Modelling the kinetics of UV/H2O2 oxidation of dichloroacetic acid.

The intrinsic reaction kinetics of the decomposition of dichloroacetic acid (DCA) using UV/H2O2 was studied. A complete mathematical model, including the effect of the absorbed radiation intensities and H2O2 concentration was developed. The results of the kinetic measurements were analysed using a complete mathematical model of the experimental device that was used for the laboratory operation (a differential reactor inside a recycle). In this way it was expected to obtain intrinsic kinetic parameters. Experimental data agree well with theoretical predictions esmploying just two kinetic parameters derived from the proposed reaction mechanism.     

UV/H2O2和UV/TiO2/H2O2去除水中微量硝基苯的比较研究

研究比较了UV/H2O2和UV/TiO2/H2O2对水中微量硝基苯的降解效果,并考察了水中常见HCO-3和腐殖酸对硝基苯降解的影响.结果表明,薄膜状TiO2的存在对UV/H2O2降解硝基苯有显著的促进作用,在最佳H2O2投加量2.1 mg/L时,UV/TiO2/H2O2的反应速率常数比UV/H2O2高32.8%;2 min内UV/TiO2/H2O2对硝基苯的去除率达到80%以上.HCO-3和腐殖酸对硝基苯降解有很强的抑制作用,HCO-3和腐殖酸浓度分别为2 mmol/L和3.2 mg/L时,UV/TiO2/H2O2对硝基苯的反应速率常数分别下降84.6%和92.2%.     

O3、O3/H2O2、O3/H2O2/UV去除水中六氯苯的研究

通过O3、O3/H2O2、O3/H2O2/UV等三种氧化工艺,分别对水中的内分泌干扰物--六氯苯的去除效果进行了研究,结果表明催化氧化工艺O3/H2O2、O3/H2O2/UV对六氯苯的去除率明显优于O3工艺.同时三种氧化工艺都存在臭氧投量的最佳值,即投量为4 mg/L时,六氯苯去除率达到最大.     

Removal of pharmaceuticals using combination of UV/H(2)O(2)/O(3) advanced oxidation process

Water and wastewater effluents contain a vast range of pharmaceutical chemicals. The present study aims to determine the potential of the advanced oxidation technology UV/H(2)O(2)/O(3) and its sub-processes (i.e. UV, UV/H(2)O(2), UV/O(3), O(3) and H(2)O(2)/O(3)) for the degradation of the antibiotics ciprofloxacin (CIP) and trimethoprim (TMP), and the antineoplastic drug cyclophosphamide (CPD) from water. Creating AOP conditions improved in most cases the degradation rate of the target compounds (compared with O(3) and UV alone). H(2)O(2) concentration was found to be an important parameter in the UV/H(2)O(2) and H(2)O(2)/O(3) sub-processes, acting as (?)OH initiator as well as (?)OH scavenger. Out of the examined processes, O(3) had the highest degradation rate for TMP and H(2)O(2)/O(3) showed highest degradation rate for CIP and CPD. The electrical energy consumption for both CIP and CPD, as calculated using the E(EO) parameter, was in the following order: UV > UV/O(3) > UV/H(2)O(2)/O(3) > O(3) > H(2)O(2)/O(3). Whereas for TMP O(3) was shown to be the most electrical energy efficient. Twelve degradation byproducts were identified following direct UV photolysis of CIP.     

Size fractionation characterisation of removed organics in reverse osmosis concentrates by ferric chloride

Reverse osmosis membrane separation is the leading method for manufacturing potable purified water. It also produces a concentrate stream, namely reverse osmosis concentrates (ROC), with 10-20% of the water, and almost all other compounds. One method for further treating this stream is by coagulation with ferric chloride. This study evaluates removed organics in ROC treated with ferric chloride. Fractionation with ultrafiltration membranes allows separation of organics based on a nominal molecular weight. A stirred cell system was applied for serial fractionation to classify organic compounds into six groups of < 0.5 kDa, 0.5-1 kDa, 1-3 kDa, 3-5 kDa, 5-10 kDa and > 10 kDa. The study found that raw ROC is rich in low molecular weight compounds (< 1 kDa) with almost 50% of the organics. These compounds include soluble microbial products (SMPs) and smaller humic and fulvic acids as indicated by fluorescence scanning. Conversely, colour was mostly contributed by medium to large molecules of humic and fulvic acids (> 0.5 kDa). Organics and colour were reduced in all molecular groups at an optimum treatment dose 1.48 mM FeCl3 and a pH of 5. However, ferric seemed to effectively remove colour in all size ranges while residual nitrogen was found mostly in the < 1 kDa sizes. Further, the fluorescence indicated that larger humic and fulvic acids were removed with considerable SMPs remaining in the < 0.5 kDa.     

