Immobilization of activated sludge in poly(ethylene glycol) by UV technology and its application in micro-polluted wastewater

A new method, ultraviolet (UV) technology, was utilized to immobilize activated sludge in poly(ethylene glycol) (PEG) gel carriers. A number of characteristics of immobilized cells, such as water content, oxygen uptake rate, and protein content, were examined, and performance in batch culture for treating synthetic micro-polluted wastewater with different C/N ratios and different pH values was also investigated. The bioactivity of immobilized cells was maintained during immobilization and the cells showed high nitrification activity after 10–15 d acclimation. Ammonia removal increased with C/N ratio while TOC removal decreased with it. However, more than 85% of the ammonia nitrogen and 72% of the TOC could be reduced in 4–6 h in all cases. No obvious effects on nitrification were seen for pH shocks at pH 6, 7, 8 or 9, but a pH shock at pH 5 caused a 30% loss of nitrification efficiency. SEM images showed that the immobilization beads were highly porous and that immobilized nitrifiers dominated the surface and within the core of the gel beads.