Potential of UV/H2O2 oxidation for enhancing the biodegradability of municipal reverse osmosis concentrates

UVC/H2O2 and VUV/H2O2 oxidation processes were evaluated for the degradation of organic pollutants in reverse osmosis concentrate (ROC) produced from a municipal secondary effluent. It was found that the oxidation by UVC/H2O2 and VUV/H2O2 processes could be described as a pseudo first-order reaction. For UVC increased oxidation occurred with increasing H2O2 dosage up to 2 mM above which improvement in oxidation performance decreased. At the same H2O2 dosage, VUV irradiation gave better overall oxidation performance. Compared with UVC/6 mM H2O2, VUV/2 mM H2O2 gave a greater rate of reduction of chemical oxygen demand, but a lower rate for reduction of dissolved organic carbon, suggesting that oxidation of organics by the two methods followed different pathways. The change of absorbance at 254 nm and fluorescence excitation emission matrix spectra of irradiated samples indicated that the large and complex compounds were fragmented rapidly by the *OH, resulting in rapid decolourisation. The biodegradability of the organics in the ROC was increased from 11% to 35% after 1 h treatment by UVC/3 mM H2O2, whereas a greater increase (41%) was obtained with VUV/2 mM H2O2. This increase in biodegradability indicates the potential for employing a subsequent biological treatment process.     

Advanced oxidation processes: mechanistic aspects

The reactive intermediate in Advanced Oxidation Processes (AOPs) is the *OH radical. It may be generated by various approaches such as the Fenton reaction (Fe2+/H2O2), photo-Fenton reaction (Fe3+/H2O2/hnu), UV/H2O2, peroxone reaction (O3/H2O2), O3/UV, O3/activated carbon, O3/dissolved organic carbon (DOC) of water matrix, ionizing radiation, vacuum UV, and ultrasound. The underlying reactions and *OH formation efficiencies are discussed. The key reactions of *OH radicals also addressed in this review.     

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.     

水工模型多条有压隧洞联合泄流糙率校正方法

针对水利水电工程多条有压隧洞联合泄流时传统的糙率修正方法工作量大且精度不高这一问题,对多条有压隧洞联合泄流的糙率校正方法进行研究,采用一封闭的方程组求解各有压隧洞的水位校正值和实际过流量。此方程组考虑了有压隧洞间的互相影响,且仅需测量1组次多条有压隧洞同时泄流时的水位、流量数据。该方法在金沙江流域其宗水电站5条有压隧洞联合泄流模型试验中的应用表明,计算简单方便,可节省大量时间,糙率校正后的试验结果准确可靠。     

示踪法对小浪底坝区绕坝渗漏通道的研究

小浪底水库运行以来,左坝肩的渗漏水量偏大,当库水超过235 m高程时,排水量急剧增加.将库水中D,18O,3H作为"事件"示踪剂,用来进行绕坝渗流场及渗漏通道的调查,配合人工示踪、连通试验等方法,查清渗漏水补给来源、渗漏层位等.天然示踪试验和连通试验证实:左坝肩帷幕下部的T3-11中存在强渗漏,库水入渗到T14,T13-1透水层,然后通过F28,F235,F238等断层补给到深部的T13-1,最后由揭露该地层的30#排水洞排出.     

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.     

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.     

H2O2、Fenton试剂与活性炭联用对CODCr去除效果的对比试验研究

为了开发高效低成本、达到回用水质标准的污水处理工艺,本试验采用H2O2、Fenton试剂与活性炭联用对CODCr进行去除的对比试验研究。结果表明：在室温下200 mL水样,当pH为3,震荡强度为150 rpm时,Fenton试剂-活性炭联用与H2O2-活性炭相比,活性炭用量少200 mg,时间缩短10 h,CODCr去除率高17.6%。试验揭示了Fenton试剂-活性炭联用的反应机理：Fe2＋与活性炭共同催化分解H2O2生成大量.OH,能快速氧化降解有机物,使CODCr浓度迅速降低。从工程应用角度和技术经济方面考虑,Fenton试剂-活性炭联用的pH值在5～7适宜;且处理成本更低。Fenton试剂-活性炭联用是处理二级出水CODCr高效、低耗的方法,值得进一步研究和推广应用。     

Applications of advanced oxidation processes: present and future.

