炼化企业中水紫外线消毒及其影响因素

研究水质对254 nm紫外线透射率的影响,通过动态实验考察了照射时间、254 nm紫外线透射率以及紫外线剂量对炼化企业中水消毒效果的影响并同时考察异养菌、硫酸盐还原菌和铁细菌的光复活及暗修复现象。结果表明,有机物是影响炼化企业中水紫外线消毒的重要因素;紫外线对炼化企业中水中的异养菌具有良好的灭活作用;增加照射时间对消毒效果的提升作用受254 nm紫外线透射率的影响;紫外线透射率在较低的范围内时对消毒效果的影响相对较大,在较高的范围内时影响较小;紫外线剂量-响应曲线受254 nm紫外线透射率的影响;剂量的"成分",即照射时间和透射率的不同组合,也会对消毒效果产生影响;在80 mJ/cm2的剂量下,20 h内异养菌出现了较强烈的光复活和暗修复现象,铁细菌仅出现了明显的光复活现象,硫酸盐还原菌没有表现出明显的复活。     

水质对紫外消毒在两种典型再生水中应用的影响

以大肠杆菌为对象，研究了再生水水质变化对紫外消毒效果和光复活的影响。结果表明，紫外对大肠杆菌有很强的灭活作用，在紫外剂量为4mJ／cm^2时，大肠杆菌的灭活率达到了4．41个对数级。腐殖酸、铁和2种再生水水体中其他溶解性物质会影响光吸收和紫外透射率，但对紫外消毒动力学无影响。在颗粒物浓度为0～200mg／L的范围内，外源高岭土和活性污泥等颗粒物的投加对紫外消毒效果影响较小，而再生水水样W1中原有的2．61／1：g／L的颗粒物则会极大地影响消毒效果，使UV对细菌的灭活出现明显的拖尾现象。腐殖酸会增强紫外损伤大肠杆菌的光复活能力，但2种再生水中细菌的光复活能力相对磷酸盐缓冲溶液（PBS）中减弱，减弱程度在不同水样中有所不同。     

紫外线杀菌效能的研究

自来水的消毒目前普遍采用氯及含氯化合物药剂，消毒过程中产生三卤甲烷等致癌或致突变物质，从而造成水体的二次污染，许多国家已经禁止在消毒中使用含氯药剂。因此，具有安全可靠高效杀菌作用的紫外线消毒技术逐渐发展起来，并越来越受到人们的关注。但是紫外线的使用也有一定的限制，通过紫外线照射时间及进水浊度的变化，研究了具有一定照射强度的紫外灯的杀菌效能变化，并得出了紫外线具有最佳杀菌效果的进水极限浊度和照射时间。同时还研究了紫外线对具有不同抗性的细菌的系灭效率，为饮用水和污水的消毒处理提供了实验基础。     

含盐量与负荷对好氧颗粒中自养与异养菌的影响

研究了含盐量分别为2.5％和5％，有机负荷分别为8 kg COD/(m³·d) 和16 kg COD/(m³·d)条件下好氧颗粒污泥中自养菌和异养菌的成长情况，研究结果如下：(1)系统在高COD负荷条件下抗盐度的冲击能力要强于低负荷条件；(2)从4个反应器对COD的去除效果来看，含盐量对异养菌的影响要低于硝化自养菌；(3)在低负荷情况下，硝化自养菌为优势菌种，在一个周期内产生的NO^-₃-N要高于高负荷，而在高负荷情况下，异养菌为优势菌种。     

