Analysis of chemical compositions contributable to chemical oxygen demand (COD) of oilfield produced water

This work was to give a comprehensive estimation for the chemical compositions contributable to COD of the produced water treatment system. For this purpose, the wastewater samples were collected from an onshore wastewater treatment plant. The chemical compositions of the wastewater were investigated, and the COD contributed by each component was estimated. The results showed that the COD levels of O&G and SS presented decreasing trends during the whole process and achieved total removal percentages of 95.1% and 62.3%, respectively. The final COD of organic acids and low-molecular-weight carbonyl compounds were respectively lowered to nearly 64% and 35% of their initial levels, and no regular trends were found for the COD of these chemicals during the whole treatment process. The COD of inorganic components presented minor variations at all sampling spots. The majority of COD was originated from O&G in raw wastewater. The COD contributed by O&G decreased greatly with continuous treatment and finally was lower than 17% of measured COD. At each sampling spot, the ratios of COD contributed by SS did not exceed 7.6% of measured COD. Other measured chemicals, including organic acids, carbonyl compounds, volatile phenols, reductive anions, metals and TDP were not the main sources of COD during the whole treatment process, and the ratio of COD was below 9% at each sampling spot. Most of the soluble components contributable to residual COD were still unknown after biological treatment, and the COD contributed by these components was greater than 57% of measured COD.     

碳氮比对人工湿地污水处理效果的影响

采用表面流人工湿地系统静态小试装置,考察了低、中、高3组不同进水COD/N(2,5,10)对系统中氮、磷及COD去除效果的影响。结果表明:进水C/N的变化对COD的去除率影响不大,平均去除率达到94.6%。TN的去除率随着COD/N的增大而逐渐升高,在C/N=5时达到63.8%,继续提高COD/N,TN的去除率变化不大。NH4+-N去除率随着COD/N的增加而降低。随着碳源的增加,释磷菌能够从进水中获得充足的碳源,从而可以比较充分地释磷,因此,磷的去除率随COD/N的增加而提高。     

COD浓度和进水流量比对一体化工艺脱氮除碳的影响

保持进水总流量不变,以一定流量比同时从缺氧区和厌氧区进水,探讨了不同进水流量比(R=Q_厌/Q_缺)和进水COD浓度对中心岛式一体化OCO工艺脱氮除碳的影响。研究结果表明,进水COD浓度和进水流量比Rs对COD的去除效果影响不大,出水COD浓度一直稳定在50 mg/L以下,去除率在92%以上;进水COD浓度和进水流量比Rs共同决定着系统TN的去除效果,进水COD浓度为100 mg/L、200 mg/L时,TN去除率随着进水流量比Rs的减小呈增加的趋势;当进水COD浓度为 300 mg/L时,TN去除率随着进水流量比Rs的减小呈先升高后降低的趋势,在进水流量比Rs为3∶1时TN去除率最高,达到87%。     

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.     

自配消解液分光光度法测定污水中的COD

以自配消解液代替ThermoFisher公司AQ4001COD测定系统的专用消解液,比较了自配消解液分光光度法与国家标准重铬酸钾法(GB 11914-1989)测定化学需氧量(COD)的差异。对比试验表明,自配消解液分光光度法测定COD的结果精确度和准确度高,与国家标准方法无显著性差异。自配消解液分光光度法测定水样COD值的相对标准偏差;低量程(30～150 mg/L)为1.38%～2.53%,中量程(0～1 500 mg/L)为0.47%～3.63%,高量程（2 000～15 000 mg/L）为0.17%～3.53%,在国家标准方法测试水样COD值的允许误差范围内。除制革废水外,自配消解液可以代替AQ4001COD测定系统的专用消解液,适用不同量程范围内污水COD的测定。自配消解液分光光度法具有试剂使用量少、速度快、经济、二次污染小等优点,值得在环境科学领域及废水水质监测中推广应用。     

外循环式UASB反应器处理槟榔废水

在中温（35±2℃）条件下,利用外循环式UASB反应器处理中高有机浓度的槟榔加工废水,并着重探讨了水力停留时间（HRT）对厌氧消化的影响。研究表明,当反应器稳定运行,水力停留时间为1 d,进水COD浓度5 000 mg/L左右,容积负荷在2.53-5.25 kg COD/（m3·d）时,COD去除率在38%以上,出水COD〈3 000 mg/L,平均产气率为0.41 m3/kg COD;若水力停留时间延长至4 d,容积负荷为1.26-1.30 kg COD/（m3·d）,COD去除率可以达到79%,出水COD〈1 200 mg/L,出水可生化性下降,BOD5/COD平均为0.28,实验取得了良好的处理效果,为利用厌氧技术处理槟榔加工废水提供了设计依据。     

