waste handling and separation, storage, and processing at the source chapter 7 waste handling and...

Waste Handling and Separation , Storage, and Processing at the Source

Chapter 7

Presentation Outline

Introduction

Handling and Separation of Solid Waste at the Source

Waste Handling and Separation at the Residential Dwellings

Waste Handling and Separation at the Commercial and Industrial Facilities

Storage of Solid Waste at the Source

Processing of Solid Wastes at Residential Dwellings

Processing of Solid Wastes at Commercial and Industrial Facilities

Introduction

The handling and separation, storage , and processing of solid wastes at the source before they are collected is the second of the six functional elements in the solid waste management system.

because this element can have a significant effect on the characteristics on the waste, on subsequent functional elements, on public health, and on public attitudes concerning the operation of the waste management system, it is important to understand what this elements involves.

Handling and Separation of SW at the Source

Waste Handling

In general, Handling refers to the activities associated with managing solid wastes until they are placed in the containers used for their storage before collection or return to drop-off and recycling centers.

The specific activities associated with handling waste materials at the source of generation will vary depending on: Types of waste materials that are separated for reuse and

recycling The extent to which these materials are separated from

the waste stream Type of collection service where handling may also be

required to move the loaded containers to the collection point and to return the empty containers to the point where they are stored between collections.

Handling and Separation of SW at the Source

Separation for Recycling

The separation of solid waste components ( waste paper, cardboard, cans, glasses and plastic containers) at the source of generation is one of the most positive and effective ways to achieve the recovery and reuse of materials.

Some homeowners store the separated components within the home, periodically transferring the accumulated wastes to larger containers used for the storage of these materials between collection

other homeowners prefer to take separated waste components and place them directly in the containers used for the storage of these materials.

Waste Handling and Separation at Residential Dwellings

The three classifications most often used for the residential dwellings are:

Low rise ( under four stories)o single – family detached o single family attached o multifamily

Medium rise ( from four to seven stories) High rise ( over seven stories)

Because of the significant differences in the solid waste handling operations for the low-rise dwellings and medium – and high –rise apartments, each is considered separately in the following discussion.


At Low – Rise Detached Dwellings The residents or tenants under this category are responsible for

placing the solid wastes and recyclable materials that are generated in and around their dwellings in storage containers.

In some collection systems, mixed wastes are placed in a variety of storage containers with little or no standardization. In other systems, mixed wastes are placed in large 90 –gal containers equipped with wheels. In both of these systems, the homeowners are responsible for transporting the containers filled with wastes to the street curb for collection.


At Low – and Medium – Rise Apartment

Handling methods in most low and medium rise apartment buildings resemble these used for low-rise dwellings, but methods may vary somewhat depending on the waste storage location and collection method.

Typical solid waste storage locations include: Basement Storage Outdoor Storage Compactor Storage

Different types of non-recycling and recycling waste handling and separation for low and medium rise apartment buildings are delineated in Table 7-3.


Basement storage/Curbside Collection Curbside collection service is common for most low-and medium –

rise apartments.

Where curbside collection is used, the building owner provides a basement storage room or area for the storage of solid waste. Typically, the containers used for recycling are located within or next to the solid waste storage area

Residents carry their waste and recyclable materials to the storage area and deposit them in the appropriate containers.

The maintenance staff is responsible for transporting the containers to the street for curbside collection. Alternatively, in many apartments the maintenance staff is responsible for the collection of wastes and recyclable materials left out-side of the doorway to the apartment or from a utility room located on each floor.


Outdoor Storage / Mechanized Collection Large waste storage containers are located outdoors in

special closures.

The large containers are emptied mechanically using collection vehicles equipped with unloading mechanisms.

The containers used for recycling are located within the outdoor storage area or next to the waste storage area.

Residents carry their waste and recyclable materials to the storage area and deposit them in the appropriate containers. If needed, the maintenance staff is responsible for moving the containers to the collection point.


At High- Rise Apartments

In high –rise apartment buildings the most common methods of handling solid wastes involves one or more of the following:

Wastes are picked up by building maintenance personnel from the various floors and taken to the basement or service area

Wastes are taken to the basements or service area by tenants

Wastes, usually bagged, are placed by the tenants in specially designed vertical chutes with openings located on each floor. Wastes discharged in chutes are collected in large containers, compacted into large containers or baled directly. The entrance to the waste chute is usually located in the service area

Recyclable materials may be put outside in the hall or entry way for pickup.



