Catalyst

Innovative technology in water: Ultraviolet light in the water treatment process

At Aqua Pennsylvania, we take seriously our responsibility of protecting and providing water services for the communities we serve. Water is Earth’s most precious resource and we know our customers rely on us to provide safe, reliable water each and every day. As such, Aqua is always looking for new and innovative ways to improve our water treatment process to best serve our customers while also protecting the environment. 

 

Source waters — whether they be surface or groundwater — have distinctive characteristics, which determine the type of treatment we select. Surface water — which includes rivers, lakes and streams, are often habitats for naturally occurring algae. By definition, an algal bloom occurs when there is a rapid increase or accumulation of algae in freshwater or marine water systems. It is recognized by discoloration of the water from the algae pigment, but might also be associated with offensive taste and odor. The Shenango River, which feeds our Shenango Valley treatment plant in the City of Sharon in western Pennsylvania, and the Neshaminy Creek, which feeds our Neshaminy plant in Bucks County in southeastern Pennsylvania, are prone to such algal blooms.

 

Algal blooms are a common issue in the water treatment process. Our operations staff are accustomed to monitoring source waters and adjusting treatment, as needed, to combat the effects of algae. The presence of algal blooms typically occurs during the changing of the seasons with the highest concentrations usually occurring in the second and third quarters of the year; however, other environmental conditions might also increase concentrations. This variability of occurrence requires diligence by our operations staff throughout the year, especially during the warmer months. For example, droughts can also cause algal blooms, as low water levels allow sunlight to easily reach streambeds and riverbeds, fueling growth.

 

The algal compounds that cause the taste and odor episodes are known as Geosmin and MIB (2-Methylisoborneol). Previously, Aqua Pennsylvania relied on the application of powdered activated carbon at both treatment plants to mitigate the taste and odor associated with the presence of algae. The fine pieces of carbon attract compounds like Geosmin and MIB, which are then filtered out of the water, reducing unpleasant taste and odor. This technique, while effective, did not completely remove the compounds and created a waste stream, which is the spent carbon removed from the treated water.

 

Unfortunately, the more the powdered activated carbon was used, the more waste was created, which needed to be filtered out and sent to a landfill. Also, because this process did not efficiently remove the compounds, we were still left with a small, but noticeable, taste and odor threshold. It was clear to us that the time had come to innovate our water treatment process with a new technology.

 

In 2010, Aqua Pennsylvania partnered with an engineering firm that recommended the addition of the ultraviolet light-hydrogen peroxide treatment process at our Neshaminy plant to complement or reduce the use of powdered activated carbon. We ultimately selected the Trojan system, which was installed at the plant. The new treatment called for hydrogen peroxide to be added to water, immediately followed by exposure to ultraviolet light. The UV light reactor is a chamber with many long ultraviolet lightbulbs inside. The water and peroxide flows through the chamber while the ultraviolet light is turned on, causing a reaction that oxidizes, or removes, the compounds that affect taste and odor as well as the peroxide. This new process offered us exactly what we were looking for – a more effective way to remove Geosmin and MIB.

 

The UV process proved to be much more effective, removing 90 percent of the Geosmin and MIB compounds present, as opposed to about 50 percent removed using powdered activated carbon. Customers now receive better-tasting water which, after ensuring its safety, is our ultimate goal.

 

Another benefit of using UV-peroxide is that there is no increase in residual production. Adding hydrogen peroxide to water prior to exposing it to the UV light does not create excess solids or particulates that would increase residual waste byproducts. The use of powdered activated carbon created one-and-a-half tons of dry solid waste daily, compared with UV-peroxide, which creates none. In turn, the UV-peroxide process is better for the environment and reduces our carbon footprint.

 

After seeing the success at the Neshaminy plant, we knew the treatment would work well at the Shenango plant where we had similar algal issues. In 2013 and 2014, we completed the design and installation of this treatment process at our Shenango Valley water treatment plant and have experienced excellent results and customer satisfaction.

 

While we initially adopted this technology for taste and odor concerns, we are now exploring its use to address algal toxins as well as for additional disinfection in both drinking water and wastewater. This technology is so impactful and effective that it can be used for several important purposes in the water treatment process.

 

Another UV-light treatment application selected by Aqua Pennsylvania was to meet changing regulations for a well station in southeastern Pennsylvania. In 2009, the U.S. Environmental Protection Agency issued a new regulation to improve water quality and provide additional protection from disease-causing microorganisms.

 

The Groundwater Rule basically requires that public drinking water have a higher level of disinfectant as it leaves the treatment process and travels throughout the distribution system. This is typically accomplished by adding storage to the treatment process so that the treated water can remain for a longer period of time in the disinfection process before delivering it to our customers.  At one of our well stations, we did not have the space to install storage that could hold the disinfected water long enough to comply with the regulation. Instead, we installed UV light, which provided immediate compliance. At the time of the installation, it was the first time UV light was used for compliance with the Groundwater Rule in Pennsylvania.

Ultraviolet technology provides many benefits to our customers and the environment. We will continue to think outside the box on the best ways to protect and provide Earth’s most essential resource.

 

Marc Lucca is the president of Aqua Pennsylvania, which serves approximately 1.4 million people in 32 counties throughout the Commonwealth of Pennsylvania.

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