Water and Effluent Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/1029923
14 | INNOVATION 2018 T he initial removal of screenings is the im- portant first step in the sewage treatment process. Ef- ficient removal of debris from the incoming flow reduces the maintenance and extends the life of the downstream treat- ment equipment. Initial coarse screens especially on large inlet works with gravity feed, should be considered an essential element to provide a barrier to damage of downstream equipment. A coarse screen with 25mm gap will also remove approximately 20% of the incoming debris, reducing the load on the downstream fine screens. Spirac has two robust coarse screen solutions; CHAINGUARDTM our multi-raked bar screen and RAKEGUARDTM our single articulated rake screen. With channel dimensions and expected incoming flow and screenings loads we can advise the optimum solution for your inlet works. With the initial intercep- tion of influent successfully achieved with a coarse bar screen, we can turn our atten- tion to fine screening. Spirac offers two main screenings solutions BANDGUARDTM and FINE- GUARDTM. The BANDGUARD is a vertical self-cleaning band screen featuring UHMWPE perforated panels in 2-6mm apertures. These robust screens can be mounted in channels up to 20m deep and handle flows up to 2000 lps. The FINEGUARD, an inclined screen has several features to maximise screen- ings removal. Asymmetric stainless-steel screening panels offer the benefit of a step to help retain debris and eliminate rag rolling in front of the screen. The panel profile enhances cleaning by a self-adjusting rotary brush mechanism. This maximises debris removal prior to final washing by a spray nozzle grid. Our latest prefabricated package treatment plant (PTA) project uses three FINE- GUARDTM screens. The plant was designed such that it can be supported on galvanised steel beams elevated ap- proximately 5m above ground level, to enable flows to gravitate through downstream process units. A SANDSEP® grit classifier and two SPIRO- WASH® screenings washer/ compactors are installed on a concrete slab at ground level. The PTA assembly is prefabricated and transported to site in such a manner that minimises installation and requires bolted connections. Sewage enters the inlet flow splitter and then passes over a fixed weir into a cham- ber feeding three FINEGUARD screens. The three fine screens work in a duty/duty/standby configuration to remove >3mm solids from the incom- ing flow. Each fine screen channel contains an elec- trically actuated penstock upstream of the fine screen. The penstock is in the closed position when its correspond- ing fine screen is in standby mode. The fine screens are capable of switching to duty/ duty/duty mode if sewage levels upstream of the fine screens reach a predeter- mined level. Screenings captured by the fine screens discharge to a horizontal shažless spiral conveyor located above the channels. The conveyor transports screenings to two SPIROWASH® screenings washer/compactors via a drop chute. The screenings washers/compactors wash and compact the screenings before depositing them into a screenings bin. Screened sewage passes INNOVATION 2018 from the fine screen channels to the vortex grit chamber where grit is separated from the sewage stream. A grit pump withdraws grit slurry from the grit tank and pumps it to a SANDSEP® grit classi- fier. The grit classifier washes, separates and transfers the grit to the grit bin. As a decades long sup- plier of spiral conveyors and screenings handling equip- ment, the addition of an extensive screen range is a perfect fit to make SPIRAC a single source supplier for the primary wastewater treatment industry. Contact: Spirac House, Thorpe Mead, Banbury OX16 4AB E: conveyors@spirac.co.uk Tel: 01295 270335 Web: www.spirac.com Choosing the right inlet works equipment made easy