Bulky items are usually taken to the service area by tenants or the building maintenance crew

In many cases, solid waste chutes are used in conjunction with large compactors. The building maintenance personnel are responsible for handling the compressed wastes and any other waste or recyclable materials that tenants bring to the service area

Chutes for use in apartment buildings are available in diameter from 12 to 36 in. The most common chute diameter is 24 in.

All the available chutes can be furnished with suitable intake doors, either side – bottom-hinged, for installation on various floor levels



Draft baffles at the intake doors, door locks, sprinklers, disinfection systems, sound insulation, and roof vents are among the many accessories that are available.

The use of a disinfecting and sanitizing unit is recommended because the cleanliness of the chute and the absence of odors generally depend to a large extent on their use.

In designing chutes for high rise apartment, one must consider variations in the rate at which solid waste are discharged.

In sizing chutes it is common to assume that The bulk specific weight of the solid waste equals 175 lb/yd3 All the daily wastes will be discharged within a 4-h period between 1 and 2 lb of wastes will be generated by each tenant

each day



In some of the more recently constructed apartment buildings, underground pneumatic transport systems have been used in conjunction with individual apartment chutes.

The underground pneumatic systems transport waste from the chute discharge points to centralized processing facilities. Both air pressure and vacuum transport systems have been used in this application.

Waste Handling and Separation at Commercial and Industrial Facilities

Commercial Facilities In most office and commercial buildings, solid wastes that

accumulate in individual offices or work locations are collected in relatively large container mounted on rollers.

Once filled, these containers are removed by means of the service elevator and emptied into Large storage containers Compactors used in conjunction with the storage containers Stationary compactors that can compress the material into

bales or into specially designed containers Other processing equipment. because many older large

office and commercial buildings were designed without adequate provision for onsite storage of solid wastes and recyclable materials, the storage and processing equipment now used is often inadequate due to space limitations and tends to create handling problems

Waste Handling and Separation at Commercial and Industrial Facilities

Industrial Facilities The handling and separation of nonindustrial solid wastes at

industrial facilities is essentially the same as for commercial facilities. Because the handling of industrial wastes is industry and site specific, few generalization are possible.


Factors that must be considered in the onsite storage of solid wastes include: The effect of storage on the wastes components The type of container to be used Container location Public health and aesthetic


The effect of storage on the wastes components Microbiological Decomposition

Food and other wastes placed in onsite storage containers will start to undergo microbiological decomposition as a result of the growth of bacteria and fungi

If waste are allowed to remain in storage containers for extended periods of time, flies can start to breed and odorous compounds can develop

Absorption of Fluids Because the components that comprise solid wastes have

differing initial moisture content, re-equilibration takes place as waste are stored onsite in containers (e.g., Paper will absorb moisture from food waste).

The degree of absorption depends on the length of time the wastes are stored until collection and the rainfall


The effect of storage on the wastes components Contamination of waste components

The major waste components may be contaminated by small amount of wastes such as motor oil, household cleaners and paint.

The effect of this contamination is to reduce the value of individual components for recycling

While the contamination that occurs during onsite storage decreases the value of the individual waste components, one can also argue that this contamination is beneficial with respect to the disposal of these wastes in a landfill. The concentration of the individual contaminations are reduced considerably when the contaminated waste components are spread out and compacted for land filling.


Types of Containers To a large extent, the types and capacities of the containers

used depend on the • characteristics and types of wastes to be collected, • the types of collection system in use, • the collection frequency, and • the space available for the placement of containers

Data on the types and sizes of containers used for onsite storage of solid wastes is summarized in Table 7-4

Typical applications and limitation of containers used for the onsite storage of solid wastes are summarized in Table 7-5.


Low – Rise Dwellings with Manual Curbside Waste Collection Service

Because solid wastes are collected manually at curbside for most low –rise detached residential dwellings, the containers should be light enough to be handled easily by one collector when they are full.

The 30-gal galvanized metal or plastic container has proved to be least expensive means of storage for low-rise dwellings

Galvanized Metals

Noisy when emptied and can be damaged

Plastic Containers

Tend to crack due UV rays and Freezing temperature


Low – Rise Dwellings with Manual Curbside Waste Collection Service

With the widespread availability of paper and plastic products, the use of container liner is now common. A disadvantage in the use of liners is that if the waste are to be separated by component, or if they are to be combusted, it is necessary to break up the liners bags in a preprocessing step.

