Chemical oxygen demand reduction in coffee wastewater through chemical flocculation and advanced oxidation processes

The removal of the natural organic matter present in coffee processing wastewater through chemical coagulation-flocculation and advanced oxidation processes （AOP） had been studied. The effectiveness of the removal of natural organic matter using commercial flocculants and UV/H202, UV/O3 and UV/H2O2/O3 processes was determined under acidic conditions. For each of these processes, different operational conditions were explored to optimize the treatment efficiency of the coffee wastewater. Coffee wastewater is characterized by a high chemical oxygen demand （COD） and low total suspended solids. The outcomes of coffee wastewater treatment using coagulation-flocculation and photodegradation processes were assessed in terms of reduction of COD, color, and turbidity. It was found that a reduction in COD of 67% could be realized when the coffee wastewater was treated by chemical coagulation-flocculation with lime and coagulant T-1. When coffee wastewater was treated by coagulation-flocculation in combination with UV/H2O2, a COD reduction of 86% was achieved, although only after prolonged UV irradiation. Of the three advanced oxidation processes considered, UV/H2O2, UV/O3 and UV/H2O2/O3, we found that the treatment with UV/H2O2/O3 was the most effective, with an efficiency of color, turbidity and further COD removal of 87%, when applied to the flocculated coffee wastewater.

On-Line Measurement of the Chemical Oxygen Demand in Wastewater in a Pulp and Paper Mill Using Near Infrared Spectroscopy

Although near infrared (NIR) spectroscopy has been evaluated for numerous applications, the number of actual on-line or even on-site industrial applications seems to be very limited. In the present paper, the attempts to produce online predictions of the chemical oxygen demand (COD) in wastewater from a pulp and paper mill using NIR spectroscopy are described. The task was perceived as very challenging, but with a root mean square error of prediction of 149 mg/l, roughly corresponding to 1/10 of the studied concentration interval, this attempt was deemed as successful. This result was obtained by using partial least squares model regression, interpolated reference values for calibration purposes, and by evenly distributing the calibration data in the concentration space. This work may also represent the first industrial application of online COD measurements in wastewater using NIR spectroscopy.

Environmental capacity of chemical oxygen demand in the Bohai Sea: modeling and calculation

A three-dimensional advection-diffusion model coupled with the degradation process is established for describing the transport of chemical oxygen demand (COD). Comparison of the simulated distribution of COD at the surface in the Bohai Sea in August, 2001 with field observations, shows that the model simulates the dataset reasonably well. The Laizhou Bay, Bohai Bay, and Liaodong Bay were contaminated heavily near shore. Based on the optimal discharge flux method, the Environmental Capacity (EC) and allocated capacities of COD in the Bohai Sea are calculated. For seawater of Grades I to IV of the Chinese National Standard, the ECs of COD in the Bohai Sea were 77×104 t/a, 116×104 t/a, 154×104 t/a and 193×104 t/a, respectively. The Huanghe (Yellow) River pollutant discharge accounted for the largest percentage of COD at 14.3%, followed by that of from the Liugu River (11.5%), and other nine local rivers below 10%. The COD level in 2005 was worse than that of Grade II seawater and was beyond the environmental capacity. In average, 35% COD reduction is called to meet the standard of Grade I seawater.

PVDF/PVA共混膜的制备及其在去除污水COD中的应用

以聚乙烯醇(PVA)、聚偏氟乙烯(PVDF)为原料,聚乙烯吡咯烷酮为溶剂,制备了PVDF/PVA共混膜。将该膜应用于膜生物反应器处理污水,测试化学需氧量(COD)去除率和膜的使用性能。结果表明:膜的水通量随PVA加入量的增加而逐渐增加,在牵伸比为1.7时,膜的水通量达到最大值;平板膜用清水清洗后,膜的水通量恢复率较高,膜的运行周期经第一次清洗后下降了18 h,经第二次和第三次清洗后,膜的运行周期基本稳定在6~8 h,COD去除率高于90%,表明该膜具有良好的使用性能。

