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Materials Mass Balance Analysis: dM/dt = ∑M in - ∑M Out + r w

WASTE GENERATION RATES. Materials Mass Balance Analysis: dM/dt = ∑M in - ∑M Out + r w. Rate of generation of waste material within the system boundary. Rate of accumulation of material within the system boundary. Rate of flow of material into the system boundary.

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Materials Mass Balance Analysis: dM/dt = ∑M in - ∑M Out + r w

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  1. WASTE GENERATION RATES Materials Mass Balance Analysis: dM/dt = ∑Min - ∑MOut + rw Rate of generation of waste material within the system boundary Rate of accumulation of material within the system boundary Rate of flow of material into the system boundary Rate of material out of the system boundary = - +

  2. OutFlow (combustion gases and ashes) Outflow (materials) Inflow Stored materials (raw materials, products solid waste) Outflow (Products) Out flow (Solid wastes, solids in wastewater) System boundary WASTE GENERATION RATES Material Mass Balance Analysis

  3. WASTE GENERATION RATES Question A cannery receives on a given day 12 tons of raw produce, 5 ton of cans, 0.5 tons of cartons and 0.3 tons of miscellaneous materials. Of the 12 tons of raw produce,10ton become products,1.2 tons end up as product waste, which is fed to cattle, and the remainder is discharged with the wastewater from plant. Four tons of the cans are stored internally for future use, and the remainder is used to package the product. About 3 percent

  4. WASTE GENERATION RATES Cont Question of the cans used are damaged. Stored separately, the damaged cans are recycled. The cartons are used for packaging the canned product, expect for 5 percent that are damaged and subsequently separated for recycling . Of the miscellaneous materials, 25 percent is stored internally for future use; 50 percent becomes waste paper, of which 35 percent is separated for recycling with the remainder being discharged as mixed waste; and 25 percent becomes a mixture of solid waste materials.

  5. WASTE GENERATION RATES Cont Question Assume the materials separated for recycling and disposal are collected daily. Prepare a material balance for the cannery on this day and a material flow diagram accounting for all of the materials. Also determine the amount of waste per ton of product.

  6. WASTE GENERATION RATES Solutions 1. On the given day, the cannery receives the following:- 12 tons of raw produce 5 tons of cans 0.5 tons of cartons 0.3 tons of miscellaneous materials.

  7. Solutions Cont 2. As a result of internal activity a) 10 tons of products is produced, 1.2 tons of produce waste is generated, and the remainder of products is discharged with the waste water b) 4 tons of cans are stored and the remainder is used, of which 3 percent are damaged c) 0.5 tons of cartons are used of which 3 % are damaged d) 25% of miscellaneous material is stored; 50% become paper waste, of which 35 percent is separated and recycled, with the remainder disposed of as mixed solid waste; the remaining 25 percent of the miscellaneous materials are disposed of as mixed waste. WASTE GENERATION RATES

  8. WASTE GENERATION RATES 3. Determine the required quantities a) Waste generated from raw produce i) Solid waste fed to cattle = 1.2 ton (1089kg) ii) Waste produce discharge with wastewater=(12-10-1.2)tons=0.8 T(726kg) b) Cans i) Damaged and recycled = (0.03)(5-4) ton = 0.03 ton(27kg) ii) Used for production of product = (1-0.03)ton -0.97ton(880kg) c) Miscellaneous materials i) Amount stored =(0.25)(0.3 ton) = 0.075 ton (68 kg) ii) Paper separated and recycled = (0.50)(0.35)(0.3 ton) = 0.053ton (48kg) iii) Mixed waste =[(0.3-0.075)-0.053] ton = 0.172 ton ( 156kg)

  9. WASTE GENERATION RATES Solutions Cont 3. Determine the required quantities e) Total Weight of product = (10 + 0.97 + 0.485) ton = 11.455ton (10,392 kg) f) Total Material stored = ( 4 + 0.0075) ton = 4.075 ton ( 3696 kg) 4. Prepare a material balance and flow diagram for the cannery for the day a) Amount of material stored= inflow-outflow –waste generation

  10. WASTE GENERATION RATES Solutions Cont 4. b) The material balance quantities i) Material stored = (4.0 +0.075)ton = 4.075 ii) Material Input = (12.0 +5.0 +0.5 +0.3)ton =17.8 iii) Material Output =(10.0 + 0.97+0.485+1.2+0.03+0.015+0.053) =12.753ton iv) Waste Generation=(0.8 + 0.172)ton v) The final material balance is 4.075 = 17.8 – 12.753 -0.972 (verified)

  11. Solutions Cont c) Material balance flow diagram 11.455T Product 12T raw Produce 1.2T Waste Fed to Cattle 5T Cans 0.03T Can Recycled 4.075T Stored Internally 0.5T Cartons 0.015T Carton Recycled 0.3Miscellaneous 0.053T paper Recycled 0.8 T waste produce discharge with wastewater 0.172T mixed waste WASTE GENERATION RATES

