Before using the Screenings Washer Monster, the Water Pollution Control Facility in Meriden, Conn., contemplated using a grinder/ shredder at the front end of the stream in the inlet. However, there was concern about possible reaccumula-tion of solids in the digester, which might cause plugging of pumps and heat exchangers. Photo: JWC Environmental
Muffins and cakes are unusual words to hear in a wastewater treatment plant. That has all changed with the introduction of the Screenings Washer Monster.
The Meriden, Conn., Water Pollution Control Facility has reduced organic content and waste volume with the Screenings Washer Monster, a device that grinds, washes, compacts, and dewaters bar screenings. Since installing the device, the facility has eliminated odor, handling of screenings, and landfill disposal costs.
The unit—from JWC Environmental of Costa Mesa, Calif.—is an alternative to a costly procedure forced by the closure of a landfill next to Meriden's 12 mgd facility. The facility had to find a company licensed to haul over the road, and certify testing for screenings parameters to be analyzed. A 15-cu.-yd. dumpster was rented for $1200 a month, and landfill drop-off charges were $40 to $50 per ton. Meanwhile, employees had to move around odorous solids loaded with organics, which required double and triple handling.
JWC Environmental's equipment provided a solution with the Screenings Washer Monster, a self-contained unit that processes screenings. Discharge is free of organic matter, with the exit plug 40% to 50% dewatered, and reduced in volume by 75% to 80%.
Solids move from a hopper through a Muffin Monster dual-shafted grinder and pass to an auger, which washes and separates organics from plastics, paper, and other undesirable elements. Organics and wash water pass through the auger's perforated trough and return to the plant's waste stream. Remaining material is conveyed, compacted, dewatered, and discharged as cake.
A controller accepts the input signal as synchronized with a screen or conveyor, and the auger operates automatically in an on/off cycle. During operation, the grinder operates continuously, or is sequenced to run only when the controller senses a signal.
The plant's two headworks screens have bar spacings of 1½-inch and an automatic raking system. Achute receives scrapings, and effluent water is piped in to push them into the Screening Washer Monster's square funnel hopper. The scrapings move through a grinder and into a wash box, where a high-pressure spray washes out organics. Compression and dewatering follows, with more water squeezed out in the tapered exit chute. The final product looks like compacted, shredded newspaper. The solid falls off into a bin and is bagged for disposal as municipal solid waste.
The weight of the facility's screenings has been reduced from 8 tons to 660 pounds per month; the volume has decreased from 15 to 1 cu. yd. monthly. The bar screen at the pump station is no longer necessary, as the screenings formerly removed there can be pumped to the new unit in the inlet building.
— Clifford Seth is a technical writer with Indumark, Doylestown, Pa.