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Finding the right lure for trapping pest insects is difficult. The typical smell of rain and humid soil, geosmin, now turns out to be a strong attractant for the yellow fever mosquito Aedes aegypti.

Disgusting fishy odor problems have become a major concern in drinking water quality, and are commonly related to algal proliferation in source water. Unlike the typical musty/earthy odorants 2-methylisoborneol (MIB) and geosmin, identification of the corresponding fishy odorants is still a big challenge. In this study, two species of fishy-odor-producing algae, Ochromonas sp. and Cryptomonas ovate, were cultured to explore the odor production characteristics and typical odorants. When algae were ruptured in the stationary and decline phases, fishy odor intensities of 4 to 8 characterized by FPA were produced. However, some frequently reported aldehydes that could cause fishy odor, including n-hexanal, 2-octenal, heptanal, 2,4-heptanal and 2,4-decadienal, were not detected in either of the cultured algae. The possible fishy odor-causing compounds were further identified by combining gas chromatography-olfactometry (GC-O/MS) and comprehensive two-dimensional gas chromatography (GC × GC-TOFMS) using retention indices (RIs). From GC-O/MS analysis, twelve and six olfactometry peaks with various odor characteristics were identified in Ochromonas sp. and Cryptomonas ovate, respectively, of which three and two olfactometry peaks showed fishy odor characteristics. 2-Nonenal, 2,4-octadienal, fluorene and 2-tetradecanone were identified as fishy odorants in Ochromonas sp., and 1-octen-3-ol, 6-methyl-5-hepten-2-one, 1-octen-3-one, 2-nonenal and 2,4-octadienal were identified in Cryptomonas ovate. Other identified compounds, including butyl butanoate (fragrant odor), ionone (fragrant odor), bis (2-chloroisopropyl) ether (chemical odor) etc., did not show fishy features. Therefore, the fishy odor might be a synthetic and comprehensive odor, which resulted from the combination of different odorants and their synergistic effects. The results of this study will be helpful for understanding fishy odor problems, which will provide support for fishy odor management and control in the drinking water industry.

In recirculating aquaculture systems (RAS)s, off-flavors and odors, mainly caused by geosmin (GSM) and 2-methylisoborneol (MIB), can accumulate in the flesh of fish from RAS water, reducing the profitability of production. In this study, peracetic acid (PAA) was applied in three application intervals to pump sumps of rainbow trout (Oncorhynchus mykiss) reared in RAS. Using a real-time polymerase chain reaction (qPCR), the potential off-flavor producers were quantified using geoA and MIB synthase genes. Streptomyces was identified as the major GSM producer, and biofilters showed the highest number of potential off-flavor producers. Concentrations of GSM and MIB were analyzed in the circulating water and in the lateral part of the fish fillet. In water, concentrations up to 51 ng L−1 (GSM) and 60.3 ng L−1 (MIB) were found, while in the fillet, these were up to 9.8 ng g−1 (GSM) and 10.2 ng g−1 (MIB), decreasing with increasing number of PAA applications. PAA applications reduced the levels of off-flavor compounds, although this was insufficient to fully prevent the accumulation of GSM and MIB.

Given tilapia grown in the biofloc technology production system can consume the biofloc, it should be possible to optimize formulated diet protein content to account for nutrition derived from consuming biofloc. The present study, conducted in an outdoor biofloc technology production system, evaluated impacts on fish production indices, common microbial off-flavors, and water quality dynamics for hybrid tilapia (Oreochromis aureus × O. niloticus) fed diets formulated to contain 22.5%, 27.7%, and 32.3% digestible protein (DP) and 6% lipid. Fingerlings (32.2 ± 10.1 g/fish) were stocked in tanks (18.6 m2; 16.6 m3) in May 2016 at 25/m2 (29/m3) and grown for 5 months to market size. At harvest, fish fed the 22.5% DP diet were significantly smaller (518 g/fish) and had significantly higher feed conversion (1.5) than those fed the higher DP diets (553–564 g/fish and 1.4, respectively). Feed nitrogen input and nitrification rate increased linearly with increased DP. Results of this study suggest that by using ideal protein theory to formulate diets supplemented with the first four limiting amino acids (Lys, Met, Thr, Ile) digestible protein can be reduced from 32.3% to 27.7% without adversely affecting hybrid tilapia productivity indices. Market size distributions, nutrient retention, 2-methylisoborneol and geosmin off-flavors, and pond water quality dynamics in relation to diet DP also are discussed.

Geosmin (GSM) and 2-methylisoborneol (MIB) are secondary metabolites of cyanobacteria that are often present in recirculating aquaculture systems (RAS) and are problematic, even at low (ng L−1) concentrations, due to their taste and odor effects on water and accumulation in the lipid tissue of fish. Removal of these compounds is difficult due to their extremely low concentrations and advanced treatment technologies, such as advanced oxidation processes (AOPs) have to be employed. In this study, a novel AOP consisting of immobilized TiO2 in a UV reactor was tested at bench scale for removal of GSM and MIB in both batch and continuous flow modes. Batch reactor application at a full-scale RAS resulted in average GSM and MIB removal efficiencies of 61% and 72%, respectively, with a 6 h treatment time. No significant removal of GSM and MIB was observed in continuous flow mode, most likely due to both lower residence time and low initial concentrations of both compounds. No negative effects were observed on downstream biological wastewater treatment processes, indicating that the proposed UV-TiO2 process can be safely integrated into RAS.

