Isolation and identification of an iopromide-degrading strain and its application in an A2/O system

► Isolate and identify an iopromide-degrading strain I-24. ► Evaluate the effects of various factors on IOPr degradation by strain I-24. ► Examine the enzymatic activity of I-24 supplied with different carbon sources. ► Apply strain I-24 to a lab-scale waste water treatment process. ► Analyse the 16S rDNA fragments obtained from the reactor by DGGE and UPGMA cluster. An iopromide (IOPr)-degrading bacterium was isolated from activated sludge of a wastewater treatment plant in Shanghai. Based on its morphology, physiological-biochemical characteristics and a phylogenetic analysis of its 16S rRNA sequence, the bacterium was identified and named as Pseudomonas sp. I-24. The optimum condition for degrading IOPr was at 30°C and pH 7.0. After 5days, strain I-24 could degrade 30mg/L IOPr by 99% in a basal salts medium with a 5% (V/V) inoculum and 200mg/L starch as the primary substrate. When applied to an Anaerobic-Anoxic/Aerobic (A2/O) process, with the coexistence of other bacteria, the strain I-24 got lower (61.3%) IOPr removal, but in two A2/O systems (with and without I-24 inoculation), the CODcr removal were both approximately 95%. The trial dosed with strain I-24 showed better IOPr removal than the un-dosed one. I-24 sustained its abundance in the A2/O system during the experiment.