Constructed wetland (CW) for industrial waste water treatment

The constructed wetland (CW) in Gradi e (Slovenia) has been in operation since 1991 for the purification of waste waters from a food processing plant. It functions according to the method of horizontal subsurface flow. Waste waters are composed of industrial, faecal and meteor waters. The CW is composed of two beds, filled with substrate and planted with Carex gracilis and Phragmites australis. Average hydraulic loading of the CW is 5 m3 d−1. A high COD average value of 3674 mg l−1 and a BOD5 average value of 962 mg l−1 are characteristic of influent waters. Analysis showed that pollution decreased with regard to COD by 92%, BOD5 89%, orthophosphate 96%, ammonium 86% and nitrate 65%. The microbiological parameters indicated that the total number of coliform bacteria is reduced by 99% and the number of faecal streptococci by 98%. Results demonstrated that the CW can be appropriate for treating waste waters from the food processing plants.