Techniques for the evaluation of wastewater treatment processes
This study focussed on extending and applying techniques to measure hydrodynamic characteristics in treatment units at sewage works. Use was made of tracer dye studies and a spreadsheet based analysis tool. The resulting infonnation about residence time, tank conguration and pathological behaviour was linked to other infonnation from respirometry and flow and load studies. Characterising the wastewater process will become increasingly important as the economic and compliance drivers in the operation of wastewater treatment facilities become increasingly pronounced. Case studies at Royton WWTW, Chorley WWTW, Preston WWTW and Montebello WWTW were used to develop, improve and apply the methodology. Tests at Royton and Chorley were used to develop the practical side of conducting tracer studies. The Preston case study was used to improve the diagnostic methodology. It was demonstrated that consent failures as a result of events are usually a result of a number of (linked) factors, in the case of Preston influenced by the tank conguration. The response of a pulse of dye was measured at Preston in vessel outlet throughout the works. The tracer dyeresponse was used to predict the response to a discharge of high ammoniacal leachate liquor and compared to measured data. This type of calibration experiment facilitated the simulation of different discharge event scenarios. The tracer and modelling techniques were incorporated in a general diagnostic methodology, which caters for a phased approach in diagnostic studies. A series of diagnostic tables take the user through cause - effect hypotheses and possible measurement techniques to use in the diagnostic investigation. Although the diagnostic methodology proved to be a versatile asset optimisation tool, which required considerable less effort than deterministic models, implementation in United Utilities' AMP3 Capital Investment Programme was problematic. The size of the programme and lack of resources forced the company to implement standard rather than tailor-made solutions. However, the diagnostic methodology can easily be applied elsewhere in the wastewater industry.