Watson-Marlow Bredel pumps in sewage treatment

The simple, glandless, straight-through design with no valves, vanes or impellers, has clear advantages in handling viscous sludges liable to contain rags or other solids which cause blockages.

• In the first stage, SP50 pumps run for approximately five minutes each hour and draw off sludge from the primary tank containing between 2% and 5% solids, and discharge to the top of a holding tank. Water is removed separately and goes for further treatment.
• An SPX50 pump running for twenty minutes in every hour, transfers the primary sludge from the holding tank to picket fence thickeners where it is constantly stirred.
• The sludge, by this time containing 8%, solids, is pumped from the thickening tank to a heated digester tank by an SPX80 pump, the slow speed avoiding thermal shock as cold matter meets warm.
• To complete primary auto-desludging, following digester treatment, the sludge goes to secondary storage tanks, where polyelectrolytes are dosed by low-pressure peristaltic pumps prior to dewatering.