Biosolids Management And Headworks

Biosolids Management And Headworks
Vertical screening system installed in challenging headworks

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Vertical screening system installed in challenging headworks

Problem: Four years ago the Mendocino (Calif.) City Community Services District needed to make a change at its 1 mgd wastewater treatment plant. The headworks equipment wasn’t getting the job done. “It would reduce some solids to a smaller size but would pass everything through,” says the district’s supervisor, Steve Acker. All nonbiodegradable materials had to be manually removed. Otherwise, it would simply pass through the process or accumulate elsewhere in the facility.

Solution: The Screentec vertical screen from Aqualitec Screening Equipment matched the district’s technical requirements and footprint constraints. The unit had to accommodate a 12-foot-deep headworks design, serviced by an 8-foot-diameter manhole.

Result: With the vertical screen in place, solid waste accumulation dropped to a fraction of former levels. Personnel no longer had to manually clean out solids, which reduced labor costs and exposure to hazardous conditions. The screen has required no servicing since its installation. 855/650-2214; www.aqualitec.com.


Dredge system utilized to tackle sedimentation issue

Problem: The 3.4 mgd water treatment plant in Tiffin, Ohio, built in the 1920s, faced turbidity fluctuations from 10 to 2,000 NTU. Coagulation was enhanced in the 1990s to meet regulations, but that increased sedimentation rates and exacerbated solids blanket depths. Winter proved to be problematic as icy conditions limited access, resulting in short-circuiting. The plant sought to eliminate the need to remove tanks for cleaning.

Solution: In 2010 the plant installed a SedVac sediment dredge system from Brentwood Industries. The system can fully clean the basin floor and keep up with solids production. Minimal modifications to the basin made the retrofit cost-effective.

Result: The basins now require cleaning twice per year instead of every three weeks, saving $65,000 per year. The system enabled extension of the backwash interval from 24 hours to 120 to 168 hours, conserving 50,000 to 75,000 gallons of treated water per day. 610/374-5109; www.brentwoodindustries.com.

 

Continuously cleaned bar screen solves algae issue, reduces maintenance

Problem: After installing a UV disinfection system, the City of Monroe, Mich., found that algae was flaking off final tanks and into the discharge, causing blockage on the UV modules and breaking the quartz lamps. Maintenance grew to one to two days each week spent hand-cleaning lamps from 18 modules.

Solution: The city chose the FlexRake FPFS from Duperon Corporation for algae removal. It already used the simple, low-maintenance screen as a preliminary screening solution. “We knew the screen would be reliable. We’re able to run it 24/7, a continuous operation,” says Randy Sommers, maintenance supervisor.

Result: The screen’s continuous operation allows algae and other small particulate matter to mat for effective removal. The debris blade at the discharge cleans each scraper as it passes, eliminating the algae concern. “We’ve had no issues whatsoever since the installation back in 2007,” says Sommers. “In fact, I haven’t had to do a thing since we installed it.” 800/383-8479; www.duperon.com.


City chooses turnkey screw pump replacement

Problem: The City of Fort Myers (Fla.) Wastewater Treatment Division includes two regional advanced wastewater treatment facilities, each with three 11 mgd carbon steel Internalift screw pumps. The pumps were approaching their 20-year life expectancy, were inefficient and needed replacing. The city wanted corrosion-resistant material and needed to continue operating during construction.

Solution: A turnkey proposal from the Davco team at Evoqua Water Technologies included six Internalift screw pumps, ancillary materials and construction. The pumps’ closed design improves safety and confines odors and splashes while providing access for maintenance, prolonged bearing life and the ability to lubricate critical components while in operation.

Result: The city replaced the pumps under a single contract completed on time without site interruption. An 18-month schedule allowed both treatment plants to operate during construction. The corrosion-resistant materials are expected to extend screw pump life. 229/227-8734; www.evoqua.com.


Center flow screens help plant increase flushable wipe capture

Problem: A wastewater treatment plant in New Orleans needed to protect downstream equipment by increasing screenings capture, including the screening of flushable wipes, but could not sacrifice flow capacity or increase headloss beyond the existing 1-inch-opening rake screens.

