A new approach for chemical oxygen demand (COD) measurement at high salinity and low organic matter samples

Background, aim, and scope  

Chemical oxygen demand (COD) is used as a discharge standard parameter in wastewater treatment plant design, environmental modelling and many other applications. Chloride interference is an important problem of COD measurement for wastewaters containing low organic matter and high chloride concentrations. In case of chloride concentrations up to 2,000 mg/L, mercury sulphate addition at a ratio of 10:1 (HgSO₄:Cl⁻) can adequately mask the interference. When chloride concentration exceeds 2,000 mg/L, this ratio becomes ineffective to hinder the interference. At this point, it is proposed to use a greater and constant ratio of mercury sulphate addition. However, this application sometimes results in extra mercury sulphate addition which is not necessary. Even in some cases, greater addition of mercury sulphate alone is not a solution to erroneous measurement results. The purpose of the study is to determine optimum HgSO₄:Cl⁻ ratios according to the chloride concentrations of the samples and to show the importance of the strength of the digestion solution for the correct determination of the COD parameter.     

Organic-coated nanoparticulate zero valent iron for remediation of chemical oxygen demand (COD) and dissolved metals from tropical landfill leachate

The use of nanoparticulate zero valent iron (NZVI) in the treatment of inorganic contaminants in landfill leachate and polluted plumes has been the subject of many studies, especially in temperate, developed countries. However, NZVI’s potential for reduction of chemical oxygen demand (COD) and treatment of metal ion mixtures has not been explored in detail. We investigated the efficiency of NZVI synthesized in the presence of starch, mercaptoacetic, mercaptosuccinic, or mercaptopropenoic acid for the reduction of COD, nutrients, and metal ions from landfill leachate in tropical Sri Lanka. Synthesized NZVI were characterized with X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller. Of the samples tested, Starch-NZVI (S-NZVI) and mercaptoacetic-NZVI (MA-NZVI) performed well for treatment both COD and metal mixture. The removal percentages for COD, nitrate-nitrogen, and phosphate from S-NZVI were 50, 88, and 99 %, respectively. Heavy metal removal was higher in S-NZVI (>95 %) than others. MA-NZVI, its oxidation products, and functional groups of its coating showed the maximum removal amounts for both Cu (56.27 mg g^?1) and Zn (28.38 mg g^?1). All mercapto-NZVI showed well-stabilized nature under FTIR and XRD investigations. Therefore, we suggest mercapto acids as better agents to enhance the air stability for NZVI since chemically bonded thiol and carbonyl groups actively participation for stabilization process.     

流动注射-火焰原子吸收法快速测定水样化学需氧量

采用流动注射-火焰原子吸收法(FI-FAAS)测定水样化学需氧量.以KMnO4作氧化剂、葡萄糖作基准物质,在95 ℃反应,生成的Mn(Ⅱ)在线分离吸附于阳离子交换树脂微型柱上,用3 mol/L HCl洗脱后,送至火焰原子吸收检测器检测.在反应盘管长500 cm、反应时间30 s的条件下,测定化学需氧量的线性范围为8.00～200.00 mg/L,检出限为2.30 mg/L;采样频率为24次/h,Cl-质量浓度至100 mg/L无干扰,Mg2 质量浓度至1 000 mg/L无干扰;对50.00 mg/L的化学需氧量标样重复测定7次,相对标准偏差为3.37%.用该法测定河水、池塘水和轻度污染工业废水的化学需氧量,获得了与重铬酸盐法(标准方法)基本一致的测定结果.     

