The Town of Peru’s early 90s era water treatment plant began facing difficulties meeting new water treatment regulations, causing the town to invest $3 million in water system upgrades to improve the overall quality of the water and help meet the regulations. The investment included improvements in storage tower mixing systems, reservoir dredging, and treatment plant upgrades. All aspects of the improvements relate to reducing organics that lead to the creation of disinfection byproducts such as THMs and HAA5s.
WesTech Engineering, Inc. was engaged in a portion of the project relating to the Multi-Tech™ treatment units initially sold to the town by Culligan in 1994. The Culligan Multi-Tech product line has had an interesting history of ownership since the technology was developed in 1976. It was sold to USFilter as a Microfloc product in 1998, and then eventually purchased by Siemens in 2004, who sold this product line to WesTech in 2012.
The treatment system at the Peru Water Treatment Plant was comprised of three trains of Multi-Tech three-stage pressurized systems, each including a 6' diameter down-flow roughing filter, 6' diameter down-flow mixed media filter, and 7' diameter down-flow GAC contactor.
Installed in 1994, the treatment system began to develop operational problems as it aged. As a result, the plant had significant DBP issues, requiring a major plant overhaul and upgrade.
The engineering firm AES Northeast, PLLC of Plattsburgh, NY, was key to bringing all of this together with in-depth investigations and evaluations of the treatment plant and distribution system to identify changes and improvements needed to reduce disinfection byproducts. AES worked closely with the municipal water filtration group of WesTech to determine what could be done with the filters, and to determine which media types, depths, and sizes would best treat the plant’s influent water.
WesTech provided the new media for the roughing and multimedia filters, new GAC media for the contactor, and new stainless steel air distribution grids, backwash supply headers, and underdrains for the vessels. WesTech also provided onsite supervision, start-up assistance, and operator training. The upgrade included adding a separate backwash waste line from the roughing filter and multimedia filter, removing the air educator (which was replaced with positive displacement blowers), and adding air headers and backwash supply headers.
Other enhancements to the facility included a new custom SCADA control system, positively controlled actuated valves at the head of each filter train, a new heating system, installation of mixers in both water storage tanks, a new chemical injection point at the water source for enhanced coagulation, and a “booster” hypochlorite injection point in the distribution system. The structure was also expanded to include a water testing lab, office, and control room.
As of 2010, the Town of Peru had nearly 1,600 residents. The plant receives its water from Furnace Brook Reservoir, which was constructed in the 1920s and is located just a few miles away. Influent water turbidity ranges from 0.7-1 NTU and occasionally spikes to 10 NTU. Influent pH runs about 7.0, color is roughly 40 units with a peak of 100, and alkalinity is in the range of 30-110 mg/L. The raw water TOC is in the range of 4.5-5.0 mg/L and it’s reduced to 2.0-2.5 in the effluent. The town uses flow-paced dosing of poly aluminum chloride with a non-ionic polymer for coagulation, which the town has found maintains the ability to form floc, even when faced with low alkalinity. The plant operates in the range of 100-185 gpm/train.
Today, the plant is fully functional again and operating within compliance of the new regulations. They have almost immediately recognized significant savings in chlorine usage by about 50%, and reduction in disinfection byproducts.
The true success of the project relies on the coordination and collaboration with all parties, which includes the town, the water plant operators, the engineering consulting firm, and the contractor. The on-site modifications were made by J. Hogan Refrigeration & Mechanical, of Peru, NY.