Cost effective energy usage at Himmerfjärdsverket sewage treatment plant in Sweden. Malin Tuvesson and Lars Gunnarsson SYVAB Himmerfjärdsverket, SE Grödinge, Sweden. Mats Holmberg and Christian Rosen Industrial Electrical Engineering and Automation (IEA), Lund University, Box 118, SE Lund, Sweden.

LG2 Content Energy usage: SE, GE About SYVAB, Himmerfjärdsverket Energy balance Simulation tool, scenarios, sensitivity Conclusions Actions taken Results

LG3 Sewage treatment in Sweden Total used energy; 930 GWh –Electricity; 630 –Other; – 3 kWh electricity / kg BOD 90 – 100 kWh electricity / pe / year

LG4 Sewage treatment in Sweden Energy production; GWh –Biogas; 600 –Heat; 2.500

LG5 Sewage treatment in Germany Electricity; 45 kWh / pe / year Heat; 45 kWh / pe / year

LG6 Sewage treatment in Germany Electricity 50% of Sweden and estimate a 30% decrease, to 30 kWh / pe / year

LG7 Himmerfjädsverket

LG8 Himmerfjärdsverket, WWTP 4,500 m3/h 300,000 p.e. 7,000 t DS/a no major industry N-reduction –1984 –1997 Start up 1974 BOD 15 (8) ppm COD 70 ppm tot-N 10 ppm tot-P 0.5 (0.3) ppm

LG9

10 50% 41% Pumping 25% 42% 17% Aeration Diffuse Electrical energyBiogas energy Sludge dryer Heating boilers Flare

LG11 Himmerfjärden WWTP

LG12 Electricity GWh –Inlet pumps 50 % –Aeration 25 %

Electricity cost of operational cost 2006: 21 % 2007: 27 %

LG14 Himmerfjärdsverket 2006 Biogas production; 3.5 MNm 3 –500 Nm3/t DS treated –1,000 Nm3/t DS reduced Oil; 5 m3

LG15 Biogas ,5 mNm3, 23 GWh –Sludge drying17 % –Heating digesters28 % –Heating buildings14 % –Flare41 %

LG16 Himmerfjärdsverket 2006 Total energy used: 41GWh –0.74 kwh/m3 treated water –1.11 kWh/m3 drinking water sold –1.9 kWh/COD-red

LG17 Simulation Model

Model input Biogas production Sludge dryer Heating demand Electrical energy cost Biogas value LG18

LG19 Simulation Model INPUT VARIABLES

LG20 Model parameters Biogas engine –Power, efficiency, etc. Heat pump –Size –temperatures Heating –Efficiency Vehicle fuel production –Volume –price

LG21 Simulation Model GAS ENGINE HEAT PUMP DRYER GAS BURNER DIGESTERS BUILDINGS OIL VEHICLE FUEL

LG22 Model output Energy balance –Biogas –Heating Financial results –Revenue –Costs –Total balance

LG23 Simulation Model GAS BALANCE HEAT BALANCE FINANCIALS

LG24 Simulation model, scenarios A - Thickening of sludge to digester B - Heat pump on reject C - Gas engine –500 kW –300 kW D - Vehicle fuel production

LG25 Simulation Model

LG27 Conclusions Efficiency increase of pumping Thickening of sludge to digester No heat pump No electricity from biogas Mechanical energy from biogas engine Vehicle fuel production

LG28 Actions Modernize inlet pumps New centrifuge for sludge thickening Gas engine and a new blower Contract to provide gas for vehicle fuel Introduce deamonification

LG29 Deamonification

LG30 Deamonification

LG31 Results Inlet pumping efficiency –decreased energy cost with 5% Thickening – 25 % reduction in heating Gas engine –Reduction in total electricity demand 10 % –Reduced costs for heating Vehicle fuel –Income / Nm3 biogas produced Deamonifiction –Reduced cost of N red. with 15 %

LG32 Target Energy efficiency and Biogas sale by 2011 to reduce costs equivalent to 2/3 of energy costs 2007

LG33 Summary, SYVAB Energy –Energy source –How to utilize –To produce –Legislation

LG34 Summary, SYVAB Methodology for investigation –Modelling tool –Scenarios –To understand & communicate Cost impact

LG35 Summary, SYVAB Actions –Pumps –Heating –Biogas –New process technology

LG36 QUESTIONS ?