Evaluation of aerobic biological process with post-ozonation for treatment of mixed industrial and domestic wastewater for potential reuse in agriculture

Abstract

Suspended growth biological process (SGBP) with post-ozonation (O₃) was investigated for treatment of simulated complex mixed industrial and domestic wastewater at specific conditions. The SGBP was operated under complete aeration, 30/30-min and 60/30-min on/off aeration cycles and effluent was exposed to ozone at 250 mgO₃/h fixed dose and contact time 1 to 60-min. The SGBP performance was maximum under 60/30-min aeration conditions achieving 92.1, 90.6, 83.3 and 83.8% reduction in COD, BOD₅, TN and PO₄-P respectively. Nitrification (64.1%) was uninhibited even on transition to pulse aeration cycles. The concentrations of diesel oil and methylene blue dye were reduced by 83.6 and 93.5% respectively. Post-ozonation oxidized residual organics up to 19.9%, based on COD measurement, and increased effluent BOD₅ up to 49.5%. The results including the crop growth outcomes indicate that SGBP-O₃ process has great potential to improve the quality of mixed industrial and domestic wastewater considerably for various water reuse applications.

Keywords: Domestic wastewater; Industrial wastewater; Mixed-wastewater treatment; Ozonation; Suspended growth biological process; Water reuse in agriculture.