Treatment of taste and odor material by oxidation and adsorption.

Massive blooms of blue-green algae in reservoirs produce the musty-earthy taste and odor, which are caused by compounds such as 2-MIB and geosmin. 2-MIB and geosmin are rarely removed by conventional water treatment. Their presence in the drinking water, even at low levels (ng/L), can be detected and it creates consumer complaints. So those concentrations have to be controlled as low as possible in the drinking water. The removals by oxidation (O3, Cl2, ClO2) and adsorption (PAC, filter/adsorber) were studied at laboratory and pilot plant (50 m3/d) to select suitable 2-MIB and geosmin treatment processes. The following conclusions were derived from the study. Both of the threshold odor levels for 2-MIB and geosmin appeared to be 30 ng/L as a consequence of a lab test. For any given PAC dosage in a jar-test, removal efficiencies of 2-MIB and geosmin were increased in proportion to PAC dosage and were independent of their initial concentration in raw water for the tested PAC dosages. In comparison of geosmin with 2-MIB, the adsorption efficiency of geosmin by PAC was superior to that of 2-MIB. The required PAC dosages to control below the threshold odor level were 30 mg/L for geosmin and 50 mg/L for 2-MIB at 100 ng/L of initial concentration. Removal efficiencies of odor materials by Cl2, ClO2, and O3 were very weak under the limited dosage (1.5 mg/L), however increased ozone dosage (3.8 mg O3/L) showed high removal efficiency (84.8% for 2-MIB) at contact time 6.4 minutes. According to the initial concentrations of 2-MIB and geosmin, their removal efficiencies by filter/adsorber differed from 25.7% to 88.4%. For all those, however, remaining concentrations of target materials in finished waters were maintained below 30 ng/L. The longer run-time given for the filter/adsorber, the higher the effluent concentration generated. So it is necessary that the run-time of the filter/adsorber be decreased, when 2-MIB or geosmin occurs in raw water.     

Fenton高级氧化技术去除水中有机污染物2-MIB的影响因素研究

针对目前比较关注的致嗅物质污染问题,选用Fenton高级氧化技术研究了其对水中致嗅物质2-甲基异莰醇（2-MIB）的去除,探讨了Fenton反应对水中致嗅物质的去除效能及H2O2/Fenton摩尔比、Fe2＋浓度、反应时间和溶液pH值各因素对氧化反应的影响。提出了Fenton氧化反应去除2-MIB的最佳反应条件。实验结果表明：Fenton高级氧化能有效去除水中的2-MIB。在H2O2/Fenton摩尔比为3.0、Fe2＋浓度10 mg/L、反应时间10 min和溶液pH值为3.0时,去除效率达到97.9%。Fenton氧化反应的操作条件（浓度、pH值等）比较容易实现,因此Fenton氧化技术在实际污染处理中有很大的应用前景。     

Advanced treatment for taste and odour control in drinking water: case study of a pilot scale plant in Seoul, Korea.

Taste and odour problems of tap water in Seoul are attributed to 2-methylisoborneol (2-MIB) and trans-1,10-dimethyl-trans-9-decalol (geosmin), which are the result of metabolism of algae and chlorine for disinfection. This study was carried out to measure 2-MIB and geosmin in the raw water from the Han River, to investigate removal efficiency of GAC and BAC integrated with post-ozonation, and to minimise and quantify the required chlorine concentration as a final disinfectant through the candidate process.     

Use of iron(VI) and iron(V) in water and wastewater treatment.

Fe(VI) (Fe(VI)O4(2-)) and Fe(V) (Fe(V)O4(3-)) have high oxidizing power, selectivity, and upon decomposition produce a non-toxic by-product, Fe(III), which makes them potential oxidants in water and wastewater treatment. Rates of oxidation increase with a decrease in pH and are related to protonation of Fe(VI)O4(2-) and Fe(V)O4(3-). Oxidation of sulfur- and nitrogen-containing pollutants by Fe(VI) can be accomplished in seconds to minutes with formation of non-hazardous products. Fe(VI) can easily oxidize the amino acid components of microcystins and is a suitable disinfectant for detoxifying toxins in water. The oxidation of pollutants and amino acids with Fe(V) is 3-5 orders of magnitude faster than with Fe(VI). The use of ionizing radiation and photocatalytic techniques in the presence of Fe(VI) results in Fe(V) formation and may have synergistic effects on the oxidation of pollutants and removal of toxins in water and wastewater. This paper summarizes the results of multi-functional properties of Fe(VI) and Fe(V) to treat water and wastewater.     

