Removal efficiency and homologue patterns of dioxins in drinking water treatment

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) analyses in raw and treated water throughout Japan were implemented to identify the concentration and homologue patterns of dioxins before and after the water treatment process. In 40 surface water and 5 ground water treatment plants, the removal efficiency of dioxins and the influence of extent chlorination on dioxins increase in drinking water were also studied. Raw water and treated water were sampled twice, summer and winter. The mean concentration in raw water and treated water of dioxins was 56.45 pg/L (0.15 pg WHO-TEQ/L) and 4.24 pg/L (0.019 pg WHO-TEQ/L), respectively. Location of water treatment plants not only significantly influenced the concentration level of dioxins but also resulted in different homologue patterns of dioxins. Levels of dioxins in ground water were much less than that of surface water in both raw and treated water. This study shows most dioxin congeners are well removed (87% removal efficiency) by water treatment. However, in some water treatment plants, the level of TeCDFs (pg WHO-TEQ/L) increased as a result of chlorination.     

人工湿地废水处理中氮、磷去除机理研究

人工湿地是由基质、植物、微生物和水体组成污水处理生态系统,在脱氮除磷方面有着很好的效果。文中比较全面的总结了近几年来在人工湿地氮磷去除机理研究方面所取得的一些成果,着重讨论了基质、植物、微生物、水力负荷、温度、溶解氧等因素对人工湿地氮磷去除效果的影响。并提出了为了提高人工湿地脱氮除磷效果、扩大人工湿地应用范围,今后需要开展3方面工作：（1）进一步的深入研究氮磷去除机理;（2）考察更多环境因素对氮磷去除的影响;（3）研发、改进工艺。     

High yield combustion synthesis of nanomagnesia and its application for fluoride removal

We describe a novel combustion synthesis for the preparation of Nanomagnesia (NM) and its application in water purification. The synthesis is based on the self-propagated combustion of the magnesium nitrate trapped in cellulose fibers. Various characterization studies confirmed that NM formed is crystalline with high phase purity, and the particle size varied in the range of 3-7 nm. The fluoride scavenging potential of this material was tested as a function of pH, contact time and adsorbent dose. The result showed that fluoride adsorption by NM is highly favorable and the capacity does not vary in the pH range usually encountered in groundwater. The effects of various co-existing ions usually found in drinking water, on fluoride removal were also investigated. Phosphate was the greatest competitor for fluoride followed by bicarbonate. The presence of other ions studied did not affect the fluoride adsorption capacity of NM significantly. The adsorption kinetics followed pseudo-second-order equation and the equilibrium data are well predicted by Frendlich equation. Our experimental evidence shows that fluoride removal happened through isomorphic substitution of fluoride in brucite. A batch household defluoridation unit was developed using precipitation-sedimentation-filtration techniques, addressing the problems of high fluoride concentration as well as the problem of alkaline pH of the magnesia treated water. The method of synthesis reported here is advantageous from the perspectives of small size of the nanoparticle, cost-effective recovery of the material and improvement in the fluoride adsorption capacity.     

The application of membrane filtration for the removal of ammonium ions from potable water

It is well recognized that soluble ammonia and nitrite in drinking water has chronic effects on humans. Ammonia has potential environmental health hazards, particularly to young children. European Union Standards limit the concentration of ammonia to 0.5 mg/l in drinking water. In Eskisehir (Turkey) drinking and tap water are supplied from a water treatment plant, consisting mainly of screening, sedimentation, filtration and sterilization units and having a capacity of 80.000 m3/d. Depend on the industrial and climatic effects the observed high ammonium concentration in treated water causes undesirable effects of water quality. Therefore, people in Eskisehir do not want to use tap water for drinking. The aim of the study was to evaluate the performance of membrane processes, i.e. Nanofiltration and reverse osmosis to the removal of ammonium and Ca ions from plant effluent and recommend one of them for a subsequent pilot plant application.     

