Synergistic oxidation of humic acid treated by H2O2/O3 activated by CuCo/C with high efficiency and wide pH range.

Combination of oxidation processes are one of the most promising humic acid treatment technologies. Single oxidant or even two oxidants in advance oxidation process can hardly achieve satisfactory removal efficiency of refractory organic matter, mainly humic acid, in the treatment process of reverse osmosis concentrates from landfill leachate. To solve this problem, this study investigated the synergistic degradation of Humic acid (HA) using a Cu and Co supported on carbon catalyst (CuCo/C) in a Hydrogen peroxide (H2O2) with ozone (O3) system. The catalyst was characterized by performing SEM, XRD, BET, XPS and FTIR technologies. UV-vis spectra, 3D Excitation Emission Matrix Spectra (3D-EEM) and gas chromatography-mass spectrometry (GC-MS) were applied for exploring degradation mechanism of HA. To further understand the oxidation mechanism, electron paramagnetic resonance (EPR) was used to evaluate the generation of hydroxyl (·OH) and superoxide radicals (O2·-). As a result, CuCo/C catalyst possessed stable catalytic performance for HA degradation with a wide pH range from 5 to 8, while T = 40 °C，catalyst dosage of 2.4 g/L，O3 intake rate of 0.15 g/min and H2O2 dosage of 1.92 mL/L, the degradation rate of total organic carbon (TOC) achieved 40-46.5 mg·L-1min-1. As affirmed by the EPR, ·OH and O2·- were effectively generated with addition of the CuCo/C catalyst. Degradation performance of UV254 proved that the catalytic activity can still be maintained above 95% with removal rate of 82% after 5 cycles reuse. GC-MS shows that the oxidation products mainly consist of amide, benzoheterocyclic ring and carboxylic acid. This work promotes an effective method for degrading HA, which has the potential for satisfactory application in landfill leachate.

Comparison of moving bed biofilm reactor and bio-contact oxidation reactor start-up with heterotrophic nitrification-aerobic denitrification bacteria and activated sludge inoculation under high ammonia nitrogen conditions.

To overcome poor ammonia tolerance and removal performance of bio-contact oxidation (BCO) reactor inoculated with activated sludge for high-ammonia nitrogen (NH4+-N) chemical wastewater treatment, this study compared inoculating heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria in moving bed biofilm reactor (MBBR) with activated sludge inoculation in BCO reactor under simulated high NH4+-N conditions. Results revealed that MBBR achieved faster biofilm formation (20 days vs. 100 days for BCO) with notable advantages: 27.6 % higher total nitrogen (TN) and 29.9 % higher NH4+-N removal efficiency than BCO. Microbial analysis indicated optimal enrichment of the key nitrogen removal (NR) bacterium Alcaligenes, leading to increased expression of NR enzymes hydroxylamine reductase, ensuring the superior NR efficiency of the MBBR. Additionally, functional enzymes and genes analysis speculated that the NR pathway in MBBR was: NH4+-N â†’ NH2OH â†’ NO3--N â†’ NO2--N â†’ NO â†’ N2O â†’ N2. This research offers a practical and theoretical foundation for extending HN-AD bacteria-inoculated MBBR processes.

[An examination of the carbon metabolic pathways in Acinetobacter sp. TAC-1 in the context of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) utilization].

The present study aimed to unravel the carbon metabolism pathway of Acinetobacter sp. TAC-1, a heterotrophic nitrification-aerobic denitrification (HN-AD) strain that utilizes poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as a carbon source. Sodium acetate was employed as a control to assess the gene expression of carbon metabolic pathways in the TAC-1 strain. The results of genome sequencing demonstrated that the TAC-1 strain possessed various genes encoding carbon metabolic enzymes, such as gltA, icd, sucAB, acs, and pckA. KEGG pathway database analysis further verified the presence of carbon metabolism pathways, including the glycolytic pathway (EMP), pentose phosphate pathway (PPP), glyoxylate cycle (GAC), and tricarboxylic acid (TCA) cycle in the TAC-1 strain. The differential expression of metabolites derived from distinct carbon sources provided further evidence that the carbon metabolism pathway of TAC-1 utilizing PHBV follows the sequential process of PHBV (via the PPP pathway)→gluconate (via the EMP pathway)→acetyl-CoA (entering the TCA cycle)→CO2+H2O (generating electron donors and releasing energy). This study is expected to furnish a theoretical foundation for the advancement and implementation of novel denitrification processes based on HN-AD and solid carbon sources.