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.     

Ability of humans to smell geosmin, 2-MIB and nonadienal in indoor air when using contaminated drinking water.

The most common compounds responsible for off flavours are geosmin, 2-MIB, and nonadienal which are poorly removed by conventional water treatment operations and hence result in customer complaints. Because these odourants are moderately volatile and have very low odour threshold values, it is necessary to determine their concentrations in air when water is used indoors. If the detectable aqueous concentrations for these odourants are known, the utilities may take action to treat their water at times when the concentration of the raw water exceeds the threshold concentration. To predict the concentration in the shower stall and bathroom air after showering, recently published Henry's law constants for the selected odourants and a model developed to determine the volatilization of the odourous compounds by applying two-resistance theory were used. Then the results were compared with the odour threshold concentration data to determine under which conditions the odourants become detectable. For parameters representing a typical bathroom and shower stall setting, the results showed that the odourants become detectable when the aqueous concentration of geosmin and nonadienal exceed 10 ng/L at 42 degrees C. As the aqueous concentration increases, geosmin and nonadienal become detectable at lower temperatures, however 2-MIB is only detectable above 20 ng/L and at 42 degrees C.     

Removal of geosmin and 2-methylisoborneol by biological filtration.

The quality of drinking water is sometimes diminished by the presence of certain compounds that can impart particular tastes or odours. One of the most common and problematic types of taste and odour is the earthy/musty odour produced by geosmin (trans-1, 10-dimethyl-trans-9-decalol) and MIB (2-methylisoborneol). Taste and odour treatment processes including powdered activated carbon, and oxidation using chlorine, chloramines, potassium permanganate, and sometimes even ozone are largely ineffective for reducing these compounds to below their odour threshold concentration levels. Ozonation followed by biological filtration, however, has the potential to provide effective treatment. Ozone provides partial removal of geosmin and MIB but also creates other compounds more amenable to biodegradation and potentially undesirable biological instability. Subsequent biofiltration can remove residual geosmin and MIB in addition to removing these other biodegradable compounds. Bench scale experiments were conducted using two parallel filter columns containing fresh and exhausted granular activated carbon (GAC) media and sand. Source water consisted of dechlorinated tap water to which geosmin and MIB were added, as well as, a cocktail of easily biodegradable organic matter (i.e. typical ozonation by-products) in order to simulate water that had been subjected to ozonation prior to filtration. Using fresh GAC, total removals of geosmin ranged from 76 to 100% and total MIB removals ranged from 47% to 100%. The exhausted GAC initially removed less geosmin and MIB but removals increased over time. Overall the results of these experiments are encouraging for the use of biofiltration following ozonation as a means of geosmin and MIB removal. These results provide important information with respect to the role biofilters play during their startup phase in the reduction of these particular compounds. In addition, the results demonstrate the potential biofilters have in responding to transient geosmin and MIB episodes.     

Efficient taste and odour removal by water treatment plants around the Han River water supply system.