鼠伤寒沙门氏菌的紫外灭活及光复活抑制的研究

研究了鼠伤寒沙门氏菌的紫外失活动力学、在日光灯下的光复活现象以及氯对其光复活的抑制。结果表明,鼠伤寒沙门氏菌的紫外失活动力学曲线分为滞后区、一级动力学区、拖尾区三阶段,在PBS中的一级动力学失活速率常数为0.9041 cm2/mJ。而紫外灭活后的鼠伤寒沙门氏菌在日光灯下存在光复活。当紫外剂量为10 mJ/cm2时,鼠伤寒沙门氏菌在日光灯下照射3 h内发生明显的光复活,浓度从8.6×103CFU/mL增加到4.1×106 CFU/mL;但是在紫外消毒后,投加1 mg/L的氯可以有效抑制该细菌的光复活,投加2 mg/L的氯可以在10 min内全部灭活。因此,紫外-氯联合消毒能够有效的抑制鼠伤寒沙门氏菌细菌光复活,使其得到高效灭活。     

低强度紫外线催化降解活性艳红X-3B溶液研究

研究了低强度紫外线对活性艳红X-3B溶液的处理效果．考察了紫外线波长、溶液pH、起始浓度、催化剂用量、温度及曝气条件对染料降解的影响。结果表明，365nm紫外线(UV356nm)的处理效果明显优于254nm紫外线(UV254nm)，反应最适pH为3．0～5．0，最佳TiO2投加量为2．0g／L，最适温度为40℃，通入空气或氧气均能加速活性艳红X-3B的降解。在上述条件下，起始浓度为50mg／L的活性艳红X-3B在150min内可完全分解。     

紫外联合过硫酸盐杀灭水中大肠杆菌

为提高UV杀菌效率并同时解决UV杀菌存在光复活现象的问题,以大肠杆菌为研究对象,采用UV-PS(紫外联合过硫酸盐)体系杀灭水中大肠杆菌,研究了各因素对UV-PS体系杀菌效果的影响,并考察复活光强度(0～42μW·cm~(-2))对不同体系处理后大肠杆菌复活的影响,最后分析其杀菌机理。结果表明:UV-PS体系杀菌效率高于单独UV及单独PS杀菌,15 mJ·cm~(-2)紫外剂量下,0.3 mmol·L-1 PS的加入较单独UV杀菌时大肠杆菌对数去除率增加1.0个对数级;且一定范围内大肠杆菌对数去除率随着PS初始浓度的增加而增加;中性条件更有利于大肠杆菌杀灭;Fe2+对大肠杆菌杀灭产生抑制效果;大肠杆菌经UV-PS体系处理后光复活能力明显下降,且仅在较强的复活光照下才会产生一定的光复活;UV-PS体系较单独UV杀菌时大肠杆菌细胞形态破坏更为严重,UV-PS体系产生的硫酸根自由基首先攻击细胞表面,使得细胞结构破损,细胞膜破裂,进而对其内容物进行氧化损伤,导致细胞死亡。UV-PS体系杀菌效率高且对大肠杆菌的光复活现象抑制明显,具有一定的应用前景。     

紫外线-茶多酚/次氯酸钠联合消毒管网微生物特性分析

紫外线对微生物的杀灭效果较好,但持续性差,引入茶多酚作为辅助消毒剂,采用管网动态模拟系统,对比了紫外线-茶多酚联合消毒和紫外线-次氯酸钠联合消毒后管网微生物的总量、群落分布和有机物荧光特性变化。结果表明,紫外线-茶多酚联合消毒对微生物的灭活效果比紫外线-次氯酸钠联合消毒更好,并且对致病菌和耐氯性细菌也有很强的杀灭能力。紫外线-茶多酚联合消毒后,酪氨酸类物质荧光和类腐殖酸物质荧光特性产生变化,说明这2类物质含量大量减少,可能会影响微生物的生长;此外,管壁生物膜中出现了儿茶素、表儿茶素类物质,这说明茶多酚与管壁微生物发生了相互作用;紫外线-次氯酸钠联合消毒后酪氨酸类的荧光特征峰发生蓝移,这说明次氯酸进入微生物内发挥氧化作用。     

