Photochemical degradation and mineralization of 4-chlorophenol

INTENTION, GOAL, SCOPE, BACKGROUND: Since the intermediate products of some compounds can be more toxic and/or refractory than the original compund itself, the development of innovative oxidation technologies which are capable of transforming such compounds into harmless end products, is gaining more importance every day. Advanced oxidation processes are one of these technologies. However, it is necessary to optimize the reaction conditions for these technologies in order to be cost-effective. OBJECTIVE: The main objectives of this study were to see if complete mineralization of 4-chlorophenol with AOPs was possible using low pressure mercury vapour lamps, to make a comparison of different AOPs, to observe the effect of the existence of other ions on degradation efficiency and to optimize reaction conditions. METHODS: In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV, UV/H2O2 and UV/H2O2/Fe2+ (photo-Fenton process) were investigated in labscale experiments for the degradation and mineralization of 4-chlorophenol. Evaluations were based on the reduction of 4-chlorophenol and total organic carbon. The major parameters investigated were the initial 4-chlorophenol concentration, pH, hydrogen peroxide and iron doses and the effect of the presence of radical scavengers. RESULTS AND DISCUSSION: It was observed that the 4-chlorophenol degradation efficiency decreased with increasing concentration and was independent of the initial solution pH in the UV process. 4-chlorophenol oxidation efficiency for an initial concentration of 100 mgl(-1) was around 89% after 300 min of irradiation in the UV process and no mineralization was achieved. The efficiency increased to > 99% with the UV/H2O2 process in 60 min of irradiation, although mineralization efficiency was still around 75% after 300 min of reaction time. Although the H2O2/4-CP molar ratio was kept constant, increasing initial 4-chlorophenol concentration decreased the treatment efficiency. It was observed that basic pHs were favourable in the UV/H2O2 process. The results showed that the photo-Fenton process was the most effective treatment process under acidic conditions. Complete disappearance of 100 mgl(-1) of 4-chlorophenol was achieved in 2.5 min and almost complete mineralization (96%) was also possible after only 45 min of irradiation. The efficiency was negatively affected from H2O2 in the UV/H2O2 process and Fe2+ in the photo-Fenton process over a certain concentration. The highest negative effect was observed with solutions containing PO4 triple ions. Required reaction times for complete disappearance of 100 mgl(-1) 4-chlorophenol increased from 2.5 min for an ion-free solution to 30 min for solutions containing 100 mgl(-1) PO4 triple ion and from 45 min to more than 240 min for complete mineralization. The photodegradation of 4-chlorophenol was found to follow the first-order law. CONCLUSION: The results of this study showed that UV irradiation alone can degrade 4-CP, although at very slow rates, but cannot mineralize the compound. The addition of hydrogen peroxide to the system, the so-called UV/H2O2 process, significantly enhances the 4-CP degradation rate, but still requires relatively long reaction periods for complete mineralization. The photo-Fenton process, the combination of homogeneous systems of UV/H2O2/Fe2+ compounds, produces the highest photochemical elimination rate of 4-CP and complete mineralization is possible to achieve in quite shorter reaction periods when compared with the UV/H2O2 process. RECOMMENDATIONS AND OUTLOOK: It is more cost effective to use these processes for only purposes such as toxicity reduction, enhancement of biodegradability, decolorization and micropollutant removal. However the most important point is the optimization of the reaction conditions for the process of concern. In such a case, AOPs can be used in combination with a biological treatment systems as a pre- or post treatment unit providing the cheapest treatment option. The AOP applied, for instance, can be used for toxicity reduction and the biological unit for chemical oxygen demand (COD) removal.     

Compound dependence of the relationship log Kow and log BCFL

Linear relatinships between log bioconcentration factor (BCF) and log K^ow for a variety of compounds have been reported many times in the literature. Analysis of the thermodynamics of the two partition processes has, however, shown that they are not analogous and that linear relationships can be expected to have different slopes for structurally unrelated compounds. In this study a set of literature lipid normalized BCF (BCF_L) values of chlorbenzenes (CBs) for rainbow trout and polycyclic aromatic hydrocarbons (PAHs) forDaphnia was put together with literature K_ow values. The slopes of the regression lines for log BCF_L versus log K_ow for the two groups of compounds proved to differ significantly in a statistical test using analysis of variance (ANOVA). The difference, which is of significance for estimates of BCFs in environmental modelling of these types of compounds, is explained by the differences in chemical structure of the two groups of compounds.     

