Characterization of changes in extracellular polymeric substances and heavy metal speciation of waste activated sludge during typical oxidation solubilization processes

Biopolymer solubilization is considered to be the rate-limiting stage of anaerobic digestion of waste activated sludge(WAS). Oxidation processes have been proven to be effective in disrupting sludge flocs and causing solubilization of the solid biopolymers. In this study,WAS was treated by NaNO2 or H2 O2 oxidation at p H of 2. The changes in extracellular polymeric substances properties and the speciation of heavy metals were investigated. The results revealed that both NaNO2 and H2 O2 treatments were effective in solubilizing organics in WAS, while the conversion of biopolymers in the two treatment processes was different. Free nitrous acid destroyed the gel network structure of EPS, and organic materials were released from the solid phase to the supernatant. Indigenous peroxidase catalyzed H2 O2 to produce hydroxyl radicals which caused significant solubilization of biopolymers, and the protein-like substances were further degraded into micro-molecule polypeptides or amino acids at high dosages of H2 O2. During the oxidation processes, Zn, Cd and Cu, with excellent mobility, tended to migrate to the supernatant, and thus were easy to remove through the liquid–solid separation process. Ni and As showed moderate migration ability, of which the residual fraction tended to transform into reducible and soluble fractions. With poor mobility, Cr and Pb mainly existed in the forms of residual and oxidizable fractions, which were difficult to dissolve and remove from WAS. Both NaNO2 and H2 O2 treatment resulted in the enhancement of sludge solubilization efficiency and heavy metal mobility in WAS, but different heavy metals showed distinct migration and transformation behaviors.     

Atmospheric photochemistry and secondary aerosol formation of urban air in Lyon, France

Photochemical aging of volatile organic compounds (VOCs) in the atmosphere is an important source of secondary organic aerosol (SOA). To evaluate the formation potential of SOA at an urban site in Lyon (France), an outdoor experiment using a Potential Aerosol Mass (PAM) oxidation flow reactor (OFR) was conducted throughout entire days during January-February 2017. Diurnal variation of SOA formations and their correlation with OH radical exposure (OHexp), ambient pollutants (VOCs and particulate matters, PM), Relative Humidity (RH), and temperature were explored in this study. Ambient urban air was exposed to high concentration of OH radicals with OHexp in range of (0.2–1.2)×10¹² molecule/(cm³?sec), corresponding to several days to weeks of equivalent atmospheric photochemical aging. The results informed that urban air at Lyon has high potency to contribute to SOA, and these SOA productions were favored from OH radical photochemical oxidation rather than via ozonolysis. Maximum SOA formation (36 µg/m³) was obtained at OHexp of about 7.4 × 10¹¹molecule/(cm³?sec), equivalent to approximately 5 days of atmospheric oxidation. The correlation between SOA formation and ambient environment conditions (RH & temperature, VOCs and PM) was observed. It was the first time to estimate SOA formation potential from ambient air over a long period in urban environment of Lyon.     

The efficacy of an oxidation pond in mineralizing some industrial waste products with special reference to fluorene degradation: a case study

The efficacy of the oxidation pond on the outskirts of the 10th of Ramadan, the main industrial city, in Egypt was examined. Samples of wastewater collected from the inlet and the outlet were screened for some priority pollutants. Acenaphthene and fluorene were the most frequently detected polycyclic aromatic hydrocarbons, while dimethyl phthalate was the most frequently detected phthalate ester. The spectrum of pollutants, their concentrations and frequencies were similar in the inlet and the outlet, indicating an inferior mineralization capability of the pond. Several degradative bacterial strains were isolated from the pond and grown on M56 minimal media supplemented with different pollutants as the carbon source. The efficacy of pure and mixed cultures to break down fluorene, the most frequently detected pollutant was examined. Fluorene degradation was fast in the first 10 days, then followed by a slow phase. Mixed culture had a higher rate of fluorene degradation in comparison to pure cultures. High performance liquid chromatography analysis of fluorene degradation showed three degradative metabolites. But GC/MS analysis detected one compound, identified as acetamide. The present work has indicated the poor efficacy of the pond. Lack of primary treatment of industrial effluent at factory level, coupled with shock loads of toxicants that may damage the microorganisms and their degradative capabilities are presumably main factors behind such inferior performance. Moreover, the type of pollutants discharged into the pond tend to fluctuate and change depending on the rate from the factories discharge and work shifts. Such irregular feeding of persistent pollutants may have led to a wash out of specialized strains of bacteria capable to degrade such persistent pollutants.     

