Evaluation of autotrophic growth of ammonia-oxidizers associated with granular activated carbon used for drinking water purification by DNA-stable isotope probing

Nitrification is an important biological function of granular activated carbon (GAC) used in advanced drinking water purification processes. Newly discovered ammonia-oxidizing archaea (AOA) have challenged the traditional understanding of ammonia oxidation, which considered ammonia-oxidizing bacteria (AOB) as the sole ammonia-oxidizers. Previous studies demonstrated the predominance of AOA on GAC, but the contributions of AOA and AOB to ammonia oxidation remain unclear. In the present study, DNA-stable isotope probing (DNA-SIP) was used to investigate the autotrophic growth of AOA and AOB associated with GAC at two different ammonium concentrations (0.14 mg N/L and 1.4 mg N/L). GAC samples collected from three full-scale drinking water purification plants in Tokyo, Japan, had different abundance of AOA and AOB. These samples were fed continuously with ammonium and ¹³C-bicarbonate for 14 days. The DNA-SIP analysis demonstrated that only AOA assimilated ¹³C-bicarbonate at low ammonium concentration, whereas AOA and AOB exhibited autotrophic growth at high ammonium concentration. This indicates that a lower ammonium concentration is preferable for AOA growth. Since AOA could not grow without ammonium, their autotrophic growth was coupled with ammonia oxidation. Overall, our results point towards an important role of AOA in nitrification in GAC filters treating low concentration of ammonium.     

Potential effects of desalinated water quality on the operation stability of wastewater treatment plants

Desalinated water is expected to become the major source of drinking water in many places in the near future, and thus the major source of wastewater to arrive at wastewater treatment plants. The paper examines the effect of the alkalinity value with which the water is released from the desalination plant on the alkalinity value that would develop within the wastewater treatment process under various nitrification-denitrification operational scenarios. The main hypothesis was that the difference in the alkalinity value between tap water and domestic wastewater is almost exclusively a result of the hydrolysis of urea (NH₂CONH₂, excreted in the human urine) to ammonia (NH₃), regardless of the question what fraction of NH_3(aq) is transformed to NH₄⁺. Results from a field study show that the ratio between the alkalinity added to tap water when raw wastewater is formed (in meq/l units) and the TAN (total ammonia nitrogen, mole/l) concentration in the raw wastewater is almost 1:1 in purely domestic sewage and close to 1:1 in domestic wastewater streams mixed with light industry wastewaters. Having established the relationship between TAN and total alkalinity in raw wastewater the paper examines three theoretical nitrification-denitrification treatment scenarios in the wastewater treatment plant (WWTP). The conclusion is that if low-alkalinity desalinated water constitutes the major water source arriving at the WWTP, external alkalinity will have to be added in order to avoid pH drop and maintain process stability. The results lead to the conclusion that supplying desalinated water with a high alkalinity value (e.g. ≥ 100 mg/l as CaCO₃) would likely prevent the need to add costly basic chemicals in the WWTP, while, in addition, it would improve the chemical and biological stability of the drinking water in the distribution system.     

多环芳烃在饮用水处理中的行为研究

采用固相萃取及气质联用(SPE-GC-MS)的方法对我国北方某市自来水中多环芳烃(PAHs)的污染水平及其在传统自来水处理过程中的行为进行了研究.结果表明:①从原水中检测出了9种PAHs,其总浓度为64～208 ng/L,并有季节性变化趋势;②从管网水中也检测出了9种PAHs,总浓度为87～198 ng/L;③常规处理工艺能去除26.8%～62.7%的PAHs,但是在管道输送过程中发现存在二次污染.     

Variations in trihalomethane levels in three French water distribution systems and the development of a predictive model