近红外光谱的水体污染指标COD定量预测模型

针对传统化学需氧量(chemical oxygen demand, COD)检测存在检测成本高、耗时、易造成二次污染,以及现有检测模型泛化性较差等不足,难以满足水环境实时监测需求的问题,提出基于近红外光谱技术的COD快速无损定量预测模型.实验结果表明,本模型在污水COD光谱数据集上的预测性能,相较于传统机器学习算法和现有其他深度学习算法更优.测试的决定系数(R^(2))和均方根误差(E_(RMS))分别达到0.992 1和27.47 mg·L^(-1),模型卷积层的输出特征可解释性强,能有效表征关键波长点.该预测模型为实际水体COD含量快速检测提供一种新的方法.

污水中化学需氧量(COD)与浊度的关系

【目的】研究某采油管理区生活污水处理站出水样品中化学需氧量与浊度之间的关系,提出便捷、快速判断污水水质的方式,为该处理站运营人员提供管理依据。【方法】使用快速测定仪,对2023年8月份不同日期,在该采油管理区生活污水处理站出口处采取的16个水样的化学需氧量与浊度进行检测,并使用最小二乘法对检测数据进行整理、分析。【结果】结果表明,该采油管理区生活污水处理站出水水样中化学需氧量与浊度存在线性正相关关系,线性方程为y=0.247 1x-4.848 8,线性回归判定系数R2=0.931 5(即化学需氧量与浊度具有较高的相关性)。【结论】可以通过简单易测的浊度来表征该采油管理区生活污水处理站出水中的化学需氧量。

污水处理厂水质检测中化学需氧量(COD)测定的手工分析法和仪器法对比

化学需氧量是污水处理厂进、出水水质检测中重要的常规参数之一,主要反映水体受有机物污染程度以及污水处理厂处理效果。随着有机物对水体的污染日益严重,污水中化学需氧量的测定也越来越受到重视,对测定结果的要求也越来越高。本文依据标准《HJ 828—2017水质化学需氧量的测定重铬酸盐法》要求,通过采用两种浓度范围4个有证标准物质对比了手工法和仪器法在化学需氧量测定中的准确度和精密度,并通过测定污水处理厂进、出水水样的化学需氧量而比较了两种测定方法的相对偏差。

COD Removal Efficiencies of Some Aromatic Compounds in Supercritical Water Oxidation

Some aromatic compounds, phenol, aniline and nitrobenzene, were oxidized in supercritical water. It was experimentally found that the chemical oxygen demand (COD) removal efficiency of these organic compounds can achieve a high level more than 90% in a short residence time at temperatures high enough. As temperature, pressure and residence time increase, the COD removal efficiencies of the organic compounds would all increase. It is also found that temperature and residence time offer greater influences on the oxidation process than pressure. The difficulty in oxidizing these three compounds is in the order of nitrobenzene ＞ aniline ＞ Phenol. In addition, it is extremely difficult to oxidize aniline and nitrobenzene to CO2 and H2O at the temperature lower than 873.15 K and 923.15 K, respectively. Only at the temperature higher than 873.15 K and 923.15 K, respectively, the COD removal efficiencies of 90% of aniline and nitrobenzene can be achieved.

Effects of Urechis unicinctus Juveniles on Chemical Characteristics of Organically Contaminated Coastal Sediment

