Composting and utilization of forest industry wastewater sludges

Two different forest industry wastewater sludges were composted in plies. T he piles were founded with leachate collection systems. The aim was to stud y the progress of the composting process, the amount and quality of leachat es as well as the toxicity of the sludges and leachates. The sludges consis ted of mixtures of primary and biosludge. The piles were monitored for eigh t months by physical measurements, chemical analyses and toxicity tests. Th e leachates were collected for six months. The lignin concentrations and th e amount of mycelium were measured from the sludges and from the soil. Test plots and control plots were established to a field with different amounts of composted sludge in order to study the applicability of the sludges in agriculture. The results showed that both sludges were amenable to composti ng. The original sludges were toxic but the toxicity decreased during compo sting and all the sludges were proved to be non-toxic at the end of compost ing. The leachates were determined non-toxic and the heavy metal concentrat ions were low in both sludges and leachates. The sludges proved to be suita ble for use as soil improver in agricultural plant production.