Degradation of p-nitroaniline from aqueous solutions using ozonation/Mg-Al layered double hydroxides integrated with the sequencing batch moving bed biofilm reactor

Abstract

In this study, two treatment steps were performed to completely remove p-nitroaniline (PNA). In the first stage, the catalytic ozonation process (COP) using the synthesized nanoparticles of magnesium–aluminum layered double hydroxide (MgAl-LDH) was applied for pre-treatment. Effective parameters in the COP, including initial pH, initial PNA concentration, catalyst dose, and contact time has been investigated. Response Surface Method)RSM(was applied to optimize process conditions in the COP. The effluent from the COP entered the sequencing batch moving bed biofilm reactor (SBMBBR). The optimum conditions for the COP process were initial PNA concentration: 120 mg/L, pH: 8.25, LDH dose: 750 mg/L, and reaction time: 70 min. Under these conditions, the maximum removal efficiency of PNA, COD, and TOC was about 91.5, 83, and 70%, respectively. The biological reactor was operated under conditions of hydraulic retention time (HRT) of 24 h, pH of 6.5–7, mixed liquor suspended solids attached to bio-carriers (MLSSatt.) of 4700 mg/L, mixed liquor volatile suspended solids attached to bio-carriers (MLVSSatt.) of 3200 mg/L, MLSS of 1000 mg/L, and MLVSS of 880 mg/L. In this study, using the COP/SBMBBR system, the complete PNA analysis and maximum removal efficiency of COD and TOC were about 99 and 97%, respectively.