Top Equipment Picks for Biosolids Dewatering Solutions

Top Equipment Picks for Biosolids Dewatering Solutions
The 1.7-meter trailer-mounted belt filter press system from Bright Technologies

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Conducting studies of biosolids dewatering or drying techniques at your clean-water treatment plant could pay huge short- and long-term dividends. Here we take a look at some of the benefits and solutions to help narrow down your options. 

In lieu of rising landfill costs, many utilities are exploring a host of biosolids management options — from hiring outside contractors, to improving dewatering processes, to exploring energy and other resource recovery approaches. 

Kevin Krejny, wastewater manager for the Greene County (Ohio) sanitary engineering department, discussed these variables recently at the Ohio WEA annual meeting. 

“First, a utility needs to determine if they can do the work in-house, or use an outside contractor,” he says. “In-house dewatering can save money in the long run,” he says, but dewatering in-house and using a contractor to dispose of the solids also works. 

He says land application is usually cheaper if farm fields are close, but it’s handy to have a landfill available as an option.

If you’re in the market for new or different processes, Krejny recommends taking advantage of the trailer- or skid-mounted dewatering test units manufacturers sometimes provide for free. 

One option is the 1.7-meter trailer-mounted belt filter press system from Bright Technologies. The press includes folding conveyor and operator walkways, and it can service multiple sites. Easily transportable and quick to set up, it needs no special lifting equipment. Options include a stainless steel frame, rollers and pans. Units can be customized to particular applications. 

Another choice is Sludge Mate container filters from Flo Trend Systems. Filters are available in roll-off, trailer-mounted and tipping-stand-mounted styles and can dewater wastewater and water treatment plant sludge. Capacities range from 5 to 40 cubic yards. 

FKC skid-mounted dewatering systems can be set up strictly for dewatering or can also be used to heat-pasteurize biosolids while dewatering to achieve Class A product. In this process, lime is added before dewatering to raise the pH to 12 in a separate agitated tank. The liquid biosolids are then pumped with polymer to the flocculation tank on the skid. Flocculated biosolids overflow from the tank into the rotary screen thickener and are then gravity-fed into the screw press, where steam from a small boiler is injected, heating the biosolids to meet the time and temperature requirements. 

Kompress skid-mounted belt filter press systems from Komline-Sanderson are available in 1-, 1.5-, and 2-meter versions with feed pump, polymer system, control panel, belt washwater pump, interconnecting piping, drain pan, and air compressor or hydraulic power unit for belt steering and tensioning. The system only needs to be off-loaded, anchored in place, and connected to utilities. It is available in two- or three-belt designs and can achieve feed rates above 200 gpm. 

Preparation pays off

“Be ready to take and run extra samples of TSS and TVS and such to verify the effectiveness of the demo dewatering units,” Krejny says. “And be ready to have a location that can get power, water, sewer and feed solids within 100 feet to place the mobile device. 

“And remember the upfront cost is very small compared to the long-term costs associated with electricity, polymer, manpower and disposal. Getting the solids 1-2-3 percent drier is also very important if you are shipping to a landfill.” 

The range of biosolids management technologies is large, so be sure to do your homework when you’re in the market.  Other biosolids management options include completely enclosed units, solar units and multi-stage processes. 

The completely enclosed rotary press from Fournier Industries stops odors and can be expanded from one to six channels to accommodate increased flows. Sludge dosed with polymer passes through a variable-speed flocculator to improve settleability. It then enters a circular dewatering channel that slowly rotates and uses backpressure to dewater material through fine mesh screens on both sides of the channel. Dry cake drops to a collection bin or is conveyed away. Once dewatering is complete, the press goes through a 5-minute wash cycle. 

The High Solids Anaerobic Digestion (HiSAD) System from Infilco Degremont uses a two-stage process to treat material at 20 percent solids or higher without mixing, keeping operations and maintenance costs low and improving return on investment. The system is resilient to changes in feed composition. 

IFT rotary drum sludge thickeners from IPEC Consultants consist of a cylindrical drum with a progressive series of screen elements. The drum rotates on four wheels mounted on a structural housing. The smallest openings screen the influent sludge, followed by coarser elements as the sludge thickens. Sludge containing 0.5 to 3 percent solids can be thickened to 3 to 15 percent, depending on the type of sludge. 

The SOLIA drying process from Kruger USA couples air drying and aerobic fermentation. Solar radiation along with a SOLIAMIX automated windrow turner helps water evaporate from the sludge for subsequent removal from the greenhouse. The turner keeps the biosolids aerated and promotes digestion, which produces heat to aid the drying process. Greenhouse drying can reduce the amount of sludge by 60 to 80 percent. 

The ACAT screw press is available in North America through Kusters Water, a division of Kusters Zima Corporation. It provides slow rotational speed, low maintenance, low noise level and low energy consumption. 

The horizontal, solid-bowl (decanter) centrifuge from Noxon North America has a variable-frequency drive design that supplies fully electric drive with the same torque-generating characteristics as units with hydraulic backdrives. It can dewater a wide variety of sludges and slurries to cake solids concentrations with high capture efficiency. Materials of construction include high carbon (50W) steel and stainless 304 and 316, protected with tungsten carbide coatings. 

Future directions

Keep an eye to the future because the clean-water profession is seriously examining innovative options that would maximize the production of energy and recover valuable resources from biosolids. 

A 2011 report by the Water Environment Federation and the National Biosolids Partnership states that concern over climate change is driving new efforts to increase energy production from biosolids and reduce the carbon footprint of treatment facilities. The report also notes new interest in recovering phosphorus and other valuable nutrients from biosolids (“Charting the Future of Biosolids Management” at 

(All equipment listings from TPO Product Focus, August 2013.)


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