The process of waste collection should be thought as a multiphase process. In developed country at least 5 separated phase. How many do you think in Bandung? Indonesia? 1
1 2 3 4 5 House to storage Truck to disposal Truck from Truck routing Storage to truck house to house Personal convenience Tax fund to operate the SW collection Volume based system or weight based fee system. Which one if more effective to reduce waste? Hint: what about a family has a home compactor? 2
A family of 4 people generates solid waste at a rate 1 kg/cap/day and the bulk density of refuse is 120 kg/m3. If collection is once a week, how many of 120 l garbage cans will they need? If they had a home compactor, how many of 120 L garbage cans will they need, if each block of compacted refuse is 840 kg/m 3. Think: how people can cheat on volume based fee Backyard or curbside collection? What are the differences and drawback? Truck to collect: rear loaded and compactor called packers (12-15 m 3 ) The most dangerous work in the world 3
Refuse is compacted as the truck moves from house to house. The higher the compaction ration, the more refuse can be carried by the truck. Backyard collection need more crews than curbside collection. Fully automatic system needs only one crew. For curbside collection, three crew do not collect three times as much refuse as one person crew. Each households produces 28 kg of refuse per week. How many households can be collected if a truck has a capacity 20 m3 and can compact refuse to 300 kg/m3, before the truck has to make a trip to landfill? 4
Total distance travel is minimizes Total cost is minimized Avoid deadheading Basic principles of Euler to solve the routing problems: All points are connected (one must be able to get from one place to another) The number of link to any node must be of an even number Macro-routing: the most direct road from the end of route to the disposal site Objective : to minimize the objective function subject to constraint. (LP is the most common technique) 5
1,2,3,4 collection route centroid point 4 1 2 Disposal site1 3 Disposal site2 The waste generated at four sources (4 centroid of collection area), The refuse will be allocated to 2 disposal sites. The objective is to minimize the cost. However several requirements must be met: The capacity of disposal sites are limites The amount of refuse disposed of must be equal o the amount generated. The collection route centroids cannot act as disposal sites, or the total amount of refuse hauled from each collection area must be greater than or equal to zero Total cost equals hauling cost plus disposal cost. 6
The objective function: N K K N x ik c ik + F k x ik i=1 k=1 k=1 i=1 Subject to the following constraints N Constraint 1: i=1 x ik B k for all K K Constraint 2: k=1 x ik =W i for all I Constraint 3: x ik 0 for all i, k Where: x ik = quantity of waste hauled from source i to disposal site k, per unit time C ik =cost per quantity of hauling the waste from source i to disposal site k F k = disposal cost per waste quantity at disposal site k (capital plus operating) B k = capacity of disposal site k, in waste quantity per unit time W i =total quantity of waste generated at source i, per unit time N= number of source i K= number of disposal site k 7
What is the current system in Bandung or n Indonesia? Current waste management system 8
1 2 3 4 5 House to storage Storage to handcart Handcart from house to house Handcart to TPS 1 2 Truck routing (macro-routing) Truck to disposal 9
Working day is not efficient Truck capacity is not efficient Truck routing is not efficient Crews behavior (delay and fatigue) Accessibility is limited To estimate the time requirement of waste collection system in order to evaluate ad subsequently optimize the system Steps for conducting a time study: 1. select crews representative of average level and skill level 2. Determine the best method (series of movement) for conducting the work 3. Set up the data sheets which contains: date, name of the crew, time recorder, type of collection method, equipment loading mechanism), specific area, distance between collection point 4. Divide the loading activity into elements that appropriate for the type of collection service, e.g time to travel from last loading point to next one; time t get out of vehicle and carry container to loading area; time to load to vehicle; time to return the container to the collection point and return to the vehicle 5. Using stopwatch to record the time required to complete each element 6. Determined the average time recorded (T0) and adjust it to normal condition. Tn=To x (1+(F+D/100) 10
Davis, M.L., Cornwell, D.A., Introduction to Environmental Engineering, MCGraw Hill, 2013 Worrel, W.A., Vesilind, P.A., Solid Waste Engineering, Cengate Learning, 2012 Sembiring,E., Nitivattananon, V., 2009, Model Formulation for preliminary decision making tool for a regional waste management in developing countries. Proceeding SIBE 11