Craig Coker

Craig Coker

Craig Coker

Speaker | Coker Composting & Consulting

Troutville, VA | (540) 874-5168 |

USCC Member

Craig has 40 years of experience in the planning, permitting, design, construction and operation of organics recycling facilities using several composting and digestion technologies. He is also a Senior Editor at BioCycle, the professional periodical for the organics recycling industry. He has presented at USCC Conferences in 2006, 2010, 2012, and has taught several USCC pre-conference workshops and Compost Operator Training sessions.

Presentation Title: Composting Liquid Dissolved Air Flotation Sludges

co-authors: Ken Newman

Session: Managing Difficult or Unusual Feedstocks

Time: Tuesday, January 29, 4:45 PM – 6:15 PM

Presentation Summary: Many industrial food processing factories are located in areas where discharges of process and sanitary wastewaters to municipal sewer systems are guided 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 contain anywhere 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 characteristics and how 18,000 gallons per day of DAF sludges are currently managed 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.