COD fractionation and parameter estimation for combined sewers by respirometric tests

This paper evaluates the effects of the pipeline retention time in sewer systems and the dilution by stormwater runoff on COD fractions and kinetic parameters of samples from two large‐scale wastewater treatment plants (WWTPs) fed with combined sewers, one collected from adjacent residential areas (Sewer Q) and the other undergoing long pipeline transportation (Sewer B). With four batch tests, COD fractions and kinetic parameters of two sewers were obtained by numerical computation based on activated sludge models (ASMs) modified by a dual hydrolysis mechanism. Long pipeline transportation significantly influenced the content and existence of heterotrophic biomass fractions in sewers, and the percentage of the fraction in Sewer B (17%) was higher than that in Sewer Q (9%). Compared with Sewer Q, long pipeline retention also resulted in lower concentrations of hydrolysable fractions and particulate inert COD in Sewer B, as well as an increase in the hydrolysis rate coefficient of particulate hydrolysable COD from 0.90 day^?1 in Sewer Q to 1.83 day^?1 in Sewer B. Results of samples from Sewer B during a typhoon event showed high variations of COD fractions and parameters, indicating the necessity for COD fractionation and parameter calibration before applying ASMs to wet weather cases. Copyright © 2008 Society of Chemical Industry     

Wastewater COD characterization: analysis of respirometric and physical‐chemical methods for determining biodegradable organic matter fractions

BACKGROUND: In this work, a comprehensive study of the respirometric and physical–chemical methods has been performed to evaluate the information provided by these two methodologies in order to assess the biodegradable organic matter fractions of wastewater. RESULTS: First, an analysis was performed of the influence of the initial substrate on biomass ratio (F₀/X₀) in the assessment of readily biodegradable organic matter, S_S, through respirometric experiments. In order to achieve an adequate assessment of the S_S component, similar conditions (given by the initial F₀/X₀ ratio) must be employed in experiments that are carried to determine S_S and Y_H (heterotrophic yield). Second, a comparative analysis of respirometric and physical–chemical methods was carried out. The respirometric analysis yielded a lower value of the S_S component than the one using the physical–chemical method. Moreover, the respirometric analysis cannot measure the total content of slowly biodegradable organic matter, X_S, since this method is only capable of determining the readily hydrolyzed biodegradable substrate. CONCLUSIONS: Considering the results, an adequate characterization method of the S_S component has been proposed. This method provides readily and slowly hydrolyzable biodegradable organic matter fractions. Copyright © 2010 Society of Chemical Industry     

利用微波测定磷矿石浮选废水中的COD值

介绍利用微波法代替传统回流法测定磷矿石浮选废水中的COD值。通过微波法与回流法相关性实验表明,微波法准确度高,重现性好,费用低,快速,水电耗量少,适合大批量分析。     

丁苯橡胶凝聚水中防老剂含量的测定及其对COD的影响

设计了不同防老剂配方量的丁苯橡胶凝聚水,采用高效液相色谱法(HPLC)测定了环保型丁苯橡胶(SBR)1500E凝聚水中的防老剂烷基-芳基-对苯二胺复配物(EPPD)含量。配制不同质量浓度(ρ)的防老剂EPPD水溶液并检测其化学需氧量(COD),进而确定了的ρ-COD标准曲线,根据HPLC检测结果和ρ-COD标准曲线可得出凝聚水样品中防老剂对水体COD的贡献率。     

SBR工艺处理高COD、高氨氮化纤废水反应终点判断

某化纤厂采用SBR工艺处理高COD、高氨氮废水,根据pH值的变化规律,并综合其他参数来判断反应终点,方法简单易行,并可以实现时时监测。     

超临界水氧化丙烯氰废水的反应动力学理论研究

以丙烯氰为研究对象,探讨丙烯氰在超临界水氧化中的动力学研究。采用密度泛函理论研究氧负离子自由基与丙烯氰分子的反应。针对可能存在的抽氢反应、置换氢反应、生成水反应及羟基化反应通道,在B3LYP/6-311++G(2d,p)和HandHLY/6-311++G**的水平上得到反应物、产物、中间体复合物和过渡态的优化构型,并利用IRC计算证实反应通道。     