H2O2/UV enhanced degradation of pesticides in wastewater.

Photodegradation of organic pesticides in industrial wastewater was examined in a UV/H2O2/air system. An experimentally determined optimal amount of hydrogen peroxide (0.008% v/v) indicates that hydrogen peroxide concentration controlled the efficiency of photodegradation. Pre-treatment operations such as sedimentation, filtration and coagulation were used to obtain better efficiency of pesticide removal and to cut down on irradiation time. Finally, scale-up experiments in the air-sparged hydrocyclone (ASH) reactor were carried out. After 5 min irradiation of 100 dm3 industrial wastewater almost all pesticides were destroyed. Thus the ASH reactor proved to be an effective contactor for carrying out photochemical reactions.     

Ozonation and combined ozone/H2O2, UV/ozone and UV/H2O2 for treatment of fuel oxygenates MTBE, ETBE, TAME, and DIPE from water--a comparison of removal efficiencies.

Methyl tert-butylether (MTBE) used as fuel oxygenate poses problems for water suppliers since it is persistent in the aquatic environment and the removal efficiency by conventional water treatment methods (aeration or activated carbon filtration) is rather low. Substitution by other ether compounds such as ethyl tert-butylether (ETBE), tert-amylmethylether (TAME) or di-isopropylether (DIPE) is discussed, however, their environmental behaviour is similar to that of MTBE. Experiments investigating the elimination efficiency of AOP were carried out in tap water and water from Lake Constance. The elimination efficiency for all treatment processes was found to follow the order: MTBE < TAME approximately equal ETBE < DIPE For all compounds under investigation, neither pure ozonation nor UV irradiation yield a considerable concentration decline. Only the formation of highly reactive OH radicals shows a potential for removing the ethers from water. Therefore the addition of H2O2 in equimolar ratio prior to ozone admixing proved to be quite efficient. The application of combined UV/H2O2 showed good results in all cases; the best concentration decline was achieved with UV/ozone. The rate of elimination of the three substitutes for MTBE (ETBE, TAME and DIPE) is higher in all processes; nevertheless, no complete removal could be achieved. Therefore, from the point of view of water suppliers, the use of other ethers as substitute for MTBE is posing the same problems as MTBE.     

Survey on production quality of electrodialysis reversal and reverse osmosis on municipal wastewater desalination

Water shortage has become an emerging environmental issue. Reclamation of the effluent from municipal wastewater treatment plant (WWTP) is feasible for meeting the growth of water requirement from industries. In this study, the results of a pilot-plant setting in Futian wastewater treatment plant (Taichung, Taiwan) were presented. Two processes, sand filter - ultrafiltration - reverse osmosis (SF-UF-RO) and sand filter - electrodialysis reversal (SF-EDR), were operated in parallel to evaluate their stability and filtrate quality. It has been noticed that EDR could accept inflow with worse quality and thus required less pretreatment compared with RO. During the operation, EDR required more frequent chemical cleaning (every 3 weeks) than RO did (every 3 months). For the filtrate quality, the desalination efficiency of SF-EDR ranged from 75 to 80% in continuous operation mode, while the conductivity ranged from 100 to 120 μS/cm, with turbidity at 0.8 NTU and total organic carbon at 1.3 mg/L. SF-EDR was less efficient in desalinating the multivalent ions than SF-UF-RO was. However for the monovalent ions, the performances of the two processes were similar to each other. Noticeably, total trihalomethanes in SF-EDR filtrate was lower than that of SF-UF-RO, probably because the polarization effects formed on the concentrated side of the EDR membrane were not significant. At the end of this study, cost analysis was also conducted to compare the capital requirement of building a full-scale wastewater reclamation plant using the two processes. The results showed that using SF-EDR may cost less than using SF-UF-RO, if the users were to accept the filtrate quality of SF-EDR.     

