Highly variable flow phasing - Wet well sizing
Highly variable flow phasing - Wet well sizing
(OP)
thread161-194365
I'm designing a large residential sewer pump station. Due to development phasing, the initial flows are much lower than final flows. The retension time during initial phases is unavoidably long given pump submergence requirements. Septic conditions is a concern, is a bubbler a solution? I am concerned about cavitation. I have seen bubblers in a dry well pump station design but never on a submerged pump wet well. Any input would be much appreciated
I'm designing a large residential sewer pump station. Due to development phasing, the initial flows are much lower than final flows. The retension time during initial phases is unavoidably long given pump submergence requirements. Septic conditions is a concern, is a bubbler a solution? I am concerned about cavitation. I have seen bubblers in a dry well pump station design but never on a submerged pump wet well. Any input would be much appreciated





RE: Highly variable flow phasing - Wet well sizing
RE: Highly variable flow phasing - Wet well sizing
In the past I've been able to get away with sitting floats close but provide the depth to raise the pump on float as flow picks up.
Also consider using a pump with a trimmed impeller for the first stages of development. When flow picks up you have a larger impeller put in the pump. This is paticulaurly a good option of there will be many years between development phases.
RE: Highly variable flow phasing - Wet well sizing
RE: Highly variable flow phasing - Wet well sizing
RE: Highly variable flow phasing - Wet well sizing
RE: Highly variable flow phasing - Wet well sizing
RE: Highly variable flow phasing - Wet well sizing
RE: Highly variable flow phasing - Wet well sizing
6" difference is probably the minimium you could realistically get away with anyhow with a float, you might be able to get an additional inch or two with a bubbler system or transducer. I dont know that an ultra-sonic would be a good choice for fine tuning pump on/off because of the possibility of grease or other floating solids in raw wastewater.
I designed a pump station in NC, which requires between 2-8 cycles per hour in 4 phases. The first phase operated very close to 2 cycles per hour with 2 pumps (one at a time and a rudundant pump). Next phase added a third pump, third phase added a fourth pump, and final phase replaced all pumps with larger pumps and the cycle times were close to 8 cycles per hour, although the final phase also included installation of VFD's and flow matching capabilities.
If you can get away with adjusting pump on/off set points that is the simpleist.
Given the distance from the WWTP, and wheather or not you're discharging to a gravity sewer, the aeration option may provide additional benifits if it keeps the flow in the downstream sewer from going septic and H2S from attacking manholes, but that really should be looked at on a case by case baisis.