福建无烟粉煤-纸浆黑液小型流化床水蒸汽催化气化表观动力学研究

在内径为26mm的实验室小型流化床反应器中进行福建尤溪无烟粉煤与纸浆黑液(BL)浸渍混合后的水蒸气催化气化实验.考察了4g/min水蒸汽流量下,不同催化剂加载浓度及不同温度对碳转化率的影响,并对催化气化表观动力学参数进行拟合与计算.研究结果表明:气化温度的升高和催化剂加载浓度的增大能显著提高碳转化率和产气速率,催化剂加载浓度从0%到8%的增加明显降低了催化气化反应的活化能,而从8%到10%的增加又令活化能有增加的趋势.在本实验条件下,BL作为催化剂的饱和加或浓度为8%.     

赤泥水浸脱碱实验及动力学研究

赤泥是一种碱性污染物,强碱性是制约其综合利用的关键因素。进行了拜耳法赤泥水浸脱碱实验及动力学研究,实验结果表明：赤泥在水浸次数为4次、液固体积质量比为9 mL/g、反应温度为90 ℃和反应时间为60 min的条件下,赤泥的脱碱率可达71%。采用未反应收缩核模型对水浸脱碱数据进行线性拟合,动力学分析表明：活化焙烧后赤泥的水浸脱碱过程受扩散步骤控制,线性相关系数大于0.97,表观活化能为11.72 kJ/mol。     

实施清污分流提高水资源利用率

介绍甘肃瓮福化工有限责任公司工艺水使用不合理、含磷废水外排严重,造成水耗、磷耗高的问题,通过实施用水分厂小循环、公司大循环、清污分流,并强化管理,水资源利用率提高,年节约成本104万元,回收磷酸一铵产品900 t、P2O5 432 t.     

Supercritical water oxidation of coal: Investigation of operating parameters' effects, reaction kinetics and mechanism

Supercritical water oxidation (SCWO) of coal was conducted in a continuous tubular reactor under various reaction conditions. Our experimental results show that the removal rate of chemical oxygen demand (COD) had no significant dependence on the temperature variations. Effect of residence time was less significant as exceeded fixed values. Free radical mechanism of SCWO reaction may be a possible explanation for the relative low conversion rate of coal at the range of tested oxygen excess. Compared with other parameters, effect of pressure was less significant. A global power-law rate expression was regressed from experimental data. The reaction orders for coal slurry and oxidant were 1.79 and 0.28 respectively. The reaction activation energy E_a was determined to be 112.3 kJ mol⁻¹, and the pre-exponential factor k₀ was 412 (mol/L)^−1.07 s⁻¹. The deviation between the model and experimental data was within ± 9%. Free radical mechanism, oxidation and hydrolysis mechanisms and phenolic hydroxyl oxidation mechanism were considered to be the possible mechanisms for the SCWO process of coal.     

黑臭水体形成原因与治理技术

黑臭水体已成为我国大部分城市共同面临的污染问题,探究其产生的原因、形成机理和治理技术具有重要意义。概述了城市黑臭水体产生的原因、形成机理,结合案例介绍了黑臭水体的治理技术和国内外治理情况,对今后黑臭水体治理思路提出几点建议。     

基于改进灰色-多元回归组合预测模型的燃煤电厂智慧水务研究

以某燃煤电厂水务系统为研究对象,对机组运行参数和水量历史数据进行筛选和关联性分析,根据前期水平衡测试结果,结合响应面分析验证,发现机组负荷、蒸发损失系数、浓缩倍率和循环水温升这四个因素能够对全厂供水量产生关键性影响。基于灰色理论和多元非线性回归分析,分别建立各因素的灰色预测模型GM(1, 1),再将灰色模型预测值作为自变量输入到多元非线性回归方程中,得到了改进灰色-多元非线性回归组合的供水量预测模型,其模型拟合度R²为0.913且与真实值的平均相对误差为6.9%左右,实现了灰色模型和回归模型优势互补,有效地预测该电厂供水量未来变化;而供水量预测是智慧水务建设的关键所在,是水务管理和智能调度的主要依据,也是实现供水管网漏损和仪表故障报警的重要途径。     

