Solid Waste Management Chapter 5

1. Solid Waste ManagementChapter 5 HS 425

2. Sources of Solid Wastes • Residential • Commercial • Institutional • Construction and demolitions • Municipal services • Treatment plant sites • Industrial • Agricultural

3. Characteristics of Solid of Wastes • Composition • Quantities • Specific Weight

4. Integrated Waste Management • IWM is the selection and application of suitable techniques, technologies and management programs to achieve waste management objectives. • Strategies set by EPA for IWM: • Source reduction • Recycling and composting • Combustion (sate-to-energy) • Landfills

5. Source Reduction • Consumers • Federal and state levels • Private sectors • Material design • Increase durability • Substitute w/less toxic material • Increase product effectiveness • *****Most efficient at the product/process design phase

6. Recycling and Composting • Returning raw material to the market • Saves precious resources • Stretches landfill capacities • Improves ash efficiency and quality in incinerators by removing non-combustible material • Improves compost quality by removing non-compostable material (glass, plastics) • Can be problematic if not handled properly • e.g. Recycling oils, solvents, etc… • e.g. Composting pesticide-contaminated grass clippings contaminating ground water

7. Combustionor Waste-to-Energy • Incineration of wastes. • Reduces the volume of wastes dramatically up to nine fold (1/9th) • Energy may be recovered in the form of steam or electricity • Stretches landfill capacities • Avoids high transportation costs to far-located landfills • Disadvantages: • High cost • Highly sophisticated for safe and economical operation • Public skeptical about their safety

8. Landfill Types • The Trench method • Used in level terrain. • Trenches are dug by excavation • Solid waste is filled in the trenches & dirt is replaced on top of the buried material • Trench is then compacted • The Area method • Most popular • By locating a side of a hill or a sloped area • Refused is dumped on the side of the slope and then covered with dirt • It continues until the entire slope is leveled • The Valley or Ravine method • Commonly used by large cities • In an area with large depression or slope such as a valley or ravine • Usually an area naturally developed • Refuse is dumped in the depression and filled with dirt • The area is then compacted and built up

9. Landfill Classification • Class 1 landfills • – hazardous materials accepted • Class 2 landfills • – low level hazardous materials accepted • Class 3 landfills • – no hazardous materials accepted

10. State of a Landfill • A) Aerobic state: 4-60 days • B) Anaerobic: after 60 days • – Produces methane, carbon dioxide and hydrogen sulfide gases as anaerobic decomposition products • In a well-run landfill: • Methane/carbon dioxide ratio is between 65% and 35% • Hydrogen sulfide is <1% • *** Landfills get inspected at least once a month. • *** Leachate is the liquid waste coming out of the ground at refuse landfills.

16. Landfill Cost Categories • Pre-development • Construction • Operations • Closure • Closure Care

17. Landfill Cost 1,000 TPD Site • Pre-development • $2,600,000 phase cost X 3 sites = $7.9 million • Construction • $29 million lump sum • Operations • $3.3 million per year X 20 years = $66.3 million • Closure • $7.6 million lump sum • Post-Closure Care • $680,00 per year X 30 years = $20.4 million

18. Modern MSW Landfills • Carefully engineered system • Designed to protect both ground & surface water • System of liners • Leachate treatment system • Designed to vent gases generated • Vent pipes

20. Landfill Reclamation • Relatively new approach • Started in the U.S. in the 1980’s

21. Landfill Reclamation • Potential benefits • Extending Landfill Capacity at the Current Site • Generating Revenues From The Sale of Recyclable Materials • Lowering Operating Costs or Generating Revenues From The Sale of Reclaimed Soil • Producing Energy at MWC • Reducing Landfill Closure Costs and Reclaiming Land for Other Uses

22. Landfill Reclamation • Potential Drawbacks • Managing Hazardous Materials • Controlling Releases of Landfill Gases and Odors • Controlling Subsidence or Collapse • Increasing Wear on Excavation and MWC Equipment

23. Modern MSW Landfills • Daily cover • – 6 inches • - compacted to prevent fly larvae emergence • Final cover • – 24 inches • 3. Slope of the landfill cell • - 2:1 rise over run ratio (results in a 26.3 or 30 grade) • 4. Must be at least 200 feet away from lakes and streams • 5. Must be at least 5090 feet away from human habitation • Citing landfill sites should be for duration of at least 30-40 years • Completed landfills can be used for parks and golf courses • Open dumps are illegal in the U.S. • If landfill is too far for vehicles to dump daily, use transfer stations

24. Modern MSW Landfills • Operated to protect against vermin & vectors • Operated to prevent fires • Covered daily with soil • Groundwater monitoring • When full • Closed to be safe • Monitoring

25. Cover Types • During landfill operations, cover is usually applied daily • Controls disease vectors • Controls vermin • Prevents odors • Prevents fires • Discourages scavenging • About 6” of compacted earth • The type of soil is not critical

26. Example of a Liner Requirements Filter Layer of Fabric Pea Gravel 12” 4” Leachate collection pipes to sump, then to water treatment 60 mil thick synthetic plastic liner Clay 36” Filter Layer of Fabric 4” Leachate collection pipes to sump Pea Gravel 12” 60 mil thick synthetic plastic liner 12” Clay Bedrock

27. Cover System • Prevents the infiltration of water • Need to consider • Soil type • Degree of compaction • High organic soils do not compact easily • Surface slope • Increases runoff • Drainage • Water balance

28. Engineering Controls • Liners • Placed on the bottom and sides of the landfill • Reduces the migration of leachate to groundwater • Covering after closing also helps to keep rainwater from percolating thru the landfill

29. Engineering Controls • Leachate removal and collection systems • Pipes collect the leachate which settles on the top of the liner • Prevent the leachate form migrated to groundwater • A series of perforated collection pipes • Usually 4 to 6” PVC • Drainage layers • Filters • Header pipes • Sumps and sump pumps • Treatment

30. Engineering Controls • Leachate removal and collection systems • Pipes placed over the liner in drainage layers filled with sand or gravel • In landfills with double liners, pipes are located both above the top liner and between the top and bottom liners • Liners are usually designed with a slope so that the leachate drains into a control collection point • Typical leachate generation is 10 to 100 gallons per acre per day

31. Landfill Gases • Methane • Explosive and a global warming gas • Can be flared • Landfilled gas is 50% carbon dioxide and 50% methane plus trace organic chemicals • Anaerobic decomposition produces methane

32. Methane • Engineering control options • Vented • Flared • Recovered • Landfilled methane is equivalent to approximately 5% pf the natural gas consumption in the U.S. or approximately 1% of the total energy demand • Less than 200 landfills recover energy

33. Health Risks • Release of potentially toxic substances • Releases of leachate to groundwater • Releases of leachate to surface water • Emissions of volatile gases into the atmosphere

34. Composting It is the natural process of plant nutrient recycling, returning nutrients back into the soil. Plant material (grass, leaves) are broken down by bacterial decay and result in the formation of nutrients. As decay progresses, fungus, mold and protozoas enter the decomposition process. Towards the end of the decomposition, millipedes, beetles and earthworms complete the process. It reduces waste down to 20% by volume. It results in HUMUS- not a fertilizer but a soil conditioner (keeps soil oxygenated and loose for water absorption) Needed conditions: Moisture, Bacteria, New materials, Plants only.