  12. WASTE GENERATION RATES Material Mass Balance Analysis • 5. Determine the amount of waste per ton of product: • a) Recyclable material = (1.2 +0.03 + 0.015 + 0.053)ton/11.4.55ton= • = 0.11tonrecycle material/ton product • b) Mixed waste = (0.8 + 0.172)ton/11.455 ton • = 0.085ton mixed waste/ton product

  13. Solid Waste Collection and Transport

  14. On-site Handling, On-site Storage : Curb Collection,Direct haul, transfer station • Collection services: types and methods • Vehicle and labor requirements • Types of Collection systems (hauled container system, stationary container system)

  15. ON-SITE HANDLING: - Activities associated with the handling of SW until they are placed in the containers used for storage before collection ON-SITE STORAGE: Factors considered: • Types of containers used • Container Locations • Public health • Aesthetics • Methods of Collection

  16. Factors considered: i) Types of Containers: • Depend on: • characteristics of SW collected • E.g. Large storage containers (Domestic SW: flats/apartment) • Containers at curbs • Large containers on a roller (Commercial/Industrial) • Collection frequency • Space available for the placement of containers - Residential; refuse bags (7 -10 litres) - Rubbish bins - 20 -30 litres - Large mechanical containers - more commonly used to cut costs (reduce labor, time , & collection costs) - must be standardized to suit collection equipment.

  17. ii) Container Locations: - side/rear of house - alleys - special enclosures (apartment/condos) • Basement (apts. in foreign countries)/ newer complexes iii) Public Health: • relates to on-time collection to avoid the spread of diseases by vectors, etc. iv) Aesthetics: - must be pleasing to the eye (containers must be clean, shielded from public’s view).

  18. v) Collection of SW - 60-80 percent of total SWM costs. - labor and capital intensive. - Major problems: • Poor building layouts - e.g. squatters • Road congestion - time cost, leachate, transport costs. • Physical infrastructure • Old containers used (leaky/ damaged) • Absence of systematic methods (especially at apartments, markets with large wst. volume).

  19. Collection of SW(cont.) • Collections were made by: • Municipal/ District Council • Private firm under contract to municipal • Private firm contract with private residents

  20. TYPES OF COLLECTION: • Municipal Collection Services: a. Residential: • Curb (Kerb-side), alley, and backyard collection (100-120 litres) • Quickest/ economical • Crew: 1 driver + 1 or 2 collectors • No need to enter property • Most common

  21. TYPES OF COLLECTION (Cont.) ii. Set-out, set back: - Collectors have to enter property - Set out crew carries full containers from resident storage location to curb/ alley before collection vehicle arrives. - Collection crew load their refuse into vehicle • Set-back crew return the container to storage area. • House-to-house collection where refuse bags used in 20-30 liter bins.

  22. High-rise apartment or flats, specially designed chutes or a communal storage or roll-on-roll-offs (RORO’s). • Future trend: mechanically-equipped trucks. b) Commercial-Industrial Collection Services ( > 12 m3 ) i. Large movable and stationary containers ii. Large stationary compactors (to form bales)

  23. Collection Frequency: - residential areas : everyday/ once in 2 days - commercial : daily - food waste - max. period should not exceed : • the normal time for the accumulation of waste to fill a container • the time for fresh garbage to putrefy and emit fouls odor • the length of fly-breeding cycle ( < 7 days).

  24. Factors Affecting SW Collection Productivity: a. Service Level Related: • collection point, frequency, waste material b. Route related: • Containers, Distance, constraints, topography, delays, road conditions c. Collection Methodology Related/Climate Related: • Crew size, collection procedures, wind, rain.

  25. Waste Collection Models Determination of Vehicle and Labor Requirements.

  26. LAY-OUT OF ROUTES: 4-Step Process 1. Prepare location maps: - with pick-up point locations - number of containers - collection frequency - estimated quantities (in the case of SCS with self-loading compactors).

  27. 2. Data summaries: - Estimate of waste each day (from pick-up locations) - ( for SCS - number of locations for each pick-up cycle). 3. Lay preliminary collection routes (from different stations). - Route should connect all pick-up locations + last location be nearest to disposal site). 4. Develop balanced route - determine haul distance for each route - Determine labor requirements per day, check against available work times per day - draw master map.

  28. Selecting Collection Equipment: - Changing needs and advances in technology - Trends - increase use of computer-aided equipment and electronic control (e.g. on-board computers for monitoring truck performance and collection performance). - Most prevalent: compactor trucks (equipped with hydraulically powered rams that can compact wastes to increase payload). - Open and close non-compacting trucks: o Inexpensive to purchase or maintain o Inefficient for most collection application (small amt. of waste, have to lift high to dump into the truck) o Suitable for yard, bulky wastes, and recyclable materials, for small communities and rural areas.

  29. Factors to consider in selection of vehicle: • Waste quantities • Truck body or container capacity • Regulations regarding truck size and weight, • To maximize the amount of wastes that can be collected while remaining within legal weights for the overall vehicle. • Consult with collection crew and drivers. • Loading location/ Location of container - determine the type of vehicles to be used: Front-loading; Side-loading or rear-loading compactor truck. • Physical characteristics of the collection routes/ road width - e.g. wide street - use side-loading automatic collection system; for narrow urban streets - use rear loaders.

