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SWM L15-L28_drhasan (Part 2).pdf

This content covers the necessary theories and related mathematical problems of Solid Waste Management Course which basically is prepared for the undergraduate students of BSc in Civil Engineering program.

1 of 93
Solid and Hazardous Waste
Management
Lecture prepared by
‘Dr. Hasanliketo beliefthat solidwasteisa valuableraw
materialslocatedat a wrongplace’
Md. Mahmudul HASAN, Engr., PhD
Associate Professor and Head
Dept. of Civil Engg.
BAUST, Saidpur
(Former: Assistant Prof., Dept. of Civil Engg., UAP
Head & Assistant Prof., Dept. of Civil Engg., UITS)
Chapter 05:
Recycling and Reuse
2
Dr. Engr. Md. Mahmudul HASAN
Dr. Engr. Md. Mahmudul HASAN
Recycling and Reuse
Recycling and reuse involve recovery of resources from the waste stream in the form of
both materials and energy. Recycling can be practised at household level and at material
recovery facilities (MRF) or full stream processing plants.
Depending on the reuse of recycled materials this process may be broadly categorised
into:
primary recycling:
This is the part of a material recovery system where recycled materials are reused in
their same form; for example, paper for packaging in retailers’ shops; textiles for
machinery wiping; textiles, shoes, etc. for reuse by the poor; demolition waste for land
reclamation; beverage bottles for refilling; containers such as bottles for use as domestic
containers. This is the most efficient form of recycling and involves a few processes;
sometimes only cleaning.
secondary recycling:
This includes both materials and energy recovery where recycled materials are used for
re-manufacturing or to produce energy. For example, paper for repulping; textiles for
paper making; metals and glass for remoulding; rubber for low-grade rubber
production; plastic for inferior grade production; waste recovered as feedstock for
biological processes; refuse-derived fuel; etc. These processes are more energy
intensive than primary recycling. 3
Dr. Engr. Md. Mahmudul HASAN
Recycling and Reuse: Environmental Justification
There are numerous environmental justifications for recycling and reuse:
i. It minimises the use of virgin raw materials directly (when recycled materials are
used as raw materials) or indirectly (reuse minimises the demand for new
products).
ii. It saves energy both directly (when recycled materials are used as feed to produce
energy) and indirectly (saves energy required to manufacture products or for their
disposal).
iii. It reduces the amount of waste that must be disposed of, which reduces the energy
required for transportation and disposal and minimises overall environmental
pollution.
iv. It limits emissions of greenhouse gases such as methane through the removal of
organic waste from open dumping (the most common method in most low- and
middle-income countries) and at landfill disposal sites.
v. It generates income through recycling (often informal in low-income countries),
trade which improves the quality of life of a section of the poor.
vi. It reduces overall waste management costs.
4
Dr. Engr. Md. Mahmudul HASAN
Recycling and Reuse: Risks
There are numerous environmental justifications but having some risks:
i. It involves health hazards to the people working in this sector, particularly when
recycling hazardous materials and sharps.
ii. The production costs of reusable products may be high. For example, reusable
containers should be more durable and therefore may consume more materials
and energy compared to a product for one use. It may also involve energy to
clean and sterilise them to safeguard public health.
iii. The collection of recycled materials may involve additional collection vehicles
which may increase the volume of traffic.
iv. In some cases more energy may be required in the recycling processes
themselves than would be used in the manufacture of new materials.
v. It is apparent from Virtanen and Nilsson (1993) that the maximum level of
paper recycling in Austria leads to greater emissions of sulphur dioxide, nitrous
oxide and carbon dioxide in comparison with the component of energy
recovery by incineration allowing a reduction in the overall use of fossil fuels
5
Dr. Engr. Md. Mahmudul HASAN
Recycling and Reuse: Bangladesh Pattern in Urban area
Figure: Recycling
pattern for urban solid
waste in Bangladesh
6

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SWM L15-L28_drhasan (Part 2).pdf

  • 1. Solid and Hazardous Waste Management Lecture prepared by ‘Dr. Hasanliketo beliefthat solidwasteisa valuableraw materialslocatedat a wrongplace’ Md. Mahmudul HASAN, Engr., PhD Associate Professor and Head Dept. of Civil Engg. BAUST, Saidpur (Former: Assistant Prof., Dept. of Civil Engg., UAP Head & Assistant Prof., Dept. of Civil Engg., UITS)
  • 2. Chapter 05: Recycling and Reuse 2 Dr. Engr. Md. Mahmudul HASAN
  • 3. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse Recycling and reuse involve recovery of resources from the waste stream in the form of both materials and energy. Recycling can be practised at household level and at material recovery facilities (MRF) or full stream processing plants. Depending on the reuse of recycled materials this process may be broadly categorised into: primary recycling: This is the part of a material recovery system where recycled materials are reused in their same form; for example, paper for packaging in retailers’ shops; textiles for machinery wiping; textiles, shoes, etc. for reuse by the poor; demolition waste for land reclamation; beverage bottles for refilling; containers such as bottles for use as domestic containers. This is the most efficient form of recycling and involves a few processes; sometimes only cleaning. secondary recycling: This includes both materials and energy recovery where recycled materials are used for re-manufacturing or to produce energy. For example, paper for repulping; textiles for paper making; metals and glass for remoulding; rubber for low-grade rubber production; plastic for inferior grade production; waste recovered as feedstock for biological processes; refuse-derived fuel; etc. These processes are more energy intensive than primary recycling. 3
  • 4. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Environmental Justification There are numerous environmental justifications for recycling and reuse: i. It minimises the use of virgin raw materials directly (when recycled materials are used as raw materials) or indirectly (reuse minimises the demand for new products). ii. It saves energy both directly (when recycled materials are used as feed to produce energy) and indirectly (saves energy required to manufacture products or for their disposal). iii. It reduces the amount of waste that must be disposed of, which reduces the energy required for transportation and disposal and minimises overall environmental pollution. iv. It limits emissions of greenhouse gases such as methane through the removal of organic waste from open dumping (the most common method in most low- and middle-income countries) and at landfill disposal sites. v. It generates income through recycling (often informal in low-income countries), trade which improves the quality of life of a section of the poor. vi. It reduces overall waste management costs. 4
  • 5. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Risks There are numerous environmental justifications but having some risks: i. It involves health hazards to the people working in this sector, particularly when recycling hazardous materials and sharps. ii. The production costs of reusable products may be high. For example, reusable containers should be more durable and therefore may consume more materials and energy compared to a product for one use. It may also involve energy to clean and sterilise them to safeguard public health. iii. The collection of recycled materials may involve additional collection vehicles which may increase the volume of traffic. iv. In some cases more energy may be required in the recycling processes themselves than would be used in the manufacture of new materials. v. It is apparent from Virtanen and Nilsson (1993) that the maximum level of paper recycling in Austria leads to greater emissions of sulphur dioxide, nitrous oxide and carbon dioxide in comparison with the component of energy recovery by incineration allowing a reduction in the overall use of fossil fuels 5
