Elimination of Daf Sludge Disposal through Resource Recovery

A common approach to wastewater pretreatment in the food industry is the utilization of dissolved air flotation @AF) cells. DAF units are common for BOD, TSS, and FOG reduction when wastewater is discharged to a municipal wastewater treatment plant. A growing problem for all DAF systems is that of sludge disposal. In the o p t i o n of a DAF, contaminants are removed in the form of a concentrated float, or sludge, skimmed from the surface. Because of the large volume of water in these skimmings and the increasingly stringent government regulations on their disposal, the costs associated with handling DAF sludge can be very high and are expected to get higher. A sludge separation system currently being used at poultry, pork, and frozen food p h t s offers a cost effective alternative to typical landfill or land application. This system can separate the sludge into oil, water and solid components by means of heat and centrifugal force. Fat is discharged from the system as a finished product containing 1% or less solids and moisture. Solids are recovered at typically 5040% moisture. Separated water can be returned to the wastewater stream. Operating costs for the pretreatment plant are typically offset by selling the recovered fat to a renderer, grease processor, or stabilized and sold to a feed mill. In the case of meat or poultry processing, the recovered solids can be sold to a renderer or dried and sold to a feed mill. In addition, sludge disposal costs can be completely eliminated, turning a costly disposal problem into a profitable operation. Actual operating and performance data from field installations are covered in this paper.