过氧化钙在城镇黑臭水体修复中的作用

我国城镇水体污染严重,本文根据城镇黑臭水体污染与生态修复治理技术现状,分析得出水体缺氧是导致城镇水体黑臭污染的主要原因以及复氧措施在治理黑臭水体时的重要性,介绍了水体原位复氧具有对水体扰动小、修复效果明显和不产生二次污染等优点,但常规复氧措施存在工程规模大、设备运行昂贵和后期仪器维护贵等问题。结合CaO₂在黑臭水体原位治理过程的高效释氧、强化微生物活性及释放羟基自由基等特性,简述了CaO₂对黑臭水体中有机物、重金属、氮磷营养元素及硫化物等污染物的去除机理与修复效果;通过归纳CaO₂在黑臭水体修复过程中的不足,建议在CaO₂对污染物的降解机理和缓释型CaO₂复合释氧剂等方面应加强研究;指出缓释型CaO₂复合释氧剂在城镇黑臭水体生态修复治理中具有重要实际意义。     

Phosphoric acid-modified magnesium oxychloride: Study of water stability,kinetics, and pair distribution function

Magnesium oxychloride (MOC) excels in performance applications due to inherent structural strength, fire retardant properties, and numerous other attributes. To avoid the slow degradation of MOC when exposed to water, phosphoric acid is usually added, effectively increasing retention of structural properties (water stability). While this is an effective method, it is poorly understood. Additions of 2.5 wt.% and above had positive impacts on the water stability, preserving ~50 wt.% crystalline MOC after water stability tests. Phosphoric acid addition also impacted the reaction kinetics, increasing the activation energy of curing from 72.2 to 87.6-95.2 kJ/mol. Using synchrotron X-ray scattering and pair distribution function analysis, we identified an unreported amorphous phase formed when phosphoric acid is added; this phase contains structural motifs related to MgHPO₄·3H₂O (newberyte), Mg₂P₂O₇·3.5H₂O (magnesium pyrophosphate), and amorphous MOC phase. The short-range order of the samples show a prominent peak at ~3.2 Å that grows with increasing acid addition, believed to be a combination of newberyte (~3.4 Å Mg–P), pyrophosphate (~3.25 Å Mg–P), and MOC (~3.15 Å Mg–Mg). We propose that the increased water stability observed is due to this combined amorphous phase, which retains the low water solubility properties of MgHPO₄·3H₂O and Mg₂P₂O₇·3.5H₂O, effectively protecting the MOC crystalline phase.     

Kinetics of the oxidation of carbon black by NO2: Influence of the presence of water and oxygen

In a fixed bed reactor, the rate of carbon black oxidation by NO₂ is significant for temperatures above 300°C, leading to NO, CO and CO₂ formation. The presence of O₂ in the feed gas increases the rate of oxidation, as well as the presence of water. A cumulative effect is observed when both water and oxygen are present. An oxygen balance shows that oxygen atoms of water molecules are not consumed. Water acts as a catalyst for the C-NO₂ reaction. A kinetic mechanism in which intermediate nitro-oxygenated species are formed in the presence of NO₂ during an initial step is in agreement with all these observations. Oxygen and NO₂ are able to react with these species at 300°C. A parametric study of the effects of the temperature, NO₂, O₂ and H₂O concentrations was performed. With a one-dimensional model of NO₂ consumption along the thickness of the carbon black bed, kinetic constants were derived and a phenomenological law was proposed, accounting for the effect of the presence of oxygen and water.     

