MIB Concentrations Research Articles

The predominant phytoplankton of Pseudoanabaena holding specific biosynthesis gene-derived occurrence of 2-MIB in a drinking water reservoir.

With the increasing occurrence of water eutrophication and blooms, earthy-musty odor problems caused by cyanobacteria have been more and more apparent. These problems have a serious impact on aquatic ecosystems and drinking water safety and become one of the priorities of the water environment researches and managements. In the present study, genes associated with 2-MIB synthesis in cyanobacteria were studied by systematic investigation on molecular characterization and quantity of 2-MIB-producing cyanobacteria in China. Our results founded that Pseudoanabaena is an important 2-MIB-producing phytoplankton and predominant in summer in Qingcaosha reservoir, and the copy number of mic and 2-MIB concentration have strongly positive correlation. We also demonstrated that abundance of mic in water was significant correlation with that in sediment. These results will help us to understand the main taxa of the odoriferous cyanobacteria in the water bodies in China, understand the genetic basis of the odor substances in the cyanobacteria. Rapid, reliable monitoring and ecological research methods for the production of odor cyanobacteria in water bodies can be established based on these results.

A Simple Alternative Method for Preservation of 2-Methylisoborneol in Water Samples.

2-Methylisoborneol (2-MIB) is one of the most commonly observed taste and odor (T&O) compounds present in drinking water sources. As it is biodegradable, a preservation agent, typically mercury chloride, is needed if the water is not analyzed right after sampling. Since mercury is a toxic metal, an alternative chemical that is cheaper and less toxic is desirable. In this study, two chemicals commonly used in water treatment processes, chlorine (as sodium hypochlorite) and KMnO4 (potassium permanganate), are studied to determine their feasibility as preservation agents for 2-MIB in water. Preservation experiments were first conducted in deionized water spiked with 2-MIB and with chlorine or permanganate at 4 and 25 °C. The results indicate that 2-MIB concentrations in the water samples spiked with both chemicals remained almost constant within 14 days for all the tested conditions, suggesting that oxidation and volatilization did not cause the loss of 2-MIB in the system. The experiments were further conducted for three different reservoir water samples with 30–60 ng/L of indulgent 2-MIB. The experimental results demonstrated that preservation with permanganate may have underestimated the 2-MIB concentration in the samples as a result of the formation of manganese dioxide particles in natural water and adsorption of 2-MIB onto the particles. Chlorine was demonstrated to be a good preservation agent for all three tested natural waters since oxidation of 2-MIB was negligible and biodegradation was inhibited. When the residual chlorine concentrations were controlled to be higher than 0.5 mg/L on the final day (day 14) of the experiments, the concentration reduction of 2-MIB became lower than 13% at both of the tested temperatures. The results demonstrated that sodium hypochlorite can be used as an alternative preservation agent for 2-MIB in water before analysis.

Variations in output and the off-flavor compounds geosmin and 2-methylisoborneol in different tilapia cultivation systems

