CONTROLLING SEPTAGE HANDLING ODORS AT THE EDGARTOWN, MASSACHUSETTS WASTEWATER TREATMENT FACILITY

The Town of Edgartown is located on Martha's Vineyard, an island off the coast of southeastern Massachusetts. The Town's Wastewater Treatment Facility (WWTF) receives an average of 4,000 gallons per day of septage. Septage currently receives coarse screening with a manually cleaned bar rack prior to discharge into aerated holding tanks. This allows the WWTF staff to meter the septage into the WWTF at a controlled rate throughout the day. The aerated septage holding tanks are connected to an existing centralized scrubber system which also treats air from the Headworks, Primary Clarifiers, Aerated Sludge Holding Tanks, and Sludge Dewatering Areas. The WWTF is located in close proximity to a residential area.In June, 2000 the Town funded an Odor Study which identified the septage receiving and processing areas as significant contributors to past off-site odor problems. Also, there were times that grit and debris were being cleaned from the existing aerated septage holding tanks. These periods were identified as significant contributors to off-site odors. The following options were considered to control septage handling odors at the WWTF:Eliminate septage receiving, haul septage off the Island to a contract disposal facilityChemical addition to the septage holding tanksEnclose the septage receiving area in a building, and provide odor scrubbing, for the buildingProvide an enclosed septage receiving and treatment unit inside a building, and provide odor scrubbing for the enclosed septage receiving unit.It was determined that elimination of septage receiving at the WWTF would not be economical for the community. The cost to haul the septage off the Island is 0.30 to 0.40 per gallon, which is 4 to 5 times the cost to provide local treatment.Chemical addition to the septage has been intermittently used at the WWTF, and is not totally effective (even with very high dosages).The alternative to enclose the septage receiving area, and provide odor scrubbing would require an odor scrubber with a capacity of 5,000 cubic feet per minute (cfm). The alternative to provide an enclosed septage receiving and treatment unit would require a 500 cfm odor scrubber. This alternative also offers the advantage of removing grit and screenings from the septage before it is discharged to the aerated septage holding tanks. This will reduce the need to clean the aerated septage holding tanks which is a messy and odorous task.This presentation will review costs and performance of the septage handling system, and its effectiveness reducing off-site odors at the Edgartown WWTF.