Supercritical water oxidation of quinoline in a continuous plug flow reactor—part 2: kinetics

The results of a detailed investigation into the kinetics of quinoline oxidation in supercritical water are presented. The novel kinetic data presented were obtained in a continuously operated, plug flow reactor where parameters such as temperature, pressure, residence time and stoichiometric ratio of oxidant to quinoline were investigated and detailed in the companion paper (Pinto LDS, Freitas dos Santos LMF, Al‐Duri B and Santos RCD, Supercritical water oxidation of quinoline in a continuous plug flow reactor—part 1: effect of key operating parameters. J Chem Technol Biotechnol). An induction time was experimentally observed, ranging from 1.5 to 3.5 s, with longer times observed in experiments carried out at lower temperatures. A pseudo‐first‐order rate expression with respect to quinoline concentration (with oxygen excess) was first adopted and the activation energy of 234 kJ mol^?1 and a pre‐exponential factor of 2.1 × 10¹⁴ s^?1 were estimated. Furthermore, an integral power rate model expression was established, attributing a reaction order for quinoline as 1 and for oxygen as 0.36. An activation energy and pre‐exponential factor for this model were determined as 224 kJ mol^?1 and 3.68 × 10¹⁴ M^?0.36 s^?1, respectively. A global rate expression was then regressed for the quinoline reaction rate from the complete set of data. The resulting activation energy was 226 ± 19 kJ mol^?1 and the pre‐exponential factor was 2.7 × 10^{13 ± 2} M^?0.1 s^?1. The reaction orders for quinoline and oxygen were 0.8 ± 0.1 and 0.3 ± 0.1, respectively. It was shown that the least‐squares regression method provided the best‐fit model for experimental results investigated in this study. Copyright © 2006 Society of Chemical Industry     

Pyrolysis of heavy oil in the presence of supercritical water: The reaction kinetics in different phases

In the presence of supercritical water (SCW) and N₂, the pyrolysis of heavy oil was investigated to distinguish the difference in the reaction kinetics between the upgrading in the SCW and oil phases. The pyrolysis in the SCW phase is faster than that in the oil phase, but the reaction in whichever phase is retarded by vigorous stirring. The pyrolysis can be preferably described by a four‐lump kinetic model consisting of the condensation of maltenes and asphaltenes in series. In the SCW phase, highly dispersed asphaltenes are isolated by water clusters from maltenes dissolved in SCW surroundings, by which the condensation of asphaltenes is drastically accelerated. Benefited from excellent mass transfer environments in SCW, the condensation of maltenes is promoted simultaneously. The introduction of SCW into the pyrolysis of heavy oil results in an effectively increased upgrading efficiency, but its influence on the properties of equilibrium liquid products is minor. © 2014 American Institute of Chemical Engineers AIChE J, 61: 857–866, 2015     

高炉水淬渣对电镀废水中重金属和COD吸附的响应面优化

为了考察高炉水淬渣处理实际电镀废水中重金属离子和COD的可行性,分别研究了吸附剂投加量、pH、吸附时间以及温度等单因素对Cu²⁺、Zn²⁺或COD去除率的影响。在单因素实验的基础上,应用 Box-Behnken中心组合方法进行三因素三水平试验,建立二次多项数学模型,并验证该模型的有效性。采用响应曲面法探讨吸附剂投加量、pH、吸附时间3个因子的交互作用及其最佳水平。结果表明：在吸附剂投加量为1.4g、pH为8、吸附时间为120min的最优化条件下,电镀废水中Cu²⁺、Zn²⁺和COD去除率达到最大,分别为99.35%、98.46%和53.63%。经对最优条件进行验证,预测值与验证实验平均值接近。吸附后废水中的Cu²⁺和Zn²⁺低于GB 21900-2008电镀废水新建企业污染物排放限值要求,而COD没有满足排放要求,所以仅应用高炉水淬渣吸附技术还不足以去除电镀废水中所有有害物质,因此可利用此技术作为辅助工艺,联合其他技术共同去除电镀废水中的重金属离子和有机物,使出水水质达到国家排放标准。