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UNIT II ON-SITE STORAGE & PROCESSING Syllabus: On-site storage methods – materials used for containers – on-site segregation of solid wastes –public health & economic aspects of storage – options under Indian conditions – Critical Evaluation of Options.
Introduction • The handling, storage and processing of solid wastes at the source before they are collected is the 2 nd of 6 functional elements of MSWM. • This unit includes a description and discussion of the Handling, Storage and Processing of waste materials at the source.
On-Site Waste Handling • It’s an activity associated with the handling of solid waste until they are placed in containers. • Waste handling depends on types of waste materials separated for reuse and recycling. • Also its an activity to move the loaded containers to the collection point and to return empty containers to the point where they are stored between collections.
On site separation • The separation of waste paper, cardboard, aluminium cans, glass and plastic containers at the source. • It is the most effective ways to achieve recovery and reuse of material. • Stored in a separate container until they are collected.
Waste handling and separation at residential dwellings • For the purpose of handling and separation of wastes, the residential dwellings are classified as (a) Low rise buildings ( < 4 stories ) 1. Single family detached 2. Single family attached (b) Medium rise buildings ( 4 -7 stories ) (c) High rise buildings ( > 7 stories )
Low- Rise Detached Dwellings • Residents or tenants are responsible for placing solid waste, recyclable materials around their dwelling in storage containers. • And also transporting the filled containers to the street curb for collection.
• Waste components separated are placed large containers. • Recyclable materials separated are placed special containers or bags. • In some residents, waste compactors are used to reduce the volume and placed in containers or sealed plastic bags.
Low and Medium – Rise Apartments • Handling are same as low rise dwellings • But waste storage location and collection may be different. • Typical solid waste storage locations include - basement storage - outdoor storage - sometimes compactor storage
Basement storage/Curbside collection • A basement storage room or area provided for storage of solid waste. • Containers used for recycling within or next to storage area. • Residents carry their waste and recyclable to the storage area and deposit. • The maintenance staff is responsible for transporting the containers to street for curbside collection.
Outdoor Storage/ Mechanized Collection • In many low and medium-rise apartments, large waste storage containers are located outdoor. • The large containers are emptied mechanically using collection vehicles equipped with unloading mechanisms. • Containers used for recycling located within the outdoor storage area.
• Residents carry their waste and recyclable materials to the storage area and deposit in appropriate containers. • In some apartments, maintenance staff responsible for above or collect from a utility room located on each floor.
At High-Rise Apartments • Methods of handling involves one or more of the following: 1. Wastes are picked up by building maintenance personnel (or) porters from the various floors and taken to the basement (or) service area. 2. Wastes are taken to the basements by tenants. 3. Wastes discharged in chutes (or) collected in large containers, compacted in to large containers. • In many high rise apartments, solid waste chutes are used with large compactors.
• In some recently constructed apartment buildings, underground pneumatic transport systems used with individual apartment chutes. • The underground pneumatic systems transport wastes from chute discharge point to centralised processing facilities • Both air pressure and vacuum transport systems used in this application.
Typical underground pneumatic waste transport system for high-rise apartment buildings
Waste Handling and Separation at commercial Buildings • Collected in large containers mounted with rollers. • Once filled, these containers removed by service elevators and emptied into 1. Large storage containers 2. Compactors used with storage containers 3. Stationary compactors with designed container 4. Other processing equipments.
• In many office and commercial buildings, the papers collected for recycling. • The waste to be recycled stored in separate containers • In large commercial facilities baling equipment used for paper and can crushers used for aluminium cans
On-Site Storage • The first phase to manage solid waste is at home level. It requires facilities for temporarily storing of refuse on the premises. • Individual house holders (or) tenants have responsibility for onsite storage of solid waste. • Four factors that should be considered in the on-site storage of solid waste are: 1. The effects of storage on the waste components. 2. Type of container to be used
3. The location of containers 4. Public health and aesthetics Effects of Storage on Waste Components • The effects based on the characteristics of waste being stored • These effects of storing wastes include 1. Biological decomposition 2. The absorption of fluids 3. The contamination of waste components
1. Microbiological decomposition • Food and other waste placed in containers immediately start microbiological decomposition (putrefaction) as a result growth of bacteria and fungi. • For extended period of time, flies start breed and odours.
2. The absorption of fluids • Waste components have initial moisture contents are stored together, paper will absorb moisture from food waste and garden trimmings. • Degree of absorption depends on time the waste stored until collection • If stored more than a week in enclosed container, the moisture distributed throughout the waste.
