kwh/ep/year of kwh/kg-n Removed Treated effluent 7/07/15 26/08/15 properties Plant electrical energy self sufficiency % Energy Self Supply

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1 Presented by WWTP energy efficiency benchmarking confirms need for continuous improvement Introduction Energy is a large portion of a Wastewater Treatment Plant s (WWTP s) operating costs. Understanding specific energy requirements of a plant and benchmarking against other similar plants is the first step to reducing energy costs and greenhouse gas emissions. In 23/4, the Water Services Association of Australia (WSAA) conducted a first round of specific energy benchmarking of 42 WWTPs across Australia. This study repeated the benchmarking exercise for the 25/6 period and included 245 WWTPs in Australia and Auckland, New Zealand. The purpose of the project was to compare the performance of WWTPs to the previous benchmarking exercise and assess new energy related benchmarks. Method Number of WWTP utilities This study s approach followed current best practice from Germany, tailored to the local water industry. It involved collection of a large volume of from the participating utilities including imported, generated and exported electricity, influent and effluent flow and quality, influent and effluent pumping and sub-metered. An adopted Equivalent Population (EP) was then calculated based on Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Nitrogen (N) loads to the plant. WWTPs were categorised according to size and type based on definitions applied in German WWTP energy benchmarking manuals. Definition of plant types Number of WWTPs Features Activated sludge treatment with separate sludge stabilisation, including those with primary sedimentation, anaerobic digestion (or alternative and on-site energy produced from biogas. 2 Activated sludge treatment with separate sludge stabilisation, including those with primary sedimentation, anaerobic digestion (or alternative) but without onsite co-generation (no onsite energy produced from biogas). 3 Extended aeration activated sludge, including aerobic digestion Sub-types recognised 4 Trickling filters 5 Lagoon and/or wetland systems 6 Rotating biological contactors Breakdown of WWTPs surveyed by Total No = 245 (previous 42) This round Previous round % increase in WWTP participation 7 The following metrics were benchmarked:. A primary benchmark of specific energy use, expressed as kilowatt-hour (kwh)/ep/year; 2. A secondary benchmark measuring the extent of electrical energy self-supply (%); and 3. New benchmarks of kwh per kg of COD and BOD and N. Energy benchmark values adopted for this study were defined for each size and type category as:. Guide s - average (or typical) performance of a WWTP; and 2. s - top performance or current best practice (top %) of a WWTP. Representation of system boundary for WWTP energy use applied in this study. Grid electricity generation and transmission (energy losses) Imported electricity Raw wastewater, influent properties and pumping Treated with main stream Imported waste, properties (eg tanker waste) Co-digested Included Excluded Results Fuel production and transport (energy loss/use) Other fuel uses (eg site maintenance) Imported fuels (gas/liquid) for energy production WWTP electricity use WWTP fuels (gas/liquid), use for electrical energy production Co-generation energy production on site > Biogas > Supplementary fuels Other onsite energy production > Wind > Solar > Other Exported electricity Treated effluent properties and pumping Water recycling (advanced treatment) Recycled water credits (offsets) This study showed that many WWTPs in Australia do not perform as well as their European counterparts in terms of energy efficiency benchmarks. However, slightly more than half the plants that participated in both the previous and current benchmarking round have improved their performance against the benchmarks. Performance of participating plants ranked by specific energy Ranking Top % Above average Number of plants Specific energy (EP/ year) Implications 25 <25 Limited for further energy efficiency improvements or lowering energy use Some Some Below average Bottom % Significant 46 > Opportunities to substantially improve energy reduce energy use, potentially involving revised plant design or operations. >5% of plants that also participated in a previous benchmark round improved their benchmark performance The two figures below are examples of how a WWTP s performance can fluctuate over a year. In this case, the Western Treatment Plant s specific energy (PE/year) met the Guide value but fell short of the value. The plants electrical self-supply (%) was always better than the Guide value but never reached the value. Its specific energy performance had not changed from the previous benchmarking round but improved slightly on its energy self-supply. The plant was highlighted as a top performing plant. EP/Year of kg-n Removed % Energy Self Supply 2 Specific electrical energy consumption and equivalent persons 2 7/7/5 26/8/ //5 4/2/5 23//6 3/3/6 2/5/6 2/6/6 EP/Year Kg-N Removed EP/Year Guide EP/Year Adopted EP Plant electrical energy self sufficiency 3,5, 3,, 2,5, 2,,,5,,, 5, 7/7/5 26/8/5 5//5 4/2/5 23//6 3/3/6 2/5/6 2/6/6 % Energy self-supply % Ess guide value % Ess target value The graph below shows that smaller WWTPs generally use more energy relative to EP and vice versa for the larger WWTPs. Electrical self-supply was a secondary benchmark used in this study. Of the 22 plants with energy self-supply, seven plants achieved the Guide of % and a further two were greater than 5%. Metrics based on kg COD or kg BOD were strongly correlated with the primary benchmark and therefore are not likely to add value. The metric of kg N was less correlated with the primary benchmark. This was attributed to nitrogen being more variable over the range of WWTP types and sizes covered and therefore most likely to provide value as an additional benchmark in a local context. Summary for primary and alternative benchmarks WWTP count kwh (EP.y) kg - COD Equivalent Persons kg - BOD Conclusions While some plants met their respective specific energy benchmark values, there clearly remains room for significant improvement in terms of energy efficiency at many WWTPs. There also remains room energy self-supply when compared to their German counterparts. There is likely value in water utilities improving sub-metering to support the adoption of the proposed benchmark of the power required to remove nitrogen from the treatment process (kg N ). The recommendations for future benchmarking are to: Develop guidelines for augmenting and designing new plants based on energy benchmarks; Propose an additional benchmark based on the metric kg N Host the benchmarking base centrally, allowing users to enter their own and compare WWTP energy performance against industry benchmarks. Acknowledgements The authors would like to acknowledge the support of all water utilities that participated in the benchmarking exercise. The Water Services Association of Australia (WSAA), Intelligent Water Networks, and the Project Delivery Team were also critical in delivering the program to a successful and informative completion. Utilities Treatment Plants NSW 3 44 VIC 7 93 QLD 6 6 TAS WA 2 NZ 2 SA 2 ACT 2 A secondary benchmark of self-supply of energy for WWTPs improved by 7% kg - N % COD % BOD % N % 98% 57% % 93% % % 98% 9% N/A N/A 93% 56% % 82% 76% All % 93% 8%

