Design and construction/reconstruction of sludge pumping stations
From technical point of view, sludge PS is one the most complicated, because of liquid high dry solids and sludge viscosity. Also it should be taken into account, that methane gas is released inside sludge pipeline, when liquid is not recirculating and all necessary air relief valves should be installed on the pipelines to avoid pump air plug. Two different type of sludge PS can be recognized:
- Active sludge circulation PS: this type of PS is designed to ensure necessary active sludge recirculation from secondary clarifiers to bioreactor. Usually these type of PS is equipped with centrifuge type pumps: submersible for small and mid size WWTP and dry installation for big size WWTP. Pumps are usually controlled by VFC, depending on circulation ratio and influent flow. Beside recirculation pumps, access sludge pumps and tank drainage pumps are installed in the same PS. Pumped sludge DS concentration usually is 0,5-2% .
- Treated sludge PS: this is different type PS, set for sludge transportation to different treatment chains: thickening, digesting, dewatering, drying, storage. Comparing to recirculation PS, DS concentration in treated sludge PS is much higher: from 3% up to 30% DS. For this reason screw (progressive cavity) pumps are used. The main advantage of this type of pumps is constant flow (not depends from pressure level) and possibility to transport very high viscosity liquids. For dewatered sludge 20-30% DS these pumps are equipped with so called “bridge braker”-special feeding mixer system. Also polymer solution is injected into pipeline for lubricating side walls of pipeline to ensure good sludge sliding.
We have long term experience of design and construction/reconstruction of various size and type sludge PS, up to 6000 m³/h sludge flow or dewatered sludge PS up to 25% DS with up to 400 m pipe length.