Peracetic acid (PAA) is an effective disinfectant/sanitizer for certain industrial applications. PAA has been described as a powerful oxidant capable of producing water quality benefits comparable to those expected with ozone application; however, the water oxidizing capacity of PAA in aquaculture systems and its effects on fish production require further investigation, particularly within recirculation aquaculture systems (RAS). To this end, a trial was conducted using six replicated RAS; three operated with semi-continuous PAA dosing and three without PAA addition, while culturing rainbow trout Oncorhynchus mykiss. Three target PAA doses (0.05, 0.10, and 0.30 mg/L) were evaluated at approximately monthly intervals. A water recycle rate >99% was maintained and system hydraulic retention time averaged 2.7 days. Rainbow trout performance metrics including growth, survival, and feed conversion ratio were not affected by PAA dosing. Water quality was unaffected by PAA for most tested parameters. Oxidative reduction potential increased directly with PAA dose and was greater (P < 0.05) in RAS where PAA was added, indicating the potential for ORP to monitor PAA residuals. True color was lower (P < 0.05) in RAS with target PAA concentrations of 0.10 and 0.30 mg/L. Off-flavor (geosmin and 2-methylisoborneol) levels in culture water, biofilm, and trout fillets were not affected by PAA dosing under the conditions of this study. Overall, semi-continuous PAA dosing from 0.05-0.30 mg/L was compatible with rainbow trout performance and RAS operation, but did not create water quality improvements like those expected when applying low-dose ozone.

Revealing the main contributors to septic odor is a challenge since diverse compounds are responsible for this odor, and there might exist synergistic effects among different odorants. In this study, based on a reconstitution evaluation, the contribution of eighteen odorants identified in Huangpu River source water to the septic odor was explored. The reconstitution test result showed that the three typical odorants, including bis(2‑chloroisopropyl) ether (BCIE), diethyl disulfide (DEDS) and dimethyl disulfide (DMDS), with respective average odor activity values (OAVs) of 2.35, 1.65 and 0.78, only contributed 61 ± 3% of the FPA intensity for septic odor in Huangpu source water. At a BCIE concentration of 50 ng/L, synergistic effect for the septic odor occurred at 10 ng/L for geosmin and 20 ng/L for 2‑methylisoborneol (MIB), showing that coexisting musty odorants could enhance the septic odor intensity caused by some typical odorants. When both geosmin and MIB, with an average OAV of 4.54 and 1.38, were further included in addition to the three typical odorants, 88 ± 4% of the septic odor in Huangpu River source water could be explained. With addition of the remaining odorants with much lower OAVs (0.23), 94 ± 2% of the septic odor could be explained. The musty odor was not affected by the presence of the co-existing odorants at the concentration levels of the present study. This study indicated that the overall odor of water contaminated with musty and septic odorants is a combination of both concentrations of individual contaminants and their synergistic effects. This is the first study to reveal the synergistic effects of typical musty odorants on septic odor, and the results of this study demonstrated that the synergistic effects of other odorants should be considered when dealing with the septic odor in drinking water.

Taste and odor (T&O) compounds are widespread in water environments and have attracted considerable public attention. Nowadays, the standard detections of these chemicals rely mainly on off-line methods such as GC-MS or evaluation by trained analysts' senses. In this study, we report a method for the rapid detection of T&O compounds in water by exploiting a newly invented chemi-ionization source, in combination with headspace vapor measurement at room temperature. The calibrated limits of detection (LODs) of 2-methylbutyraldehyde, methyl tert-butyl ether (MTBE), methyl methacrylate (MMA), 2-isobutyl-3-methyoxypyrazine (IBMP), and 2-isopropyl-3-methoxypyrazine (IPMP) are in the range of 3.5–50.2 ng L−1, and the estimated LODs of 2-methylisoborneol (2-MIB) and geosmin (GSM) are 0.25 and 0.77 ng L−1, respectively. The calibration results reveal that the instrumental LODs for 2-methylbutyraldehyde, MTBE, MMA, β-cyclocitral, 2-MIB, and GSM are 1–2 orders of magnitude better than the odor thresholds of humans. The accuracy, precision, recovery, and linearity (R2) of the method are tested. Water samples from city tap water and three rivers in Beijing are assessed using this technique, and the typical T&O compositions are observed with concentrations ranging from 0.2 to 297 ng L−1. The new ultra-sensitive rapid detection method shows comparable sensitivities to the existing off-line technique and displays great potential for real-time detection of T&O pollution in water environments.

