Ovivo, a world leader in engineered water treatment solutions, is on course to complete a major refurbishment of Dorr Oliver® type scraper bridges at a sewage treatment works (STW) in the Home Counties.
Ovivo’s best value solutions include full replacement of all drive units and rail track, plus refurbishment of underwater and scum removal systems. The scraper bridges in this latest contract had reached the end of their working lives, encountering numerous mechanical drive or lift-system failures, also suffering from ‘crabbing’ whilst travelling along the tanks. As the bridges continued to deteriorate, the STW was issued with an odour abatement notice due to the poor condition of the tanks’ sludge removal system.
The scraper bridge currently undergoing refurbishment by Ovivo utilise a central drive unit with double output shafts to line shafts, couplings and plummer block bearings. A one-to-one chain drive leading down to a further drive unit carries the long travel cog drive wheel, which in turn traverses the bridges along rail track, up and down the tanks. The bridges have a skimmer blade mechanism that collects scum from the surface and discharges it up and over a stainless steel ramp into a scum outlet channel. This mechanism operates with the underwater structure which transfers settled sludge to a hopper at the end of the tank. A further scum blade is attached to the opposite side of the machine to trap scum from passing back into the tank.
Ovivo was awarded the contract partly because of its considerable knowledge of scraper bridge technology. In August 2007, Eimco Water Technologies (now Ovivo UK Limited), completed a divestment of certain Dorr-Oliver® technologies. Ovivo retained detailed engineering and technical expertise related to the scraper bridges and continues to provide refurbishment and maintenance services to support certain existing Dorr Oliver® equipment.