Use of Ozone-Photocatalytic Oxidation (O3/UV/TiO2) and Biological Remediation for Treatment of Produced Water from Petroleum Refineries

Abstract

Batch ozone-photocatalytic oxidation (O3/UV/TiO2) and biological remediation by macroalgae were performed in a laboratory-scale reactor to evaluate the efficiency of these processes in the degradation of contaminants and/or decrease in the ecotoxicity of produced waters of petroleum refineries. The effectiveness of the hybrid advanced oxidation process followed by biological treatment was evaluated through the physicochemical time-course analysis and ecotoxicological tests. The results showed that after 5 min of treatment the O3/UV/TiO2 combination was very effective and phenol concentration decreased by 99.9%, sulfide by 53.0%, COD by 37.7%, O&G by 5.2%, and ammonia by 1.9%. The following reductions in contaminants were obtained after 60 min of oxidation treatment: phenols 99.9%, O&G 98.2%, sulfide 97.2%, COD 89.2%, and ammonia 15%. The acute toxicity tests with the bacterium Vibrio fischeri (Lumistox) and the fish Poecilia vivipara showed a high toxicity of the raw effluents (E(L)C50<1.55% for both species), while after 60 min of treatment effluents showed lower acute toxicity toward bacteria (EC50=30.9%), but toxicity toward fish remained high (EC50=1.9%). Additional wastewater biotreatment with macroalgae Ulva spp. for wastewater depuration showed a significant toxicity reduction (EC50=89.2% for bacteria and EC50=85.7% for fish), which was due to the biosorption/transformation of metals and ammonia compounds during the biological treatment. Thus, the physicochemical results showed that a combination of O3/UV/TiO2 for 10 min followed by macroalgae depuration seems to be a good option for cost effective treatment of produced water streams.