ENVIRONMENTAL ENGINEERING (506)-Module 3.pptx

Lecture slide

1. CVE 506 SOLID WASTE MANAGEMENT

2. Example 8.3 : Analysis of a hauled container system Solid waste from a new industrial park is to be collected in large containers, some of which will be used in conjunction with stationary compactors. Based on traffic studies at similar parks, it is estimated that the average time to drive from garage to the first container location (t1) and from the last container location (t2) to the garage each day will be 15 and 20 min, respectively. If the average time required to drive between containers is 6 min and the one-way distance to the disposal site is 15.5 mi (speed limit: 55 mi/h → a = 0.016 h/trip b = 0.018 h/trip), determine the number of containers that can be emptied per day, based on an 8-h workday. Assume the off-route factor, W, is equal to 0.15.

3. 5/8/2023 CVE 506 Prepared by Ado Mohammed 3

4. 5/8/2023 CVE 506 Prepared by Ado Mohammed 4

5. 5/8/2023 CVE 506 Prepared by Ado Mohammed 5

6. 5/8/2023 CVE 506 Prepared by Ado Mohammed 6

7. Example 8.3 Analysis of a hauled container system Solution Determine the pick-up time per trip: P hcs = pc + uc + dbc pc: time required to pick up loaded container, h/trip uc : time required to unloaded empty container, h/trip pc + uc = 0.4 h/trip (from Table 8-5) dbc : time req. to drive between container locations = 6 min/trip = 0.1 h/trip P hcs = pc + uc + dbc = 0.4 + 0.1 = 0.5 h/trip

8. Example 8.3 Cont. Analysis of a hauled container system Solution Cont. Determine the time per trip: Thcs = Phcs + s + h = Phcs + s + a + bx s: at site time = 0.133 h/trip (from Table 8-5) a = 0.016 h/trip b = 0.018 h/trip T hcs = 0.5 + 0.133 + 0.016 + 0.018(31) = 1.21 h/trip Determine the # of trips that can be made per day: N d = (H(1-W)-(t1+t2))/ T hcs N d = (8h/d (1-0.15)-(0.25h+0.33h))/1.21 h/trip N d = 5.14 trip/d ≈ 5 trips/d

9. Solid Waste Disposal Disposal of solid wastes is defined as placement of the waste so that it no longer impacts society or the environment. The wastes are either assimilated so that they can no longer be identified in the environment, as by incineration to ash, or they are hidden well enough so that they cannot be readily found.

10. Until the environmental movement emerged in the 1960s, most wastes were disposed of with little or no control: to land, as open dumping; to air, by burning or evaporation of volatile compounds; or to water, by discharging solids and liquids to surface, groundwater or the ocean.

11. METHODS OF SOLID WASTE DISPOSAL AND MANAGEMENT Here are some common methods of solid waste disposal and management:- 1) Solid Waste Open Burning 2) Sea dumping process 3) Solid wastes sanitary landfills 4) Incineration method 5) Composting process 6) Disposal by Ploughing into the fields 7) Disposal by hog feeding 8) Salvaging procedure 9) Fermentation/biological digestion 10) Controlled Tipping/Burying 11) Discharge to sewers 12) Open dump

12. Sanitary landfilling Sanitary landfilling is the compaction of refuse in a lined pit and covering of the compacted refuse with an earthen cover. Typically, refuse is unloaded, compacted with bulldozers, and covered with compacted soil. The landfill is built up in units called cells. The daily cover is between 6 and 12 in. thick depending on soil composition, and a final cover at least 2ft thick is used to close the landfill

13. The characteristics of sanitary landfill that distinguish it from an open dump are: The waste is placed in a suitably selected and prepared land fill site in a carefully prescribed manner ii. The waste materials is spread out and compacted with appropriate heavy machinery iii. The waste is covered each day with a layer of compacted soil • It is effective method for permanent disposal if there is enough land and equipment • Useless lands become useful (hills, valleys) e.g. flat land for recreation N.B. It may not be appropriate in rural areas because of highly skilled professionals require for proper operation, planning, regulating and controlling and deposition of solid wastes on selected areas.