The use of liners may be a convenience for the homeowner, liners may not be ideal from the standpoint of material recovery and recycling.


Low – Rise Dwellings with Mechanized Curbside Waste Collection Service

Mechanical collection systems for residential services is increasing as labor and insurance premium costs rise. The containers used for the onsite storage of waste is an integral part of the collection system.

Low and Medium Rise Apartments

The two most common types are individual plastic or galvanized metal containers and large portable or fixed containers.


High – Rise Apartments

The most common means of storage for wastes accumulated from the individual apartments include

1. enclosed storage containers or disposable bags used in conjunction with compaction equipment

2. Large open top containers for un compacted wastes, bulky items and white goods

3. Large open top containers for recycled materials

Commercial Facilities

The types of containers depend on Method used for collecting the waste produced The available space


Container Storage Locations

Container storage locations depend on the type of dwelling or commercial and industrial facilities and the available space and access to the collection services

Residential Dwellings

Low rise dwellings at the sides or rear of

the house In alleys In or next to the

garage

Low – and medium rise apartment buildings In the basement of

the buildings Outdoor storage

High rise apartment In the basement of

the buildings


Container Storage Locations

Commercial and Industrial facilities The sitting of containers at existing commercial and industrial

facilities depends on both the location of available space and service access conditions.

Public Health and Aesthetic Public heath concerns are related primarily to the infestation

of areas used for the storage of solid waste with vermin and insects that often serve as potential disease vectors.

Proper sanitation involves• the use of containers with tight lids • the periodic washing of containers and storage area • the periodic removal of biodegradable materials

Processing of Solid Waste At Residential Dwellings

Waste processing is used to reduce the volume recover reusable materials alter the physical form of the solid waste

Typical onsite processing operations and facilities are listed by source in Table 7-6


Grinding of Food Waste Because the organic material added to the wastewater has

resulted in overloading many treatment facilities, it has been necessary in some communities to forbid the installation of waste food grinders in new developments until additional treatment capacity become available

Separation of wastes one of the most effective ways to achieve the recovery and reuse

of materials. Where the remaining wastes are to be combusted, the question that must be answered is, what is the energy content of residual solid waste

See example 7-3


Compaction the two principal types of compactor used for the processing of

wastes at residential dwellings are Small (individual) home and apartment compaction units Large compactors used to compact waste from a large

number of apartments

The effect of the use of home compactor on the volume of wastes collected is illustrated in example 7-4

the use of home compactors may also be counterproductive from stand point of subsequent processing operations

For example, if the wastes are to be separated mechanically into components at MRF, the compacted wastes will have to be broken up again before sorting. Also, by compacting, the wastes may become so saturated with the liquids present in the food wastes that the recovery of paper or other components may not be feasible because product specification may not be met


Compactors for large Apartment Buildings Typically, a compactor is installed at the bottom of the solid

waste chutes ( See fig 7-13)

Wastes falling through the chutes activate the compactor by means of photoelectric cells or limit switches. Once these switches are activated, the wastes are compressed. Depending on the design of the compactor, the compressed wastes may be formed in bales or extruded and loaded automatically into metal containers or paper bags.

where solid waste incinerators are used, the compacted wastes must be broken up to avoid delayed combustion in the furnace and high losses of unburned combustible materials. All these factors must be considered when the use of onsite compactors is being evaluated.


Composting it is an effective way of reducing the volume and altering the

physical composition of solid wastes while at the same time producing a useful by-product

Combustion the choice between the two types of combustors used for high –rise apartment depends on the method of charging flue-fed and chute – fed.

in the flue –fed type, waste are charged through doors on each floor directly into refractory flue, the bottom of which opens directly into the top of the furnace combustion chamber.

In the chute – fed type, wastes are charged through hopper doors on each floor into a metal chute and they collect in a basement hopper. The wastes are then either manually or mechanically transferred into the furnace

Processing of Solid Waste At Commercial and Industrial Facilities

Onsite processing operations carried out at commercial – industrial facilities are generally similar to those described for residential sources. However, compaction is very important in commercial facilities.

Compaction, Shredding and Hydropulping are commonly used as means of processing of solid wastes at commercial and industrial facilities

waste handling and separation, storage, and processing at the source chapter 7 waste handling and...

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