Biological activities of marine benthos such as burrowing and feeding may change sediment characteristics.We conducted three experiments to examine the potential of using juveniles of a spoon worm Urechis unicinctus to improve the quality of organically contaminated coastal sediment.Sediment samples were collected from a site that was heavily contaminated with organic matter (Seonso) and two sites that were clean (Myo-do,Dolsan-do).Urechis juveniles,obtained by artificial fertilization and cultured in the laboratory,were introduced to the sediment (weight 3 kg,depth 10 cm) at a density of 500 individuals per aquarium (length 50 cm,width 35 cm,height 30 cm) (Experiment 1),or at densities ranging from 100 to 900 individuals per beaker (Experiment 2).To examine how sediment contamination can be modified by the effects of Urechis,500 individuals (per aquarium) were exposed to the Seonso contaminated sediment that had been mixed with 0-100% clean sand (Experiment 3).Each experiment lasted two months and sediment samples were collected every 15 d to determine the several indexes of sediment quality,which included acid volatile sulfide (AVS),chemical oxygen demand (COD) and total ignition loss (TIL).In Experiment 1,the existence of Urechis did not result in significant changes in quality indexes in the sediments collected from Myo-do,Dolsan-do.However,AVS,COD and TIL of the Seonso sediment all decreased significantly after co-incubation with Urechis juveniles for 30 to 45 d.Experiment 2 showed that a density of at least 300 juveniles per beaker was necessary to significantly reduce all three quality indexes,and the magnitude of reduction was positively correlated with juvenile density.Experiment 3 revealed that Urechis juveniles were effective in reducing the AVS,COD and TIL of the Seonso sediment that had been mixed with 60%,80%,and 80% of clean sand,respectively.The results of the present study therefore indicated that juveniles of this spoon worm have the potential to be used to improve the quality of organically contaminated sediment in coastal waters.

A New Spectrophotometric Method for Measuring COD of Seawater

This research studied a new spectrophotometric method for measuring the chemical oxygen demand （COD） of seawater. In this method, the COD was measured using a spectrophotometer instead of titrating with sodium thiosuiphate. The measuring wavelength was selected to be 470 nm, and the COD of three standard glucose solutions （COD = 0.5, 1.5 and 2.5 mgL^-1, respectively） and two seawater samples （from the South Yellow Sea and Jiaozhou Bay） were measured using the spectrophotometric method and titrimetric method respectively. The results showed that the spectrophotometric method was somewhat better than the titrimetric method. The relative standard deviation （RSD） of the spectrophotometric method was less than 2.7%, and the recovery of seawater samples ranged from 96.3% to 103.8%. In addition, the spectrophotometric method has other advantages such as expeditiousness, operation simplicity, analysis automatization, etc. Therefore the spectrophotometric method can be used to measure the COD of seawater with satisfactory results.

Disruption of biofilms from sewage pipes under physical and chemical conditioning

Biofilms grown inside two sewage collecting pipes located in industrial and residential areas are studied. Bacterial biomass inside three layers of biofilms was evaluated. Biofilm cohesion under different mixing rate and ionic strength was also investigated. Effects of physical and chemical parameters in the biofilms were evaluated by monitoring turbidity, chemical and biochemical oxygen demands. Extracted organic matter from biofilms was partitioned to polar, aromatic and saturated fractions using activated silica column chromatography. Results revealed that bacterial biomass growth depending on biofilm thickness and stratification. The most loaded stratum in bacteria/biomass was the sewage-biofilm interface stratum that represented 51% of the total bacteria/biomass. Stirring rate and ionic strength of mono- and bivalent salts showed a major influence in biofilm disruption. The stirring time enhanced the exchange dynamic and matter capture between biofilm fragments at the critical stirring rate 90 r/min. Sodium chloride showed the dispersing effect on biofilms in suspension, and decreased the BOD5 （biochemical oxygen demand） beyond the physiological salt concentration.

高COD_(Cr)煤矿矿井水臭氧氧化处理研究

为研究臭氧对煤矿矿井水中有机污染物的氧化去除性能,首先采用浸渍法以活性炭为载体制备了固载不同金属的催化剂,接着以COD_(Cr)为指标,考察了臭氧发生器电流、反应时间、催化剂种类、催化剂用量及使用次数对臭氧催化性能的影响。研究结果表明,所制备的催化剂比表面积可以达到912m^(2)/g,而且孔道分布均匀。催化剂的加入可以加快臭氧氧化过程,不同催化剂催化效果顺序如下:Co基>Ni基>Fe基>Zn基>Cu基。在催化氧化过程中加入Co基催化剂,可将COD_(Cr)从135.5 mg/L降低至5 mg/L以下。所制备的催化剂具有良好的重复使用性能,重复使用100次之后,依然保持有良好的催化效果。