14. Arrangement of Cells in a Sanitary Landfill

15. MODERN LANDFILL

16. Unlined Landfills and Groundwater Contamination

17. Diagram of a Sanitary Landfill

18. Sanitary landfilling operation The sanitary landfilling operation involves numerous stages, including siting, design, operation, and closing.

19. Siting Restrictions The landfill disposal regulations provide the following restrictions on landfill location: Prohibit the placement of a landfill facility near an airport because of dangers from scavenging birds. Require the landfill to be located outside the 100 year floodplain or the landfill design must prevent the washout of solid waste during a 100 year flood. Prohibit the placement of a new landfill or expansion of an existing landfill into or on a wetland . Prohibit the placement of a landfill within 200 feet of an earthquake fault. Prohibit the placement of a landfill in an area with a high probability of a strong earthquake . Prohibit the placement of a landfill in an area with unstable soil . Require existing landfills which cannot meet the airport, floodplain, or unstable area requirements above, to close within five years. The state may grant a maximum of a two year extension.

20. Siting Landfills Siting of landfills is rapidly becoming the most difficult stage of the process since few people wish to have landfills in their neighborhoods. In addition to public acceptability, considerations include: Drainage: Rapid runoff will lessen mosquito problems, but proximity to streams or well supplies may result in water pollution.

21. Wind: It is preferable that the landfill be downwind from any nearby community. Distance from collection. Size: A small site with limited capacity is generally not acceptable since finding a new site entails considerable difficulty. Rainfall patterns: The production of leachate from the landfill is influenced by the weather. Soil type: Can the soil be excavated and used as cover?

22. Depth of the water table: The bottom of the landfill must be substantially above the highest expected groundwater elevation Treatment of leachate: The landfill must be proximate to wastewater treatment facility Proximity to airports: All landfills attract birds to some extent, and are therefore not compatible with airport siting. Ultimate use: Can the area be used for private or public use after the landfilling operation is complete?

23. Sanitary Landfill: Federal Legislation Provisions

24. Operational Requirements Exclusion of hazardous waste from the landfill. Provide at least six inches of daily soil cover over new solid waste placed in the landfill. Control disease vectors such as rodents and insects. Monitor methane concentrations in the landfill and buildings. (Methane is explosive when combined with the oxygen in air .) Elimination of most open burning. Control public access. Construct run-on and run-off controls for water. Meet water quality discharge requirements (NPDES) to surface water. Prohibit all liquid wastes except small quantities of household liquid wastes. Maintain records indicating compliance.

25. Design Requirements Synthetic membrane liner at least 30 mils thick Soil liner at least 2 ft. thick Hydraulic conductivity no more than 10 -7 cm/s Other state-approved designs possible

26. Landfilling: Area Method From Sincero & Sincero, 1996

27. Trench Method From Sincero & Sincero, 1996

28. From Davis & Cornwell, 1991

29. Operation of Landfills The landfill operation is actually a biological method of waste treatment. Municipal refuse deposited as a f ill is anything but inert. The liquid produced during decomposition, as well as water that seeps through the groundcover and works its way out of the refuse, is known as leachate. The amount of leachate produced by a landfill is difficult to predict. The only available method is water balance: the water entering a landfill must equal the water flowing out of the landfill, or leachate

30. The total water entering the top soil layer is C = P(1-R)-S-E where C = total percolation into the top soil layer (mm), P = precipitation (mm), R = runoff coefficient, S = storage (mm), and E = evapotranspiration (mm).

31. Gas is a second by-product of a landfill. Since landfills are anaerobic biological reactors, they produce (2% and C02). The rate of gas production from sanitary landfills may be controlled by varying the particle size of the refuse by shredding before placing the refuse in the landfill, and by changing the moisture content. Gas production may be minimized with the combination of low moisture, large particle size, and high density.

32. Unwanted gas migration may be prevented by installing escape vents in the landfill. These vents, called “ tiki torches,” are kept lit and the gas is burned off as it is formed. Improper venting may lead to dangerous accumulation of methane. Since landfills produce considerable quantities of methane, landfill gas can be burned to produce electric power.

33. Closure and Ultimate Use of Landfills Municipal landfills must be closed according to state and federal regulations. Such closure includes the permanent control of leachate as well as gas, and the placement of an impermeable cap. The cost of closure is very high and must be incorporated in the tipping fee during the life of the landfill.

