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 known to act as biofilters through a combination of physical, chemical and biological factors which all participate in the reduction of the number of bacteria. Five constructed wetlands in the Czech Republic were studied during 1994 and 1995 in order to determine removal of total and faecal coliform bacteria and Enterobacteriaceae. In addition, total count of aerobic and anaerobic bacteria were determined in water. Populations of nitrogen cycle bacteria were monitored on roots and rhizomes of Glyceria maxima in the system at Doksy. The results revealed that the retention of coliform bacteria is very high and exceeds common retention values for conventional systems. The measurements also indicated that nitrifying bacteria were not present in wastewater, however, quite large numbers were found on the surface of roots and rhizomes of Glyceria. This fact can explain the significant nitrification observed in this system.