This paper describes a study which was carried out to evaluate the performa
nce of two types of small sewage-treatment plant which are commonly availab
le in the UK, i.e. a rotating biological contactor and a sequencing batch r
eactor. Both systems produced an effluent quality of less than 20mg/l BOD a
nd 30mg/l SS; however, the sequencing batch reactor was more consistent in
producing a better effluent (i.e. BOD<10mg/l and SS<less than>20 mg/l) than
the rotating biological contactor. The sequencing batch reactor also demon
strated a greater tendency to remove nutrients, although the special design
features which were used in this study were believed to have enhanced the
rate of nutrient removal.