控制饮用水原水中藻类、藻毒素的水厂处理工艺

介绍了国内外对原水中藻类、藻毒素的去除方法,其中对藻类及其胞内藻毒素的去除主要有预过滤、强化混凝、气浮等技术,对细胞外溶解性藻毒素的去除主要有生物预处理、活性炭吸附、膜过滤、臭氧及紫外线等高级氧化工艺。通过分析这些工艺的优缺点及研究进展,提出了一些可行性优化组合方案并展望了可能的发展方向。     

Removal of MS2, Qβ and GA bacteriophages during drinking water treatment at pilot scale

The removal of MS2, Qβ and GA, F-specific RNA bacteriophages, potential surrogates for pathogenic waterborne viruses, was investigated during a conventional drinking water treatment at pilot scale by using river water, artificially and independently spiked with these bacteriophages. The objective of this work is to develop a standard system for assessing the effectiveness of drinking water plants with respect to the removal of MS2, Qβ and GA bacteriophages by a conventional pre-treatment process (coagulation-flocculation-settling-sand filtration) followed or not by an ultrafiltration (UF) membrane (complete treatment process). The specific performances of three UF membranes alone were assessed by using (i) pre-treated water and (ii) 0.1 mM sterile phosphate buffer solution (PBS), spiked with bacteriophages. These UF membranes tested in this work were designed for drinking water treatment market and were also selected for research purpose.The hypothesis serving as base for this study was that the interfacial properties for these three bacteriophages, in terms of electrostatic charge and the degree of hydrophobicity, could induce variations in the removal performances achieved by drinking water treatments.The comparison of the results showed a similar behaviour for both MS2 and Qβ surrogates whereas it was particularly atypical for the GA surrogate. The infectious character of MS2 and Qβ bacteriophages was mostly removed after clarification followed by sand filtration processes (more than a 4.8-log reduction) while genomic copies were removed at more than a 4.0-log after the complete treatment process. On the contrary, GA bacteriophage was only slightly removed by clarification followed by sand filtration, with less than1.7-log and 1.2-log reduction, respectively. After the complete treatment process achieved, GA bacteriophage was removed with less than 2.2-log and 1.6-log reduction, respectively.The effectiveness of the three UF membranes tested in terms of bacteriophages removal showed significant differences, especially for GA bacteriophage. These results could provide recommendations for drinking water suppliers in terms of selection criteria for membranes.MS2 bacteriophage is widely used as a surrogate for pathogenic waterborne viruses in Europe and the United States. In this study, the choice of MS2 bacteriophage as the best surrogate to be used for assessment of the effectiveness of drinking water treatment in removal of pathogenic waterborne viruses in worst conditions is clearly challenged. It was shown that GA bacteriophage is potentially a better surrogate as a worst case than MS2. Considering GA bacteriophage as the best surrogate in this study, a chlorine disinfection step could guaranteed a complete removal of this model and ensure the safety character of drinking water plants.     

压缩活性炭与超滤深度处理饮用水

研究了压缩活性炭净化饮用水的性能，并与超滤法去除有机污染的效果进行了比较，探讨了压缩活性炭—超滤工艺制备优质饮用水的可行性。试验结果表明，在流动状态下压缩活性炭去除有机污染的效率高于超滤，对CODMn、TOC、UV254和浊度的平均去除率分别为67．5％、74．1％、97．6％和50％以上，可用作超滤的预处理；压缩活性炭一超滤工艺可用于制备优质饮用水。     

Experiences of algal bloom control using green solutions barley straw and ultrasound,an industry perspective

Water companies in the United Kingdom have been dealing with seasonal algal blooms for many decades, with escalating costs as bloom occurrences have increased markedly with elevated demand on water supply. Environmentally friendly water treatment solutions, such as ultrasound and barley straw, are defined as those that use less energy and chemicals. Barley straw has been used quite extensively by certain UK water companies, and results are generally positive. Ultrasound has only recently been used as a treatment for algal removal, with limited results from several successful trials finding cyanobacteria to be the most susceptible algal group at field scale, with results also indicating susceptibility in other algal groups; however, energy costs are higher than barley straw. Ultrasound has been extremely successful at removing bacteria in wastewater treatment; therefore, ultrasound should be considered as an in‐works solution where its effectiveness would be enhanced while reducing energy requirements.     