Epidemiological studies have demonstrated that chlorination by-products in drinking water may cause some types of cancer in humans. However, due to differences in methodology between the various studies, it is not possible to establish a dose-response relationship. This shortcoming is due primarily to uncertainties about how exposure is measured—made difficult by the great number of compounds present—the exposure routes involved and the variation in concentrations in water distribution systems. This is especially true for trihalomethanes for which concentrations can double between the water treatment plant and the consumer tap.The aim of this study is to describe the behaviour of trihalomethanes in three French water distribution systems and develop a mathematical model to predict concentrations in the water distribution system using data collected from treated water at the plant (i.e. the entrance of the distribution system).In 2006 and 2007, samples were taken successively from treated water at the plant and at several points in the water distribution system in three French cities. In addition to the concentrations of the four trihalomethanes (chloroform, dichlorobromomethane, chlorodibromomethane, bromoform), many other parameters involved in their formation that affect their concentration were also measured.The average trihalomethane concentration in the three water distribution systems ranged from 21.6 μg/L to 59.9 μg/L. The increase in trihalomethanes between the treated water at the plant and a given point in the water distribution system varied by a factor of 1.1-5.7 over all of the samples. A log-log linear regression model was constructed to predict THM concentrations in the water distribution system. The five variables used were trihalomethane concentration and free residual chlorine for treated water at the plant, two variables that characterize the reactivity of organic matter (specific UV absorbance (SUVA), an indicator developed for the free chlorine consumption in the treatment plant before distribution δ) and water residence time in the distribution system.French regulations impose a minimum trihalomethane level for drinking water and most tests are performed on treated water at the plant. Applied in this context, the model developed here helps better to understand trihalomethane exposure in the French population, particularly useful for epidemiological studies.     

A new concept of supplying the population with a quality drinking water

The paper has considered the causes for low quality of drinking water supplied to the consumers. We have proposed a new concept of supplying the population with drinking water. This concept provides for obtaining at the waterworks of safe water, in terms of toxicological and microbiological indicators, for use with domestic and household purposes. Such tap water is supplied to the distribution networks. Quality drinking water which is safe for human health is produced at the site of its consumption (at the plant of the well room type) and it comes to the distribution network to the consumer in other ways (self-flow or bottling). The article has considered approaches for solutions that are necessary for implementation of legislative, organizational, and technical issues.     

城市饮用水原水中亚硝酸盐的转化与控制

由于水源水水质的污染和氨氮含量的升高,水质净化或输水过程中亚硝酸盐浓度的升高已成为饮用水水质安全所关注的重要问题之一。针对某地下水源高氨氮浓度期间输水管道中存在的亚硝酸盐污染问题,研究了氯消毒工艺对亚硝酸盐转化的影响及其控制条件,对输水管道中的硝化反应过程进行了检验和分析,细菌鉴定结果表明,管道中亚硝化细菌的数量远高于硝化细菌,是造成管道中亚硝酸盐积累的主要原因;适宜的水温和pH值条件,以及较高的氨氮和较低的余氯浓度是促进水中亚硝化细菌生长与活性提高的主要因素;在水厂现行工艺条件下,提高预加氯量是解决亚硝酸盐问题的有效途径。实验条件下,加氯量为2～4mg/L时就可以有效控制亚硝酸盐的转化。     

Diversity and antibiotic resistance of Aeromonas spp. in drinking and waste water treatment plants

The taxonomic diversity and antibiotic resistance phenotypes of aeromonads were examined in samples from drinking and waste water treatment plants (surface, ground and disinfected water in a drinking water treatment plant, and raw and treated waste water) and tap water. Bacteria identification and intra-species variation were determined based on the analysis of the 16S rRNA, gyrB and cpn60 gene sequences. Resistance phenotypes were determined using the disc diffusion method.Aeromonas veronii prevailed in raw surface water, Aeromonas hydrophyla in ozonated water, and Aeromonas media and Aeromonas puntacta in waste water. No aeromonads were detected in ground water, after the chlorination tank or in tap water. Resistance to ceftazidime or meropenem was detected in isolates from the drinking water treatment plant and waste water isolates were intrinsically resistant to nalidixic acid. Most of the times, quinolone resistance was associated with the gyrA mutation in serine 83. The gene qnrS, but not the genes qnrA, B, C, D or qepA, was detected in both surface and waste water isolates. The gene aac(6’)-ib-cr was detected in different waste water strains isolated in the presence of ciprofloxacin. Both quinolone resistance genes were detected only in the species A. media. This is the first study tracking antimicrobial resistance in aeromonads in drinking, tap and waste water and the importance of these bacteria as vectors of resistance in aquatic environments is discussed.     

