Case Studies
Case Study 2: Severn Trent Sewage Treatment
Scunthorpe Sewage Treatment Works serves the Scunthorpe town and villages in the surrounding area. The plant treats a mixture of domestic and trade effluent; in particular the effluent from a crisp manufacturer. The Sewage Treatment Works (STW) site had three
distinct problems:
•The primary settlement tanks were badly affected by gross volumes of floating solids.
•The main feeder channels between the primary screens and the primary settlement tanks were blocked with thick sludge type deposits of fats and solids. The grease and fat was fibrous in appearance.
• The sludge consolidation tanks were badly affected by gross floating solids.
Floating sludge and poor sludge compaction was also causing a major problem with the sludge consolidation tanks. Instead of decanting liquor to be returned to the primary tanks, the decanted return was heavily contaminated with fatty sludges. This in turn affected the performance of the feeder channels to the primary settlement tanks and aggravated the problem of floating sludge on the primary tanks.

Quash undertook the scope for consultation and recommended application of its Formula 33® microbial aid formulations to the client. This solution was added with the incoming effluent using Quash’s Pre-Assimilated Technology (PAT)® system and dosed into the stream on a regular basis. While the operations were in process Quash technical Team made regular site visits to assess the progress and undertake sample collection as per the predefined schedule.

After four weeks of treatment the primary settlement tank performance was significantly improved with only a small volume of floating sludge evident. This was easily controlled and dealt with efficiently by the surface scrapers. The problem of ‘layering’ of the sludge and the formation of a sludge blanket had been eliminated. The cleaning routines of the main feeder channels were reduced to once a week with only a general hose down of the channels now required. BOD from the primary tank was reduced improving the performance in the activated sludge plant. The most noticeable area of improvement centred on the sludge consolidation tanks.