Biodegradation of aromatic hydrocarbons by Haloarchaea and their use for the reduction of the chemical oxygen demand of hypersaline petroleum produced water

Ten halophilic Archaea (Haloarchaea) strains able to degrade aromatic compounds were isolated from five hypersaline locations; salt marshes in the Uyuni salt flats in Bolivia, crystallizer ponds in Chile and Cabo Rojo (Puerto Rico), and sabkhas (salt flats) in the Persian Gulf (Saudi Arabia) and the Dead Sea (Israel and Jordan). Phylogenetic identification of the isolates was determined by 16S rRNA gene sequence analysis. The isolated Haloarchaea strains were able to grow on a mixture of benzoic acid, p-hydroxybenzoic acid, and salicylic acid (1.5 mM each) and a mixture of the polycyclic aromatic hydrocarbons, naphthalene, anthracene, phenanthrene, pyrene and benzo[a]anthracene (0.3 mM each). Evaluation of the extent of degradation of the mixed aromatic hydrocarbons demonstrated that the isolates could degrade these compounds in hypersaline media containing 20% NaCl. The strains were shown to reduce the COD of hypersaline crude oil reservoir produced waters significantly beyond that achieved using standard hydrogen peroxide treatment alone.     

无机陶瓷膜处理油田采出水

针对陶瓷膜在油田采出水处理过程中操作参数的选择及污染机理进行了研究。通过现场实验,分析了不同的操作参数对膜通量的影响,陶瓷膜对含油量及悬浮物的去除效果,膜阻力组成及膜污染清洗方法。实验结果表明,在确定出水水质达到低渗透油田注水水质A1级标准条件下,陶瓷膜过滤最佳操作条件为:跨膜压差0.16 MPa、温度50℃、膜面流速5.0 m/s。同时发现,NaOH和HNO3联合清洗有助于恢复膜通量。     

基于生化双膜工艺的油田采出水处理与资源化

针对胜利油田油井采出水处理负荷过大但锅炉用水短缺的问题,对油井采出水进行生化双膜工艺处理,处理后的产水用于锅炉给水,浓水用于低渗油田回注.开展了规模为200m3?d-1的中试实验,重点研究了超滤进水悬浮物与超滤膜污染的关系,考察了反渗透进水压力、进水温度对产水率、膜通量和透盐率的影响.结果表明:生化处理后的油田采出水中...     

Stochastic modeling of chemical oxygen demand transformations in gravity sewers.

Wastewater quality characteristics in terms of biomass, its substrates, and the corresponding kinetic and stoichiometric parameters were determined based on 109 wastewater samples originating from five different campaigns in four different sewer networks. Quality parameters were determined by model calibration of measured wastewater oxygen uptake rates applying a model that describes the aerobic breakdown of wastewater organic matter. Thereafter, the distributions of the parameters were analyzed. Two of the five datasets were obtained at the upstream end of a five-km-long, intercepting gravity sewer. For each of these upstream wastewater samples, downstream samples were collected with a delay corresponding to the residence time. The upstream distributions of the wastewater composition were used as boundary conditions for a Monte Carlo simulation. The calculated downstream distributions were compared to the measured downstream distributions and good agreement was observed.     

Incomplete oxidation of ethylenediaminetetraacetic acid in chemical oxygen demand analysis.

Ethylenediaminetetraacetic acid (EDTA) was found to incompletely oxidize in chemical oxygen demand (COD) analysis, leading to incorrect COD values for water samples containing relatively large amounts of EDTA. The degree of oxidation depended on the oxidant used, its concentration, and the length of digestion. The COD concentrations measured using COD vials with a potassium dichromate concentration of 0.10 N (after dilution by sample and sulfuric acid) were near theoretical oxygen demand values. However, COD measured with dichromate concentrations of 0.010 N and 0.0022 N were 30 to 40% lower than theoretical oxygen demand values. Similarly, lower COD values were observed with manganic sulfate as oxidant at 0.011 N. Extended digestion yielded somewhat higher COD values, suggesting incomplete and slower oxidation of EDTA, as a result of lower oxidant concentrations. For wastewater in which EDTA is a large fraction of COD, accurate COD measurement may not be achieved with methods using dichromate concentrations less than 0.1 N.     