  • 6. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Bangladesh Pattern in Urban area Figure: Recycling pattern for urban solid waste in Bangladesh 6
  • 7. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Effectiveness factors The development of an effective recycling programme and selection of materials that can be recycled should be based on the following: i. Legislation may demand diversion of certain materials from waste streams (for example, present legislation in many industrialised country bans disposal of certain materials on the landfill, and the final disposal option may involve a higher tipping fee for selected materials). ii. Recycling opportunities provide a market for recycling materials; however, to design centralised recycling plants, particularly in developing countries, if a small percentage of targeted materials are available in the waste stream because of their very high market value (so that they are recycled at household level), then a centralised recycling system may not be cost effective. iii. Commitment of organisations involved in solid waste management and protection of environment is essential – depending on the level of commitment, there may be subsidies, loans, incentives, etc. for recycling selected materials. iv. Labour and equipment infrastructures must be available. v. Finance is required for the programme – including the cost of planning awareness programmes; capital costs (for recycling plant); programme operation and maintenance costs; and marketing costs (of recycled products). 7
  • 8. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Processes The activities involved in material recycling processes may be broadly categorised into: 1. Separation of materials: Separation (sorting) of materials from the waste stream is the first essential elements in any recycling operation. The possibility of contamination of source separated materials is minimised if they can be separated at household level. Commonly practised separation mechanisms involve: o manual sorting o mechanised sorting o both manual and mechanised sorting. 2. Conversion of materials: Waste materials can be converted into usable materials and energy. The main conversion processes are: o thermal conversion – incineration to recover energy or heat, pyrolysis o biochemical conversion – anaerobic digestion, composting, hydrolysis. 8
  • 9. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Processes manual sorting 9
  • 10. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Mechanised sorting Mechanized material separation techniques: 1. conveyors (pan, belt, bucket or pneumatic) – to pick and/or convey waste in the recycling plant (manual sorting of selected materials from conveyor can also be done), 2. shredding (flair or hammer mills, shear shredders, glass crushers, wood grinders) equipment – used to break various constituents of waste to extract them more easily, 3. screens (rotary drum or disk type) – process of separation by size, but it is generally plugged by a number of things, 4. cyclone/density separators – occasionally used to separate light materials from air stream or prepared waste, 5. magnetic and electromechanical separators – often used for the purification of feed streams containing unwanted magnetic impurities or concentration of magnetic materials, 10
  • 11. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Mechanised sorting Screening: Factors that must be considered in the selection of screening equipment include: 1. specification of materials for the components to be screened 2. characteristics of the waste materials to be screened, including particle size shape, density, etc. 3. screen design characteristics including materials of construction, opening size, surface area of the screen, speed of the rotor, etc. 4. separation efficiency and overall effectiveness 5. site, access, noise and environmental limitations. The efficiency of a screen can be evaluated in terms of the percentage recovery of the material in the feed stream by using the following expression: 11
  • 12. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Mechanised sorting Screening: The efficiency of a screen can be evaluated in terms of the percentage recovery of the material in the feed stream by using the following expression: Hence, the effectiveness of screen can be deduced by the following expression: 12
  • 13. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Determination of screen recovery efficiency and effectiveness Example: Given that 2500kg/h of municipal solid waste with 10% glass is applied to a rotary screen for the removal of glass prior to shredding. Weight of underflow is 500kg/h and weight of glass in screen underflow = 200kg/h, determine the recovery efficiency and effectiveness of the screen. 13
  • 14. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Promotion and planning Following Activities may help with promotion and planning for recycling and reuse: i. Involvement of all stakeholders The recycling programme should aim to involve all waste generators, governments, NGOs, etc. to operate the system efficiently. ii. Public education campaign As their participation is important for well-planned recycling, it is necessary to encourage greater participation of waste generators (for example, separation of materials at source) and to support them by providing information and education. iii. Commitment of local government Local as well as national government has a major responsibility to develop a recycling plan with some targets, and local government should play an advocacy role to motivate and encourage generators. iv. Assessment and augmentation of existing system It is vital to identify the successes, problems and limitations of any existing system so that appropriate measures can be planned, such as modifying or formulating waste management legislation. 14
  • 15. Dr. Engr. Md. Mahmudul HASAN Recycling and Reuse: Promotion and planning v. Building local expertise If a new technological solution is being adopted, operation and maintenance of pilot- scale plants may help develop local expertise and will also minimize planning errors. vi. Possibility of integration with other waste management elements Waste management can be integrated with transfer stations and disposal sites as this has a positive impact on other waste management elements and may help to sustain the programme. vii. Assessment of local waste stream Both quantity and composition of different constituents should be assessed, to identify materials with potential to be recycled. viii. Market specification of recovered materials The market needs to be investigated, to assess the costs associated with meeting the required specification for recovered materials. ix. Recycling opportunities The ultimate success of many recycling plants depends on marketing of recovered materials. It should take into account market uncertainties. 15
  • 16. Chapter 06: Anaerobic Digestion 16 Dr. Engr. Md. Mahmudul HASAN
  • 17. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion The following terms are frequently used as synonyms for anaerobic digestion: o biogasification o biogas generation o fermentation o methane fermentation o methane production. The main advantages of anaerobic digestion are: i. produces renewable energy ii. energy recovery rate is much higher than the energy recovery inform landfill (all gas produced can be collected and utilised, but landfill gas collection efficiency never exceeds 50 per cent and in many situations landfill gas collection efficiency is very low) iii. cured sludge can be used as a soil conditioner iv. produces less saline product than compost v. minimises odour and aesthetic problems compared with composting systems vi. low or no energy consumption in operation vii. occupies very little land viii. reduces volume for final disposal for solid waste and avoids landfill gas generation ix. minimises greenhouse gases x. provides low environmental impact - reducing water, soil and air pollution. 17
