Stabilization of Cd-, Pb-, Cu- and Zn-contaminated calcareous agricultural soil using red mud: a field experiment

Red mud (RM) was used to remediate heavy metal-contaminated soils. Experiments with two different dosages of RM added to soils were carried out in this study. It was found that soil pH increased 0.3 and 0.5 unit with the dosage of 3 and 5% (wt%), respectively. At the dosage of 5%, the highest stabilization efficiencies for Cd, Pb, Cu and Zn reached 67.95, 64.21, 43.73 and 63.73%, respectively. The addition of RM obviously transferred Cd from the exchangeable fraction to the residual fraction. Meanwhile, in comparison with the control (no RM added), it reduced 24.38, 49.20, 19.42 and 8.89% of Cd, Pb, Cu and Zn in wheat grains at the RM addition dosage of 5%, respectively. At the same time, the yield of wheat grains increased 17.81 and 24.66% at the RM addition dosage of 3 and 5%, respectively. Finally, the addition of RM did not change the soil bacterial community. These results indicate that RM has a great potential in stabilizing heavy metals in calcareous agricultural soils.

     

The temporal changes of the concentration level of typical toxic organics in the river sediments around Beijing

In this study, the current situation of five types of toxic organics and endocrine disrupters in the sediments of rivers around Beijing, i.e., polycyclic aromatic hydrocarbons (PAHs), phthalic acid esters (PAEs), organic chlorinated pesticides (OCPs), estrogens (Es), and bisphenol A (BPA), which included 56 contaminants, was analyzed and compared with that registered by the historical literatures. The ecological risks were also assessed. The total concentration of PAHs, PAEs, OCPs, Es, and BPA ranged from 232.5 ng·g^–1 to 5429.7 ng·g^–1, 2047.2 ng·g^–1 to 18051.5 ng·g^–1, 4.5 ng·g^–1 to 11.7 ng·g^–1, 18.1 ng·g^–1 to 105.2 ng·g^–1, and 36.3 ng·g^–1 to 69.6 ng·g^–1, respectively. Among these five types of organic compounds, the concentration levels of PAHs and OCPs have decreased significantly in the last ten years, while those of PAEs and Es had an upward trend compared with the previous studies. BPA still remained at a moderately high level, as it was ten years ago. The risks of the PAEs in all of the sample sites, and fluoranthene, benzo[a]anthrene, and benzo[a]pyrene in the Wenyu River sediment, were relatively high. These results supplemented the database of toxic organics’ concentration levels in the sediments of Beijing rivers.

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Removal of nitrogen from wastewaters by anaerobic ammonium oxidation (ANAMMOX) using granules in upflow reactors

Nitrogen pollution of waters has sometimes caused severe eutrophication, leading to the death of fishes and most aquatic life. There is therefore a need for efficient and cost-effective methods to remove nitrogen from ammonium-rich wastewaters. Anaerobic ammonium oxidation (ANAMMOX) is a promising process to remove nitrogen because this process directly oxidizes ammonium (NH₄ ⁺) to dinitrogen gas (N₂) under anoxic condition. Nonetheless, a challenge of this process is that chemolithoautotrophic Anammox bacteria grow slowly at the beginning, thus resulting in low Anammox biomass and instability of reactors. Such issues can be overcome by granulation of the Anammox sludge. Here, we review the characteristics of the Anammox bacteria, and the formation, structure and flotation of Anammox granules under high hydraulic loadings. We also evaluate the performances of full-scale granular Anammox processes. The major points are: 1) Anammox bacteria secrete a large amount of extracellular polymeric substances (EPS), up to 415 mg g^?1 of volatile suspended solids (VSS), containing many hydrophobic functional groups that facilitate biomass granulation. 2) Granulation enhances the sludge settling property and retention time, which contributes to the extremely high nitrogen removal rate of 77 kg m^?3 d^?1 of Anammox upflow reactors. 3) Flotation of Anammox granules frequently occurs under nitrogen removal rate higher than 10 kg m^?3 d^?1, which is mainly due to the overproduction of EPS under high hydraulic conditions.     

Effect of pH on the sonochemical degradation of organic pollutants

An increasing number of organic compounds are manufactured, consumed, and discarded every year. Incomplete destruction of these compounds in wastewater treatment plants leads to pollution of natural waters, posing great health and ecological concerns. Ultrasound, as an emerging advanced oxidation technology, can quickly and effectively degrade organic pollutants in waters. To improve removal efficiency of organic pollutants in an ultrasonic system, operational parameters, especially pH, have been frequently evaluated and optimized. This review show that pH-induced changes in volatility, hydrophobicity and Coulombic force between the target compound and cavitation bubbles leads to higher degradation at acidic pH for most compounds. In addition, pH also changes free radical formation and reactivity in water during sonication, thereby altering degradation kinetics of target compounds. However, the influence of pH is not always consistent for various organic pollutants covering a broad range of physicochemical properties and reactivities. A systematic investigation on the pH effect is necessary to elucidate how pH alters cavitation bubble dynamics and collapse, radical yield and reactivity, distribution of target compounds in the vicinity of cavitation bubbles, water matrices transformation, and ultimately the degradation kinetics of organic pollutants. This first systematic review provides valuable insight into the pH effects on organic pollutant sonolysis, helps to improve our mechanistic understanding of the sonochemical system, and sheds light on future application of ultrasound in water engineering.     

