Chapter 8 Cllectin f Slid Waste Cllectin accunts fr 50-90% f the budget f a MSW management system! Cllectin f MSW Cllectin includes nt nly the gathering r picking up f SW frm varius surces, but als the hauling t the lcatin where the cntents f the cllectin vehicles are emptied. The unlading f cllectin vehicle is als cnsidered part f the cllectin peratin. Activities assciated with hauling and unlading are similar fr mst cllectin systems. Gathering r picking up f SW will vary with the characteristics f facilities, activities, r lcatins where wastes are generated and the methds used fr nsite strage f accumulated wastes between cllectins. 1
Cllectin f cmmingled MSW Curbside Cllectin (manual) Curbside Cllectin (mechanized) Frm lw-rise detached dwellings Types f residential cllectin services Curb in frnt f huse n the curb Alley ne r tw cntainers in the alley Setut-Setback frth and back t the huse Setut frth but nt back t the huse Manual methds Direct lifting and carrying f laded cntainers Rlling f laded cntainers Use f small lifts fr rlling laded cntainers 2
Frm lw-and medium-rise apartments Transprting the cntainer t the street fr curbside cllectin by manual r mechanical means Frm high-rise apartments Emptying mechanically using cllectin vehicles equipped with unlading mechanism Hauling t an ff-site lcatin Frm cmmercial-industrial facilities Bth manual and mechanical means Using mvable cntainers t large statinary cmpactrs Using large pen-tp cntainers T avid traffic cngestin during the day, slid wastes frm cmmercial establishments in many large cities are cllected in late evening and early mrning hurs. 3
Frm cmmercial-industrial facilities Using private haulers r city crew In sme cities, cardbard is bundled and left at curbside where its cllected separately. In large cmmercial facilities baling equipment may be used fr the paper and cardbard, and crushers are used fr the aluminum cans and plastics. Cllectin f separated MSW Waste materials that have been separated at the surce must be cllected r gathered tgether befre they can be recycled. The principal methds nw used fr the cllectin f these materials include curbside cllectin. Curbside Cllectin 4
Vechiles used fr separate cllectin Standard trucks Cmpactr trucks Mbile cntainer system Mdified flatbed truck Open-bin recycling truck Clsed-bdy recycling truck Cllectin System Types Hauled Cntainer System (HCS) Cntainer is mved t dispsal site Used fr cnstructin & demlitin waste High generatin rates (pen markets) One drive and frequent trips Statinary Cntainer System (SCS) Cntainer remains at site (residential and cmmercial) May be manually r mechanically laded Cntainer size and utilizatin are imprtant 5
Hauled Cntainer System (HCS) Ideally suited fr the remval f wastes frm surces where the rate f generatin is high The cntainer is picked up and hauled ff t the dispsal area where the cntainer is emptied and returned t the riginal lcatin (cnventinal mde). The cntainer is carried by the truck. A variatin (exchange cntainer mde) is start with an empty cntainer. HCS: Cnventinal mde 1 2 3 n Beginning f rute, t 1 End f rute, t 2 (Empty Vehicle) Transfer Statin r Dispsal Site 6
HCS: Cnventinal mde s Transfer Statin r Landfill A rund trip starting frm the time the truck arrives at a waste generatin site wuld be: pickup the cntainer, pc drive t the dispsal site with the used cntainer, h empty the cntainer at the dispsal site, s drive t the generatin site with the empty cntainer, h return the empty cntainer t the pickup lcatin in Step 1, uc drive t the next pickup lcatin with an empty truck (n cntainer), dbc HCS: Exchange cntainer mde 1 2 3 n Beginning f rute, t 1 (Vehicle with empty cntainer) End f rute, t 2 Transfer Statin r Dispsal Site 7
HCS: Exchange cntainer mde s Transfer Statin r Landfill A rund trip starting frm the time the truck leaves the dispsal site wuld be: drive t the pickup lcatin with an empty cntainer n truck, h unlad the empty cntainer, pickup the used cntainer, repsitin the empty cntainer, (uc+pc+zc) drive t the dispsal site, h empty the cntainer at the dispsal site, s Rund trip sequence is nw cmplete. After at-site time, vehicle will start the rund trip sequence again and drive t next site. Hauled Cntainer System (HCS) Advantages: Useful when generatin rate is high and cntainers are large May eliminate spillage assciated with multiple smaller cntainers Flexible. Need mre capacity, use a larger cntainer Disadvantage: If the cntainers are nt filled, lw utilizatin rate. 8
Statinary cntainer system (SCS) SCS can be used fr the cllectin f all types f wastes The waste cntainer remains in the vicinity f where the waste is generated. The waste is unladed int a bigger truck. A large cntainer is an integral part f the truck. When fully laded frm multiple waste cntainers, the truck travels t and frm the landfill as ppsed t the waste cntainer. Statinary cntainer system (SCS) Types: Manually laded: Small cntainers, residential pickup. Mechanically laded: Larger cntainers, wheeled residential pickup and cmmercial pickup Almst all vehicles cntain internal cmpactin equipment 9
