Slater, Iowa

Secondary Treatment with Nutrient Removal

RAB™ treatment system helps municipal wastewater facilities meet stricter limits and enhance removal process.


The City of Slater, IA (2,000 Population) operates a 1 MGD aerated lagoon wastewater treatment plant. This plant was designed to meet the community’s BOD and TSS limits. Recently, the facility received a stricter ammonia discharge limit that the existing facility is unable to meet. The facility must upgrade the treatment process to meet these stricter limits. The City selected Gross-Wen Technologies to provide the Revolving Algal Biofilm (RAB™) treatment system to help the facility meet these stricter limits.

The RAB system is well suited to provide enhanced secondary treatment with nutrient removal. The system is capable of simultaneous BOD, ammonia and phosphorus removal. The RAB system is placed directly before the lagoon cells to take advantage of the nutrient rich and warmer influent water. This makes the RAB an ideal choice for lagoons that are looking to improve their effluent water quality without changing from their simple lagoon treatment system. It should be noted that the RAB system also removes TN and TP, which is likely to be included in the City’s treatment requirements in the future.

Today the system is being built to house three, 10-belt RAB modules (30 belts total). Additionally, the City designed the system to have space for up to 6 modules total; allowing the City to easily add treatment capacity as the community continues to grow.

Facility Design Criteria

The RAB system is designed to meet the City’s new ammonia discharge limit.

We don’t just think green, we grow it.