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FOCUS—ENERGY AND ENERGY RECOVERYContinued from previous pagethe WWTPs for the City of Vancouver.“Now we can get by with a single turboblower at each treatment plant most of thetime.” The city also installed a variablefrequency drive (VFD) on the water recyclingsystem at its Marine Park facility.Instead of running continuously,the VFD automates pump operation basedon demand, saving an estimated 220,000kilowatt-hours per year (kWh/y).In addition to capital improvements,the city and Veolia learned how to optimizeenergy usage for various systemconditions. By fine-tuning the set pointsof its UV arrays based on flow and dailywater tests, the team reduced its UVenergy consumption by 27 percent, representingnearly 15 percent of the entireload at the WWTPs. “No pun intended,but our UV usage was a matter of overkill,”says Kraft. “We partnered with theESI team, who helped us measure contacttime in relation to flow. We found that wecan use less UV during low flow periodsand still meet our permit requirements.”These changes are saving the facilitiesroughly one million kilowatt hours andtens of thousands of dollars per year. Also,ESI support and utility incentives coveredabout 30 percent of the project’s capital costs.“It’s been great working with ClarkPublic Utilities and BPA,” said Dick. “TheESI program is unbelievably well organized.They included and motivated ourentire staff. They were actively engagedthroughout the process, from baselinetesting to ongoing monitoring. And theycontinually look for additional energy efficiencyopportunities. We’ve been thrilledwith the results.”You may contact Layne McWilliams atlayne.mcwilliams@energysmartindustrial.com.WWTPs providing transportation fuel?Feasibility study underway in OregonBy Matt Krumenauer, Oregon Department of EnergyThis summer Janet Gillaspie from the OregonAssociation of Clean Water Agencies (ACWA), ThadRoth from Energy Trust of Oregon and I were discussingenergy conservation and renewable energy opportunitiesat wastewater treatment facilities. As broad as the opportunitiesare and the depth that Janet and Thad bring to the table,you can imagine the wide ranging discussion we had. Onetopic we discussed in depth was the number of treatmentplants that have recently evaluated their Anaerobic Digestionsystems or would be in the near future. The reasons for theevaluations varied but they all had a decision point in common.Oregon wastewater treatment plants use biogas for processheat and power, and some generate electricity using biogas turbines.But what other opportunities for biogas use existed?One area that has generated interest across the countryis the use of biomethane as a transportation fuel. Janet suggestedthat a few of her members would be interested inspeaking further about this opportunity; therefore we set up abrainstorming session to gage interest. During the meeting, itbecame clear there is interest in evaluating biogas opportunities,and there are other facilities that would benefit.Back at the Oregon Department of Energy, we determinedthat this was definitely an area of interest for the State andan area that we could assist by building a body of knowledgeabout the technology and its application and offer assistanceto not only the clean water industry in the region, but morebroadly to the growing Northwest biogas industry. We were ableto partner with ACWA and its members, Metro, NW Natural,Energy Trust of Oregon, Washington State University, andothers to fund a detailed biogas technology evaluation andfeasibility study.The group selected TetraTech NUS, Inc. to complete the studyand it is currently underway. The first step is to complete atechnology assessment. This will involve a detailed evaluationof biogas purification and upgrading technologies, inventoryhandling and storage requirements, and evaluate available technologiesfor use of biogas in two ways: Injection of upgradedbiogas into the existing natural gas grid, and refueling of naturalgas-powered vehicles. The second step will be an economicevaluation of the available markets, life-cycle analysis and riskassessment, and an analysis of the environmental attributesincluding all regulatory requirements.With this information, a more detailed feasibility analysiswill be completed at four Oregon wastewater treatment plantsin Portland, Gresham, Salem, and Klamath Falls. The feasibilityanalysis will also include an assessment of the currentand potential fleet use and necessary fueling infrastructure.This approach will provide a base of knowledge and a methodologythat can be utilized and replicated by other facilities,including wastewater treatment plants, in the region. We willcomplete the study by the end of February. The final reportwill be released shortly thereafter.You may contact Matt Krumenauer at 503-383-8694 or matt.krumenauer@state.or.us.24 PNCWA NEWSLETTER | WINTER 2011
