Evaluation of peat and compost filtration for the treatment of the effluent of yard waste composting facilities

Yard waste compost leachates may contain relatively high concentrations of organic matter and thus require treatment before being released into the environment. The leachate used in this study is characterized by variations in organic content, BOD5 (biochemical oxygen demand after a 5-day incubation period at 20 degrees C) varying from 100 to 5000 mg/L. Promising results were obtained in the laboratory using 20-L biofilters of pear and compost as filtering media for the treatment of this effluent. BOD5 reductions of 82% at an organic loading of 0.21 kg BOD5/m(3) . d, and of more than 80% for SS (suspended solids) were obtained. Residual color in the effluent of the columns, leached from the humic material used as filtering medium, affected COD reduction, which reached 70% at best. Compost biofilters were as efficient as peat biofilters for reduction of SS and BOD5, and could be regarded as economical filtering media for treating leachate from composting sites. However, the effluents treated by these units did not meet Quebec standards for release into some surface water systems or storm sewers when the higher organic loads were used (0,21 and 0,42 kg BOD5/m(3) . d).