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UNIT II

ON-SITE STORAGE & PROCESSING

2 MARKS:

1. What is meant by Onsite Handling of Solid waste?Onsite handling refers to the activities associated with the handling of solid wastes

until they are placed in the containers used for their storage before collection. Dependingon the type of collection service, handling may also be required to move the loadedcontainers to the collection point and to return the empty containers to the point wherethey are sorted between collections.

2. What are the factors that must be considered in the onsite storage of solid waste?1. Type of Container.2. The Container location.3. Public health and Aesthetics and4. The collection methods that must be used.

3. What is Public health importance of Onsite Storage and handling of waste?The most important factor in Onsite storage and handling of residential waste is that

they are generated in areas with limited storage space. As a result they can havesignificant public health and aesthetic impacts.

Public health concerns are related to the infestation of areas used for the storage ofsolid wastes with vermin and insects that often serve as potential reservoirs of disease.Aesthetic considerations are related to the production of odors and the unsightlyconditions that can develop when adequate attention is not given to the maintenance ofsanitary conditions.

4. What is meant by onsite processing of solid waste?It must be kept in mind that onsite processing of solid waste may take place at a time

before collection (before, during, or after storage) which includes Grinding, sorting,compaction, shredding, composting and hydropulpery. These methods are intended to (i)reduce the volume (ii) alter the physical form or (iii) recover usable materials from solidwastes.

5. Mention the On-site processing methods of solid waste?1. Grinding. 2. Sorting. 3. Compaction. 4. Shredding. 5. Composting.6. Hydropulpery.

6. How do you classify the buildings for onsite storage & handling?A classification based on the number of stories is low-rise, under four stories;

medium-rise, from four to seven stories; and high rise, over seven stories. The low-riseresidential dwellings are further subdivided into the following categories: single-family

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detached, single-family attached such as row or townhouses; and multifamily, of whichgarden apartments are typical.

7. What is meant by onsite segregation of solid waste?Sorting of solid waste into biodegradable fraction, combustible fraction, recyclable

fraction, and Hazardous fraction at the point of collection itself is called onsitesegregation of solid waste. Onsite segregation may also include intermediate sortingstations wherein the solid wastes are separated, baled and converted into a form whichcan easily be transported to the treatment or disposal yard.

8. What are the materials used for containers for collection of solid waste?Galvanized metal containers, Plastic containers, Container liners, Temporary and

disposable containers(paper or plastic bags), Large portable or fixed containers, Largeopen top containers, enclosed storage containers, containers equipped with self-containedcompacting mechanism, special containers that are sealed to carry toxic or radioactivewastes.

9. What is meant by shredding?Cutting the bulky Solid waste into smaller pieces with the help of a mechanically

driven blade chopper mechanism. Once the solid waste is cut into smaller pieces it canthen easily be transported and handled. This process results in mechanical volumereduction.

10. What is meant by Pulping?Adding water to grind the solid waste onto a pulp so that solid waste reduces in

volume and exhibits a form that can be easily transported and easily handled.

11. What is meant by Compaction of MSW?Mechanical size reduction of solid waste with the help of mechanical force applied

externally by compactors of various kinds is called compaction. The Compactors can bevehicles allowed to run over a heap of solid waste or crushers that can apply pressure inall directions to the solid waste.

12. What is meant by home composting?The process of converting the biodegradable fraction of the solid waste biologically

into rich humus like form by providing abundant oxygen to the microbes, so that the end-product could be used as nutrient value for plants is called composting. In this methodthis end product called compost can be marketed.

13. State the advantages of on-site segregation of solid waste?The advantage of on-site segregation of solid waste are as follows

1. Waste minimization: The separation of recoverable materials like metal, plasticse.t.c. from waste result in less quantity of remaining waste which are to be treated.Hence the cost of treatment reduces. Also these recoverable materials like plastic,ferrous metals, etc. fetch revenue in those industries that utilize them.

