-5- 



this period, the sludge is dewatered and in good condition for screening. 

 The compost pile can then be placed in a larger "curing" pile with no 

 danger of anaerobic conditions developing. A problem may develop if the 

 sludge is frozen when the pile is constructed. If this occurs, heating 

 may be initiated by exhausting a working pile into the frozen pile. 



Durham's present composting site is adjacent to the sewerage treat- 

 ment plant and covers approximately 1-3/4 acres. The area has a gravel 

 base and good drainage. It is recommended that any permanent site be 

 paved, and include a drainage system to handle leachate from the piles 

 and rain water falling on the pad. This should drain into a holding pond, 

 or preferably back to the head of a treatment plant. 



Mixing of the wood chips and sludge is done with a grader and loader 

 in the following manner: The loader operator constructs a windrow of wood 

 chips approximately 100 feet long. Sludge is piled on top of the wood 

 chips, then covered with another layer of wood chips. This provides a 

 "sandwich" of sludge between wood chips and aids in the mixing. The grader 

 operator then mixes the material back and forth until an even consistency 

 of wood chips and sludge is obtained. After the mixing is completed, the 

 loader operator transfers the mixture onto the wood chip layer on the com- 

 post pad as previously described. When piling this mixture onto the aera- 

 tion pad, it is important that the loader tires do not mat down the bedding 

 and that the material is not packed into the pile. Air cannot properly 

 move through an area that has been compacted, and the pile is likfely to be- 

 come anaerobic. 



In mixing, the grader and loader work well together. However, mixing 

 with the bucket of the loader only was tried and was found to be sufficient 

 if a grader is not available. However, the rnixing will not be as complete. 