Formation of assimilable organic carbon (AOC) and specific natural organic matter (NOM) fractions during ozonation of phytoplankton

Ozonation of natural surface water increases the concentration of oxygen-containing low molecular weight compounds. Many of these compounds support microbiological growth and as such are termed assimilable organic carbon (AOC). Phytoplankton can contribute substantially to the organic carbon load when surface water is used as source for drinking water treatment. We have investigated dissolved organic carbon (DOC) formation from the ozonation of a pure culture of Scenedesmus vacuolatus under defined laboratory conditions, using a combination of DOC fractionation, analysis of selected organic acids, aldehydes and ketones, and an AOC bioassay. Ozonation of algae caused a substantial increase in the concentration of DOC and AOC, notably nearly instantaneously upon exposure to ozone. As a result of ozone exposure the algal cells shrunk, without disintegrating entirely, suggesting that DOC from the cell cytoplasm leaked through compromised cell membranes. We have further illustrated that the specific composition of newly formed AOC (as concentration of organic acids, aldehydes and ketones) in ozonated lake water differed in the presence and absence of additional algal biomass. It is therefore conceivable that strategies for the removal of phytoplankton before pre-ozonation should be considered during the design of drinking water treatment installations, particularly when surface water is used.     

臭氧/氯消毒中藻类有机物生成消毒副产物的特征

饮用水源地藻华会释放大量藻类有机物(AOM),AOM与氯消毒剂反应生成的消毒副产物(DBPs)会给饮用水用户带来不容忽视的健康风险。为此,探究了臭氧/氯消毒对AOM结构和DBPs生成的影响。结果表明,臭氧氧化能有效去除AOM中芳香蛋白和酚类、叶绿素a、藻蓝蛋白结构物质,但是对腐殖酸类结构的去除效果相对较差。DBPs生成总量随臭氧投加浓度的升高而增加,其中主要是三氯甲烷(TCM);卤代乙腈和卤代酮的生成总量随臭氧投加浓度的变化趋势不明显。延长臭氧接触时间会明显增加1 h氯化中TCM的生成量,氯化24 h时DBPs生成总量与臭氧接触时间无关。在臭氧/氯消毒过程中,AOM的DBPs生成潜能低于天然有机物(NOM)。AOM有利于一溴一氯乙腈的生成,而NOM会生成更多的二氯乙腈。     

Disinfection by-products and their precursors in a water treatment plant in North China: Seasonal changes and fraction analysis

A one-year-long monitoring project was conducted to assay the concentrations of THMs, HAAs and their formation potential along the conventional process in a water treatment plant in North China. Subsequent investigations of organic matter fractionation and the contribution of the algae to the precursor were also conducted to trace the source of the DBPs. The results showed that the concentration of DBPs and their formation potential varied with the seasons. The highest concentrations of THMs and the highest HAAs formation potential, each almost 500 microg/L, were detected in autumn and the lowest were in spring, no more than 100 microg/L. Both organic matter and algae were found to be important DBP precursors. The hydrophobic acid fraction in dissolved organic matter has the highest formation potential for both THM and HAA. Algae contribute about 20% to 50% of the total formation potential during an algal bloom. The efficiency of each unit process for DBPs and precursors was also assayed. Unfortunately, the conventional drinking water treatment process is limited in its efficiency for precursor removal. The pre-chlorination and filtration process had a negative effect on DBP or precursor removal.     

Fate of perfluorooctanesulfonate and perfluorooctanoate in drinking water treatment processes

Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) have been recognized as global environmental pollutants. Although PFOS and PFOA have been detected in tap water from Japan and several other countries, very few studies have examined the fate, especially removal, of perfluorinated compounds (PFCs) in drinking water treatment processes. In this study, we analyzed PFOS and PFOA at every stages of drinking water treatment processes in several water purification plants that employ advanced water treatment technologies. PFOS and PFOA concentrations did not vary considerably in raw water, sand filtered water, settled water, and ozonated water. Sand filtration and ozonation did not have an effect on the removal of PFOS and PFOA in drinking water. PFOS and PFOA were removed effectively by activated carbon that had been used for less than one year. However, activated carbon that had been used for a longer period of time (>1 year) was not effective in removing PFOS and PFOA from water. Variations in the removal ratios of PFOS and PFOA by activated carbon were found between summer and winter months.     

