UV & Ozone Technologies

HOW A SIMPLE ORGANICS MONITOR HELPED REDUCE CHEMICAL COSTS

The Ridgway Water Treatment Plant (WTP) in Elk County Pennsylvania uses a Real Tech Real UV254 online analyser to achieve a 20-30% savings in annual coagulant use in their conventional water treatment process. The dual-feel Real UV254 analyser is used to continuously monitor raw and finished water dissolved organics via a single online analyser. Beyond operational cost savings, the Real UV254 system helps the WTP consistently produce high quality drinking water for the town’s 1700 customers.

Background 

The Ridgway WTP receives water from a spring-fed source on Big Mill Creek in rural north-central Pennsylvania near the Allegheny National Forest. Raw water from the creek is fed into the 272 million-gallon H.B. Norton Reservoir before being fed to the WTP. From there, the city’s 2 MGD (7.5 MLD) conventional coagulation, flocculation, sedimentation treatment process handles treatment. Raw water entering the process is dosed with polyaluminum chloride (PAC) for coagulation and soda ash (sodium carbonate) for pH control. Both gas chlorine and permanganate (KMnO4) are also dosed to achieve better organics control in the conventional process. Settled water  is then fed to one of five (5) conventional dual-media (sand + anthracite) filters for filtration prior to final stabilisation and disinfection before distribution. Overall, the process continues to provide excellent water treatment for its community. 

 

Improving performance with UV254 

Although raw water to the plant is of generally high quality, periodic turbidity spikes and seasonal variation of dissolved organics entering the process have posed operational challenges. Looking for ways to improve performance, Rick McKnight, Ridgway’s Water Plant Supervisor, decided to explore UV254 instruments in the summer of 2012. Before starting to monitor UV254, the plant looked at turbidity on the raw water. “We would have high colour in the water that wasn’t picked up with turbidity” said McKnight “As a result sometimes we were either over-, or under-dosing coagulant which led to filtration and other operating issues.” Based on his research and many years experience operating the plant, McKnight took a proactive approach by putting data from his Real UV254 meter into action. After five (5) years of very promising results the WTP installed a dual-feed Real UV254 analyser to monitor both raw and settled water in 2017. Now with years of continuous operating data the plant has developed a firm relationship between raw water UV254 and coagulant dose. Being able to monitor organics and adjust their coagulant has made a big impact for the plant.

 

Having UV254 is just as important as turbidity, especially during the summer season and after weather events. “We see events in the summer where UV254 is high from colour and organics, but turbidity stays low” stated McKnight. “It’s very important for us to remove organics for disinfection by-product (DBP) formation potential. The two-stream method is perfect for monitoring organics removal, it works great for us and we can consistently achieve really high-quality treated water.”  Beyond cost savings, the Real UV254 system has also proven to be easy to operate. “The analyser is fairly pretty fool-proof,” said McKnight,” and we hardly ever do anything to it for maintenance.”The ease of operation has meant that newer operators are eager to use the UV254 data as a crucial part
of their training and daily operations. 

 

“The Real UV254 system has been very reliable and easy to operate,” said McKnight, “and I would definitely recommend it to other water treatment plants.” The Ridgway WTP is a prime example of how Real Tech’s Real UV254 system can help operators know what’s in their water and respond to changing conditions. The ability to understand and adjust coagulant dose in real time not only ensures compliance with even the most stringent DBP regulations, it also saves the Ridgway plant 20-30% in annual operating cost. Overall, the Ridgway WTP is another win-win example of how Real Tech makes online water quality monitoring practical, accurate and affordable. 

 
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