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From Water and Wastewater.com Dewatering Merritt, BC -- Public works and operations management at a conventional activated sludge wastewater treatment plant (WWTP) report reduction of routine maintenance time for screenings processing equipment by over 75% through the installation of a design upgrade.
The upgrade, an Auger Monster®, aided in restoring optimal BOD levels along with other benefits realized upon installation. The original version was installed in 1999 after the plant lost district landfill privileges, and whose performance had begun to slip due to wear. With key components now fabricated from stainless steel, it is also expected to provide significantly extended high-performance service life, while the plant concurrently pursues installation of separate, long-needed grit removal equipment. The Auger Monster, manufactured by JWC Environmental in Costa Mesa California, incorporates a lifting spiral with patented Muffin Monster® grinding technology. Combining the benefits of fine screening with the high-flow capability of bar screens, the Auger Monster removes ground solids from the wastewater stream. As solids are conveyed and washed, soft organics pass through the Auger’s perforated screen and are returned to the channel. The remaining solids are washed, dewatered and compacted. Shawn Boven, AScT, Merrit’s Public Works Manager, noted the thinking behind the processing equipment change. “Once it was confirmed that we were upgrading the existing facility instead of building on an alternate site, the Auger upgrade was first on the list,” he said. “Any time there is an opportunity to free up operator time and improve the overall operational process, it should be taken. This was one of those times.” Joe Matias, the Plant’s Senior Operator, elaborated about the time savings and process improvement. “Our routine maintenance of the screenings processing equipment is much easier,” he reported. “It now only takes a half-hour to an hour, while before, it required at least half a day. With the grinder blades now mounted on the unit instead of on its supporting frame below the sewage level, we no longer have to re-direct raw sewage while we pump down the channel to get to the blades.” “Meanwhile,” he continued, “we’ve returned to the 150-250 mg/l BOD levels we need to optimize plant operation, which we had begun to lose, among other benefits, when the original grinding unit showed signs of wear after about five years of service in a plant that does not have a grit remover.” “With the new design featuring stainless steel in place of standard steel and plastic components, we are expecting much longer service life at a high performance level, while pursuing the installation of a separate grit remover that will help further extend the life of the unit, along with other equipment in the plant. We’re now back to filling a bag of processed screenings about the size of a 45 gallon (170 l) drum within two weeks, for easy disposal.” The 1.5 mgd (250 m3/h) plant was originally commissioned in 1963 as a secondary treatment plant with tertiary treatment via ferrous chloride-induced phosphorous extraction. The plant has been through six size upgrades - the latest completed in 2000. It currently serves about 3,500 connections, about 95% residential, and the remainder including saw mills, planer mills and light industrial sites. The plant’s former senior operator, Ed Morris, who retired in 2003, recalled the original installation of the JWC screenings processing equipment, and the benefits it provided. “We had a 150 mm microscreen process to remove biosolids during the primary treatment stage which we trucked to the city’s permitted landfill,” he said. “We joined the regional district landfill when the city decommissioned their site in 1996. Then they shut down their septage lagoon in 1998, and no longer took screenings with biological (fecal) content. So we had to put something into the plant to remove the screenings.” “I had already been interested in the JWC equipment, which I had seen in provincial seminars and trade magazines,” he continued, “since we were getting less than 100 mg/l for BOD, it’s a lot harder to maintain a plant like ours at those levels. We also considered a cutter pump, but had limitations in considering that among other alternatives, because we really couldn’t house any other kind of equipment with our piped-in process laid out on a 60’ x 200’ (18 x 60m) footprint.” “Once installed, we saw immediate results through improved biomass and were able to undertake a six-month optimization of our entire process. With BOD now ranging from 150-250 mg/l, typically at 200 mg/l, we started running more smoothly, and less subject to stress or upset to the biological process.” “Input surges from rain or melt were now less of a problem, and we experienced less clogging of pumps and other equipment by textile, plastic, and rubber solid waste, now being taken care of by the grinder part of the Auger Monster. It also enabled us to get rid of the microscreen, and a press we had for dewatering screenings.” Matias noted additional aspects of the manufacturer’s customer service. “Later, we found JWC to be very receptive to our request for design changes, with their local rep facilitating direct contact with JWC’s technical staff. This was a contrast with other vendors we had known, who tended to regard their equipment as perfect and not want to be bothered, and offshore vendors you couldn’t get through to at all.” “Their local JWC rep, Elaine Connors, from Jelcon, arranged for an exchange of former unit for the upgraded one. She also helped with customs, speeding up a process that could have been quite lengthy,” he added. The unique process of grinding prior to solids separation removes virtually all soft organics (fecal) from the discharged product, reducing odors and landfill costs. Auger Monsters are available with perforated screening troughs with 2, 3 or 6mm openings. The screen is designed to handle heavy solids loading and up to 12 mgd (1900 m3/h) of flow. For more information visit: http://www.jwce.com/ © Copyright 1998 - 2008 Water and Wastewater.com |
