Process Troubleshooting of an Effluent Mechanical Filtration System

A Case Study (download )


Siemens Water


100,000 gpd WWTP in Pennsylvania

Services Requested:

Type of Treatment

  1. Wastewater Process: SBR Activated Sludge
  2. Effluent Filtration: Rotary Drum Disc Filtration

This small municipal wastewater treatment plant serves a small town in Pennsylvania with little industrial input. The plant effluent requirement is relatively lenient at 10/10/1 (mg/L as BOD/TSS/NH4-N). However, the process was unable to meet those requirements following a prolonged startup. The Process Supplier retained the services of Wastewater Experts, Inc. to determine the cause of system failure and identify corrective procedures and fixes which would achieve a satisfactory Performance Acceptance Test.

Examination of plant operating records revealed that the SBR effluent was reasonable, but the Effluent Disc Filter was ineffective. After much additional investigation the problem was clearly the very small size of biomass particles in the SBR effluent which then passed through the filter. The process conditions which caused this problem were identified as follows:

The Biological/Chemical causations of this failure were ultimately resolved, after much negotiation with the Contract Operators.


The Plant passed the Performance Acceptance Test.