8 Waste collection – Collection routing and crew

Dr. Yogalakshmi K. N

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Objectives:

 

1.      To understand the routing mechanism involved in waste collection

 

2.      To study in detail about the waste collection crew organization and their operation mechanism

 

3.      To calculate the waste collection time and number of vehicles used in waste collection

 

1.0 Introduction

 

Waste is defined as any unwanted or unusable substance that is discarded after primary use. Wastes are normally generated as a result of human and animal activities. Urbanization and rapid advancements in industrialization has led to an increase in the production and consumption processes resulting in the generation of wastes from various sectors that include agricultural, commercial, domestic, industrial, institutional, social and from community activities. Over time, these wastes accumulate and can have real impacts on the health and the environment. Waste management is the only solution intended to reduce adverse effects of waste on health, the environment or aesthetics.

 

Management of solid waste is crucial to avoid environmental and health hazards. Solid waste management is highly complex as it involves different steps, technologies and public participation. The steps involved in solid waste management include reduction in waste generation, handling, storage, collection, segregation, transfer, transport, processing, treatment and disposal. The success of waste management depends on the public and the government. Both share equal responsibilities and they should work hand in hand to achieve proper waste management.

 

Waste collection is the major and crucial step in waste management process. It is defined as the collection or gathering of waste from the source of generation and haul them to the transfer stations, processing sites, disposal site or landfills. Hence, waste collection does not mean the gathering of waste alone. Waste collection differs for comingled and source separated wastes. Source separated wastes (i.e) biodegradables, recyclables and non-recyclables are collected separately from different collection centres or containers and taken for further processing. Likewise, the comingled waste is carried to transfer station for further separation and processing. Waste collection is most difficult and complex in an urban environment because the generation of residential, commercial-industrial solid waste including recyclables takes place in every home, apartment building, commercial and industrial facility, and in the streets, parks, and even vacant areas. Henceforth, the waste collection becomes complex with increasing waste quantity and diffused waste generation pattern. More diffuse is the waste collection, more is waste generation and more complex is waste collection. Waste collection is costly component of waste management. Around 50 to 70 percent of the total waste management cost is utilized for waste collection. The cost can be reduced if the waste collection is properly planned and managed. Waste collection depends on number of containers, collection vehicles, routes and collection frequency. In the previous modules, the various elements in waste management was outlined with a special emphasis on waste collection and its components. Storage container characteristics, types of waste containers, their location, waste collection vehicles, types of waste collection systems were also discussed. In this module we shall discuss about the collection frequency, collection routing and collection crew.

 

3.0 Collection frequency

 

The rate at which the waste is collected from a collection area is called as collection frequency. Collection frequency depends on many factors such as population, community, income group, life style and climatic conditions. In a hot humid climate, the waste collection must be frequent as this climate favor microbial activity resulting in faster decomposition of solid wastes. It also produces bad odour/ foul smell and leachate (a watery liquid that oozes out from the waste). Henceforth this climate necessitates collection at least twice or thrice a week. This is applicable for putrescible material too. Frequent collection of putrescible waste will avoid health problems. Requirements of a locality is another factor that determines the collection frequency. Residential area requires frequent collection unlike the shops, institutions and industries. Likewise, urban area generates more waste than rural areas and hence require frequent collection.

 

Income group and life style also plays a major role in determining the frequency of waste collection. The average waste collection frequency or rate of waste collection is directly proportional to income levels. According to reports, low-income countries showed low collection rates (i.e) around 41%, while high-income countries showed 98% waste collection. High income groups tend to waste lot of materials such as food, clothes, furniture and other used materials. Income favors them to buy, replace new materials and dispose off the old one. Thus, the waste collection rates should be more frequent. This very unlikely of a low-income group. Likewise, the packaging waste generation is also too high in high income groups. The waste collection frequency varies with region too. Africa and south Asian countries showed a collection frequency of 46% and 65%. However, OECD countries showed 98% collection frequency.

 

Collection frequency directly or indirectly is connected to the health of the workers and residents. The potential exposure of householders and waste collectors to health risks is higher when the waste is collected at extended frequencies. According to reports, wastes stored for longer period of time in open bins, favored the growth of mites, maggots and bacteria. The decomposition of waste by these organisms released endotoxins which when inhaled might cause lung inflammation.

