DAVYHULME WwTW PILOT VERSUS FULL SCALE BAFF PLANT

Davyhulme Wastewater Treatment Works (WwTW), Manchester, England is the largest of North West Water's wastewater treatment plants. It serves a population equivalent of 1.2 million, and handles a large volume of industrial effluent. The UK's environmental regulator, The Environment Agency, imposed a new consent standard for Davyhulme works, tightening limits on Biological Oxygen Demand (BOD), Suspended Solids (SS) and, in particular, ammonia, as part of the Mersey River Basin Campaign. The tighter limits led NWW to trial a new process called Biostyr, patented by Ominum Traitement de Valorisation Birwelco (OTVB).Trials were launched to reassure North West Water that Biostyr would effectively treat wastewater at Davyhulme, and would be able to deal with the inhibition effects of the large amount of trade discharge. OTVB was contracted to build a half-size cell pilot plant at Davyhulme WwTW in 1991, at a cost of £2 million. The plant was tested at various upward flow velocities with a maximum of 10 m/h. Impressed by its performance, NWW decided to purchase a 36 cell Biostyr plant from OTVB at a cost of approximately £50 million. Outstanding benefits Design estimates made during the life of the pilot plant have proved encouragingly accurate. Close correlation has been observed between the first year performance of the 36 cell plant and the pilot plant data.The decision to invest in a half—size cell for pilot trials has brought several outstanding benefits:Estimated savings of £10 million, with cell numbers reduced from 44 to 36 and co-settling of backwash water.Assurance that the 36 cell plant would have a high level of operability.Thorough understanding and knowledge of a new process, including its strengths and weaknesses.Considerable confidence in the effectiveness of the process in removing ammonia.Indications that the plant would provide protection from inhibition.