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On any given day at the village of Addison’s (Ill.) South Wastewater Plant, operators have no idea what’s coming down the influent pipe.
With a combined storm system and sanitary sewer lines, the 20-in., inlet pipe can go from a trickle to raging water with just a few hours of rain.
“We always get bigger than usual equipment installed here because we have to get ready for the bigger flows,” said Doug Armstrong, chief operator of the Addison South Wastewater Plant. “The plant can go from 1.5 mgd to 20 mgd in a heartbeat.”
When it appeared strict landfill regulations were coming down the legislative pipeline, the city started investigating new technologies to clean up tons of wastewater screenings they were sending to a local transfer station each year. The city, located in the suburbs of Chicago, carefully plans frequent upgrades at its two wastewater plants so it can maintain high environmental standards.
In early 2003, they decided to stay ahead of legislation requirements and install an innovative washer-compactor called on the Screenings Washer Monster (SWM), built by JWC Environmental. The positive results from the installation of this washer-compactor have astounded the South Plant’s staff and received rave reviews from local garbage operators.
“I would say the SWM has exceeded my expectations,” said Armstrong. “I cannot believe how well it washes and removes fecal matter and the reduction of waste stream is amazing. Cleaner, more compact screenings have an overall effect on the plant, it reduces the time and work people must put into handling and cleaning up the wet, sloppy screenings material.”
Wastewater facilitates and transfer stations across the nation are struggling with the rising load of fecal laden sewage screenings. Handling the wet, sloppy, malodorous and hazardous screenings is a costly and time-consuming endeavor. In part, the problem stems from regulatory pressures pushing in opposite directions—wastewater plants want more solids removed at the headworks to protect sensitive treatment equipment such as membranes, and landfill operators need to reduce or ban completely the amount of hazardous materials dumped at their sites.
“We see the legislative handwriting on the wall across the country—fecal material has got to come out of wastewater screenings sent to landfills,” said Fritz Egger, JWC’s director of marketing. “Fortunately, our Muffin Monster grinder and patent pending Screenings Washer Monster technology help break-up material so the spray jets can more effectively wash off the fecal material. Our grinder is the real secret weapon inside this machine.”
Stationed next to the Addison plant’s two inlet screens, the SWM model 4018 accepts screenings pulled from the wastewater channel and puts them through a six-stage process—wash, grind, wash, screen, compact, dewater—before discharging them. When screenings first fall into the SWM’s hopper, they are flushed into a central Muffin Monster grinder which breaks up clumps, exposes surface area for efficient washing and helps manage the flow of material.
Next, spray jets wash solids clean and flush fecal matter through a screen and back into the plant while an Auger compresses the inorganic solid material. Finally, the screenings are further compressed and dewatered as the material moves up and out of a long discharge chute.
“The SWM is proceeded by two inlet screens with 15 mm openings, now I wish I had window screening in the pulling everything out because this SWM could handle it,” said Armstrong, referring to the trend toward fine screens with 3 or 6 mm openings. “The discharge is clean, compact and virtually without odor.”
The local refuse contractor is also thrilled with the cleaner screenings results, according to Armstrong. Raw wastewater screenings from several nearby communities are hauled to a local transfer station where “the fecal material is just sitting around on the tipping floor,” said Armstrong. “With the visual fecal material absent from the Addison screenings, the local refuse contractor just loves it.”
The grinding and washing action of the SWM gets screenings cleaner, and it also helps compact and reduce the cubic volume of material. After 13 months of operation, Armstrong estimates the SWM has helped cut the volume of material headed to the landfill by approximately 90%.
Before the SWM, the plant was having 1-4 cubic yards of material hauled away each week and in wet weather that could go to 3-6 yards per day. Now with the SWM, the amount of material is “maybe 10-15 yards of debris for the entire year,” said Armstrong.
That is an average discharge rate of just one cubic yard per month.
JWC representatives helped with the start-up of the unit, but noticed something unusual at first.
“The compaction was so great, it took over eight weeks for material to even fill the chute,” said Dean Wiebenga, a principle 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 greatly.”
Armstrong also praised the SWM’s quality design and construction. Armstrong recalled one night an operator left the SWM 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 turned the SWM on, watched it chew all the material up in a matter of minutes and process it cleanly.