Design and evaluation of hydraulic baffled-channel PAC contactor for taste and odor removal from drinking water supplies

Based on the concept of hydraulic flocculator, a baffled-channel powdered activated carbon (PAC) contactor, placed before the rapid-mixing basin, was designed and evaluated for removal of taste and odor (T&O) in drinking water. PAC adsorption kinetic tests for raw water samples were conducted for selection of design parameters related to contact time and degree of mixing. Within the tested range of velocity gradient (G) from 18 to 83s(-1), mixing had a relatively minor effect on the adsorption kinetics of the PAC. The hydrodynamic characteristics of the pilot-scale horizontally and vertically baffled-channel PAC contactor were investigated by tracer tests. It was found that the plug flow fractions of vertically baffled-channel PAC contactor (vBPC) were higher than those of the horizontally baffled-channel PAC contactor (hBPC) for the same bend width or bend height. However, the hBPC seems to be more appropriate than the vBPC in terms of construction and maintenance. The geosmin and MIB removal rate increased with the number of baffles, PAC dose and contact time increased regardless of bend width in the pilot-scale hBPC. The pair of full-scale hBPCs at Pohang water treatment plant, having a design capacity of 6.5x10(4)m(3)/d with 20min of hydraulic retention time with a safety factor of 2, was designed based on lab- and pilot-scale experimental results. Under a velocity gradient of 20s(-1), the number of baffles to be installed was calculated to be 20 with a space of about 2m between each baffle, resulting in a hydraulic head loss through the contactor of about 0.056m. The successful application of hBPC for T&O removal from drinking water supplies should provide momentum for developing more effective treatment methods.     

DOC removal by multi-stage ozonation-biological treatment

Multi-stage ozonation-biological treatment process for dissolved organic carbon (DOC) removal was evaluated to apply for drinking water treatment. Waters with different types of DOC were used, i.e. a reservoir water for drinking water supply, a secondary effluent from a municipal wastewater treatment plant and a solution of humic substances extracted from leaf mold. The multi-stage ozonation-biological treatment process was compared with conventional single-stage ozonation-biological treatment process. Amount of DOC removed in biological treatment was defined as amount of biodegradable dissolved organic carbon (BDOC) in influent of biological treatment. DOC removal in the multi-stage ozonation-biological treatment was higher than that in the conventional single-stage ozonation-biological treatment with the same total ozonation time for the reservoir water and humic substances solution. Moreover, three- or four-stage ozonation for 5 min followed by biological treatment (total ozonation time 15 or 20 min) showed higher removal of DOC than the single-stage ozonation (60 min) and biological treatment. The higher DOC removal in the multi-stage treatment was due to the production of BDOC by ozonation. The long-term ozonation was not effective to produce BDOC because most of ozone was utilized to oxidize BDOC produced in the early stage of ozonation. In the multi-stage treatment, ozonation was effective to decompose refractory DOC and to produce BDOC because BDOC was removed by biological treatment. However, multi-stage ozonation-biological treatment was not effective for the secondary effluent. The reason seems to be high concentration of ozone scavengers in that water and low reactivity of DOC for ozone.     

Current status of arsenic contamination in drinking water and treatment practice in some rural areas of West Bengal,India

The aim of the present investigation was to draw the current scenario of arsenic (As) contamination in drinking water of community tube well and drinking water treated by tube wells installed with different adsorbent media-based treatment plants in districts Nadia, Hooghly and North 24-Parganas districts, West Bengal, India. As removal efficiencies of different treatment plants varied from 23 to 71%, which is largely governed by adsorption capacity of adsorbent and influencing environmental factors. Though investigated treatment plants removed substantial amount of As from tube well water, high As concentration in treated drinking water was retained after passing through the treatment plants. This high level of As concentration in tube well water and retention of high As concentration in treated drinking water were severe for the consumers which therefore, indicating the improvement of removal efficiency of treatment plant by meticulously considering favorable influencing factors or/and application of other high capacity treatment alternatives to adsorb the excess As retained in drinking water and regular monitoring of As concentration in the treated drinking water are indispensable.     