34. Does MSW Degrade in a Landfill?

35. The advantages of landfilling as a waste disposal option include: It costs less than other disposal options A wide variety of wastes are suitable for landfill It frequently offers the only final disposal route for residues arising from end-of-pipe treatment technologies and other waste management options, such as incineration Landfill gas can be collected and utilized for heat and as a low-polluting fuel for energy generation Restored land can provide valuable space for wildlife habitat or leisure use

36. The disadvantages of landfilling include: Older sites, constructed before the impacts of leachate and landfill gas were realized, are now sources of pollution with uncontrolled leakages There is continued risk of contamination from operational landfill sites Some parts of the world are experiencing shortages of suitable landfill sites close to the source of waste generation Landfilling achieves a lower conversion of wastes into energy than other solid waste management strategies The convenience of landfilling tends to discourage the development of innovative waste management strategies Landfilling may produce contaminated land that is unsuitable for some future uses Landfilling causes noise pollution, odors, unsightliness, and often heavy vehicle movement adding to air pollution problems

37. Example : Determine the area required for a new landfill site with a projected life of 20 years for a population of 150,000 generating 25 kg per household per week. Assume the density of waste is 500 kg/m 3 . A planning restriction limits the height of the landfill to 10 m . Assume 3 persons per household. Solution: DATA Population= 150000. Projected life= 20yrs, Waste generated per household= 25kg Waste density= 500kg/m 3 , Height=10m, 3 persons per household.   Waste generated by total household = 150000 * 25 =1250 tonnes/week 3 10 3 = 65000 tonnes/year Volume of landfill space required = (65000*10 3 )/500=130*10 3 m 3 /year If the height is 10m Required land area = 130*10 3 /10 =13000m 2 =1.3ha This value will need to increase by 1.5 to allow for daily cover, roads, receiving areas, fencing etc. Therefore, required area for 20 years ≡ 1.3*20*1.5= 39ha . Note: 1.3 is the required land area, 20 is the life of the landfill 1.5 is the increase.

38. Incineration

39. Characteristics of wastes suitable for incineration: Content of combustible matter above 60% Content of non-combustible solids below 5% Content of non-combustible fines below 20% Moisture content below 30%

40. Waste types not to be incinerated: Pressurized gas containers Large amount of reactive chemical waste Silver salt and photographic or radiographic wastes Halogenated plastics such as polyvinyl chloride (PVC) Waste with high mercury or cadmium content, such as broken thermometers, used batteries, and leadlined wooden panels Sealed ampoules or ampoules containing heavy metals ⇒ Air pollution is undesirable characteristics of incinerator ⇒ Expensive and skill personnel is needed ⇒ May be located close to centre of waste production (advantageous)

41. Hazardous Materials A hazardous material is a substance (gas, liquid, or solid) capable of causing harm to people, property, and the environment. The United States Department of Transportation (DOT) uses the term hazardous materials to cover nine categories identified by the United Nations Hazard Class Number System, including:

42. • Explosives • Gases (compressed, liquefied, and dissolved) • Flammable Liquids • Flammable Solids • Oxidizers • Poisonous Materials • Radioactive Materials • Corrosive Materials • Miscellaneous Materials

43. Assessing the health impacts of waste management we need to bear in mind two groups of people: • the workers involved in the process • the wider public. Health studies Health studies can consist of epidemiological surveys where medical statistics are used to search for any effects. For example, a study could compare the incidence of birth defects among babies whose mothers lived within 5 km of a landfill site (the exposed group) with a similar group (the control group) who were not close to a landfill.

44. Health impacts of incineration Respiratory health – some evidence was found to link incinerator emissions and respiratory health problems. Birth impacts and congenital malformations – the review identified a large number of studies of birth outcomes of mothers living close to incinerators.

45. Moisture Content Determination The moisture content of solid waste is moisture content = mass of moisture /total mass of waste. The moisture content of MSW may vary between 15 and 30%, and is usually about 20%. Moisture is measured by drying a sample at 77°C (170°F) for 24 h, weighing, and calculating as M = w – d x 100, W where M = moisture content, percent, w = initial, wet weight of sample, and d = final, dry weight of sample.