Leachates From Landfill Sites In Thessaloniki, Greece: Effect Of Aging

Abstract

Sanitary landfilling still is one of the most common management systems of solid urban wastes. The persistent environmental impact of landfills depends on leachate characteristics. The present study aimed at the characterisation of leachate from two landfill sites in the prefecture of Thessaloniki, Greece. Mavrorachi landfill stands in our study as a representative Greek active landfill site, that started operating in 2008. Tagarades landfill has stopped receiving waste from 2008 after 27 years of full operation. In this investigation, leachate samples were physico-chemically characterised so as to assess their pollution potential and their concentration in regard to the type and age of landfill. Elevated concentrations of inorganic and organic constituents were observed in the leachate composition. COD ranged from 2,490 mg/L to 19,700 mg/L, while the respective range for BOD was 390-14,850 mg/L during a 35-year period. The pH values of the leachate samples presented more moderate fluctuations between 7.3 and 8.5. In addition, the ammoniacal nitrogen content increased as landfill age increased, whereas heavy metals concentrations showed significant variations with a slight decreasing trend. The results presented in this paper proved that as time passed, the values of most parameters decreased as the biodegradable compounds are broken down while the refractory compounds resist to biodegradation. Thus, the age has a pronounced influence on the composition of leachate. This study also focused on quantifying the level of contamination that leachates can be potentially cause on a comparative basis by Leachate Pollution Index (LPI). LPI values showed that pollution load was declining but is still not negligible after 33 years.