FOCUS—ENERGY AND ENERGY RECOVERYO&M Energy Efficiency Checklistfor Wastewater Treatment PlantsThe purpose of this list is to help identify no cost or lowcost electricity savings through operation and maintenancepractices at wastewater treatment plants. The list is organizedby System (blower aeration, mechanical aeration, mixing,pumping, etc.) in approximate order from highest to lowestenergy use. Therefore, start at the top of the list and workdown. Because some measures are common to multiple systems,they are repeated, so that each system has a complete list. Pleasereview “Other Measures” on last page, which lists importantideas applicable to the entire plant.Please distribute this open source document to anyone who might be interested, andplease provide comments, suggestions, and new ideas to Walt Mintkeski, P.E., atmintkeski@juno.com, 503-771-0232, in Portland, Oregon.BLOWER AERATION SYSTEM■■Fix air piping leaks. For exposedpipes, apply soapy water to createbubbles. For underground pipes, lookfor air bubbles surfacing through soilduring or just after rain events.■■Reduce air demand—reduce or eliminateair flow to aerated channels andempty aeration basins; reduce airflow to aerated grit chamber; takeexcess aeration basins off line.■■Eliminate air flow restrictions cleanintake air filters, fix sticking checkvalves, open or eliminate throttlingvalves, enlarge undersizedvalves or piping.■■Minimize inlet air temperaturefor centrifugal blowers, especiallythose which draw air from insidebuildings (such as turbo blowers).■■Dissolved Oxygen (DO) ControlSensors—clean and check DOProbe calibration twice a month;airflow meters and pressure sensorsannually.■■Check placement of DO probein basin for representativeDO reading.■■Lower DO set point to lowestpossible setting which results inproper treatment. (That should beless than 2 PPM. However, if eitherammonia or nitrogen removal isrequired, higher set point maybe required, especially duringcold weather).■■Lower blower output pressure byfully opening air valve to highestdemand aeration zone, and thenbalancing other air valves to obtainuniform DO set point concentrationacross remainder of aeration basin;check and tune the settings annually.Use Most Open Valve control strategyfor plants with centrifugal blowersand more than 3 aeration basins.■■Monitor Blower Performance—checkair flow and pressure against blowercurve to determine if units are operatingat most efficient point.■■Identify most efficient blower (highestSCFM/kW) and program controlsto run that unit as primary blower.■■If different capacity blowers are available,program blower operation tomatch diurnal air demand. If blowersare positive displacement units,adjust belts and sheaves to matchoutput to diurnal air demand.■■Monitor SCADA System to identifyif 2 or more blowers operate atreduced speed. Determine if oneunit at higher speed will satisfydemand while drawing less kW. Ifso, take excess equipment off line.■■Diffuser air flow—check CFM/diffuser rate. If it exceeds manufacturer’srecommendation, adddiffusers or reduce air flowper diffuser to restore oxygentransfer efficiency.■■Diffuser maintenance—every week,look for air “boils” which couldindicate broken pipes or diffusers;measure air pressure of eachdrop leg at a set SCFM blowerair flow rate, to detect distributionpiping resistance and diffuserfouling. Remove blockages; flex diffusermembranes with air pulsesor clean diffusers as needed toreduce pressure and increase oxygentransfer efficiency.■■If nitrification is not required, lowerMean Cell Residence Time to 4–5days and turn off aeration systemfrom 1 to 2 hours during the earlymorning low flow period in order toinhibit nitrifying bacteria.■■Convert first zone of aeration basinto anoxic selector. Anoxic zone helpsremove surfactants, which increasesoxygen transfer efficiency.MECHANICAL AERATION SYSTEMS■■Check that the submerged depthof the mechanical aerator is set toproduce the maximum mixing andaeration at a lowest amperage draw.■■Stage unit operation to match DOdemand. If different capacity unitsare available, program operation tomatch diurnal air demand. Use timersto turn units ON/OFF or VFDsto change speed. Take excess unitsoff line.■■Monitor SCADA System to identifyif 2 or more aerators operate atreduced speed. Determine if oneunit at higher speed will satisfydemand while drawing less kW. Ifso, take excess equipment off line.■■Dissolved Oxygen (DO) Controls—Lower DO set point to lowestpossible setting which results inproper treatment (less than 2.0 PPMfor aeration basins and as low as 0.2PPM for aerobic digesters).■■DO probe—clean and check calibrationtwice per month, replaceparts as needed.■■Identify most efficient unit (lbs of O2transferred/kWh) and program controlsto run that unit as primary unit.WINTER 2011 | PNCWA NEWSLETTER 25
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Page 30 and 31: AWARDSWEF & PNCWA Safety AwardsPaul
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Page 36 and 37: KEY VOLUNTEERS—CONTACTSPNCWA BOAR

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