The use of advanced oxidation processes (AOPs) to remove pollutants in various water treatment applications has been the subject of study for around 30 years. Most of the available processes (Fenton reagent, O3 under basic conditions, O3/H2O2, O3/UV, O3/solid catalyst, H2O2/M(n+), H2O2/UV, photo-assisted Fenton, H2O2/solid catalyst, H2O2/NaClO, TiO2/UV etc.) have been investigated in depth and a considerable body of knowledge has been built up about the reactivity of many pollutants. Various industrial applications have been developed, including ones for ground remediation (TCE, PCE), the removal of pesticides from drinking water, the removal of formaldehyde and phenol from industrial waste water and a reduction in COD from industrial waste water. The development of such AOP applications has been stimulated by increasingly stringent regulations, the pollution of water resources through agricultural and industrial activities and the requirement that industry meet effluent discharge standards. Nevertheless, it is difficult to obtain an accurate picture of the use of AOPs and its exact position in the range of water treatment processes has not been determined to date. The purpose of this overview is to discuss those processes and provide an indication of future trends.     

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.     

Study on the treatment of Acid Red 4 wastewaters by a laminar-falling-film-slurry-type VUV photolytic process.

The purpose of this study is to develop the design equation of a laminar-falling-film-slurry-type (LFFS) photoreactor for the treatment of organic wastewaters (Acid Red 4) by 185 nm vacuum ultra-violet (VUV) related processes. The LFFS photoreactor is one of the most efficient reactor configurations for conducting heterogeneous photocatalytic reactions, particularly for wastewater treatment. The decomposition of Acid Red 4 dye wastewaters by VUV-based photo-oxidation process was studied under various UV light intensities, dosages of H2O2 and TiO2. By the treatment of the LFFS-VUV only process, it was found that the decomposition rates of the dye in aqueous solutions increased with the increasing of VUV light intensity, dosage of TiO2, dosage of H2O2. The apparent potential of OH. generation from the photolysis of used oxidants (i.e. OH. sources, H2O, H2O2, TiO2) to decompose the targeted dye wastewater was investigated and compared.     

非活性红色链霉菌吸附废水中Pb2+机理分析

采用吸附等温方程、扫描电镜以及红外光谱仪等测试分析方法对红色链霉菌废菌体吸附废水中Pb2+的机理进行分析和探讨。结果表明,强碱的处理可以明显提高废菌体的吸附性能;红色链霉菌细胞壁上的—COO—、C—H和O—H可能是吸附铅离子的主要基团;红色链霉菌吸附Pb2+的过程可能是一个以表面络合反应为主的物理化学吸附过程。     

H_2O_2与沸石联用处理污水厂二级出水的研究

为探寻污水厂二级出水深度处理方法,以阜新市某污水处理公司二级出水为研究对象,进行H2O2与沸石联用去除水中COD、氨氮的研究。结果表明：在二氧化锰的催化作用下,pH值为7时,H2O2和沸石的投加量分别为1.5mL和2g,二级出水的COD从138.24mg/L降到52.76mg/L,去除率达到75.36%,NH3-N从20mg/L降到5mg/L,去除率为74.59%,出水有机物和氨氮含量达到国家相关出水标准。     

Biofilm control in water by advanced oxidation process (AOP) pre-treatment: effect of natural organic matter (NOM)

The main goal of this study was to examine the influence of natural organic matter (NOM) on the efficiency of H?O?/UV advanced oxidation process (AOP) as a preventive treatment for biofilm control. Pseudomonas aeruginosa PAO1 biofilm-forming bacteria were suspended in water and exposed to various AOP conditions with different NOM concentrations, and compared to natural waters. H?O?/UV prevented biofilm formation: (a) up to 24 h post treatment - when residual H?O? was neutralized; (b) completely (days) - when residual H?O? was maintained. At high NOM concentrations (i.e. 25 mg/L NOM or 12.5 mg/L DOC) an additive biofilm control effect was observed for the combined H?O?/UV system compared to UV irradiation alone, after short biofilm incubation times (<24 h). This effect was H?O? concentration dependent and can be explained by the high organic content of these water samples, whereby an increase in NOM could enhance (?)OH production and promote the formation of additional reactive oxygen species. In addition, maintaining an appropriate ratio of bacterial surviving conc.: residual H?O? conc. post-treatment could prevent bacterial regrowth and biofilm formation.     