UV/H2O2 degradation of endocrine-disrupting chemicals in water evaluated via toxicity assays.

Due to rising concern regarding the presence of endocrine-disrupting chemicals (EDCs) in surface water and groundwater throughout the United States, Asia and Europe, treatment of these chemicals in drinking water and wastewater to protect human health and the environment is an area of great interest. Many conventional treatment schemes are relatively ineffective in removing EDCs from water and wastewater. This is concerning because these chemicals are biologically active at very low concentrations and effects of mixtures are relatively unknown. 17-alpha-oestradiol (E2) and 17-beta-ethinyl-oestradiol (EE2), suspected EDCs, were degraded significantly by the UV/H2O2 AOP. The UV/H2O2 processes using either low or medium pressure lamps were degraded EDCs by between 80 and 99.3% at a 15 ppm H2O2 concentration and a UV dose of 1,000 mJ/cm2. Significantly greater removal was noted when the removal was based on total oestrogenic activity using a yeast oestrogen screen (YES) assay. These data indicated that a dose of less than 200 mJ/cm2 completely removed oestrogenic activity in lab water. Values for natural waters were slightly higher. A steady state model was developed to determine EDC destruction efficiency in waters of differing quality. The model effectively predicted destruction in water, where concentrations of all scavenging species were known. Based on these results it was concluded than complete destruction of oestrogenic activity was possible under practical advanced oxidation conditions for a variety of water qualities.     

UV/H2O2联用工艺去除水中微量有机污染物的中试研究

为了考察UV/H2O2工艺对微量有机物的去除效果,在砂滤池出水后接UV/H2O2高级氧化中试设备,并投加了特征污染物(阿特拉津、臭味物质2-MIB与Geosmine)。结果表明,UV/H2O2工艺对Geosmine去除效果最好,去除率能达到90%以上,对MIB和阿特拉津的去除效果比较接近,去除率均在50%以上,对UV254的去除率为20%～38%。在UV/H2O2工艺中无溴酸盐生成。     

Heterogeneous catalytic oxidation of hypophosphite by H2O2: pH effect.

Phosphorus chemicals control key aspects of eutrophication and other environmental process. Hypophosphite (HP) originating from manmade and natural sources was evidenced as present in the environment and was investigated rarely. Recently, iron oxide has been used as a catalyst for oxidising organic contaminants with hydrogen peroxide (i.e. heterogeneous Fenton-like reaction). This study focused mainly on the oxidation of 1.0 mM HP by hydrogen peroxide in the presence of a novel iron oxide catalyst (B1 catalyst) which was prepared through a fluidised-bed Fenton reactor (FBR-Fenton). The background experiments including the oxidation experiment of HP by air only, by H2O2 only and adsorption of HP by B1 catalyst were first elucidated. It was found that HP could not be oxidised at all by air and H2O2 at pH 2.5-12 in 24 hours. On the other hand, it could be adsorbed by B1 catalyst with 89.8% removal at pH 2.5 in 5 hours and complete desorption at pH 11.0. Then, we investigated the effects of pH and Fe leaching from the catalyst on the oxidative efficiency of HP. We found that although the removal rate of HP at pH 2.5 is faster than that at pH 4.0, B1 catalyst has a higher HP oxidation efficiency at pH 4.0 than that at pH 2.5. We conclude that it is a major heterogeneous catalytic oxidation by our novel iron oxide catalyst to oxidise HP at pH 4.0. Also, B1 could be a useful and potential catalyst for the treatment of HP wastewater.     