  • 18. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Unit operations and steps Figure: Typical unit operations and steps in the anaerobic digestion of solid waste 18
  • 19. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Mechanism The anaerobic digestion of solid waste involves the microbial decomposition of the organic fraction of solid waste, in the absence of molecular oxygen, by a group of micro-organisms, which convert waste organic materials to produce: mostly methane (CH4) and carbon dioxide (CO2) and very small amounts of other gases such as hydrogen sulphide (H2S), ammonia (NH3), depending on the composition of the feed materials. The mechanism of this anaerobic process is very complex and it follows several pathways to decomposition by several groups of anaerobic micro-organisms. This includes the following stages: Stage1: hydrolysis: the polymer breakdown of organics of higher molecular weight into smaller, soluble molecules/monomers, carried out by extracellular enzymes. Proteins, carbohydrates and lipids are transformed to amino acids, sugars and fatty acids (and glycerine) respectively. However lipids are hydrolysed very slowly, particularly at temperatures below 200 C, and therefore hydrolysis might be (including methane production) a rate-limiting step for waste containing a higher percentage of lipids and other slow-hydrolysing compounds, such as piggery waste. 19
  • 20. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Mechanism Stage 2: fermentation (acidogenesis and acetogenesis) soluble monomers are fermented to simple organic compounds, volatile fatty (acetic, butyric, propionic, and also lactic and formic) acids and in some situations, CO2 and/or hydrogen by acid- forming bacteria, depending on the composition of waste materials. Stage 3: methanogenesis methane is produced from methogenic substrates or from the reduction of carbon dioxide by hydrogen using acetotrophic and hydrogenotrophic bacteria respectively. The hydrogen consumption also improves the environment of the conversion processes of butyrate and propionate to acetone. Methanogenic substrates generally include acetate, methanol, formate, methylamines, methyl mercaptants and reduced metals. Micro-organisms may also directly produce methane from carbon monoxide, carbon dioxide and hydrogen. 20
  • 21. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Mechanism Figure: Different stages of anaerobic digestion All the above processes are successive, but in a continuous-feed digester they may take place at any time. The better the different fermentation processes merge, the shorter the digestion period. 21
  • 22. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Overall Reactions The general anaerobic transformation of solid waste can be described by means of the following equation: If it is assumed that the organic wastes are stabilised completely, the corresponding expression is: 22
  • 23. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Reactions at different stages The typical reaction that may take place in 1st stage i.e. hydrolysis process is: The typical reactions that may take place in the 2nd stage i.e. fermentation process caused by acid-forming bacteria are: 23
  • 24. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Reactions at different stages The typical reactions that may take place in the 3rd stage i.e. methanogenesis phase are: 24
  • 25. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Gas estimation Problem: Estimate the total theoretical amount of gas that could be produced under anaerobic conditions in a sanitary landfill per unit weight of solid waste. Given that the chemical formulas of the typical waste are as follows: Without water: C60.0 H94.3 O37.8 N With water : C60.0 H156.3 O69.1 N Given that the total weight of organic material in 1001b of solid wastes is equal to 58.5 lb including moisture. Solution: 1. Determine the total amount of dry decomposable organic waste, assuming that 5% of the decomposable material will remain as an ash: Decomposable organic wastes (dry basis), lb = 58.5 * 0.95 = 56.0 lb 2. Using the chemical formula C60.0H94.3O37.8N estimate the amount of methane and carbon dioxide that can be produced, using Equation 25
  • 26. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Gas estimation Problem: For the given chemical formula, here, a = 60.0 b = 94.3 c = 37.8 d = 1 26
  • 27. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Gas estimation 27
  • 28. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Gas estimation 6. Determine the total theoretical amount of gas generated per unit weight of solid waste: 28
  • 29. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Factors affect The important factors affecting anaerobic digestion are: pH: The anaerobic digestion process requires an environment with a neutral pH, where methanogenesis progresses at a relatively higher rate. The desirable pH range is from 6.5 to 8, but microbial activity may take place between pH 5 and pH 9. Beyond this pH limit the rate of methanogenesis decreases. The stability of pH is also important. Environmental factors: o pH o alkalinity o temperature o Toxicity Other factors: o Loading rate o Retention time o Nutrients o Solid content o Pre-treatment o Mixing 29
  • 30. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Factors affect Alkalinity: Alkalinity indicates the capability of fermentative fluid in neutralising excess acidic or basic substance. It is evident that biogas fermentation can occur in fermentative fluid if the alkalinity range is between 1,000 to 10,000 mg/l (when expressed as CaCO3). Temperature: In anaerobic digestion, there exists a direct relationship between the extent and intensity of microbial activity and temperature. Biogas production efficiency increases with increasing temperature. According to the temperature of the digester content, the following types of digestion are distinguished: o psychrophilic digestion (0 C– 20 C) o mesophilic digestion (20 C– 40 C) o thermophilic digestion (40 C–70 C). The retention time for psychrophilic, mesophilic and thermophilic digestion may be more than 100 days, 20 days and 8 days respectively. Many micro-organisms, especially methaneproducing bacteria, are sensitive to sudden changes of temperature. The generation of biogas will be slowed down noticeably if there is an abrupt change of temperature of 5 C or more. Toxins: Many compounds such as heavy metals, antibiotics, disinfectants, detergents, pesticides, chlorinated hydrocarbons and other organic solvents at inhibitory concentrations affect the rate of anaerobic digestion. Therefore, care must be taken so that the feed materials or the water used are not polluted by such materials. 30
  • 31. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Factors affect Loading rate : The loading rate is generally expressed as weight of organic matter [volatile solids (VS) or chemical oxygen demand (COD)] per unit of digester capacity per unit of time. The loading rate is significantly influenced by the nature of the waste. It is apparent from different investigations that the lower loading rate is more desirable for easily biodegradable feed materials (like animal manure, sewage, meat, green leaves), as these foods are readily available for bacterial consumption, Higher loading rates can be applied to refractory organic materials (like paper and dry organic materials). The loading rates can range from 1 to 5 kg/m3/d depending on the type of feed materials, the size of digester and the climatic conditions. Retention time : The term retention time or residence time indicate the length of time spent by the feed materials in an anaerobic digester. The retention time depends on digestion temperature and, in some situations, on the nature of feed materials. Nutrients: Nitrogen, phosphorus and potassium are required for anaerobic digestion. An appropriate carbon-nitrogen ratio (C/N) is essential in the nutrient balance of most of the micro-organisms. A high C/N ratio favours acid formation and thus may slow down digestion, particularly the methanogenesis process. Similarly, the presence of insufficient carbon to convert nutrients into protoplasm, eliminates excess nitrogen, often as ammonia. Therefore, proper attention has to be paid in selecting feed materials to minimise these effects, and it is very important to mix the raw materials in accordance with the C/N ratio to ensure better performance of anaerobic digestion. 31