Tap water consumers differ from non-consumers in chlorine flavor acceptability but not sensitivity

Unpleasant taste and especially chlorine flavor is one of the most common reasons advocated for choosing tap water alternatives as drinking water. As a consequence, the putative link between sensitivity to chlorine flavor and tap water consumption is an issue in drinking water habits studies. In the present study, we set out to examine such a link following a strategy in which we measured chlorine flavor perception at threshold and supra-threshold level for two groups of participants selected on their drinking water consumption habits. The first group included exclusive tap water consumers and the second group included exclusive bottled water consumers. In a first experiment, we used the constant stimuli procedure to evaluate the chlorine flavor detection threshold of a group of 20 tap water consumers and a group of 20 non-consumers. In a second experiment, a group of 18 tap water consumers and a group of 17 non-consumers evaluated supra-threshold flavor intensity, liking and acceptability for eight chlorinated solutions (0-10 mg/L Cl₂). The results revealed no significant difference in chlorine flavor detection threshold and supra-threshold sensitivity between tap water consumers and non-consumers. Nevertheless, tap water consumers showed a higher liking score for chlorinated solutions and were found to be more inclined to accept these solutions as drinking water. Taken together these findings suggested that consumers may disparage chlorine flavor in drinking water on the basis of their tap water cognitive representation.     

Effects of chronic ammonium and nitrite contamination on the macroinvertebrate community in running water microcosms

In the present study, during a three-month exposure lethal and sublethal effects of ammonium and its products on typical brook organisms (Gammarus pulex, Amphipoda; Radix ovata, Gastropoda; Limnephilus lunatus Trichoptera) were monitored in microcosms approximating field conditions. Every 24 h during this period the microcosms were contaminated with ammonium at five different nominal concentrations, which by chemical reactions produced a mixture of the toxic products ammonia and nitrite. G. pulex proved the most sensitive to the ammonia and nitrite contamination resulting from the ammonium load. In contrast. L. lunatus and R. ovota exhibited clearly effects only at concentrations 10 times higher. It is appropriate to investigate ammonium pollution with its reaction products as a mixture, because in natural bodies of water receiving ammonium input (e.g., from sewage-treatment plants) the substances ammonium/ammonia and nitrite are likewise present simultaneously.     

Chemical water quality in Thailand and its impacts on the drinking water production in Thailand

In Thailand, surface water and groundwater are the main water sources for tap water and drinking water production. Thirty-six different samples from surface waters from Chao Praya and Mae Klong rivers, tap waters, bottled drinking waters, groundwaters and commercial ice cubes from around the Bangkok area were collected. Water samples were also taken from two waterworks in the Chonburi province. The extensive survey showed that, overall in all water samples investigated, there was only a minor pollution which could be traced back to the analyses performed including amongst others total organic carbon, inorganics and heavy metals, pesticides, organochlorine compounds, volatile organic compounds, surfactants, pharmaceuticals and disinfection by-products. However, whenever organic micropollutants could be detected in surface water, such as, e.g. the herbicide atrazine, they were also present in the tap water produced thereof proving that the present treatment steps are not sufficient for removal of such pollutants. The concentration of disinfection by-products was higher in tap water produced from Chao Praya river than from Mae Klong river. Disinfection by-products were also found in bottled drinking water. Commercial ice cubes contained anionic surfactants and their metabolites at elevated concentrations. The data of this study constitute the first set of homogenous data for the chemical water quality and also aid development of new water quality criteria in Thailand.     

Selection of an adsorbent for lead removal from drinking water by a point-of-use treatment device

The removal of lead from drinking water was investigated to develop a point-of-use water filter that could meet the regulation imposed by the new European Directive 98-83 lowering lead concentration in drinking water below 10 μg L⁻¹. The objective of this research was to assess the potential of different adsorbents (zeolites, resins, activated carbon, manganese oxides, cellulose powder) to remove lead from tap water with a very short contact time. To begin, the repartition of the lead species in a tap water and a mineral water was computed with the computer model CHESS. It showed that in bicarbonated waters lead is mainly under lead carbonate form, either in the aqueous or in the mineral phase. Batch experiments were then conducted to measure the equilibrium adsorption isotherms of the adsorbents. Then, for five of them, dynamic experiments in micro-columns were carried out to assess the outlet lead concentration level. Three adsorbents gave rise to a leakage concentration lower than 10 μg L⁻¹ and were then selected for prototypes experiments: chabasite, an activated carbon coated with a synthetic zeolite and a natural manganese oxide. The proposed method clearly showed that the measurement of equilibrium isotherms is not sufficient to predict the effectiveness of an adsorbent, and must be coupled with dynamic experiments.     