有压管道过渡过程的数值计算

基于理想气体状态方程和全新的圆形管道水体积与水深关系数学模型,按照小流量充水原则,结合空气阀的进、排气性质和泄水管的排水特性,对一定的充水流量和不同的放水流量下有压管道充、放水过程中气体压力的变化进行了数值计算。结果表明:在小流量充水的情况下,管内的气体压力不是很高,放水流量越大,对应管段的气体压力越小、管道越危险。     

Phosphorus removal from synthetic and municipal wastewater using spent alum sludge.

In the present study, phosphorus removal was studied using as coagulant spent alum sludge from a water treatment plant of EYDAP (Athens Water Supply and Sewerage Company) and compared to alum (Al2(SO4)3.18H2O), iron chloride (FeCl3.7H2O), iron sulfate (Fe2(S04).10H2O) and calcium hydroxide (Ca(OH)2) at a constant pH (equal to 6).The comparison was based on their efficiency to remove phosphorus in synthetic wastewater consisting of 10 mg/L P as potassium dihydrogen phosphate and 50 mg/L N as ammonium chloride, The experiments were carried out using a jar-test apparatus and the measurements were performed according to the Standard Methods for the Examination of Water and Wastewater. Pure alum, iron chloride and iron sulfate were much more efficient in phosphorus removal than the spent alum sludge but in the case of calcium hydroxide, phosphorus removal was very low in pH = 6. Specifically, orthophosphate were totally removed by alum using 15 mg/L as Al, by alum sludge using 75 mg/L as Al and by FeCl3.7H2O or Fe2(SO4).10H2O using 30 mg/L of Fe while in the case of calcium hydroxide P removal was actually zero. pH measurements showed that the uptake of phosphates is associated to the release of OH ions in the solution and that the end of P uptake is accompanied by the stabilization of pH. Finally this spent alum sludge was tested on municipal wastewater and proved to be effective as apart from phosphorus it was shown to remove turbidity and COD.     

Comparison between ozone and ferrate in oxidising geosmin and 2-MIB in water.

Among the chemicals causing taste and odour (T&O) in drinking water, the most commonly identified and problematic ones are geosmin and 2-MIB (2-methylisoborneol). Since the reported odour thresholds of geosmin and 2-MIB are as low as 4 and 8.5 ng/L, respectively, they are not readily removed by conventional water treatment processes. In this study, ozone (O3) and ferrate (Fe(VI)) were applied to oxidise geosmin and 2-MIB. Their performances were compared in terms of removal efficiency of geosmin and 2-MIB. In the case of O3, removal efficiency of geosmin and 2-MIB ozonation at different initial O3 doses, H2O2/O3 ratios and water temperatures were evaluated. The oxidation rates of geosmin and 2-MIB by Fe(VI) were measured within pH 6-8. The effect of H2O2 addition was also evaluated. In summary, O3, especially with H2O2, could almost completely oxidise geosmin and 2-MIB, while Fe(VI) could not oxidise them more than 25% at any pH that was considered in this study. This was attributed to the structure of the organics and high reaction selectivity of Fe(VI). Further study should be conducted to find the reason of inhibition of oxidation by Fe(VI).     

A kinetic study of enhancing effect by phenolic compounds on the hydroxyl radical generation during ozonation.

