NUTRIENT REMOVAL IN A REED BED SYSTEM

Since 1984 investigations concerning sewage technology, plant physiology and soil properties have been carried out on the reed bed system at Mannersdorf/Leithagebirge (local loamy soil, Phragmites, planted area 3 x 150 m2, influent 30 - 50 mm/d). The removal efficiency of COD and BOD5 amounts to 80-90% and 90-98%, respectively. Elimination of nutrients (N(TOT) and P(TOT)) varies from 30 to 60%, in general. Total nitrification cannot be reported for any of the plots fed with different sewage qualities. Nutrient uptake of N(TOT) and P(ToT) by Phragmites a. reaches 30 or 15% of influent sewage load during July and August but is of no importance with respect to the average of the year. The proportion of N(TOT) in the soil is still increasing every year and now amounts to about 450 mg/100g soil. The concentration of phosphorus essentially stagnates at the level of 50 mg/100g soil.