Blending blowers to reduce total cost of ownership

Problem: The wastewater treatment plant in Letchworth, United Kingdom, sought a blower system with a lower purchase price, superior turndown and high aeration efficiency.

Solution: A blended blower system from Atlas Copco Compressors included a ZBVSD+ high-speed turbo blower to handle the baseline aeration demand and three ZSVSD screw blowers to provide aeration trim for diurnal loading.

Result: The capital cost was 28 percent lower than an all-turbo-blower system. The turndown of the blended blower system is 21-1, versus the 9-1 aeration control an all-turbo system could provide. With the efficiency of the screw blower at low flow, the blended blower system efficiency is 50 percent greater at minimum design flow. Aeration efficiency during off-peak times is about 15 percent lower than the system as designed with only turbo blowers. 866-546-3588; www.atlascopco.us

Blending blowers to reduce total cost of ownership

Problem: The wastewater treatment plant in Letchworth, United Kingdom, sought a blower system with a lower purchase price, superior turndown and high aeration efficiency.

Solution: A blended blower system from Atlas Copco Compressors included a ZBVSD+ high-speed turbo blower to handle the baseline aeration demand and three ZSVSD screw blowers to provide aeration trim for diurnal loading.

Result: The capital cost was 28 percent lower than an all-turbo-blower system. The turndown of the blended blower system is 21-1, versus the 9-1 aeration control an all-turbo system could provide. With the efficiency of the screw blower at low flow, the blended blower system efficiency is 50 percent greater at minimum design flow. Aeration efficiency during off-peak times is about 15 percent lower than the system as designed with only turbo blowers. 866-546-3588; www.atlascopco.us

Chopper pump aids in de-ragging at plant

Problem: De-ragging at a wastewater treatment plant near Houston had become a tough, twice-weekly chore, requiring six to eight hours per week for two people. Every blockage meant unscrewing the bottom part of the pumps because the impellers would not move.

Solution: The plant installed a 24.5 hp Landia Chopper Pump. Landia can retrofit its pumps onto the base elbow used for the pump awaiting replacement using only four bolts.

Result: Since the chopper pump was installed, there have been no blockages. Previously, site engineers had to use up a 5-gallon container of anti-greasing chemical every two weeks at an annual cost of $4,000 to reduce the buildup of FOG. This is no longer necessary. 919-466-0603; www.landiainc.com

Water reclamation facility revitalizes biosolids piston pump

Problem: Tres Rios Water Reclamation Facility, owned by Pima County in Tucson, Arizona, installed three truck-loading silos from Schwing Bioset in 2013. The intent was to deliver biosolids at 22 percent solids to the silos using progressive cavity pumps. However, the pumps could not pump the material. Adjusting the centrifuges and adding water to reduce the solids content to 15 percent enabled the pumps to transport the cake but created issues upstream and added cost.

Solution: A KSP 25 piston pump from Schwing Bioset had been in service until the completion of the truck loading facility. The plant staff worked with Schwing Bioset to rebuild that 15-year-old pump and replace one of the progressive cavity pumps. 

Result: This enabled transport of the higher-solids material to the loading silos. The remaining pumps and centrifuges are being used for thickening. 715-247-3433; www.schwingbioset.com

Rural collections system simplifies lift station maintenance with aboveground systems

Problem: The city of Perryville, Missouri, employs a small staff to manage its lift station network. The submersible pumps were unreliable and required time-consuming confined-space entry and frequent pump replacements.

Solution: The city now operates six Wet Well Mounted Pump Stations from Smith & Loveless. All pumps, valves and controls are housed above ground and outside the wet well. “You don’t have to be in the wastewater and dealing with all the hazardous situations,” says Linda Chappius, maintenance technician.

Result: Chappius inspects each station daily without confined-space entry, helping simplify its pump station maintenance program and extend station life. The first station, installed in 1995, is still in operation. “It’s been a tremendously good lift station,” Chappius says. “For where it’s located and what it goes through for day-to-day use, it’s an excellent piece of equipment.” 800-898-9122; www.smithandloveless.com

Chopper pump used to clear wet well of grease blanket

Problem: The Otay River Pump Station, which pumps 7 to 9 mgd of raw sewage to the South Bay Water Reclamation Facility for water recovery in San Diego had a problem in the 50-foot-long, 10-foot-wide, 30-foot-deep wet well. A floating blanket of grease and debris, sometimes as thick as 4 feet, would form regularly. The city was hiring two vacuum trucks to clean the station every three to four months at a cost of $50,000 to $100,000 per year.

Solution: Based on good experience with Vaughan chopper pumps, the city turned to that company again. The pumps are suitable for use in pump and lift stations as conditioning pumps when fitted with a nozzle to provide high-velocity mixing. They were placed in the problem wet well on a portable stand to recirculate and chop the contents. The company selected an 8-inch submersible chopper pump with a 25 hp, 1,200 rpm motor with mixing nozzle and portable stand.

Result: In 18 months of use, the wet well has not required cleaning. The pump paid for itself in 2 1/2 months. 888-249-2467; www.chopperpumps.com