 

The requirement of containers too determines the collection frequency. According to the population and quantity of waste generation the number of containers should also be increased. Apparently open containers necessitate waste collection on daily basis unlike the sealed containers. Inappropriate estimation of waste generation and irregular waste collection increases the overall cost of the collection. Proper planning and segregation of waste at source will minimize the cost involved in waste collection.

 

Table 1 summarizes the advantages and disadvantages associated with less and more collection frequency.

 

Table Advantages and disadvantages of collection frequency

 

 

3.0 Collection route

 

The route planned by collection crew to collect waste in a specific area is called as collection routing. A proper planning of the collection routes will decrease the overall cost in addition to labour cost, conserve energy by minimizing vehicle fuel consumption and reduce the working hours. The size of each route is decided based on

 

•      the amount of waste collected per stop,

•      distance between stops,

•      loading time

•      traffic conditions.

•      Barriers, such as railroad, embankments, rivers and roads with heavy traffic, can be considered to divide route territories.

 

All these factors determine the collection routing. Proper planning will improve efficiency of collection and decrease the collection cost. It will also help the supervisor to track the collection crew.

 

The success of waste collection depends upon the collection crew and equipment requirement. Once collection crew is formed, it is essential for a solid waste manager to lay down the collection route. Improper routing results in ineffective waste collection. The collection route is laid after several trials of motion time experiments. The collection routing is heuristic process as it does not involve any standard or universal set of rules. The routes are prepared by relatively simple approach that defines the specific pattern of routing. A route map should illustrate the collection points, garbage service location, one way- two-way streets, location of processing and disposal sites, natural barriers and traffic congested areas.

 

3.1 Guidelines for laying out collection route

  • Details of the amount of waste generation, collection points, frequency of collection, crew size and vehicle type must be identified and coordinated.
  • Routes should be laid out in such a way that they begin an end near arterial streets. The physical barriers such as railway tracks, bridges, river and embankments should be taken as route boundaries.
  • The routes should neither be fragmented nor overlapping. They should be compact and show clustered street segment of a particular area.
  • In hilly terrain, the routing should begin at the top and proceed downhill. This is due to the fact that the vehicle becomes loaded and is difficult to be taken uphill when the reverse pattern is followed. It also conserves fuel.
  • The pattern of routing should be such that the last point of waste generation should be located near the disposal site.
  • Areas suffering from heavy traffic congestion should be visited during the early hours of the day to avoid rush. Likewise, areas generating large quantity of waste should be visited during the first part of the day.
  • One-way streets should begin at the upper end of the street and end in down street through the looping process. Dead end streets can be serviced at T- junctions i.e. intersecting segments.
  • Collections involving both sites of the streets require long straight path before anticlockwise turning.
  • One sided collection can be routed with many anticlockwise turns around the blocks.
  • Scattered pick up points with small quantity of waste generation should be attended in one trip on the same day.

The steps involved in establishing collection routes include

  • Preparation of maps showing the point of waste generation
  • Preparation of information summary table
  • Preliminary route lay out
  • Development of balance routes after trials

 

Once the routes are laid down on the paper, they are given to the collection crew for implementation. Further with field experience, the route is modified and entered into the database as a new route. A schedule is prepared for each route with details of location and sequence of pick up points and is provided to the collection crew. Every truck driver should maintain a route book which he uses to check the location and record the problems associated with the same. The information recorded will be used in modifying the collection route.

 

Motion time measurement is a standard procedure to develop solid waste collection system. It’s a technique by which the time taken for the movement of the collection crew is estimated with the help of stop watches. The results such as time, distance and number of containers are tabulated to identify the best series of activities that the collection crew must follow to collect the waste in the shortest possible time. Motion time measurement also helps us in determining the beast equipment to achieve good output and reduce various health problems. In recent times the motion time measurement studies involve the usage of video cameras at different collection points to study the movement of the collection crew. This is mainly done to make the collection crew conscious and complete the work within the stipulated time. It also improves the credibility of the crew. Many developed countries use geographical system to identify the location of the crew. This will improve the performance of the collection crew.

