COMPOSITION, CHARACTERISTICS AND QUANTITIES
3.3.1 Need for Analysis
An analysis of the composition, characteristics and quantities of solid wastes is essential for the following reasons:
· It provides the basic data on which the management system is planned, designed and operated
· The changes/trend in composition and quantity of waste over a period of time are known which help in future planning
· It provides the information for the selection of equipment and appropriate technology
· It indicates the amount and type of material suitable for processing, recovery and recycling
· The forecast trends assist designers and manufacturers in the production of vehicles and equipment suitable for future needs.
For such information to be of the widest possible benefit it must be collected by a responsible national, regional or local authority and made available to all who require it.
3.3.2 Field Investigations
Field investigations are necessary for providing the basic data on solid wastes and are carried out in three ways:
· Weighing of vehicles at disposal sites
· Sorting of wastes into predetermined components for weighing and sampling in order to determine the percentage of each component and the physical and chemical characteristics of the wastes.
· Visiting institutional and industrial sites to identify wastes being generated and disposal methods being used.
The weighing of loaded and unloaded vehicles is accomplished with a weighing scale or weighbridge with a capacity of 20,000 kg. The loaded vehicles are weighed when they enter the disposal site and empty vehicles are weighed when they leave the site after unloading. Weighing is carried out each day of weighing period in order to determine the average weight. Ideally the weighing scale should be operated during the entire daily period of operation of the landfill site, round the clock, if necessary. A shift system should be employed, the weighing team comprising four workers for each scale – a supervisor, an assistant and two helpers moving the scale platform to the desired spacing for each vehicle.
The quantities of waste measured at disposal sites more correctly reflect the quantities being disposed rather than those generated since the measurements do not include:
· Waste salvaged at the site of generation
· Waste disposed of in unauthorised places-empty lots, alleys, ditches etc.
· Waste salvaged by collectors
· Waste salvaged at the disposal site
Differences between the two are insignificant with well-managed collection systems, enlightened public attitude and strict enforcement of legislation. This is frequently not the case, particularly in some cities and it is then necessary to measure waste quantities at source. Flintoff (1984) describes a method for collecting samples with the active cooperation of householders wherein containers or plastic bags are filled by a representative number of householders and labeled before being taken to the depot where the contents are weighed and the volume measured.
Sorting is carried out manually, each sample size being about 100-150 kg for desired accuracy of analysis. This process separates the waste into predetermined components, each component being separately weighed. Equipment
used for this purpose includes:
· A sorting table, 3m long x 1.5m wide
· A measuring box, 1m long x 0.5m wide x 1m high
· Bins or boxes for storage of about 60 litre i.e. 0.06 m3 capacity sorted material
· A platform weighing machine – 500 Kg
This procedure may not be feasible in developing countries where time for study and resources are limited. For such situations a suitable procedure of sample collection is described.
