Operational mode and powdered activated carbon promoting syntrophic propionate oxidation during anaerobic digestion of complex organic substances.

Operational mode and powdered activated carbon (PAC) are key factors facilitating microbial syntrophy and interspecies electron transfer during anaerobic digestion, consequently benefiting process stability and efficient methanogenesis. In this study, continuous-flow reactor (CFR) and sequencing batch reactor (SBR), with and without the addition of PAC, respectively, were operated to examine their effects on system performance and methanogenic activity. Based on the cycle-test result, the PAC-amended CFR (CFRPAC) recorded both the highest methane yield (690.1 mL/L) and the maximum CH4 production rate (28.8 mL/(L·h)), while SBRs exhibited slow methanogenic rates. However, activity assays indicated that SBRs were beneficial for organics removal in batch experiments fed with peptone. Taxonomic and functional analysis confirmed that CFRs were optimal for proliferating oligotrophs (e.g., Geobacter) and SBRs were more suitable for copiotrophs (e.g., Desulfobulbus). Metagenomic analysis revealed that CFRs had efficient acetate metabolic pathways from propionate and ethanol, whereas SBRs did not, resulting in the buildup of propionate. Furthermore, Methanobacterium and Methanothrix were acclimated to the different operational conditions, while acetoclastic Methanosarcina and hydrogenotrophic Methanolinea were acclimated in SBRs (5.1-13.4%) and CFRs (0.3-1.7%), respectively. This study confirmed the enhancement of microbial syntrophy by the addition of PAC as well as the acclimation of electroactive bacteria (e.g., Geobacter) with complex organic substances.

A Review on Tetrabromobisphenol A: Human Biomonitoring, Toxicity, Detection and Treatment in the Environment.

Tetrabromobisphenol A (TBBPA) is a known endocrine disruptor employed in a range of consumer products and has been predominantly found in different environments through industrial processes and in human samples. In this review, we aimed to summarize published scientific evidence on human biomonitoring, toxic effects and mode of action of TBBPA in humans. Interestingly, an overview of various pretreatment methods, emerging detection methods, and treatment methods was elucidated. Studies on exposure routes in humans, a combination of detection methods, adsorbent-based treatments and degradation of TBBPA are in the preliminary phase and have several limitations. Therefore, in-depth studies on these subjects should be considered to enhance the accurate body load of non-invasive matrix, external exposure levels, optimal design of combined detection techniques, and degrading technology of TBBPA. Overall, this review will improve the scientific comprehension of TBBPA in humans as well as the environment, and the breakthrough for treating waste products containing TBBPA.

Using pH as a single indicator for evaluating/controlling nitritation systems under influence of major operational parameters.

This study focused on using pH as a single indicator to evaluate/control the performance of the nitritation system under the influence of three major operational parameters, and a total of fifteen batch tests were conducted. Results indicated that there were important interactions among different operational parameters and pH in the nitritation system; it was possible to propose the optimal nitritation operation scheme to compensate for negative changes in operational parameters. The optimal carbon to nitrogen (C/N) ratio was kept at 2.0 to ensure efficient removal of ammonium. The reaction time was the lowest (150 min) with the temperature = 20 °C, C/N = 0, and sludge/water ratio = 1:1. However, the C/N ratio could be adjusted to close to zero by reducing the temperature to about 10 °C, weakening the heterotrophic bacteria, and supplying sufficient biomass. The C/N ratio and sludge/water ratio could also be set at 4.0 and 1:3 respectively to deal with the impact of low temperature and organic matter. Results of this study might be useful to explain the optimal conditions and process control schemes with pH as a single indicator.

Start-up of Anammox systems with different biochar amendment: Process characteristics and microbial community.

As the 'go-to' process when it comes to biological nitrogen removal from wastewaters in recent years, the Anammox process has undergone lots of investigations in order to optimize its performance. In evaluating the effect of distinct biochar types at different concentrations on the Anammox startup process, as well as analyze their corresponding influence on the microbial community structure, three additives (coconut, peach, and bamboo) at either 5%, 10%, or 15% respectively were amended in various Anammox EGSB setups. (i). The 5% coconut biochar amendment resulted in the fastest startup of 46 days with an average ammonium removal efficiency of 96% whereas the control setup took 69 days. Thus, a more robust and cost effective Anammox process could be realized on an industrial scale. (ii) The Illumina high-throughput sequencing of the collected sludge samples indicated that the amendment with distinct biochar resulted in varied prevailing microbial communities in the respective setups. (iii) Proteobacteria was the dominant microbial community. (iv) However, two Anammox bacteria species, Candidatus Brocadia and Candidatus Jettenia were identified, with relative abundances of 0-4.72% and 0-6.23% respectively. The results from this study illustrate the correlation between Anammox reactor performance (startup and nitrogen removal efficiency), type and concentration of biochar amendment employed, as well as microbial community succession.