Efficient arsenic(V) removal from water by ligand exchange fibrous adsorbent

This study is an efficient arsenic(V) removal from contaminated waters used as drinking water in adsorption process by zirconium(IV) loaded ligand exchange fibrous adsorbent. The bifunctional fibers contained both phosphonate and sulfonate groups. The bifunctional fiber was synthesised by graft polymerization of chloromethylstyrene onto polyethylene coated polypropylene fiber by means of electron irradiation graft polymerization technique and then desired phosphonate and sulfonate groups were introduced by Arbusov reaction followed by phosphorylation and sulfonation. Arsenic(V) adsorption was clarified in column methods with continuous flow operation in order to assess the arsenic(V) removal capacity in various conditions. The adsorption efficiency was evaluated in several parameters such as competing ions (chloride and sulfate), feed solution acidity, feed flow rate, feed concentration and kinetic performances at high feed flow rate of trace concentration arsenic(V). Arsenic(V) adsorption was not greatly changed when feed solutions pH at 3.0-7.0 and high breakthrough capacity was observed in strong acidic area below pH 2.2. Increasing the flow rate brings a decrease both breakthrough capacity and total adsorption. Trace level of arsenic(V) (0.015 mM) in presence of competing ions was also removed at high flow rate (750 h⁻¹) with high removal efficiency. Therefore, the adsorbent is highly selective to arsenic(V) even in the presence of high concentration competing ions. The adsorbent is reversible and reusable in many cycles without any deterioration in its original performances. Therefore, Zr(IV) loaded ligand exchange adsorbent is to be an effective means to treat arsenic(V) contaminated water efficiently and able to safeguard the human health.     

Evaluation of a novel hybrid inorganic/organic polymer type material in the arsenic removal process from drinking water

The objective of this paper is the evaluation of a hybrid inorganic/organic polymer type material based on hydrated ferric oxide (HFO), in the adsorption process of arsenic oxyanions from contaminated waters used as drinking water. The study includes rapid small-scale column tests conducted in continuous flow operation in order to assess the arsenic removal capacity in various conditions. Thus it was evaluated the influence of some competing ions like silicate and phosphate on As(V) adsorption and the influence of feed water pH in the removal process of As(V) and As(III) species. Based on the As/pH variation in time at different feed water pH (5, 7 and 9), a possible sorption mechanism that fits the experimental data was suggested. The regeneration and re-use of the hybrid adsorbent was studied in the presence and in the absence of the contaminant ions. The novel hybrid material is very selective towards arsenic oxyanions even though the presence of silica and phosphate reduces the adsorption capacity.     

Effectiveness of household reverse-osmosis systems in a Western U.S. region with high arsenic in groundwater

It is well known to the public in Lahontan Valley in rural Nevada, USA, that local aquifers produce water with varied, but sometimes very high concentrations of arsenic (>4 ppm). As a result, many residents of the area have installed household reverse-osmosis (RO) systems to produce drinking water. We examined performance of RO systems and factors associated with arsenic removal efficiency in 59 households in Lahontan Valley. The sampling results indicated that RO systems removed an average of 80.2% of arsenic from well water. In 18 of the 59 households, arsenic concentrations exceeded 10 ppb in treated water, with a maximum in treated water of 180 ppb. In 3 of the 59 households, RO treatment had little effect on specific conductance, indicating that the RO system was not working properly. Two main factors lead to arsenic levels in treated water exceeding drinking-water standards in the study area. First, arsenic concentrations were high enough in some Lahontan Valley wells that arsenic levels exceeded 10 ppb even though RO treatment removed more than 95% of the arsenic. Second, trivalent As(+3) was the dominant arsenic species in approximately 15% of the wells, which significantly reduced treatment efficiency. Measurements of specific conductance indicated that efficiency in reducing arsenic levels did not always correlate with reductions in total dissolved solids. As a consequence, improvements in taste of the water or simple measurements of specific conductance made by technicians to test RO systems can mislead the public into assuming the water meets safety standards. Actual measurements of treated water are necessary to assure that household RO systems are reducing arsenic concentrations to safe levels, particularly in areas where groundwater has high arsenic concentrations or where As(+3) is the dominant species.     