  • 32. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Factors affect Solid content: Generally 6-12% of solid concentration of the feed material is considered to be optimal for the production of biogas. This also depends on the fermentation temperature and the type of materials used. Pre-treatment: Pre-treatment may include separation of contaminants, size reduction of feed materials and partial decomposition of refractory materials. Separation of contaminants (non-biodegradable waste or recyclables) from the organic fraction of solid waste improves the efficiency of biological processes and enhances the quality of the digested residue – generally used as compost. Reduction of particle size increases the exposed surface areas for bacterial action and thus enhances the digestion process. Mixing: Mixing enhances the efficiency of the anaerobic digestion processes. Mixing also minimises the problems associated with the formation of scum. This can be carried out by mechanical stirring devices or through digester design modification, by liquid and/or gas recycling, or by a combination of both mechanical and re-circulation arrangements together. 32
  • 33. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Types of digester Different anaerobic treatment processes and a wide variety of digester models (including a few large-scale installations) are currently available to carry out anaerobic digestion: i. batch- and dry-fermentation or batch digester: It is simple and requires no control if the start-up is successful. But the main disadvantage of this system is that biogas production varies with time, limiting its usage ii. fixed dome (Chinese model): This is the most common digester type in developing countries, and the basic design originated in China. The reactor consists of a gastight chamber constructed from bricks, stone, or poured concrete. Both the top and bottom of the reactor are hemispherical, and are joined together by straight sides. iii. floating cover (Indian or KVIC design): most popular in India. It is also used extensively throughout the world, being the most common type of digester used for treating sewage sludge in many industrialised countries. iv. flexible bag: The bag digester is essentially a long cylinder (generally with length /diameter ratios ranging from 3 to 14) made of either PVC, a Neoprene-coated fabric (Nylon), or red mud plastic v. septic tank: A number of purpose-made anaerobic reactors are currently used in the USA, Europe, Japan and some other countries, mostly to digest sewage. vi. plug flow: A typical plug-flow reactor consists of a trench cut into the ground and lined with either concrete or an impermeable membrane (Figure 6.7). To ensure true plug-flow conditions, the length has to be considerably greater than the width and depth. vii. anaerobic baffler reactor: The reactor is a simple rectangular tank, with physical dimensions similar to a septic tank, and is divided into 5 or 6 equal volume compartments by means of walls from the roof and the bottom of the tank. The liquid flow is alternative upwards and downwards between the walls viii. anaerobic filter: Both upflow and downflow anaerobic filters are used on a limited scale, mainly to treat industrial wastewater, and the system is very costly. ix. large-scale installation. 33
  • 34. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Batch digester 34
  • 35. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Batch digester 35
  • 36. Dr. Engr. Md. Mahmudul HASAN Anaerobic Digestion: Economic and Environmental aspects Economic aspects: The cost of waste treatment largely depends on local conditions such as the cost of labour, the availability and cost of materials, land prices, taxes and subsidies and so on. It is apparent that the investment costs for anaerobic digestion appear to be a factor of 1.2-1.5 higher than for composting. The capital costs of a modern anaerobic digestion plant are lower than those for energy from waste plants, but similar to those of MRF. Environmental aspects: During the digestion process, a significant reduction of BOD occurs. It is evident that about 70 per cent of BOD removal occurs within five days of the retention period. Thus, the digestion process improves the quality of digester effluent and minimises environmental damage, particularly ground water pollution. 36
  • 38. Dr. Engr. Md. Mahmudul HASAN “Composting (also called ordinary composting) is the biological decomposition of the biodegradable organic fraction of MSW under controlled conditions to a state of sufficiently stable for nuisance-free storage and handling and for safe use in land applications.” The specification “biological decomposition” confines composting to the treatment and disposal of the biologically originated organic fraction of MSW. The term “controlled conditions” “differentiates the composting process from the simple organic waste decomposition that happens in open dumps and landfills (in composting, it is a way of harnessing the natural processes of decomposition to speed up the decay of waste). The specification, “sufficiently stable,” is a prerequisite for nuisance-free storage and handling and for safe use in land applications. During the composting process, heat, various gases and water vapors are released, greatly reducing the volume and mass of the pile. Decomposition of solid waste may be accomplished aerobically or anaerobically. Anaerobic process however involves offensive odors and is extremely slow. Most composting operations are therefore aerobic. Composting provides a means of accomplishing all three of the Rs: the amount of rubbish sent to the landfill is reduced, organic matter is reused rather than being damped, and it is recycled into a useful soil amendment. The composting process is explained in the Fig 1. Composting: Explanation 38
  • 39. Dr. Engr. Md. Mahmudul HASAN Figure: Organic solid waste Figure 01: Composting process Composting: Process 39
  • 40. Dr. Engr. Md. Mahmudul HASAN Composting: Compost or Humas Figure 3: Compost or Humas: End product of the composting The end product remaining after bacterial activity is called “humus” or “compost” (as shown in the Fig. 3). The Characteristics of the compost are given in the following table: 40
  • 41. Dr. Engr. Md. Mahmudul HASAN Figure: process flow diagram for MSW composting facilities Composting: process flow diagram for MSW composting facilities Composting process consists of four basic steps: (1) preparation; (2) digestion, (3) curing, and (4) finishing. Preparation Digestion Curing Finishing 41
  • 42. Dr. Engr. Md. Mahmudul HASAN Composting: process flow diagram for MSW composting facilities Preparation o The non-compostable materials such as plastics, textile, leather, bones, glass, metals etc. are removed from the feed stock. o This will prevent any damage to the machines during the subsequent operations. o Also improves the compost quality. o Sorting, Shredding, Grinding, Screening are the common steps to separate non-compostable materials during preparation. Digestion o Main process of the composting. o In modern composting plants/facilities, digestion takes place within windrows (area method) or in mechanical digesters (High rate digestion method). 42
