NEW SLUDGE TREATMENT TRIALS AT DAVYHULME WwTW BENEFIT FROM HIDROSTAL’S SLUDGE PUMPING EXPERTISE

The Davyhulme Waste Water Treatment plant in Manchester is historically known for being the site where the first large scale activated sludge process was tested in 1914. Although most parts of the pilot-plant were made of wood and the model was placed on the chassis of a horse-driven wagon, the installation exhibited most of the characteristic features of the activated sludge process we know today. The continuous-flow arrangement with separate clarifiers and activated sludge recycle, and the fill-and-draw arrangement, nowadays known as an SBR, were both actively tested.

Today, Davyhulme WwTW is the site being used by United Utilities to test a new process. The aim is to remove the nutrients from sewage mainly phosphates and nitrates. It involves diverting part of the settled primary sewage into two dedicated activated sludge lanes. Within these lanes the sewage is biologically treated to remove the nutrients. In order to divert the required flow of sewage from the culvert which supplied the normal activated sludge lanes to the two dedicated BNR lanes, two Hidrostal self-priming pumps [duty/standby] are being used, each rated at approx 150 lit/sec. The 2 metre width of the culvert, plus the fact that the flow of sewage to the activated sludge lanes could not be stopped, precluded the installation of submersible pumps. Hidrostal suggested that they could supply two types of self priming units - vacuum primer or tank primer. The priming tank self-priming pump was selected. By using the priming tank mechanism there is no vacuum pump or vacuum pump motor to maintain and no additional control equipment required so operational costs can be kept to a minimum.

Hidrostal supplied 2 No Screw Centrifugal sewage pumps, 250mm nominal bore, powered by 15 kw motors, each to provide 165 lit/sec at 5.25 metres head. The pumps are mounted at ground level on the side of the culvert.

Said Ivan Finch, Hidrostal’s Sales Engineer: “The pumps have been running successfully now for 24 hours/day for approx 12 months and have given excellent service with no problems being encountered. Whilst this priming arrangement is uncommon in the waste water treatment industry, it is a well proven, tried and tested method within the industrial market. With the correct application and Hidrostal’s expertise, this method of priming can offer lots of advantages to the waste water industry”.