Biosolids from the WWTP of Thessaloniki were examined for the leaching of phosphorus (as PO4(3-) -P), nitrogen (as NH4+ (-N) and NO3- (-N)), and organic matter (as TOC and COD), using two tests: (1) a pH static leaching test and (2) a characterization test, relating contaminant release to the liquid to solid (L/S) ratio. Moreover, a Microtox toxicity test was conducted, to examine the pH dependency of the toxicity of the sludge leachate on the Vibrio fischeri bacterium. Maximum phosphorus release was observed at pH < 3 and at pH > 10. Ammonium nitrogen exhibited maximum leachability at near neutral pH conditions, while nitrate nitrogen exhibited a mild increase in the leachate, as the leachant pH increased from 2 to 12. Both TOC and COD exhibited an increase in the leachate concentration, as the leachant pH was increased from 2 to 12. Ecotoxicological analysis showed that maximum toxicity occurred at very low and very high pH-conditions. As liquid-to-solid ratio increased, the leachate concentration (in mg/l) of all parameters studied decreased. The results of the study were used to conduct a release assessment estimate for the case of Thessaloniki.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.