New insights into FeS/persulfate system for tetracycline elimination: Iron valence, homogeneous-heterogeneous reactions and degradation pathways

In this study, complete tetracycline（TTC） and above 50% of total organic carbon（TOC） were removed by Fe S/PS after 30 min under optimized conditions. Although free radicals and high-valent iron ions were identified to generate in the process, the apparent similarity between intermediate products of Fe S/PS, Fe/PS, and UV/PS systems demonstrated that the degradation of TTC was due to sulfate radicals(SO₄^·-) and hydroxyl radicals（ ·OH）. Based on the reaction between free radi...     

Solvent-free mechanochemical mild oxidation method to enhance adsorption properties of chitosan

• Solvent-free chitosan oxidation is obtained by rapid mechanochemical reaction. • Different oxidants induce very diverse physicochemical changes on chitosan. • Oxidized chitosan with persulfate or percarbonate has improved adsorption capacity. • Uptake on oxidized chitosan with persulfate is 125-fold faster than on pristine one. Oxidation has been profitably utilized to improve some properties of chitosan. However, only solvent-based oxidation procedures have been proposed so far, which are hardly feasible at industrial scale in an economic way because of product recovery cost. In this study, a solvent-free, rapid, and effective oxidation method is proposed. It is based on direct solid-state reaction between chitosan and oxidant powder in a mechanochemical reactor. Results prove that by short high energy ball milling (<3 h) it is possible to achieve diverse physicochemical modifications employing different reagents. Apart from polysaccharidic chain shortening, persulfate provokes high amorphization and induces formation of ketonic groups; percarbonate heightens deacetylation degree, preserving in part crystallinity; calcium peroxide merely deprotonates amino groups and increases amorphization degree. Adsorption tests with the azo-dye reactive red 2 show that adsorption capacity of chitosan co-milled with persulfate (974 mg/g milled product), which is the best performing adsorbent, is twice that of pristine chitosan, while adsorption rate is outstandingly boosted (125 times).     

柠檬酸-Fe（Ⅱ）／K2S2O8降解泥水体系中敌草隆的研究

研究了泥水体系中柠檬酸-Fe（Ⅱ）／K2SO8降解敌草隆时各影响因子的作用机制,通过正交实验确定了反应的最佳操作条件为：K2SO8浓度为2．0mmol／L,Fe（Ⅱ）浓度为1．0mmol／L,柠檬酸浓度为0．5mmol／L,反应时间为120min,pH=7．0。此奈件下,0．1mmol／L敌草隆降解率可达97．6％。采用分子探针竞争实验鉴定了体系中产生的硫酸根自由基。     

优势微生物强化水解—多级接触氧化工艺处理屠宰废水

结合工程实例,本文对优势微生物强化水解—多级接触氧化处理屠宰废水工艺及设计体会进行了讨论。设计进水COD、BOD5、SS、NH3-N、动植物油为2300~2700mg/L、900~1300mg/L、600~800mg/L、100~120mg/L、70~90mg/L,出水为90mg/L、20mg/L、60mg/L1、0mg/L1、0 mg/L。实际运行结果表明:主要出水指标COD、BOD5、SS、NH3-N、动植物油的去除率分别可达到97.9%、98.6%、93.7%、93.4%、90.7%。该工艺具有占地少、建设成本低、运行可靠、稳定达标、剩余污泥少、运行成本低、维护简便等优点。     

煤矿矿井乏风瓦斯利用方法浅谈

甲烷是仅次于二氧化碳的重要温室气体,甲烷排入大气而引起气候异常以及对臭氧层的破坏,已经成为全世界共同面临的重大问题。矿井乏风是最大的甲烷工业排放源,收集和利用煤矿乏风瓦斯,减少温室气体排放,是我国面临的紧迫任务。本文根据近几年从事矿井乏风处理项目环评工作经验,对目前煤矿所采用的乏风氧化处理方法进行了探讨,并对乏风处理后带来的环境效益进行了阐述。     

快速法与重铬酸钾回流法测定CODcr的比较

通过回流法测定CODcr分析方法与快速法分别对不同水质类型的水样同时测定分析,找出了两者间存在的一些相关性规律.     

水体中四环素类抗生素的去除技术研究进展

四环素类抗生素因其可以防治人类和动物由病菌引起的疾病,同时又能用作生长促进剂以加快动物生长,目前在国内外被大量使用。抗生素的使用甚至滥用对自然环境造成不容忽视的污染,并进一步对人类身体健康产生潜在危害。从常规处理、膜处理、化学氧化和吸附等角度讨论了国内外对四环素类抗生素去除技术的研究进展,为环境水体中四环素类抗生素污染的有效去除提供了方向。