India has come a long way in the past decade as far as treatment of sewage is concerned. The country has undertaken various initiatives and has established over 1,000 sewage treatment plants (STPs). The construction of STPs is usually financed by urban local bodies (ULBs) through grants and subsidies sponsored by central and state government schemes, and revenue generated from the sale of the treated water. In order to efficiently operate and manage their water and wastewater infrastructure, these civic bodies outsource the operation and maintenance (O&M) of STPs. Earlier, ULBs used to award O&M contracts for a shorter tenure of two to three years. However, with the emergence of advanced technologies and growing expertise in operations, O&M contracts are now awarded for over 15 years. The uptake of newer technologies allows the concerned authorities to closely monitor different operations in the STPs.
Water utilities in Chennai and Bengaluru have followed the model of third-party O&M contracts. The Koyambedu STP Zone III plant is run by the Chennai Metropolitan Water Supply and Sewerage Board, and its maintenance is handled by Detech. The Thoothukudi City Municipal Corporation has awarded the O&M contract for a 24 mld wastewater treatment plant in the public-private partnership mode to VA Tech Wabag Limited and a consortium of Operational Energy Group Private Limited and South Ganga Waters Private Limited. Meanwhile, the O&M of the Sarai STP, Haridwar, which has a capacity of 14 mld, has been awarded to HNB Engineers till 2035. In August 2021, Toshiba Water Solutions won a contract to construct an STP in Hajipur, Bihar. The project involves construction of the STP and its O&M for 15 years.
Digital solutions for STPs
Supervisory control and data acquisition (SCADA) systems enable remote monitoring of water supply distribution systems and their various process parameters such as water quality (pH, turbidity and residual chlorine), process variables (flow level and pressure) and control elements (electric actuators for valves). Treatment plants in various cities are now being monitored through SCADA. The Ahmedabad Smart City has installed a SCADA system for real-time monitoring of its water treatment and distribution system. The project has been set up to cover three water treatment plants and 148 water distribution stations. It will monitor the quantity and quality of water supplied in various areas. In another development, the Pimpri Chinchwad Municipal Corporation has brought all the STPs in its jurisdiction under a central monitoring system. This SCADA system monitors the entire sewerage network, comprising 13 STPs and 33 pumping stations. A master control room has been set up with engineering and operator stations. The installation of the centralised SCADA system involved a total investment of Rs 42 million.
The Okhla STP is being developed as an integrated plant that will not only treat sewage, but also have a complete sludge management facility. The plant will have the largest ultraviolet disinfectant system in the country for the removal of faecal coliform from water. It will be fully automated with a SCADA system. Meanwhile, Bengaluru has been using a SCADA system for its water network for several years. It monitors data from the water supply facilities of the Bengaluru Water Supply and Sewerage Board, such as pumping stations, water and wastewater treatment plants, and reservoirs.
Bhopal Smart City Development Limited has undertaken the initiative to install a technology-enabled SCADA system as part of the comprehensive Bhopal city water utility SCADA management project. This system will monitor water treatment plants and overhead tanks for the optimal utilisation of water resources. In Naya Raipur, a computerised water billing software (PLC-SCADA mode) has been deployed for accurate measurement, billing and collection of water charges. Further, at the water intake level (from the river), the city’s water pumping system has been automated to generate real-time data on the number of charges of pumps, pressure applied and the flow of water. Meanwhile, Nashik Municipal Smart City Development Corporation Limited has plans to implement SCADA and automatic meter reading/advanced metering infrastructure meters in the city. With this, the water supply will be monitored from the start point (water treatment plant) to the end point (consumers).
GIS, GPS and RFID
Geographic information system (GIS) technology is designed to capture, store, manipulate, analyse, manage and present all types of geographical data. Meanwhile, radio frequency identification (RFID) tags, installed at sewage collection points, read information about collection vehicles and send alerts to the sewage collection authorities.
The Kerala Water Authority (KWA) has come up with a new tool using GIS for optimal site selection of STPs. It is undertaking a study to find the most optimal sites for STPs using the GIS-based multi-criteria analysis in Elamkulam, Kochi. GIS and management information systems are also being deployed in Vara nasi to effectively monitor the city’s civic infrastructure, such as the water supply and sewerage network, and improve the financial and operational performance of the ULB.
In January 2021, a Delhi-based tech start-up, Onelap, was appointed as a GPS tracking service provider to the Chumukedima Municipal Corporation. With the help of GPS tracking services, the ULB will be able to manage its waste and sewage more efficiently. Meanwhile, the Jabalpur Municipal Corporation has established a collection and transportation system through private sector participation to refine sewerage management in the city. Jabalpur, in one of its major IT initiatives, implemented RFID and bin-level sensor tracking for better monitoring of waste and sewerage collection vehicles.
Ultrasonic flowmeters are volumetric flowmeters that require particulates or bubbles in the flow. This makes them ideal for wastewater applications. The Bellandur STP, developed by BWSSB, has a capacity of 60 mld. The STP uses flowmeters to monitor the flow rate and ensure the efficiency of treatment operations.
Another widely deployed method is the fibre optic method, wherein leak detection sensors are installed along the exterior of the pipeline system of an STP. In Vadodara and Mumbai, sound-based sensors for leak detection in STPs are being implemented. Meanwhile, the KWA has adopted the Sahara drag chute and SmartBall leak detection technologies for easier and more effective detection of leakages.
One of the key reasons for the poor O&M of STPs in the country is the lack of funds for maintenance activities due to the lack of a structured approach to estimating O&M fund requirements. It has been observed that O&M activities carried out by private contractors have been quite satisfactory, but O&M conditions in some of the treatment plants maintained by public health departments have been below par due to the lack of funds and interest. Another issue faced by treatment plants is the absence of a designated chemist, which is a prerequisite for efficient functioning of a treatment plant. The lack of proper and regular training and a skilled staff for carrying out O&M works for plant operators is yet another persistent issue.
Newer technologies such as artificial intelligence (AI), machine learning (ML) and digital twins are emerging as advanced tools for efficient O&M practices in the water and wastewater sector. However, these technologies are still at a nascent stage in India and their implementation by ULBs has been limited.
AI is becoming a cost-effective solution, giving rise to an increasing number of use cases, from healthcare to wastewater treatment. It is handling the heavy lifting of repetitive, time-consuming tasks in treatment plants. When it comes to the wastewater treatment process, AI can address sludge expansion problems, and help in improving aeration and pump efficiency. ML is a subset of AI, under which an algorithm is trained to detect abnormal data patterns (or correlations of patterns) regardless of whether the control thresholds have been breached. With ML, algorithms are looking for behaviour patterns even within the thresholds.
Another emerging technology in the O&M of STPs is digital twins. Digital twins facilitate virtual representations of assets, processes and environments, which can be used for real-time monitoring, predictions and automated responses. The technology understands and interprets demand, flow and performance so that the operator can put those insights to work to mitigate risk, cut costs and ensure that it is taking the most efficient approach to wastewater management.