Polish experience in operation of sludge treatment reed beds

Sludge Treatment Reed Beds (STRBs) is the technology of sludge treatment, which is based on natural processes occurring in the environment, in specially designed and operated facilities to achieve benefits for the environment. Integrated dewatering and stabilization occur in reed systems. For economic and environmental reasons it is an attractive solution, especially in rural areas where there are no appropriate facilities. In the recent years many European countries like Denmark, France or Germany have applied this technology for sewage sludge management. Poland has also some experience in dewatering and stabilization of sewage sludge in STRB systems. The objective of the paper is to present the current experience and lessons learned from the operation and to assess the quality of sewage sludge from STRBs in Poland. The analyzed sewage sludge was treated in STRBs located in five wastewater treatment plants: Darzlubie, Swarzewo, Zambrow, Nadole and Gniewino, Poland. Two from the analyzed systems (Darzlubie and Swarzewo) worked only in a pilot scale and three of them (Darzlubie, Swarzewo and Nadole) did not work any longer. In the collected samples of sludge the evaluation of dewatering and stabilization processes, fertilizer properties, as well as heavy metals concentrations were determined. The average dry matter content in sludge treated in Polish STRBs was from 11.2 to even 53.7%. The degree of mineralization in analyzed systems was from 31.4 to 68.6%. The average nutrient contents was for nitrogen from 1.0 to 10% DM and for phosphorus from 0.2 to 1.0% DM. The conducted research confirms that sludge treated in STRBs is dewatered and stabilized, thus it could be used as a fertilizer in agriculture.