  • 43. Dr. Engr. Md. Mahmudul HASAN Composting: process flow diagram for MSW composting facilities Curing o In this step, carbon is further converted to carbon dioxide and humus; and nitrogen into nitrates. o the population of the microorganisms decreases and the type of the organisms is changed too. o This lowers the temperature of the compost pile. o Curing is needed to ensure complete stabilization. Finishing o In this step, the compost is passed through a 1 to 1.25cm fine screen to remove oversized and non-compostable materials. o Further improves the quality of the compost. o In developed countries, there are established standards for the compost quality which are met before sending it to the market for sale. Therefore proper quality testing is required. o Also includes the operations of making pellets, granulation, regrinding, rescreening, blending with various additives and adjustment of moisture content and bagging etc. 43
  • 44. Dr. Engr. Md. Mahmudul HASAN Composting: technologies currently used 1. Passive windrow 2. Turned windrow 3. Aerated static pile 4. In-vessel channel 44
  • 45. Dr. Engr. Md. Mahmudul HASAN Composting: essential factors of effective composting 45
  • 46. Dr. Engr. Md. Mahmudul HASAN Composting: essential factors of effective composting Following conditions are essential for effective composting: i. For optimum results, the size of the waste should lie between 2 and 8 cm. ii. The minimum size of the compost heap should be such that it does not dissipate moisture and heat from the pile. The minimum recommended volume is about 3 cubic metres. iii. Sufficient number of microorganisms to be present to perform digestion. Sewage sludge is added for this purpose. iv. The presence of nitrogen, phosphorous, potassium and some other trace elements helps the composting process. Due to the high microbial activity in the composting process, a large supply of nutrients is required by bacteria. The essential range of C/N ratio should be 30 to 50 and C/P ratio should be 100 or less. v. Moisture content should be 50 to 60%. Addition of water is done to raise moisture contents, if required. Excess MC (>65%) generally replaces air from the inter-spaces within the particles that minimizes the level of available oxygen and thus may lead to anaerobic conditions. Again if a certain amount of moisture is absent (<12%), the metabolic activity of the microorganisms may cease. The optimum MC for the composting process depends on the physical characteristics of the materials also. vi. pH should vary between 5.5 to 8.5 throughout the process although organic materials with a wide range of pH values (from 3 to 11) can be composted. vii. Air should be thoroughly dispersed throughout the organic waste. This is done by frequently turning and mixing the wastes. viii. Temperature should be maintained between 50 to 60oC for active composting period i.e. this range ensures more suitable environment for thermophilic micro-organisms and results in a significant reduction in pathogens and parasites. 46
  • 47. Dr. Engr. Md. Mahmudul HASAN Composting: Micro-Organisms and Functions Following function are performed by the composting process: a) Stabilizes the putrescible organic matter. b) Kills pathogens and weed seeds. c) Conserves N, P, K, and resistant organic matter found in the raw material. d) Produces uniform, relatively dry end product free from objectionable and harmful objects. e) Conducts the process in a sanitary manner. If conditions are controlled well then it is free from insects, rodents and odors. Types of Micro-Organisms in composting: The principal classes of microorganisms involved in the aerobic decomposition of solid wastes are; (1) bacteria, (2) fungi , (3) actinomycetes, (4) algae, (5) protozoa and (6) some larva. The general class of microorganisms which play active role in the conversion of solid wastes to either cell mass or some by-product of cell metabolism are called “protists”. Bacteria, fungi, yeasts and actinomycetes are of major concern. Protozoa and algae are also protists but are not of primary importance. 47
  • 48. Dr. Engr. Md. Mahmudul HASAN Composting: Advantages 1. Composting is the only presently operational technology which provides for the recycling of organic residuals. 2. Composting can be used to dispose of many organic industries' wastes which because of their non-fluid nature are not amendable to treatment by activated sludge or trickling filter process. 3. The process is used in many parts of the world to convert human and often animal excrement with plant trimmings and other organic refuse to soil conditioner. 4. Composting plants offer favorable conditions for reclaim of paper, cans, metals, rags and glass. 5. A well located refuse composting plant may reduce the cost of hauling refuse to the points of disposal. 6. Flexibility of operation permits a 100-200% overload design capacity for several days by increasing the time, receiving bins and grinders' operation. 7. Weather does not affect an enclosed system. 8. There is no leachate control problems involved. 9. There are no air pollution control problems as involved in incineration. 10. Composting produces potentially useful end product, which is utilized as soil conditioner, helps soil conservation in sloppy area, replaces the organic content exhausted by the excessive use of lands, improves porosity of soil and thus water retaining property for nourishment of the crops. 11. Sludge addition saves disposal cost. 48
  • 49. Dr. Engr. Md. Mahmudul HASAN Composting: Disadvantages 1. Capital and operating costs apparently are relatively high. Cost/ton of refuse is about 400-500% that of sanitary landfill if the end product is not sold. 2. Uncertainty of the market for compost as a fertilizer or soil conditioner undermines the desirability of the system especially in large population centers. 3. Seasonal use of the end product may require special marketing procedure or outdoor storage. 4. Refuse that damages the grinders must be removed and disposed of separately e.g. pipes, heavy stones. 5. Trained personnel to operate composting plants are not readily available. 6. Site procurement is a problem as every kind of refuse disposal facility is considered a nuisance in most neighborhoods. 7. A secondary disposal is always required, working also as alternate outlet in case of breakdown and for inorganic and non-recyclable materials. 49
  • 50. Dr. Engr. Md. Mahmudul HASAN Composting: Reasons of failure Most of mechanized compost plants have failed for economic or technical reasons: Economic reasons i. Cost of raw materials – often this involves the cost of transportation of feed materials, ii. Quality of the compost – this is governed by the quality of raw materials and maintenance of the composting process, iii. Location of composting plants – this influences the costs of transportation for both raw materials and the end product, iv. Government policies and legislation – for example, the import policy for chemical fertilizers, source separation initiatives, incentives to encourage recycling and resource recovery etc., v. Public awareness – public education and information, vi. The availability and cost of other soil conditioners and fertilizers. Technical reasons i. In many situations, the mechanised pre-processing of mixed waste cannot accommodate the diverse nature of solid waste, and it therefore does not produce good compostable materials. ii. In other cases, inadequate attention is paid to ensuring the proper environment and nutrients to improve the performance of composting (biological) processes. 50
  • 51. Dr. Engr. Md. Mahmudul HASAN Composting: O2 requirements The process is performed under aerobic conditions. The products of aerobic digestion and the amount of oxygen required for the job are expressed by the following equation: Where, 51
  • 52. Dr. Engr. Md. Mahmudul HASAN Composting: O2 requirements Determine the amount of oxygen required to compost 1000 kg of solid wastes. Assume that the initial composition of the material to be composted is given by [C6H7O2(OH)3]5 , that the final composition is estimated to be [C6H7O2(OH)3]2, and that 400 kg of material remains after the composting process. 52
