AGRICULTURAL USAGE OF TREATMENT PLANT SLUDGES IN TURKEY

The disposal problems of the generated sludge from wastewater treatment plants have gained increasing importance in Turkey. The amount and characteristics of treatment plant sludges vary depending on wastewater composition and used wastewater treatment technologies. Landfilling, composting, incineration and land application methods are mostly used for treatment plant sludges as final disposal methods. Sludges can be used for agricultural purposes as a fertiliser to improve the structure and quality of the soil where they are applied. However, some potential problems by disposing of the sludge on land must be considered. The characteristics of sludges that affect their suitability for land application or the design of land application systems include organic matter content (as usually determined by volatile solids), nutrients, pathogens, metals, and toxic organics. The maximum application rates for a given disposal location depend on a number of factors including soil, crops, topography, potential for water contamination, weather, potential for odour production, method of the application. This paper evaluates the advantages and disadvantages of sludge disposal on land for agricultural purposes and presents some information on amounts and compositions of treatment sludges that are produced in Turkey. It is also given the standards for application of sludge on land (i.e. heavy metals, nutrients and pathogens) in the EU, the USA, and Turkey. The Turkish regulations and legislations on agricultural usage of sludges are compared with international regulations (EU Directives and US-EPA standards). The overall objective of this paper is to discuss the usage potential of treatment plant sludges as a fertiliser in Turkey and to debug the advantages and disadvantages of the sludge land application method in terms of international and national regulations