The Thompson Run Sewage Treatment Plant improvements project involved the construction of a new Sequencing Batch Reactor (SBR) treatment system being incorporated into the existing conventional activated sludge process. The new SBR has a peak capacity of 5 million gallons per day (mgd) with an average dry weather design flow of 1.5 mgd. The two systems together can handle a peak flow of 9 mgd. Each system is continuously fed through either the influent pumps or by gravity. Splitting the flows between the conventional process and the new SBR is controlled by a PLC system that can easily be programmed to accommodate operational changes. At this time, the PLC is programmed such that the Homeville/Kenmore watersheds are discharging into the SBR and the remaining watershed flows are pumped to the existing plant.

The SBR system includes a headworks system that includes a self-cleaning fine screen followed by a grit removal changer. Pretreated sewage will flow continuously from the headworks into the two SBR aeration tanks that are operated in parallel for BOD and ammonia nitrogen removal. Treated effluent is discharged into an ultraviolet disinfection system prior to combining with the existing STP effluent and discharging to Thompson Run through a new 36 inch outfall pipe.

The SBR system utilized at the Thompson Run STP is an Intermittent Cycle Extended Aeration System (ICEAS). The ICEAS system incorporates continuous activated sludge technology with intermittent systems operation. The system uses a single vessel in which the activated sludge is alternately aerated and mixed over a number of pre-determined cycles. Solids liquid separation occurs during the settling phase of the cycle. After the settling phase, treated effluent is decanted or withdrawn from the liquid surface. Flow to the vessel is not interrupted at any time. The functions of flow equalization, biological oxidation, nitrification, denitrification, sedimentation and aerobic sludge stabilization are carried out in a single basin. The ICEAS system has both a normal cycle and a storm cycle. During the normal operations, aeration occurs for 120 minutes, settling occurs for 60 minutes and decant occurs for 60 minutes for a total cycle time of 4 hours. During the storm cycle, the aeration time is decreased to 90 minutes, settling occurs for only 45 minutes and decant occurs for 45 minutes for a total cycle time of 3 hours. This storm cycle allows the peak flow rate of 5 mgd. to be treated.