Composting of forest industry wastewater sludges for agricultural use

The feasibility of composting of pulp and paper industry sludges was studie d. The aim was to study the progress of the composting process and the toxi city and applicability of the sludges in agriculture. Five different sludge s were used: two biosludges and three biosludge and primary sludge mixtures . The sludges were composted in seven piles, two smaller of them founded wi th leachates collection systems. The piles were monitored throughout the co mposting period by physical measurements, chemical analyses and toxicity te sts. Also the lignin concentrations were measured from the sludges and from the soil as well as the amount of mycelium. The results showed that all sludges were easily composted and they will be suitable for the use as soil improvement in agricultural plant production. Toxicity of the sludges decreased during composting and all the sludges wer e proved to be non-toxic at the end of the composting. Heavy metal concentr ations were low in all sludges and leachates. The leachates were also non-t oxic and the concentrations of nutrients were low. (C) 1999 Published by El sevier Science Ltd on behalf of the IAWQ. All rights reserved.