山梨酸废水在ABR中的基质降解行为

稳态条件下,采用厌氧折流板反应器(anaerobic baffled reactor,ABR)处理山梨酸废水并进行基质降解动力学研究.实验表明,在污泥负荷为0.54～1.63 kg COD/(kg VSS·d)的范围内,COD去除率随着负荷的增加从85%降到55%.各隔室出水COD沿程递减,前3个隔室承担了去除COD的重要作用,但随着污泥负荷的增加,后部承担的COD去除率比例增大.基于各串联隔室完全混合的假定,推导ABR中山梨酸废水的基质降解动力学方程,并通过实验确定相关动力学参数及相应的动力学方程.实测值与预测值基本吻合.     

Influence of chemical oxygen demand/total Kjeldahl nitrogen ratio and sludge age on nitrification of nitrogenous wastewater.

Four laboratory-scale biological nitrification units (influent total Kjeldahl nitrogen [TKN] = 1002 to 1062 mg/L) were operated at chemical oxygen demand (COD)/TKN ratios of approximately 0.5, 1.0,15, and 2.0 and at three different sludge ages of 30, 20, and 10 days to study the influence of COD/TKN, sludge age, COD loading, and TKN loading on nitrification and nitrifiers. Percent nitrification was found to increase with decreases in COD/TKN and increases in sludge age. The average nitrifier concentration increased from 460 mg/L at a COD/TKN of 2.22 and a sludge age of 10 days to 706 mg/L at a COD/TKN of 0.676 and a sludge age of 30 days. The nitrifier fraction was found to be higher at a lower COD/TKN and lower at a higher COD/TKN. The nitrifier fraction increased with the decrease in sludge age and COD loadings and the increase in TKN loadings. The effect of sludge age on the nitrifier fraction was amplified at a COD/ TKN of approximately 0.5 rather than at approximately 2.0. The nitrification rate (kilograms TKN oxidized per kilograms nitrifiers per day) was shown to be dependent on COD/TKN and sludge age. The activity performed by Nitrobacter was affected at all COD/TKN ratios studied as well as at a sludge age of 10 days. This was manifested by the accumulation of high levels of nitrite-nitrogen in the nitrified effluent. The presence of heterotrophs did not affect nitrification rates and the growth of nitrifiers, which were found to be beneficial. High sludge age and COD loadings resulted in a higher sludge volume index of more than 200 mL/g mixed liquor suspended solids. Microscopic examination showed filamentous structure of sludge under these conditions. It is concluded from the investigations that a sludge age of 30 days and a COD/TKN of approximately 1.0 are optimal to yield maximum nitrification and nitrifier growth rates for treating high-strength nitrogenous wastewater.     

UASB-SBR处理涤纶短纤维废水的实验研究

分别采用水解酸化与好氧（SBR）、厌氧（UASB）与好氧（SBR）工艺对涤纶短纤维废水的生物降解性能进行研究。水解酸化与好氧工艺在进水COD为1 900 mg/L的时候,去除率在80%左右。采用UASB-SBR工艺,进水COD为2700 mg/L时,COD去除率可以达到96%,出水COD〈100 mg/L。实验研究表明,涤纶短纤维废水更适合采用UASB-SBR工艺来处理,并且能够取得较好的效果。     

道路径流SS和COD污染特征及出流规律

选择芜湖市火车站点进行长期监测,采集降雨7次;同时选择5个不同功能区,采集典型降雨1次。探讨了道路径流中总固体悬浮物(SS)和化学需氧量(COD)的污染特征、影响因素及出流规律,结果表明,7次降雨事件SS和COD平均值范围分别为198～1 529 mg/L和66～367 mg/L。SS和COD污染较为严重。SS在不同功能区中大小顺序为:工业区>居民区>商业区>交通区>文教区,总COD大小顺序为:工业区>交通区>居民区>商业区>文教区,溶解态COD大小顺序为:工业区>交通区>商业区>文教区>居民区,颗粒态COD大小顺序为:工业区>居民区>交通区>文教区>商业区。工业活动对地表径流SS和COD含量影响最大。SS受降雨历时影响较大,溶解态COD受平均雨强影响较大,颗粒态COD受最大雨强影响较大。不同降雨强度下,SS、溶解态COD及颗粒态COD的出流规律不同,降雨强度对径流初期效应的影响显著。     

