Connecting Waterpeople

Balancing power consumption and the goals of water treatment: A UV-centric perspective

  • Balancing power consumption and the goals of water treatment: UV-centric perspective

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SWM Bimonthly frontpage

About the blog

Dr Assaf Lowenthal
Senior Scientist, Atlantium Technologies Ltd.
Schneider Electric

UV technology is considered environmentally friendly because it is chemical free. In most cases, it is a minor power consumer in comparison to the overall electrical demand of a water treatment facility. Still, operators that wish to reduce the power consumption, may have the option to do so with slight modifications, as suggested in the next paragraphs.

UV technology is mainly known for its role in the disinfection of pathogens in potable water, where disinfection standards are determined by environmental and health authorities. In such cases, there is little margin for reducing power consumption mainly since the design must comply with regulatory constraints, but also since the required UV dose is usually low to begin with.

In other processes, the goals of a UV treatment are determined by the user and are based on performance. For example, in aquaculture, the goal of UV is to decrease the mortality rate of fish due to infectious diseases. In RO membranes, the goal of UV is to minimize the accumulation rate of biofouling on the membrane and the consequent decline in performance. In these two cases, there is no regulatory body to determine the optimal dose for the process. The optimal UV dose is determined by pilot studies, usually carried out in collaboration between academic researchers, the UV industry, and the end user. Clients are often unfamiliar with the subtleties required for the determination of the UV dose that their process requires and may purchase an oversized system.

The challenge of a sustainable UV system is supplying clients with their requirements while maintaining power consumption to the minimum

The challenge of a sustainable UV system is supplying clients with their requirements while maintaining power consumption to the minimum. One solution is to give the client the option of choosing between two operational modes: high-risk and low-risk. A high-risk mode would supply maximum protection and consume more power. The user may choose this mode during seasonal events such as the appearance of specific pathogens in aquaculture, the appearance of algal blooms or increased organic load in RO facilities. Low-risk mode consumes less power (at least 30% less than high-risk) and provides a standard level of protection. This mode is suitable for standard operating conditions when preventive maintenance (such as CIP) is carried out on schedule and there are no indications of a high microbial load.

A risk-based approach would save power expenses, which may add up to $4,000 per year in a 100 m3/h system. An operational mode feature already exists in some UV systems and can be easily operated by the user.

In addition to disinfection, UV technology is also well established in the context of treating water polluted with chemical contaminants using advanced oxidation processes (AOP). Each contaminant has its own cleanup goal (the concentration of the contaminant after treatment), which is often defined as below the detection limit of the standard method. Many AOP projects begin before a final regulatory framework has been laid. One aspect of the framework is the determination of analytical methods, which may vary from one lab to another. For example, in New York, 1,4 dioxane is treated to below detection limit, which can be 0.02 ppb in one laboratory, and 0.07 ppb in another. Assuming initial concentration of only 1 ppb, this difference accounts for a 32% increase in power consumption, which can easily translate into over 20 megawatts per year in a site with a flow rate of 50 m3/h.

Another feature of AOP projects is that the contaminant concentration slowly drops during the period of the activity. A UV-AOP system that can adjust its power consumption according to changing requirements can save the client operational costs and increase the sustainability of the project.

In summary, to guarantee uncompromised performance while maximizing electrical efficiency, a sustainable UV system, either for disinfection or AOP, should be able to adapt its power consumption according to varying water quality, and the operational and regulatory framework.

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