Effective and mechanistic insights into shale gas wastewater reverse osmosis concentrate treatment using ozonation-biological activated carbon process

Reverse osmosis technology plays a pivotal role in the resource utilization of shale gas wastewater. However, the treatment of the resulting reverse osmosis concentrate (ROC) with high salinity and high concentration of organic matter is a huge challenging. This study aims to indicate the enhancement effects and mechanisms of pre-ozonation on the removal efficacy of organic matter in ROC by the biological activated carbon (BAC) system. Research results showed that during the stable operation stage, the ozonation (O3 and O3/ granular activated carbon)-BAC system can remove 43.6%-72.2% of dissolved organic carbon, achieving a 4 to 7 times increase in removal efficiency compared to the alone BAC system. Through dynamic analysis of influent and effluent water quality, analysis of biofilm performance, combined with the succession and function prediction analysis of microbial community structure, the main enhancement mechanisms were revealed: 1) pre-ozonation significantly improved the biodegradability of ROC, by 4.5 to 6 times, and reduced the organic load of BAC system; 2) pre-ozonation contributes to selective enrichment of microbes capable of degrading organic compounds in BAC system, thereby enhancing the biodegradation capability and stability of the microbial community; 3) pre-ozonation accelerated the regeneration rate of GAC adsorption site. It can provide valuable suggestions for treating ROC by pre-oxidation combined with biotreatment process.

反渗透技术在页岩气废水资源化利用中发挥着至关重要的作用。然而，针对该工艺产生的高盐高有机物浓度反渗透浓缩液（reverse osmosis concentrate，ROC）进行处理，仍是一项极具挑战性的任务。本研究旨在探究预臭氧化（pre-ozonation）对生物活性炭（biological activated carbon，BAC）系统去除反渗透浓缩液中有机物的强化效果与作用机制。研究结果表明，在稳定运行阶段，臭氧化（O3及O3/颗粒活性炭（granular activated carbon，GAC））-BAC系统对溶解性有机碳（dissolved organic carbon）的去除率可达43.6%~72.2%，较单独BAC系统提升了4~7倍。通过对进出水水质的动态分析、生物膜性能表征，并结合微生物群落结构的演替与功能预测分析，本研究揭示了其核心强化机制：1. 预臭氧化可将反渗透浓缩液的可生物降解性提升4.5~6倍，显著降低了BAC系统的有机负荷；2. 预臭氧化有助于在BAC系统中选择性富集能够降解有机污染物的微生物，进而提升微生物群落的降解能力与运行稳定性；3. 预臭氧化可加速颗粒活性炭吸附位点的再生速率。该研究可为预氧化联合生物处理工艺处理反渗透浓缩液提供有价值的参考依据。