2 WWTP ENERGY EFFICIENCY BENCHMARKING CONFIRMS NEED FOR CONTINUOUS IMPROVEMENT Keywords Greg Appleby, Nirmala Dinesh 2, George Charakos 3, David De Haas 4, Jennifer Bartle-Smith 5. Sydney Water, NSW, Australia 2. SA Water, South Australia, Australia 3. Melbourne Water, Victoria, Australia 4. GHD Pty Ltd, Brisbane, Australia 5. WSAA, Victoria, Australia Energy, Benchmark, Wastewater, Treatment, Efficiency, Greenhouse, Emissions EXECUTIVE SUMMARY Energy benchmarking of 245 wastewater treatment plants (WWTPs) in Australia and Auckland, was carried out for the period 25 to 26. The study showed that many WWTPs in Australia do not perform as well as their European counterparts in terms of energy efficiency but had improved on average overall compared to a previous benchmarking exercise carried out for the period 23 to 24. The study also highlighted a new benchmark based on energy required for nitrogen, that could be utilised by water utilities in the future. INTRODUCTION Energy is a large portion of a WWTP s operating cost. Understanding specific energy of a plant and benchmarking against other similar plants is the first step to reducing energy costs and greenhouse gas emissions. In 23/4, the Water Services Association of Australia (WSAA) conducted a first round of specific energy benchmarking of 42 WWTPs across Australia. This study repeated the benchmarking exercise for the 25/6 period and included 245 WWTPs in Australia and Auckland, New Zealand. The purpose of the project was to compare the performance of WWTPs to the previous benchmarking exercise and assess new energy related benchmarks. HIGHLIGHTS Participation in the benchmarking exercise increased from 42 to 245 WWTPs A number of plants improved their specific energy performance A secondary benchmark of self-supply of energy for WWTPs improved by 7% Benchmarking the metric kg of Nitrogen by the WWTP will add value A standard collection template and sub metering guidelines were developed. METHODOLOGY/ PROCESS This study s approach followed current best practice from Germany, tailored to the local water industry, and involved collection of a large volume of from the participating utilities including imported, generated and exported electricity, influent and effluent flow and quality, influent and effluent pumping and sub-metered. An adopted Equivalent Population (EP) was then calculated based on organic (BOD and COD) and nitrogen loads to the plant. WWTPs were categorised according to size and type based on definitions applied in German WWTP energy benchmarking manuals. The following metrics were benchmarked:. A primary benchmark of specific energy use, expressed as EP/year; 2. A secondary benchmark measuring the extent of electrical energy self-supply (%); and 3. A new benchmark of kwh per kg of Chemical Oxygen Demand (COD) and/or Biochemical Oxygen Demand (BOD) and/or Nitrogen (N).

