Shifts in microbial community structure and diversity in a MBR combined with worm reactors treating synthetic wastewater

The chemical oxygen demand (COD) and NH₃-N removal, membrane fouling, sludge characteristics and microbial community structure in a membrane bioreactor (MBR) coupled with worm reactors (SSBWR) were evaluated for 210 days. The obtained results were compared to those from a conventional MBR (C-MBR) operated in parallel. The results indicated that the combined MBR (S-MBR) achieved higher COD and NH₃-N removal efficiency, slower increase in membrane fouling, better sludge settleability and higher activities of the related enzymes in the activated sludge. Denaturing gradient gel electrophoresis was used to analyze the microbial community structures in the C-MBR and the S-MBR. The microbial community structure in the S-MBR was more diverse than that in the C-MBR. Additionally, the slow-growing microbes such as Saprospiraceae, Actinomyces, Frankia, Clostridium, Comamonas, Pseudomonas, Dechloromonas and Flavobacterium were enriched in the S-MBR, further accounting for the sludge reduction, membrane fouling alleviation and wastewater treatment.     

Performance and microbial community of a membrane bioreactor system——Treating wastewater from ethanol fermentation of food waste

In this study, a lab-scale biological anaerobic/anaerobic/anoxic/membrane bioreactor(A_-~3MBR) was designed to treat wastewater from the ethanol fermentation of food waste,a promising way for the disposal of food waste and reclamation of resources. The 454 pyrosequencing technique was used to investigate the composition of the microbial community in the treatment system. The system yielded a stable effluent concentration of chemical oxygen demand(202 ± 23 mg/L), total nitrogen(62.1 ± 7.1 mg/L), ammonia(0.3 ±0.13 mg/L) and total phosphorus(8.3 ± 0.9 mg/L), and the reactors played different roles in specific pollutant removal. The exploration of the microbial community in the system revealed that:(1) the microbial diversity of anaerobic reactors A_1 and A_2, in which organic pollutants were massively degraded, was much higher than that in anoxic A_3 and aerobic MBR;(2) although the community composition in each reactor was quite different, bacteria assigned to the classes Clostridia, Bacteroidia, and Synergistia were important and common microorganisms for organic pollutant degradation in the anaerobic units, and bacteria from Alphaproteobacteria and Betaproteobacteria were the dominant microbial population in A_3 and MBR;(3) the taxon identification indicated that Arcobacter in the anaerobic reactors and Thauera in the anoxic reactor were two representative genera in the biological process. Our results proved that the biological A_-~3MBR process is an alternative technique for treating wastewater from food waste.     

Simultaneous removal of Cu(II) and Cr(VI) by Mg–Al–Cl layered double hydroxide and mechanism insight

Mg–Al–Cl layered double hydroxide (Cl-LDH) was prepared to simultaneously remove Cu(II) and Cr(VI) from aqueous solution. The coexisting Cu(II) (20 mg/L) and Cr(VI) (40 mg/L) were completely removed within 30 min by Cl-LDH in a dosage of 2.0 g/L; the removal rate of Cu(II) was accelerated in the presence of Cr(VI). Moreover, compared with the adsorption of single Cu(II) or Cr(VI), the adsorption capacities of Cl-LDH for Cu(II) and Cr(VI) can be improved by 81.05% and 49.56%, respectively, in the case of coexisting Cu(II) (200 mg/L) and Cr(VI) (400 mg/L). The affecting factors (such as solution initial pH, adsorbent dosage, and contact time) have been systematically investigated. Besides, the changes of pH values and the concentrations of Mg²⁺ and Al³⁺ in relevant solutions were monitored. To get the underlying mechanism, the Cl-LDH samples before and after adsorption were thoroughly characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. On the basis of these analyses, a possible mechanism was proposed. The coadsorption process involves anion exchange of Cr(VI) with Cl⁻ in Cl-LDH interlayer, isomorphic substitution of Mg²⁺ with Cu²⁺, formation of Cu₂Cl(OH)₃ precipitation, and the adsorption of Cr(VI) by Cu₂Cl(OH)₃. This work provides a new insight into simultaneous removal of heavy metal cations and anions from wastewater by Cl-LDH.     

Research on the degradation mechanism of pyridine in drinking water by dielectric barrier discharge

Pyridine, an important chemical raw material, is widely used in industry, for example in textiles,leather, printing, dyeing, etc. In this research, a dielectric barrier discharge(DBD) system was developed to remove pyridine, as a representative type of nitrogen heterocyclic compound in drinking water. First, the influence of the active species inhibitors tertiary butanol alcohol(TBA),HCO_3~-, and CO_3~(2-)on the degradation rate of pyridine was investigated to verify the existence of active species produced by the strong ionization discharge in the system. The intermediate and final products generated in the degradation process of pyridine were confirmed and analyzed through a series of analytical techniques, including liquid chromatography–mass spectrometry(LC–MS), high performance liquid chromatography(HPLC), ion chromatography(IC), total organic carbon(TOC) analysis, ultraviolet(UV) spectroscopy, etc. The results showed that the degradation of pyridine was mainly due to the strong oxidizing power of ozone and hydroxyl radical produced by the DBD system. Several intermediate products including 3-hydroxyl pyridine, fumaric acid, 2, 3-dihydroxypyridine, and oxalic acid were detected. Nitrogen was removed from the pyridine molecule to form nitrate. Through analysis of the degradation mechanism of pyridine, the oxidation pathway was deduced. The study provided a theoretical and experimental basis for the application of DBD strong ionization discharge in treatment of nitrogen heterocyclic compounds in drinking water.     