Geosmin (GSM) and 2-methylisoborneol (2-MIB) are two common odor compounds in drinking water. In this paper, the performance of UV/chlorine was compared with that of chlorine and UV to degrade GSM (100 ng L−1) and 2-MIB (100 ng L−1) in water. UV/chlorine was further exploited, and a steady-state kinetic model was used to conduct a detailed study on efficiency, rate, reactive species and pathway. The results showed that UV/chlorine greatly could improve the removal ratio to 90% within 5 min, from approximately 20% with only UV or dark chlorine in 60 min. The removal ratio and rate depended on UV light intensity, free chlorine dosage, reaction time and water quality parameters (e.g. pH, concentrations of HCO3− and Cl−). Among these factors, the first two obviously could accelerate the rate and increase the ratio. The degradation was also significantly improved in an acidic condition, while alkaline conditions and HCO3− had inhibitory effects, and Cl− created no difference. Contributions of OH and Cl to the degradation of 2-MIB and GSM were further revealed, and OH was found to be the most important reactive species. In the UV/chlorine process, 6 degradation byproducts of 2-MIB, including 1 alcohol, 2 ketones, and 3 olefins, were identified, and 14 degradation byproducts of GSM, including 6 ketones, 1 aldehyde, 2 alcohols, 3 naphthenes, and 2 olefins, were found by using solid-phase microextraction coupled to gas chromatography-mass spectrometry. The possible degradation pathways of GSM and 2-MIB in UV/chlorine thus were proposed.

While cyanobacteria have been widely recognised as the most common cause of geosmin and 2-methylisoborneol related taste and odour (TO) episodes in drinking water supplies, many reported occurrences could not be attributed to these organisms. The Streptomyces genus of soil bacteria also includes producers of these compounds, however their potential role in such occurrences is poorly understood and often disregarded on the basis that they are terrestrial rather than aquatic organisms, with their detection in water samples assumed to reflect the presence of dormant spores rather than metabolically active vegetative cells. Using qPCR and a differential cell lysis technique for DNA extraction, allowing distinction of spores from vegetative cells, the aim of this study was to determine the distribution, abundance and potential activity of Streptomyces species across a range of aquatic and marginal habitat zones in two drinking water reservoirs, including: exposed soil, submerged sediments, plant debris and emergent macrophytes at the margins; marginal and offshore surface waters; deep offshore waters; and offshore benthic sediments. Marginal substrates including soil, sediment and plant debris were identified as the dominant habitat zones for Streptomyces, (concentrations up to 1.1 × 10

The accumulation of geosmin and 2-methylisoborneol in culture water and fish is a common problem encountered in recirculating aquaculture systems (RAS). In these systems, like in other aquaculture systems, abatement of this problem is usually conducted by purging the fish with clean water prior to their marketing. In indoor RAS, mainly heterotrophic prokaryotes underlie the production of geosmin and MIB. While production of these off flavor compounds has been linked with the organic-rich parts of these systems, no further information on factors that promote the growth of the geosmin and MIB-producing microorganisms under these conditions is currently available. Thus far, geosmin and MIB removal from RAS has mainly been conducted by ozonation, albeit with limited success. Biodegradation of geosmin and MIB might serve as an additional method for removal of these compounds from RAS. Geosmin and MIB degradation has been detected in the latter systems, yet factors which promote the activity of geosmin and MIB degraders in these systems remain largely unknown. In the present review, the current knowledge on geosmin and MIB production and removal in RAS is presented. Emphasis is placed on the biodegradation of these off-flavor compounds, a process which has received little attention thus far.

This study evaluated a long-term impact of biological activated carbon (BAC) filter that was employed in a full-scale drinking water treatment plant to enhance the removal of contaminants by the ultrafiltration (UF) process. The results showed that BAC enhanced UF performance by increasing the flux by 18.5% and extending the filtration run by 45%. The presence of BAC improved the removal of primary contaminants, including dissolved organic carbon (4–40%), UV254 (10–57.7%), geosmin and 2-methylisoborneol (80%). BAC was also effective in decreasing the concentration of biopolymers, humic substances, (semi-)volatile organics, chlorite and halonitromethanes, thereby lowering contaminant load on the UF unit. The changes in primary water quality parameters in the combined process showed that the humic substances in dissolved organic nitrogen, low molecular weight substances in UV254, and fluorescence protein-like substances could be useful indicators for DBPs as these organic fractions had strong correlation with DBPs. Obvious spatio-temporal characteristics of GAC grain and microbial communities in BAC filter were observed with operation time and filter depth. The bacterial community in BAC filter was highly diverse and was less influenced by influent quality with an increase in filter depth, while the communities in UF cake layer correlated with organic removal in the UF system.

Vetiveryl acetate is a common ingredient of the perfume industry highly prized by perfumers for its crisp vetiver note and thus often used in high-end perfume compositions. Vetiveryl acetate is currently manufactured from vetiver oil by means of various industrial processes that result in the conversion of the main vetiver alcohols into their corresponding acetates. Despite being used for decades as perfume ingredient, vetiveryl acetate has barely been studied in the past, therefore its chemical composition is poorly documented. While vetiveryl acetate is currently under investigation by regulation authorities, it was crucial to fill this gap of knowledge. We report here the first detailed investigation of different types of vetiveryl acetates, covering analytical, regulatory, and olfactory aspects. This study is based upon an integrated analytical methodology involving a full array of gas chromatographic techniques and spectroscopic/spectrometric methods. The principal objective was the identification of the main ester constituents contained in different samples of vetiveryl acetate, as well as linking their chemical composition with their manufacture process. Among the major esters detected in all samples, 23 ester constituents were either isolated by capillary preparative-gas chromatography or synthesized in order to provide their complete spectral characterization. The quantification of constituents in both commercial and laboratory-made vetiveryl acetates was carried out by internal calibration using comprehensive two-dimensional-gas chromatography and predicted relative response factors. The generated set of analytical data permitted to explore both the regulatory aspects and the olfactory properties associated with the substance. The manufacture of vetiveryl acetate modulates the initial scent of vetiver essential oil by suppressing the notes brought by the main fragrant alcohols. While the impact of undesired odorant molecules such as phenol derivatives and geosmin is lowered, the major odour-active ketones such as khusimone, ziza-6(13)-en-3-ones, and the two vetivones develop their own odor characters in vetiveryl acetate.

