Urban wastewater disinfection by filtration technologies

The microbiological quality of effluents from different macrofiltration systems (pressure sand filter and disc filter) used as pre-treatment and membrane technologies (microfiltration and ultrafiltration) was evaluated in order to determine their possible application as alternatives to disinfection of urban wastewater prior to reutilization. Microbiological quality was determined by reference to nematode egg content, fecal coliforms, E. coli and somatic coliphages. Pathogenic nematode eggs were efficiently retained by the macrofiltration systems. However, since other types of nematode eggs were present in the effluents treated by both systems, the possibility of such infective agents appearing after this type of treatment cannot be discounted. The membrane technologies proved highly efficient at retaining micro-organisms, achieving effluents of excellent microbiological quality. However, the effluents could not be classified as sterile, since contamination of permeation zones gave rise to the presence of micro-organisms. This result casts doubt on the validity of using the fecal coliform indicator to assess microbiological quality of effluents from these systems. Differences between the two membrane technologies were noted with regard to viral particle retention capacity, with only the ultrafiltration module achieving effluents with total absence of fecal contamination indicators. The macrofiltration systems may present problems when used as pre-treatments to standard disinfection systems (UV radiation, reactive oxidant disinfection). Such problems do not arise with the membrane technologies, which offer a valid alternative for the disinfection of urban wastewater prior to reutilization.     

Occurrence of ochratoxin A in cocoa beans: Effect of shelling

The aim of this study was to investigate the influence of the shelling process on the presence of ochratoxin A (OTA) in cocoa samples. Twenty-two cocoa samples were analysed for the determination of OTA before (cocoa bean) and after undergoing manual shelling process (cocoa nib). In order to determine OTA contamination in cocoa samples, a validated high-performance liquid chromatography (HPLC) method with fluorescence detection was used for the quantitative analysis of ochratoxin A (OTA). In both types of samples, OTA was extracted with methanol-3% sodium hydrogen carbonate solution and then purified using immunoaffinity columns prior to HPLC analysis. Due to the fact that different recovery values were obtained for OTA from both types of samples, a revalidation of the method in the case of cocoa nibs was needed. Revalidation was based on the following criteria: Selectivity, limits of detection and quantification (0.03 and 0.1 µg kg^-1, respectively), precision (within-day and between-day variability) and recovery 84.2% (RSD = 7.1%), and uncertainty (30%). Fourteen of the twenty-two cocoa bean samples (64%) suffered a loss of OTA of more than 95% due to shelling, six samples suffered a loss of OTA in the range 65-95%, and only one sample presented a reduction of less than 50%. The principal conclusion derived from this study is that OTA contamination in cocoa beans is concentrated in the shell; therefore, improvements of the industrial shelling process could prevent OTA occurrence in cocoa final products.     

UFC法测定管网水的DBP生成量

我国主要采用前体物试验(FP试验)对饮用水中消毒副产物(DBP)的形成进行评估,但这种方法无法对配水系统中DBP产量进行评估。为此借鉴美国的评估方法,根据中国的具体情况,建立了评估配水管网中消毒副产物产量的新方法———UFC试验(uniformformationconditions),确立了UFC试验的条件:温度为(20±1.0)℃,pH值为7.5±0.2,培养时间为(24±1)h,24h后游离余氯为(1.0±0.4)mg/L,并建立了UFC的分析检测方法。     

成都市饮用水中消毒副产物的变化研究

以成都市第六水厂的工艺出水和管网水为测试对象，研究了常规处理工艺对消毒副产物及其前体物的去除特性，分析了消毒副产物在管网中的变化规律，并且提出了控制饮用水中消毒副产物的对策。研究结果表明：①成都市自来水中消毒副产物的主要成分为卤乙酸；②常规处理工艺对三卤甲烷前体物和卤乙酸前体物均有很好的去除效果(去除率为50％左右)，但对卤乙酸(HAAs)和三卤甲烷(THMs)却无去除作用；③预氯化产生的THMs、HAAs分别占管网中此类物质最高浓度的22％和50％；④应该以管网入口处三氯甲烷、卤乙酸的浓度作为整个管网的控制指标。     

饮用净水的直流电解消毒应用研究

主要研究直流电解杀菌的影响因素及其应用于饮用净水的消毒。电流密度越大，杀菌效果越好。在额定水流量1m^3/h，选定电流密度7．5mA/cm^2的情况下，水样的pH值低，杀菌效果好，水中的氨氮含量越高，杀菌效果越差，水中的氯离子浓度越高，杀菌效果越好。在电解杀菌应用于饮用净水的消毒中，杀菌效果十分显著，出水符合饮用净水卫生标准（CJ94－1999），且具有持续杀菌作用，可作为一种消毒装置应用于饮用净水的消毒。     

芯壳结构复合消毒粉的制备及其对2-CEES的消毒性能研究

为改善固体消毒剂的流散性以及对芥子气模拟剂2-氯乙基乙基硫醚(2-CEES)的消毒能力,以环境友好的过氧化物单过氧邻苯二甲酸镁(MMPP)为芯材,以不同吸附材料为壁材,通过流化床包衣技术,制备了新型芯-壳结构复合消毒粉MgO/MMPP,Al_2O_3/MMPP,活性白土(HEAC)/MMPP,并以羟丙基甲基纤维素(HPMC)/MMPP为对照研究了复合消毒粉微观形貌、粒径、流散性能、稳定性和2-CEES的消毒能力等性质。结果表明,复合消毒粉在提高MMPP流散性的同时,表现出良好的热稳定性,且消毒能力有了较大提高,其中MgO/MMPP,Al_2O_3/MMPP对2-CEES的消毒率高于99%,反应产物主要为2-氯乙基乙基亚砜和2-氯乙基乙基砜。通过流化床制备的复合消毒粉比MMPP有更好的消毒能力,这为新型吸附反应型洗消剂的开发提供了技术支撑。     

Inactivation of Escherichia coli in Na2SO4 electrolyte using boron-doped diamond anode

Electrochemical disinfection in chloride-free electrolyte has attracted more and more attention due to advantages of no production of disinfection byproducts (DBPs), and boron-doped diamond (BDD) anode with several unique properties has shown great potential in this field. In this study, inactivation of Escherichia coli (E. coli) was investigated in Na₂SO₄ electrolyte using BDD anode. Firstly, disinfection tests were carried on at different current density. The inactivation rate of E. coli and also the concentration of hydroxyl radical (OH) increased with the current density, which indicated the major role of OH in the disinfection process. At 20 mA cm⁻² the energy consumption was the lowest to reach an equal inactivation. Moreover, it was found that inactivation rate of E. coli rose with the increasing Na₂SO₄ concentration and they were inactivated more faster in Na₂SO₄ than in NaH₂PO₄ or NaNO₃ electrolyte even in the presence of OH scavenger, which could be attributed to the oxidants produced in the electrolysis of SO₄²⁻, such as peroxodisulfate (S₂O₈²⁻). And the role of S₂O₈²⁻ was proved in the disinfection experiments. These results demonstrated that, besides hydroxyl radical and its consecutive products, oxidants produced in SO₄²⁻ electrolysis at BDD anode played a role in electrochemical disinfection in Na₂SO₄ electrolyte.     

Ozonation of Urban Waste Water in Tourist Zone

Ozone dose is adjusted as a function of the treated flow so that the residual ozone is maintained between 0.2 and 0.6 g/m³. Total coliform count is then reduced from 10⁷ to 10³/ml. In the treated effluent, entero-viruses have not been found in 20 liters volume samples. Color and chemical oxygen demand are also reduced.