Removal of quinol from aqueous solution by adsorption onto Fe(III)/Cr(III) hydroxide and application to real effluent treatment

The adsorption capacity of ‘waste’ Fe(III)/Cr(III) hydroxide for removal of quinol at varying agitation time, quinol concentration, adsorbent dose, pH and temperature was investigated by batch method. The Langmuir isotherm was found to represent the equilibrium sorption data well and the adsorption capacity was found to be 24.4 mg g^?1 and 28.2 mg g^?1 for untreated and pre‐treated adsorbent, respectively. Adsorption followed second‐order kinetics. Adsorption was maximum and uniform in the pH range 4.0–10.0 and 6.0–10.0 for untreated and pre‐treated adsorbent, respectively. The adsorption was endothermic in nature. Application of the adsorbent to the treatment of real effluent was demonstrated.     

Application of carbon nanotube technology for removal of contaminants in drinking water: A review

Carbon nanotube (CNT) adsorption technology has the potential to support point of use (POU) based treatment approach for removal of bacterial pathogens, natural organic matter (NOM), and cyanobacterial toxins from water systems. Unlike many microporous adsorbents, CNTs possess fibrous shape with high aspect ratio, large accessible external surface area, and well developed mesopores, all contribute to the superior removal capacities of these macromolecular biomolecules and microorganisms. This article provides a comprehensive review on application of CNTs as adsorbent media to concentrate and remove pathogens, NOM, and cyanobacterial (microcystin derivatives) toxins from water systems. The paper also surveys on consideration of CNT based adsorption filters for removal of these contaminants from cost, operational and safety standpoint. Based on the studied literature it appears that POU based CNT technology looks promising, that can possibly avoid difficulties of treating biological contaminants in conventional water treatment plants, and thereby remove the burden of maintaining the biostability of treated water in the distribution systems.     

Preparation and evaluation of a novel Fe-Mn binary oxide adsorbent for effective arsenite removal

Arsenite (As(III)) is more toxic and more difficult to remove from water than arsenate (As(V)). As there is no simple treatment for the efficient removal of As(III), an oxidation step is always necessary to achieve higher removal. However, this leads to a complicated operation and is not cost-effective. To overcome these disadvantage, a novel Fe-Mn binary oxide material which combined the oxidation property of manganese dioxide and the high adsorption features to As(V) of iron oxides, were developed from low cost materials using a simultaneous oxidation and coprecipitation method. The adsorbent was characterized by BET surface areas measurement, powder XRD, SEM, and XPS. The results showed that prepared Fe-Mn binary oxide with a high surface area (265 m2 g(-1)) was amorphous. Iron and manganese existed mainly in the oxidation state +III and IV, respectively. Laboratory experiments were carried out to investigate adsorption kinetics, adsorption capacity of the adsorbent and the effect of solution pH values on arsenic removal. Batch experimental results showed that the adsorbent could completely oxidize As(III) to As(V) and was effective for both As(V) and As(III) removal, particularly the As(III). The maximal adsorption capacities of As(V) and As(III) were 0.93 mmol g(-1) and 1.77 mmol g(-1), respectively. The results compare favorably with those obtained using other adsorbent. The effects of anions such as SO4(2-), PO4(3-), SiO3(2-), CO3(2-) and humic acid (HA), which possibly exist in natural water, on As(III) removal were also investigated. The results indicated that phosphate was the greatest competitor with arsenic for adsorptive sites on the adsorbent. The presence of sulfate and HA had no significant effect on arsenic removal. The high uptake capability of the Fe-Mn binary oxide makes it potentially attractive adsorbent for the removal of As(III) from aqueous solution.     

活性氧化铝吸附水中砷的动态试验研究

近年来,饮用水砷污染事件层出不穷,选择高效合适的除砷方法,已成为全球关注的问题.试验采用逆流式单床吸附柱的吸附方式,对活性氧化铝吸附砷做了动态试验研究.研究结果显示,当初始砷浓度为10mg/L时,砷的去除率均在90%以上;当初始砷浓度为50mg/L时,以5mg/L为穿透点,穿透体积为110L,动态吸附量为3.43mg/g.结果表明,在水中砷的去除方面,活性氧化铝可作为一种有效吸附剂.该研究对实际应用中的活性氧化铝改性及饮用水处理具有重要意义.     

