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.

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.

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.

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。

Feasibility and advantage of biofilm-electrode reactor for phenol degradation

The new biofilm-electrode method was used for the phenol degradation, because of its low current requirement. The biofilm-electrode reactor consisted of immobilized degrading bacteria on Ti electrode as cathode and Ti/PbO2 electrode as anode. With the biofilmelectrode reactor in a divided electrolytic cell, the phenol degradation rate could achieve 100% at 18 h which was higher than using traditional methods, such as biological or electrochemical methods. Chemical oxygen demand （COD） removal rate of the biofilmelectrode reactor was also greater than that using biological and electrochemical method, and could reach 80% at 16 h. The results suggested that the biofilm-electrode reactor system can be used to treat wastewater with phenol.

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.

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.

Effects and mechanism of ozonation for degradation of sodium acetate in aqueous solution

The degradation efficiencies and mechanism of ozonation for the degradation of sodium acetate in aqueous solution were investigated under atmospheric pressure at room temperature （293 K）. The effects of the initial pH value, reaction time, and concentrations ofHCO3^-, CO3^2- , CaC12, and Ca（OH）2 on the removal rate of chemical oxygen demand （COD） were studied. The results indicated that ozonation obviously improved the degradation rate of sodium acetate when the pH value of the solution was not less than 8.5. A suitable long reaction time may be helpful in increasing the COD removal rate, and a removal rate of 36.36% can be obtained after a 30-minute treatment. The COD removal rate increased firstly and decreased subsequently with the increase of the HCOj concentration （from 0 to 200 mg/L）, and under the same experimental condition it reached the optimum 34.66% at the HCO3-^ concentration of 100 mg/L. The COD removal rate was 5.26% lower when the concentration of HCO3^- was 200 mg/L than when there was no HCO3^-. The COD removal rate decreased by 15.68% when the CO3^2- concentration increased from 0 to 200 mg/L. CO3^2- has a more obvious scavenging effect in inhibiting the formation of hydroxyl radicals than HCO3. CaC12 and Ca（OH）2 could increase the degradation efficiency of sodium acetate greatly, and the COD removal rates reached 65.73% and 83.46%, respectively, after a 30-minute treatment, 29.37% and 47.10% higher, was proved that the degradation of sodium acetate in the ozonation process followed the mechanismof oxidization with hydroxyl free radicals （.OH）.

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。

一种快速测定化学需氧量(COD)的方法

提出用混酸来代替单一酸测定废水中的化学需氧量(COD)含量的方法。采用混酸(硫酸∶磷酸=4∶1)、重铬酸钾反应体系,氧化反应时间由标准方法的2h缩短为15min,是原来的1/8。用两种方法分别测试了标准物质所配制的废水和实际废水,经t检验和相关性分析,两种测试方法间不存在显著性差异,相关系数为0.95,相关性良好,同时实验得出本方法的检测限为5.15mg/L。本方法由于具有反应时间短,节省药剂和电费等优点,具有一定的可行性。

重铬酸钾法测定COD存在问题及改进研究进展

肯定了传统的COD测定方法——重铬酸钾法的优点,指出了存在的不足和问题：耗时长、试剂用量大、耗水、耗电、费人工、排污严重、存在氯的干扰、贵金属的浪费。较为全面地叙述了对上述各问题改进的国内外研究进展,简单介绍了COD测定的几种新方法,指出了未来需要的是准确、快速、稳定、灵敏、价格合理、携带方便、无二次污染的环境友好型COD在线自动监测仪。

近红外光谱透射法测量废水化学需氧量(COD)的光程选择

在用近红外光谱法测量废水化学需氧量（COD）时,水是一个强干扰因素,如何选择合适的光程长以提高测量灵敏度,减少测量误差很重要.本文通过在傅里叶变换近红外光谱仪上用透射光谱法测量废水COD实验来讨论废水测量的光程选择.采集了60个养猪废水水样,分别用1mm、2mm、5mm和10mm的样品池作对比研究,用PLS回归建模,比较不同光程长对废水COD预测的效果,结果显示在800-1350nm谱区选用10mm的光程,在1350-2500nm谱区选用1mm或2mm的光程测量,使用双光程组合方法建模可以提高模型在800-2500nm谱区的预测性能.该光程组合方法对其它复杂组分的水溶液的近红外定量测量也具有一定的参考意义.

荧光光谱法检测水质COD时温度、浊度、 pH的影响分析

以COD标准液为研究对象,基于特定激发波长下的荧光发射光谱数据,采用化学计量学算法对水质COD进行了检测,分析了水的温度、浊度和pH的变化对发射光谱的影响,并对相关参数的影响进行了补偿校正。在此基础上建立了多参量共同作用时对水质COD预测模型的补偿校正方法。首先采用荧光光谱法对浓度范围为1～55 mg·L^(-1)水质化学需氧量(COD)标准溶液进行三维荧光光谱的采集,去除散射峰以后采用基于蚁群算法优化的偏最小二乘法(ACO-iPLS)对不同激发波长(Ex=255～285 nm,间隔为5 nm)下的荧光发射光谱(Em=275～450nm)数据进行特征提取并采用基于粒子群优化的最小二乘支持向量机算法(PSO-LSSVM)进行预测模型的建立。结果表明,不同激发波长下的荧光发射光谱数据模型的检验集决定系数R■在0.961 8～0.998 1范围内,当采用波长为Ex=270 nm的激发光作用时所激发出的荧光发射光谱数据所建模型的效果最优,其检验集决定系数R■=0.998 1,预测均方根误差RMSEP=0.348 3 mg·L^(-1)。其次,对温度、浊度、 pH对荧光光谱法检测水质COD的影响进行了分析,并给出了相应的补偿模型。结果表明,温度和浊度在检测水质COD时对荧光光谱的影响不可忽略,但通过建立补偿模型可以对其影响进行有效的补偿校正,温度补偿后荧光数据模型的整体平均偏差Bias=0.130 6 mg·L^(-1),经浊度补偿后可以很好的校正浊度变化对荧光光谱法检测水质COD的影响,而pH范围在4～12.3内变化时对荧光光谱的影响相对较小,因此可忽略。最后,结合单一影响因素的分析结果,对荧光光谱法检测水质COD时水体的多种环境因素(温度、浊度、 pH)共同作用的影响进行了分析。实验结果表明,忽略pH影响后,可以采用对温度和浊度同时补偿的方法对二者的影响进行有效的校正。该结果可为水质参数光学传感器在调试过程中抑制环境因素的影响提供参考。