3. The contamination of waste components • Most serious effect of on site storage • Major waste components contaminated by small amount of waste like motor oils, cleaners and paints. • It reduces the value of individual components for recycling
Storage Container • The types and capacities of containers depend on - characteristics and types of solid waste to be collected - the type of collection system in use - the collection frequency - the space available for placement of containers.
Table: Types and sizes of containers used for onsite storage of solid waste Type Capacity Dimensions Unit Range Unit Typical Plastic or Galvanised metal gal 20 -40(30) in 20 D x 26 H Barrel, Plastic, Aluminium or fibre gal 20 -65(30) in 20 D x 26 H Small Container Disposable Paper bags Standard gal 20 -55(30) in 15 W x 12 d x 43 H Leak-resistant gal 20 -55(30) in 15 W x 12 d x 43 H Leakproof gal 20 -55(30) in 15 W x 12 d x 43 H Disposable Plastic bags Medium Container 18 W x 15 d x 40 H yd 3 1 -10(4) in 72 W x 42 d x 65 H Open top, roll off(debris boxes) yd 3 12 -50 ft 8 W x 6 H x 20 L Used with Stationary compactor yd 3 20 -40 ft 8 W x 6 H x 18 L yd 3 20 -40 ft 8 W x 8 H x 22 L Large Container Equipped with self contained compaction mechanism
Contin…. Type Capacity Unit Dimensions Range Unit Typical Large Container, trailer mounted Open top Enclosed, equipped with selfcontained compaction mechanism yd 3 20 -50 ft 8 W x 12 H x 20 L yd 3 20 -40 ft 8 W x 12 H x 24 L D- Diameter, H- Height, L- Length, W- Width, d- depth Note: gal x 0. 003785 = m 3 in x 2. 54 = cm yd 3 x 0. 7646 = m 3 ft x 0. 3048 = m
Container Storage Locations • Container storage locations depends on - type of dwelling or commercial facilities - the available space - access to collection services
Residential Dwellings • Between collections, containers used in lowrise detached dwellings placed 1. at the sides or rear of the house 2. in alleys, where alley collection is used 3. in or next to garage/carport or some common location specifically designed for that purpose. • Two or more dwellings located close, a concrete pad open or surrounded by wooden enclosure.
• For low- and medium-rise apartment buildings include basement storage and outdoor storage. • In large high-rise apartments, waste storage and processing equipment is located in the basement of the building.
Storage containers as per Indian Conditions • The segregation of garbage at source is primarily meant to keep solid waste generated separately in different containers (i. e. ) bio degradable waste in one container (GREEN) and nonbio degradable waste in another container (RED). • The storage of garbage used by pedestrians (or) the floating populations, bins should be located at regular intervals. The bins should be placed on “TWO BINS BASIS”
• Some types of receptacles presently used for storage are: (a) Buckets (b) Plastics / HDPE / MDPE bins (c) Plastic bags (d) Metal bins with (or) without lids. • The MSW Rules, 2000 describes, “ The littering of municipal solid waste shall be prohibited in cities, towns and in urban areas notified by the State Government ”
• Plastic liners for cans and wrapping for garbage reduce the need for cleaning of cans and containers. It avoids bad odors, rat and fly breeding. • Galvanized metal is preferable for garbage storage because it is resistant to corrosion. • Bulk containers are recommended where large volumes of refuse are generated such as hotels, restaurants, apartment houses, shopping centres.
• They should have tightly fitting covers. They must be of such size that, when full, can be lifted easily by one man. • They should be located in a cool place over platforms, at least 30 cm above ground level. • The bins must be emptied at least daily and maintained in clean conditions.
• An adequate number of suitable containers should be provided with proper platforms with stand. • Suitable containers shall be water tight, rust resistant, tight fitting covers, fire resistant, enough size, light in weight, side handle & washable.
On-Site Processing • On site waste processing is used : (a) To reduce the volume (b) To recover usable materials (c) To alter the physical form of the solid wastes.
Onsite Processing Operations I. Low-rise Detached Residential Dwellings 1. Food Waste Grinding 2. Component Separation 3. Compaction 4. Incineration (in fireplaces) 5. Composting II. Low-, Medium-, High-rise Apartments 1. Food Waste Grinding 2. Component Separation 3. Compaction
Grinding of food waste • Food waste grinders used for wastes from preparation, cooking, and serving of foods. • Grinders render the material to suitable for transport through sewer system. • The food waste grinders used where the weight of waste collected person is low. • Where grinders used, the time period between collection is increased.
