Abstract

Recalcitrant aromatic compounds reach the aerobic, anaerobic run Wastewater Treatment Plant (WWTP) units. The outflow is discharged into receiving waters and transported into oceans. Recalcitrant aromatic compounds as Di-n-Butyl Phthalate (DBP) or HCB concerning is asked can they serve denitrifying and archaea in WWTPs and oceans as electron donators. A special research program, financed by the German Research Foundation, tried giving an answer by adding effluent of the experimental WWTP, Civil Engineering Department, University Stuttgart, Germany, to triplicated, 50ml of a chloride-free, nitrate mineral salt medium containing 200ml flasks for enriching denitrifying bacteria and archaea. On chloride-free, nitrate containing mineral salt medium agar plates which contained Inter alia DBP or HCB as sole carbon source pure cultures were isolated. The with DBP or HCB as pure cultures received strains B20b1 (DBP) and B8a (HCB) served as inoculum for studying in airtight closed, the nitrate mineral salt medium containing, autoclaved, and with about 10⁷ cells of the denitrifying, on DBP or HCB agar growing isolates inoculated flasks degradation success. About DBP has been reported [1], about the U-¹⁴C-labeled HCB experiments under a to 10 or 19 Vol% O₂ adjusted Helium (He) atmosphere is reported here. From the in hexane dissolved added U-¹⁴C-labeled HCB hexane evaporated during flask evacuation and afterwards crystalized HCB covered the bottle bottom. During the 5 months of incubation (30 ᵒC) the as Pseudomonas aeruginosa identified strain B 8a formed around the HCB crystals a biofilm and monthly controlled O₂, CO₂, N₂O and N₂ changes in the flask atmosphere, the from the originally added 156mg HCB as ¹⁴CO₂ released 0.084 ± 0.3mg into the flask headspace, and the 13.26 ± 1.03mg accumulated U-¹⁴C-HCB in cells and biofilm of the 10% O₂ flask variant signalized HCB interactions which are discussed.

Keywords: Tertiary wastewater treatment; Pseudomonas aeruginosa; Denitrifying wastewater effluent isolate; Hexachlorobenzene degradation; Biofilm formation