Options for sustainable sewage sludge management in small wastewater treatment plants on islands: The case of Crete

This work examines four essentially different and widely established methods for the treatment of sewage sludge and determines the applicability of each one of them in the economical, geographical and environmental settings of the island of Crete in Greece. Under these conditions, the combination of lime stabilization and solar drying appears to be the optimum solution for sewage sludge management. For each of the treatment technologies considered, cost indicator spreadsheets were developed that enabled the automatic calculation of the total cost. Τhe cost of the lime stabilization–soar drying combined treatment is comparable to the cost of composting or thermal drying alone. The judgment criteria and the economical parameters used for the evaluation of the methods may be a useful tool for other wastewater treatment plants in various Mediterranean islands.