A sewage treatment works in York has undergone a substantial upgrade to improve effluent discharged into a local river.  Due to the nature of the sludge, which is produced from the aeration process treatment of domestic sewage, movement of the sludge gave the potential for gas locking in the system pipework.  This, together with the high rag content in the sludge and a temperature of 35ºC made for difficult hydraulic suction conditions.  A duty-standby pair of pumps was required to circulate sludge from two digesters through heat exchangers and back into the digesters.

Transferring the sludge at a rate of 20 l/s and a maximum delivery pressure of 3 bar, the Mono pump has been so successful on this application that the customer has ordered another 4 units, for further digestion plant works on this scheme.