Technological process of sewage sludge de-watering by impulse method and assesment of options to use dried material

Abstract

Waste water sewage sludge is one of municipal waste materials that could be used for nutrient recycling in agriculture, plantation forestry or re-cultivated areas. Sewage sludge contains at least 80 % of water and nutrient rich organic materials what could be used for fertilization of bare soils or for energy production instead of landing on landfills. The de-watering process of sludge by using the impulse method has less energy consumption and higher content of dry matter in the final product is reached in comparison with traditional drying. The aim of the study is to elaborate a method for sewage sludge drying, which allows saving the biological value of final organic material. Impulse interval, frequency, air pressure and temperature in the camera are the key factors for an economically effective process and reaching of qualitative final product. The product could be used for fertilization of non-food products, tree planting, perennial grasses for seed production etc. If sludge contains too high concentration of heavy metals, it could be burned for energy production, and just ashes deponent on landfills. The technological and energy consumption aspects of the methods were analyzed. For sewage sludge containing a low content of heavy metals. Drying is more sustainable after - and pretreatment methods before recycling of plant nutrient elements included in sludge organic material for farming. Transport of dried material is more economical as fresh mass, as well dry material does not smell. The barriers for implementation of these technologies into common practice are more political than technical.