FULL-SCALE TRIAL OF DEGREMONT’S BIOLYSIS ‘O’ SLUDGE MINIMISATION TECHNOLOGY ON AN ACTIVATED SLUDGE PLANT IN THE UK
Mike Rewcastle1, Tom Taylor2, John Churchley3 , Thierry Lebrun4, and Didier Perrin4.
1Northumbrian Water, 2Yorkshire Water, 3Severn Trent Water, 4Degremont.
(free)
Among the several options for managing sewage sludge, minimisation of production has received relatively little attention. Degremont have developed and are promoting Biolysis O (which uses ozone) as a realistic option to reduce the amount of sludge for which treatment and disposal or beneficial re-use outlets are needed.
This paper provides information from, and discusses the outcome of, a full-scale trial completed between April and August 2004 at Broomhaugh STW in Northumbrian Water Ltd the objectives of which were to
- Confirm the sustainable levels of sludge reduction achievable
- Establish the cost of the sludge minimisation treatment
- Study the impact on sewage treatment processes and final effluent quality
- Study the impact on activated sludge behaviour
- Study the impact on residual sludge quality
- Understand the operability and process control aspects of applying Biolysis O on an activated sludge plant.
The trial has been a collaborative one involving the technology supplier, and three UK Water Companies (Northumbrian, Yorkshire and Severn Trent). Agreements were drawn up to cover the trial scope, responsibilities, budget, confidentiality and intellectual property.
The chosen sewage works was a small conventional two-lane activated sludge plant with primary treatment, aeration and final clarification. Broomhaugh STW serves a domestic population only, of about 7,500 p.e. Biolysis O was applied to one entire lane, effected by a separation of lane outlets and return activated sludge recirculation routes. In this way, a side-by-side trial has been able to observe and monitor the impacts on the trial lane sludge production and its final effluent, relative to the other, control lane.
Before applying Biolysis O, extensive work was carried out to characterise the lanes to confirm similar performance and establish the ‘normal’ range of biological sludge production. Ozone has been applied continuously during the trial, at two dose rates targeted to achieve 60% and 80% reduction of biological sludge.
A robust methodology to monitor the impacts of the process in pursuit of the trial objectives has been implemented. This will be described in the report.
Results from the trial are presented and discussed.
KEY WORDS Activated sludge, biology, Biolysis, minimisation, ozone, sludge, trial.