Separation of wastes • It is one of the most effective way to achieve the recovery and reuse of materials. Compaction • Two principal types of compactors used for processing of wastes in residential dwellings 1. Small (individual) home and apartment compaction units and 2. Large compactors used to compact wastes from a large number of apartments.
1. Home and Apartment Compaction Units • Small compactors manufactured based on the ratio of loose paper and corrugated paper. • It reduces the volume of waste upto 70%. • They can be used for only small proportion of the solid waste generated. • The drawback of compaction, if the wastes to be separated into components at MRF, the compacted waste have to be broken up before sorting.
• Also by compacting, the waste may become so saturated with the liquids present in the food waste that the recovery of paper or other components may not be feasible. 2. Compactors for large Apartment Buildings • Compactor is installed at the bottom of the solid waste chute. • Wastes falling through chute active the compactor by means of photoelectric cells or limit switches. • The compressed waste may be formed into bales and loaded automatically into metal container or paper bags.
• When a bale formed or container or bag filled, the compactor shutdown automatically and warning light turns on. • The operator tie and remove the bale from compactor, or remove the full bag and replace it with empty one. • The compactors reduce the volume, the weight remains same. • The compacted volume 20 to 60% less of the original volume.
Composting • It is an effective way of reducing organic materials and altering physical composition of solid waste, at the same time producing useful by-product. • The impact of home composting on the volume of solid waste to be handled is very small.
Backyard Composting • It requires individual home owner develop some method of composting yard wastes(leaves and grass clippings and also brush, stumps, and wood) • The simplest backyard composting method involves placement of materials in a pile and watering and turning it to provide moisture and oxygen to the microorganisms within pile.
• Composting period upto a year, the material placed in the pile undergo bacterial and fungal decomposition until only humus material known as compost remains. • Composted materials, biologically stabilised can be used as mulching • Many prefabricated composting units are available. • Additives also available to enhance the composting process.
Lawn Mulching • Another type of composting involves leaving grass chippings from a newly mowed lawn where they were cut. • The gross chippings will be composted and incorporated into the humus.
Combustion • In the past, burning of combustible materials in fireplaces and burning of rubbish in backyard incinerators was common practice. • Backyard incineration is now banned. • Elimination of backyard burning increased the quantity of paper, cardboard and yard wastes collected. • Waste combustion is still in many parts of the world.
• Two types of combustors (incinerators) used for high-rise apartments. • In flue-fed type, wastes are charged through doors on each floor directly in to the refractory flue, the bottom of which opens directly into the top of the furnace combustion chamber. • In chute-fed type, wastes charged through hopper doors on each floor into metal chute and they in basement hopper. • Then the wastes either manually or mechanically transferred into the furnace.
Processing of Solid Waste at Commercial Facilities Compaction • The baling of waste cardboard at markets and other commercial establishments is common. • The bales vary in size, typically about 36 x 48 x 60 in. • Baled cardboard is reprocessed for production of packing materials or shipped overseas for remanufacture into variety of products.
Shredding and Hydropulping • Shredding used mostly in commercial establishments and by governmental agencies to destroy sensitive documents that are no longer of value. • Some cases, volume of wastes increased after shredding.
• Although Hydropulping system work well • They are expensive and discharge to local wastewater collection system. • Because the discharge of pulped material increases the organic loading on local treatment facilities.
Critical Evaluation of Options • In case of On-Site processing of solid wastes, there are more number of methods may be available. • But, one engineer should know to evaluate the various methods and should be able to pick up a better and better solution suitable to the local conditions. • Engineer should select and design the most sustainable and cost effective methods for a given community.
• The various factors that enters in, when deciding the best suitable method are: (a) System’s impact on local & global environment (b) Reliability (c) Safety to workers and to local community (d) Ease of operations (e) Efficiency (f) Economics & aesthetics (noise, odours, litter)
Public health & Aesthetics Aspects of On. Site Storage Public Health • Public health concerns areas used for the storage of solid waste with vermin and insects that serve as potential disease vectors. • The most effective control measure for both rats and flies is proper sanitation. • It involves the use of containers with lids, the periodic washing of the containers, storage areas and removal of biodegradable materials.
Aesthetics • Aesthetic considerations related to production of odours and unsightly conditions when adequate attention not given to maintenance. • Odours can be controlled through use of containers with lids and reasonable collection frequency. • If odour persist, sprayed with masking deodorant. • To maintain aesthetic conditions, the container should be scrubbed and washed periodically.