PDF HTML阅读 XML下载 导出引用 引用提醒 罗非鱼不同养殖系统对产出效果及异味物质含量的影响 DOI: 作者: 作者单位: 1. 上海海洋大学省部共建水产种质资源发掘与利用教育部重点实验室, 上海 201306;2. 通威股份有限公司, 四川 成都 610041;3. 宁波检验检疫科学技术研究院, 浙江 宁波 315012 作者简介: 张凯(1992-),男,专业硕士研究生,研究方向为鱼类生态养殖技术.E-mail:mkaizhang@sina.com 通讯作者: 中图分类号: S96 基金项目: 欧盟委员会第七框架协议项目（222889）；通威股份有限公司合作项目. Variations in output and the off-flavor compounds geosmin and 2-methylisoborneol in different tilapia cultivation systems Author: Affiliation: 1. Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education;Shanghai Ocean University, Shanghai 201306, China;2. Tongwei Group Co. Ltd, Chengdu 610041, China;3. Ningbo Academy of Inspection and Quarantine of China, Ningbo 315012, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:对鱼菜共生系统、底排污系统、底排污+鱼菜共生3种养殖系统的水质变化和罗非鱼产出效果进行了分析，并利用微波蒸馏-吹扫捕集-气相色谱质谱联用技术检测了各系统水体中和罗非鱼肌肉中异味物质的含量变化。经过12周的养殖实验，对终重、生物量、特定生长率、饵料系数、增重率等指标进行测量比较，结果发现，罗非鱼的产出效果从优到差依次为：鱼菜共生组、底排污+鱼菜共生组、底排污组、对照组；底排污+鱼菜共生系统水体中溶解氧在各时期均最高，其亚硝氮、氨氮含量在各时期均最低；底排污或鱼菜共生系统均能有效降低养殖水体中异味物质2-MIB和GSM含量；对照组罗非鱼肌肉中异味物质含量最高，2-MIB和GSM分别达到（0.67±0.02）μg/kg和（0.870±0.018）μg/kg，而底排污+鱼菜共生组罗非鱼肌肉中异味物质含量在各时期最低，2-MIB和GSM分别为（0.31±0.02）μg/kg和（0.53±0.042）μg/kg。结果表明，在罗非鱼精养池塘中，可通过底排污和鱼菜共生结合，降低水体中和罗非鱼体内异味物质的累积，提高其经济价值。 Abstract:This study compared the effects of four different tilapia cultivation systems (a tilapia-water spinach integrated system, a sewage discharging system, a sewage discharging and tilapia-water spinach integrated system, and a tilapia monoculture system as a control) on the variations in water quality, tilapia production, and off-flavor contents in water and tilapia in June, July, and August 2016. Using gas chromatography and mass spectrometry (GC-MS) based on microwave-assisted distillation followed by purge-and-trap, the off-flavor compounds geosmin (GSM) and 2-methylisoborneol (2-MIB) were determined in water and tilapia tissue. The results showed that production in the tilapia-water spinach integrated system was the highest among the systems examined (<0.05). The contents of ammonia nitrogen and nitrite in the sewage discharging and tilapia-water spinach integrated system were significantly lower compared with the control group[(0.67±0.02) μg/kg and (0.870±0.018) μg/kg]. In addition, the concentrations of 2-MIB and GSM in the muscle of tilapia in the sewage discharging and tilapia-water spinach integrated system[(0.31±0.02) μg/kg and (0.53±0.042) μg/kg] were significantly lower than those in the control group[(0.67±0.02) μg/kg and (0.870±0.018) μg/kg, respectively]. These results indicate that the sewage discharging and tilapia-water spinach integrated system reduced the accumulation of off-flavor compounds in water and tilapia muscle in an intensive tilapia farming system. 参考文献 相似文献 引证文献

Earthy and Musty Off‐Flavor Episodes in Catfish Split‐Pond Aquaculture Systems

AbstractThe interest and use of variations of partitioned aquaculture systems (PAS) by the catfish farming industry in the southeastern USA continues to grow. Split‐pond systems, one type of PAS, are designed to improve the management of dissolved oxygen levels and fish waste products (e.g., ammonia) compared with conventional earthen ponds that have been used for many decades. While recent studies of split‐pond systems have focused on design, water flow rates, and management practices, there has not been any assessment of the occurrences and intensities of common “off‐flavor” episodes in these split‐ponds. For the current study, pond water samples were collected from split‐ponds at a commercial fish farm in western Alabama and at a research facility in western Mississippi approximately every 3–4 weeks during the fish grow‐out period (May to November) during 2014 and 2015. In addition, fillet samples from hybrid catfish (Channel Catfish Ictalurus punctatus × Blue Catfish Ictalurus furcatus) were obtained in late summer and autumn from these same split‐ponds. Concentrations of the “earthy” and “musty” off‐flavor compounds geosmin and 2‐methylisoborneol (MIB), respectively, in water and fillet samples were determined. Sensory analysis was also performed on catfish fillets collected during 2014. The highest geosmin and MIB concentrations detected in split‐pond water during the study were 898 and 22,651 ng/L, respectively. Geosmin and MIB concentrations in split‐pond water were often higher in summer and autumn, and concentrations were similar to those reported previously for conventional ponds. The highest geosmin and MIB concentrations detected in fillets during the study were 1,712 and 29,851 ng/kg, respectively. Concentrations of these compounds in fillets and the description and intensities determined via sensory analysis were similar to those reported previously for off‐flavor catfish from conventional ponds. Accordingly, catfish farmers using split‐ponds can use similar management approaches as those used to mitigate earthy and musty off‐flavor problems in catfish raised in conventional ponds (e.g., applications of algicides).

