Novel strategies in sewage sludge treatment

Sewage sludge is not only the sink for nutrients removed from wastewater but also for hazardous substances. When sewage sludge is reused in agriculture these hazardous substances can be harmful to the environment depending on their concentration. Nevertheless, the mere disposal of sewage sludge cannot be purposeful as the contained nutrients and the organic material offer a biologically valuable fertilizer. Currently, agricultural reuse of sewage sludge is discussed controversially in Germany. Changes in legal requirements for sewage sludge application are planned that will set lower limit values for hazardous substances and higher quality requirements in general. With these new restrictions, sewage sludges may not be suitable for agricultural reuse any longer. The focus is on alternative sewage sludge treatment technologies that gain the most economic and ecological benefit from the sludge's valuables. Several technologies for nutrient recovery, especially phosphorus, have been developed to recycle finite natural resources. This article will provide an overview on novel strategies for sewage sludge treatment and management especially in regard to new legal requirements.