温室气体排放与中国粮食生产

中国用占世界8％的土地养活了世界上1／5的人口，粮食生产已经基本满足了现有人口的需求。但是，生产粮食会向大气释放大最的温室气体。面对全球减少温室气体排放的压力，在粮食生产中，增加农田生态系统的碳固定能力及减少N2O和CH4的排放，直接关系着中国粮食生产的未来发展。文章分析全球和中国温室气体排放清单中粮食生产的作用和意义；利用生物地球化学模型DNDC和中国农业生产数据库，估算中国农田生态系统的土壤碳动态和N2O排放；通过情景分析(Scenario)，预测在不同方案下，中国农田生态系统碳动态和N2O的排放量；提出了我国未来粮食生产应该采取的对策和技术措施。     

不同预处理对电镀污泥电动过程的影响

以风干电镀污泥为电动处理试验材料,水为阳极电解液,柠檬酸-柠檬酸铵缓冲液为阴极电解液,施加25 V直流电压条件下电动运行5 d,研究了水、低浓度木钙和硝酸等预处理对电镀污泥电动过程的影响。结果表明,各处理的阴极电解液pH值变化平稳,都维持在3-3.5较理想的范围。而1%木钙、1%硝酸饱和预处理电镀污泥,明显改变了电动过程中电渗流和电流密度的大小,对电镀污泥Cu、Ni的去除率也有明显增加。其中,木钙、硝酸预处理后对Cu的去除率由对照的13.24%分别提高到19.05%和25.55%,即去除量分别增大3 516.35 mg/kg和7 457.62 mg/kg;木钙、硝酸预处理后对Ni的去除率由对照的14.68%分别提高到16.47%和28.85%,即去除量分别增大800.91 mg/kg和6 359.92 mg/kg。     

饮用水生物处理小试工艺中NH＋４-N的非硝化去除途径分析

通过计算N和DO的质量平衡,研究饮用水生物处理小试工艺中是否存在NH4 -N的非硝化去除途径,并探讨其可能机制.结果表明,当生物流化床和生物滤池进水NH4 -N浓度大于2 mg/L时,前者进水的NH4 -N、NO2--N和NO3--N之和比出水高出0.91 mg/L,后者理论上消耗的DO比实际多约2.90 mg/L,说明这2种工艺中均有氮亏损现象发生,一部分NH4 -N通过与DO无关的非硝化作用被去除.对非硝化去除途径的分析表明,因为反应器对磷元素和有机物的利用不随氮亏损发生变化,可以排除掉同化作用和反硝化作用;因为反应器进水低碳高氮的特性NO2--N的积累与发生氮亏损的废水生物处理系统相似,据此提出在生物膜缺氧内部发生、通过短程硝化和厌氧氨氧化的偶联(或OLAND反应)将NH4 -N和NO2--N同时转变为N2脱除的自养脱氮是饮用水生物处理中氮亏损的可能途径.     

全耦合活性污泥模型(FCASM3)在A+A2/O工艺污水处理厂中的数值模拟应用

基于FCASM3建立了杭州市某污水厂A+A~2/O工艺模型.首先测定该污水处理厂的进水水质组分,以及不同阶段污染物浓度的变化和活性污泥中微生物动力学参数;然后,利用该厂2017年上半年的运行数据对模型进行校核.校核结果显示,该模型能够很好地模拟出系统中各物质的转化情况.最后,利用校核完成的工艺模型对该污水厂的主要工艺参数,包括溶解氧、污泥回流比和混合液回流比,进行多因素正交模拟试验.试验结果表明,该污水处理厂的最佳运行工况为:当A+A~2/O系统的好氧池氧传输速率(Oxygen Transfer Coefficient,KLa)、污泥回流比和混合液回流比分别控制在2 h-1、75%及250%时,好氧池TN出水浓度下降1.28 mg·L~(-1),脱氮效率提高了15.91%,同时该厂污水处理能耗降低.     

