Energy Management and Sustainability

Energy Management and Sustainability
Cogen plant uses methane from wastewater plant

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Control system automatically monitors phosphorus levels

Problem
Operators at the Beaver Dam (Wis.) Wastewater Treatment Plant had to feed enough ferric chloride to handle phosphorus spikes. To meet a 1.0 mg/L total phosphorus limit, they had to be careful not to overfeed, increasing sludge production and wasting chemical. The operators constantly monitored the phosphorus levels.

Solution
The RTC-P Chemical Phosphorus Control System from Hach Company now automatically optimized ferric feed, delivering the exact amount of precipitant needed to maintain an orthophosphate setpoint. By measuring effluent flow and orthophosphate in real time, the controller uses programmed algorithms to adjust the dose ahead of the clarifiers as the phosphorus load changes.

Result
Previously, the staff maintained an average ferric chloride dose of 12.5 gph. After the installation, the average feed was 5.55 gph, a savings of 56 percent. The savings paid for the system in less than 12 months. The staff no longer has to monitor phosphorus levels. 800/227-4224; www.hach.com.

Double-tube heat exchangers rectify blocking issues

Problem
Severn Trent Water continuously dealt with spiral heat exchanger blocks, resulting in low efficiency and high maintenance costs. The problem led to replacement of the exchangers on the digesters. Replacement units had to fit the space available. Both sides of the replacement exchangers had to produce pressures to suit existing equipment, and the design needed to have minimal impact on existing site pipe work. The exchangers had to resist clogging with raggy sludge and meet thermal requirements efficiently, reliably and with minimal maintenance.

Solution
HRS Heat Exchangers recommended DTI Series industrial double-tube heat exchangers, a tube-in-tube design with tubes sized to allow large particles and raggy sludge to pass through. The internal tube is corrugated, creates turbulence that improves heat transfer coefficient and reduces the risk of fouling.

Result
The heat exchangers brought an end to the blocking problems and increased digester efficiency. 623/915-4328; www.hrs-heatexchangers.com.

Self-cleaning filter enables treatment plant to utilize nonpotable water

Problem
The Throop Wastewater Treatment Plant at the Lackawanna River Basin Sewer Authority in northern Pennsylvania went through a series of upgrades in 2012 that called for increased use of nonpotable water. It became important to ensure that the water did not contain particles that would clog equipment.

Solution
Design engineers selected the Forsta Self Cleaning Filter, sized to treat effluent for use throughout the plant. The A6-LP180I model offers 3 square feet of screen area, uses a 1-inch flush valve, has a cleaning duration of 15 to 20 seconds and requires 13 gallons of water per cleaning cycle. The filter came with a stainless steel 250-micron wedge-wire screen to handle the fibrous particles that originate intermittently from the source water.

Result
The filter was set to clean on a timer at 30-minute intervals or when a preset differential pressure was reached. This happens rarely, indicating that the filter was properly designed and sized. 888/936-7782; www.forstafilters.com.

Cogen plant uses methane from wastewater plant

Problem
The La Salina Wastewater Treatment Plant processes about 20 percent of sewage from the City of Oceanside, Calif. The methane produced in the process was being flared off, placing the city at risk of violating Southern California’s strict air-quality standards. The city also faced steadily rising electricity costs.

Solution
City officials turned to CHP Clean Energy to build, own and operate a 150 kW digester-gas-fired cogeneration plant at no cost or risk to the city. Rather than waste methane, the process uses it to generate electricity and reduce reliance on natural gas. The fuel-conditioning system from BioSpark reduces engine maintenance and increases output.

Result
The system reduced energy costs by $625,000 over the initial contract period. 508/934-6904; www.chpcleanenergy.com.

LED lighting helps wastewater facility improve visibility, reduce energy consumption

Problem
The wastewater treatment facility in Santa Cruz, Calif., processes 10 mgd on average. With hundreds of fixtures to light its exterior 12 hours a day, the facility used high-pressure sodium and mercury vapor fixtures. The poor-quality light hindered visibility and reduced the image clarity for the closed-circuit security system. The fixtures needed constant changes of bulbs and ballasts, which led to costly hazardous material disposal.

Solution
The facility chose Dialight to replace 82 fixtures in its solids dewatering building, pre-aeration building and trickling filters with DuroSite LED fixtures. The entire change-out took five days — 30 to 60 minutes per fixture. The lighting was outfitted with photocells and timers, taking advantage of the instant-on capabilities.

Result
The facility reduced lighting energy usage by more than 50 percent, significantly lowered its CO2 emissions and dramatically improved visibility, enhancing security. With each fixture expected to last up to 10 years, the retrofit has reduced lighting maintenance. With a rebate through a utility incentive program, the project will pay for itself in three years. 732/919-3119; www.dialight.com.

Efficient blowers increase aeration and save electric costs

Problem
The wastewater treatment plant located in Meriden, Conn., was outdated, with its last update in the early 1980s. A major facility upgrade was needed to make sure operating efficiencies and effluent quality remained at the highest levels possible. The goal was to find more efficient blowers to upgrade the aeration system.

Solution
Three turbocompressors from Sulzer Pumps were chosen to increase the efficiency of the aeration system: two ABS turbocompressors HST 40 (one operating and one as backup), and one ABS turbocompressor HST 2500. Life cycle cost analysis had determined that over an estimated 20-year product life, these would save the plant over $1 million.

