August 2011, Vol. 23, No.8

Problem Solvers

New liquid-polymer feed system has unexpected benefits

Problem: Need to replace failing liquid-polymer feed system.

Solution: Installation of new system with a wider range of available blending polymers.

 

The City of Marengo, Ill., is a growing municipality of nearly 8000. In 2007, operators at the city’s 3.4-million L/d (900,000-gal/d) wastewater treatment plant began to notice that the liquid-polymer feed system was performing erratically, resulting in increased downtime and maintenance. The additional maintenance requirements resulted in increased cost to the city.

Also, unreliable operation of this type of system, which plays a crucial role in cleaning wastewater, can result in a process that does not meet public health and regulatory standards. Since the city’s system was wasting liquid polymer by not using it as precisely as a new system would, the city decided to replace the system.

To find a replacement, Steve Fiepke, superintendent of the Marengo Wastewater Treatment Plant at the time, consulted with Peter Lynch at the manufacturer’s representative firm, LAI Ltd. (Rolling Meadows, Ill.). After learning the plant’s requirements, Lynch suggested the dynaBLEND® liquid-polymer-blending technology from Fluid Dynamics, a division of Neptune Chemical Pump Co. Inc. (North Wales, Pa.).

The dynaBLEND is designed to activate all types of liquid polymer, and its nonmechanical mixing chamber is designed to deliver a high degree of reliability. 

The high-energy, nonmechanical system features HydroAction Technology, which is designed to produce an excess of six times the mixing energy per unit volume than a comparable-sized mixer.

The HydroAction Technology operates in three stages. In the first, a high-velocity water jet impinges on the polymer as it enters the mixing chamber. In the second, the blended polymer recirculates multiple times for additional exposure to non-damaging turbulence, completing the blending process. In the third, mixing energy is diminished in the system’s concentric chambers, while the flow path through the concentric chambers further ensures optimum polymer performance by preventing polymer from short-circuiting. This process is designed to ensure high mixing energy without the use of mechanical impellers, which could cause polymer damage and gelling.

The polymer mixing system also features an injection valve that is easy to disassemble and inspect; a small, space-saving footprint measuring 610 mm (24-in.) deep ´ 610 mm (24- in.) wide ´ 1730 mm (68 in.) tall; and the ability to pull liquid polymer in directly from a storage vessel on an as-needed basis to help reduce the chances of a polymer spill.

“It was much easier to set the dials for the feed rates for the dewatering or thickening processes,” Fiepke said. “We also noticed a reduction in the amount of polymer we were using for those processes, so there was a monetary savings there. After a couple months of testing it, we decided that it was something that we were interested in and decided to purchase it.”

Operators can manually set flow rates, which enable them to more effectively control polymer use and keep costs down. The system only requires periodic maintenance where operators check the oil and clean the check valve.

“It delivers the polymer at either a low-flow rate or high-flow rate, and is pretty much maintenance-free, which is nice,” said Jay Berman, current superintendent of the plant. He added, “It’s easy to operate and troubleshoot, and perhaps best of all, it’s a workhorse.” Berman also said he is pleased with the cost savings the system provides.

 

©2011 Water Environment Federation. All rights reserved.