Solid Waste Management: Collection Components

COLLECTION COMPONENTS  

(i) Collection points:  These affect such  collection system components as crew size and storage, which  ultimately control the cost of collection. Note that the collection points depend on locality and may be residential, commercial or industrial.  

(ii) Collection frequency: Climatic conditions and requirements of a locality as  well as  containers  and costs  determine  the collection  frequency.  In hot and humid climates, for  example, solid wastes must be collected at least twice a week, as  the decomposing solid wastes  produce bad odour and leachate. And,   as   residential   wastes usually   contain food wastes  and other putrescible  (rotting)  material,  frequent  collection  is desirable for  health  and  aesthetic  reasons.   Besides  climates,  the  quality  of  solid  waste  containers on  site  also  determines  the  collection frequency. For instance, while sealed or closed containers allow collection frequency up  to three days, open and unsealed containers  may require daily collection.   Collection efficiency  largely depends on the demography of the area (such as income groups, community, etc.), where  collection  takes  place.

cost, e.g., optimal collection frequency reduces the cost as it involves fewer trucks, employees and reduction in total route distance;  storage space, e.g., less frequent collection may require more storage space in the locality; sanitation,  e.g.,  frequent  collection  reduces concerns  about  health, safety and nuisance associated with stored refuse.  

(iii) Storage containers: Proper container selection can save collection energy, increase the speed of collection and reduce crew size. Most importantly, containers should be functional for the amount and type of materials and collection vehicles used. Containers should also  be  durable,  easy  to handle, and economical,  as well  as resistant  to corrosion,  weather and animals.  In  residential areas, where refuse is collected manually,  standardised  metal or plastic  containers  are typically required for waste  storage. When  mechanised  collection  systems are used,   containers   are specifically designed to  fit the  truck-mounted loading  mechanisms efficiency, i.e., the containers should help maximise the overall collection efficiency.

convenience, i.e.,  the containers must be easily manageable both for residents and

collection crew.

compatibility,  i.e.,  the  containers  must  be  compatible  with  collection equipment.

public health and safety, i.e., the containers should be securely covered and stored.

ownership,  i.e., the municipal  ownership  must guarantee  compatibility with collection

equipment.

(iv)Collection crew (see also Subsection 3.3.1): The optimum crew size for a community depends on labour and equipment costs, collection methods and route characteristics. The size of the collection crew also depends on the size and type of collection vehicle used, space between the houses, waste generation rate and collection frequency. For example, increase in waste generation rate and quantity of wastes collected per stop due to less frequent collection result in a bigger crew size. Note also that the collection vehicle could be a motorised vehicle, a pushcart or a trailer towed by a suitable prime mover (tractor, etc.). It is possible to adjust the ratio of collectors to collection vehicles such that the crew idle time is minimised. However, it is not easy to implement this measure, as it may result in an overlap in the crew collection and truck idle time. An effective collection crew size and proper workforce management can influence the productivity of the collection system. The crew size, in essence, can have a great effect on overall collection costs. However, with increase in collection costs, the trend in recent years is towards:

ü Decrease in the frequency of collection;

ü Increase in the dependence on residents to sort waste materials;

ü This trend has, in fact, contributed to smaller crews in municipalities.

Collection route: The collection programme must consider the route that is efficient for collection. An efficient routing of collection vehicles helps decrease costs by reducing the labour expended for collection. Proper planning of collection route also helps conserve energy and minimise working hours and vehicle fuel consumption. It is necessary therefore to develop detailed route configurations and collection schedules for the selected collection system. The size of each route, however, depends on the amount of waste collected  per stop,  distance between stops,  loading  time  and  traffic conditions. Barriers, such  as railroad, embankments, rivers and  roads  with  heavy  traffic, can be considered  to divide  route territories. Routing (network)  analyses and planning can: increase  the likelihood  of all  streets  being  serviced  equally and consistently; help supervisors locate or track crews quickly; provide optimal routes that can be tested against driver judgement and experience.

(vi)   Transfer station : A  transfer station is  an intermediate station  between final disposal option  and collection point  in order  to  increase  the efficiency of the system,  as  collection vehicles  and crew remain closer to routes. If the disposal site is far from  the collection area, it  is justifiable to have a transfer station, where smaller collection vehicles transfer their loads to larger vehicles, which then haul the waste long distances. In some instances, the transfer station serves as a pre- processing point, where wastes are dewatered, scooped or compressed. A centralised sorting and recovery of recyclable materials are also carried out at transfer stations (EPA, 1989). The unit cost of hauling solid wastes from a collection area to a transfer station and then to a disposal site decreases, as the size of the collection vehicle increases.