Result
As well as radically decreasing noise levels, the ABS turbocompressors paid for themselves in six months. With their precise variable-speed operation, this plant has actually increased aeration activity by 25 percent, while using 20 percent less electricity. In addition, the plant has saved a great deal on maintenance, which now involves only an annual air filter change and replacement of the cooling fans every five to six years. 800/525-7790; www.sulzer.com.

Solids-handling pump warns of seal issues

Problem
The Village of Bradford, Ohio, had a duplex lift station with 6-inch discharge pumps rated for 700 gpm at 66 feet. The pumps were failing from mechanical seal leaks. Jay Roberts, primary operator, needed a pump that would warn of impending seal problems, be faster and less expensive to repair and resist clogging.

Solution
Crane Pumps & Systems provided a 4SHMD solids-handling pump with a 25 hp motor, a slide rail adapter that fits the current base elbow assembly and a MiniCAS replacement relay. The device connected to the existing control panel and warns of seal issues with an alarm connection to the SCADA system.

Result
The village has had no mechanical seal failures or clogging since the pump was installed in June 2010. 937/615-3544; www.cranepumps.com.

Chopper pump eliminates build up of fat and wipes

Problem
Thames Water was experiencing stormwater-handling problems at its East Hyde sewage treatment works near Luton, just north of London. Pump blockages were caused by buildup of wet wipes and food fat.

Solution
Operators installed a 6-inch MPTK-I 150 series chopper pump from Landia. The 30 kW, 1,500 rpm pump is suited for the wastewater and sludge with coarse solids.

Result
The plant has had no more blockages. Guide traces in the pump’s MPTK casing ensure that no dry matter particles are caught. Thames Water has since purchased two more Landia units. 919/466-0603; www.landiainc.com.

Wastewater treatment plant puts water harvesting to good use

Problem
The wastewater treatment plant in Romeoville, Ill., used large volumes of potable water for operations. To reduce potable water usage, operators decided to reuse final effluent for a variety of functions.

Solution
Based upon design suggestions by Metropolitan Industries, the plant was upgraded to include a packaged plant water system. Final effluent is pressurized, distributed to various locations and used to wash raw sludge screens, rinse grit-collectors, wash down the sidewalls of excess-flow storage ponds and feed plant hydrants for general washdown.

Result
The upgrade has already saved considerable potable water and will reduce freshwater demands on the growing Chicago suburb for many years. 815/886-9200; www.metropolitanind.com.

Wind turbines provide power for ‘off-grid’ farms’ water and wastewater systems

Problem
Several off-grid farmers near North Kohala, Hawaii, needed a clean, low-cost alternative to diesel fuel to generate electricity for water and wastewater pumping.

Solution
The owners installed a microgrid that includes a Northern Power 100 wind turbine with sophisticated voltage controls and no inrush current. The system includes a battery bank and solar panels. It can pump more than 30 million gallons annually.

Result
The system has proven successful in irrigating 400 acres of agricultural land supporting 14 farms and agricultural businesses. 877/906-6784; www.northernpower.com.

Management system solves pump run-time issues

Problem
The City of Winter Park, Fla., was experiencing excessive pump run times and unacceptable pressures because of multiple lift stations pumping into a single force main.

Solution
The city implemented Symphony - Harmonious Pump and Flow Management from Data Flow Systems. It coordinates systemwide operation of lift stations to reduce force main pressures and equalize flow. It corrects the random operation of stations and synchronizes pumping on a minute-by-minute basis.

Result
The city saw diminished pump run times, lower maintenance and energy costs, fewer service calls and longer pump life. The system also resolved daily peak flow and pressure spikes. Research continues to improve the pumping algorithm. Initially, the system reduced average run-time reductions by 24 percent and energy costs by 39 percent. Recent run times are reduced 34 percent and energy costs 42 percent. 321/259-5009; www.dataflowsys.com.

Data-entry system saves on manpower

Problem
The wastewater treatment facility in Lafayette, Colo., was doubling its data collection work. The daily manual inspections were being done on paper in the field, after which data was entered to the computer.

Solution
The plant turned to FlexSystems to automate the process. Operators using the FlexOps system carry PDAs to capture the data and drive standard operating procedures. The touch-screen PDA is used to scan barcodes at inspection points and pieces of equipment. The software then leads the operator through the inspection with a simple question-and-answer format. Logic flow functionality guides operators through troubleshooting or repairs.

Result
Data entered on the PDAs is automatically pulled into customizable reports emailed to management. Reports include time and date stamps for all actions and exception reports that include all nondefault responses entered. The system saves labor and shows reliable and legally defensible reports for state and EPA compliance. 303/684-8303; www.flexops.net.

Sewer district values familiarity in plunger pump replacement

Problem
In 1963, The Greater Chillicothe (Ill.) Sewer District purchased two Komline-Sanderson Model KSS-9-1 simplex 9-inch plunger pumps to transfer primary sludge to its anaerobic digester. The district decided to replace one of the 50-year-old pumps during a project to replace a digester cover.

Solution
Because of experience with the pumps and two additional K-S Model KS-11-1 plunger pumps purchased in 1993, the district, through Baxter & Woodman, specified the same Komline-Sanderson pump. The pumps transfer 90 gpm of primary sludge at 3 to 5 percent solids to an anaerobic digester at discharge pressures of 30 feet TDH for about 30 minutes a day.

Result
The pumps have worked well. “These pumps are indestructible,” said David Day, plant superintendent. 800/225-5457; www.komline.com.



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