Effects of Climate Change on 2-Methylisoborneol Production in Two Cyanobacterial Species

2-Methylisoborneol (2-MIB) is a common off-flavor metabolite, and it has a very low odor threshold value. 2-MIB is produced by a variety of cyanobacteria and heterotrophic bacteria. In this study, Dolichospermum spiroides (Anabaena spiroides, FACHB 498) and Planktothrix sp. (FACHB 1371) were investigated. The influence of high temperature (27, 35, and 40 °C) and dissolved inorganic carbon (DIC, 18.4, 27.5, and 36.7 mg/L) on the two 2-MIB-producing cyanobacteria were simulated to study the effect of climate change on 2-MIB production. DIC had an effect on 2-MIB production by Planktothrix sp. The results showed that the highest DIC concentration (36.7 mg/L) led to the fastest algal growth, which increased 2-MIB production by Planktothrix sp. However, 40 °C killed all the cyanobacteria. The higher temperature (35 °C) shortened the lifecycle of the two cyanobacteria because it moved forward their logarithmic phase compared to 27 °C. The 2-MIB-producing potential of Dolichospermum spiroides may increase at 35 °C. The Dolichospermum spiroides results showed that the fluorescence intensity and the concentration of extracellular 2-MIB were highly correlated (r2 ≥ 0.90). At 35 °C, there was a stronger correlation between extracellular dissolved organic matters’ (DOMs, fulvic acid (P3 (r2 = 0.90)), humic acid (P4 (r2 = 0.92)) and the soluble microbial metabolites’ (P5 (r2 = 0.71)) fluorescence peak intensities and 2-MIB concentration. The Dolichospermum sproides 2-MIB-producing potential was affected by extracellular humus. The Planktothrix sp. 2-MIB-producing potential declined in general over the growth period. In addition, temperature had no significant effect on the Planktothrix sp. 2-MIB-producing potential and the extracellular 2-MIB component.

Effect of light and temperature on new cyanobacteria producers for geosmin and 2-methylisoborneol

This study evaluates the effect of light intensity and temperature on the taste and odour compounds of two cyanobacteria species isolated as producers of taste and odour compounds, Phormidium retzii, which produced geosmin and Microcoleus vaginatus, which produced 2-methylisoborneol (2-MIB), both being recorded for the first time as producers of these compounds. The results revealed no relationship between the light intensity and temperature for geosmin/2-MIB production under three different levels of the light intensity (17, 33 and 50 μmol photons m−2 s−1) and temperature (10, 25 and 33 °C). Higher concentrations of total geosmin (96.6 ng L−1) and 2-MIB (135.8 ng L−1) were observed at 17 μmol photons m−2 s−1 and 25 °C. Geosmin and 2-MIB were retained intracellularly during the lag phase and the highest amount of intracellular geosmin and 2-MIB occurred in the late exponential phase, whereas the extracellular geosmin and 2-MIB were released during the stationary and death phase.

Predicting In Situ Responses of Taste- and Odor-Producing Algae in a Southeastern US Reservoir to a Sodium Carbonate Peroxyhydrate Algaecide Using a Laboratory Exposure-Response Model

Efficacy of an in situ algaecide treatment can be predicted prior to an application by physically modeling exposures and responses with laboratory experiments. A sodium carbonate peroxyhydrate (SCP) algaecide was used in a drinking water reservoir (Hartwell Lake, Anderson, SC) to control a benthic algal assemblage putatively producing 2-methylisoboreol (MIB) and geosmin, compounds with adverse taste and odor attributes. These SCP applications provided an opportunity to test hypotheses regarding potential convergence of laboratory and in situ exposures and responses. Objectives of this study were to (1) measure responses of a benthic algal assemblage from Hartwell Lake to 7-day laboratory exposures of SCP [measured as hydrogen peroxide (H2O2) concentrations], (2) to measure the exposure of SCP (as H2O2) applied in a cove of Hartwell Lake and consequent responses of the algal assemblage, and (3) compare exposures and responses measured in the laboratory and in situ. Results demonstrated that in laboratory exposures, H2O2 released by SCP dissipated within 48 h. Significant responses of the algal assemblage in terms of phycocyanin concentrations and cell densities were measured 4 days after treatment (4-DAT) and 7-DAT following exposures of 453, 615, and 812 mg H2O2 m−2. The H2O2 exposure measured in situ was comparable to effective laboratory exposures in terms of initial exposure (619 ± 428 mg H2O2 m−2) and exposure duration (dissipation within 30 h), but the in situ exposure had a large deviation initially (i.e., ±428 mg H2O2 m−2) and was an order of magnitude less than the targeted initial exposure. Therefore, comparison of measured responses was critical to infer comparable exposures and confirm accuracy of the laboratory model. Significant in situ responses were measured 4-DAT and 7-DAT in terms of phycocyanin concentrations and cell densities, and were comparable to responses obtained from effective laboratory exposures (i.e., 453, 615, and 812 mg H2O2 m−2). Decreases in measured concentrations of MIB and geosmin at the intake of the drinking water treatment facility provided additional evidence that algae were sufficiently exposed to H2O2 from SCP. Results of this experiment provide evidence for the design and use of physical laboratory models to predict responses of algae in the field.

