A robust metering infrastructure is important for strengthening the water distribution segment. Efficient metering practices such as effective water management and reduction in non-revenue water (NRW) help improve the financial health of a utility. These practices not only help create an efficient billing and collection network but also increase consumer awareness on water conservation.
Utilities usually switch to advanced metering solutions to reduce the percentage of NRW, which primarily consists of commercial and physical losses. Several issues such as non-metering, incorrect billing and illegal connections, legal but uncharged connections and treatment work losses (like backwash, transmission and distribution mains cleaning) can lead to commercial losses. Meanwhile, transmission losses, service reservoir leakages and overflow, and losses in distribution networks lead to physical losses.
There are various metering solutions to ensure round-the-clock water distribution. However, some emerging instrumentation techniques help provide 24×7 water supply.
One of the most common instruments used for measuring the amount of water passing through a pipe is the water flowmeter. These flowmeters can be used for domestic and industrial water measurement applications of both clean and dirty water. There are different flowmeter technologies suitable for different situations. Each water flowmeter offers certain benefits, has a unique operation principle and possesses specific attributes. There are primarily five types of flowmeters available, which are mentioned below:
- Electromagnetic flowmeter (or magmeter) is a device that does not have any moving parts. These flowmeters have the ability to measure a wide range of difficult-to-meter fluids such as corrosives, slurries and sludges and operate in applications with low pressure drop, which sets them apart from other flowmeters. They are used across industries like waste and water, pulp and paper, mining, chemical, and food. However, magmeters cannot be used for liquids having electric conductivity of less than five microSiemens per centimetre (µS per cm).
- Ultrasonic flowmeter is a non-intrusive device that uses sound waves for determining the speed of a fluid that flows through a pipe. These flowmeters are highly accurate and have an accuracy level of ±0.5 per cent to 1 per cent of the flow. The repeatability of measurements with these devices is also strong (± 0.05 per cent of flow). Another benefit of this technology is that there are clamp-on versions available, which can be attached to the outside of a pipe. However, ultrasonic flowmeters can be cost intensive and could have interferences from pipe walls when using clamp-on models.
- Mass flowmeter (or inertial flowmeter) is a device that measures the mass flow rate of the liquid passing through a pipe. The mass flow rate is the mass of the liquid travelling past a fixed point per unit of time.
- Bypass rotameter is the most cost-effective solution used for flow measurement in large pipelines and large rate of flow. However, its use is limited to solid particles and semi-liquid mixtures that tend to clog the openings.
- Vortex flowmeter operates under the vortex shedding principle, where an oscillating whirlwind occurs when a fluid such as water flows passes a bluff body. It is used in industries requiring low maintenance.
As far as water application is concerned, the best-suited technique is electromagnetic flowmeters since they cause no obstruction (due to the lack of moving parts), are maintenance- free and highly accurate. Another instrumentation technique available is the level meter. It is used to measure the water levels in piezometers, and to monitor wells and boreholes. There are several types of level meters like ultrasonic level meters, radar level meters, level switches and level gauges. In case of water application, radar level meters are the most preferred. They can perform all functions with one model catering to the demands of the entire plant. This technology also offers unmatched reliability.
Apart from flow and level measurement technologies, there are many pressure measuring instruments as well. These include pressure gauges, non-smart pressure transmitters, smart pressure transmitters, special gauges for slurry and sludge, and pressure switches. Owing to their unmatched reliability and ability to perform functions in a simple manner, non-smart pressure transmitters are the best for water applications.
Apart from providing round-the-clock water supply, ensuring and maintaining water quality are also crucial. To this end, there are various water quality analysers such as PH meters (measures acidity of water), conductivity meters (measures electrical conductivity), turbidity analysers (checks the presence of organisms suspended in liquids), chlorine analysers (measure the chlorine levels in water), true biochemical oxygen demand (BOD) analysers, sludge-level analysers and online chemical oxygen demand (COD)/BOD/ PH/total suspended solids analysers. In addition, there are vibrations monitoring systems that facilitate the monitoring of rotating machinery like turbines, compressors, pumps, fans, motors and gearboxes. This technology is primarily used for preventive maintenance of machines to reduce maintenance costs. There are acceleration, velocity and eddy current sensors with monitoring systems as per API 670 standards. Apart from this, there is an interface with applications like the supervisory control and data acquisition (SCADA) system, digital control system, programmable logic controller (PLC) and an analysis system for better monitoring of systems through data management.
To ensure data transmission reliably, quickly and cost effectively, several telemetry devices can be used. These include internet of things (IOT)- based systems, modems, machine-to-machine terminals, PLC and remote terminal units. Effective implementation of IoT architecture helps reduce the need for skilled manpower and the cost of SCADA maintenance and upgrades, as well as saves the utility from superior follow-up support. Several utilities have adopted smart technologies to promote water management.
In order to provide better control to water authorities, another emerging solution is water management software. It manages water permits and regulatory requirements, and provides a single location to track water discharges and its sampling logs. Keeping in view that water management involves various different stakeholders, the software is a three-tier system with stakeholders like operator, asset care manager and the plant head. The software sends alerts related to the equipment’s health, its accurate maintenance and diagnosis for in-time actions to the operators. In addition, it sends alerts to the asset care manager to track the effectiveness of maintenance and planning and to keep a tab on inaction on the part of the operator. The software also provides the plant head with an overall utility overview by sending alerts related to safety, production and efficiency.
Several utilities have transitioned to or are expected to move towards advanced metering infrastructure to improve their water distribution networks. In 2009, the Delhi Jal Board (DJB) initiated its transition to facilitate better water audits by installing bulk flowmeters only at the sources of water. BWSSB and the Pune Municipal Corporation (only pump stations) also have flowmeters in place. Over the next two to three years, various utilities including DJB, the Brihanmumbai Municipal Corporation, and the Chennai Metropolitan Water Supply and Sewerage Board are expected to install flowmeters in various stages of their distribution networks.
With the emergence of advanced technologies, several new metering solutions have come to the fore. As a result, many urban local bodies have started taking cognisance of these technologies and are adopting them to improve and strengthen their water distribution networks to ensure round-the-clock water supply. The key metering solutions are flowmeters with advanced technologies like electromagnetic flowmeters and ultrasonic flowmeters, level meters like ultrasonic and radar level meters, water quality analysers, and SCADA and telemetry devices. In addition, there is analysis and customised water management software catering to the specific needs of stakeholders.
In sum, these emerging solutions not only help in effective water management and reduction of NRW, but also facilitate the creation of an efficient billing and collection network through automation.
With inputs from a presentation by Neville Bhasin, Consultant and G. Prasanna, Industry Manager (Water), Forbes Marshall Private Limited, during the India Smart Grid Week 2018