BIOLOGICAL NUTRIENT REMOVAL - DESIGN SNAGS, OPERATIONAL PROBLEMS AND COSTS

The EC urban waste water treatment Directive will lead to some sewage- treatment works in the UK having to remove nitrogen and phosphorus. Th e paper reviews the basic biological processes which are available for retrofitting existing activated-sludge plants to achieve this removal , and then points to some of the problems which are encountered with t hese processes in other countries. The authors make suggestions as to how these problems can be overcome in design and operation. The paper also provides a cost comparison of different ways of uprating an exist ing nitrifying activated-sludge plant to achieve nitrification/denitri fication and phosphorus removal.