Shift in microorganism and functional gene abundance during completely autotrophic nitrogen removal over nitrite (CANON) process.

Nitrification-denitrification process has failed to meet wastewater treatment standards. The completely autotrophic nitrite removal (CANON) process has a huge advantage in the field of low carbon/nitrogen wastewater nitrogen removal. However, slow start-up and system instability limit its applications. In this study, the time of the start-up CANON process was reduced by using bio-rope as loading materials. The establishing of graded dissolved oxygen improved the stability of the CANON process and enhanced the stratification effect between functional microorganisms. Microbial community structure and the abundance of nitrogen removal functional genes are also analyzed. The results showed that the CANON process was initiated within 75 days in the complete absence of anaerobic ammonium oxidizing bacteria (AnAOB) inoculation. The ammonium and nitrogen removal efficiencies of CANON process reached to 94.45% and 80.76% respectively. The results also showed that the relative abundance of nitrogen removal bacterial in the biofilm gradually increases with the dissolved oxygen content in the solution decreases. In contrast, the relative abundance of ammonia oxidizing bacteria was positively correlated with the dissolved oxygen content in the solution. The relative abundance of g__Candidatus_Brocadia in biofilm was 15.56%, and while g__Nitrosomonas was just 0.6613%. Metagenomic analysis showed that g__Candidatus_Brocadia also contributes 66.37% to the partial-nitrification functional gene Hao (K10535). This study presented a new idea for the cooperation between partial-nitrification and anammox, which improved the nitrogen removal system stability.

A review of the recent progress in biotrickling filters: packing materials, gases, micro-organisms, and CFD.

Organic pollutants in the air have serious consequences on both human health and the environment. Among the various methods for removing organic pollution gas, biotrickling filters (BTFs) are becoming more and more popular due to their cost-effective advantages. BTF can effectively degrade organic pollutants without producing secondary pollutants. In the current research on the removal of organic pollutants by BTF, improving the performance of BTF has always been a research hotspot. Researchers have conducted studies from different aspects to improve the removal performance of BTF for organic pollutants. Including research on the performance of BTF using different packing materials, research on the removal of various mixed pollutant gases by BTF, research on microbial communities in BTF, and other studies that can improve the performance of BTF. Moreover, computational fluid dynamics (CFD) was introduced to study the microscopic process of BTF removal of organic pollutants. CFD is a simulation tool widely used in aerospace, automotive, and industrial production. In the study of BTF removal of organic pollutants, CFD can simulate the fluid movement, mass transfer process, and biodegradation process in BTF in a visual way. This review will summarize the development of BTFs from four aspects: packing materials, mixed gases, micro-organisms, and CFD, in order to provide a reference and direction for the future optimization of BTFs.

Experimental study on the effects of H(2)O on PCDD/Fs formation by de novo synthesis in carbon/CuCl(2) model system.

The effects of H(2)O vapor on de novo synthesis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and biphenyls (PCB) were investigated at two levels (none and 10 vol.%) in various model systems containing five different carbons, CuCl(2), and quartz, exposed to a flow of 10% O(2)/N(2) at 300 degrees Celsius. The influence of H(2)O was studied on (1) speciation and behavior of copper compounds, (2) catalytic oxidation of carbons of distinct reactivity, and (3) formation of organic chlorine compounds, with the aim to investigate any effects on de novo synthesis. It is found that H(2)O converts CuCl(2) to CuCl(2) x CuO, and finally to CuO in a flow of 10% O(2)/N(2) at 300 degrees Celsius and that it decreases of organic chlorine (C-Cl) formation. When CuCl(2) is supported on carbon, the addition of H(2)O promotes the catalytic oxidation of this carbon. When CuCl(2) is supported on quartz, however, H(2)O inhibits carbon oxidation. A decrease in chlorination level of PCDD/Fs and PCBs with water addition is observed for all (six) model ashes; yet this addition affects the yields of PCDD/Fs and PCBs differently. Under the experimental conditions tested H(2)O does not react with Cu(2)Cl(2), which is the catalyst of carbon oxidation. On the basis of the experimental results, the following mechanism is proposed: conversion of CuCl(2) into CuO which is less reactive in de novo synthesis and promotion of catalytic oxidation of carbon by Cu(2)Cl(2).

Co-degradation with glucose of four surfactants, CTAB, Triton X-100, SDS and Rhamnolipid, in liquid culture media and compost matrix.

Strengthened biodegradation is one of the key means to treat surfactant pollution in environment, and microorganism and surfactant have significant effects on degradation. In this paper, co-degradation of CTAB, Triton X-100, SDS and rhamnolipid with glucose by Pseudomonas aeruginosa, Bacillus subtilis and compost microorganisms in liquid culture media, as well as the degradation of rhamnolipid in compost were investigated. The results showed that CTAB was recalcitrant to degrade by the three microorganisms and it also inhibited microorganisms from utilizing readily degradable carbon source. Non-ionic surfactant Triton X-100 could also hardly be degraded, but it was not toxic to microorganisms and would not inhibit the growth of the microorganisms. Anion surfactant SDS had no toxicity to microorganisms and could be co-degraded as carbon source with glucose. Biosurfactant rhamnolipid was a kind of particular surfactant, which had no toxicity and could be degraded by Bacillus subtilis and compost microorganisms, while it could not be utilized by its producing bacterium Pseudomonas aeruginosa. Among these three bacteria, the compost consortium had the strongest degradation capacity on the tested surfactants due to their microorganisms' diversity. In compost matrix rhamnolipid could be degraded during composting, but not preferentially utilized.

[Kinetic of pH control in anaerobic digestion of organic fraction of municipal solid waste in a batch reactor].

Using a material and ionization balance analysis of anaerobic digestion process, a kinetic model of pH control in a batch anaerobic digestion of organic fraction of municipal solid waste was established on the basis of substrate decay and microbial growth kinetics, and a corresponding computer soft ware was created. The optimal pH in different anaerobic digestion can be predicted by this model. Consequently the maximal methane production can be obtained in anaerobic system by controlling the pH in optimal value. Comparative experiments were conducted to validate the model. The experiments demonstrated that the methane production of anaerobic system under optimal pH was steadier than the same condition under uncontrolled pH, and the cumulative methane production had an average increment about 20%.