Epidemiological investigation on chronic copper toxicity to children exposed via the public drinking water supply

Copper in drinking water has been associated with Non-Indian Childhood Cirrhosis (NICC), a form of early childhood liver cirrhosis. This epidemiological study examines the exposition of infants to increased copper concentrations through drinking water from public water supplies in Berlin, Germany, and if this dietary copper intake can cause liver damage in early childhood. In total, water samples from 2944 households with infants were tested for copper. Mean copper concentrations in the two different types of collected composite samples were 0.44 and 0.56 mg/l, respectively. Families having a copper concentration at or above 0.8 mg/l in one or both of the composite samples (29.9% of all sampled households) and a defined minimum ingestion of tap water of their infant were recommended to undergo a paediatric examination. Nearly every of the 541 recommended infants were examined by a local paediatrician and of these 183 received a blood serum analysis, too. None of the infants had clear signs of a liver disease although a few serum parameters lay outside the accompanying reference range and abdominal ultrasound imaging gave slightly unusual results in five cases. Additionally, no signs of a negative health effect could be found in the statistical analysis of the serum parameters GOT, GPT, GGT, total bilirubin, serum copper, or ceruloplasmin in relation to estimated daily and total copper intakes of the infants from tap water. No dose relation of serum parameters and estimated copper intakes could be established. From the results of the study, no confirmed indication of a liver malfunction in infants whose food had been prepared using tap water with an elevated copper concentration could be found and, therefore, no indication of a hazard due to copper pipes connected to public water supplies could be detected.     

Assessment of ammonia toxicity in tests with the microalga,Nephroselmis pyriformis,Chlorophyta

Previous studies of an industrial effluent have indicated toxic effects by the ammonium/water system in tests with the unicellular green alga, Nephroselmis pyriformis. This investigation was undertaken to determine the toxicity of ammonia to this alga, and to identify the dominant toxicant in an industrial process effluent. The algal standard test was modified to improve the pH control, i.e. by testing at shorter exposure time and in the presence of a buffering agent, 3 mM HEPES. Ammonia was found to be the predominant toxic form in the dissociating ammonium/water system and the specific toxicity of ammonia (EC50, 24 h exposure) was 2.34 microM (32.8 microg ammonia nitrogen/L). Due to the dissociation, the toxicity is strongly pH dependent. Joint toxicity with additive effects of ammonia and ammonium ions was indicated, but the toxicity of ammonium ions was almost a factor 100 less (EC50, 24 h exposure, 224 microM or 3140 microg ammonium-nitrogen/L). According to the results the EC50 for effect on growth rate of N. pyriformis in seawater of pH 8.0 is 71 microM total ammonium. Hence, this alga appears to be more sensitive to ammonia than other studied marine plankton algae. Ammonia was found to be the dominant toxicant in the industrial effluent, using N. pyriformis as test organism.     

Total selenium concentration in tap and bottled drinking water and coastal waters of Greece

The total selenium concentration in various waters from all over Greece was determined fluorimetrically. The concentration in most of the drinking water, either from the tap or bottled, was within the range 100-200 ng l-1 and showed no great seasonal fluctuations. Most Greeks receive 0.2-0.4 micrograms selenium per day from drinking water. Coastal surface water contains 100-250 ng Se l-1, while higher concentrations are found at locations regarded as polluted.     

Nitrification and potential control mechanisms in simulated premises plumbing

Indigenous drinking water organisms were used to establish nitrification in glass reactors containing copper or polyvinyl chloride (PVC) surfaces. The reactors were fed soil-derived humics as the organic carbon source and ammonium sulfate as the nitrogen source in biologically treated tap water. Water in the reactors was stagnant for 8 h and then flowed for 5 min to simulate conditions in household plumbing. Following the establishment of complete nitrification (conversion of ammonia to nitrate) in both reactor types, various inhibitors of nitrification were tested followed by a period where recovery of nitrification was observed. In one PVC reactor, copper was gradually introduced up to 1.3 ppm. To ensure that most of the copper was in the ionic form, the pH of the influent was then gradually lowered to 6.6. No significant change in nitrification was observed in the presence of copper. Chlorite was introduced into copper and PVC reactors at doses increasing from 0.2 ppm to 20 ppm. There was limited effect on the PVC system and inhibition in the copper reactor only at 20 ppm. Chloramine was tested at chlorine to ammonia ratios ranging from 0.5:1 to 5:1. Nitrification activity was impacted significantly at a 5:1 ratio and ultimately stopped, with the fastest response being in the copper system. Whenever a control mechanism was tested, there was increased release of copper from the reactors with copper coupons. In all cases, nitrification recovered when inhibitors were removed but the rates of recovery differed depending on the treatment method and coupon surface.     

