MICROBIAL CHARACTERISTICS OF CONSTRUCTED WETLANDS

Constructed wetlands have been shown to be capable of removing a wide variety of contaminants, including bacterial pollution. Wetlands are k nown to act as biofilters through a combination of physical, chemical and biological factors which all participate in the reduction of the n umber of bacteria. Five constructed wetlands in the Czech Republic wer e studied during 1994 and 1995 in order to determine removal of total and faecal coliform bacteria and Enterobacteriaceae. In addition, tota l count of aerobic and anaerobic bacteria were determined in water. Po pulations of nitrogen cycle bacteria were monitored on roots and rhizo mes of Glyceria maxima in the system at Doksy. The results revealed th at the retention of coliform bacteria is very high and exceeds common retention values for conventional systems. The measurements also indic ated that nitrifying bacteria were not present in wastewater, however, quite large numbers were found on the surface of roots and rhizomes o f Glyceria. This fact can explain the significant nitrification observ ed in this system. (C) 1997 IAWQ.