NRW Loss Reduction

Strategies for better water network management

Urban local bodies (ULBs) in India have reported very high levels of non-revenue water (NRW), which accounts for at least 50 per cent of their water supply. NRW  includes water that is lost due to leakages in transmission and distribution networks; consumption that is authorised but not billed (public stand posts for instance); and losses owing to illegal connections and metering inaccuracies. To reduce NRW losses, ULBs need to improve network management and modernise their metering infrastructure. Some of the ULBs have acknowledged these issues and adopted water network management systems with smart distribution and automation mechanisms to reduce their water losses. Some of the key drivers for better network management are increasing levels of NRW, expanding customer base, need for sustainable assets and better cost recovery, and greater service-level requirements, among others.

Strategies for network management

A prerequisite for efficient network management is accurate measurement of water consumption. This requires proper planning and design in order to map the existing infrastructure and assess the current supply and demand requirements through consumer surveys. Further, continuous water supply needs to be maintained by controlling water pressures and optimising operations and maintenance of the system to ensure regular leakage repairs, pipeline replacements, and efficient metering and billing.

Primarily, there are four strategies to reduce water losses that also help improve water network management. These are pressure management, command and control, leakage management, and metering and billing.

Pressure management: One of the ways to manage water pressure is to install pressure transmitters at critical monitoring points (CMPs). CMPs are the farthest located points from the overhead tanks, or the highest elevation points in a district metered area. They are equipped with GPRS connectivity. Once the CMPs are fitted with transmitters, the collected pressure data is transferred to the central server on an hourly or daily basis.

Besides, pressure regulating valves can be used to manage and control the water pressure. The most commonly used regulating valves are advanced hydraulic pressure regulating valves and advanced electronic pressure regulating valves. The advanced hydraulic valves help reduce the higher inlet pressure to a usable outlet pressure, in accordance with a prior set pressure value. Hydraulic valves keep the system from being over-pressurised by maintaining the pressure as per the demand, while ensuring an adequate and required flow. On the other hand, the advanced electronic valves are connected to an electronic controller, which is preloaded with a flow/pressure profile. These valves can be easily fitted into the supervisory control and data acquisition (SCADA) system, which allows remote adjustments to the pipeline pressure level.

Command and control: For the smart command and control of water systems, utilities can install SCADA and a web-based integrated management information system (IMIS), which serves as an online customer redressal system. The SCADA system allows utilities to remotely monitor the water supply system, and ensure accurate data collection and efficient management of historical data. Parameters such as the flow and pressure of a pipeline can also be remotely assessed from the control centre. It is used by utilities not only to monitor the water flow but also to automate water treatment plants. The web-based IMIS creates a user-friendly online interface for consumers for a two-way communication. It helps in building customer confidence through an efficient complaint redressal mechanism and reduction in the response time for leakage repairs.

Leakage management: ULBs have adopted different types of technologies for leakage detection. These include helium gas, water leak sensors, and SmartBall (accelerometer and gyroscope technology). Some of the most commonly used methods for leakage detection are based on sound technology. In this technology, equipment such as listening sticks/acoustic sticks, acoustic noise loggers, leak noise correlators and ultrasonic flow meters are deployed for monitoring distinct noises resulting from leakages.

Acoustic leak detection technologies use sound waves to help locate leakages in distribution systems and prioritise leak repair by identifying the largest leaks. The acoustic sticks are used for metal and non-metal pipelines. These sticks transfer the leak noise to the human ear. Besides, noise loggers are a specific type of acoustic leak detection equipment. They comprise a listening head and a digital recorder in a single sensor. They can be attached magnetically to the distribution system (key junctions, main valves or hydrants). They can be left in a fixed place for extended periods or moved as needed to record noise levels and detect leakages. In addition, the leak noise correlators are particularly used to pinpoint areas of suspected leakages. It is one of the more advanced technologies for leakage management are ultrasonic flow meters. They are non-intrusive devices that make use of sound waves for determining the speed of a fluid that flows through a pipe. They are highly accurate with an accuracy level of ±0.5-1 per cent of the flow. They are mounted on valves and other fixtures to identify leakages. However, ultrasonic flow meters can be cost intensive and have interferences from pipe walls when using clamp-on models.

Metering and billing: A robust metering and billing infrastructure is crucial for strengthening the water distribution segment. Automatic meter reading (AMR), advanced metering infrastructure (AMI) and LoRa water meter sensors provide advanced metering solutions to utilities. AMR meters are used to track water consumption. The consumption data is transferred from the electric meter to the utility (one-way communication) for billing, troubleshooting and analysis purposes. AMI is an integrated system of smart meters, communication networks and data management systems that enables two-way communication between ULBs and consumers. AMI facilitates real-time meter reading, thereby enabling utilities to record daily/hourly data. LoRa water meter sensors are radio communication devices. As they have low power but a long range, LoRa meters are used in combination with AMR meters or AMI. The water consumption data collected is sent to the LoRa gateway, which is generally within a distance of 1 km from the module.

Data encryption is handled by the LoRa module and data is then sent to the gateway. Further, the gateway transfers the data to the central control room through the internet. The central control room collects the data from all local gateways and decrypts the data using the network server. The decrypted data is later processed through analytical software.

Conclusion

Going forward, ULBs are required to actively address the NRW issue by controlling physical losses, ensuring customer meter accuracy and making efforts to reduce the number of illegal connections. These measures will help boost their revenue by increasing the amount of billed water while reducing any wastage of the resource. In this regard, the need for greater automation and smart technologies for NRW reduction cannot be overlooked. The private sector is also likely to play a key role in water network management in the coming years.

With inputs from a presentation made by J. Venkatesh, Senior Deputy General Manager and Head, Water Management, Water Supply and Distribution, L&T Construction, at the Non-Revenue Water Conference 2018

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