Case Study Wastewater > Source of Renewal Energy

Transcription

1 Case Study Wastewater > Source of Renewal Energy 15 December 2015 Xiaohua CHEN Engineering Director Veolia Water Technologies Asia

2 Table of Content 1. Link between Wastewater treatment and Sludge treatment 2. Case Study Qingdao Maidao WWTP, China 3. Case Study Urumqi WWTP, China 4. Conclusion

3 1. Link between Wastewater treatment and Sludge treatment Link with wider possibilties 3

4 The Changing Way We See Wastewater o Yesterday Treat wastewater, Minimise sludge for disposal o Today & Tomorrow Treat waste water to higher standards Reuse wastewater Maximise sludge production Recover renewable sustainable resources; energy, fertiliser, nutrients, plastics o This impacts the way we should design treatment plants waste water and sludge are linked successful resource recovery depends on appropriate WWTP design Sludge, and Anaerobic Digestion, are the key elements for energy production 4

5 Classical WWTP approach Low Load Activated Sludge Clarifier River Screening Sand, Greases Thickening Dewatering Key features of this kind of plant: o Simple o Large footprint o Low sludge production o High energy consumption o Produced sludge has low biomethane potential o Final sludge cake with a low dryness 5

6 WWTP Design for Energy Recovery High Efficiency Primary Biofilm process River Screenings Sand, Greases Thickening Dewatering Key differences: o High Efficiency Primary Settler o Biofilm process o Total Produced Sludge Quantity increased o Sludge Quality increased for energy production o Energy consumption in biological step reduced 6

7 WWTP Design for Energy Recovery Total Sludge Quantity Conventional Design for Energy Recovery 50% higher Primary 0 % 60-80% Secondary 100% 40-20% Energy consumption Gas Production Potential Final sludge CAKE quantity 40% lower (but chemical cost added) 60-70% higher 25-30% lower after digestion (Lower TDS, higher dryness) 7

8 Scheme of sludge strategy 8

9 2. Case Study Qingdao Maidao WWTP, China 9

10 Maidao WWTP Type of process: Multiflo TM Trio and Biostyr Nominal Capacity: 140,000m 3 /day Collection area: 35 KM 2 No of inhabitants served: 706,000 Area Occupied by facilities: 3.9ha Operation of Maidao extension: July 2007 Operation staff on site: 52 10

11 Process Diagram Water Line PRE- TREATMENT GRIT & GREASE REMOVAL MULTIFLO Trio Remove large insoluble material Remove grit, grease and grains more than 0.2mm BIOSTYR UV DISINFECTION Carbon and Nitrogen pollutions removal Coliform removal 11

12 Mesophilic Digestion + Co-generation Hot water Electricity: up to 69 % self sufficiency 12

13 Digesters Total sludge:48,674kgss/d Sludge concentration:38g/l Mini retention time:20d Number:2 Diameter:29.3m Cylinder height:18m Unit useful volume:12700m 3 13

14 Cylindrical Digesters 14

15 Mesophilic digestion: mechanical mixer Low energy consumption, easy for installation and high efficiency 15

16 Digester Heating Dual fuel boiler Tube type heat exchanger 16

17 Biogas Handling Double membrane gas holder Gas flare Technical data: Volume:2500m3 Diameter:17.8m Height:14.4m Retention time:4h 17

18 Co-generation Gas engines Number of co-generator:4 Mode of consumption:internal use Elec output:1,200-1,600 kw 18

19 Year 2009 main operation data costs FeCl 3 dosing rate 25mg/l = RMB/m 3 Sludge dryness > 4% VSS content > 60% Yearly gas production: 5,422,589 m 3 Biogas boilers are operated only 227 h/year, sludge heated by heat recovered from power generation during the rest of time Electricity produced: 10,103,477 kwh/y, a saving of > 850 k EUR/y Specific power consumption: kwh/m 3 or 0.01 EUR/m 3 PRESENTATION TITLE / SUBTITLE / DATE 19

20 Key Features and Benefits High biogas production: 14,400 15,000 Nm 3 /d ( m 3 /d) Specific biogas production: 900 l/removed kgvss Low H2S content without specific desulfurization system: < 20 ppm o Dosing of FeCl3 in primary treatment result in: 2 Fe S 2-2 FeS + S Green energy: 65% of overall electricity needs produced from biogas CH4, which has 21 times higher Carbon Footprint than CO2 is consumed and not released into the atmosphere 15,000 Nm 3 /d corresponding to t CO2/year emission avoided 20

21 3. Case Study Urumqi WWTP, China Lorem ipsum dolor sit amet, elit. Proin porttitor consequat velit, ac aliquam enim faucibus eu.

22 Urumqi Hedong Digestion & Co-generation Digester Qty: 6 (4 for phase 1, 2 for phase 2) Biogas production: 41,225 m 3 /d 3x500 kw co-generators 2x500 kw biogas drive air blowers repaired and put into service

23 Urumqi Hedong WWTP phase 1 digestion refurbishment Original information: 4 digesters with a capacity of 7500 m 3 each - Mixers were delivered from Finland in The digesters were commissioned around 1998 Digesters have been stopped since 2006 until Veolia refurbishment in 2010

24 Possible causes of Hedong digesters system failure Various mechanical problems on mixers (up to shaft of mixer damaged) may be due to design installation operation maintenance. Sand found in the bottom of digesters -> link with water line operation Operation and maintenance

25 Urumqi Hedong WWTP phase 1 digestion refurbishment Veolia s solution Design revue and modification of the existing digestion system by our Engineering Dept with support of Technical Dept in VEOLIA. Repair or replacement of some equipment in bad situation or strategic equipments (mixers, pumps, piping ), replacement of instrumentation, specific checking and repair on digesters and equipment. Supervision of all mechanical installation by VWT and suppliers. Commissioning of digestion system by VWT commissioning engineers.

26 Actual situation after refurbishment o o o 4 digesters are in good conditions of operation since end of A preventive maintenance plan has been set up by the Operation Co. Biogas production is according design. Quality of biogas is good and can be used now to run: - All boilers - Phase 1 biogas drive air blowers - Co-generation system have been constructed, VW plan to start it this year. 26

27 Key points about digestion refurbishment o Existing digestion condition should be considered carefully (link with cost & safety). o Some equipment are critical. They have to be replaced by new ones (mixers, safety devices, ) in order to ensure the success of projects. o Safety should be considered at design stage. 27

28 VWT added value Support from VEOLIA France experts at design stage, installation and commissioning. High consideration of safety. Strong experience in digestion Design, Built, Refurbishment. Implementation of new system around digestion (biogas treatment system, co-generation, other sludge treatment system). The use of these new system can generates cost saving or revenues.

29 4. Conclusions There are many opportunities in the sludge treatment market: - Renewable energy production: The generation of biogas is gaining in productivity across EU (target of 20% total gross electricity consumption in 2020). Anaerobic digestion (AD) generates renewable energy through biogas production. There s renewable energy incentive policy (tax credit) in many countries in Europe and USA. - Nutrient recovery from sludge cake. This area has a lot of potential because the value of fertilizer prices. - There is growth potential in the treatment of return liquors, because they have high concentrations of nutrients.

30 Thank you for your attention