Seven major water treatment plants in Seoul Metropolitan Area, which are under Korea Water Resources Corporation (KOWACO)'s management, take water from the Paldang Reservoir in the Han River System for drinking water supply. There are taste and odour (T&O) problems in the finished water because the conventional treatment processes do not efficiently remove the T&O compounds. This study evaluated T&O removal by ozonation, granular activated carbon (GAC) treatment, powder activated carbon (PAC) and an advanced oxidation process in a pilot-scale treatment plant and bench-scale laboratory experiments. During T&O episodes, PAC alone was not adequate, but as a pretreatment together with GAC it could be a useful option. The optimal range of ozone dose was 1 to 2 mg/L at a contact time of 10 min. However, with ozone alone it was difficult to meet the T&O target of 3 TON and 15 ng/L of MIB or geosmin. The GAC adsorption capacity for DOC in the three GAC systems (F/A, GAC and O3 + GAC) at an EBCT of 14 min is mostly exhausted after 9 months. However, substantial TON removal continued for more than 2 years (>90,000 bed volumes). GAC was found to be effective for T&O control and the main removal mechanisms were adsorption capacity and biodegradation.     

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。     

The effect of oxidants on 2-MIB concentration with the presence of cyanobacteria.

In this study, the effect of three oxidants, sodium hypochlorite, potassium permanganate, and ozone, were tested for the removal of 2-MIB with presence of cyanobacteria. Algae in water samples from the source water of Feng-Shen waterworks (FSW), Taiwan were cultivated at 30 degrees C with continuous light at an intensity between 2,500 and 3,400 lux. During the cultivating process, water samples were analyzed for nutrients, light absorbance at 665 nm (A665), and 2-MIB concentration. The 2-MIB concentrations within the incubated samples increased to as high as 1,000 ng/L to 2,000 ng/L, although no extra nutrients were added to the raw water. After 2 to 3 days incubation, the intracellular 2-MIB concentration was as high as 70% of the total 2-MIB in the samples. The algae that developed were mainly cyanobateria, and more than 90% belonged to the Genus Oscillatorias. An almost 100% removal of both 2-MIB and geosmin in the raw water was observed after ozonation for 10 minutes at a dosing rate of 0.91 mg/l-min. Chlorine and permanganate were much less effective, both removing only about 11% of the 2-MIB within 60 minutes at oxidant concentration of 10 mg/l. Oxidation of the cultivated samples showed that chlorine and permanganate may damage algae cells causing them to release intracellular 2-MIB. During the 60 minutes of reaction time, the total 2-MIB concentrations (intracellular plus dissolved) varied by no more than 10%, however, the ratios between dissolved and total 2-MIB concentrations increased. Two effects of ozonation on the 2-MIB concentration in the cultivated samples were observed when the algae were young, namely 2-MIB release from damaged cells and 2-MIB oxidization. The rates of 2-MIB release and 2-MIB destruction were similar. However, old algae cells were more easily damaged. As a result, intracellular 2-MIB was released faster, and the soluble 2-MIB was destroyed more quickly by ozonation.     

Effective degradation of para-chloronitrobenzene through a sequential treatment using zero-valent iron reduction and Fenton oxidation

In this study, zero-valent iron (ZVI) was used to pretreat para-chloronitrobenzene (p-CNB), and the major product was para-chloroaniline (p-CAN). By adding H(2)O(2) directly, further p-CAN degradation can be attributed to Fenton oxidation because ferrous ions (Fe(2+)) released during the ZVI corrosion could be used as an activator for H(2)O(2) decomposition. In the reduction process, the reduction efficiency of p-CNB as well as Fe(2+) concentration increased with increasing iron dosage and decreasing solution pH. Under the optimal conditions, 25 mg L(-1) of p-CNB could be transformed in 3 h when initial solution pH was 3.0 and ZVI dosage was 2.0 g L(-1). A sufficient amount of Fe(2+) (50.4 mg L(-1)) was obtained after the above reaction to activate H(2)O(2). In the Fenton process, the oxidization of p-CAN was also more effective in acidic conditions and it increased with increasing H(2)O(2) concentration. The control experiments showed that the sequential treatment was more effective than Fenton oxidation alone in treating p-CNB wastewater since the removal rate of total organic carbon (TOC) was improved by about 34%. It suggested that the amino function group is more susceptible to oxidative radical attack than the nitro function group. Therefore, sequential treatment using zero-valent iron reduction followed by Fenton oxidation is a promising method for p-CNB degradation.     