新型滤料生物滤池除锰技术在农村饮用水中的应用

根据锰氧化细菌的生物除锰作用,依托于新型滤料生物滤池,提出了简单曝气+一级生物过滤的饮用水生物处理工艺,实现了锰的高效生物去除效果;同时,对新型滤料生物滤池除锰的长期运行效果进行了分析。结果表明,这种饮用水生物除锰工艺是一种经济高效、运行稳定的处理方法,适合应用于受锰污染的农村饮用水水源的处理中。     

Investigating norovirus removal by microfiltration,ultrafiltration, and precoagulation–microfiltration processes using recombinant norovirus virus-like particles and real-time immuno-PCR

The removal of microorganisms by drinking water treatment processes has been widely investigated in laboratory-scale experiments using artificially propagated microorganisms. However, this approach cannot be applied to norovirus removal, because this virus does not grow in cell or organ culture, and this fact has hampered our ability to investigate its behavior during drinking water treatment. To overcome this difficulty, our research group previously used recombinant norovirus virus-like particles (rNV-VLPs), which consist of an artificially expressed norovirus capsid protein, in laboratory-scale drinking water treatment experiments. However, the enzyme-linked immunosorbent assay (ELISA) method generally used to detect rNV-VLPs is not sensitive enough to evaluate high removal ratios such as those obtained by ultrafiltration (UF). We therefore developed and applied a real-time immuno-polymerase chain reaction (iPCR) assay for rNV-VLP quantification to investigate norovirus removal by microfiltration (MF), UF, and hybrid precoagulation–MF processes. The rNV-VLP detection limit with the developed iPCR assay was improved at least 1000-fold compared with ELISA. Whereas MF with a nominal pore size of 0.1 μm could not eliminate NV-VLPs, a 4-log reduction was achieved by UF with a molecular weight cutoff of 1 kDa. When MF was combined with precoagulation (≥10 μmol-Fe/L for ferric chloride; ≥20 μmol-Al/L for polyaluminum chloride; ≥40 μmol-Al/L for alum), the performance of the hybrid process in eliminating rNV-VLPs was greater than that achieved by the 1 kDa UF. For all processes, the removal ratios of the bacteriophages MS2 and Qβ were greater than the rNV-VLP removal ratios by 1–2 logs, so neither bacteriophage can be recommended as a possible conservative surrogate for predicting the behavior of native NV during these processes.     

The effect of biofilter loading rate on the removal of organic ozonation by-products

The effect of biofilter loading rate on the removal of organic ozonation by-products (OBPs) was studied in three biofilters used for the pretreatment of drinking water. One of the biofilters contained plastic biofilm media (KMT) and the two others contained expanded clay aggregates (Filtralite). Tests were carried out with ozonated humic water at several OBP concentration levels using empty bed contact times (EBCTs) from 6.2 to 48 min. The sum of aldehyde (formaldehyde, acetaldehyde, glyoxal and methyl glyoxal) and acetone concentrations ranged from 21 to 77 μg l⁻¹ in the ozonated water. The total ketoacid (glyoxylic, pyruvic, and ketomalonic acids) concentrations varied from 92 to 521 μg l⁻¹. The results were modelled using a first-order model including parameter for minimum substrate concentration (S_min). The OBPs showed different sensitivities to decreasing EBCT. Formaldehyde and pyruvic acid had the highest specific removal rates and their removal was little affected by increased loading rate. Ketomalonic acid had the lowest specific removal rate and its removal efficiency was reduced most with decreasing EBCT. The other studied OBPs had specific removal rates close to each other. The ketoacids had higher S_min concentrations than aldehydes and the S_min concentrations were influenced by the influent OBP concentrations. The biofilter media did not have a significant effect on OBP removal efficiency. Generally, over 80% removal efficiency was obtained for OBPs at EBCTs over 20 min. The significance of OBP concentrations close to S_min for the biological stability of drinking water needs to be determined.     