  • 53. Dr. Engr. Md. Mahmudul HASAN Composting: Vermicomposting o Also called 'vermiculture', 'composting with worms’ or 'worm composting’ o Uses worms and micro-organisms to break down organic materials under aerobic conditions, but at a relatively low temperature, to give nutrient-rich end product (compost). o Specific species of earthworms (for example, eisenia foetida – commonly known as redworms, brandlingworms or tigerworms, and lumbricus rubellus, are suitable for vermicomposting. o The worms (a worm is made of about 70-95% water and 5-30% protein) consume both partially decomposed organic materials and micro-organisms which are also constantly involved in composting o The average weight of 2,000 adult worms is about 1kg, and these worms can be accommodated in an area of 1m2. o Produce better quality rich in nitrates, potassium, phosphorus, calcium and magnesium) and finer (enhance particle size reduction) of compost. o Since this type of compost is rich in nutrients, so can mix this compost with ordinary compost before using as manure. o The composting in this process takes place in a relatively cool environment (0o C to 30o C) so, the end product may contain pathogens. o Compared to ordinary composting, this process requires more manpower and careful control of the environment (mainly temperature and moisture levels). 53
  • 54. Dr. Engr. Md. Mahmudul HASAN Composting: Vermicomposting 54
  • 55. Dr. Engr. Md. Mahmudul HASAN Composting: Barrel composting o Barrel composting has been developed especially for developing countries as an alternative low-cost and sustainable waste management system. o Municipal domestic waste is kept within the barrel for aerobic digestion for about one month. After digestion is complete, the waste is taken out and processed to maturation stage. o The barrel may be perforated on its surface and a perforated pipe may be inserted and attached to the base of the barrel to sustain the aerobic conditions. The top cover of the barrel prevents rainwater from entering the barrel. 55
  • 56. Dr. Engr. Md. Mahmudul HASAN Composting: Barrel composting 56
  • 57. Dr. Engr. Md. Mahmudul HASAN Composting: Barrel composting A barrel of 55 gal (US) litres has been used to install a barrel composting plant at Gazipur (population 500) in Bangladesh. The plant will operate throughout the year. The average temperature measured within the waste is 43 oC. The composition of solid waste in a 100 kg as shown in table. The targeted loss of volume is 54% and the average density of the waste is 450kg/m . The waste generation rate of Gazipur is 0.4kg/capita/day. Calculate the number of barrels required in barrel composting plant. 57
  • 58. Dr. Engr. Md. Mahmudul HASAN Composting: Barrel composting Solution: Step 1: Find out the total composition In the composting process, the non-compostable materials must be screened out for digestion of the waste. So, in this 100kg sample, cardboard (8kg), plastics (5kg) and wood (5kg) must be screened out. 58
  • 59. Dr. Engr. Md. Mahmudul HASAN Composting: Barrel composting 59
  • 60. Dr. Engr. Md. Mahmudul HASAN Composting: Barrel composting 60
  • 61. Chapter 08: Ultimate Disposal 61 Dr. Engr. Md. Mahmudul HASAN
  • 62. Dr. Engr. Md. Mahmudul HASAN Final disposal of solid waste Final disposal of the municipal solid waste can be accomplished in following ways: 1. Into water bodies 2. Onto land (1) open dumping (Controlled and uncontrolled) (2) sanitary landfilling. 62
  • 63. Dr. Engr. Md. Mahmudul HASAN Final disposal of solid waste (1) Open dumping (Controlled and Uncontrolled): o Open dumping refers to placing the solid waste, at a designated place, without any cover. o A cheap disposal method o Highly undesirable as it poses serious threats to the air, soil, ground water and human health (Fig. 8.1). Although some measures are taken to minimise the risk to public health and the environment in controlled open dumping method. o Open dumping results in littering of waste with wind. Rain water may result in dissolving organics and toxic matters, which may either infiltrate and join groundwater or may join surface water due to run off. o Poor implementation of environmental regulations, lack of awareness, technical expertise and resources are the major factors for the use of this method. o It is mostly practiced in developing countries. 63
  • 64. Dr. Engr. Md. Mahmudul HASAN Final disposal of solid waste 64
  • 65. Dr. Engr. Md. Mahmudul HASAN Final disposal of solid waste (2) Sanitary landfill: o Sanitary landfill is a scientific and an engineered method of final disposal of solid waste, in a manner that protects the public health and the environment. o The process by which wastes are placed in the landfill is called landfilling. o Historically, the most economical and environmentally acceptable method for the disposal of solid waste in the developed countries and in some of the developing countries too. Even with implementation of waste reduction, recycling and transformation technologies, disposal of residual solid wastes in landfills still remains an important component of integrated solid waste management. o It includes the following activities: i. Monitoring of the incoming waste stream, ii. Placement and volume reduction of the waste through mobile compactors such as bulldozers etc., and iii. Installation of the landfill and environment control facilities. o In a sanitary landfill, waste is spread in thin layers, compacted to the smallest practical volume, and covered with the soil or other suitable material at the end of each day. When the disposal site reaches its ultimate capacity i.e., after all disposal operations are completed, a final layer of 0.6 meter thick or more of cover material is applied. o A typical sustainable sanitary landfill site is show in Fig. 8.2. 65
  • 66. Dr. Engr. Md. Mahmudul HASAN Final disposal of solid waste 66
  • 67. Dr. Engr. Md. Mahmudul HASAN Final disposal of solid waste Open dump Controlled dump Sanitary landfill o Poorly sited o Unknown capacity, No cell planning o Little or no site preparation o No leachate management o No gas management o Only occasional cover o No compaction of waste o No fence, no record keeping o Waste picking and trading o Planned capacity o No cell planning o Grading, drainage in site preparation o Partial leachate management o Partial or no gas management o Regular cover o Fence o Basic record keeping o Controlled waste picking and trading o Site based on EnRA o Planned capacity, o Designed cell development o Extensive site preparation o Full leachate and gas management o Daily and final cover, compaction o Fence and gate o Record volume, type, source o No waste picking Characteristics 67
  • 68. Dr. Engr. Md. Mahmudul HASAN Final disposal of solid waste Open dump Controlled dump Sanitary landfill o Easy access o Extended lifetime o Low initial cost o Aerobic decomposition o Low cost, access to waste pickers o Materials recovery, income o Less risk of environmental contamination o Permits long term planning o Low initial cost o Easier rainfall runoff o Moderate cost o Extended lifetime o Controlled access and use o Materials recovery, Income, lower risk to o pickers o The most economical method of disposal where land s available. o Initial investment is low. o Can receive all types of solid wastes, eliminating the necessity of separate collections. o Minimised environmental risk o Permits long term planning o Reduced risk o Vector control, aesthetics o Extended lifetime and flexible o Secure access, gate records o Eliminate risk to pickers Advantages 68
  • 69. Dr. Engr. Md. Mahmudul HASAN Final disposal of solid waste Open dump Controlled dump Sanitary landfill o Environmental contamination o Overuse, many noxious sites o Unsightly, needs remediation o Water contamination o Risk of explosions o Vectors/disease, Shorter lifetime o Indiscriminate use, Vermin o No record of landfill content, o Least efficient for material record o Perhaps less accessible o Perhaps environmental contamination o Slower decomposition, so total cost is high o Maintenance required o Harassment, Possible displacement of o pickers and buyers, Fewer recyclable o resources o In highly populated areas, suitable land may not be available within an economical hauling distance. o Located in residential area can provoke extreme public opposition. o Access, longer siting process o Cost, preparation time o Slower decomposition o Regular maintenance o Equipment use o Displacement of pickers and buyers o Loss of recyclable resources o Methane, an explosive gas, and other gases produced may become a hazard or nuisance. Disadvantages 69
