(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.
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.
i.e., the containers must be easily
manageable both for residents and
the containers must
be compatible with
health and safety, i.e., the containers should be securely covered and stored.
ownership, i.e., the municipal ownership must guarantee
compatibility with 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
in the frequency of collection;
in the dependence on residents to sort waste materials;
trend has, in fact, contributed to smaller crews in municipalities.
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.