A systems approach evaluation of sludge management strategies: sludge management in Valparaíso and Aconcagua, Chile.

In the 5th Region, located in central Chile, infrastructure projects are being implemented in order to increase the capacity to treat and dispose of sewage. In order to analyse the sludge management alternatives the ORWARE model was used. The research project was divided in two stages: in the first stage, the sewage and sludge management strategies to be compared as well as the objectives were established. The management alternatives chosen were for chemical or biological treatment of sewage while for sludge the management alternatives were based on digestion, composting or lime stabilisation. The second stage included simulation and analysis of results. The main conclusions of the work were: if "lowest possible emissions" is the main objective of sewage treatment, biological treatment should be applied. Regarding pathogen reduction, both chemical precipitation and biological treatment attain an adequate reduction if the treated sewage is to be discharged to the sea. On the other hand, additional disinfection is needed in the case of discharge to rivers. Control at source should be stressed to avoid heavy metals and toxic organic compounds in the sludge.