Permeability of low molecular weight organics through nanofiltration membranes

The removal of natural organic matter (NOM) using nanofiltration (NF) is increasingly becoming an option for drinking water treatment. Low molecular weight (LMW) organic compounds are nevertheless only partially retained by such membranes. Bacterial regrowth and biofilm formation in the drinking water distribution system is favoured by the presence of such compounds, which in this context are considered as the assimilable organic carbon (AOC). In this study, the question of whether NF produces microbiologically stable water was addressed. Two NF membranes (cut-off of about 300 Da) were tested with different natural and synthetic water samples in a cross-flow filtration unit. NOM was characterised by liquid chromatography with organic carbon detection (LC-OCD) using a size-exclusion column in addition to specific organic acid measurements, while AOC was measured in a batch growth bioassay.Similarly to high molecular weight organic compounds like polysaccharides or humic substances that have a permeability lower than 1%, charged LMW organic compounds were efficiently retained by the NF membranes tested and showed a permeability lower than 3%. However, LMW neutrals and hydrophobic organic compounds permeate to a higher extent through the membranes and have a permeability of up to 6% and 12%, respectively. Furthermore, AOC was poorly retained by NF and the apparent AOC concentration measured in the permeated water was above the proposed limit for microbiologically stable water. This indicates that the drinking water produced by NF might be biologically unstable in the distribution system. Nevertheless, in comparison with the raw water, NF significantly reduced the AOC concentration.     

Denitratation des eaux a potabiliser sur resines echangeuses d'ions—Impact sur la qualite chimique de l'eau traitee

The increase in nitrate concentration in public water supplies is becoming an important problem in certain countries. Among the treatment processes available, the removal of nitrates by ion exchange has been thoroughly studied in recent years with regard to problems of capacity and selectivity. The use of anionic resins in drinking water treatment imply that these compounds do not induce secondary degradation in the quality of the treated water.The purpose of this paper is to examine the chemical quality of water treated by a strong base ion exchange resin (IRA 400) regenerated by sodium chloride.Two sources of organic compounds can be found in water treated with a filter of ion exchange resin:The constitution monomers leached from IRA 400 (styrene, divinylbenzene, trimethylamine and their derivatives).The micropollutants liable to be adsorbed, desorbed or produced during the exhaustion cycles of denitratation.The evolution of the concentration synthesis monomers in treated water was studied during the conditioning and the exhaustion cycles of the resin. Moreover the adsorption isotherms of the IRA 400 for different kinds of micropollutants (aromatic compounds, chlorinated solvents, herbicides, nitrosamines) were determined and the concentration of an added micropollutant (phenol) was measured during an exhaustion cycle.As for the formation of organic compounds during the treatment, we have limited our study to the analysis of N-dimethylnitrosamine during the exhaustion cycle, since this compound has been detected in water demineralized by an ion exchange resin.     

Conventional oxidation treatments for the removal of arsenic with chlorine dioxide, hypochlorite, potassium permanganate and monochloramine

Arsenic is widespread in soils, water and air. In natural water the main forms are arsenite (As(III)) and arsenate (As(V)). The consumption of water containing high concentration of arsenic produces serious effects on human health, like skin and lung cancer. In Italy, Legislative Decree 2001/31 reduced the limit of arsenic from 50 to 10 μg/L, in agreement with the European Directive 98/83/EC. As consequence, many drinking water treatment plant companies needed to upgrade the existing plants where arsenic was previously removed or to build up new plants for arsenic removal when this contaminant was not previously a critical parameter.Arsenic removal from water may occur through the precipitation with iron or aluminum salts, adsorption on iron hydroxide or granular activated alumina (AA), reverse osmosis and ion exchange (IE). Some of the above techniques, especially precipitation, adsorption with AA and IE, can reach good arsenic removal yields only if arsenic is oxidized.The aim of the present work is to investigate the efficiency of the oxidation of As(III) by means of four conventional oxidants (chlorine dioxide, sodium hypochlorite, potassium permanganate and monochloramine) with different test conditions: different type of water (demineralised and real water), different pH values (5.7-6-7 and 8) and different doses of chemicals.The arsenic oxidation yields were excellent with potassium permanganate, very good with hypochlorite and low with monochloramine. These results were observed both on demineralised and real water for all the tested reagents with the exception of chlorine dioxide that showed a better arsenic oxidation on real groundwater than demineralised water.     