破乳剂对模拟油田二元复合驱采出水的作用机理

针对破乳剂成分与结构对油田采出水破乳脱稳的影响机制仍不明确的问题,依据新疆油田二元驱实际采出水组成配制模拟二元复合驱采出水,考察有机破乳剂种类和结构及无机电解质对其破乳脱稳的影响.结果表明,合成有机破乳剂的起始剂种类对破乳脱稳的影响较大,起始剂含量具有一定影响,而EO/PO比的影响相对较小.PAC和Al2(SO4)3的破乳脱稳效果最好,投加量500 mg/L时均能将剩余含油量降低到10 mg/L以下;而FeSO4和ZnSO4次之,NH4Cl较差.破乳剂通过电性中和及与HPAM形成的协同絮凝作用,促进了油滴的碰撞聚并,达到了较好的破乳脱稳效果.     

紫外-近红外光谱法测定废水COD含量

针对传统方法测定化学需氧量（COD）药剂成本高、检测效率低、连续监测难、废液二次污染等问题,基于现有的紫外-可见光与近红外光谱法测量COD技术,研究了综合利用紫外光谱与近红外光谱中的信息来预测废水中COD含量的可行性。实验采集了100个工厂现场水样,每一水样分成两组：一组测其190~2 300 nm波长范围的光谱数据,另一组利用传统方法测其COD,并把该方法得到的结果作为标定该水样光谱的标准值,对水样光谱用偏最小二乘法（PLS）建立废水样的COD预测模型。经验证预测值与实测值的相关度为0.967 1,验证标准误差值为24.8 mg·L-1,具有较好的预测效果。     

Analyzing the uncorrected error of dilution water demand for the dilution biochemical oxygen demand method.

Dilution water demand (DWD) can cause a positive error when the dilution biochemical oxygen demand (BOD) method is used. Dilution water demand may be attributed to oxidation of organic impurities in the dilution water and nitrification of ammonia added as a nutrient. To minimize the error associated with these sources, the standard BOD method requires that DWD be less than 0.2 mg/L in 5 days and does not allow correction for DWD when calculating test results. This study derives a set of theoretical equations to analyze the uncorrected errors with and without seeding. The authors concluded that DWD can be completely corrected if seeded dilution water is used for the sample dilution. When seeding individual bottles, the uncorrected error approaches 8.3 to approximately 8.8% at a 5-day depletion of 2 mg/L for a typical secondary effluent. Tests without seeding show an almost 1% higher uncorrected error than seeded tests. The analysis also suggests that these errors can be effectively reduced to less than 3% when the 5-day depletion approaches 6 mg/L. even for 5-day biochemical oxygen demand concentrations exceeding I x 10(4) mg/L. Further analysis indicates that, if not inhibited, the ammonium added to dilution water as a nutrient may contribute additional error due to nitrification.     

生物法/人工湿地工艺处理采油废水及其生态毒性削减研究

采用2种生物法/人工湿地工艺(水解酸化/好氧/人工湿地工艺和水解酸化/人工湿地(进水区强化曝气)工艺)处理胜利油田某联合处理站经隔油、混凝处理的采油废水,并运用发光细菌技术研究采油废水在处理过程中的生态毒性削减规律.研究结果表明,在水解酸化段水力停留时间(HRT)为20 h,好氧段HRT为10 h,人工湿地HRT为2 d的工况下,水解酸化/好氧/人工湿地工艺与水解酸化/人工湿地(进水区强化曝气)工艺的出水水质均能满足COD≤80 mg/L、NH_4~+-N≤15 mg/L的处理要求.发光细菌法试验结果表明,经隔油、混凝处理后的采油废水属高毒性废水,再经水解酸化/人工湿地(进水区强化曝气)工艺处理后生态毒性大幅削减,出水生态毒性降至低毒.     