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2. On-site segregation may include intermediate sorting stations wherein the solidwastes are separated, baled and converted into a form which can easily betransported to the treatment or disposal yard.

3. Advantage of segregation: If waste cannot be segregated in the beginning, then itbecomes very difficult to segregate them at the end in the dumping yard. Also thesolid wastes which are segregated in the beginning are sent to respective treatmentfacilities. eg. The garbage can be sent to composting yard to obtain bio-manure,while the combustible fraction of the rubbish can be sent for incineration fromwhere electricity can be produced via thermal power plant and also other greenwaste can be sent for sanitary land filling from where methane is produced. Thus allfractions of the solid waste are easily treated separately from which beneficialproducts are obtained.

14. What are the different on-site process on solid waste?A. Mechanical Volume and Size reduction:

1. Compaction or Volume reduction2. Shredding or Size reduction( Flail mills, Hammer mills, Grinders and Wetpulping)

B. Component Separation:1. Screening (Vibrating screen, Trommel screen, disc screen)2. Magnetic separation (Ferromagnetic separators and eddy current separators)3.Air classification (Horizontal air classifier, Inclined and moving chair curtains,

Cyclone separators and Vibrating tables)4. Other separation techniques

C. Drying and Dewatering:1. Convection drying(Counter-current Direct-heat Rotary drum dryer)2. Centrifugation and filtration

15. What is the purpose of reduction in volume of solid waste?If the volume of solid waste is reduced then the final volume to be treated is also

reduced thus saving in cost. Also the transport cost reduces.

16. What is the essential of proper storage of MSW?1. The solid waste storage facility must have lid or must be covered on top to prevent

litter and bad odour problems.2. The storage bin or container must be of sufficient volume or capacity to temporarily

store the waste before unloading. Often the container overflows due to insufficientsize.

3. Municipal solid waste must not be kept more than 24 hours in the storage containersince the organic waste starts to undergo putrefaction leading to odour problems.

4. The municipal workers as well as the people should not touch the solid wastedirectly by hand. Instead gloves must be provided to handle the solid waste. Alsosolid waste must be segregated and put into colour coded bags before discharge intostreet containers.

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17. What is recovery and recycling of solid waste? List out the operations involvedin recycling?The collection of materials like glass, plastics, ferrous metals, etc from solid waste andthe utilization of these materials as raw material in the manufacture of new products iscalled recycling. The collection of materials like paper, cardboard, coir may be ofsufficient value to warrant their separation and can be converted into energy source(through incineration or direct combustion in power boilers to produce steam) is calledenergy recovery.Operations involved in recycling: Handsorting, Air separation, Magnetic separation,Screening, Inertial separation, Floatation, Optical sorting, Electrostatic separation,Drying and dewatering, centrifugation and filtration.

18. What is the importance of waste stream assessment(WSA)?A waste stream assessment is the process of understanding the mix of material in

the local waste stream. Waste stream assessment(WSA) is a means to determine thebasic aspects of quantity (i.e., the amount of waste generated in the community, bothin terms of weight and volume), composition (i.e., the different components of wastestream) and the sources of wastes. A waste stream assessment can be as simple asevaluating existing data that a local government already keeps or it may include anextensive waste sort to estimate quantities of various materials in the waste stream.

WSA is not a one-time activity. It is a continuous and dynamic process, becausethe characteristics of wastes differ depending on the regions, communities, seasons,e.t.cIMPORTANCE:A waste stream assessment should not be conducted only to gather dust on a shelf. Itshould be a dynamic record that helps a local government prioritize its waste reductionactivities. A waste stream assessment provides local governments with the followingbenefits: Identifies major material categories and their quantities in the waste stream. Helps rank materials according to their impact on the local waste stream. Helps identify specific commercial/industry types and/or facilities that should be

targeted for waste reduction. Assists in creating local educational materials on solid waste management.