利用UVC去除低浓度苯的实验研究

探讨了不同实验参数对苯的UVC去除效果的影响，获得了苯的去除率与苯的初始浓度、气体流量、相对湿度和氧气含量等参数之间的关系。数据表明，在实验条件范围内，苯的去除率的倒数与苯初始浓度、气体流量之间为线性关系；苯的去除率随相对湿度的增加呈现先升高后缓慢降低的关系，最佳相对湿度值在30%～50%之间；苯的去除率随氧气量的增加而缓慢增加；波长为185+254 nm的UV与254 nm的UV相比净化效果更为理想。还分析了苯降解产生的中间产物，探讨了苯的降解机理。     

超声波对城市污水处理厂出水消毒的研究

对于城市污水处理厂出水，传统消毒方法存在很多的弊端，实验对超声波消毒进行研究，探索城市污水处理厂出水消毒的新工艺。采用21.51 kHz与32.36 kHz 2个频率的超声波,通过改变超声波的频率、强度、辐照时间等因子，考察总大肠菌群的灭活情况。对超声波消毒效果、消毒机理及超声波与紫外线协同消毒效果进行了研究探讨。结果表明，超声消毒效果随超声时间及声密度的增大而增大；时间和声密度相同情况下，32.36 kHz超声的消毒效果强于21.51 kHz；对水体进行少量曝气时，消毒效果明显增强。超声波消毒技术与紫外消毒技术联用，10 s超声波预处理加20 s紫外消毒，总大肠菌群灭活率可达到4.5个对数单位，要优于1 min紫外消毒达到的3.7个对数单位，且能耗更低。     

污水紫外消毒微生物光复活原理及其控制技术

紫外消毒技术因其具有操作简单、无有害副产物、经济高效等优势,在污水处理中越来越广泛被应用.但其无剩余消毒能力,微生物在光照条件下进行修复而实现复活,从而导致出水微生物数量增多.综述了国内外紫外消毒出现的光复活现象,阐述了污水紫外消毒微生物光复活原理和控制技术.     

Wastewater disinfection alternatives: chlorine, ozone, peracetic acid, and UV light.

Disinfection tests were carried out at pilot scale to compare the disinfection efficiency of ozone, sodium hypochlorite (NaOCl), peracetic acid (PAA), and UV irradiation. Total coliforms, fecal coliforms, and Escherichia coli were monitored as reference microorganisms. Total heterotrophic bacteria (THB) were also enumerated by cytometry. At similar doses, NaOCl was more effective than PAA, and its action was less affected by contact time. The results obtained by ozonation were comparable for total coliforms, fecal coliforms, and E. coli. On the contrary, some differences among the three indicators were observed for NaOCl, PAA, and UV. Differences increased with increasing values of the disinfectant concentration times contact time (C x t) and were probably the result of different initial counts, as total coliforms include fecal coliforms, which include E. coli. The UV irradiation lead to complete E. coli removals, even at low doses (10 to 20 mJ/cm2). Total heterotrophic bacteria appeared to be too wide a group to be a good disinfection indicator; no correlation was found among THB inactivation, dose, and contact time.     

Inactivation of Ascaris eggs in soil by microwave treatment compared to UV and ozone treatment

This study reports on the effect of microwave radiation for inactivation of Ascaris lumbricoides eggs in 25 g of soil compared to ultraviolet irradiation and ozone expose. Microwave radiation at 700 W with 14% water content (w/w) achieved approximately 2.5 log inactivation of eggs in soil within 60 s. On the other hand, UV irradiation at 3 mW cm⁻² with and without shaking soil for 3600 s achieved approximately 0.32 and 0.01 log inactivation of eggs, respectively. In ozone treatment, 0.13 log inactivation of eggs was achieved with 5.8 ± 0.7 mg L⁻¹ of dissolved ozone dose for 30 min in a continuous diffusion reactor. In addition, the inactivation of eggs by three disinfection techniques was conducted in water in order to compare the inactivation efficiency of eggs in soil. The inactivation efficiency of microwave radiation was found to be no significant difference between in soil and water. However, the inactivation efficiency of UV irradiation was significantly increased in water while in ozone expose there was no significant difference between in soil and water. Microwave treatment thus proved to be the most efficient method in controlling A. lumbricoides eggs in soil.     

