high. To make matters even more complicated, the extreme temperature and humidity in Chennai also lead to high heat dissipation from the motor panel room, contributing to high load on the control room cooling system. This required a bigger HVAC system which consumed more energy, resulting in higher energy bills.

The Koyambedu Tertiary Treatment Reverse Osmosis plant, which was designed and built by VA Tech WABAG Ltd, is one of the most advanced wastewater treatment plants. Advanced pre-treatment with dual media rapid gravity filter, wastewater polishing using a state-of-the-art ultrafiltration system, and a 3-stage reverse osmosis system are all key to achieving the excellent overall recovery of 80%.

These measures all help save over 16 billion litres of fresh water every year. With a throughput of up to 45 million litres a day, this also means that the plant faces high energy consumption. Therefore, to improve the energy efficiency of its operations, the Koyambedu wastewater treatment plant implemented variable speed control using VLT® AQUA Drive FC 202 units from Danfoss. This has resulted in more than 700,000 USD savings in running costs over 15 years of operation.

This method of cooling greatly reduces the ingress of airborne contaminants in the control electronics area resulting in longer life and higher reliability. The remaining 15% of heat losses are removed from the control electronics area using lower-volume door fans. The robust design and efficient monitoring significantly reduce maintenance requirements.

Due to the back-channel cooling, the Koyambedu wastewater treatment plant selected a 30-ton air conditioning unit, instead of using an air conditioning unit weighing more than 80 tons. This reduced the capital expenditure of the plant by more than 130,000 USD and reduced the energy bills leading to a reduction in operational expenses. Back-channel cooling reduces energy consumption by 22%, leading to more than 700,000 USD savings over the application lifetime.