Although a waste stream assessment is important, it should be remembered thatrecycling is a market-driven endeavour, and markets will be the ultimate factor used totarget materials for recycling.The main aims of a waste assessment are to: Identify each waste stream on or leaving the site. Quantify and characterize each waste stream to establish benchmark data. Establish how and why each waste stream is generated. Calculate costs incurred with treatment, storage, handling and disposal of wastes,

including quantifying associated labour, energy, water and lost raw material costswhere possible.

Determine liabilities associated with waste generation. Identify options for more efficient and effective waste management (for example

identify reduction/diversion opportunities).

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19. What is meant by E-Waste management?It involves the management of electronic materials that have been discarded as scrap.The process of E-Waste management consists of separation of various electroniccomponents, their treatment and their recovery or disposal of electronic waste in amanner that is environment friendly.

20. List the parameters influencing the capacity of containers?1. The volume and characteristics the solid wastes to be collected.2. The collection frequency3. The choice of materials and the available budget.4. The space available for the placement of containers.5. Type of collection system adopted.6. Manpower and no. of collection trips per day.

21. What is meant by positive and negative sorting?In a solid waste stream, the material to be separated, is picked out first along thewaste stream in a segregation process is called positive sorting. In a solid wastestream, the removal of all other components finally leaves the rejected material andsuch a sorting is called negative sorting of the final material.

22. What is the effect of storage on public health?1. Litter from storage bins will spread disease to humans, animals and living beings.2. Bad odour and unsightly conditions may emanate from open storage bins.3. Municipal workers and children are the risk groups upon which the diseases easily

spread.4. During rainy season the storm water that flows through the solid waste litter, carry

toxic substances which ultimately flow into the river or stream thus resulting infish kills and flora damage.

23. What is the use of Jigs in separation process?Jigs are used to separate light density particles from heavy density particles in awaste stream.

12 Marks:

1. Explain the Waste Handling, Sorting, Storage, and Processing at the Source:

Waste handling and sorting involves the activities associated with management of wastesuntil they are placed in storage containers for collection. Handling also encompasses themovement of loaded containers to the point of collection. Sorting of waste components isan important step in the handling and storage of solid waste at the source. For example,the best place to separate waste materials for reuse and recycling is at the source ofgeneration. Households are becoming more aware of the importance of separatingnewspaper and cardboard, bottles/glass, kitchen wastes and ferrous and non-ferrousmaterials.

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On-site storage is of primary importance because of public health concerns and aestheticconsideration. Unsightly makeshift containers and even open ground storage, both ofwhich are undesirable, are often seen at many residential and commercial sites. The costof providing storage for solid wastes at the source is normally borne by the household inthe case of individuals, or by the management of commercial and industrial properties.Processing at the source involves activities such as backyard waste compostingCollection: The functional element of collection includes not only the gathering of solidwastes and recyclable materials, but also the transport of these materials, after collection,to the location where the collection vehicle is emptied. This location may be materialsprocessing facility, a transfer station, or a landfill disposal site.Sorting, Processing and Transformation of Solid Waste: The sorting, processing andtransformation of solid waste materials is the fourth of the functional elements. Therecovery of sorted materials, processing of solid waste and transformation of solid wastethat occurs primarily in locations away from the source of waste generation areencompassed by this functional element. Sorting of commingled (mixed) wastes usuallyoccurs at a materials recovery facility, transfer stations, combustion facilities, anddisposal sites. Sorting often includes the separation of bulky items, separation of wastecomponents by size using screens, manual separation of waste components, andseparation of ferrous and non-ferrous metals. Waste processing is undertaken to recoverconversion products and energy. The organic fraction of Municipal Solid Waste (MSW)can be transformed by a variety of biological and thermal processes. The most commonlyused biological transformation process is aerobic composting. The most commonly usedthermal transformation process is incineration. Waste transformation is undertaken toreduce the volume, weight, size or toxicity of waste without resource recovery.Transformation may be done by a variety of mechanical (eg shredding), thermal (e.g.incineration without energy recovery) or chemical (e.g. encapsulation) techniques.Transfer and Transport: The functional element of transfer and transport involves twosteps: (i) the transfer of wastes from the smaller collection vehicle to the larger transportequipment and (ii) the subsequent transport of the wastes, usually over long distances, toa processing or disposal site. The transfer usually takes place at a transfer station.Disposal: The final functional element in the solid waste management system is disposal.Today the disposal of wastes by landfilling or uncontrolled dumping is the ultimate fateof all solid wastes, whether they are residential wastes collected and transported directlyto a landfill site, residual materials from Materials Recovery Facilities (MRFs), residuefrom the combustion of solid waste, rejects of composting, or other substances fromvarious solid waste-processing facilities. A municipal solid waste landfill plant is anengineered facility used for disposing of solid wastes on land or within the earths mantlewithout creating nuisance or hazard to public health or safety, such as breeding of rodentsand insects and contamination of groundwater.