Solution: The utility selected center flow screens with 6 mm stainless steel laced links from Hydro-Dyne Engineering. Their center flow technology has a high screening capture ratio, and they capture a high volume of solids while minimizing headloss. Because the facility had tight overhead clearances, equipment was supplied modularly for easy installation and required no modifications to the channel.

Result: The screens increased the capture rate, with zero carryover, while maintaining high capacity and minimizing headloss. Each screen passes 60 mgd and captures the flushable wipes. Integral washing compactors deliver a clean and dewatered product for disposal. 813/818-0777; www.hydro-dyne.com.


Biosolids dryer helps produce Class A product, increase treatment capacity

Problem: The Picnic Point Wastewater Treatment Facility in Edmonds, Wash., was reaching process capacity. Hauling and incinerating biosolids was difficult and expensive. The city wanted Class A biosolids to alleviate those concerns and be more environmentally conscious.

Solution: The facility implemented the Veolia BioCon Dryer from Kruger USA at its new activated sludge plant, which also uses membrane bioreactors.  Dried biosolids can be used by a third party to fertilize farmland.

Result: With the dryer the plant doubled its treatment capacity, ensuring that the site can handle increased biosolids loads. It yields a lower volume of biosolids that are safely and easily handled. The solution was executed in a small footprint and yields a valuable end product. 919/677-8310; www.krugerusa.com.


Fine screen system helps city reduce fouling

Problem: Since 1998, the City of Prince Albert, Saskatchewan, had relied on three Channel Monster units from JWC Environmental to capture and grind the solids at the wastewater treatment plant headworks. In recent years, facing an increase in rags fouling equipment, officials decided to remove the rags and other inorganic solids before they entered the treatment system.

Solution: The city chose a Fine Screen Monster with StapleGuard ultra-high molecular weight (UHMW) panels coupled with a Screenings Washer Monster from JWC Environmental. The bacteria-resistant and self-lubricating UHMW panels are abrasion- and impact-resistant for durability and reduced maintenance. The panel construction eliminates the need for a rotating brush to clean off screenings.

Result: Since the installation in May 2014, the city has solved its ragging problem and improved process efficiency. Inorganic solids are removed, ground, washed and compacted by the Screenings Washer Monster, allowing the city to send dry, compacted solids to the landfill. 800/331-2277; www.jwce.com.


Dosing system helps remove odor from potable water

Problem: United Utilities in Rochdale, United Kingdom, needed to add powdered activated carbon (PAC) to the water it drew from a reservoir. The PAC neutralized geosmin, an organic compound produced by microbes and algae that gave the untreated water a harmless but undesirable earthy taste and aroma.

Solution: A dosing system provided by Spiroflow Systems Inc. included a bulk bag discharger and a flexible screw conveyor to transfer PAC from the discharger up to a volumetric metering feeder with a buffer hopper above. From there, it is transferred to a second buffer hopper, which maintains a constant head of material above a venturi ejector. PAC is drawn under vacuum from the second buffer hopper and metered proportionately into a bypass water stream to form a slurry, which then re-enters and is mixed with the main water flow.

Result: Now free of the undesirable taste and smell, the PAC-treated water is distributed to homes and businesses in the area. 704/246-0900; www.spiroflowsystems.com.


Centrifuges help plant increase cake solid percentage

Problem: The City of Flint, Mich., sought to maximize cake solids over the average 18 percent aging belt filter presses were producing with digested sludge. 

Solution: The city and the state of Michigan partnered with BioWorks Energy to construct anaerobic digesters at the city’s wastewater treatment plant. Two DC20 horizontal solid-bowl centrifuges from Noxon North America were installed to replace a pair of belt filter presses. Each unit runs between 80 and 100 gpm, processing solids consisting of municipal sludge and food processing byproducts.

Result: The centrifuges provide cake solids concentrations in the 25- to 28-percent range. The extra dryness translates into disposal savings, which coupled with biogas-fueled energy production, puts the plant at net zero energy consumption. 416/843-6500; www.noxon.com.


Wireless temperature monitoring system utilized to compost biosolids

Problem: One of the largest municipal compost facilities in North America, located in California, was having mass failures with its wireless temperature monitoring system due to the stainless steel stems corroding and the enclosures failing to keep corrosive gases out of the enclosure.

