Since the mid-1970s, Sweden has been depositing 1 million ton d.w sludge/year, produced at waste water
treatment plants. Due to recent legislation this practice is no longer a viable method of waste management.
It is necessary to improve existing and develop new sludge management techniques and one promising
alternative is the dewatering and treatment of sludge in constructed wetlands. The aim of this study
was to follow reduction of organic carbon, BOD and nutrients in an industrial sludge containing nitro-aromatic
compounds passing through constructed small-scale wetlands, and to investigate any toxic effect
such as growth inhibition of the common reed Phragmites australis. The result showed high reduction of
all tested parameters in all the outgoing water samples, which shows that constructed wetlands are suitable
for carbon and nutrient removal. The results also showed that P. australis is tolerant to xenobiotics
and did not appear to be affected by the toxic compounds in the sludge. The sludge residual on the top of
the beds contained low levels of organic carbon and is considered non-organic and could therefore be
landfilled. Using this type of secondary treatment method, the amount of sludge could be reduced by
50–70%, mainly by dewatering and biodegradation of organic compounds.
2011 Elsevier