The potential of ferrate(VI) to oxidize algal-derived taste and odor (T&O) compounds during water treatment was assessed by investigating the reaction kinetics of ferrate(VI) with selected T&O compounds. Apparent second-order rate constants (kapp) were determined in phosphate buffered waters in the pH range of 6–9. The olefinic T&O compounds show an appreciable reactivity to ferrate(VI): kapp = 34–639 M−1 s−1 at pH 7. The non-olefinic T&O compounds such as geosmin and 2-methylisoborneol show negligible reactivity to ferrate(VI) (kapp

Common off-flavor compounds, including geosmin (GSM) and 2-methylisoborneol (MIB), bioaccumulate in Atlantic salmon Salmo salar cultured in recirculating aquaculture systems (RAS) resulting in earthy and musty taints that are unacceptable to consumers. To remediate off-flavor from market-ready salmon, RAS facilities generally relocate fish to separate finishing systems where feed is withheld and makeup water with very low to nondetectable GSM and MIB levels is rapidly exchanged, a process known as depuration. Several procedural aspects that affect salmon metabolism and the associated rate of off-flavor elimination, however, have not been fully evaluated. To this end, a study was carried out to assess the effects of swimming speed and dissolved oxygen (DO) concentration on GSM levels in water and fish flesh during a 10-day depuration period. Atlantic salmon (5–8 kg) originally cultured in a semi-commercial-scale RAS (150 m3 tank) were exposed to a concentrated GSM bath before being transferred to 12 replicated partial reuse depuration systems (5.4 m3 total volume). Two swimming speeds (0.3 and 0.6 body lengths/sec) and two DO levels (90% and 100% O2 saturation) were applied using a 2 × 2 factorial design (N = 3), and each system was operated with a 5-h hydraulic retention time, creating a water flushing to biomass ratio of 151 L/kg fish biomass/day. Geosmin was assessed at Days 0, 3, 6, and 10 in system water and salmon flesh. A borderline effect (P = 0.064; 0.068) of swimming speed was measured for water and fish, respectively, at Day 3, where slightly lower GSM was associated with low swimming speed (0.3 body lengths/sec); however, differences were not detected at Days 6 or 10 when salmon are commonly removed for slaughter. Overall, this research indicates that significant improvements in GSM depuration from RAS-produced Atlantic salmon are not expected when purging with swimming speeds and DO concentrations similar to those tested during this trial.

Taste and odor (T & O) episodes always cause strong effects on drinking water supply system. Luanhe River diversion into Tianjin City in China is an important drinking water resource. Massive growth of a benthic filamentous cyanobacterium with geosmin production in the open canal caused a strong earthy odor episode in Tianjin. On the basis of the morphological and Molecular identification of this cyanobacterium as Oscillatoria limosa Agardh ex Gomont, the genetic basis for geosmin biosynthesis and factors influencing growth and geosmin production of O. limosa CHAB 7000 were studied in this work. A 2268-bp open reading frame,.encoding 755 amino acids, was amplified and characterized as the geosmin synthase gene (geo), followed by a cyclic nucleotide-binding protein gene (cob). Phylogenetic analysis implied that the evolution of the geosmin genes in O. limosa CHAB 7000 might involve a horizontal gene transfer event. Examination on the growth and geosmin production of O. limosa CHAB 7000 at different light intensities showed that the maximum geosmin production was observed at 10 mu mol photons m(-2)s(-1), while the optimum growth was at 60 mu,mol photons m(-2)s(-1). Under three temperature conditions (15 degrees C, 25 degrees C, and 35 degrees C), the maximum growth and geosmin production were observed at 25 C. Most amounts of geosmin were retained in cells during the growth phase, but high temperature and low light intensity increased the release of geosmin into the medium, implying that O. limosa CHAB 7000 had a high potential harm for the release of geosmin from its cells at these adverse conditions. (C) 2017 Elsevier B.V. All rights reserved.

