Treatment of petrochemical wastewater by 3D printed biocarrier integrated activated sludge system: Optimization by response surface methodology, biokinetics, and microbial community

The existence of petrochemicals in petrochemical wastewater (PW) causes it detrimental and complex wastewater. The treatment plant is fed with lower PW concentrations of influent because of the high levels of toxicants. In this study the treatment of PW was carried out with AnoxKaldnes™ (K5) carriers, and 3D printed biocarrier in continuous flow integrated activated sludge system. The integrated activated sludge reactor assisted with K5 biocarrier (IAS-CB) while other assisted with 3D printed biocarrier (IAS-3PB) operated under similar conditions with varying hydraulic retention time (HRT) from 12 h to 24 h and PW concentration from 20 % to 100 % for organic and nutrient removal. The optimized result using response surface methodology (RSM) revealed better performance of IAS-3PB than IAS-CB for organics and nutrient removal. The maximum removal efficiency of total phosphorus (TP), Chemical oxygen demand (COD), and ammonia‑nitrogen (NH₄⁺-N) was 78.4 %, 90.3 %, and 86.2 % in IAS-3PB while 75.2 %, 88.1 %, and 84.2 % in IAS-CB, respectively. Moreover, the RSM predicted optimized conditions revealed higher removal efficiencies with more PW concentration and shorter HRT in IAS-3PB. The IAS-3PB achieved better nitrification rate due to the adherence of Nitrosomonas, Nitrospira and Acinetobacter on 3PB as a biofilm with a higher abundance. However, the abundance of Proteobacteria, and Bacteroidetes were witnessed in IAS-CB. The modified Stover-Kincannon biokinetic model was found to be the best fit for both the reactors for organic and nutrient removal. Thus, these findings can provide solution to petrochemical industry for the treatment of PW with higher loading conditions.