Nowadays, antibiotics are widely used, increasing the risk of contamination of the water body and further threatening human health. The traditional water treatment process is less efficient in degrading antibiotics, and the advanced oxidation process (AOPs) is cleaner and more efficient than the traditional biochemical degradation process. The combined ozone/peroxymonosulfate (PMS) advanced oxidation process (O₃/PMS) based on sulfate radical (SO₄^•−) and hydroxyl radical (•OH) has developed rapidly in recent years. The O₃/PMS process has become one of the most effective ways to treat antibiotic wastewater. The reaction mechanism of O₃/PMS was reviewed in this paper, and the research and application progress of the O₃/PMS process in the degradation of antibiotics in drinking water and wastewater effluent were evaluated. The operation characteristics and current application range of the process were summarized, which has a certain reference value for further research on O₃/PMS process.

Biochar (BC) is a new type of carbon material with a high specific surface area, porous structure, and good adsorption capacity, which can effectively adsorb and enrich organic pollutants. Meanwhile, nano zero-valent iron (nZVI) has excellent catalytic activity and can rapidly degrade organic pollutants through reduction and oxidation reactions. The combined utilization of BC and nZVI can not only give full play to their advantages in the adsorption and catalytic degradation of organic pollutants, but also help to reduce the agglomeration of nZVI, thus improving its efficiency in water treatment and providing strong technical support for water resources protection and environmental quality improvement. This article provides a detailed introduction to the preparation method and characterization technology, reaction mechanism, influencing factors, and specific applications of BC and nZVI, and elaborates on the research progress of BC-nZVI in activating persulfate (PS) to degrade organic pollutants in water. It has been proven experimentally that BC-nZVI can effectively remove phenols, dyes, pesticides, and other organic pollutants. Meanwhile, in response to the existing problems in current research, this article proposes future research directions and challenges, and summarizes the application prospects and development trends of BC-nZVI in water treatment. In summary, BC-nZVI-activated PS is an efficient technology for degrading organic pollutants in water, providing an effective solution for protecting water resources and improving environmental quality, and has significant application value.

The ozone/peroxymonosulfate (O₃/PMS) system has attracted widespread attention from researchers owing to its ability to produce hydroxyl radicals (•OH) and sulfate radicals (SO₄^•−) simultaneously. The existing research has shown that the O₃/PMS system significantly degrades refinery trace organic compounds (TrOCs) in highly concentrated organic wastewater. However, there is still a lack of systematic understanding of the O₃/PMS system, which has created a significant loophole in its application in the treatment of highly concentrated organic wastewater. Hence, this paper reviewed the specific degradation effect, toxicity change, reaction mechanism, various influencing factors and the cause of oxidation byproducts (OBPs) of various TrOCs when the O₃/PMS system is applied to the degradation of highly concentrated organic wastewater. In addition, the effects of different reaction conditions on the O₃/PMS system were comprehensively evaluated. Furthermore, given the limited understanding of the O₃/PMS system in the degradation of TrOCs and the formation of OBPs, an outlook on potential future research was presented. Finally, this paper comprehensively evaluated the degradation of TrOCs in highly concentrated organic wastewater by the O₃/PMS system, filling the gaps in scale research, operation cost, sustainability and overall feasibility.

Tetracycline (TC) contamination in water is one of the key issues in global environmental protection, and traditional water treatment methods are difficult to remove antibiotic pollutants.Therefore, efficient and environmentally friendly treatment technologies are urgently needed. In this study, activated persulfate (PS) using a biochar-loaded nano zero-valent iron (BC-nZVI) advanced oxidation system was used to investigate the degradation effect, influencing factors, and mechanism of TC. BC-nZVI was prepared using the liquid-phase reduction method, and its structure and properties were analyzed by various characterization means. The results showed that nZVI was uniformly distributed on the surface or in the pores of BC, forming a stable complex. Degradation experiments showed that the BC-nZVI/PS system could degrade TC up to 99.57% under optimal conditions. The experiments under different conditions revealed that the iron-carbon ratio, dosing amount, PS concentration, and pH value all affected the degradation efficiency. Free radical burst and electron paramagnetic resonance (EPR) experiments confirmed the dominant roles of hydroxyl and sulfate radicals in the degradation process, and LC–MS experiments revealed the multi-step reaction process of TC degradation. This study provides a scientific basis for the efficient treatment of TC pollution in water.