We tested the hypothesis that the fate of dietary phosphorus will not differ among a dicalcium phosphate-free practical diet treated with 6-phytase (3000 FTU/kg; Quantum Blue™; P-F + Phy), and positive (C) and negative (P-F) control practical diets when fed to hybrid tilapia (Oreochromis aureus x O. niloticus; 29.8 g initial weight) stocked at 29 fish/m3 and grown for 5 months to market size (454 g/fish) in outdoor biofloc production system tanks (16.6 m3). The ideal protein diets were formulated to contain 27.7% digestible protein and 4% lipid from practical ingredients and were extruded commercially. Final weights (467–494 g), weight gains (1636-1723%), and average daily intake (2.10–2.18%) did not differ for fish fed the P-F + Phy or C diets; however, these metrics were significantly lower in the P-F diet treatment. There were fewer market size fish (46.8–54.7%), feed conversion ratios were poorer (1.59–1.61), and intraperitoneal fat contents (6.96–7.40%) were higher for fish fed the phosphorus-free diets compared to the C diet (65.3%, 1.46, 5.90%). Geosmin, as compared to 2-methylisoborneol, was considered the more relevant off-flavor compound and fillet concentrations were higher than those for 2-methylisoborneol, but concentrations present of each compound were unlikely to cause “earthy” or “musty” off-flavors. Accumulation rates of soluble reactive phosphorus, organic phosphorus, and total phosphorus in tanks fed the phosphorus-free were diets nearly half those observed for the C diet while phosphorus loading from feed was 37.7% lower.

Hydrophobic carriers were examined for geosmin and 2-methylisoborneol removal from water derived from an aquaculture system. A combination of adsorption and biodegradation was found to underlie the removal of the off-flavor compounds. Adsorption of these compounds by the carriers was unaffected by the presence of organic matter in the water to be treated. A model based on adsorption/desorption and first-order degradation kinetics provided an accurate prediction for experimentally determined 2-methylisoborneol removal rates. Steady removal of geosmin and 2-methylisoborneol as well as nitrate reduction were observed during long-term operation of the plug-flow reactors with water derived from an aquaculture facility. Metagenomic analysis of the microbial community on the carriers during long-term operation of the reactors revealed a predominance of denitrifying bacteria. It was found that geosmin and 2-methylisoborneol led to statistically significant changes in the abundances of 21 contigs that contained genes involved in terpene degradation. This study shows that at low ambient concentrations of geosmin and 2-methylisoborneol in nitrate and organic-rich water, such as found in aquaculture systems, their biodegradation can be accomplished by terpene-degrading denitrifiers that develop on hydrophobic carriers used for filtration of the contaminated water.

Highlights • A SPME and GC-MS/MS based analytical method was developed and optimized for 18 T&O compounds. • Effect of different holding times on the stability of T&O compounds was evaluated. • Preservation with acid increased the holding times of aldehydes, ketones, alcohols and esters. • Eight out of 18 T&O compounds were detected and quantified during the occurrence study with 13 drinking water utilities., Taste and odor (T&O) issues have been a major concern among drinking water utilities as source waters are becoming increasingly vulnerable to compounds released during algal blooms as well as non-algal compounds. While most of the literature focuses on the two most common T&O compounds – 2-MIB and geosmin, there are other compounds that have the potential to cause T&O events. The aim of this study was to develop an advanced analytical method using solid phase microextraction (SPME) and gas chromatography-tandem mass spectrometry (GC-MS/MS) to identify 18 T&O compounds belonging to various odor classes. The developed method was optimized for the 18 analytes and implemented to determine the holding time of the compounds in raw and treated (distribution system point-of-entry or PoE) drinking water matrices. Compounds belonging to certain classes such as pyrazines and anisoles were found to be “stable” (< 30% loss) in all tested waters for up to two weeks, while aldehydes, ketones, esters and alkyl sulfides showed > 30% loss within 96 h in raw water. Preservation of samples at low pH (< 2) using hydrochloric acid increased the holding times and reduced losses within 96 h for aldehydes, ketones and esters. The paper also discusses the occurrence of these compounds with water utilities from the Midwest and Eastern US during the summer months. The study detected eight T&O compounds - 2-MIB, geosmin, β-cyclocitral, β-ionone, hexanal, indole, dimethyl disulfide and dimethyl trisulfide. While five compounds were detected above their threshold concentrations in the raw water, two of them (2-MIB and geosmin) were detected above threshold in the PoE samples.

Elimination of black-stinking water contamination has been listed as an urgent task in the Water pollution prevention action plan promulgated by State Council of China. However, the key blackening and stinking pollutants and their sources are still unclear. In this study, water quality of a black-stinking urban river in Beijing, Dongsha River, was evaluated firstly; then the distribution of the blackening and stinking pollutants was investigated, and the key pollutants and their potential sources were identified; and finally, the health risk of those pollutants was assessed. The results showed that NH 3 N, total phosphorus, dissolved oxygen and chemical oxygen demand ranged from 1.3 to 5.3 mg/L, 0.7–3.0 mg/L, 1.0–3.2 mg/L and 29–104 mg/L, respectively. The value of TP-based trophic level index indicated that Dongsha River reached severe eutrophication level; the maximum value of chroma and odor level reached 32 and 4, respectively. The main dissolved organic compounds included aromatic protein II, soluble microbiological metabolites, fulvic acids and humic acids. The blackening pollutants Fe, Mn, Cu and S 2− were extensively detected, with significantly spatial differences along the river. Dimethyl sulfide, β-ionone, 2-methylisoborneol and geosmin were identified to be the stinking pollutants. Their concentrations covered wide ranges, and even the lowest concentration value was thousands of times higher than its olfactory threshold. Correlation analysis indicated that in the overlaying water S 2− was the key blackening pollutant, while β-ionone and geosmin were the key stinking pollutants. Principal components analysis combining with the site survey revealed their potential sources. S 2− was mainly associated with the decomposition of endogenous sulfur-containing organics; β-ionone might be generated by the endogenous β-carotene bio-conversion and the exogenous discharges, while geosmin might originate from the endogenous humus bio-conversion and anthropic wastes. Furthermore, multi-metals in the sediment posed health risks to children, while dimethyl sulfide had non-cancer health risk for adults and children.

