Oxidation ditch system for waste water treatment at various demands fo
r effluent quality with regard to BOD, nitrogen and phosphorus are pre
sented. Simple design for only BOD-removal and nitrification as well a
s designs for advanced treatment including biological nitrogen and bio
logical phosphorus removal are presented, and full scale results from
more than 15 years of operation are shown. The simple design and price
competitive construction can none the less produce effluent qualities
below 15 mg BOD/l, 8 mg NA and 1.5 mg P/l if the right oxidation ditc
h combination is used.