 

3.2 Types of collection vehicle routing

 

There are three types of collection routing

 

1. Macro routing: It’s the process by which total area is divided into routes in a way that represents single day collection of each group. The amount of waste collected per point distance between point loading and unloading time and traffic conditions determine the size of the route. Barriers like rivers, roads, railway tracks and traffic signals to divide into territories. Since macro routing balances the size and shape of route area within the limits imposed by the barrier. They are also referred as route balancing.

Table 1 Motion Time Measurement Study: Determination of Time, Distance and Number on Containers in Collection Route

 

2. Micro routing: The specific path covered by each crew and collection vehicle per day is defined as micro routing. Micro routing is laid out based on the results of micro routing.
3. Districting: When area is large enough, it is impossible for one institution to collect per day the waste generation. To facilitate efficient waste collection, the area is divided into smaller sections (Example of districting, routing of metropolitan cities).

 

4.0 Collection crew

 

The persons involved in collecting the waste from house to house; trucks and taking it to the transfer station or disposal site is termed as ‘collection crew’. The crew consists of 8-12 persons and is headed by the supervisor. The size of the crew varies from community to community, region to region, amount of waste generation in a locality/ waste generation rate, frequency of waste collection, collection methods involved, space between the houses, size and type of collection vehicle and route characteristics. Labour and equipment costs also determine the crew size. The crew size increases when there is increase in the rate of waste generation. Less collection frequency also increases the crew size because the quantum of waste per individual stop will be high. The crew size has a great effect on collection costs which leads to

  • Improper collection frequency
  • Segregation of material at source
  • Implementation of automation in collection

 

5.0 Cost involved in waste collection

 

As mentioned earlier, 60- 70% of the cost involved in total waste management is covered by waste collection. Cost of storage containers, collection vehicle, labour charges of collection crew contribute to total cost of waste collection. To be specific, labour charges depend upon the crew size, service time, travel time and discharge time. However, the cost of labour varies from large cities to small town. In large cities, with narrow lanes and heavy traffic congestion, the collection vehicles require minimum of four persons per vehicle to manually collect the waste, which adds to the cost of labour. On the contrary, the small town with less vehicle congestion and more space, vehicle with one person is sufficiently enough to handle the waste. Thereby reducing the cost of collection. Mechanically loaded System involving one person per crew is considered to be cost effective. Maintenance of storage containers, collection vehicles, compactors also add to the cost of collection. The collection cost also varies for co-mingled and source separated waste.

 

6.0 Analysis of collection time:

 

The        collection         time can         be         calculated         as        per         the        formula         given         below

 

Y = a + b + c(d) + e + f + g

 

Where:

 

Y   =      total collection time

a   =   garage to route time

b   =   actual time collecting waste

c   =   number of trips to disposal site

d   =   time to drive fully loaded truck to disposal facility, unload and return to collection area

e   =   time to drive to garage at the end of the trip

f   =   official breaks, including bathroom visits

g  =   other lost time such as traffic jams, breakdowns

f + g    =       off route time, usually a fraction of Y

a, d, and e are a function of distance and speed

b is a function of the number of customers, time per customer, number of loads (full or partial)

c is a function of the capacity of the vehicle and its compaction ratio

 

Likewise the number of vehicles required for collecting waste from a specific area is calculated as per the formula

 

N = SF/XW

 

Where

N = number of vehicles required
S = total number of customers served per week
F = collection frequency
X = number of customers truck can serve per day
W = number of work days per week

 

7.0 Management of collection system

 

The main objective of managing the collection system includes: protection of public health and maintain cost effective services. The management of the collection system can be done by both private and public entities. The advantage of a private entity is, it rarely faces monetary problems. It is capable enough to bear the expenses related to purchase of containers and collection vehicles. Moreover, in private entities, the labour charges are well taken care of in addition to the flexibility in maintaining the collection crew. In India, the private entities are generally authorized by the government through franchise of service agreement. The significant role is also played by the public entity/ government. In countries where both public and private entities work hand in hand, the efficiency of waste collection system increases.

 

8.0 Summary

  • To summarize, in this module we have familiarized about
  • Collection frequency and the factors influencing them
  • Collection routing mechanism, guideline and steps involved
  • Calculating the collection time and number of vehicles used for waste collection Collection crew
  • Cost of waste collection along with the management options

 

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References