Effect of chlorination and ultraviolet disinfection on tetA-mediated tetracycline resistance of Escherichia coli

Antibiotic-resistant bacteria are an emerging threat to public health during drinking water consumption and reclaimed water reuse. Several studies have shown that the proportions of antibiotic-resistant bacteria in waters may increase when exposed to low doses of UV light or chlorine. In this study, inactivation of tetracycline-resistant Escherichia coli and antibiotic-sensitive E. coli by UV disinfection and chlorination was compared to determine the tolerance of tetracycline-resistant E. coli to UV light and chlorine, and tetracycline resistance of a tetracycline-resistant E. coli population was studied under different doses of the disinfectants. Our results showed that relative to antibiotic-sensitive E. coli, tetracycline-resistant E. coli had the same tolerance to UV light and a potentially higher tolerance to chlorination. The mortality frequency distributions of tetracycline-resistant E. coli exposed to tetracycline were shifted by both chlorination and UV disinfection. When compared to the hemi-inhibitory concentrations (IC₅₀) of tetracycline-resistant E. coli with no exposure to UV or chlorination, the IC₅₀ of tetracycline-resistant E. coli treated with tetracycline was 40% lower when inactivation by UV light or chlorination reached 3-log but was 1.18 times greater when inactivation by chlorination reached 4.3-log. Chlorination applied to drinking water or reclaimed water treatment may increase the risk of selection for highly tetracycline-resistant E. coli.     

Treatment of Arctic wastewater by chemical coagulation,UV and peracetic acid disinfection

Conventional wastewater treatment is challenging in the Arctic region due to the cold climate and scattered population. Thus, no wastewater treatment plant exists in Greenland, and raw wastewater is discharged directly to nearby waterbodies without treatment. We investigated the efficiency of physicochemical wastewater treatment, in Kangerlussuaq, Greenland. Raw wastewater from Kangerlussuaq was treated by chemical coagulation and UV disinfection. By applying 7.5 mg Al/L polyaluminium chloride (PAX XL100), 73% of turbidity and 28% phosphate was removed from raw wastewater. E. coli and Enterococcus were removed by 4 and 2.5 log, respectively, when UV irradiation of 0.70 kWh/m³ was applied to coagulated wastewater. Furthermore, coagulated raw wastewater in Denmark, which has a chemical quality similar to Greenlandic wastewater, was disinfected by peracetic acid or UV irradiation. Removal of heterotrophic bacteria by applying 6 and 12 mg/L peracetic acid was 2.8 and 3.1 log, respectively. Similarly, removal of heterotrophic bacteria by applying 0.21 and 2.10 kWh/m³ for UV irradiation was 2.1 and greater than 4 log, respectively. Physicochemical treatment of raw wastewater followed by UV irradiation and/or peracetic acid disinfection showed the potential for treatment of arctic wastewater.     

Point-of-use water disinfection using UV light-emitting diodes to reduce bacterial contamination

The treatment process described in this research explores the impact of exposing water samples containing fecal coliforms to the radiation produced by single ultraviolet (UV) light-emitting diodes (LEDs) operating at 265 nm. UV LEDs are long lasting, compact in size and produce more efficient light output than traditional mercury-vapour bulbs, making them ideal for application in point-of-use disinfection systems, such as in remote areas. In this study, contaminated water samples containing either a pure culture of Escherichia coli or tertiary effluent from the City of Regina Wastewater Treatment Plant were used to study the application and efficiency of using UV LEDs for water disinfection. The results indicate that bacterial inactivation was achieved in a time-dependent manner, with 1- and 2.5-log E. coli reductions in water following 20 and 50 min of UV LED exposure, respectively. Ultraviolet radiation was less effective in reducing coliform bacteria in wastewater samples due to the elevated turbidity levels. Further work remains to be completed to optimize the application of UV LEDs for point-of-use disinfection systems; however, the results from this study support that bacterial inactivation using UV LEDs is possible, meriting further future technological development of the LEDs.     

