Catalytic Oxidation of Benzene over Atomic Active Site AgNi/BCN Catalysts at Room Temperature.

Benzene is the typical volatile organic compound (VOC) of indoor and outdoor air pollution, which harms human health and the environment. Due to the stability of their aromatic structure, the catalytic oxidation of benzene rings in an environment without an external energy input is difficult. In this study, the efficient degradation of benzene at room temperature was achieved by constructing Ag and Ni bimetallic active site catalysts (AgNi/BCN) supported on boron-carbon-nitrogen aerogel. The atomic-scale Ag and Ni are uniformly dispersed on the catalyst surface and form Ag/Ni-C/N bonds with C and N, which were conducive to the catalytic oxidation of benzene at room temperature. Further catalytic reaction mechanisms indicate that benzene reacted with ·OH to produce R·, which reacted with O2 to regenerate ·OH. Under the strong oxidation of ·OH, benzene was oxidized to form alcohols, carboxylic acids, and eventually CO2 and H2O. This study not only significantly reduces the energy consumption of VOC catalytic oxidation, but also improves the safety of VOC treatment, providing new ideas for the low energy consumption and green development of VOC treatment.

Effect of flow fluctuation on water pollution in drinking water distribution systems.

The detachment of biofilm caused by changes in hydraulic conditions is an essential reason for the pollution of water in the drinking water distribution system (DWDS). In this research, the effect of flow fluctuation on bulk water quality was studied. The turbidity, iron concentration, manganese concentration, the total number of bacteria, biodegradable dissolved organic carbon (BDOC), bacterial community structure, and pathogenic genes in bacteria of bulk water were analyzed. The results indicate that the detachment of biofilm caused by fluctuant flow and reverse flow (especially instant reverse flow) can lead to the pollution of water. Throughout the entire experimental period, the turbidity under fluctuant flow velocity is 4.92%∼49.44% higher than that under other flow velocities. BDOC concentration is 5.68%∼53.99% higher than that under low and high flow velocities. The flow fluctuation increases bacterial regrowth potential (BRP) and reduces the biological stability of the bulk water. Low flow velocity is more conducive to the expression of pathogenic functional genes. In the short term, the water quality under low flow velocity is the best. Nevertheless, in a long-term operation (about seven days later), the water quality under high flow velocity is better than that under other flow velocities. This research brings new knowledge about the fluctuant hydraulic conditions on the bulk water quality within the DWDS and provides data support for stable drinking water distribution.

Application of UV-vis absorption spectrum to test the membrane integrity of Membrane bioreactor (MBR).

In this work, UV-vis absorption spectrum of the membrane integrity analysis based on slopes of log-transformed absorbance spectra, differential absorbance spectroscopy (DAS), and absorption coefficient α(254) were studied at different number of breakage fibers and filtration times. Moreover, we analyze the influence of Fe2+ and Ca2+concentration on UV spectrum detection results. Cluster analysis and the change ratio Rs were used to determine the dissolved organic matter (DOM) leakage stages. As a result, the correlation coefficient between slope280-350 value and the number of breakage fibers is 0.901. Seven gaussian bands were successfully model from the DAS, and A4 (312 nm), A5 (339 nm), A6 (367 nm) were chosen to indicate the extent of breakage fiber. Peak 4(A4) is minimally affected by ions concentration. The α(254) could be used as a good indicator for detecting industrial wastewater treatment process which correlation coefficient between the number of breakage fibers is 0.955. The DOM leakage process was divided into three stages which were bulk leakage stage, development stage and stabilization stage. The UV-vis absorption spectrum can effectively detect the membrane integrity more sensitive than particle counter and three analyse methods are suitable for different substance in feed water.

Microbial fuel cell and membrane bioreactor coupling system: recent trends.

Membrane bioreactor (MBR) and microbial fuel cell (MFC) are new technologies based on microbial process. MBR takes separation process as the core to achieve the high efficient separation and enrichment the beneficiation of microbes during the biological treatment. MFC is a novel technology based on electrochemical process to realize the mutual conversion between biomass energy and electric energy, in order to solve the problems of serious membrane fouling and low efficiency of denitrification in membrane bioreactor, the low power generation efficiency, and unavailability of bioelectric energy of MFC. In recent years, MFC-MBR coupling system emerged. It can effectively mitigate the membrane fouling and reduce the excess sludge production. Simultaneously, the electricity can be used effectively. The new coupling system has good prospects for development. In this paper, we summarized the research progresses of the two kinds of coupling systems in recent years and analyzed the coupling structure and forms. Based on the above, the future development fields of the MFC-MBR coupling system were prospected.

Micro-bubbles enhanced breakage warning for hollow fiber membrane integrity with a low-cost real-time monitoring device.

A low-cost device was developed to monitor the integrity of hollow fiber membrane by real-time online detecting and measuring air bubbles in the permeate flow. When a breakage occurs in the fiber membrane system, air bubbles will find their ways to enter the permeate flow. The monitoring device consists of two pairs of platinum probes attached to a pipe, along which the permeate flows. Membrane's breakage was identified by the voltage changes between the two pairs of probes when air bubbles in the permeate touch them. There was no addition of any other chemicals or materials into the system that would jeopardize final products of the membrane process. Experimental results showed that the voltage signal changes before and after a breach of membrane were obvious in the normal operation conditions. The smallest diameter of the bubbles that can be detected by the monitoring device was 50 µm, which was captured and identified with a high-speed camera. Furthermore, the sensitivity of device with two pairs of probes improved by 5~9% over that with one pair of probes. Finally, cost of the proposed device was roughly estimated only about 70 US dollars and the detection result was highly consistent with that obtained with the prevailing particle counters of several thousand US dollars.