The general theory of location-routing optimisation, a class of locational analysis that considers vehicle routing issues, has been applied in the last decade to a large number of problems. Traditionally optimal wastewater and sludge management has been limited to the determination of the shortest path between sources and disposal facilities, which can be attained through the solution of a typical travelling salesman problem. The aim of this paper is to generalise this approach through the introduction of further issues: the convenience of a centralised treatment facility to reduce the sludge to a dry mass after preliminary onsite dewatering, the influence of different costs and/or prices on the optimisation task if the sludge is deposited in sanitary landfills (or disposed of in other ways) or is partially used as a fuel in suitable industrial processes, the modification of the shortest path approach into a full vehicle routing problem by assigning weights to the links between nodes of the network not necessarily equal to their distances.
