THE SELECTION AND DESIGN OF ROTATING BIOLOGICAL CONTACTORS AND REED BEDS FOR SMALL SEWAGE-TREATMENT PLANTS

Severn Trent Water Ltd operates over 1000 sewage treatment works, appr oximately 70% of which serve a population of less than 1500. Since pri vatization, Severn Trent Water Ltd has spent over 70 million Pound rep lacing over 150 old works with rotating biological contactors (RBC) an d reed beds. The Paper describes changes in methods following the impl ementation of the Water Act 1989. Specifically, it discusses the Compa ny's achievements in resolving the hydraulic problems associated with small flows. The design of both integral and modular units is consider ed. The Paper includes reference to the development of reed beds for s torm water treatment as an alternative to conventional storm water tan ks for small communities. It also includes some details of final efflu ent quality and suggests that a high quality effluent can be achieved by this process, and specifically that the discharge from storm reed b eds is infinitely better than that from storm tanks.