A Model for Optimal Operation and Design of Solid Waste Transfer Stations

Abstract

At a transfer station arriving trucks dump collected refuse, and larger capacity trucks haul the refuse to a final disposal point. Transfer of refuse from collection to haul trucks is direct at some such facilities, while at others a storage area serves as a buffer into which refuse is dumped and from which it is loaded for shipment. A (single) deterministic queuing model is formulated for idealized forms of both direct and indirect transfer. The model takes into account a time-dependent arrival rate of refuse, the number of haul trucks, the hauling time, the number of collection loads per haul load, the storage capacity, numbers of dumping and loading channels, and dumping and loading times. Arrivals and departures of both types of vehicles are treated as fluid flows. Mathematical relations that describe physical behavior are derived, and interpreted graphically. Quantities represented graphically include storage level, and queues and delays of both kinds of vehicles. Optimal haul schedules are obtained for “typical” examples. The San Francisco (indirect) and Orange County (direct) transfer stations are discussed, based on direct observation. The model is applied directly to the former facility; a variation of the model is outlined for the latter.