Operatinal Sequence f SCS 1 2 3 n Beginning f rute, t 1 (Empty Vehicle) End f rute, t 2 Transfer Statin, MRF r Dispsal Site Statinary cntainer system (SCS) Advantages: Majr advantage is that vehicle des nt travel t dispsal area until it is full yielding higher utilizatin rates Disadvantages: System is nt flexible in terms f picking up bulky gds Wastes e.g. demlitin, that make damage the relatively delicate mechanisms Large vlume generatins may nt have rm fr string large cntainers 10
Analysis f Cllectin Systems T determine Capacity f vehicle # f vehicle required Crew size Labr required Length f wrkday/week Lk at: (divide cllectin int specific tasks) Pick up time Haul time At site time Off rute time Cntainer capacity,waste vlume generated Vehicle cmpactin factr Analysis f Cllectin Systems The activities invlved in the cllectin f slid wastes can be reslved int fur unit peratins 1. Pickup P HCS P SCS time spent driving t the next cntainer the time spent picking up the laded cntainer time required t re-depsit the cntainer after it has been emptied time spent lading the vehicle, beginning with the first cntainer and ending when the last cntainer has been laded 11
Analysis f Cllectin Systems 2. Haul (h) 3. At-site (s) HCS- The time required t reach the lcatin where the waste will be emptied SCS - The time required t reach the lcatin where the full vehicle will be emptied and cntinuing until the truck arrives at the lcatin The time spent at the site (landfill, transfer statin) where the system is unladed (including waiting time) 4. Off-Site (W) Nn-prductive activities (Check in, check ut, meeting, breaks) Typically 15% Cllectin Vehicles (avg. life 5-7 years) Side lader Frnt lader Rear lader 12
Cllectin Vehicles (avg. life 5-7 years) Crane truck fr igl cntainers Truck with tilt frame fr hauled cntainers Hist truck fr hauled cntainer Cllectin Rutes Path established by Trial and errr Cmputer Heuristic methds (cmmn sense) Steps Define cllectin area Assign dispsal sites if mre than ne Establish daily cllectin znes - cllectin area divided int sectins fr daily service established based n cmpacted vlume 13
Cllectin Rutes Steps Balance daily vehicle assignments (districting) Rute vehicles within daily districts Rules Lcatin maps with pertinent inf; surces, vlume, cntainers Layut preliminary rutes Begin and end near arterial streets Start at tp f hills Wrk tward dispsal site Wrk in cngested areas during nn-rush hurs Large quantities first Example 8.2 Determinatin f haul-speed cnstants The fllwing average speeds were btained fr varius rund-trip distances t a dispsal site. Find the hauled speed cntants a and b and the rund-trip haul time fr site that is lcated 11 mi away. Rund-trip distance (x), mi/trip Average haul speed (y), mi/h Ttal time (h=x/y), h 2 17 2/17=0.12 5 28 0.18 8 32 0.25 12 36 0.33 16 40 0.40 20 42 0.48 25 45 0.56 14
Travel time (h), h/trip 01-Mar-15 Example 8.2 Determinatin f haul-speed cnstants Slutin Plt x/y, which is the ttal haul travel time versus the rund-trip distance as shwn belw. 0.6 0.5 0.4 0.3 0.2 0.2 h/trip 10 mi/trip h = 0.08 + 0.02x slpe, b= 0.02 h/trip 0.1 a= 0.08 h/trip 0.0 0 5 10 15 20 25 30 Rund-trip haul distance (x), mi/trip The rund-trip haul time fr the site that is lcated 11 mi away. Rund-trip distance, x = 2 (11 mi/trip) = 22 mi/trip Rund-trip haul time, h = a + bx = 0.080 h/trip + (0.020 h/mi) (22 mi/trip) = 0.52 h/trip Example 8.3 Analysis f a hauled cntainer system Slid waste frm a new industrial park is t be cllected in large cntainers, sme f which will be used in cnjunctin with statinary cmpactrs. Based n traffic studies at similar parks, it is estimated that the average time t drive frm garage t the first cntainer lcatin (t1) and frm the last cntainer lcatin (t2) t the garage each day will be 15 and 20 min, respectively. If the average time required t drive between cntainers is 6 min and the ne-way distance t the dispsal site is 15.5 mi (speed limit: 55 mi/h), determine the number f cntainers that can be emptied per day, based n an 8-h wrkday. Assume the ff-rute factr, W, is equal t 0.15. 15
Example 8.3 Analysis f a hauled cntainer system Slutin Determine the pick-up time per trip: P hcs = pc + uc + dbc pc: time required t pick up laded cntainer, h/trip uc: time required t unladed empty cntainer, h/trip pc + uc = 0.4 h/trip (frm Table 8-5) dbc: time required t drive between cntainer lcatins, h/trip P hcs = pc + uc + dbc = 0.4 + 0.1 = 0.5 h/trip Determine the time per trip: T hcs = P hcs + s + a + bx S: at site time = 0.133 h/trip (frm Table 8-5) a = 0.016 h/trip b = 0.018 h/trip (frm Fig. 8-16) T hcs = 0.5 + 0.133 + 0.016 + 0.018(31) = 1.21 h/trip Determine the # f trips that can be made per day: N d = (H(1-W)-(t1+t2))/T hcs N d = (8h/d (1-0.15)-(0.25h+0.33h))/1.21 h/trip N d = 5.14 trip/d 5 trips/d Example 8.3 Analysis f a hauled cntainer system Figure 8-16 Crrelatin between haul speed and rund-trip haul distance fr waste cllectin vehicle 16