Physical Characteristics - Density
3.3.7.1 Density
A knowledge of the density of a waste i.e. its mass per unit volume (kg/m3) is essential for the design of all elements of the solid waste management system
viz. Community storage, transportation and disposal. For example, in highincome countries, considerable benefit is derived through the use of compaction
vehicles on collection routes, because the waste is typically of low density. A reduction of volume of 75% is frequently achieved with normal compaction
equipment, so that an initial density of 100 kg/m3 will readily be increased to 400 kg/m3. In other words, the vehicle would haul four times the weight of waste in the compacted state than when the waste is uncompacted. The situation in low-income countries is quite different: a high initial density of waste precludes the achievement of high compaction ratio. Consequently, compaction vehicles offer little or no advantage and are not cost-effective.
Significant changes in density occur spontaneously as the waste moves from source to disposal, as a result of scavenging, handling, wetting and drying by
the weather, vibration in the collection vehicles. The values shown in Table 3.8 reflect densities at the pick-up point.
Table 3.8 : Density of Municipal Solid Wastes in Some Cities
Sl.No. City Density
(Kg/m3)
1. Bangalore 390
2. Baroda 457
3. Delhi 422
4. Hyderabad 369
5. Jaipur 537
6. Jabalpur 395
7. Raipur 405
Source : Solid Waste Management in Developing Countries INSIDOC, 1983
N.B.: The above figures may be taken as indicative and actual field measurements must be made while designing solid waste management schemes for towns and cities.
Density is as critical in the design of a sanitary landfill as it is for the storage, collection and transportation of waste. Efficient operation of a landfill requires compaction of the waste to optimum density after it is placed.
Bulk Density Measurement
Materials and apparatus:
· Wooden box of l m3 capacity
· Wooden box of 0.028 m3 capacity
· Spring balance weighing upto 50 kg.
Procedure: The solid waste should be taken in the smaller 0.028 m3 box to give a composite sample, from different parts of the heap of waste, then weighed with the help of a spring balance. After weighing, this smaller box (0.028 m3) is emptied in bigger l m3 box and the weight of the waste poured into the bigger box is noted. This is repeated till the larger box is filled to the top. The waste should not be
compacted by pressure. Fill the l m3 box three times and take the average. Thus the weight per cubic meter is obtained.