Oxidation of geosmin and 2-methylisoborneol by the photo-Fenton process: Kinetics, degradation intermediates, and the removal of microcystin-LR and trihalomethane from Nak-Dong River water, South Korea

Due to the increased intensity and frequency of cyanobacterial blooms, taste and odor (T&O) causing compounds, geosmin (GSM) and 2-methylisoborneol (MIB), have become a cause for great concern in drinking water treatment plants (DWTPs). Advanced oxidation processes (AOPs) have been studied for the removal of GSM and MIB. However, in this work, a photo-Fenton treatment was investigated for the first time for the degradation of GSM and MIB in both synthetic and Nak-Dong River water from DWTPs. Synthetic water-based experiments were performed to investigate the optimal operation conditions for the removal of GSM and MIB, and the effects of water quality parameters of the photo-Fenton process, including the Fe(II)/H2O2 concentration, reaction time, pH, organic matter, and initial concentration of GSM and MIB. Degradation intermediates of dehydration and ring-opening were observed during the photo-Fenton process. The optimal conditions were determined to be 2mg/L Fe(II) and 20mg/L H2O2 at pH 5 considering both efficiency and cost. The degradation efficiency was lower than that of DI water, mainly because of the pH (7.2–7.6). Nevertheless, the photo-Fenton process meets the guideline levels (20ng/L) in South Korea when the initial concentration in the river water is below 50ng/L. In addition, trihalomethanes (THMs) and microcystin-LR (MC-LR), derived from cyanobacterial blooms and another cause for concern, were degraded effectively using the photo-Fenton process on the river water.

Unexpected impact of 2-methylisoborneol as off-odour substance in aged wines.

Four Pinot noir wines from Burgundy were investigated by gas chromatography-olfactometry, with regard to the presence of earthy-smelling compounds. 2-Methylisoborneol (2-MIB) was detected in two of these wines, although the samples were seven years old, contradicting previous reports that this substance is unstable in wine and must. In order to investigate this seemingly paradoxical situation, 2-MIB stability was reinvestigated in wine and in model solution starting with an elevated initial concentration. Although 2-MIB concentration greatly decreased during the 90days of storage, the final concentration measured in both media was well above the odour threshold of the substance. Based on the observation of a decelerating decrease of 2-MIB with time, it was concluded that this substance can still be detected in wine and can induce, in this case, an earthy off-odour on condition that the start concentration is high enough.

Experimental validation of a time-dependent model for chemical taste taint accumulation as geosmin (GSM) and 2-methylisoborneol (MIB) in commercial RAS farmed barramundi (Lates calcarifer)

The accumulation of naturally-derived taste taint chemicals, geosmin (GSM) and 2-methylisoborneol (MIB), impair the flavour of Recirculating Aquaculture System (RAS) farmed-fish. Quantification and control of these by analytical or sensory means are not presently practical for RAS farmers. To forecast taste taint in RAS, a time-dependent model was synthesised (Ecological Modelling 291 (2014) 242–249). Here we report for the first time an extensive two-year validation study of this model with commercial RAS farmed barramundi (Lates calcarifer) in which fingerlings (∼0.01kg) were grown to harvest (∼0.85kg) at 245days. The concentration of GSM and MIB in the growth water and fish-flesh was determined (weekly) using Headspace Solid-Phase Micro-Extraction, followed by Gas Chromatography Mass-Spectroscopy (and microwave-mediated distillation). The concentration of both taint chemicals in the RAS growth water was controlled using continuous dosing of hydrogen peroxide (2.5mgL−1) as a benign biocide. A special dosing apparatus was developed for this purpose. Results showed, generally, very good agreement between observed and predicted taint values in the range 0–2μgkg−1, and especially below the important consumer rejection threshold (<∼0.7μgkg−1). A minor anomaly was a general over-prediction of chemical in about a half of the N=706 simulations in the range 0–12μgkg−1. Predictions were conservative therefore i.e. on the ‘safe’ side. This is attributed, largely, to dissimilar (exponential) growth constant (γ) for smaller and larger fish, and the fact that the RAS environment is oscillatory. Findings highlight that the work could be meaningfully applied to RAS systems to develop protocols to limit taste taint in harvested fish. Significantly, these results are the first for RAS farmed-fish covering an entire production cycle from fingerlings to harvest. The work will be of immediate benefit and interest to RAS farmers, selling agents and researchers.

