| Abstract: | The de novo formation of organochlorines was observed in a municipalsewage treatment plant. Due to this formation, the amount of organically boundhalogens (AOX) increased 15-fold inside the sewage treatment plant. Per day,more than 6 kg of organically-bound chlorine were produced. Thisformation is not based on a metabolism of present organochlorines, it is a denovo formation out of inorganic chloride and organic substrates. The AOXtriggerconcentration in sewage sludge in Germany is 500 mgkg–1 and was sometimes exceeded by a factor of 10. Noknown anthropogenic organohalogens were found which could explain the elevatedAOX concentrations. Instead many chlorinated compounds could be identifiedwhichwere not known to be of anthropogenic origin. The compound with the highestconcentration was the 3,4-dichlorophenylacetic acid (3,4-CPAc). In one case,more than 1 g kg–1 of this compound was detected.A slaughterhouse that emits phenylacetic acid is probably the origin of thatformation. In model experiments phenylacetic acid was chlorinated with HOCl butchlorinated phenylacetic acids other than 3,4-CPAc were found. Therefore it canbe excluded that the chlorination in the sewage treatment plant takes place byan abiotic reaction with hypochlorite that might have been introduced there. Weassume that the occurring microorganisms are responsible for the de novoformation in the sewage treatment plant. The obtained knowledge could also beuseful to understand natural chlorination processes. |
