Biological treatment: A response to the accumulation of biosolids

Municipal wastewater treatment produces significant quantities of biosolids, which needs to be managed with respect to the environment, according to the EU and national legislations. In last years, biosolids became a major environmental issue due to increased production, lack of sustainable solutions, and public concern about environmental and food safety. The problem is even more pronounced because of different strategies for management taken up by each country and different disposal methods. In this review chapter, a discussion of the most common solutions has been presented. Conventional methods, such as incineration and landfilling, are currently not very well accepted, while the sludge is rich in organic materials and nutrients and could be used as a fertilizer with appropriate treatment method. In addition, the aerobic and anaerobic digestions are well situated in almost all EU countries and ensure sanitation of the biosolids and significant reduction of heavy metals and greenhouse gas emissions in the resulting by-product, making them environmentally friendly and acceptable by the population. Finally, a case study on composting and vermicomposting of biosolids and biodegradable waste is presented.