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.     

ph and Mg/Ca control for biological treatment of an offensive flavour (2-MIB)

From a series of experimental observations, it was found that removal rates of the offensive flavor 2-methylisoborneol(2-MIB) and ammonia by a biological treatment for water supply were rather unstable and that the removal rates of them often became reverse such as low removal in 2-MIB and high removal of ammonia. One reason for the reverse phenomenon was found that the affinities of sludge around bacteria with 2-MIB and ammonia often became reversed. The affinities of sludge with 2-MIB and ammonia were found to be changeable depending upon pH along with magnesium (Mg) and calcium (Ca) concentrations in sludge. From these findings, control of pH and magnesium calcium ratio (Mg/Ca) of raw water was recommended for simultaneous and stable removal of 2-MIB and ammonia. From plant scale experiments equipped with automatic pH controller, the effects of pH and Mg/Ca control for biological treatment of 2-MIB and ammonia were observed in a biological activated filtration. Here, a biological activated carbon filtration means a longer filtration than 40 to 50 days from the beginning. The obtained results were almost as expected, showing high removal rates of both 2-MIB and ammonia.     

Mechanistic evidence and efficiency of the Cr(VI) reduction in water by different sources of zerovalent irons.

The objective of this research was to assess the mechanism and effectiveness of the zerovalent iron (ZVI) to remediate the Cr(VI) contaminated water. The mechanism of Cr(VI) reduction by ZVI was evaluated by characterising surface properties and chemical compositions of Fe and Cr products using SEM-EDS, XRD and XPS analyses. The effectiveness of ZVI in Cr(VI) reduction was assessed by the luminescent bacteria (Photobacterium Phosphoreum). The Cr(VI) was reduced to Cr(III), when the reactive Fe(o) was oxidised to Fe(II, III), showing the presence of Fe2O3, (Fe-Cr)2O3 and FeOOH. The SEM-EDS analysis showed that ZVI with a higher reducing capacity was more subject to changes of surface and morphological properties due to ionisation of ZVI. The Cr and Fe in precipitates subsisted exclusively in the Cr(III) or Fe(III) states with the respective forms of Cr(OH)3 or Cr2O3 and FeOOH or Fe2O3. Electrons produced from ZVI oxidation reduced Cr(VI) to Cr(III), thus resultantly Cr(III) precipitated or co-precipitated with Fe(III) to form Fe(III)-Cr(III) hydroxide or Fe(III)-Cr(III) oxyhydroxide. Toxicity of water reacted with ZVI was significantly lower than that of the untreated water.     

Catalytic action of goethite in the oxidation of 2-chlorophenols with hydrogen peroxide.

The use of goethite and hydrogen peroxide was recently found to effectively oxidise organic compounds. This research was to investigate the effect of adsorption, pH, Fe2+ and Fe3+ on 2-CP oxidation. Results indicated that 2-CP can be decomposed with hydrogen peroxide catalysed by goethite and the oxidation rate increased with decreasing goethite particle size. The optimum oxidation rate was observed at the pH below 3.0. Addition of Fe2+ and Fe3+ can enhance the catalytic oxidation rate of 2-CP very efficiently. The main mechanism of goethite catalysing hydrogen peroxide to oxidise 2-CP may be due to the catalysis of ferrous ions and goethite surface.     

Degradation of endocrine disrupting chemicals in aqueous solution by interaction of photocatalytic oxidation and ferrate (VI) oxidation.

In this study, the degradation of bisphenol A in aqueous suspension by interaction of photocatalytic oxidation and ferrate(VI) oxidation was investigated under different conditions. The results indicate that the formation of Fe(V) and Fe(IV) is in the photocatalytic reduction of Fe(VI) by electron (ecb-) on the surface of TiO2. The oxidation efficiency of the photocatalytic oxidation in the presence of Fe(VI) was much greater than that without. In addition, the decomposition of Fe(VI) under different conditions was also investigated. The results indicate that the Fe(VI) reduction was accelerated by photocatalytic reaction and the adsorption capacity of Fe(VI) on TiO2 surface decreased as pH increased. The characteristics of solid potassium ferrate prepared were investigated by X-ray diffraction. It was found that the potassium ferrate solid has a tetrahedral structure with a space group of D2h (Pnma) and a = 7.705 A, b = 5.863 A, and c = 10.36 A.     

