Study of a management model of minimization of sewage sludge’s disposal costs
Summary
Management of sewage sludge is becoming a problem all over the world (in all industrial and development countries). The quantity of sludge is raising mainly because of the increasing of urban population and the improvement of life conditions. At the same time counties’ regulations are fixing more restrictive limitation on agricultural re-use of sewage sludge (due to environmental protection and population’s health) and on landfill disposal (reduction in disposal of organic wastes). Considering the increase of production and the more and more restrictive limitation on final destination of sewage sludge, it can be easily understood how an efficient management of biosolids is necessary to minimize costs.
The study of sewage sludge management is the general objective of this graduation thesis. The particular objective is the development of a mathematical model to optimize the management of the biosolids’ treatment chain. The optimization model tries to minimize the management’s costs of sewage sludge;
besides a more rational and planned use of resources (as regards to the operations of biosolids’ management) can has a minor environmental impact
The two optimization models which have been developed concern the management of sewage sludge from the production to the recovery and disposal activities. The first model can process different kinds of sludge in different ways, the second one considers only a single type of sludge and it has been adapted to the Valdinievole’s territory (A.T.O. 2 – Tuscany). Data deriving from the purification plants of Valdinievole has been used to execute an application of the second model. The comparison of the application’s results to the present management system of biosolids suggests that the use of the optimization model is convenient in case of large amounts of sewage sludge and long distances to reach the alternative platform treatment. In this kind of situations the data to be processed are more numerous and therefore the optimal management strategy is difficult to evaluate without the use of an optimization model.
The study concerns also the regulation and technical aspects of the possible final disposal of sewage sludge and the technical solutions to minimize biosolids’
production; the quantities of sewage sludge produced from the purification plants of Garfagnagna and Media Valle’s territory (A.T.O. 1 – Tuscany) has been estimated to plan a right management.
