Energy efficiency continues to rise up the agenda for water companies. Not only are energy costs significant, but consumers have become more environmentally aware. Moreover, regulatory and government policies such as the Carbon Reduction Commitment demand that attention is focused on energy consumption. It is likely that reporting greenhouse gas emissions will become mandatory for organisations in the sector within the next year.
To report, manage and reduce emissions better, most water companies have already established carbon management plans. But improving the energy efficiency of water assets and operations is not an objective to be treated in isolation – it should go hand in hand with measures aimed at broader improvements, such as risk mitigation or saving costs.
Improvements to mechanical and electrical equipment and processes offer a prime opportunity to improve energy efficiency while also delivering operational and cost benefits, and there are a number of quick win measures that companies in the water industry can take.
Some of the greatest energy efficiency improvements can be secured by addressing principal energy-consuming processes, in particular aeration – dissolving oxygen into water to improve its quality. The driving force for developments in aeration technology is the goal of optimising standard aeration efficiency (the amount of oxygen transferred per energy unit). Aeration was generally achieved by the use of fine bubble diffusers, but in recent years surface aerators have been shown to offer better performance and economics.
For example, in a recent project, Deritend addressed the fact that aeration consumed approximately 80 per cent of the total energy used in one major water company’s sewage treatment operations. It surveyed one large site and proposed replacing the existing jet aerators with slow-speed surface aerators to improve the efficiency of the aeration process in four cascaded tanks.
The new aerators are conical in shape, which creates a pump function, pumping up water from the lower parts of the tank. Water reaching the surface has a high oxygen deficit, making the transfer of oxygen relatively easy, and the process is much more efficient than using comparable flat plate aerators.
The result was a dramatic reduction in energy consumption, not only reducing the environmental impact of operations on the site, but also providing annual
savings of £37,000.
There are a host of other asset management-based opportunities available to water companies to lower their carbon footprint while increasing operational efficiency and saving costs. These include:
· the application of high-efficiency motors to increase productivity;
· improved, co-ordinated maintenance programmes to improve operational efficiency and prevent failures;
· failure mode effect analysis and reporting, to monitor and manage cause and effect.
Asset management can offer water and wastewater companies simple opportunities to reduce carbon consumption and greenhouse gas emissions while also providing broader business benefits, and it should form a key element of water organisations’ carbon management strategies.
Dave Hawley is divisional director of mechanical and engineering site services at asset management specialist Deritend
This article first appeared in Utility Week’s print edition of 21st September 2012.
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