Phototransformation of ibuprofen and ketoprofen in aqueous solutions

The UV (254 nm) and UV/VUV (254/185 nm) photolysis of two anti-inflammatory drugs, ibuprofen and ketoprofen, have been studied in aqueous solutions as a possible process for the removal of non-biodegradable compounds.We have examined the effects of dissolved oxygen and initial target concentration. Upon irradiation at 254 nm, the decomposition rate of ketoprofen is almost forty times higher as it of ibuprofen whilst VUV irradiation only increased the ibuprofen decomposition rate. The presence of dissolved oxygen accelerated the photodegradation of ibuprofen, whereas no effect was observed on the degradation of ketoprofen. The maximum quantum yield for the phototransformation was 0.2. The rate of mineralization in both cases was ∼60%, even after 1 h of treatment and this suggests the formation of stable by-products which were identified using GC-MS and HPLC-MS, respectively.     

Effects of wastewater disinfection on waterborne bacteria and viruses.

Wastewater disinfection is practiced with the goal of reducing risks of human exposure to pathogenic microorganisms. In most circumstances, the efficacy of a wastewater disinfection process is regulated and monitored based on measurements of the responses of indicator bacteria. However, inactivation of indicator bacteria does not guarantee an acceptable degree of inactivation among other waterborne microorganisms (e.g., microbial pathogens). Undisinfected effluent samples from several municipal wastewater treatment facilities were collected for analysis. Facilities were selected to provide a broad spectrum of effluent quality, particularly as related to nitrogenous compounds. Samples were subjected to bench-scale chlorination and dechlorination and UV irradiation under conditions that allowed compliance with relevant discharge regulations and such that disinfectant exposures could be accurately quantified. Disinfected samples were subjected to a battery of assays to assess the immediate and long-term effects of wastewater disinfection on waterborne bacteria and viruses. In general, (viable) bacterial populations showed an immediate decline as a result of disinfectant exposure; however, incubation of disinfected samples under conditions that were designed to mimic the conditions in a receiving stream resulted in substantial recovery of the total bacterial community. The bacterial groups that are commonly used as indicators do not provide an accurate representation of the response of the bacterial community to disinfectant exposure and subsequent recovery in the environment. UV irradiation and chlorination/dechlorination both accomplished measurable inactivation of indigenous phage; however, the extent of inactivation was fairly modest under the conditions of disinfection used in this study. UV irradiation was consistently more effective as a virucide than chlorination/dechlorination under the conditions of application, based on measurements of virus (phage) diversity and concentration. Taken together, and when considered in conjunction with previously published research, the results of these experiments illustrate several important limitations of common disinfection processes as applied in the treatment of municipal wastewaters. In general, it is not clear that conventional disinfection processes, as commonly implemented, are effective for control of the risks of disease transmission, particularly those associated with viral pathogens. Microbial quality in receiving streams may not be substantially improved by the application of these disinfection processes; under some circumstances, an argument can be made that disinfection may actually yield a decrease in effluent and receiving water quality. Decisions regarding the need for effluent disinfection must account for site-specific characteristics, but it is not clear that disinfection of municipal wastewater effluents is necessary or beneficial for all facilities. When direct human contact or ingestion of municipal wastewater effluents is likely, disinfection may be necessary. Under these circumstances, UV irradiation appears to be superior to chlorination in terms of microbial quality and chemistry and toxicology. This advantage is particularly evident in effluents that contain appreciable quantities of ammonia-nitrogen or organic nitrogen.