Research on characteristics of aerobic granules treating petrochemical wastewater by acclimation and co-metabolism methods

Based on the methods of gradual acclimation and co-metabolism, the feasibility of treating petrochemical wastewater using granular sludge cultivated with synthetic wastewater was surveyed in a sequencing batch airlift reactor (SBAR). During the experiment, structural properties and pollutant removal efficiency of granules were also studied. Results showed that increasing petrochemical wastewater proportion led to poor granules performance in terms of settleability, extracellular polysaccharides (EPS) production and the removal of COD and NH4+–N. When the influent was 100% of petrochemical wastewater, more serious deterioration was found in pollutant removal and the settleability of aerobic granules. At the same time, the mean granule size was reduced as well. However, aerobic granules exhibited a steady trend corresponding to stepwise decreased sludge volume index (SVI) when sodium propionate was added as a co-substrate according to 1:1 of CODC:CODPW. With presence of co-metabolism, average removal efficiencies of COD, NH4+–N and TN in petrochemical wastewater reached 89%, 94% and 67%, respectively.

Research highlights
► By acclimation and co-metabolism methods, granule morphology, structure and decontamination properties were investigated.
► With sodium propionate as co-substrate, aerobic granules exhibited a steady trend in terms of SVI, MLVSS, etc.
► Moreover, with presence of co-substrate, average removal efficiencies of COD and TN reached 89% and 67%, respectively.
► Results showed the co-metabolism could ensure effective removal of petrochemical pollutants and compact granules.