In the case of mixed waste processing, bulky items (appliances, furniture, etc.) and specified contaminants (e.g., hazardous waste) generated in some of the industrialising economies can be, and oftentimes are, manually removed from the waste prior to mechanical processing. With few exceptions, a completely manual separation of materials from mixed waste beyond this initial separation is reserved for small operations, i.e., less than 20 Mg/day. Manual separation is also applicable to the removal of contaminants from source-separated materials. (Here, “contaminants” refers to components other than the materials specified for separate collection.)
Ranges of sorting rates and of recovery efficiencies can be established that cover the usual set of operating conditions at processing facilities. Ranges for selected material categories are presented in Table VI-1.Equipment involved in manual separation of materials usually includes a sorting belt or table, which contains a mixture of materials. Workers (“sorters”) are stationed on one or both sides of the belt or table. Hoppers or other receptacles for receiving removed items are positioned within easy reach of the sorters.
The design of processes that rely on manual separation requires a good understanding of basic principles of time and motion, of the composition of the waste, and of the comfort and safety requirements of the sorters. The application of simple, labour-intensive designs does not imply a disregard for safety and environmental control within the facilities.
The incorporation of manual separation into the design of resource recovery facilities is presented elsewhere in this chapter.