An alternative method to quantify 2-MIB producing cyanobacteria in drinking water reservoirs: Method development and field applications

2-Methylisoborneol (2-MIB) is a commonly detected cyanobacterial odorant in drinking water sources in many countries. To provide safe and high-quality water, development of a monitoring method for the detection of 2-MIB-synthesis (mibC) genes is very important. In this study, new primers MIBS02F/R intended specifically for the mibC gene were developed and tested. Experimental results show that the MIBS02F/R primer set was able to capture 13 2-MIB producing cyanobacterial strains grown in the laboratory, and to effectively amplify the targeted DNA region from 17 2-MIB-producing cyanobacterial strains listed in the literature. The primers were further coupled with a TaqMan probe to detect 2-MIB producers in 29 drinking water reservoirs (DWRs). The results showed statistically significant correlations between mibC genes and 2-MIB concentrations for the data from each reservoir (R2=0.413–0.998; p<0.05), from all reservoirs in each of the three islands (R2=0.302–0.796; p<0.01), and from all data of the three islands (R2=0.473–0.479; p<0.01). The results demonstrate that the real-time PCR can be an alternative method to provide information to managers of reservoirs and water utilities facing 2-MIB-related incidents.

Effects of Inoculated Bacillus subtilis on Geosmin and 2-Methylisoborneol Removal in Suspended Growth Reactors Using Aquacultural Waste for Biofloc Production.

Geosmin and 2-methylisoborneol (2-MIB) are two of the most common taint compounds that adversely affect the quality of aquacultural animals. In the present study, 94% of geosmin and 97% of 2-MIB in suspended growth reactors producing bioflocs (SGRs) with aquaculture waste were removed after inoculation with Bacillus subtilis, significantly higher than that of control SGRs (70% of geosmin and 86.4% of 2-MIB). The lowest concentrations of geosmin and 2-MIB achieved in the effluent of the SGRs were 2.43 ± 0.42 ng/l and 2.23 ± 0.15 ng/l, respectively. The crude protein content of the bioflocs produced in the SGRs was 35 ± 4%. The NH4(+)-N and NO2(-)-N concentrations in the effluent of the reactors were 1.13 ± 0.21 mg/l and 0.42 ± 0.04 mg/l, respectively. These results suggest that inoculated with Bacillus subtilis, SGRs have a better performance to reuse the nitrogen in fish waste and to remove geosmin and 2-MIB from the culture water efficiently.

Occurrence and Emergency Response of 2‐Methylisoborneol and Geosmin in a Large Shallow Drinking Water Reservoir

Taste and odor causing compounds (TOCCs) especially 2‐methylisoborneol (MIB) and geosmin (GSM) should be eliminated because of increasing complaints of undesirable musty and earthy odor in drinking water. Spatial and temporal distributions of MIB and GSM in a large shallow drinking water reservoir were investigated since its first filling. The results showed that the GSM concentration was &lt;15 ng/L and its potential to cause a taste and odor event was small. The concentrations of MIB in the transition zone were higher than in the riverine and the lacustrine zones of the reservoir and could reach 330 ng/L during warmer seasons, which was an alarm for taste and odor events. Emergency response practices showed that (i) powdered activated carbon was effective in removing MIB while the raw water was flowing through the pipes to the drinking water treatment plants (DWTPs); (ii) the ozone‐biological activated carbon process was effective in removing MIB in DWTPs; and (iii) the combination of these two technologies could ensure that the MIB content in treated water stayed below the olfactory threshold concentration even when its concentration in the reservoir was &gt;300 ng/L. Continuous monitoring of TOCCs not only provides water quality information to the reservoir operators but also shows the development of TOCCs, which would help researchers and engineers to find effective ways preventing the occurrence of TOCCs in drinking water.