Pre- and post-beach response to engineering hard structures using Landsat time-series at the northwestern part of the Nile delta,Egypt

Analyses have been undertaken to examine shoreline positions established from remote sensing data along the northwestern part of the Nile delta from the Abu Qir Bay to Gamasa embayment (∼143 km length). The image data used (MSS, TM and ETM+ sensors) are acquired at unequal intervals between 1972 and 2006, i.e., covering a time span of 34 years. Automated waterline positions extracted from Landsat satellite images during this period of time were computer generated. A digital shoreline analysis software was used to calculate the annual rate of beach changes at 1,432 cross-shore transects prior to (1972–1990) and after protection (1993–2006). On comparison, rates estimated from three statistical approaches (the end point rate, the Jackknife and a weighted linear regression) at corresponding positions are successfully validated with those measured from ground survey. Before protection, results reveal longshore patterns wherein erosion along a coastal stretch gives way to accretion in an adjacent stretch, refining the sub-cells previously identified within the littoral system of the delta. Maximum shoreline retreat occurs along the Rosetta promontory (−138.52 m/year) and along the central bulge of the delta at Burullus headland (−6.07 m/year). In contrast areas of shoreline accretion exist within saddles or embayments between the promontories at west Abu Qir Bay (20.04 m/year), Abu Khashaba saddle (16.17 m/year) and Gamasa embayment (20.68 m/year). These rates of changes have been significantly altered by the construction of intensive shoreline protective structures built from 1990 to combat areas of rapid erosion at both the Rosetta promontory and Burullus–Baltim headland, ∼15-km length in total.     

Do these eggs smell funny to you?: an experimental study of egg discrimination by hosts of the social parasite Polyergus breviceps (Hymenoptera: Formicidae)

Social parasites exploit the behaviours of other social species. Infiltration of host systems involves a variety of mechanisms depending on the conditions within the host society and the needs of the social parasite. For many species of socially parasitic ants, colony establishment entails the usurpation of colonies of other species. This frequently involves the eviction or death of the host colony queen and the subsequent adoption of the invading queen. The social parasite queen achieves host worker acceptance by either manipulating the nest-mate recognition processes of the host or undergoing chemical modification. Little is known, however, about how host workers respond to social parasite eggs or whether host species defend against brood parasitism during parasite invasions. Host species are believed to adopt social parasite offspring because the recent common ancestry between many social parasites and their hosts may grant the sharing of certain characteristics such as chemical cues. Use of multiple host species, however, suggests other processes are needed for the social bond between host and parasite young to form. This study reports the findings of adoption bioassays in which eggs from a slave-maker ant, Polyergus breviceps, were offered to workers of two of its host species from unparasitised or newly parasitised nests to determine whether P. breviceps eggs generally elicit rearing behaviours from multiple host species. Comparisons of parasite egg survival until adulthood with conspecific egg survival reveal that workers of both host species, free-living or newly enslaved, do not typically accept slave-maker eggs. Both host species thus have sufficient discriminatory power to reject social parasite eggs although our hydrocarbon analysis indicates parasite eggs may be adapted to their local host species. Combined these results suggest that host rearing of P. breviceps eggs may reflect an evolutionary equilibrium that is maintained by probability and cost of recognition errors.Communicated by L. Sundström     

Remediation of Kraft E1 and black liquor effluents by biological and chemical processes

We sutdied the application of the bacteria Azotobacter vinellandi on the treatment of effluents from pulp and paper industry. Two types of treatment employing this microorganism were studied: biological treatment isolated and combined with stages of pre- or post-treatment using ozonation or photocatalysis processes. In the biological treatment, the siderophores production by A. vinellandi had a major effect on the efficiency of effluents degradation. Among the different combined treatments, the best results were obtained with the photocatalytic pre-treatment.     

苯酚液相臭氧氧化和复合氧化反应动力学

推导了苯酚液相臭氧氧化和复合氧化（O3/H2O2）反应动力学模型,研究了苯酚液相臭氧氧化和复合氧化过程的降解,得出了苯酚液相臭氧氧化和复合氧化在温度288～313K和pH3.2～9.8条件下的反应动力学,探讨了反应机理,认为：在酸性(pH3.2）及弱酸性（pH6.2～6.5）时,苯酚的臭氧化和复合氧化降解反应均为O3分子的直接氧化过程;在碱性（pH9.8）条件下,苯酚复合氧化降解机理以自由基反应为主。