Removal of pollutants and accumulation of high-value cell inclusions in heavy oil refinery wastewater treatment system using Rhodopseudomonas and Pseudomonas:Effects of light intensity

Abstract

Photosynthetic bacteria (PSB) wastewater treatment is a special technology which can simultaneously remove pollutants from wastewater and produce high-value cell inclusions, but the characteristics of PSB in the heavy oil refinery wastewater treatment system are not clear. This study evaluated pollutants removal with different light intensities, and the accumulation of biomass, carotenoid, bacteriochlorophyll, and coenzyme Q10 while treating heavy oil refinery wastewater in PSB system. Furthermore, high sequencing technology and q-PCR were used to analyses microbial community structure and the quantity of Rhodopseudomonas and Pseudomonas in the systems. Results showed that 500 lx was the optimal intensity for SCOD and NH4+-N removal, the corresponding removal ratios were 62.66% and 91.54%, respectively, and the yield of coenzyme Q10 reached the highest on the 8 th day, which was 9.90 mg/g-DCW, with the highest dehydrogenase concentration reaching 71.83 mg/L. While 4000 lx was the optimal light intensity for the yield of carotenoid, bacteriochlorophyll and biomass production, the corresponding accumulations were 10.64 mg/g-DCW, 5.88 mg/g-DCW, and 550 mg/L, respectively. Furthermore, the relative abundance of Pseudomonas was the highest at 500 lx, which was 37.13%, and the gene number was 4.56 × 105 gene copies/μL, 2.34 times of that before the reaction. At 4000 lx, the relative abundance of Rhodopseudomonas was the highest, which was 58.91%, and the gene number was 9.51 × 105 gene copies/μL, 7.15 times of that before the reaction. The results proved that it was feasible for culturing Rhodopseudomonas and Pseudomonas in PSB system to treat heavy oil refinery wastewater and realized cell inclusions accumulation simultaneously. The results could provide theoretical guidance for industrial treatment of refinery wastewater.