[Bioaugmentation with immobilized genetically engineered microorganism (GEM)/CAS process for treatment of atrazine...

Bioaugmentation with immobilized genetically engineered microorganism (GEM)/conventional activated sludge (CAS) process for treatment of atrazine wastewater was investigated and effects of hydraulic retention time (HRT) on treatment efficiency, activities of GEM were discussed. The results showed that when HRT was 4-24 h, significant removal of atrazine was obtained in the process with bioaugmentation. When the HRT was 24 h, the first stage of the process got best treatment effect: average atrazine removal rate was 96.64% and average atrazine concentration in effluent was 0.56 mg/L. When HRT was changed to 12 h, 8 h or 4 h, the removal rate was 88.59%, 89.79% and 88.61% respectively. The average removal of COD in 4 runs was 72.76%, 64.59%, 66.16% and 65.84% respectively, Significant loss of GEMs was not observed but strong growth activities, formation of biofilm and zoogloea on the surface of immobile particles were observed via scanning electron microscope (SEM). The mechanical stability of the particles remained unchanged after nearly two-month operation.