  30. Factors to consider in selection of vehicle(Cont.): • Residential, commercial or industrial: HCS for large buildings (e.g. apt., industries,etc.) • Safety and comfort - to minimize danger to crews. • Truck turning radius - be as short as possible. • Water tightness - to prevent leakages. • Speed - wide range of speed.

  31. TRANSFER OF MUNICIPAL WASTE - More common as the distance of landfill sites becomes greater - Most common in larger metropolitan areas. - Variance in types, size, and degree of sophistication - E.g. open-air stations or enclosed in a building (newer stations).

  32. Advantages of Transfer stations: - better haul roads for collection vehicles (usually paved - reducing damages to trucks and delay). - greater traffic control (avoid traffic jams/congestion or litter + safety to children). - fewer truck on the sanitary landfill haul routes( reduction ratio of from 3 (trucks) :1 (transfer haul) or 5:1). - improved landfill operating efficiency (fewer trucks mean better traffic control). - Lower overall haul cost (reduction in no. of drivers/crew).

  33. Criteria for Transfer Location: - Near the collection area served (to minimize collection crew time for haul to the transfer station). - Accessible to major haul routes (public acceptance and economics - lower transfer haul cost)). • Adequate land area to provide isolation (to handle traffic flow). • Suitable Zoning (commercial or industrial) - Served by utilities (water, sanitary sewer, storm drainage, electricity)

  34. Station Concepts • Pit • Direct Dump • Compaction • Pit: • Collection vehicles unloaded wastes into a large pit. • Wastes are then pushed to an open-top transfer trailer by a tractor. • The pit - as storage during peak periods. • Compaction of bulk items made by the tractor in the pit.

  35. Direct Dump: • collection vehicles dump directly into open-top transfer trailer • Large hoppers direct the waste into the transfer trailers. • Very large transfer trailers are used (due to minimal compaction). • Efficient - no intermediate handling required (direct from vehicle to transfer trailer).

  36. 3. Compaction: i) Hopper type compaction station : waste drop by gravity into a compactor - packs the waste into the trailers. ii) Push pit compactor station: a large hydraulically operated blade moves the waste to the stationary packer - then packs the waste into the trailers.

  37. Advantages & Disadvantages of Design Alternatives:

  38. PROCESS OPTIONS AT TRANSFER STATIONS: - To prepare waste for transfer haul and subsequent disposal 1. Baling: • - practiced in the US since 1960’s • - reduces haul cost • - a more controlled operation at the landfill • - require lower cover material • - density 1500-2000 lb/yd3 • - may have wire ties or may not be tied. - Requires little or no separation of wastes.

  39. 2. Shredding: - Shredders are used. - Handles bulky wastes (furniture, tree limbs, etc.) - Transport - use enclosed transfer trailers. - Wastes have good compaction characteristics - requires small trailers.

  40. HAZARDOUS WASTE

  41. DEFINITION • Hazardous waste means wastes (solids, sludges, liquids and container gases) other than radioactive (and infectious) wastes, by reason of their chemical activity of toxic, explosive, corrosive or other characteristics cause danger or likely will cause danger to health or the environment, whether alone or when coming into contact with other waste - United Nations Environment Programme (UNEP) (1985)

  42. Hazardous waste is any waste or combination of wastes which pose a substantial present or potential hazard to human health or living organisms because such wastes are lethal, non-degradable, persistent in nature, biologically magnified or otherwise cause or tent to cause detrimental cumulative effects. - United States Environmental Protection Agency (USEPA) • Toxic and hazardous wastes are wastes or combination of wastes that pose a significant present or potential hazard to human health or living organisms, and are included in ‘Scheduled Wastes’ - Department of Environment (DOE), (1995) • There are 107 categories of ‘Scheduled Wastes’ and these include wastes generated mainly from petroleum and oil refineries, pharmaceutical, rubber processing, chemical and electronics and semiconductor industries

  43. Classification of hazardous waste • Two basic approaches • Listing approach • Criteria approach • Listing approach • Listing by source • Candidate waste streams are reviewed by source and segregated into hazardous and non-hazardous categories

  44. Advantages • Ease of implementation and enforcement • Once wastes have been designated, the wastes can be readily categorised by source. • Generators and regulators can quickly determine the status of waste without performing any test • Cost associated with identification of hazardous waste is low • Disadvantages • Ignores the reality that waste from two generically similar sources may have greatly different properties • Does not accommodate new wastes or combination of wastes • Periodic evaluation of wastes to reaffirm or change designation is necessary

  45. Listing by pure compound • Selected list of hazardous compound is developed • Wastes that contain any of these compounds are designated hazardous • Advantages • Data on most of the selected compounds are readily available in the literature • Literature data is used and waste analysis is reduced to chemical characterization • Costly hazard testing is eliminated • Disadvantages • Its assigns properties of single constituent to a complex waste mixture, thus fails to account for interactions between various constituents – alter the hazardous nature • Mixture of non-hazardous compounds may react to produce a hazardous product in a waste

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