2. WASTE DISPOSAL

3. Types of Waste Inert wastes - no chemical or biological hazards Special (hazardous) wastes e.g. –ignitable, corrosive, reactive –Carcinogenic or mutagenic (PCBs, medical waste, radioactive waste, asbestos) –heavy metals, azides, acids/alkalis

4. Landfill Sites Many old landfills are poorly designed and major environmental hazard. They are not designed for 50, 100 or 1000 years into the future There are 4000 operational and 4000 closed landfill sites in the UK Two types of landfill in the UK are leach and disperse (old sites) containment and treatment (new sites)

5. What Happens in a Landfill Site? Rain water dissolves & reacts chemically & biologically with waste Leachate Landfill Gas

6. Leachate toxins kill aquatic life eutrophication in rivers precipitates iron kills vegetation pathogens/bacteria non-hazardous materials can decompose into hazardous products serious groundwater pollution

7. Landfill Gas methane

8. Landfill Gas Loscoe, Derbyshire - 1986

9. Landfill Gas Loscoe, Derbyshire - 1986

10. Possible Routes by Which Landfill Gas Can Migrate from a Site Caves & natural cavities Highly permeable strataFissured & fractured strata Mine shafts Gas vents Tree roots Highly permeable strata Underground services e.g. sewer pipes Desiccation cracks in soil

11. Landfill Site Selection Geology of Area Porosity & permeability of rock Resistance to weathering Joints & fracture systems in rock Dip of rock strata (no dip or synform) Hydrogeology of Area Rate of groundwater flow Gradient of groundwater flow Depth to water table Fluctuations of groundwater Impermeable to contain leachate & landfill gas Reduce groundwater contamination from leachate Topography of Area Existing hole or steep sided quarry Free from disturbance (tectonic/subsidence) A site capable of retaining waste

12. Groundwater Hydraulic Gradient Groundwater Pore spaces Joints/fractures Water Table Recharge Saturated zone

13. Aquifers Impermeable rock Groundwater Pore spaces unsaturated Pore spaces saturated

14. What rocks in the UK make good aquifers? Sandstone 40% porosity 30% specific yield High permeability Clay 45% porosity 3% specific yield Low permeability

15. Impacts of pumping water from aquifers

16. Drawdown Hydraulic Gradient Cone of Depression

17. Impacts of pumping water from aquifers Saline wedge Control – reduce/stop abstraction, change pattern of abstraction ( winter not summer) or move borehole Monitoring – chemical testing (boreholes/salinity testing)

18. two feet of compacted clay strong, flexible, very thick plastic, called high density polythene (HDPE) known as a geomembrane. one-foot layer of gravel with pipes running through it. The leachate collects in these pipes and is pumped out of the landfill and filtered. very tough fabric, called a geotextile fabric, to protect the pipes. top layer is about one foot of compacted soil to protect the entire liner system from the waste. Each evening, large trucks roll over the landfill to crush the day's rubbish and then cover it with 15cm of soil so the waste doesn't smell or attract flies and rats. When an area of the landfill is completely full, it is capped with clay and soil. This final landfill cover helps keep rainwater out of the waste and reduces the amount of leachate that forms. Site Preparation Modern Landfill Site

19. Site Management & Monitoring monitoring groundwater for chloride & ammonia in plumes monitoring unsaturated zone for gases venting of methane gas by boreholes porous pipes to transfer leachate into sumps for collection & removal

21. Site Restoration Uses Parkland Recreation Open spaces Greenbelt Low level industrial development Housing

22. Site Restoration Trumps Farm is a former sand pit which was used by Surrey County Council for the disposal of household waste from the early 1980s until its closure in 1998. The overall objective of the works is to reinstate the landfill to pasture and meadow, to a landscape typical of the area and create a variety of wildlife habitats.

23. Site Restoration Problems Methane gas hazard – leakage through permeable rocks Ground instability on completion - subsidence Groundwater pollution Landfill site needs to remain accessible for over 25 years to manage & monitor

24. Agriculture Nitrates Pesticides Industry Chemical leaks Chemical spills Contamination from chemical storage Waste Disposal Leachates from landfill sites Radioactive waste Contamination of aquifers

25. Chloride content (milligrams per litre) of leachate Monitoring chemical testing of water from boreholes, springs, extraction wells ground penetrating radar (remote sensing methods) electrical resistivity analysis (oil pollutants = high resistivity) soil gas chemical monitoring (organic pollutants give off a vapour such as methane) borehole Most expensive Cheapest

26. Contamination of aquifers 1. Control clay liner synthetic liner leachate collection total containment

27. Contamination of aquifers 2. Control build barriers to plume trenches filled with concrete hammered piles injected with cement grout Barrier to predicted depth of pollution Pollution localised 10 – 20m max

28. Contamination of aquifers 3. Control pump pollutant to surface for treatment/disposal

29. Contamination of aquifers 4. Control direct polluted groundwater into to bioreactive barrier bioreactive barrier use naturally occurring bacteria to breakdown the pollutant oxygen & nitrates injected into barrier to encourage decay processes factory pollutant Impermeable wall to direct groundwater Bioreactive filter

30. Non-hazardous Waste Disposal Landfill Sites Factors Affecting Site Selection Site Management & Monitoring Site Preparation What happens in a landfill site Pollutants Problems of Leachate Problems of Landfill Gas Problems after site is restored

31. Hazardous Waste What are hazardous waste materials? What specific problems do they cause? What factors need to be taken in to account with hazardous waste disposal? What are the options for their disposal? (examples)

35. Possible Routes by Which Landfill Gas Can Migrate from a Site