Solution: REOTEMP Instruments installed an EcoProbe wireless temperature monitoring system that included a nonmetal sheath to protect the stainless steel stem from corrosion. It has a triple seal to ensure that biosolids compost gases are kept out of the enclosure and cannot damage the internal electronics.

Result: Over five years after initial installation, the wireless probes continue to provide reliable temperature data in the harsh indoor compost environment. The customer is pleased with their performance and has recommended the system to multiple facilities in the years since. 800/648-7737; www.reotemp.com.


Municipality installs dewatering system to produce Class A biosolids

Problem: The Immokalee Water and Sewer District, about 30 miles inland from Naples, Fla., operates a 4 mgd facility where biosolids were dewatered before being hauled to a landfill by a contract company at a cost of almost $500,000 per year. The district sought a more efficient alternative.

Solution: The district selected Schwing Bioset, Inc. to dewater and produce Class A biosolids for use on a district-owned 300-acre farm. A screw press dewaters the material to 20 percent solids. The material is then transferred through a piston pump into an alkaline stabilization reactor. Within an hour, Class A fertilizer is discharged to a spreader taken to the adjoining farm for daily land application. The automated system demands little operator interface.

Result: The district saves almost $400,000 a year, achieving an expected payback at about five years. Beneficial use of the material offsets commercial fertilizer costs. 715/247-3433; www.schwingbioset.com.


Smart-conveying pump lowers maintenance costs

Problem: The City of Hays, Kan., wastewater treatment facility needed to replace an old piston pump with new technology to convey primary biosolids and intermittently drain the primary clarifier’s grease pit. The piston pump caused maintenance and housekeeping issues, had long lead times for replacement parts and would be excessively costly to replace.

Solution: The city installed a BN 35-6LS progressive cavity pump equipped with Smart Conveying Technology (SCT) from SEEPEX Inc. The SCT design splits the pump stator axially and integrates a retensioning device that when adjusted increases service life. It speeds up rotor and stator changing and allows removal of blockages and contaminants without dismantling piping.

Result: “We wanted to get away from various maintenance issues, primarily the mess the piston pump would make when packing wore out or when we used it for emptying the grease pit,” says Roger Moerke, wastewater superintendent. “The SEEPEX pump came in under budget, performs both functions cleanly and empties the grease pit twice as quickly. We have yet to perform maintenance on the pump after it has been installed for three months, and we will be able to adjust the stator three times before a replacement stator is needed.” 937/864-7150; www.seepex.com.


Increase in flow to plant requires upgraded grit removal

Problem: Plans called for closure of one of three wastewater treatment plants in the City of Baton Rouge, La., saving an estimated $36 million a year in operation and maintenance. The diversion of the flows from the closing plant required overhaul of the nearby South Wastewater Treatment Plant, and project leaders sought a more efficient screening and grit removal system able to handle capacities up to 205 mgd.

Solution: To achieve 95 percent grit removal, project leaders specified the  PISTA 360 hydraulic vortex grit removal system  from Smith & Loveless, Inc. The six grit chambers have a flat chamber floor, internal baffling and low-energy axial-flow propeller. The internal baffling directs the inlet flow into the chamber with a 360-degree rotation. In the outlet, it directs the flow out of the unit and acts as a slice weir to control water levels. No additional downstream flow control device is required to keep an acceptable velocity, even during low flow periods.

Result: The system went partially online in March 2013. Initial grit testing to evaluate grit removal performance demonstrated removal efficiency of 97.9 percent down to a 105-micron particle size. 800/898-9122; www.smithandloveless.com.


Belt press helps village reduce biosolids disposal costs

Problem: The Village of Fort Simpson in Canada’s Northwest Territories upgraded its sewage treatment facility to improve capacity and performance. The facility needed a dewatering technology suitable for processing solids produced from the new sequencing batch reactor plant.  The northern location limited biosolids management options. Because a plant operator is not always on site, the dewatering process had to require minimal operator oversight.

Solution: The village decided to install a VFOLD INC. folding belt press as a simple and economical dewatering method. A rotating drum thickener combined with Maxi-V folding belt press accepts slurry feed at 0.5 to 8 percent solids.

Result: Dewatering produces filter cake up to 18 percent solids for transport to a landfill. The equipment capital payback is forecast at 1 1/2 years. 877/818-3653; www.vfoldinc.com.  



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