Managing Difficult or Unusual Feedstocks
Many industrialfood processing factoriesare located in areas where discharges of process and sanitary wastewaters to municipal sewer systems areguided by Industrial Pretreatment Discharge regulations. These regulations often limit the amount of Biochemical Oxygen Demand (BOD), Total Suspended Solids (TSS) and Hexane-Extractable Materials (HEM) that can be dischargedto levels that are common in sanitary wastewaters.
To meet these limits, many of these food processors use Dissolved Air Flotation (DAF) as a pretreatment technology. One residual of theDAF process is “float”, which has compostable solids, oils, greases and other floatable materials from the original process wastewater. DAF sludges containanywhere from 5% to 15% total solids, so they behave as a liquid.DAF sludges are often land-applied, which can be challenging in watersheds with significant water-quality limitations, such as the Chesapeake Bay in Virginia, Maryland, Delaware, Pennsylvania and portions of New York.
Composters, like Royal Oak Farm in Evington, VA, can take these liquids in as tipping fee feedstocks if they have dedicated receiving facilities and good management procedures. This presentation will review how these feedstocks are created, their composting characteristicsand how 18,000 gallons per day of DAF sludges are currentlymanaged at Royal Oak Farm.As demand for this type of feedstock processing is increasing, this presentation will also cover more robust means of handling these liquids, which may require anaerobic digestion and mechanical dewatering.