Enhancement of extracellular Cr(VI) reduction for anammox recovery using hydrazine: performance,pathways, and mechanism

● N₂H₄ addition enhanced and recovered anammox performance under Cr(VI) stress. ● N₂H₄ accelerated electron transfer of Cr(VI) reduction for detoxification. ● N₂H₄ enhanced anammox metabolism for activity recovery from Cr(VI) inhibition. ● Extracellular Cr(VI) reduction to less toxic Cr(III) was the dominant mechanism. The hexavalent chromium (Cr(VI)) would frequently impose inhibition to anaerobic ammonium oxidation (anammox) process, hindering the efficiency of nitrogen removal in wastewater treatment. Hydrazine (N₂H₄), which is an intermediate product of anammox, participates in intracellular metabolism and extracellular Cr(VI) reduction. However, the roles of N₂H₄-induced intracellular metabolism and extracellular reduction in nitrogen removal under Cr(VI) stress remain unclear. The addition of 3.67 mg/L of N₂H₄ increased the anammox activity by 17%. As an intermediate, N₂H₄ enhanced anammox metabolism by increasing the heme c content and electron transfer system activity. As a reductant, N₂H₄ accelerated the reduction of c-Cyts-mediated extracellular Cr(VI) to the less toxic Cr(III). Extracellular Cr(III) accounts for 74% of the total Cr in a Cr(VI)-stressed anammox consortia. These findings highlight that N₂H₄-induced extracellular Cr(VI) reduction is the dominant mechanism for the survival of anammox consortia. We also found that N₂H₄ increased the production of extracellular polymeric substances to sequester excessive Cr(VI) and produced Cr(III). Taken together, the study findings suggest a potential strategy for enhancing nitrogen removal from ammonium-rich wastewater contaminated with Cr(VI).     

长沙地区O3污染潜势广义可加模型的季节分异性

基于长沙市2016—2019年臭氧（O₃）浓度的逐时监测资料以及该时段同时次的气象观测数据,首先利用相关性分析和方差膨胀因子相结合的方法排除了相对湿度、太阳辐射、气温、风速、气压之间存在多重共线性问题,进而构建了春、夏、秋、冬四季O₃日最大8 h滑动平均质量浓度（O₃-8 h）与上述气象因子的广义可加模型（GAMs）,分析了O₃污染潜势GAMs模型的季节分异特征。结果表明：①春、夏、秋、冬四季O₃与相对湿度、太阳辐射、气温、风速、气压各变量之间多呈现出非线性关系（自由度大于1）。②春、夏、秋、冬四季多变量GAMs模型方差解释率（IRV）分别为80.7%、60.2%、83.0%、81.4%,调整判定系数R²分别为0.795、0.564、0.819、0.795,即不同季节气象因子在GAMs模型中对O₃的解释能力存在显著差异,秋季最好,冬春季次之,夏季最差。③相对湿度、太阳辐射、气温是决定春、夏、秋、冬四季O₃浓度变化最重要的气象要素,但其重要性排序随季节有所变化,对应的太阳辐射的F统计值分别为140.841、36.606、14.16、46.377,相对湿度的F统计值分别为3.291、4.158、15.82、8.105,气温的F统计值分别为7.030、2.113、15.79、3.340。该结论揭示了气象因子对O₃演化影响的复杂性,并为后续O₃污染潜势的预报奠定了基础。     

Fe2O3添加对钛基SCR催化剂表面硫酸氢铵分解行为的影响规律

采用共沉淀法合成了TiO_2及TiO_2-Fe_2O_3载体,并对硫酸氢铵与上述载体之间的相互作用及硫酸氢铵的具体分解行为进行了研究.结果表明,催化剂载体表面含硫官能团主要以双齿硫酸盐的形式存在,含氮官能团以铵根离子的形式存在.当硫酸氢铵沉积于催化剂载体表面时,由于硫酸根离子具有较强的电负性,Ti原子及Fe原子处于电子缺失状态.对于TiO_2载体,硫酸根离子主要与Ti原子相连;而对于TiO_2-Fe_2O_3载体,Ti原子及Fe原子均为硫酸根离子主要的附着位点.采用热分析方法及原位红外对硫酸氢铵在TiO_2及TiO_2-Fe_2O_3载体表面的分解行为进行了研究,发现铁氧化物的添加显著促进了硫酸氢铵在低温区间内的分解行为;与铵根离子相比,硫酸根离子具有更高的热稳定性.催化剂稳定性测试结果表明,铁氧化物的添加显著提高了低温抗硫抗水性能,为实现低温SCR技术的工业应用提供了理论基础.     

Red mud-modified biochar reduces soil arsenic availability and changes bacterial composition

Environmental Chemistry Letters - Worldwide arsenic (As) contamination in soils induces pollution of surface and ground waters, reduces crop quality and yield, and threatens human health....     

炭素焙烧炉沥青烟静电除尘技术

针对炭素焙烧炉含尘低浓度高温沥青烟，优化设计方案，采用干式、湿式预处理和静电净化两级处理，先除去大粒径烟尘，降低烟尘温度，降低电阻率，后静电净化沥青烟。系统具有自动控制，节电节能，除尘效率高等特点。     

典型产业集聚区地下水优先控制污染物筛选

为明确地下水污染高风险区环境管控目标,快速识别优先控制污染物,于2022年以典型产业集聚区为研究对象,利用污染源产排污状况和地下水基础环境状况调查结果,将污染评价和环境风险相结合,优选污染源超标率、地下水环境污染等级、生物毒性参数和环境迁移转化参数作为筛选因子,利用层次分析法和综合分析法,计算各污染指标综合得分,建立筛选地下水优先控制污染物的方法体系。筛选结果显示,该产业集聚区的优先控制污染物相关指标包括：硝酸盐、耗氧量、石油类、总硬度、亚硝酸盐、镍、锌、硫酸盐、甲苯、氨氮等。筛选结果与园区主导行业产排污特征和地下水质量现状相符,具有一定的可靠性,可为科学、精准管控高风险区地下水质量提供依据。