2. Explain the methods of Waste minimization.

Waste minimization or reduction at source is the most desirable activity, becausethe community does not incur expenditure for waste handling, recycling and disposal of

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waste that is never created and delivered to the waste management system. However, it isan unfamiliar activity as it has not been included in earlier waste management systems.To reduce the amount of waste generated at the source, the most practical and promisingmethods appear to be (i) the adoption of industry standards for product manufacturingand packaging that use less material, (ii) the passing of laws that minimize the use ofvirgin materials in consumer products, and (iii) the levying (by communities) of cess/feesfor waste management services that penalize generators in case of increase in wastequantities.

Modifications in product packaging standards can result in reduction of wastepackaging material or use of recyclable materials. Minimization of use of virgin rawmaterials by the manufacturing industry promotes substitution by recycled materials,sorting at source, recycling at source and processing at source (e.g. yard composting) helpin waste minimization.

One waste management strategy used in some communities in developedcountries is to charge a variable rate per can (or ton) of waste, which gives generators afinancial incentive to reduce the amount of waste set out for collection. Issues related tothe use of variable rates include the ability to generate the revenues required to pay thecosts of facilities, the administration of a complex monitoring and reporting network forservice, and the extent to which wastes are being put in another place by the generatorand not reduced at source.

3. Explain the segregation of MSW.

Municipal waste is being generated in ever increasing volumes in the urban areas. Theschematic diagram describes how municipal solid waste is segregated and where it can beused.

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4. Explain the processing of MSW?

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5. Explain the shredding process.

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6. Explain the types of magnetic separation.

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7. Explain the On-site storage of MSW.

In a usual setting of municipal solid waste management service, on-site storage is thepoint at which the service demand meets its supply, or more specifically, it is where solid

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waste generated is stored for collection by the municipal authority or its contractor. On-site storage (often in some sort of container such as a bin, basket or bag) can be classifiedunder two categories: (1) individual storage serving the occupiers of a house, shop oroffice, and (2) communal storage serving the occupiers of more than one house, shop oroffice. Normally, the responsibility for the provision and maintenance of individualstorage rests with the owner/occupiers of each unit while the municipal solid wastemanagement authority assumes the responsibility of providing and maintainingcommunal storage. Therefore, it is not easy to assign the previously identified indicatortypes to the on-site storage indicators. The indicators relating to individual storage aregenerally classified as socioeconomic and physical condition indicators while thoserelating to communal storage are considered to be resource input indicators.The following indicators are useful for the design and operational management of a solidwaste collection system.(a) Individual storage- Type (e.g. bin, bag, basket, no container)- Size or capacity (litre)- Material (e.g. plastic, metal, bamboo)- Number and location (on a map)- Maintenance condition (by observation)- Cover or lid (by observation)- Use of standardized containers (%)(b) Communal storage- Type (e.g. bin, bag, basket, no container)- Size or capacity (litre or m3)- Material (e.g. plastic, metal, wood, bamboo)- Number and location (on a map)- Maintenance condition (by observation)- Cover or lid (by observation)- Maximum distance from houses (m)(c) Cost- purchase cost of individual container ($/container)- purchase cost of communal container ($/container)- repair cost of communal container ($/container