Remediation of pharmaceutical contaminated water by use of magnetic functionalized metal organic framework. Physicochemical study of doxycycline adsorption

The presence of pharmaceutical pollutant, doxycycline (DOC) in water and waste streams has negative impact on the environment. In this research, metal organic framework was synthesized and functionalized by potassium nickel ferrocyanide (KNiFC). After characterisation, the functionalized adsorbent was used for removal of DOC from aqueous solutions. The adsorbent containing 80% of KNiFC exhibited the high adsorption capacity of 100 mg/g. The adsorption process was kinetically fast and the equilibration was established within 30 min. The used adsorbent retained 90% of its initial capacity after regeneration. The magnetic susceptibility of the adsorbent measured by VSM technique was 35 emu/g and sufficient for separation of the used adsorbent by external magnetic field. Isotherm models including Langmuir, Freundlich, Tempkin, Redlich‐Peterson, and Sips were applied to correlate the experimental equilibrium data. To evaluate the fitness of the isotherm equations error analysis methods, residual root mean square error and average relative error were used.     

Reducing the concentration of assimilable organic carbon (AOC) in treated drinking water

This study focuses on reducing the concentration of assimilable organic carbon (AOC) in treated drinking water. Experiments were conducted to evaluate the efficiency of AOC removal by biological activated carbon filters (BACF) in a pilot-scale system. The measured values of AOC in treated drinking water were approximately 59.0 ± 8.6 μg acetate-C/L. The results show that BACFs reduce the total concentration of AOC. The concentration of AOC primarily indicates microbial growth in a water supply network, and the amount of AOC in the water is significantly reduced after BACF treatment. After BACF treatment, the removal of AOC was approximately 58% after 40 min of empty-bed contact time. An AOC empirical equation was established by determining the relationship between water quality parameters, such as total organic carbon, dissolved organic carbon, UV₂₅₄, ammonia nitrogen, and total phosphorous.     

Vulnerability of bank filtration systems to climate change

Bank filtration (BF) is a well established and proven natural water treatment technology, where surface water is infiltrated to an aquifer through river or lake banks. Improvement of water quality is achieved by a series of chemical, biological and physical processes during subsurface passage. This paper aims at identifying climate sensitive factors affecting bank filtration performance and assesses their relevance based on hypothetical ‘drought’ and ‘flood’ climate scenarios. The climate sensitive factors influencing water quantity and quality also have influence on substance removal parameters such as redox conditions and travel time. Droughts are found to promote anaerobic conditions during bank filtration passage, while flood events can drastically shorten travel time and cause breakthrough of pathogens, metals, suspended solids, DOC and organic micropollutants. The study revealed that only BF systems comprising an oxic to anoxic redox sequence ensure maximum removal efficiency. The storage capacity of the banks and availability of two source waters renders BF for drinking water supply less vulnerable than surface water or groundwater abstraction alone. Overall, BF is vulnerable to climate change although anthropogenic impacts are at least as important.     

臭氧-生物活性炭深度处理饮用水挂膜试验研究

以中置式高密度沉淀池沉后水作为进水，考察了臭氧-生物活性炭（O3-BAC）饮用水深度处理工艺的挂膜过程，并探讨了生物活性炭挂膜的影响因素。结果表明，挂膜期间O3-BAC工艺对水中浊度、CODMn及氨氮具有较好的去除效果，运行后期浊度、CODMn及氨氮的去除率分别达到50％，62．71％和62．5％以上；运行至82天时，CODMn和氨氮去除率分别大于30％和60％．生物膜趋于成熟。     

不同产地粉末状沸石去除水中低浓度氨氮性能比较

通过静态试验比较了不同产地粉末状沸石去除水中低浓度氨氮的性能。结果表明，不同产地粉末状沸石对氨氮的吸附性能差别较大，按吸附容量由高到低依次为：缙云沸石≈阜新沸石〉信阳沸石〉赤峰沸石；不同产地的粉末状沸石对氨氮的去除率达到最大时的pH值不同，缙云沸石和阜新沸石在pH值为6时对氨氮的去除率最高，信阳沸石和赤峰沸石则在pH值分别为8和10时最高。对沸石吸附前、后水中离子浓度的测定结果表明，沸石吸附氨氮不会增加水中有害离子的浓度，用于对饮用水的处理是可行的。