Ozone decomposition in aqueous solution proceeds through a radical type chain mechanism. These reactions involve the very reactive and catalytic intermediates O2- radical, OH radical, HO2 radical, OH-, H2O2, etc. OH radical is proposed as an important factor in the ozonation of water among them. In the present study, the enhancing effects of several phenolic compounds; phenol, 2-, 3-, 4-monochloro, 2,4-dichloro, 2,4,6-trichlorophenol on OH radical generation were mathematically evaluated using the electron spin resonance (ESR)/spin-trapping technique. OH radical was trapped with a 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a stable adduct, DMPO-OH. The initial velocities of DMPO-OH generation in ozonated water containing phenolic compounds were quantitatively measured using a combined system of ESR spectroscopy with stopped-flow apparatus, which was controlled by homemade software. The initial velocities of DMPO-OH generation increased as a function of the ozone concentration. The relation among ozone concentration, amount of phenolic compounds and the initial velocity (v0) of DMPO-OH generation was mathematically analyzed and the following equation was obtained, v0 (10(-6) M/s) = (A' x [PhOHs (10(-9) M)] + 0.0005) exp (60 x [ozone (10(-9) M)]). The equation fitted very well with the experimental results, and the correlation coefficient was larger than 0.98.     

Comparison of different advanced oxidation process to reduce toxicity and mineralisation of tannery wastewater.

Many organic compounds contained in wastewater are resistant to conventional chemical and/or biological treatment. Because of this reason different degradation techniques are studied as an alternative to biological and classical physico-chemical processes. Advanced Oxidation Processes (AOPs) probably have developed to become the best options in the near future. AOP while making use of different reaction systems, are all characterised by the same chemical feature: production of OH radicals (*OH). The versatility of AOPs is also enhanced by the fact that they offer different possibilities for OH radical production, thus allowing them to conform to specific treatment requirements. The main problem with AOPs is their high cost. The application of solar technologies to these processes could help to diminish that problem by reducing the energy consumption required for generating UV radiation. In this work, different AOPs (O3, TiO2/UV, Fenton and H2O2/UV) were examined to treat tannery wastewater or as a pre-treatment step for improving the biodegradation of tannery wastewater, at different pH and dosage of the chemicals. Under certain circumstances retardation in biodegradation and/or an increase in toxicity may be observed within these treatment steps. Two different bioassays (Daphnia magna and Vibrio fischeri) have been used for testing the progress of toxicity during the treatment. In parallel other objectives were to analyse and identify organic compounds present in the untreated wastewater and arising degradation products in AOP treated wastewater samples. For this purpose substance specific techniques, e.g., gas chromatography-mass spectrometry (GC-MS) in positive electron impact (El(+)) mode and atmospheric pressure ionisation (API) in combination with flow injection analysis (FIA) or liquid chromatography-mass and tandem mass spectrometry (LC-MS or LC-MS-MS) were performed.     

Impact of summer droughts on water quality of the Rhine River - a preview of climate change?

It is generally recognized that climate change will affect the discharge regime of the Rhine River. Especially the anticipated increase in extreme river discharges (floods and droughts) poses serious problems to water management, both with regard to water quantity and water quality. Water quality effects of climate change are not sufficiently recognized, however. The purpose of this study is to investigate the impact of droughts on the water quality of the River Rhine. Time series of river flow and water quality were analyzed for station Lobith, located at the Dutch-German border. Over the past three decades, three major droughts were identified, occurring in the years 1976, 1991, and 2003. The water quality during these dry years was compared with the water quality in reference years, characterized by average hydrological conditions and similar chemical pollution. Four groups of water quality parameters were investigated: 1, general variables (water temperature, dissolved oxygen, chlorophyll-a); 2, major ions (chloride, sodium, sulfate, fluoride, bromide); 3, nutrients; and 4, heavy metals. It was found that water quality is negatively influenced by (summer) droughts, with respect to water temperature, eutrophication, major ions and heavy metals. Effects on nutrient concentrations were small for ammonium and could not be demonstrated for nitrate, nitrite and phosphate. The decline in water quality during summer droughts is both related to the high water temperatures and to low river discharges (limited dilution of the chemical load from point sources). Moreover, the impact of the 1976 drought on water quality was far more important than that of the 2003 drought, indicating that the impact of droughts on water quality will be greater when the water quality is already poor.