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81.
Membrane based treatment processes are very effective in removing salt from wastewater, but are hindered by calcium scale deposit formation. This study investigates the feasibility of removing calcium from treated sewage wastewater using accelerated seeded precipitation. The rate of calcium removal was measured during bench scale batch mode seeded precipitation experiments at pH 9.5 using various quantities of calcium carbonate as seed material. The results indicate that accelerated seeded precipitation may be a feasible option for the decrease of calcium in reverse osmosis concentrate streams during the desalination of treated sewage wastewater for irrigation purposes, promising decreased incidence of scaling and the option to control the sodium adsorption ratio and nutritional properties of the desalted water. It was found that accelerated seeded precipitation of calcium from treated sewage wastewater was largely ineffective if carried out without pre-treatment of the wastewater. Evidence was presented that suggests that phosphate may be a major interfering substance for the seeded precipitation of calcium from this type of wastewater. A pH adjustment to 9.5 followed by a 1-h equilibration period was found to be an effective pre-treatment for the removal of interferences. Calcium carbonate seed addition at 10 g l−1 to wastewater that had been pre-treated in this way was found to result in calcium precipitation from supersaturated level at 60 mg l−1 to saturated level at 5 mg l−1. Approximately 90% reduction of the calcium level occurred 5 min after seed addition. A further 10% reduction was achieved 30 min after seed addition. 相似文献
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基于长江流域区域1956-2011年50年气象资料和同期太平洋海温资料,采用Z指数、EOF、REOF、SVD分析等方法,探讨长江流域春季和夏季旱涝特征及其旱涝事件与极端海温异常之间的关联性,得出以下结论。1REOF的Z指数春夏季节旱涝空间分区特征显示,春季前6个模态的累计方差贡献率能够达到61.2%,收敛速度较平缓,夏季前6个模态累积方差贡献率更低,只有52.1%。2前冬太平洋海温的变化与长江流域旱涝的态势呈显著相关关系,春季海温场与长江流域旱涝Z指数场的SVD第一模态显示,长江流域的东北区的旱涝与厄尔尼诺显著相关,当赤道东太平洋海温升高,西太平洋海温降低时,长江流域东北地区偏涝,而长江流域的西部地区偏旱,反之亦然。3夏季海温场与长江流域旱涝Z指数场的SVD第一模态,表明太平洋海温分布主要呈现南北向的分布,当赤道中东太平洋海温偏高,北太平洋海温偏低时,长江流域夏季中部地区偏涝。反之亦然。第二模态,全球海温呈现厄尔尼诺类型的分布,中东太平洋是负相关,而在西太平洋为显著负相关。 相似文献
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2013年12月1-9日成都及周边城市出现了一次较为严重的区域大气污染过程,重污染区域集中在成都市,其API值最高达到225,首要污染物为PM2.5。对成都地区PM2.5源解析可得出本次污染过程是以机动车尾气和煤烟污染的混合型污染过程,贡献比重之和为42.8%。同时探讨了研究期间造成污染持续累积的相关因素:高空500hPa的大气环流形势处于弱高压前部以下层气流为主;主导风向西南风和东南风,平均风速分别为1.46m/s和0.99m/s,无降水,气温日较差较往年偏高7.1℃的气象条件;高湿及"双逆温"效应的大气结构均不利于污染物扩散。研究表明逆温强度变化与颗粒物浓度的消长具有显著的滞后一致性。研究结果可为成都平原地区发生重污染过程的预警预报及污染防治提供理论依据和研究参考。 相似文献
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Heavy-metal contamination is a major concern, as excessive heavy metals produce environmental pollution, and the cumulative effects of heavy metals in vivo pose a major threat to human health. There is an urgent need for a rapid, sensitive, and efficient method for detecting heavy metals. Quantum dots (QDs) are in the category of semiconductor nanocrystals whose radii are less than or close to the exciton Bohr radius. QDs possess a potential in the biological and medical fields to function as a new type of fluorescent marker, because of their unique and tunable photophysical properties, which include broad excitation spectrum, narrow emission spectrum, tunable emission wavelengths, and negligible photobleaching. In recent years, QDs made significant progress in quantitative analysis by providing a new approach for determination of chemical content analysis. The aim of this study was to review the research progress of QD detection of heavy metals in water and consider the challenges and future outlook for QD-based sensors for heavy-metal ions. 相似文献
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Min Xu Zirui Liu Bo Hu Guangxuan Yan Jianan Zou Shuman Zhao Jingxiang Zhou Xianhui Liu Xueping Zheng Xiaoyan Zhang Jing Cao Mengshuang Guan Yirong Lv Yanyun Zhang 《环境科学学报(英文版)》2022,34(5):265-276
Luoyang is a typical heavy industrial city in China, with a coal-dominated energy structure and serious air pollution. Following the implementation of the clean air actions, the physicochemical characteristics and sources of PM2.5 have changed. A comprehensive study of PM2.5 was conducted from October 16, 2019 to January 23, 2020 to evaluate the effectiveness of previous control measures and further to provide theory basis for more effective policies in the future. Results showed that the aerosol pollution in Luoyang in autumn and winter is still serious with the average concentration of 91.1 μg/m3, although a large reduction (46.9%) since 2014. With the contribution of nitrate increased from 12.5% to 25.1% and sulfate decreased from 16.7% to 11.2%, aerosol pollution has changed from sulfate-dominate to nitrate-dominate. High NO3−/SO42− ratio and the increasing of NO3−/SO42− ratio with the aggravation of pollution indicating vehicle exhaust playing an increasingly important role in PM2.5 pollution in Luoyang, especially in the haze processes. Secondary inorganic ions contributed significantly to the enhancement of PM2.5 during the pollution period. The high value of Cl−/Na+ and EC concentration indicate coal combustion in Luoyang is still serious. The top three contributor sources were secondary inorganic aerosols (33.3%), coal combustion (13.6%), and industrial emissions (13.4%). Close-range transport from the western and northeastern directions were more important factors in air pollution in Luoyang during the sampling period. It is necessary to strengthen the control of coal combustion and reduce vehicle emissions in future policies. 相似文献
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