A pilot-scale study of cryolite precipitation from high fluoride-containing wastewater in a reaction-separation integrated reactor

Fluoride removal by traditional precipitation generates huge amounts of a water-rich sludge with low quality, which has no commercial or industrial value. The present study evaluated the feasibility of recovering fluoride as low water content cryolite from industrial fluoride-containing wastewater. A novel pilot-scale reaction-separation integrated reactor was designed. The results showed that the seed retention time in the reactor was prolonged to strengthen the induced crystallization process. The particle size of cryolite increased with increasing seed retention time, which decreased the water content. The recovery rate of cryolite was above 75% under an influent fluoride concentration of 3500 mg/L, a reaction temperature of 50℃, and an influent flow of 40 L/hr. The cryolite products that precipitated from the reactor were small in volume, large in particle size, low in water content, high in crystal purity, and recyclable.     

Supercritical water oxidation of polyvinyl alcohol and desizing wastewater：Influence of NaOH on the organic decomposition

Polyvinyl alcohol is a refractory compound widely used in industry. Here we report supercritical water oxidation of polyvinyl alcohol solution and desizing wastewater with and without sodium hydroxide addition. However, it is difficult to implement complete degradation of organics even though polyvinyl alcohol can readily crack under supercritical water treatment. Sodium hydroxide had a significant catalytic effect during the supercritical water oxidation of polyvinyl alcohol. It appears that the OH ion participated in the C-C bond cleavage of polyvinyl alcohol molecules, the CO2-capture reaction and the neutralization of intermediate organic acids, promoting the overall reactions moving in the forward direction. Acetaldehyde was a typical intermediate product during reaction. For supercritical water oxidation of desizing wastewater, a high destruction rate (98.25%) based on total organic carbon was achieved. In addition, cases where initial wastewater was alkaline were favorable for supercritical water oxidation treatment, but salt precipitation and blockage issues arising during the process need to be taken into account seriously.     

Identification of key factors governing chemistry in groundwater near the water course recharged by reclaimed water at Miyun County, Northern China

Reclaimed water was successfully used to recover the dry Chaobai River in Northern China, but groundwater may be polluted. To ensure groundwater protection, it is therefore critical to identify the governing factors of groundwater chemistry. Samples of reclaimed water, river and groundwater were collected monthly at Chaobai River from January to September in 2010. Fifteen water parameters were analyzed. Two kinds of reclaimed water were different in type (Na-Ca-Mg-Cl-HCO3 or Na-Ca-Cl-HCO3 ) and concentration of nitrogen. The ionic concentration and type in river were similar to reclaimed water. Some shallow wells near the river bed had the same type (Na-Ca-Mg-Cl-HCO3 ) and high concentration as reclaimed water, but others were consistent with the deep wells (Ca-Mg-HCO3 ). Using cluster analysis, the 9 months were divided into two periods (dry and wet seasons), and all samples were grouped into several spatial clusters, indicating different controlling mechanisms. Principal component analysis and conventional ionic plots showed that calcium, magnesium and bicarbonate were controlled by water-rock interaction in all deep and some shallow wells. This included the dissolution of calcite and carbonate weathering. Sodium, potassium, chloride and sulfate in river and some shallow wells recharged by river were governed by evaporation crystallization and mixing of reclaimed water. But groundwater chemistry was not controlled by precipitation. During the infiltration of reclaimed water, cation exchange took place between (sodium, potassium) and (calcium, magnesium). Nitrification and denitrification both happened in most shallow groundwater, but only denitrification in deep groundwater.     

湄公河下游国家水质管理状况与区域合作前景

本文分析了老挝、缅甸、泰国、柬埔寨和越南等湄公河下游五国的水质状况及原因,通过汇总湄公河五国的水质管理法律法规及水质标准和介绍各国的水质管理措施,阐述了湄公河国家在水质管理方面做出的努力以及水质管理中存在的问题,并对湄公河国家在流域水质区域合作方面进行了展望。     

纳米Fe_3O_4/膨润土的制备、表征及光催化降解焦化废水

以铝柱撑膨润土负载纳米Fe_3O_4制备出性能良好的复合型催化剂。结合X射线粉末衍射(XRD)、扫描电镜(SEM)和比表面孔隙分析(BET)对催化剂的晶相、比表面积和粒度进行表征。负载的纳米Fe_3O_4粒径约为20～30nm,均匀分散到膨润土表面,未发生明显的团聚。在紫外光作用下用该催化剂对焦化厂二沉池出水进行深度处理。结果表明,在催化剂投加量为0.7 g/L,pH为2.5,温度40℃,H_2O_2初始浓度为17.6mmol/L的反应条件下,二沉池出水(化学需氧量COD=140mg/L,色度=400度)经催化氧化降解后,COD和色度可分别降低到54.44 mg/L和10度,达到国家工业再生用水水质标准GB/T 19923-2005(COD≤60 mg/L,色度≤30度)。催化剂重复使用4次时,废水COD和色度去除率保持稳定。     

浅谈环境空气自动监测站质控方式

采用标准样品检查、PM10采样流量检查和运行管理检查等方式,加强对云南省环境空气自动监测站的质量管理和质量控制,保证了仪器设备的可靠运行和监测数据准确有效。实践证明,这套检查方式操作简单、易于实施、效果较好。     

高校校园景观水体浮游植物调查与水质评价

对华侨大学厦门校区景观水体浮游植物群落结构和水质的理化指标进行了调查研究,结合生物监测和理化监测手段,基于浮游植物优势度、丰度和多样性指数的评价标准,对水体进行了生态评价。评价结果表明,水体受到一定程度的污染并出现富营养化现象。     

关于不锈钢酸洗废水处理的技术分析

随着社会经济的快速发展,不锈钢酸洗废水处理技术成为了当前的一项重要技术参数。本文旨在分析当前不锈钢酸洗废水的相关处理技术,从多种技术综合的应用出发,围绕当前工业发展的实际需要,多角度的分析不锈钢酸洗废水的技术,实现整体技术的全面运用。     

水中总氮空白的影响因素的探讨

本研究以水中总氮空白值为研究对象,不同厂家的过硫酸钾和不同试验用水条件下的总氮空白的变化规律。研究结果表明：无氨水和二次水蒸出来的总氮空白明显低于一次水蒸出来的总氮空白;这跟蒸馏水纯度有关系,一次水含有氨,所以消解时蒸馏水中的氨会被氧化,从而导致空白值偏高。同样有的厂家的过硫酸钾纯度不高,所以导致空白值高。     

宜昌市沮漳河流域当阳段水环境现状调查与评价

对宜昌市沮漳河流域当阳段的水环境进行了调查和评价。通过区域自然环境、社会经济发展、水体功能区、水环境容量等分析以及多个断面数据的监测,表明沮漳河流域当阳段水环境质量不能满足Ⅲ类水体功能区要求,主要超标因子为高锰酸盐指数、NHrN、BOD5、TP、石油类,主要受沿岸工业废水、生活污水及农业面源污染所致。