The Council Bluffs Water Pollution Control Plant, Iowa, replaced an outdated aerated grit basin to improve fine loess sand removal and reduce digester cleaning and sludge dewatering centrifuge repair.

Situation

Council Bluffs Water Pollution Control Plant in Iowa, USA, has handled all of the community’s wastewater treatment needs since 1974. Most of the original equipment was still in operation, including the existing pretreatment facilities, the primary clarifiers and the two-stage trickling filters that culture bacteria on rock media to decompose organic solids. 

Plant operators were concerned at the amount of grit that was passing through the system, abrading equipment and clogging processes.

Problem

Fine loess sand from local hills trickles into the waste stream, so any grit removal system would need to be able to target sub-100 micron fine grit.

Solution

Plant operators went through an evaluation process and settled on a new gravity-forced vortex grit removal system. The system consists of four HeadCell^® grit removal units, two SlurryCup™ grit washing units and one Grit Snail^® dewatering escalator.

Outcome

The retrofit grit removal system meets the needs of the plant, removing, washing and dewatering the problem fine loess sand.

It’s performing really well," said Hank Pangelina, Plant Supervisor, Council Bluffs Water Pollution Control Plant. "One of the indicators we had was that in the anaerobic digesters we haven’t seen grit. When you take a digester down and clean it out, you can see it. We used to have three feet (0.9 m) of grit, now we have very little. There’s less wear on the centrifuge, I don’t have to take the digester offline and clean it. We didn’t have to build another pump station and maintain it. All in all, this system has done what we wanted at a very reasonable cost!