Geosmin (GSM) and 2-methylisoborneol (2-MIB) are the most common naturally occurring taste and odor compounds in water supplies. Conventional approaches for water treatment exhibit some benefits. However, those protocols are generally ineffective for the elimination of the two compounds. In this paper, an approach on removal of GSM and 2-MIB using K2FeO4 was explored. Detailed methodology was developed. GG-MS was employed to identify the GSM and 2-MIB compounds. Further, the parameters influencing the effect of GSM and 2-MIB removal, such as pH and K2FeO4 amount were evaluated. At pH of 9, GSM and 2-MIB received its maximum value (22.5%, 31.9%). When dealing with both substances simultaneously, K2FeO4 exhibited obvious effects on MIB. More importantly, K2FeO4 can control the production rate of MIB in algae.

Nonylphenol (NP) is extensively used in agricultural, industrial and household applications. Moreover, NP is the major breakdown product of the nonionic surfactants, nonylphenol ethoxylates (NPEOs), the most widely used group of surfactants. Nonylphenol is persistent in the environment, highly toxic to aquatic organisms and is a potential endocrine disruptor. NP and NPEOs have been identified as priority hazardous substances under the Environmental Quality Standards Directive 2013/39/EU and are referred to in the list of substances of particular risk to the Baltic Sea. The toxicity of NP to the bloom-forming cyanobacterium Planktothrix agardhii 1113 isolated from the eastern Gulf of Finland, Baltic Sea and the bioremoval of NP by P . agardhii were studied. NP in concentrations > 0.4 mg L − 1 suppressed cyanobacterial growth. The median effective concentration of NP for P . agardhii after 4 days of treatment (EC 50 ) was 1.5 mg L − 1 . The removal of NP from the culture medium was primarily due to abiotic processes and biodegradation by the cyanobacterium rather than sorption by the cells. NP significantly increased the photosynthetic pigments, extracellular proteins and soluble exopolysaccharides content. The cyanobacterial growth inhibition was accompanied by the increased synthesis of microcystin dm-RR and of the odorous metabolites, geosmin and 2-methylisoborneol (MIB), by P . agardhii 1113. NP also notably increased the microcystin released into the environment. Increased levels of extracellular proteins, soluble exopolysaccharides, microcystins and odorous metabolites may affect the microbial loop in aquatic ecosystems. An increased level of malondialdehyde (MDA) was indicative of the formation of free radicals in P . agardhii under NP stress, whereas increased levels of superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH) and proline indicated the occurrence of a scavenging mechanism.

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)/H 2 O 2 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 2 mg/L Fe(II) and 20 mg/L H 2 O 2 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 (20 ng/L) in South Korea when the initial concentration in the river water is below 50 ng/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.

Ozone and biological activated carbon (BAC) are known to be effective at removing odors in drinking water. However, the specific variations in complex odors and odorants along the course of advanced treatments in full-scale drinking water treatment plants (DWTP) have remained unclear. In this paper, the migration of odors and odorants through pre-ozonation, sedimentation, post-ozonation, and BAC treatment processes were studied from January to December 2019 in a DWTP. The results indicated that septic, musty, and chemical odors with intensities of 6-6.7, 6-7.5, 4-5 could be removed by both ozonation and BAC, while grassy, fishy odors with intensities of 3.3-4.8, 2.3-5.8 could not be removed until the BAC step. Twenty-four odorants identified in raw water were classified as musty (2-methylisoborneol, geosmin), chemical (e.g. indane, eucalyptol), septic (e.g. dimethyl disulfide, pentanethiol), fishy (2,4-decadienal) and grassy (nonanal, decanal) odor compounds. It is noteworthy that eleven additional odorants were produced after ozonation; in addition, the concentrations of fishy and grassy odorants were increased after ozonation, and the concentrations of musty, septic, fishy, and grassy odorants were increased after sedimentation, suggesting that sedimentation and ozonation should be carefully managed. BAC was the most effective at removing the above odorants simultaneously. This study would be helpful for providing more insights into the migration of odorants along treatment processes and understanding the mitigation of odors in DWTPs using raw waters with complex odors.