  • 70. Dr. Engr. Md. Mahmudul HASAN Landfill Classification Depending on the principles of a particular landfill waste management strategy, landfills may be classified as: i. dilute and attenuate landfills ii. containment landfills The present design and operation practices of landfill are mostly focused on the containment principle. i. Dilute and attenuate landfills o These landfills allow leachate to be absorbed within the waste or to migrate into the surrounding environment for attenuation by physico-chemical or biological processes. o This involves processes of dilution and dispersion if attenuation of leachate is not achieved within the landfill environment. Therefore, the landfill designer should clearly visualise the hydrogeological and geochemical characteristics of the site and surrounding environment. o These landfills involve the risk of contamination of water and soils. 70
  • 71. Dr. Engr. Md. Mahmudul HASAN Landfill Classification ii. Containment landfills o In these landfills, leachate is contained within the landfill site boundary by the use of liner materials. o Containment involves the degradation of waste within the landfill. It also involves controlled migration of gas within the landfill. o This requires a much greater degree of site design, engineering and management, and thus ensures a larger degree of protection to public health and the environment. o The main components of a containment-type sanitary landfill are illustrated in Figure 9.1. o In a contemporary context this is the most acceptable means of disposal of waste to land. 71
  • 72. Dr. Engr. Md. Mahmudul HASAN Major stages of waste degradation in landfills The process of degradation of the organic fraction of solid waste within a landfill may be broadly divided into five stages. Organic materials degrade in presence of oxygen (aerobic conditions) in the first and fifth stages, but they degrade essentially in the absence of oxygen (anaerobic conditions) in the second, third and fourth stages. All these processes are successive, but because of heterogeneous characteristics of waste they may take place at any time until all of them have advanced to stage five. 72
  • 73. Dr. Engr. Md. Mahmudul HASAN Sanitary Landfill: Planning, Design and Operation Planning, Design and Operation of Sanitary Landfills The planning and design of sanitary landfills involves careful consideration at all stages from site selection to final closure and post-closure care. The stages involved in well-engineered sanitary landfills are: i. siting ii. design iii. construction and operation iv. closure and post-closure care v. environmental monitoring and corrective action. o Siting A site investigation is the important element in identifying a possible landfill site. The site selection process should accommodate the preliminary investigation/surveying of a number of sites with a checklist of important points to consider along with the assessment of environmental impacts. The various merits and demerits should be addressed at a public meeting to minimise public concern at the beginning of the process. The evaluation process may consider a wide range of site selection factors including: 73
  • 74. Dr. Engr. Md. Mahmudul HASAN Sanitary Landfill: Planning, Design and Operation 1. Location restriction –In many industrialised countries, a number of location restrictions are imposed by the state. For example, the EPA Regulations on Criteria for Classification of Solid Waste Disposal Facilities and Practices (40 CFR 258) (USEPA, 1993) presents the location restrictions as shown in Table 9.3 to address both the potential effects that a MSW landfill unit may have on the surrounding environment and the effects that natural- and manmade conditions may have on the performance of the landfill unit. 2. Type of waste –The characteristics of the waste to be landfilled indicate the risks associated with particular landfill operation practices. 3. Size –This depends on the expected life of the landfill site (i.e. the number of years for which it can operate) and the quantities of waste generated. One should take into account projected future populations and waste generation rates for the entire design life. The density of landfilled waste depends on the degree of compaction, depth of waste filled, depth of cover materials, properties of the cover materials and the stage of decomposition. UKDOE 3 3 (1995) reports a range of density from 0.4 tonnes/m to 1.23 tonnes/m . For 3 3 planning purposes, a density of between 0.65 tonnes/m to 1.0 tonnes/ m may be used. 74
  • 75. Dr. Engr. Md. Mahmudul HASAN Sanitary Landfill: Planning, Design and Operation 4. Transport to site –The site should be easily accessible and should be close enough to the major waste generation areas. The method of transport should be considered. If transport is to be by road, the present quality of road must be considered and the potential impact of heavy waste vehicle traffic on road surfaces. Proper attention should be paid to the present use of the road, congestion, areas through which the waste transportation vehicles will have to travel and so on. 5. Soil type –Clay and silty soil is a more desirable landfill base material than sand, gravel or organic clay deposits. 6. Topography –Equipment operation and movement of vehicles becomes difficult on steep slopes (severe in >15%, moderate in 3-15% and minimal in <3%). 7. Hydrological, geotechnical and hydrogeological characteristics of the site –The hydrological characteristics will help to identify the expected quantities of leachate and hence the form of leachate management system. Knowledge of the geotechnical and hydrogeological characteristics (the geological factors relating to water) is necessary to determine what natural protection of the groundwater etc. is available against pollution by the leachate and landfill gas, and to identify potential flow path of leachate and gases. For example, a proposed site which is underlain naturally by clay may need little in the way of extra leachate protection. However, a site which is underlined by fissured rock will pose greater problems, as leachate may be able to percolate into groundwater. The degree of limitation of landfill design associated with groundwater occurrence appears to be severe, moderate or minimal if groundwater depths are less than 3m, 3- 7.5m and more than 7.5m respectively. 75
  • 76. Dr. Engr. Md. Mahmudul HASAN Sanitary Landfill: Planning, Design and Operation 8. Climatic conditions –Extreme climatic conditions may disrupt landfill operation. For example, heavy rainfall during the rainy season in a particular area may demand the use of a separate landfill. 9. Drainage –The resent drainage conditions of a site need to be assessed, including the existence of a watercourse within or adjacent to the site and the cost of surface water diversion (if required). The desirable location of a landfill site from a stream/ lake is more than 300m. 10. Availability of land –A reasonable size of landfill site with an adequate buffer zone should be selected to maximise its cost-effectiveness. Availability of land for cover materials is also an important consideration. The cost of auxiliary facilities do not increase much with an increase in landfill area. 11. Land use –This is a very important consideration because the presence of places of historic or cultural significance may restrict the use of the site for landfill. Other factors such as the location of groundwater abstraction points for drinking or irrigation purposes, overhead or underground electrical cables and so on must all influence the location of the site. The extent of limitation of landfill location associated with wells appears to be severe, moderate or minimal if they are at a distance of less than 90m, 90-300m and more than 300m respectively. 76