퇴적층의 온도별 배양에 따른 조류군집 형성과 이취미물질 발생 특성

We analyzed the formation of phytoplankton community and the occurences of odorus compound from benthic cyanobacteria in North, South Han-River, Paldang-Lake and Kyeongan-Stream sediments. Sediments were incubated in different water temperature. Akinetes were found (0~500 cells/g) with the highest number on sediment in Yangsoo railroad bridge (YC). The result showed that Anabaena ranged between in Sambong (SB), YC, Mukhyen-Stream (MS), Paldang-Lake (P2) and Kyeongan-Stream (KK). The total 68 taxa of phytoplankton were observed during the incubation period. A standing crop of phytoplankton was in the range of and Microcystis appeared in SB, YC, P2 and KK sites with temperature. In South Han-River (P3), Oscillatoria tenuis was dominant at temperature. The concentration of geosmin was the highest in SB- (25.5 ng/L), and the concentration of 2-MIB was the highest in P3- (286.8 ng/L). Odorous compounds were detected in all the temperature conditions from each site. Our results indicate that the dominant benthic cyanobacteria (O. tenuis, O. limosa, Phormidium tenue and Pseudanabaena limnetica) have high correlation with the occurrence odorous compounds and 2-MIB.

Off-flavour compounds in common carp (Cyprinus carpio L.) flesh in context of type of fish pond

The aim of our study was to survey the geosmin (GSM) and 2-methylisoborneol (MIB) concentrations of the sediment and that of common carp (Cyprinus carpio) flesh in three different Hungarian fish farms (clayey, marshy, and sodic ponds). Results showed that the concentrations of off-flavour compounds of the sediment and fish fillets were related to the natural environment. The GSM concentration of bottom soil samples was higher, than MIB in each fish farm. Both off-flavour compounds were the highest in the marshy fish pond and the lowest in the sodic pond. In case of fish flesh, significant differences were found between the farms in GSM level and fat content. In the fish flesh the same tendency was found as in the sediments, but surprisingly, MIB concentration was higher in the fillets, referring to accumulation.

미량오염물질 및 맛 냄새유발물질의 제거를 위한 오존/AOP 및 활성탄 공정의 적용성에 관한 연구

This study was conducted to assess the removal characteristics of taste and odor causing compounds(2-MIB and geosmin) and micro organic matters. GAC and BAC process consisting of Ozone/AOP and activated carbon was applied. As a result, the influent concentration of 2-MIB 159 ng/L and geosmin 371 ng/L were removed 42% and 86% by ozone 1.0 mg/L, and 58%, 90% by AOP(ozone 1.0 mg/L + H2O2 0.5 mg/L). Also it showed less than 2 ng/L effluent in GAC process and 99.8% removal efficiency in BAC process. Therefore, BAC process combining ozone/AOP and GAC is effective for persistent removal of micro organic matters, taste and odor. It is needed for optimization of Ozone/AOP process according to influent concentrations.

Occurrence of algae and algae-related taste and odour (T&amp;O) compounds in the Qingcaosha Reservoir, China

This study examined the temporal and spatial variations in the occurrence of major algae and algae-related taste and odour (T&O) compounds in Qingcaosha Reservoir, China. Water samples were collected monthly from seven sites in the reservoir and analysed using solid phase microextraction combined with gas chromatography-mass spectrometry. Results showed that green algae were dominant over the 9-month study. In addition, cyanobacteria in the summer and early autumn peaked at 3.2 ∼ 9.6 × 106 cell/L. Among the four most common algae-related T&O compounds, dimethyl trisulphide was undetectable at any of the sampling sites, and 2-methylisoborneol (2-MIB), geosmin and β -cyclocitral were frequently over their respective odour threshold levels from August through October. β -cyclocitral concentration was linearly correlated with the concentration of cyanobacteria ( R 2 = 0.9831). The peak β -cyclocitral concentrations varied from 452 to 1,293 ng/L and were observed close to the water table. In contrast, high concentrations of 2-MIB and geosmin occurred in the water overlying sediments, probably because some of the 2-MIB and geosmin came from the micro-organisms in the sediments. These results provide important information regarding algae and algae-related T&O compounds in a typical reservoir in estuary and coastal areas, and will be helpful for developing appropriate strategies to minimize undesirable T&O issues in water sources.