Frequent cyanobacterial blooms in reservoirs used for human supply increase the risk of noxious secondary metabolites, endangering human health and ecological balance, and requiring constant monitoring by water companies. Although hydrogen peroxide (H2O2) has been widely reported as an effective agent for the control of cyanobacteria, being Microcystis aeruginosa one of the most studied species, very limited data is available on its effects over Dolichospermum circinale. Therefore, this study aimed to evaluate the impact of H2O2 on D. circinale and comparing it to the effects over the M. aeruginosa. The treatment was performed in cyanobacterial cultures with the application of 2 and 5 mg L−1 of H2O2 under visible light. To measure the impact of the treatment, intact cells were counted and cell re-growth monitored. Geosmin and microcystin, cell pigments, color, and organic matter in water were also analyzed during the treatment. The results showed that even the smallest H2O2 concentration (2 mg L−1) was able to completely remove D. circinale cells. Although M. aeruginosa could only be completely removed using 5 mg L−1, the few cells remaining after the application of 2 mg L−1 were not viable and did not re-grew after 15 days. Total microcystin concentration increased after M. aeruginosa was exposed to H2O2, suggesting that oxidative stress may increase the detection of this metabolite when the cells are lysed. While 2 mg L−1 was able to significantly decrease total geosmin, the addition of 5 mg L−1 did not improve removal. Chlorophyll-a was readily degraded after cell rupture but the same did not happen to phycocyanin, demonstrating its high resilience to this oxidant. Color and organic matter increased for the M. aeruginosa but decreased for the D. circinale suspension, probably because the higher concentration of the M. aeruginosa yielded more extracellular content to the water which was not able to be degraded by the amount of H2O2 applied.

Intimately coupled photocatalysis and biodegradation (ICPB) combining photocatalysis with microbial degradation is an attractive wastewater treatment technology. However, when prepared in conventional ways, the supported-photocatalysts aggregate frequently, detach easily from carriers, and prohibit the colonization of microorganisms inside the carriers. To overcome these challenges, silane coupling agent (SCA)-enhanced TiO2 coating method is developed in this study. The coupling agent γ-glycidoxypropyltrimethoxysilane (KH560) greatly enhanced the adhesion between photocatalysts and the carrier through ether and Ti-O-Si linkages. The dense TiO2 layer was firmly adhered to the carrier outer surface, and the loading amount reached 351.8±8.2 mg/g, over ten times higher than using the powder sintering method (31.5±2.4 mg/g). In the ICPB system constructed with the KH560-enhanced TiO2-supported polyurethane sponge (KH560-TiO2-PU) carriers, removal efficiencies of two model odor substances, 2-methylisoborneol (2-MIB) and geosmin (GSM), reached 88.9±0.3% and 85.0±1.0% in 12 h at an initial concentration of 500 ng/L respectively, which were 17.7±0.6% and 19.4±0.4% greater than those of the ICPB system prepared with the powder sintering method. After 5 operating cycles, the novel ICPB system remained stable with high 2-MIB and GSM removal efficiencies, reaching 89.9±0.8% and 86.1±0.2% respectively after 12h, while TiO2 peeling ratio was as low as 5.0±2.8%. Biofilms attached onto the carrier inner surface were resilient over the operating cycles with the increase of both richness and diversity of microbial communities. Analysis of biofilm microbial community and pollutant degradation pathways revealed the enhanced removal of 2-MIB and GSM in the novel ICPB system might be attributed to multiple factors. First, the alleviated aggregation and increased adhesion of photocatalysts onto carriers improved the overall photocatalysis efficiency. Second, biofilm inside of the carrier was protected and the microbial activity was well remained. Third, photocatalytic intermediate products were efficiently biodegraded by the enriched functional microbial populations, such as Thauera and Flavobacterium, with little concern of excessive oxidation. Collectively, this research provides a new technological solution that synergizes photocatalysis and biodegradation for effective removal of odorous substances in polluted natural water.

The addition of powdered activated carbon (PAC) is an effective measure to cope with seasonal taste and odor (T&O) problems caused by 2-methylisoborneol (2-MIB) and trans-1, 10-dimethyl-trans-9-decalol (geosmin) in drinking water. Some T&O problems are episodic in nature, and generally require rapid responses. This paper proposed a simplified approach for the application of the homogenous surface diffusion model (HSDM) to predict the appropriate PAC doses for the removal of 2-MIB. Equilibrium and kinetic experiments were performed for 2-MIB adsorption onto five PACs in three source waters. The simplified HSDM approach was compared with the experimental data, by assigning the Freundlich 1/n value in the range of 0.1-1.0 and obtaining the Freundlich equilibrium parameter K value through a 6-hr adsorption kinetic test. The model describes the kinetic adsorption data very well for all of the tested PACs in different source waters. The results were validated using the data obtained from one full scale water treatment plant, and the differences between the predicted and observed results were within 10% range. This simplified HSDM approach may be applied for the rapid determination of PAC doses for water treatment plants when faced with 2-MIB episodes in source waters.