3 Energy benchmark values adopted for this study were defined as:. Guide s - average (or typical) performance of a WWTP for each size and type category; and 2. s - top performance or current best practice (top %) of a WWTP for each size and type category. RESULTS/ OUTCOMES Primary Benchmark - (EP.year) This study showed that many WWTPs in Australia do not perform as well as their European counterparts in terms of energy efficiency benchmarks, although slightly more than half the plants that participated in both the previous and current benchmarking round have improved their performance against the benchmarks. 25 WWTP s with specific energy use of less than 25 EP/y are in the top % and approaching or exceeding industry best practice. Such plants are likely to have limited for further energy efficiency improvements or lowering energy use 75 WWTP s with specific energy use between 25-5 EP/y are better than average and are likely to have some lower energy use 24 WWTP s with specific energy use between 5- EP/y are considered to have energy performance around average in the Australian context 75 WWTP s with specific energy use between 6- EP/y are considered to be below average and might have significant lower energy use 46 WWTP s with specific energy use greater than EP/y are amongst the least energy efficient and for these plants, there are to substantially improve energy reduce energy use, potentially involving revised plant design or operations. Secondary Benchmark - % self-supply Of the 22 plants with energy self-supply, seven plants achieved the Guide of % and a further two were greater than 5%. There was a 7% increase in self-supply from the previous benchmarking project. Alternative Benchmarks Metrics based on kg COD or kg BOD were strongly correlated with the primary benchmark and therefore are not likely to add value. The metric of kg N was less correlated with the primary benchmark. This was attributed to nitrogen being more variable over the range of WWTP types and sizes covered and therefore most likely to provide value as an additional benchmark in a local context. Recommendations A number of recommendations are made for future benchmarking including:. Develop guidelines for augmenting and designing new plants based on energy benchmarks 2. Propose additional benchmark values based on the metric kg N 3. Host the benchmarking base centrally, allowing users to enter their own and compare WWTP energy performance against industry benchmarks. CONCLUSION While some plants met their respective specific energy benchmark values, there clearly remains room for significant improvement in terms of energy efficiency on many of the WWTPs. There also remains room to improve energy self-supply when compared to their German counterparts. There is likely value in water utilities improving sub-metering to support the adoption of the new benchmark of the power required to remove nitrogen from the treatment process (kg N ).

4 Figure : WWTPs surveyed in this study compared to previous study, according to ( definitions listed below)

5 Table : Summary of WWTP total plant specific energy performance from this study 4 [45] 2 64 [66] 3 7 [68] 4 76 [68] 5 62 [57] EP/year Minimum EP/year 5 [4] 26 [] 25 [5] 2.5 [].3 [] EP/year Guide [3] [38] 5 [44] 32 [27] 35 [34] EP/year 26 [2] 25 [24] 32 [26] 24 [7] 22 [7] Comments s in parentheses are from the previous WSAA benchmarking round (23-4) Room for improvement in 5% of plants to achieve Guide s plants new plants to this benchmarking exercise plants Room for improvement in most plants Table 2: Proposed (interim) Guide and values for alternative benchmarks based on pollutant specific energy use Data 25-6 Guide Proposed 25-6 Proposed 25-6 Guide Proposed Guide Units: kg COD kg BOD kg N. (.) (.5) 2.2 (2.) (.) (.) (.6) 3. (2.) (.) N/A N/A 3.9 (.4) (.4) (.6) (.2) 3.2 (2.) (.5) summary definitions as follows: : With primary sedimentation, anaerobic sludge digestion and co-generation from biogas 2: With primary sedimentation and anaerobic sludge digestion but without co-generation from biogas 3: Extended aeration activated sludge 4: Trickling filters, including trickling filter-activated sludge combinations 5: Lagoon plants, including aerated lagoons Size summary definitions as folloows: Size Class :, EP Size Class 2: 5, EP Size Class 3: 5, EP Size Class 4:,, EP Size Class 5: >, EP