Sustainable Strategies for Sludge Treatment and Disposal in Iran

In spite of gradual advances in municipal wastewater treatment in Iran, the handling of sewage sludge is often lacking appropriate disposal strategies. Moreover, until now there is no proper legal framework concerning the disposal of sludge in Iran. Therefore, the objective of the present contribution is to demonstrate an approach for planners and decision-makers in Iran to identify suitable solutions for sludge treatment and disposal, taking into consideration all relevant boundary conditions. The fundamental differences between the principal alternatives regarding the disposal of sewage sludge, i.e., landfilling, agricultural reuse and incineration, are clarified and comprehensively discussed. In any case, the stabilisation of primary and excess sludge is strongly recommended. In addition to the non-negligible energy gain obtained by anaerobic sludgedigestion, any application involving possible human contact with the sludge, such as reuse in agriculture, requires its hygienisation in order to minimise health risks. In regions with increased agricultural land use, the reuse of digested sludge represents a viable option due to the valuable composition of sludge in terms of nutrients. However, the distance between the point of generation and the point of final application, as well as the total demand for fertilisers within a reasonable range of the plant are limiting factors with respect to agricultural sludge reuse.