Impacts of COD and DCP loading rates on biological treatment of 2,4-dichlorophenol (DCP) containing wastewater in a perforated tubes biofilm reactor

Biofilm processes offer considerable advantages for biological treatment of chlorophenol containing wastewaters since such industrial effluents are difficult to treat by conventional activated sludge processes. A rotating perforated tubes biofilm reactor (RTBR) was developed and used for treatment of 2,4-dichlorophenol (DCP) containing synthetic wastewater. Effects of COD and DCP loading rates on COD, DCP and toxicity removals were investigated. Percent COD removal decreased and effluent COD increased with increasing COD and DCP loading rates due to toxic effects of high DCP content in the feed. DCP and toxicity removals showed similar trends. As the DCP loading rate increased the effluent DCP content increased yielding high toxicity levels in the effluent. COD and DCP loading rates should be below 90gCODm(-2)d(-1) and 2.8gDCPm(-2)d(-1) in order to obtain more than 90% DCP and toxicity removals. However, DCP loading rates lower than 1gDCPm(-2)d(-1) are required to obtain more than 90% COD removal. Empirical equations were developed to estimate percent COD, DCP and toxicity removals as functions of COD and DCP loading rates. The coefficients of the empirical equations were determined by using the experimental data. Empirical model predictions for percent COD, DCP and toxicity removals were in good agreement with the experimental data.     

二氧化氯处理中药废水的氧化特性研究

采用稳定性二氧化氯溶液氧化降解中药废水,运用正交设计方法考察了常温、常压(291～298 K,1.013×10~5Pa)下ClO_2起始浓度([ClO_2]:COD)、pH、氧化反应时间等因素对中药废水处理效果的影响。研究表明,(1)当[ClO_2]:COD在1.0～0.4范围时,COD的平均去除率42%;当[ClO_2]:COD大于1.0或小于0.4时,COD平均去除率仅为27%～35%;(2)pH=2～4时,COD去除率可以达到40%以上,且pH≥10时,COD去除率高达59%;(3)COD去除率随着反应时间的延长而升高,氧化反应30 min左右,COD去除率能达到40%以上,105 min后处理效率达到63%;(4)ClO_2处理中药废水的最佳工艺条件是[ClO_2]:COD为0.7:1,反应pH值6,反应时间75 min。     

FOP-EGSB-MBR组合工艺处理2-萘酚生产废水

2-萘酚生产废水具有COD高、BOD/COD值低和生物毒件高的特点,采用FOP-EGSB-MBR组合工艺对其模拟废水进行处理工艺的研究.结果表明:废水经Fenton氧化处理后,可将出水BOD/COD值从0.01提高至0.67;再经过厌氧和好氧处理后,出水COD为100 mg/L以下;该组合上艺总的COD去除去可达99%,且运行性能稳定,效果可靠.     

EGSB反应器处理城市生活垃圾沥滤液

采用膨胀颗粒污泥床(EGSB)反应器对城市生活垃圾焚烧厂产生的垃圾沥滤液进行处理。实验结果表明:中温条件下,当COD浓度为55 000 mg/L左右,有机容积负荷(OLR)为22.8 kg COD/(m3.d)时,EGSB对垃圾沥滤液具有较好的的处理效果,COD去除率可达94.2%。当进水COD为72 000 mg/L左右时,为保证反应器的稳定运行,OLR应降低至18.2 kg COD/(m3.d),此时COD去除率可以达到88%左右,出水COD平均为9 103 mg/L。垃圾沥滤液和EGSB处理出水均以小分子量有机物为主,其中<4 kDa的有机物分别占76.5%和74.4%。EGSB对整个分子量区间的溶解性有机物都有较好的处理效果,其中对大分子有机物的处理效率相对更高。     

电极材料对电解法处理循环式准好氧垃圾填埋场渗滤液效果的影响研究

分别用3种不同材料电极(不锈钢、Ti/Pt和Ti/RuO2-IrO2)作阳极、石墨电极作阴极在同一条件下分别对循环式准好氧填埋垃圾场渗滤液进行电解处理对比研究.研究结果表明,随着电解时间的变化,渗滤液中的COD、BOD5、BOD5/COD、重金属离子浓度、色度和pH值均会发生改变.当电解时间为10～20 min时,用上述3种电极作阳极电解均会出现渗滤液COD、BOD5、BOD5/COD增大的现象;当电解时间为30～40 min时,用Ti/RuO2-IrO2或Ti/Pt电极作阳极电解均可使渗滤液的色度降为0;当电解时间为120 min时,分别用3种电极作阳极电解都可使渗滤液中的COD、BOD5和重金属得到有效的去除,其中用Ti/RuO2-IrO2电极作阳极电解对COD、BOD5的去除效果最好:用Ti/Pt电极作阳极电解对Pb2 的去除效果最好.     