Simulated reaction of formaldehyde and ambient atmospheric particulate matter using a chamber

The reaction of HCHO with Beijing winter's real ambient particulate matter(PM) inside a 3.3 m~3 Teflon Chamber was conducted in this study. NO_2, O_3 and H_2O gases were removed from the ambient aerosol before entering into the chamber. The decays of HCHO were monitored(acetylacetone spectrophotometry method) during the reactions at different PM number concentrations(N_a) and relative humidities(RHs), and the formed particulate formate was detected by IC and XPS techniques. The results showed that when RH was10%–15%, the decay rate of HCHO in the chamber was higher with the existence of PM from relatively clean days(with number concentration(N_a) 200,000 particle/L, 0.35–22.5 μm)compared to dirty days(N_a 200,000 particle/L, 0.35–22.5 μm). When RH increased to 30%–45%, PM can hardly have significant influences on the decay of HCHO. The formations of formate on the reacted PM were consistent with the HCHO decay rates at different ambient PM N_aand RH conditions. This is a first study related to the "real" ambient PM reacted with HCHO and suggested that in the clean and low RH days, PM could be an effective medium for the conversion of HCHO to formate.     

不同主体功能定位的县域空间功能区划研究

文章通过判别分析法,尝试构建一套针对不同主体功能定位县通用的指标体系,以反映社会经济发展状况、生态环境保护重要性、国土空间开发支撑条件。通过在广西10个不同主体功能定位县的实践应用,将县域空间划分为城镇空间、农业空间和生态空间,重点开发区、农产品主产区、重点生态功能区的城镇空间分别小于30%、20%和10%,农产品主产区的农业空间和重点生态功能区的生态空间均大于50%。研究成果为全省范围推广县域空间功能区划提供了科学依据。     

某钢铁企业颗粒物无组织排放核算与监测对比分析

以济南东部老工业区一家大型钢铁企业为例,通过前期调研和排放系数核算出颗粒物(TSP)排放总量,再运用公式计算出厂区周边不同距离颗粒物(TSP)的落地浓度。将该落地浓度与厂区周边颗粒物(TSP)的监测值进行对比分析,充分印证了连续点源扩散的高斯模式的准确性和可行性。随着气流经过该厂区,对比上下风向监测点位颗粒物(TSP)浓度迅速升高(增大1.04倍),下风向颗粒物(TSP)浓度超出二级标准1.32倍;颗粒物(TSP)的落地浓度在厂区不同距离上的浓度变化明显,从0.1到10 km其落地浓度稀释了约3 500倍,距离>4 km时,无组织排放的颗粒物(TSP)对周围空气质量直接影响有限。     

美国市政污水处理排放标准制定对中国的启示

在概述美国市政污水处理排放标准制度体系的基础上,介绍了其制定基于技术的排放限值和基于水质的排放限值的方法,阐述了其制定的科学性,并指出了中国市政污水处理排放标准中存在的相应问题。最后,根据美国制定排放标准限值的经验,对我国污水处理排放标准进行了思考,并提出了科学制定排放标准的方法和建议。     

燃煤电厂烟塔合一排烟风洞试验与数值模拟对比分析

近年来,燃煤电厂烟塔合一烟气排烟对近距离环境影响的不确定性,使其在国内的推广过程受到一定限制。准确判断烟塔合一排烟的环境影响,对于我国现有燃煤电厂烟气污染物的排放有着巨大的工程价值和明显的现实意义。利用国家环境保护某重点实验室中风洞试验平台,对燃煤电厂烟塔合一烟气污染物在近距离的扩散和传输行为,进行物理风洞试验以及数值模拟计算,并进行对比分析。结果表明:德国Austal2000模式的浓度预测并不精确;数值风洞也有其差异性,而物理风洞的结果在很大程度上符合现有的理论及国内工程实际。     

厌氧发酵处理庆大霉素菌渣的可行性及条件优化

采用厌氧发酵处理庆大霉素菌渣,考察了含固率、接种比、接种污泥、发酵底物等因素对庆大霉素菌渣厌氧发酵的影响,并用累积净甲烷产量衡量庆大霉素菌渣进行厌氧发酵的可行性及发酵程度。试验结果证实了庆大霉素菌渣进行厌氧发酵的可行性,其中含固率和接种比对发酵的影响较大,最佳条件为含固率5%,接种比1/3;对比试验所用3种接种污泥,发现接种某造纸厂污水处理IC反应器的厌氧颗粒污泥效果最优,在最优含固率和接种比的条件下,累积净产甲烷量为28.21 m3/t;此外,试验还证实,采用不同菌渣的联合发酵表现出了明显的协同作用,在最优条件下,庆大霉素菌渣与林可霉素菌渣按1∶2的比例联合发酵的产甲烷量可达到37.5 m3/t。