The impact of benzoic acid and lactic acid on the treatment efficiency and microbial community in the sulfur autotrophic denitrification process.

Nitrate poses a potential threat to aquatic ecosystems. This study focuses on the sulfur autotrophic denitrification mechanism in the process of water culture wastewater treatment, which has been successfully applied to the degradation of nitrogen in water culture farm effluents. However, the coexistence of organic acids in the treatment process is a common environmental challenge, significantly affecting the activity of denitrifying bacteria. This paper aims to explore the effects of adding benzoic acid and lactic acid on denitrification performance, organic acid removal rate, and microbial population abundance in sulfur autotrophic denitrification systems under optimal operating conditions, sulfur deficiency, and high hydraulic load. In experiments with 50 mg·L-1 of benzoic acid or lactic acid alone, the results show that benzoic acid and lactic acid have a stimulating effect on denitrification activity, with the stimulating effect significantly greater than the inhibitory effect. Under optimal operating conditions, the average denitrification rate of the system remained above 99%; under S/N = 1.5 conditions, the average denitrification rate increased from 88.34% to 91.93% and 85.91%; under HRT = 6 h conditions, the average denitrification rate increased from 75.25% to 97.79% and 96.58%. In addition, the addition of organic acids led to a decrease in microbial population abundance. At the phylum level, Proteobacteria has always been the dominant bacterial genus, and its relative abundance significantly increased after the addition of benzoic acid, from 40.2% to 61.5% and 62.4%. At the genus level, Thiobacillus, Sulfurimonas, Chryseobacterium, and Thermomonas maintained high population abundances under different conditions. PRACTITIONER POINTS: Employing autotrophic denitrification process for treating high-nitrate wastewater. Utilizing organic acids as external carbon sources. Denitrifying bacteria demonstrate high utilization efficiency towards organic acids. Organic acids promote denitrification more than they inhibit it. The promotion is manifested in the enhancement of activity and microbial abundance.

Acoustic emission characteristics of micro-discharges in initial pulsed PEO process on 60% SiCp/Al composite.

The initial discharge process of pulsed plasma electrolytic oxidation (PEO) on the 60% SiCp/2009 aluminum metal matrix composite (Al MMC) in silicate solution was monitored by acoustic emission (AE) technique. Parameters and correlations of AE signals on the Al MMC sample and under water were analyzed, and their generation mechanism was discussed. It was found that the peak amplitudes of AE signals and AE hits during the pulse time quickly increased with the increase of micro-discharge intensity, and the absolute energy of AE signals improved several orders of magnitude. Moreover, different from the peak amplitude, duration and rise time, the duration and count had a strong correlation. Elastic stress waves resulted from the microjet of plasma bubble collapse, the inner-surface friction inside discharge channel, the expansion-shrinkage process of plasma bubbles and micro-crack propagation during rapid solidification of melt are sources of AE signals on the Al MMC sample during the pulse time. However, the expansion-shrinkage process of plasma bubbles plays a key role in the generation of underwater AE signals. In the pause time of one pulse period, the bursting and moving of vapor bubbles result in weak AE signals. It is demonstrated that the AE technique can effectively characterize the features of micro-discharges within a pulse period.

In situ monitoring of initial plasma electrolytic oxidation process on 60 vol. % SiCp/2009 aluminum matrix composite by sound and vibration measurement techniques.

The initial discharge process of plasma electrolytic oxidation (PEO) on the 60 vol. % SiCP/2009 aluminum matrix composite in silicate solution was in situ monitored by sound and vibration measurement techniques. The underwater sound, airborne sound, and sample vibration signals were detected in the initial 120 s of the PEO process, and their generation mechanism was discussed. In terms of waveforms and spectrograms of the sound and vibration signals, the initial PEO process can be divided into five stages: conventional anodizing stage (I), glow discharge stage (Ⅱ), tiny spark discharge stage (Ⅲ), large spark discharge stage (Ⅳ), and strong spark discharge stage (Ⅴ). The sound and vibration signals during the PEO process are attributed to the evolution of bubbles, which are from the plasma discharge, electrochemical reactions, and vaporization of electrolyte under Joule heat. In stage I, these signals completely come from the bubbles produced by the evaporative electrolyte and electrochemical reactions. In stages Ⅱ-Ⅴ, the bubbles from the plasma discharge gradually become the main source of these signals with increasing discharge intensity. In addition, the spike peaks on the waveforms of these signals at stage Ⅴ are related to the strong discharge sparks. These results demonstrate that sound and vibration measurement techniques can effectively monitor the PEO discharge process.

Degradation of 2,4-dichlorophenol by cathodic microarc plasma electrolysis: characteristics and mechanisms.

In this work, we used cathodic microarc plasma electrolysis (CMPE) to degrade 2,4-dichlorophenol (2,4-DCP) in simulated wastewater. By investigating and comparing the removal efficiencies and chemical oxygen demand (COD) during the degradation process, higher bath voltage and alkaline condition were considered as more suitable for the 2,4-DCP decomposition. Higher initial 2,4-DCP concentration was attributed to the increase in the utilisation of the energy input. The plasma characteristics during CMPE were studied by optical emission spectroscopy (OES). It was found that the 2,4-DCP directly participated in the plasma discharge process. Furthermore, by studying the evolution of intermediate products at different experimental parameters, it was found that the existence of Cl- played an important role in the opening of benzene ring, which activated the ortho-substitutions of hydroxyl, meanwhile accelerated the p-substitutions. The instantaneous high temperature and high pressure and the Cl- that were generated and driven by cathodic plasma made the decomposition of 2,4-DCP much quicker.

Maggot protein ameliorates dextran sulphate sodium-induced ulcerative colitis in mice.

Ulcerative colitis (UC) is a common chronic remitting disease but without satisfactory treatment. Maggots are known as a traditional Chinese medicine named as 'wu gu chong'. The aim of the present study was to investigate the therapeutic effect of the maggot protein on dextran sulphate sodium (DSS)-induced colitis in C57BL/6 mice. In the present study, female C57BL/6 mice were given sterile water containing 3% DSS to establish the model of UC. Mice were randomly divided into five groups: control group (sterile water), model group (DSS), treatment group (DSS + maggot protein), mesalazine group (DSS + mesalazine), and maggot protein group (sterile water + maggot protein). The mental state, defecate traits, and changes in body weights were recorded daily. The disease activity index (DAI) as a disease severity criterion was calculated based on body weights and stool consistency and bleeding. All the mice were killed on the 12th day. Colon length, colon histological changes, and other inflammatory factors were analyzed and evaluated. The results showed that colitis models of mice were established successfully. Administration of maggot protein markedly suppressed the severity of UC compared with the DSS model group. Furthermore, maggot protein potently ameliorated DSS-induced weight loss, colon shortening, and colon histological injury. Moreover, the maggot protein exerted anti-inflammatory effects via inhibition of the activation of the nuclear factor κB (NFκB) signaling pathway. In summary, treatment by maggot protein was able to improve not only the symptoms of colitis, but also the microscopic inflammation in mice with DSS-induced colitis. The present study may have implications for developing an effective therapeutic strategy for inflammatory bowel diseases (IBDs).