REDUC1NG AMMONIA LOSSES BY ADDING FeCl_3 DURING COMPOSTING OF SEWAGE SLUDGE

摘要

The release of ammonia nitrogen during composting of sewage sludge mixed with a lignocellulosic bulking agent leads to a reduction in the agronomic value of the final compost and to harmful effects on the environment. We propose adding a cheap salt FeCl_3 which can be used without special precaution to reduce ammonia losses by decreasing pH conditions. An in-vessel co- composting experiment was conducted in a large reactor (100 L) in which FeCl_3 was added to sludge mixed with a bulking agent (pine shavings and sawdust) and compared with a control mixture without FeCl_3. Temperature, oxygen consumption and pH were monitored throughout the composting of both mixtures. The final balance of organic matter, organic and inorganic nitrogen permitted to conclude that the addition of FeCl_3 reduced nitrogen loss (by a factor of 2.4 in relation to the control) and increased mineralisation of the organic nitrogen by 1 .6.