Julian Sandino, PhD, PE, BCEE IWA & WEF Fellow VCS Denmark Mads Leth Per Henrik Nielsen Carsten Steen Soren Eriksen Niels M. Askjær CH2MHILL Dru Whitlock Tom Johnson Tim Constantine Dwight Houweling • Nitrification increases O2 demand – Longer sludge age during low temperature increases biomass endogenous demand and larger aeration volume also requires additional mixing – NH3-N conversion to NO3-N typically doubles O2 demand • Denitrification only partially recovers O2 • Unaerated zones for Bio P and Denitrification require mixing energy • Low Nutrient requirements could require filtration (extra pumping?) • Effective primary treatment reduces carbon load to subsequent BNR basins, while increasing potential for energy recovery from sludge – Carbon needs for denitrification and P-removal must be addressed (external carbon? WAS fermentation/hydrolysis?) • Carbon present in sludge offers opportunity for significant energy recovery : CHP Cogeneration • Established in 1853 as first modern waterworks in Denmark • 3rd largest water and wastewater company in Denmark. HQ in Odense. • Operates 7 WTPs and 8 WWTPs with 3,400 km of conveyance Courtesy of Google Maps (Altered by CH2MHILL) ø • 385,000 PE BNR facility • 76% energy self-sufficient in 2011 • Contribute towards achieving VCS’s corporate goal of energy self-sufficiency and carbon neutrality by 2014. • Identify energy optimization opportunities (EOOs): concentrate on short-term, readily implementable scenarios to reduce consumption and/or increase generation, decreasing GHG emmissions • Identify and document all options, including longer term opportunities for positive net energy status for future consideration Ejby Mølle WWTP 2011 Annual Average Electricity Consumption Thickening/Dewatering Centrifuges 6.44% Anaerobic Digestion 3.83% Sludge Storage 1.56% Activated Sludge - Other 0.24% Screen, Grit, and Grease Primary Treatment Pumping to 3.88% 3.09% Trickling Filters Other 2.15% 5.59% Pumping to Activated Sludge 5.80% Trickling Filters Stage 2 pumping 7.30% Effluent Filters 10.43% Activated Sludge WAS Pumping 0.22% Activated Sludge RAS Pumping 0.86% Activated Sludge Oxidation Ditch Mixing 2.09% Trickling Filters Recirculation pumping 4.73% Trickling Filters WAS/Humus Pumping 0.01% Trickling Filters - Return Pumping to Act Sludge 0.64% Activated Sludge Oxidation Ditch Aeration 39.35% Activated Sludge Anaerobic Zone Mixers 1.78% • Adopted screening criteria – Readily implementable; Primarily process modifications – Significant impact on energy profile; Proven elsewhere • Longer term Improvements for – Implement chemical enhanced positive net energy status • Short-listed EOOs primary treatment (CEPT) – Operate at shorter BNR system solids retention time (SRT) – Decommission TFs and convert TF clarifiers to CEPT for wet weather treatment – Reduce effluent filtration operation to 12 hours per day – Co-digestion of high strength waste by mid 2014 – Implement deammonification for N removal in sidestreams by 2014; mainstream by 2015 – Replace oxidation ditch mechanical aerators with fine bubble diffused aeration Energy Produced 2011 Additional Energy Produced Additional Energy Saved All Operational EOOs + Anammox + Diffusers All Operational EOOs Partial Effluent Filtration Lower Bioreactor Sludge Age No Trickling Filters Energy Self-Sufficiency Chemically Enhanced Primary Treatment Existing Condition (Baseline) 75% 80% 85% 90% 95% 100% 105% 110% 115% 120% Electrical Energy 9,000,000 8,000,000 7,000,000 6,000,000 5,000,000 4,000,000 3,000,000 2,000,000 1,000,000 kWh/year - Production Usage 25,000,000 2014 2013 2012 15,000,000 Production 10,000,000 2014 2013 2012 2011 5,000,000 kWh/year 2010 Electrical + Heat Energy Usage 2009 2011 2010 2009 20,000,000 • Full-scale evaluation of co-digestion with organic waste • Implementing sidestream and mainstream deammonification for N control • Developing “hybrid” aeration concept by combining mechanical and diffused aeration systems High-strength waste increases biogas generation Co-digestion in Anaerobic digesters Energy Recovery from cogeneration (heat and electrical) Sidestream deammonification Mainstream hydrocyclones • Plant-wide mass and energy balance model used to evaluate operational and facility energy optimization scenarios • Collaborative approach identified “operational” path to energy selfsufficiency • Co-digestion and deammonification (sidestream and mainstream) capabilities will yield positive net energy status by end of 2014 • VCS is well into achieving adopted goal of achieving energy and CO2 neutrality VCS & CH2MHILL and Project Team Project received 2013 WEX Process Optimization award
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