Treatment of Landfill Leachate Reverse Osmosis Concentrates by Advanced Oxidation-Heterotrophic Nitrification-Aerobic Denitrification Combination process.

This study aimed to develop a multistage treatment system for highly toxic wastewater named reverse osmosis concentrates of landfill leachate. Therefore, a combination of the ammonia stripping process (ASP), catalytic ozone oxidation process (COP), and heterotrophic nitrification-aerobic denitrification process (HNADP) was proposed and the quality of effluent was evaluated for the concentration of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total nitrogen (TN). ASP had moderate removal efficiency of NH4+-N, and TN in the effluent. COP was catalyzed by cerium-supported-activated carbon achieved good performance in disposal of COD. The effluent of HNADP had the most significant removal efficiency of COD, NH4+-N, and TN. As a result, the effluent of combined process successfully met the discharge standards for NH4+-N and TN according to Table 1 of GB 16889-2008 in China. To investigate the microbial mechanism of pollutant removal in HNADP, 16S rRNA high-throughput sequencing was performed and the results suggested that the relative abundance and diversity of microorganisms fluctuated with the changes of COD/TN ratio in HNADP. Truepera and Halomonas were identified as the key genera involved in the simultaneous degradation of COD and nitrogen-containing pollutants, the functional genes (hao, amoA, nirS, and nirK) were predicted in nitrification and denitrification process. Overall, this study demonstrates a feasible multistage system for treatment of concentrates and propose that further explorations of combined techniques may lead to even more satisfactory removal efficiencies.

Evaluation of carbon mineralization and its temperature sensitivity in different soil aggregates and moisture regimes: A 21-year tillage experiment.

Characterizing soil organic carbon (SOC) mineralization and its temperature sensitivity (Q10) under different soil moisture in tillage systems is crucial for determining global carbon balance under climate warming and increasing precipitation. Aggregate protection can potentially govern SOC mineralization and its Q10. However, how tillage and aggregate sizes affect SOC mineralization and its Q10, especially under varying soil moisture, remains unclear. Soil samples (0-10 cm and 10-20 cm) were collected from a 21-year field study with four tillage treatments: conventional tillage (CT), reduced tillage (RT), no-tillage (NT), and subsoiling (SS). Bulk soil and dry-sieved aggregates were incubated at 15°C and 25°C at low, medium, and high moistures (i.e., 40%, 70%, and 100% water-holding capacity, respectively). Macro-aggregates (> 0.25 mm) had lower SOC mineralization relative to micro-aggregates (< 0.25 mm) across all soil temperatures, moistures, and depths (P < 0.01), which was attributed to their lower SOC quality (i.e., higher ratio of SOC to total nitrogen and lower ratio of dissolved organic carbon to SOC). Moreover, NT and SS promoted macro-aggregation relative to CT and RT, and thereby decreased mineralization (P < 0.001). However, Q10 was higher in macro-aggregates than in micro-aggregates at low and medium moistures. The Q10 was negatively correlated with the SOC quality in macro-aggregates (P < 0.05). The macroaggregate-associated SOC quality was lower under NT and SS than under CT and RT, which resulted in a greater Q10 under NT and SS at low and medium moistures, suggesting that NT and SS may accelerate SOC losses under global warming. Furthermore, increased soil moisture could lower Q10, and no differences among tillage practices were observed at high moisture levels (P > 0.05). Overall, our findings indicated that NT and SS decreased SOC mineralization but increased Q10 because of their large amounts of macro-aggregates with low SOC quality, and the improvement of Q10 was constrained by increasing soil moisture.