Stimulation of 2-methylisoborneol (MIB) production by actinomycetes after cyclic chlorination in drinking water distribution systems

The impact of fluctuation in chlorine residual on actinomycetes and the production of 2-methylisoborneol (MIB) were studied in cast-iron and PVC model distribution systems. Actinomycetes were spiked in each system and continued operation for a 12-day non-chlorine experiment, resulting in no changes in actinomycetes and MIB concentrations. Three cyclic chlorination events were performed and chlorine residuals were maintained as follows: 1.0 mg L−1 for 24 h, 0 mg L−1 for 48 h, 0.5 mg L−1 for 48 h, 0 mg L−1 for 48 h and 2 mg L−1 for 24 h. After each chlorination event, 2 -3 log decrease in actinomycetes was noted in both systems. However, within 48 h at 0 mg L−1 chlorine, the actinomycetes recovered to the pre-chlorination levels. On the contrary, MIB concentration in both systems remained un-impacted after the first cycle and increased by fourfold (< 5 to > 20 mg L−1) after the second cycle, which lasted through the third cycle despite the fact that actinomycetes numbers fluctuated 2–3 logs during this time period. For obtaining biofilm samples from field, water meters were collected from municipality drinking water distribution systems located in central Arizona. The actinomycetes concentration in asbestos cement pipe and cast iron pipe averaged 3.1 × 103 and 1.9 × 104 CFU cm−2, respectively. The study shows that production of MIB is associated with changes in chlorine residual in the systems. This is the first report of cyclic chlorine shock as a stimulus for MIB production by actinomycetes in drinking water distribution system's ecology.

Establishment and field applications of real-time PCR methods for the quantification of potential MIB-producing cyanobacteria in aquatic systems

2-Methylisoborneol (MIB), along with geosmin, has been frequently associated with taste and odor (T&O) events in waters, and cyanobacterial species were considered the main producers in freshwater ecosystems. The detection and quantification of genes responsible for the synthesis of these odors on-site could be valuable for the prediction and treatment of T&O. In this study, SYBR Green and TaqMan real-time quantitative polymerase chain reaction (qPCR) assays were established on the basis of conserved regions in cyanobacterial MIB cyclase gene (mic) and applied to the quantification of potential MIB-producing cyanobacteria in waters. These two qPCR assays showed the prescribed values of amplification efficiency (0.976 and 1.023, respectively) with linearity (R (2) > 0.99) in the range of 10(1) to 10(7) mic copies. Examination on environmental samples and cyanobacterial cultures indicated that qPCRs were rarely inhibited by background biomass, and the limit of quantification was at the level of 10(3) mic copies L-1 in natural waters. The seasonal variations of mic abundances in Lushui Reservoir, Donghu Lake, and Qinghai Lake of China were successfully quantified using the two qPCR protocols and indicated the applicability of these assays in field monitoring. Regression analysis revealed the positive correlation between mic abundance and MIB concentration, but no significant linear correlation was found between MIB-producing cyanobacteria and total cyanobacteria in investigated waters. The qPCR assays developed in this study could rapidly and reliably detect and quantify the abundance of potential cyanobacterial MIB producers, thereby providing a valuable tool for the prediction and early detection of T&O events.

Taste and odour and public perceptions: what do our customers really think about their drinking water?

Customers primarily perceive the safety of drinking water on aesthetic qualities. Chlorine, geosmin and 2-methylisoborneol (2-MIB) are common causes of taste and odour complaints in Australia. Variance in customer preference, perception, cultural differences and individual experiences make regulation of these, in the form of guidelines, challenging to establish. Here, analysis of historical water quality and customer complaint data showed the use of customer complaints as an indicator of deteriorating water quality is not robust. The use of a modified Flavour Ratings Assessment showed a statistical decrease in customer acceptance from control samples when chlorine concentration in drinking water increased above 0.2 mg/L and when geosmin or 2-MIB concentration was greater than 10 ng/L. However, geosmin was only rated ‘unacceptable’ at 30 ng/L while chlorine and 2-MIB were not rated ‘unacceptable’ for the range tested. For all samples, including ‘blanks', customers indicated a greater tendency to complain in a social setting rather than formally to their water provider.