A2/O工艺城市污水处理厂的启动与调试

当曝气池水温为12.9～22.2℃,平均进水CODCr为142 mg/L时,在不接种的条件下,通过投加聚硅硫酸铁(PFSS)和聚丙烯酸(PA),经闷曝和连续进水两个阶段,完成了A2/O工艺城市污水处理厂的启动与调试.闷曝阶段,PFSS投加量为6 mg/L时,可使MLSS提高22%.当PFSS和PA的投加量分别为30 mg/L和0.05 mg/L时,MLSS达到100 mg/L即可进入连续进水阶段,从而缩短了启动时间.污泥培养58 d,MLSS达到3 000 mg/L,CODCr去除率稳定在80%左右,脱碳功能形成,且污泥中存在反硝化细菌和聚磷菌.污泥培养89d,当进水氨氮为10.8～21.4 mg/L时,氨氮去除率稳定在90%以上,硝化功能形成.     

Degradation of macromolecular tannic acid by O3/H2O2

Tannic acid, being polyhydroxyl, is a macromolecule natural organic matter. The efficiency and mechanism of degradation of tannic acid by O3 and O3/H2O2 was studied. The results showed that the addition of H2O2 had no obvious improvement on the ozonation efficiency of tannin. It was observed that the addition of H2O2 decreased the removal efficiency of TOC by 10%. The relative intensity of .OH generated in the O3-H2O2 system was detected by electronic spin resonance (ESR) and it was found that tannin consumed the .OH radicals, which may be associated with the polyhydroxyl structure of tannin. Derived with PFBBr and analysed by GC-ECD, the by-products of tannin ozonation were found to be aldehydes such as acetaldehyde, glyoxal and methyl glyoxal. Analysis with an ion chromatogram showed that the final products of tannin were oxalic acid, ketomalonic acid and oxalic acid, which consisted of 35% of TOC in both systems.     

Effect of H2O2 dose on the thermo-oxidative co-treatment with anaerobic digestion of excess municipal sludge.

Thermo-oxidative treatment, applied at moderate temperatures below the boiling point of water and using hydrogen peroxide as oxidant, has been shown to enhance anaerobic digestion of excess municipal sludge. Due to the high economic impact of chemical addition on the process, a balance between process performance and economic cost has to be established. The effect of three low hydrogen peroxide dosages (0.1, 0.25 and 0.5 gH2O2/gVSSinfluent) applied at 90 degrees C was evaluated. Increases in solids destruction of 13.9, 18.9 and 25.6% with respect to a control were observed when the thermo-oxidative co-treatment was operated at 0.1, 0.25 and 0.5 gH2O2/gVSSinfluent, respectively.     

Degradation of the endocrine disruptor carbofuran by UV, O3 and O3/UV.

The photodegradation of a carbamate insecticide, Carbofuran (CBF), which has been recognised as a potential endocrine disrupting chemical, was studied via different wastewater treatment processes. This study has shown the efficiency of advanced oxidation process, AOP (UV/O3) than those of the direct UV photolysis and ozonation process, by completely removing 0.2 mM CBF and achieving 24% mineralisation within 30min. The initial decay of CBF by UV/O3 accelerated from 0.05 to 0.16 min(-1) as the initial pH increasing from 3.0 to 11.3. The pH-dependency of CBF has also been shown in both ozonation and UV/O3 process. A linear relationship could be found for the latter process in all pH, while for the former process, two stages of reactions (steady and accelerating) were found in the acidic and alkaline pH condition, respectively.     

Treatment of wastewater from a cotton dyeing process with UV/H2O2 using a photoreactor covered with reflective material

Wastewater containing several dyes, including sulfur black from the dyeing process in a textile mill, was treated using a UV/H2O2 process. The wastewater was characterized by a low BOD/COD ratio, intense color and high acute toxicity to the algae species Pseudokirchneriella subcaptata. The influence of the pH and H2O2 concentration on the treatment process was evaluated by a full factorial design 22 with three replicates of the central experiment. The removal of aromatic compounds and color was improved by an increase in the H2O2 concentration and a decrease in pH. The best results were obtained at pH 5.0 and 6 g L(-1). With these conditions and 120 min of UV irradiation, the removal of the color, aromatic compounds and COD were 74.1, 55.1 and 44.8%, respectively. Under the same conditions, but using a photoreactor covered with aluminum foil, the removal of the color, aromatic compounds and COD were 92.0, 77.6 and 59.4%, respectively. Moreover, the use of aluminum foil reduced the cost of the treatment by 40.8%. These results suggest the potential application of reflective materials as a photoreactor accessory to reduce electric energy consumption during the UV/H2O2 process.     

