Wastewater Screenings Disposal Problems

July 11, 2002

Installation of a new system that grinds, washes, compacts, and dewaters bar screenings at the Meriden(CT) Water Pollution Control Facility has reduced organic content and overall volume, eliminating remote landfill disposal costs, while also significantly reducing handling needs and odor, according to the plant's manager. In addition, the processed screenings have been approved for disposal as feedstock for mass-burn, trash-to-energy plants.

The Screenings Washer Monster„· device, installed last May as an alternative to a costly, complex and burdensome procedure forced by closure of an adjacent landfill, is manufactured by JWC Environmental of Costa Mesa, CA, which has a patent pending for it.

"Before the landfill adjacent to our site was closed, all we had to do was haul the screenings there in our own 8 cu. yd. truck,? recalled Robert T. Mercaldi, Assistant Director, Water Pollution Control Division, Dept. of Public Works, and manager of the 11.6 mgd plant, which is a two-time winner of EPA Region 1's Operation and Maintenance Excellence Award.

"After the closure, we had to find a company licensed to haul over the road, certify testing for a list they gave us of screenings parameters to be analyzed, rent a 15 cu. yd. specially-lined dumpster for $1200 a month, and pay landfill drop-off charges ranging from $40-50 a ton at sites in Ohio, Pennsylvania, and New Jersey,? he said. "Meanwhile, we had a complex new task to take care of in the plant, moving around solids heavily loaded with organics, with heavy odor, and requiring double and triple handling.?

"But we couldn't go on like we were, and were ready to award a bid to JWC Environmental for a grinding solution, when we found out they had developed a new piece of equipment for this situation, and had high hopes for it.?

"We installed the new unit without the need for any outside contractors, including all wiring and controls, and haven't had any operational problems with it,? he stated. "It's basically totally unattended. The control panel is checked daily by regular plant operators, who have a manual to follow if they need it, and we'll be using our regular maintenance mechanics for biannual checks of gear oils and transmission fluids.?

"I was a little concerned when nothing had come out the end for the first five days after startup, but I also noticed there wasn't any odor,? he remembered. "Finally, a very dry solid, resembling shredded newspaper, extended 6 or 8 inches above the exit chute, like ashes at the end of a cigarette. That falls off into a bin, and we bag it up for disposal as Special Waste, including state-approved use in trash-to-energy plants. The Connecticut Dept. of Environmental Protection is working further with the trash-to-energy plants to have the material re-classified as Municipal Solid Waste.?

"We've been able to reduce the weight of our bar screenings from 8 tons per month to 660 lbs per month, and their volume was reduced from 15 cu. yd./mo. to one cu. yd./mo.? he concluded. "In addition to eliminating the cost for the out-of-state dumping, and all that extra work we were doing with a backhoe, front-end loader, wheelbarrows, and the dumpster, we no longer need the bar screen at our pump station. All the screenings formerly removed there can be pumped to the inlet building where the new unit is.?

The Screenings Washer Monster is a self-contained unit that can effectively process screenings that have been captured by bar screens or other screenings removal devices. Discharge is said to be virtually free of organic(fecal) matter, with the exit plug typically 40-50% dewatered, and reduced in volume by about 75-80%.

Screenings capacities are 150 cu.ft.(2.55 cu. m.)/hr for a 10 HP(7.5 kW) unit, or 25 cu. ft.(0.71 cu. m.)/hr for a 5 HP(3.7 kW) alternative. The unit is available in a grinder-less version for use with the company's Auger Monster system.

About the Author

Matt Giambrone