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Effects of leachate recirculation on anaerobic treatment of municipal solid waste by Chayanon Sawatdeenarunat.

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Presentation on theme: "Effects of leachate recirculation on anaerobic treatment of municipal solid waste by Chayanon Sawatdeenarunat."— Presentation transcript:

1 Effects of leachate recirculation on anaerobic treatment of municipal solid waste by Chayanon Sawatdeenarunat

2 Municipal Solid Waste (MSW) Municipal Solid Waste (MSW) Municipal Solid Waste (MSW) Predominantly household waste Predominantly household waste The addition of commercial waste The addition of commercial waste which are collected by a municipality within a given area.

3 MSW management

4 Characteristics of MSW in US (2005) Food waste 9.8% Food waste 9.8% Yard trimming 9.6% Yard trimming 9.6% Paper & paper board 39.6% Paper & paper board 39.6% Glass 4.7% Glass 4.7% Metal 7.8% Metal 7.8% Plastic 11.2% Plastic 11.2% Wood 6.6% Wood 6.6% Total MSW generated 340 million tons Total MSW generated 340 million tons

5 Landfill is a site for the disposal of waste materials by burial and is the oldest form of waste treatment is a site for the disposal of waste materials by burial and is the oldest form of waste treatment

6 Leachate is the refuse from landfills is the refuse from landfills The compositions vary regarding the age of each landfills and characteristics of MSW The compositions vary regarding the age of each landfills and characteristics of MSW High COD, sulfate and metal ion High COD, sulfate and metal ion Anoxic, acidic Anoxic, acidic

7 Anaerobic digestion

8 Effects of leachate recirculation on organic compounds removal Conventional landfills Conventional landfills Washed out Washed out Bio-conversion Bio-conversion Bioreactor landfills Bioreactor landfills Accelerated bio-conversion Accelerated bio-conversion

9 Effects of leachate recirculation on organic compound removal

10 What are the benefits of leachate recirculation on organic compound removal? Increase moisture content Increase moisture content Enhance hydrolysis stage Enhance hydrolysis stage Enhance contact between organic compounds and microorganism Enhance contact between organic compounds and microorganism Recirculate organic compounds Recirculate organic compounds Recirculate methanogen microorganism Recirculate methanogen microorganism Reach stabilization more rapidly Reach stabilization more rapidly

11 Accelerated biodegradation

12 Effects of leachate recirculation on landfill gas production and methane content Methane production increase in recirculating landfills Methane production increase in recirculating landfills The acceleration of organic compounds removals The acceleration of organic compounds removals Return organic compounds Return organic compounds Improve methanogenic activities Improve methanogenic activities Methane content is not significantly change Methane content is not significantly change High recirculation rate High recirculation rate Cause acid accumulation Cause acid accumulation inhibit methanogen microorgsnism inhibit methanogen microorgsnism Reduce methane production rate Reduce methane production rate

13 Methane production and methane content

14 Effects of leachate recirculation on metal concentration Metal precipitation Metal precipitation In the beginning (acidogenesis stage) In the beginning (acidogenesis stage) pH is between 4 and 6 pH is between 4 and 6 High solubility of metal High solubility of metal Reach stabilization (methanogenesis stage) Reach stabilization (methanogenesis stage) pH is between 7 and 9 pH is between 7 and 9 Metal sulfide and metal hydroxide precipitate Metal sulfide and metal hydroxide precipitate Metal concentration in MSW Metal concentration in MSW Higher due to the accumulation of precipitated metal Higher due to the accumulation of precipitated metal

15 Effects of leachate recirculation on metal concentration Conventional landfills Conventional landfills Need longer time to reach methanogenesis stage Need longer time to reach methanogenesis stage Remove less metal from leachate when compared with bioreactor landfills at the same time Remove less metal from leachate when compared with bioreactor landfills at the same time Bioreactor landfill Bioreactor landfill Increase contact between waste and leachate Increase contact between waste and leachate Remove metal from leachate more effectively Remove metal from leachate more effectively

16 Metal concentration in leachate

17 Metal concentration in MSW

18 Other mechanisms of metal removal from leachate Other mechanisms of metal removal from leachate Subsequent capture within waste metrix by encapsulation Subsequent capture within waste metrix by encapsulation Sorption Sorption Ion-exchange Ion-exchange filtration filtration

19 Study in full-scale landfills Properties of landfill facilities

20 BOD and BOD:COD & Time reach methanogenesis stage within 6 years reach methanogenesis stage within 6 years

21 pH & Time

22 Metal concentration in leachate Metal concentration is below standard within 13 years Metal concentration is below standard within 13 years

23 Gas flow rate (production rate) About 60% higher in bioreactor landfillsAbout 60% higher in bioreactor landfills

24 Disadvantage Accumulation of NH 3 -N Accumulation of NH 3 -N Leakage of Nitrification bacteria Leakage of Nitrification bacteria NH 3 + O 2 → NO 2 − + 3H + + 2e − NH 3 + O 2 → NO 2 − + 3H + + 2e − NO 2 − + H 2 O → NO 3 − + 2H + + 2e − NO 2 − + H 2 O → NO 3 − + 2H + + 2e − Leachate should be pre-aerated off site before recirculation Leachate should be pre-aerated off site before recirculation

25 NH 3 -N & Time

26 Disadvantage Accumulation of Cl - in leachate Accumulation of Cl - in leachate

27 Recirculation Strategies The balance of biological process and hydraulic capacity of the waste The balance of biological process and hydraulic capacity of the waste Recirculate slowly before reaching methanogenesis stage Recirculate slowly before reaching methanogenesis stage To prevent acid stuck which could inhibit methanogen bacteria To prevent acid stuck which could inhibit methanogen bacteria To prevent bacteria washed out To prevent bacteria washed out Initiated as soon as possible following waste placement Initiated as soon as possible following waste placement To ensure the appropriate moisture content of biodegradation To ensure the appropriate moisture content of biodegradation

28 Recirculation Strategies Leachate should be recirculated uniformly Leachate should be recirculated uniformly To prevent short circuiting To prevent short circuiting To Increase contact between leachate and MSW To Increase contact between leachate and MSW

29 Thanks and Questions


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