O3、O3/H2O体系处理染料废水酸性嫩黄G的试验研究

以配制的酸性嫩黄G染料废水为研究对象,考察O3、O3/H2O2体系对去除染料废水中的COD.和色度,提高可生化性的效果,分析pH值、初始污染物浓度、H2O2投加量等各种因素对O3氧化染料废水的影响.试验结果表明:臭氧氧化对COD.去除率达55.1%,对色度的去除率接近100%,B/C由原水的0.08上升到03;臭氧化酸...     

Classification of the degradability of 30 pharmaceuticals in water with ozone, UV and H2O2.

Experiments were conducted to assess the degradability of 30 PPCPs, selected on the basis of consumption and environmental relevance, by O3 process, UV process and AOPs consisting of UV/ H2O2, O3/UV and O3/H2O2. A batch reactor with volume of 22L of water including the PPCPs was used. For UV process, combination of UV and H2O2 or O3 that can generate OH radicals was capable of degrading the PPCPs faster than UV radiation alone. On the other hand, O3 process and O3-based/UV-based AOPs could remove a variety of the PPCPs effectively, while some PPCPs such as 2-QCA, DEET and cyclophosphamide showed a relatively low degradability compared with the other PPCPs. However, further evaluation on formation of intermediate products resulting from the degradation of the parent PPCPs will be needed because DOC concentration was not decreased with lowered concentrations of the PPCPs.     

Advanced H2O2 oxidation for diethyl phthalate degradation in treated effluents: effect of nitrate on oxidation and a pilot-scale AOP operation

One of the objectives of this study was to delineate the effect of nitrate on diethyl phthalate (DEP) oxidation by conducting a bench-scale ultraviolet (UV)/H2O2 and O3/H2O2 operations as suggested in a previous study. We also aim to investigate DEP oxidation at various UV doses and H2O2 concentrations by performing a pilot-scale advanced oxidation processes (AOP) system, into which a portion of the effluent from a pilot-scale membrane bioreactor (MBR) plant was pumped. In the bench-scale AOP operation, the O3 oxidation alone as well as the UV irradiation without H2O2 addition could be among the desirable alternatives for the efficient removal of DEP dissolved in aqueous solutions at a low DEP concentration range of 85+/-15 microg/L. The adverse effect in the UV/H2O2 process was significantly greater than that in the UV oxidation alone, and its oxidation was almost halved by the nitrate. However, the nitrate clearly enhanced the DEP oxidation in the O3 oxidation and O3/H2O2 process. Especially, the addition of nitrate almost doubled the DEP oxidation efficiency in the O3/H2O2 process. The series of pilot-scale AOP operations confirmed that about 30-50% of DEP dissolved in the treated MBR effluent streams was, at least, oxidized by the O3 oxidation alone as well as the UV irradiation without H2O2 addition. The UV photolysis of H2O2 was most effective for DEP degradation with an H2O2 concentration of 40 mg/L at a UV dose of 500 mJ/cm2.     

H2O2/O3协同灭活水中隐孢子虫影响因素研究

开展了H2O2/O3灭活隐孢子虫(Cryptosporidium parvum)的研究。考察了H2O2和O3投加比例、过氧化氢作用效果、无机金属离子等因素的影响。结果表明,H2O2/O3协同技术具有最佳的灭活效果,H2O2的投加不仅降低了药剂(O3)的初始浓度(投量2.0mg/L),而且缩短了灭活时间(7.0 min),达到理想的灭活效果(灭活率99.0%以上)时,H2O2/O3摩尔比为0.8;同时考察了水中常见离子对H2O2/O3灭活效果的影响,低浓度的Ca2+,Mg2+和Cu2+等二价金属离子均对灭活起到一定促进作用,一价离子Na+对灭活无明显的作用,而NO-3,HCO-3和Cl-在一定范围内抑制了H2O2/O3对隐孢子虫的灭活。