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Washer-compactor cleans up sloppy, smelly screenings
On any given day, operators at the village of Addison’s South Wastewater Plant have no idea what’s coming down the pipeline. With a combined storm and sanitary sewer system, the 20-in. inlet can go from a trickle to raging-water full with just a few hours of rain.
“We always get bigger than usual equipment because we have to be ready for bigger flows. (The plant) can go from 1.5 to 20 million gal per day in a heartbeat,” said Doug Armstrong, the plant’s chief operator. “I always tell manufacturers: I need something that’s little but big.”
In 2003 they decided to stay ahead of requirements and install an innovative washer-compactor called the Screenings Washer Monster (SWM) , built by JWC Environmental of Costa Mesa, Calif. The positive results have astounded the South Plant’s staff and received rave reviews from the local trash hauler. The village even purchased a second unit for their North Plant.
“I would say the SWM has exceeded my expectations,” Armstrong said. “I cannot believe how well it washes and removes fecal material, and the reduction of the waste stream is amazing. Cleaner, more compact screenings have an overall effect on the plant. It reduces the time and work people have to put into handling piles of wet screenings.”
Stationed behind the plant’s two inlet screens, the SWM model 4018 accepts trash and rags pulled from the channel and puts them through a six-stage process—wash, grind, wash, screen, dewater, compact—before dropping them into a dumpster. Screenings first fall into a hopper and are flushed through a Muffin Monster grinder to break up clumps, expose more surface area for better washing and protect the system from blockages. Next, internal spray jets clean the solids and liquefy fecal matter, returning it to the treatment plant flow where it belongs. Finally, screenings are compressed and dewatered as material is pushed up and out the discharge chute.
“The SWM is preceded by two inlet screens with 15-mm openings. Now, I wish I had window screening on there pulling everything out because this SWM could handle it,” Armstrong said, referring to the perforated plate fine screens with 3- or 6-mm openings. “The discharge is clean, compact and virtually without odor.”
The local trash collector is thrilled with the cleaner screenings, Armstrong said. Raw screenings from several nearby communities are hauled to a local transfer station where “fecal material is just sitting around on the tipping floor,” Armstrong said. “With visual fecal material absent (from Addison’s screenings), he just loves it.”
Before the SWM , the plant had 1 to 4 cu yd of material hauled away weekly and in wet weather, 3 to 6 yards per day. With the SWM in operation, the amount of material is “maybe 10 to 15 yards of debris for the entire year,” Armstrong said. That’s an average discharge rate of just 1 cu yd per month.
JWC representatives helped with the start-up and noticed something unusual. “The compaction was so great, it took over eight weeks for material to even fill the chute,” said Dean Wiebenga, a principal with Peterson & Matz, JWC’s local representative. “I have seen a great difference in the plant’s operation… Addison has reduced the volume hauled to the landfill tremendously.”
Armstrong reports that the washer-compactor is also built tough. For example, one night an operator left it turned off, letting screenings accumulate in the hopper and up into the discharge chute for 16 hours. However, instead of a big mess the next morning, Armstrong said he simply flipped it on, watched it chew up all the material in a matter of minutes and process it cleanly.
“We’ve always had a good relationship with JWC and Peterson & Matz, the local rep,” Armstrong said. “When I call in for something the engineers and staff are more than helpful.”
The village of Addison is pleased with the results and purchased a second one for their North Plant in 2007. “The village is very cost payback conscious,” Wiebenga said. With the SWM’s clean and compact discharge, everyone benefits and the village got the return on investment it was looking for.
The washer-compactor is available integrated with fine screens as part of a complete headworks package and won the Water Environment Federation’s Innovative Technology Award for solids handling in 2001.