重铬酸盐滴定法测定COD的影响因素研究

消解酸度、滴定酸度、还原性离子、消解时间等是影响重铬酸钾滴定法测定水中化学需氧量(COD)的重要因素。本文对这些影响因素开展研究,结果表明,消解酸度从50%(v/v)减少至30%,COD的测定值降低了35%~57%。氯离子的氧化产物为氯气,但采取0.025 mol/L的重铬酸盐时不能被完全氧化;铵离子单独存在时对测定COD值无贡献,但与氯离子共存时有贡献;碘离子则无此现象。

废液再生型COD_(Cr)分析仪的研制及试验方法研究

针对重铬酸钾法检测水中化学需氧量(COD)产生的废液会造成环境污染的问题,设计并开发了一款可实现COD废液再生及循环利用的新型COD_(Cr)分析仪(CODet-5000型)。首先,通过向COD_(Cr)废液中加入氧化剂来氧化Cr^(3+),以提高Cr^(6+)的浓度、减小空白的吸光度。然后,采用蒸馏浓缩的方式提高废液的酸度,并过滤不溶性物质。最后,将得到的再生液作为COD_(Cr)分析仪测量所需的消解液循环使用,从而实现环境零污染。试验结果表明,该分析仪测量时具有较好的重复性和稳定性,所得数据示值误差在允许范围内。该分析仪的研制为常规COD_(Cr)分析仪实现废液循环利用、环境友好等目标提供了参考,并在环境监测仪表开发领域有着十分重要的意义,具有广阔的应用前景和市场潜力。

掺杂碳酸钙污泥生物炭去除废水中化学需氧量(COD)的实验研究

通过在污泥生物炭中添加不同含量的碳酸钙(CaCO_(3)),不同碳酸钙掺量污泥生物炭(Sludge biochar of calcium carbonate,SBC-Ca)在相同条件下得到制备,对其去除废水中化学需氧量(chemical oxygen demand,COD)的效果进行了评估。结果表明:CaCO_(3)比例为9%的污泥生物炭为最佳掺量;通过正交试验,最佳设计组合为A_(1)B_(2)C_(1)D_(3)E_(1),即吸附时间为60min,生物炭投加量为4.0g/L,pH6.0,温度为25℃,COD初始质量浓度为689.09mg/L;在最佳碳酸钙掺量下,SBC-Ca对废水中COD的去除量为166.08mg/g,去除率高达97.83%;比表面积和孔径分析显示SBC-Ca比表面积为39.86m^(2)/g,中孔量较多;红外光谱图表明含有-OH、C=O、C-O、Si-H等官能团;X射线衍射(X-Ray diffraction,XRD)谱图和扫描电子显微镜(scanning electron microscope,SEM)图显示SBC-Ca负载了CaCO_(3)。

典型重金属离子对SBR脱氮工艺及COD去除的影响研究进展

氮是目前导致水体富营养化的主要污染物质,而化学需氧量(COD)是体现水体中有机物污染情况的主要指标。近年来,SBR工艺作为一种应用广泛的污水处理工艺,在生物脱氮技术中也备受关注。实际含氮废水中,通常含有一定量的重金属,包括Zn、Cu和Ni等。这些重金属的存在,会抑制微生物的代谢能力,严重影响氮和COD的去除。选取含氮废水中的3种典型重金属离子(Cu^(2+)、Zn^(2+)和Ni^(2+)),进行了其对SBR工艺中脱氮效能的相关影响研究。研究结果表明:在较低质量浓度情况下,Cu^(2+)、Zn^(2+)和Ni^(2+)3种典型重金属离子对脱氮及COD的去除有一定的促进作用;在高质量浓度情况下,对脱氮及COD去除会产生抑制作用,且随质量浓度的增加而抑制作用增强。