武汉市主要供水水源地水质参数反演研究

以武汉市的主要供水水源地水质参数（氨氮）为研究对象,利用某时段的实测数据和遥感影像数据,尝试性地建立了氨氮含量的回归反演模型。精度和可用性检验结果表明,氨氮模型的反演精度较好,最大平均相对误差为10．02％,最小为6．28％,可以用来进行氨氮含量参数的反演。     

Trihalomethane formation by chlorination of ammonium- and bromide-containing groundwater in water supplies of Hanoi, Vietnam

The occurrence and the fate of trihalomethanes (THMs) in the water supply system of Hanoi City, Vietnam was investigated from 1998 to 2001. The chlorination efficiency, THM speciation, and, THM formation potential (THMFP) was determined in the water works and in tap water. With regard to THM formation, three types of groundwater resources were identified: (I) high bromide, (II) low bromide, and (III) high bromide combined with high ammonia and high dissolved organic carbon (DOC) concentrations. Under typical treatment conditions (total chlorine residual 0.5-0.8 mg/L), the total THM formation was always below WHO, EU, and USEPA drinking water standards and decreased in the order type I > type II > type III, although the THMFP was > 400 micrograms/L for type III water. The speciation showed > 80% of bromo-THMs in type I water due to the noticeable high bromide level (< or = 140 micrograms/L). In type II water, the bromo-THMs still accounted for some 40% although the bromide concentration is significantly lower (< or = 30 micrograms/L). In contrast, only traces of bromo-THMs were formed (approximately 5%) in type III water, despite bromide levels were high (< or = 240 micrograms/L). This observation could be explained by competition kinetics of chlorine reacting with ammonia and bromide. Based on chlorine exposure (CT) estimations, it was concluded that the current chlorination practice for type I and II waters is sufficient for > or = 2-log inactivation of Giardia lamblia cysts. However, in type III water the applied chlorine is masked as chloramine with a much lower disinfection efficiency. In addition to high levels of ammonia, type III groundwater is also contaminated by arsenic that is not satisfactory removed during treatment. N-nitrosodimethylamine, a potential carcinogen suspected to be formed during chloramination processes, was below the detection limit of 0.02 microgram/L in type III water.     

MAP法处理高氨氮废水的影响因素研究

采用磷酸铵镁沉淀法处理高氨氮废水,考察了pH、反应温度、反应时间以及镁盐和磷盐沉淀剂与氨氮的配比等因素对去除氨氮的影响.结果表明,在pH值为10、Mg:N:P(物质的量之比)=1.1:1.0:1.3、温度为18～30 ℃的条件下,自动搅拌、反应并沉淀20 min,氨氮浓度可由1 000 mg/L降到76 mg/L,去除率高达92.4%,为后续生化处理奠定了基础.     

重庆小城镇居民用水状况研究

对重庆小城镇(市)———永川、黔江居民生活用水状况调查研究表明:2004年两座城市居民实际人均用水量与居民的家庭收入具有一定的相关性,但总体而言仍低于现行规范值。居民对现有的自来水水质满意程度不一,26.21%的居民对现在的自来水水质非常不满意或不满意,74.6%的居民都希望供水的卫生状况得到改善,27.27%的居民希望有直饮水供应,并且被调查的居民中已有56.68%的家庭将桶装水作为饮用水。85%以上的家庭愿意为自来水质改善和污水处理支付费用。     

部分城市自来水中典型无机金属元素的达标状况

针对当前给水管网中出现的无机金属元素超标问题,以36个城市的给水管网为研究对象,在不同时段采集龙头水并利用电感耦合等离子体质谱法对水样中常见无机金属元素进行检测分析,系统评价了现有市政管网中金属元素的达标状况和超标原因,并提出了相应的改善对策。结果表明,在调查范围内,铬、镍、镉、硒、铜和锌6种元素的含量均符合《生活饮用水卫生标准》(GB 5749—2006)。管网高峰水(早上08:30)中的铁、铅和铝以及初流水(凌晨05:30)中的铁超标率达到10%以上。除水源水的贡献外,龙头水中的无机金属含量主要受管材及其使用年限的影响。因此,在提高出厂水水质的基础上,建议通过优化管网运行管理、更换管材等方式控制无机金属元素的超标风险。