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.     

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。     

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.     

Effect of operational parameters on the removal of particulate chemical oxygen demand in the activated sludge process.

The removal of particulate material in the aeration basin of the activated sludge process is mainly attributed to bioflocculation and hydrolysis of particulate substrate. The bioflocculation process in the aeration tank of the activated sludge process occurs only under favorable conditions in the system, and several common operational parameters affect its performance. The principal objective of this research was to observe the effect of mixed liquor suspended solids, solids retention time (SRT), and extracellular polymer substances on the removal of particulate substrate by bioflocculation. A first-order particulate removal expression, based on flocculation, accurately described the removal rates for supernatant suspended solids and colloidal chemical oxygen demand. Based on the results presented in this investigation, a mixed liquor concentration of approximately 2200 mg/L, an SRT of at least 3 days, and a contact time of 30 minutes are needed for relatively complete removal of the particulate substrate in a plug-flow reactor.     

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     

Ti/BDD/PbO_2复合电极在化学需氧量测定中的应用

以钛基掺硼金刚石为基体,采用电沉积的方法制备了Ti/BDD/PbO2复合电极,并将其用于化学需氧量（COD）的测定。采用扫描电子显微镜（SEM）和X射线衍射谱图（XRD）表征了电极的微观形貌及结构,采用电化学工作站考察了电极对有机物响应特性。实验结果表明,在1.45 V的低电位条件下,线性范围为0.5～175 mg/L,检测限为0.3 mg/L（S/N=3）。采用Ti/BDD/PbO2复合电极测定法和重铬酸钾标准方法对市政污水、食品废水及印染废水的对比结果表明,2种方法的相对误差小于10%,具有良好的一致性。     

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.     

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.     

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.     

Formation of singlet oxygen during farmorubicin oxidation.

The enhanced generation of singlet oxygen (1O2) during oxidation of farmorubicin in the Co(II) + H2O2 system was studied using chemiluminescent, fluorescent and spectrophotometic techniques. The influence of 1O2-quenchers, catalase, superoxide anion radical (O2*-) and hydroxyl radical (HO*) scavengers on the light emission was studied. The spectrophotometric determination of 1O2 was based on bleaching of p-nitrosodimethylaniline caused by an intermediate product of the reaction of 1O2 with imidazole, and was followed by monitoring the decrease in optical density at 440 nm.     

A novel design for anaerobic chemical oxygen demand and nitrogen removal from leachate in a semiaerobic landfill

The removal capacity of carbon and nitrogen from an artificial leachate was evaluated by using laboratory-scale columns, and a design was proposed to remove nitrogen more efficiently from a semiaerobic landfill. Five columns (i.e., two artificial municipal waste columns under anaerobic and semiaerobic conditions, an artificial construction waste column under semiaerobic conditions, and two crushed stone columns under anaerobic and semiaerobic conditions) were used. The influent load rates of organics [g chemical oxygen demand (COD)/m3 x day], NH4+, NO3- and aeration conditions for the columns were varied, and the removal capacities of the columns for COD, NH4+-N, and NO3--N were measured. Among the packed column materials, crushed stone was shown to be most effective in removing COD, NH4+ N, and NO3--N from artificial leachate. Average removal rates of crushed column under the semiaerobic condition (column D) for COD and NH4+-N were estimated at about 150 g COD/m3 x day and 20 g COD/m3 x day, while those of crushed column under anaerobic condition (column E) for COD and NO3--N at about 400 and 150 g COD/m3 x day, respectively. It also was found that denitrification and nitrification reactions in column D occurred at the same time, and the ratio of denitrification to nitrification was estimated to be about 80%. Therefore, an anaerobic structure, which could be attached to the bottom of a main pipe in a semiaerobic landfill, is suggested to remove nitrogen and organic substances more effectively.     

Ti/BDD/PbO2复合电极在化学需氧量测定中的应用

以钛基掺硼金刚石为基体,采用电沉积的方法制备了Ti/BDD/PbO2复合电极,并将其用于化学需氧量(COD)的测定。采用扫描电子显微镜(SEM)和X射线衍射谱图(XRD)表征了电极的微观形貌及结构,采用电化学工作站考察了电极对有机物响应特性。实验结果表明,在1.45 V的低电位条件下,线性范围为0.5～175 mg/L,检测限为0.3 mg/L(S/N=3)。采用Ti/BDD/PbO2复合电极测定法和重铬酸钾标准方法对市政污水、食品废水及印染废水的对比结果表明,2种方法的相对误差小于10%,具有良好的一致性。     

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.     

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.