Investigation of assimilable organic carbon (AOC) in flemish drinking water

The aim of the study was to investigate the drinking water supplied to majority of residents of Flanders in Belgium. Over 500 water samples were collected from different locations, after particular and complete treatment procedure to evaluate the efficiency of each treatment step in production of biologically stable drinking water. In this study assimilable organic carbon (AOC) was of our interest and was assumed as a parameter responsible for water biostability. The influence of seasons and temperature changes on AOC content was also taken into account. The AOC in most of the non-chlorinated product water of the studied treatment plants could not meet the biostability criteria of 10 mug/l, resulting in the mean AOC concentration of 50 microg/l. However, majority of the examined chlorinated water samples were consistent with proposed criteria of 50--100 microg/l for systems maintaining disinfectant residual. Here, mean AOC concentration of 72 microg/l was obtained. Granular activated carbon filtration was helpful in diminishing AOC content of drinking water; however, the nutrient removal was enhanced by biological process incorporated into water treatment (biological activated carbon filtration). Disinfection by means of chlorination and ozonation increased the water AOC concentration while the ultraviolet irradiation showed no impact on the AOC content. Examination of seasonal AOC variations showed similar fluctuations in six units with the highest values in summer and lowest in winter.     

雌激素活性作为饮用水水质指标的探讨

当前饮用水常规处理工艺对具有雌激素活性内分泌干扰物的去除效果较差，而饮用水水质指标中缺乏对这类物质的限制标准。为此探讨了雌激素活性作为饮用水水质指标的可行性，初步设定饮用水的雌激素活性安全阈值为0．4ngEEQ／L。     

纳滤用于饮用水深度处理的研究

采用纳滤膜对某市自来水进行深度处理试验,研究了纳滤对自来水中有机物及离子等的去除效果.结果表明,采用一级纳滤工艺,在回收率为70%的情况下,能有效去除自来水中的有机物、离子、内分泌干扰物和细菌等.对CODMn浊度、Cr6+和阿特拉津的平均去除率分别为81.06%,85.47%,77.20%和83.90%;对总硬度和阴离子的去除率保持在一个适中的水平;出水中未检测出细菌.     

O3／H2O2艺去除饮用水中2-MIB的效能与机制

以2-甲基异莰醇（MIB）为嗅味物质的代表物,采用过氧化氢／臭氧氧化（O3／H2O2）工艺去除水中嗅味物质,考察了O3／H2O2工艺对水中2一MIB的去除效能与主导作用机制。研究表明,投加H2O2显著提高了单独0,氧化对2-MIB的去除效能,H2O2与O3最佳物质的量比为0．3：1,且2-MIB去除效果随pH值的升高而升高。叔丁醇对2-MIB的去除表现出显著的抑制作用,在O3氧化2-MIB过程中,除O3分子氧化2-MIB外,O3在水中自分解产生的强氧化性的羟基自由基（HO·）也具有协同氧化作用。不同浓度的天然有机物（NOM）对2-MIB去除效果的影响不同,较低浓度的NOM促进了2-MIB的去除,但随着其浓度的升高,2-MIB去除率明显降低。O3／H2O2工艺对水中2-MIB表现出良好的去除效果,是强化去除水中2-MIB等致臭微量有机物的重要工艺。     

Effects of water chemistry on arsenic removal from drinking water by electrocoagulation

Exposure to arsenic through drinking water poses a threat to human health. Electrocoagulation is a water treatment technology that involves electrolytic oxidation of anode materials and in-situ generation of coagulant. The electrochemical generation of coagulant is an alternative to using chemical coagulants, and the process can also oxidize As(III) to As(V). Batch electrocoagulation experiments were performed in the laboratory using iron electrodes. The experiments quantified the effects of pH, initial arsenic concentration and oxidation state, and concentrations of dissolved phosphate, silica and sulfate on the rate and extent of arsenic removal. The iron generated during electrocoagulation precipitated as lepidocrocite (γ-FeOOH), except when dissolved silica was present, and arsenic was removed by adsorption to the lepidocrocite. Arsenic removal was slower at higher pH. When solutions initially contained As(III), a portion of the As(III) was oxidized to As(V) during electrocoagulation. As(V) removal was faster than As(III) removal. The presence of 1 and 4 mg/L phosphate inhibited arsenic removal, while the presence of 5 and 20 mg/L silica or 10 and 50 mg/L sulfate had no significant effect on arsenic removal. For most conditions examined in this study, over 99.9% arsenic removal efficiency was achieved. Electrocoagulation was also highly effective at removing arsenic from drinking water in field trials conducted in a village in Eastern India. By using operation times long enough to produce sufficient iron oxide for removal of both phosphate and arsenate, the performance of the systems in field trials was not inhibited by high phosphate concentrations.