平板陶瓷膜处理油田采出水运行控制优化及膜污染机理

陶瓷膜凭借其机械强度高、化学稳定性好等优点,近年来在油田采出水处理领域得到了广泛的应用。针对陶瓷膜处理油田采出水膜污染控制这一核心问题,采用小试实验与模型分析相结合的方法,深入开展了陶瓷膜处理系统运行控制优化的研究,结合微观表征,阐明了陶瓷膜处理油田采出水膜污染机理。结果表明,陶瓷膜处理油田采出水最佳运行控制工况为：初始膜通量80 L·(m²·h)⁻¹,过滤时间10 min,反冲洗时间30 s,曝气强度3 L·min⁻¹;此条件下陶瓷膜可保持平均膜通量27.82 L·(m²·h)⁻¹。原水和污染层的表征结果表明,胺类或酰胺类、烃类、羧酸类、芳香族、醇类等有机物化合物是造成陶瓷膜污染的主要有机物,Si、Fe、Ca、Mg、Ba等无机盐离子也是膜污染的重要组成部分;过滤过程中膜孔内阻力和凝胶层阻力对陶瓷膜膜污染形成起主导作用。     

Determination of Schulze equation for chemical oxygen demand reduction using stabilized landfill refuse media

Three columns each with 770 cm2 of surface area and 60-105 cm effective depth were set up for this study. These columns were filled with compacted, stabilized refuse. High-strength brewery wastewaters were uniformly trickled down the medium. Overall, 16 runs with various organic loadings were tested and the results demonstrated that the stabilized refuse had excellent capability in removing chemical oxygen demand (COD). The COD removal efficiency reached 95% at a depth of 60 cm at Q = 8 L/day for the initial COD of approximately 6000 mg/L and the efficiency increased to >99% at a depth of 90 cm (organic loading of 0.69 kg/m3/day). As would be expected, the filter performance is a function of flow rate, influent COD concentration, and bed depth. The Schulze equation is able to predict the COD removal performance well. The variations of pH, oxidation reduction potential, and volatile fatty acids indicated that the acidogenesis reaction occurred in the upper layers.     

不同密度絮体的实际耗氧需求分析

通过选取不同污水处理厂及实验室改进A2/O反应器曝气池内的活性污泥进行实验,研究了不同密度污泥的耗氧需求以及其节能特性。研究发现,实验所用污泥密度分别为1.004 1、1.003 3、1.001 7、1.001 3和1.000 6 g·mL-1时,其实际耗氧量与理论需氧量比值（Cresp/Craw）分别为0.42、0.61、1.38、1.44和1.69,即当污泥密度越大,则污泥在去除污染物质的过程耗氧量越小,节能性能越好,且其节能程度与微生物用于自身基础代谢的内源呼吸速率比例有关,内源呼吸速率比例越小,污泥越节能。另外通过对不同密度活性污泥进行短期冲击实验,研究发现在非稳态环境中,密度小的污泥用于基础代谢的能量多,而用于生长代谢的少,其稳定性能较好。     

回灌对垃圾填埋初期渗滤液化学需氧量的影响

通过模拟柱实验 ,研究了回灌对垃圾填埋场初期渗滤液 CODCr的影响。研究结果表明 ,模拟降雨雨水的渗入且无渗滤液回灌的参照柱 ,其渗滤液出水 CODCr最高 ,一般在 70 0 0 0 mg/L 左右 ;模拟渗滤液原液回灌 ,从第 4周起因脂肪酸的积累导致渗滤液的 p H低于 6,从而抑制了微生物的生化反应 ;模拟好氧生物处理后渗滤液的回灌 ,能加速垃圾层 CODCr的溶出和甲烷化阶段的建立 ,且此时渗滤液的 CODCr变化规律符合指数方程 ;当垃圾层建立甲烷化阶段后 ,回灌 CODCr在 2 0 0 0 0 m g/L 左右的渗滤液 ,仍可促使垃圾中有机物迅速转化为气态物