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As petrochemical industrial wastewater contains many recalcitrant compounds, the potential of hybrid biological reactors may present a resource to be tapped, especially in the actual operation of an industrial wastewater treatment facility such as Al-Wafra industrial wastewater treatment plant in Kuwait treating primarily petrochemical industry wastewater. This paper examines possible scenarios for use of hybrid reactors in existing Al-Wafra industrial wastewater treatment plant to improve its efficiency due to loss of biomass in the activated sludge process caused by extreme conditions of the industrial wastewater it receives and its inhibitors. The main innovation in this study, the hybrid reactor was constructed using a biological carrier of the high surface area Random Packing type and was operated using real wastewater samples from Al-Wafra Industrial wastewater Treatment plant. The modalities of operation included high dissolved oxygen levels (4.0 mg/l), low dissolved oxygen levels (2.0 mg/l), and under ANNAMOX conditions. Results revealed that stable biomass have developed on the support media of the hybrid biological reactor with attached to suspended biomass ratio exceeding 70% and improved efficiency of the first sequence (hybrid-to-ASP) process for TOC removal of 11-17% and 19-26% for the second sequence (ASP-to-hybrid) combination depending on the operating conditions. These results clearly reflect the unfavorable conditions for biodegradation after the primary chemical treatment at Al-Wafra plant. In addition, the dominant bacterial species were identified as pseudomonas species favor less acidic environments which were achieved after the ASP. In terms of nitrification/denitrification, the process met the ammonia and total nitrogen Kuwait standards for irrigation water of 15 and 35 respectively. Index Terms-Hybrid biological reactors, industrial wastewater, wastewater treatment. I. INTRODUCTION Petrochemical industries are an important industrial sector in Kuwait and internationally as they use and produce considerable amounts of water and wastewater. Petrochemical wastewater is treated using a variety of technologies, including physical and chemical treatment processes such as electro-coagulation, electrochemical oxidation, dissolved air flotation, adsorption, and many others [1]. However, these technologies are costly, use specialized treatment equipment, use huge amounts of chemicals, and produce excessive amounts of sludge.

This study presents the results of an analysis of the most common Volatile Organic Compounds (VOCs) in wastewater samples from one of the largest wastewater treatment plants in Kuwait. Samples from four different locations (plant influent, aeration tank inlet, aeration tank, and plant effluent) were collected weekly and were analyzed for toluene, benzene, xylene, 1, 3, 5 trimethylbenzene, dichloromethane and chloroform. The results showed that all the selected VOCs were detected except benzene. The average concentrations of VOCs that entered the treatment plant were as follows: chloroform 0.22 ± 0.03 μg/mL, dichloromethane 0.18 ± 0.05 μg/mL, toluene 0.08 ± 0.01 μg/mL, O-Xylene 0.03 μg/mL, M-Xylene 0.01 μg/mL, P-Xylene 0.02 μg/ml, and 1,3,5-trimethylbenzene 0.02 μg/mL. The concentration of VOCs during the treatment processes decreased for all the selected VOCs (treatment efficiency >98%), except chloroform, which has increased. The disinfection process in the treatment plant might have generated byproducts (such as chloroform) which could have increased chloroform concentration. In conclusion, all of the analyzed VOCs in this study were lower than the maximum level of VOCs in treated wastewater.