  • 77. Dr. Engr. Md. Mahmudul HASAN Sanitary Landfill: Planning, Design and Operation 12. Impact on the locality – It is important to consider how the development of a landfill site at a location will impact the local area in terms of noise, odour, traffic, possible leachate and gas pollution, the spreading of disease vectors, hazards to health and the value of property and so on. There should be an adequate buffer zone from the nearest housing. 13. Local opposition –The opposition of local people to the site selection may be reduced by including them in the decision making process. 14. Ultimate use for completed landfill –This will affect landfill design and operation, and the remediation cost is always much higher if the ultimate use is not planned at the earliest stage. 15. Cost of land –This will always be a key consideration in the decision-making process. 77
  • 78. Dr. Engr. Md. Mahmudul HASAN Movement and Control of Leachate in Landfill Leachate may be defined as liquid that has percolated through solid waste and is comprised of dissolved and suspended materials and/or microbial contaminants. In most landfills the leachate is composed of the liquid produced from the decomposition of the wastes and liquid that has entered the landfill from external sources (such as surface drainage, rainfall etc.). In general, it has been found that the quantity of leachate is a direct function of the amount of external water-entering the landfill. In fact, if a landfill is constructed properly, the production of measurable quantities of leachate can be eliminated. When sewage sludge is to be added to the solid wastes to increase the amount of methane produced, leachate control facilities must be provided. A leachate management system includes an efficient leachate collection system for its proper collection and treatment. Representative data on the chemical characteristics of leachate, reported in Table 8.2, indicates that the range of concentration values for the various constituents is rather extreme. For this reason; no average value can be given for leachate. The typical values reported are intended to be used only as a guide. 78
  • 79. Dr. Engr. Md. Mahmudul HASAN Leachate Treatment 79
  • 80. Dr. Engr. Md. Mahmudul HASAN Leachate Treatment Treatment processes for leachate 80
  • 81. Dr. Engr. Md. Mahmudul HASAN After-use of Landfill Sites After-use of Landfill Sites Once a landfill site is closed and the capping completed, the area is then available for further use. In high-income countries, landfill sites often become recreational areas such as parks, golf courses or nature reserves. However, in some situations, where land is in higher demand, there may be strong competition for the use of the land. When deciding on the after-use of the site the properties of the land must be fully considered and the following potential should be addressed: o Fill settlement (total as well as differential settlement) o Load-bearing capacity o Hazards associated with combustible and potentially explosive gases o Degree of stabilisation and the corrosive nature of decomposition products. 81
  • 82. Chapter 09: Special Waste management (H-Waste and E-Waste) 82 Dr. Engr. Md. Mahmudul HASAN
  • 83. Dr. Engr. Md. Mahmudul HASAN Special wastes In addition to residential and commercial areas, solid waste is also generated from other sources like healthcare facilities, industries, electronic shops, packaging services and slaughterhouses. These are termed as special wastes. Handling, collection and disposal of these wastes is sometimes quite different from municipal solid waste. Hence these are discussed separately. Healthcare Waste and its Source The waste generated from the healthcare facilities is called “healthcare waste” or “medical waste”. Healthcare waste in generated as a result of the following activities: a) Diagnosis and treatment of diseases at healthcare facilities b) Research activities in biomedical research centers c) Production and testing of the pharmaceuticals. Broadly, the main sources of healthcare waste are: hospitals, clinics, laboratories, dispensaries, pharmacies, nursing homes, maternity centers, blood banks, research institutes and veterinary hospitals. Such a waste is also generated when healthcare is being provided to the patient at home and is usually mixed with municipal waste. 83
  • 84. Dr. Engr. Md. Mahmudul HASAN Special wastes Healthcare Waste Management: The healthcare waste management is a sensitive issue and comprises of knowledge of quantity and quality of waste, its storage, handling, transportation and disposal in a manner that helps in (1) containment of infections; and (2) reduces public health risks both within and outside the healthcare facility. Generation rates, for hospitals, are normally expressed as kg/bed of the hospital/day. After generation, waste is segregated, stored on site, transported within and outside the hospital, treated and finally disposed. Hospitals generate large quantities of solid waste which can be categorized into two distinct types i.e. (1) Non- hazardous waste: which is not infected, does not entail more risk and hence comparable to normal domestic solid waste. Usually it constitutes 75 – 90% of the total quantity of waste generated in a hospital. 84
  • 85. Dr. Engr. Md. Mahmudul HASAN Special wastes (2) Hazardous waste: consists of materials that are susceptible to contain pathogens (or other toxins) to cause diseases to a potential host. This waste may be contaminated by one or more types of bacteria, viruses, parasites or fungi. Usually, it is 10 – 25% of the total hospital waste. More categorized as this Fig: 85
  • 86. Dr. Engr. Md. Mahmudul HASAN Special wastes 86
  • 87. Dr. Engr. Md. Mahmudul HASAN Special wastes 87
  • 88. Dr. Engr. Md. Mahmudul HASAN Special wastes 88
  • 89. Dr. Engr. Md. Mahmudul HASAN Special wastes 89
  • 90. Dr. Engr. Md. Mahmudul HASAN Special wastes Electronic Waste (E-Waste) Management: E-waste is term used for electronic products nearing the end of their useful life. It includes old, outlived or discarded electrical and electronic equipment and appliances such as computers, televisions, VCRs, stereos, copiers, fax machines, electric lamps, cell phones, audio equipment, refrigerators, and batteries which have been discarded by their original users. Broadly, e-waste is loosely discarded, surplus, obsolete, broken, electrical or electronic devices. The processing of electronic waste in developing countries causes serious health and pollution problems due to the fact that electronic equipment contains toxic contaminants such as lead, cadmium, beryllium and brominates flame retardants. Even in developed countries recycling and disposal of e-waste involves significant risk. 90
  • 91. Dr. Engr. Md. Mahmudul HASAN Special wastes E-Waste Management Challenges: a) Lack of Awareness regarding E-waste management. b) Inadequate regulatory measures, inadequate strategies and poor implementation of law. c) Lack of technical expertise in this area. d) Non availability of technology for recycling of E-waste. e) Lack of coordination among different stakeholders and ministries / departments. f) Lack of system to regulate the import of refurbished e-waste. g) Low attention from government on ewaste. h) Inadequate funding available for the implementation of various provisions of Basel Convention. i) Non availability of proper inventories of hazardous waste, particularly in Ewaste. j) No research and development work in this area so far. k) Non availability of guidelines for recycling and disposal of E-waste. l) Inadequate public awareness about the toxicity of chemicals in E-waste and their health impacts. m) Unskilled workers/technicians for handling of E-waste. n) Lack of proper system for inventory of imported and local E-waste. o) No mechanism for developing centralized E-waste recycling facility. 91
  • 92. Dr. Engr. Md. Mahmudul HASAN Special wastes 92
  • 93. Dr. Engr. Md. Mahmudul HASAN 93 Thanks “STUDY HARD, no matter if it seems impossible, no matter if it takes time, no matter if you have to stay up all night just remember that the feeling of success is the best thing in the entire world”