Modification of chemical oxygen demand monitoring in the Yellow River, China, with a high content of sediments.

This paper presents a modification of chemical oxygen demand (COD) monitoring giving a better indication of the pollution level compared with the conventional COD method for rivers with a high content of sediments. The correlation between the sediment organic carbon and COD was investigated using sediments sampled in the middle Yellow River, China. Partitioning of the sediment organic carbon between the water and sediment phases was also investigated using batch experiments, with the sediment concentration varying from 20 to 400 g/L. As a result, the COD modification equations are proposed for both turbid water (mixture of water and sediment) and supematant water (filtrate using a 0.45-microm membrane). The modified COD in turbid water and supernatant water could be 40 and 10% less than the monitored COD values, respectively. These results may have a significant influence on the assessment of water quality class in the Yellow River.     

两级SBR与传统SBR工艺的对比研究

采用两级SBR工艺(TSSBR)处理COD与氮浓度较高的工业废水,SBR1去除有机物,SBR2主要进行硝化反硝化。TSSBR与传统SBR工艺相比,COD降解速率和硝化反应速率明显提高,COD去除率由84%提高到93%,2种工艺的反硝化速率没有明显差别。在原水COD浓度较高的情况下,TSSBR可有效克服高COD浓度对硝化反应的抑制,硝化反应速率是传统SBR的2倍。对于COD和氮浓度较高的工业废水,TSSBR明显优于传统SBR,是一种理想的处理工艺。     

光度法测定高浓度化学需氧量

在建立了低浓度化学需氧量光度测定法的基础上，进一步摸索了高浓度ＣＯＤ光度测定法的测试条件，实验证明，在波长６１０ｎｍ，重铬酸钾浓度（１／６Ｋ２Ｃｒ２Ｏ７）０．５５ｍｏｌ／Ｌ的条件下，可以测定２００～２０００ｍｇ／Ｌ范围内的ＣＯＤ，结果令人满意，用该光度法测定的ＣＯＤ与标准滴定法的ＣＯＤ比值在０．９７～１．０３之间。     

Methane production from the soluble fraction of distillers' dried grains with solubles in anaerobic sequencing batch reactors

Methane production from the soluble fraction of distillers' dried grains with solubles, a co-product of ethanol production, was studied in 2-L anaerobic sequencing batch reactors (ASBRs) under 10 different operating conditions. Methane production and chemical oxygen demand (COD) removal were quantified for a wide range of operating parameters. Chemical oxygen demand removals of 64 to 95% were achieved at organic loading rates ranging from 1.5 to 22.2 g COD/L x d, solids retention times from 8 to 40 days, and food-to-microorganism ratios ranging from 0.4 to 1.9 g COD/g volatile suspended solids (VSS) x d. Biogas methane content varied from 61 to 74%, with 0.29 L CH4 produced/g COD removed. Roughly 56% of the influent COD and 84% of the COD removed in the ASBRs was converted to methane. Microbial yield (Y) and decay (b) constants were determined to be Y = 0.126 g VSS/g COD removed and b = 0.032 day(-1), respectively. Methane produced from co-products can reduce the costs and fossil-fuel consumption of ethanol manufacture.     

The effect of residual chemical oxygen demand on anoxic and aerobic phosphate uptake and release with various intracellular polymer levels.

This study investigated the anoxic and aerobic phosphate uptake and release reactions and the fraction of denitrifying phosphate-accumulating organisms (DPAOs) under various initial chemical oxygen demand (COD) and residual COD conditions. The results showed that DPAOs and non-DPAOs could release phosphate when high soluble COD was present. Consequently, the phosphate-uptake potential was dynamic and increased when the initial COD increased, the initial polyhydroxyalkanoates (PHA) increased, and the residual COD decreased. Furthermore, the electron acceptor (oxygen of nitrate) has more significant influence on the phosphate uptake/release characteristics, while the residual COD concentrations have little influence on that. The fraction of DPAOs to phosphate-accumulating organisms was 42% when the initial PHA storage was enough by both DPAOs and non-DPAOs. This was closely related to the relative phosphate uptake (47%) in the anoxic zone of the process.