表面活性剂与纳米颗粒协同稳定Pickering有机硅乳液的制备及其应用性能

针对目前有机硅平滑剂乳液往往存在分散稳定性差或高剂量表面活性剂引起的应用性能降低等问题,以聚丙烯酸异辛酯的共聚物胶乳(PEHA)为Pickering颗粒,协同表面活性剂,用于制备“油/水”Pickering有机硅乳液,并将其用于织物后整理。考察了PEHA粒径、表面亲水改性及PEHA质量分数对有机硅乳液分散稳定性的影响,通过对整理残液化学需氧量(COD)和整理织物表面摩擦因数的研究,考察了表面活性剂与Pickering纳米颗粒协同稳定对有机硅乳液应用性能的影响。结果表明:PEHA颗粒吸附在有机硅液滴的表面,形成机械阻隔,提升有机硅乳液的分散稳定性,180 nm的PEHA颗粒的稳定效率最佳,90 nm时的稳定效率最差;表面亲水改性能显著提高PEHA稳定乳液的效率,在质量分数仅为10%时,即可实现乳液稳定;最佳稳定方案可使表面活性剂质量分数降低60%以上;浸轧整理织物时,相比表面活性剂独自稳定的体系,Pickering体系吸附织物效率更高,整理后残液的COD值降低63%,整理织物表面静、动摩擦因数分别降低至0.51与0.49,即“Pickering/表面活性剂”协同稳定有机硅乳液具有良好的应用性能。

基于近红外光谱法的废水COD、BOD_5、pH的快速测量

收集了城市生活污水处理厂和养殖废水200个样品,以4cm-1的分辨率,分别用2mm和10mm样品池,用透射法采集800～2500nm谱区的光谱数据,采用偏最小二乘法(PLS)回归建立了废水的生化需氧量(BOD5)、化学需氧量(COD)和pH的预测模型.该模型的BOD5、COD和pH的预测值与参考值的校正相关系数分别为0.763、0.975、0.966,校正标准误差分别为27.7mg.L-1、19.9mg.L-1、0.165,预测相关系数分别为0.6939、0.945、0.927,预测标准误差分别为37.9mg.L-1、29.4mg.L-1、0.208.实验结果表明,近红外光谱技术可成为特定废水多指标快速检测的新手段.

油田污水处理工艺中COD的去除研究进展

概述了油田污水的组成特点,并从近年来聚合物驱油和三元复合驱油产生污水带来的新问题出发,阐述了油田污水处理的难点所在。同时对当前油田污水处理工艺流程特点、实际工艺中存在的不足等作了比较,得出当前油田污水处理过程中工艺流程的选择标准和目标。重点对工艺处理中的絮凝沉降、生化处理以及膜法处理等不同的工艺流程中COD的去除进行了研究,通过比较各种方法得出在油田污水处理中利用生化法和膜处理方法的有机结合将是油田污水处理的主要发展方向。同时对当前油田污水处理中亟待需要解决的问题作了进一步表述。

对黄河泥沙有机质的溶解特性和降解特性的研究——再论黄河水的COD值不能真实反映其污染状况

对黄河自潼关至三门峡至花园口河段泥沙中有机质的含量、组成、溶解特性和降解特性及对河水COD值与泥沙有机质的关系问题进行了研究 .查明了 :1)黄河泥沙中的有机质主要富集于 <5 μm的细颗粒物中 ;2 )这一段黄河水中溶解态有机质在总有机质中的比例非汛期为 2 0 %— 2 5 % ,汛期为 5 %— 10 % ;3)黄河泥沙中的有机质 75 %— 80 %以上是既不能为酸也不能为碱所萃取的胡敏素物质 ;4 )在黄河水中可被生化降解的有机质只占总有机质的 1%— 3% ;5 )目前在黄河清洁河段测得的COD值经常高达数十、数百、甚至上千mg L ,几乎等同于河水泥沙含量与泥沙中有机质含量的乘积 .研究结果表明 ,黄河泥沙中的有机质是稳定性极好的天然腐殖质类物质 ,它们在COD监测方法规定的高温、强酸性和强氧化剂条件下可以被氧化 ,构成黄河COD值的主体 ,但在实际自然条件下氧化过程极为缓慢和有限 ,不会对水体产生污染危害 ,不能将其与通常概念上的耗氧性有机污染物混为一谈 .测得后未经泥沙有机质背景值校正的COD值不是评价河流污染程度的恰当的水质指标 ,应寻找更好的水质参数来反映和评价黄河水的有机污染状况 .