AOPs with ozone and UV radiation in drinking water: contaminants removal and effects on disinfection byproducts formation.

In this study, the advanced oxidation with ozone and UV radiation (with two low pressure UV lamps, at 254 and 185 nm wavelength) were experimented on a surface water in order to study the removal of two odorous compounds (geosmin and 2-methylisoborneol) and a pesticide (metolachlor), the influence on organic compounds (UV absorbance and THM precursors) and bromate formation. Different batch tests were performed with ozone concentration up to 10 mg/L, UV dose up to 14,000 J/m2 and a maximum contact time of 10 minutes. The main results show that metolachlor can be efficiently removed with ozone alone while for geosmin and MIB a complete removal can be obtained with the advanced oxidation of ozone (with concentration of 1.5-3 mg/L and contact time of 2-3 minutes) with UV radiation (with doses of 5,000-6,000 J/m2). As concerns the influence on the organic precursors, all the experimented processes show a medium removal of about 20-40% for UV absorbance and 15-30% for THMFP (trihalomethanes formation potential). As concerns bromate formation, the advanced oxidation of ozone/UV 254 nm shows a bromate formation that is about 40% lower with respect to conventional oxidation with ozone.     

二氧化氯催化氧化降解铬黑T试验研究

在常温常压下,对Fe2O3/γ—A12O3+H2O2和ClO2+TiO2两种催化氧化体系处理铬黑T废水的效果进行了分析。试验结果表明,处理甲基橙废水效果较好的Fe2O3/γ—Al2O3+H2O2组合对铬黑T的降解效果非常有限,而ClO2+TiO2组合的处理效果较好:以500 mg/L的铬黑T溶液为模拟废水,当pH为4,C102投加量为200 mg/L,TiO2投加量为500 mg/L,反应时间为90 min时,脱色率达89.96%,CODCr的去除率可达45.36%。     

Fe-O/CeO_2催化剂的制备、表征及其对垃圾渗滤液微波催化氧化活性的研究

以浸渍法制备用于常温常压微波催化氧化工艺的负载型Fe-O/CeO_2催化剂并通过XRD和SEM手段进行表征;利用优化制备后的催化剂进行微波催化氧化垃圾渗滤液的研究.结果表明:Fe-O/CeO_2催化剂中活性组分Fe以α-Fe_2O_3和CeFe_2的形式存在.在渗滤液初始COD_(Cr)5 736 mg/L、氨氮1 840 mg/L、色度500倍和pH 8.69的条件下,在Fe-O/CeO_2投加量10 g/L、H_2O_2(30%)投加量22.5 mL/L、微波功率800 W、微波辐射时间10 min和水样初始浓度C_(水样)/C_(原水)为100%的最佳运行条件下,微波催化氧化工艺对COD_(Cr)、氨氮和色度的去除率分别为73%、78%和85%;在反应的第4～8 min和第2～8 min,COD_(Cr)和氨氮去除率分别与反应时间呈近似直线的关系.     

Fenton试剂对铁锰矿井废水处理的实验研究

使用Fenton试剂对铁锰矿井水进行处理试验,论述了反应温度、H2O2的投加量、pH、反应时间对Fenton试剂处理矿井水的影响,讨论了Fenton试剂处理酸性矿井废水的机理。结果表明:芬顿试剂对铁锰矿井水中锰的去除效率很高,矿井水中的Fe2+能与H2O2形成Fenton试剂后产生的具有强氧化性的.OH能有效处理矿井水中的Mn2+。对于原水Mn2+的初始浓度为2 mg/L,Fe2+的初始浓度为250 mg/L,pH为5,当控制反应温度为25℃,H2O2的投加量为8 mmol/L,调节pH值为4.5,反应时间为10 m in,Mn2+去除效率可以达到78.1%以上。