This study investigated the degradation efficacy, kinetics, and mechanism of the ozone (O₃) process and two enhanced O₃ processes (O₃/peroxymonosulfate (O₃/PMS) and O₃/peroxymonosulfate/iron molybdates/biochar composite (O₃/PMS/FeMoBC)), especially the O₃/PMS/FeMoBC process, for the degradation of tetracycline (TC) in water. An FeMoBC sample was synthesized by the impregnation–pyrolysis method. The XRD results showed that the material loaded on BC was an iron molybdates composite, in which Fe₂Mo₃O₈ and FeMoO₄ accounted for 26.3% and 73.7% of the composite, respectively. The experiments showed that, for the O₃/PMS/FeMoBC process, the optimum conditions were obtained at pH 6.8 ± 0.1, an initial concentration of TC of 0.03 mM, an FeMoBC dosage set at 200 mg/L, a gaseous O₃ concentration set at 3.6 mg/L, and a PMS concentration set at 30 μM. Under these reaction conditions, the degradation rate of TC in 8 min and 14 min reached 94.3% and 98.6%, respectively, and the TC could be reduced below the detection limit (10 μg/L) after 20 min of reaction. After recycling for five times, the degradation rate of TC could still reach about 40%. The introduction of FeMoBC into the O₃/PMS system significantly improved the TC degradation efficacy and resistance to inorganic anion interference. Meanwhile, it enhanced the generation of hydroxyl radicals (^•OH) and sulfate radicals (SO₄^•−), thus improving the oxidizing efficiency of TC in water. Material characterization analysis showed that FeMoBC has a well-developed porous structure and abundant active sites, which is beneficial for the degradation of pollutants. The reaction mechanism of the O₃/PMS/FeMoBC system was speculated by the EPR technique and quenching experiments. The results showed that FeMoBC efficiently catalyzed the O₃/PMS process to generate a variety of reactive oxygen species, leading to the efficient degradation of TC. There are four active oxidants in O₃/PMS/FeMoBC system, namely ^•OH, SO₄^•−, ¹O₂, and •O₂⁻. The order of their contribution importance was ^•OH, ¹O₂, SO₄^•−, and •O₂⁻. This study provides an effective technological pathway for the removal of refractory organic matter in the aquatic environment.

Based on the kinetics of the treatment process of the completely mixed reactor in series, this study reveals the relationship between the reactor stages and the treatment efficiency, and it was applied to the simultaneous nitrogen and phosphorus removal process. The strengthening effect of the reactor stages of the main anoxic sections on the anoxic phosphorus absorption efficiency and the contribution to improving the treatment effect were investigated. Using sewage with a low carbon-to-nitrogen ratio as the research object and keeping the operation parameters of the improved anaerobic–anoxic–oxic (A²O) process unchanged, the experimental research was carried out under the condition that reactor stages in series of the main anoxic section were one, two, three and four, respectively. The results showed an increase in the number of reactors in series in the main anoxic zone. The total phosphorus (TP) concentration in the effluent of the main anoxic stage decreased significantly, and the phosphorus uptake increased from 4.411 g/d (when n; the number of reactor stages in series was one) to 5.086 g/d when n was 4. Additionally, the nitrate nitrogen (NO₃⁻–N) concentration in the effluent decreased, from 12.53 mg/L when n was one, to 9.62 mg/L when n was four, the removal rate of total nitrogen (TN) increased, from 56.86% when n was one to 65.98% when n was four, and the reduction power of nitrate nitrogen increased, and the denitrification rate increased. The increase in the number of reactors in series enhanced the anoxic phosphorus absorption and denitrification performance. Therefore, the main anoxic section of the synchronous nitrogen and phosphorus removal system can be designed and operated as reactors in series.