ABSTRACT 



The Town of Durham, New Hampshire, has been using a sewage sludge 

 composting system since 1975 with considerable success. The process in- 

 volves mixing wet sludge (about 22 percent solids) with wood chips at a 

 ratio of three parts chips to one part sludge by volume, then covering 

 the pile with about a foot of composted sludge for insulation purposes. 

 Air is drawn through the pile for the first 10 to 14 days and exhausted 

 into a small pile of composted sludge for odor absorption. After this 

 period, the fans are reversed, and air is blown through the pile for an- 

 other 10 days. The resulting compost is stable, practically odorless, 

 and essentially devoid of pathogens. Negligible numbers of salmonellae 

 and undectectable fecal coliforms remained after the composting period. 



Composting costs were competitive with other methods of sludge 

 disposal, about $72 per dry ton compared with $115 to $134 for trench- 

 ing, $57 to $93 for incineration, and $62 to $115 for heat drying. 



Composting appears to be a viable and highly satisfactory method of 

 sludge disposal for towns without a high concentration of heavy metals 

 in the sludge. 



