Speciation of heavy metals in municipal sewage sludge from different capacity sewage treatment plants

The known chemical methods for heavy metals removal from sewage sludge were inapplicable due to high costs, operational difficulties and low efficiency (Ryu et al. 2003). Microbiological methods, based on the transition of heavy metals from sewage sludge to reflux, are in the testing phase (Xiang et al. 2000, Ryu et al. 2003).