Cyanobacteria are one of the principal sources of volatile organic compounds (VOCs) which cause offensive taste and odor (T&O) in drinking and recreational water, fish, shellfish and other seafood. Although non-toxic to humans, these T&O compounds severely undermine public trust in these commodities, resulting in substantial costs in treatment, and lost revenue to drinking water, aquaculture, food and beverage and tourist/hospitality industries. Mitigation and control have been hindered by the complexity of the communities and processes which produce and modify T&O events, making it difficult to source-track the major producer(s) and the factors governing VOC production and fate. Over the past decade, however, advances in bioinformatics, enzymology, and applied detection technologies have greatly enhanced our understanding of the pathways, the enzymes and the genetic coding for some of the most problematic VOCs produced by cyanobacteria. This has led to the development of tools for rapid and sensitive detection and monitoring for the VOC production at source, and provided the basis for further diagnostics of endogenous and exogenous controls. This review provides an overview of current knowledge of the major cyanobacterial VOCs, the producers, the biochemistry and the genetics and highlight the current applications and further research needs in this area. usc Refereed/Peer-reviewed

Visible light (VIS) photocatalysis has large potential as a sustainable water treatment process, however the reaction pathways and degradation processes of organic pollutants are not yet clearly defined. The presence of cyanobacteria cause water quality problems since several genera can produce potent cyanotoxins, harmful to human health. In addition, cyanobacteria produce taste and odor compounds, which pose serious aesthetic problems in drinking water. Although photocatalytic degradation of cyanotoxins and taste and odor compounds have been reported under UV-A light in the presence of TiO2, limited studies have been reported on their degradation pathways by VIS photocatalysis of these problematic compounds. The main objectives of this work were to study the VIS photocatalytic degradation process, define the reactive oxygen species (ROS) involved and elucidate the reaction mechanisms. We report carbon doped TiO2 (C-TiO2) under VIS leads to the slow degradation of cyanotoxins, microcystin-LR (MC-LR) and cylindrospermopsin (CYN), while taste and odor compounds, geosmin and 2-methylisoborneol, were not appreciably degraded. Further studies were carried-out employing several specific radical scavengers (potassium bromide, isopropyl alcohol, sodium azide, superoxide dismutase and catalase) and probes (coumarin) to assess the role of different ROS (hydroxyl radical OH, singlet oxygen (1)O2, superoxide radical anion [Formula: see text] ) in the degradation processes. Reaction pathways of MC-LR and CYN were defined through identification and monitoring of intermediates using liquid chromatography tandem mass spectrometry (LC-MS/MS) for VIS in comparison with UV-A photocatalytic treatment. The effects of scavengers and probes on the degradation process under VIS, as well as the differences in product distributions under VIS and UV-A, suggested that the main species in VIS photocatalysis is [Formula: see text] , with OH and (1)O2 playing minor roles in the degradation.

Recirculating Aquaculture System (RAS) farming of fish is becoming widespread. However, taste taint accumulation in the fish flesh as geosmin (GSM) and/or 2-methylisoborneol (MIB) is a major concern for farmers and consumers. Here we apply the emerging Fr 13 risk methodology (Food Control 50 (2015) 770–777; Food Control 29 (2013) 248–254) to demonstrate quantitatively the impact of naturally occurring fluctuations in these chemicals in RAS water on their accumulation in fish flesh. The approach is based on the time dependent accumulation model of Hathurusingha and Davey (Ecological Modelling 291 (2014) 242–249) in which taint chemicals enter the flesh via the gills and are diluted through metabolism and growth, together with a risk factor (p) such that for all p > 0 the chemical taint is above a desired threshold concentration (which includes a practical tolerance) respectively, 0.814 and 0.77, μg kg−1 for GSM and MIB. Monte Carlo (with Latin Hypercube) sampling of chemical in the growth water (CW), water temperature (T) and growth time (t) was used to simulate practical RAS farmed barramundi (Lates calcarifer), a premium fish, for up to 260 days growth. Results show some 10.10% of all harvests over the long term will result in fish with taste taint as GSM above the threshold concentration due to natural fluctuations in the RAS environment. For MIB this failure rate is 10.56%. The vulnerability to taste taint failure is shown to be impacted highly significantly by the time to harvest, and to a lesser extent by concentration and fluctuation of the taint chemicals in the RAS water. An advantage is growth time can be readily controlled by farmers; this should not exceed 240 day. The methodology appears generalizable and therefore applicable to a range of RAS farmed foods. Findings will be of immediate benefit to RAS farmers and to risk researchers in foods processing.

Geosmin (GSM), a typical musty odor compound, causes undesirable earthy off-flavors and is a serious concern in the drinking water and aquaculture industries. Here, we employed a novel palladium (Pd) modified tungsten trioxide (WO3) photocatalyst to remove GSM from water under simulated solar light. We also investigated the effect of catalyst loading, GSM initial concentration, light intensity, pH and dissolved oxygen (DO) for GSM destruction. The Pd/WO3 catalyst almost completely degraded GSM within 20 min under optimum conditions, with GSM degradation conforming to a pseudo-first-order reaction. This catalyst also exhibited a superior reuse performance. Photocatalytic degradation rate of GSM decreased in the presence of hydroxyl radical trapping reagent, implying oxidation by hydroxyl radicals plays a very significant role in the photo-degradation mechanism. Some possible intermediates were also identified. These results could provide helpful information for constructing a new efficient system for rapid GSM removal under solar light.

Geosmin is the major off-flavour compound found in rivers and reservoirs during and after cyanobacteria blooms in Korea. A dynamic spatially varying predictive model for geosmin has been developed based on a two-dimensional laterally averaged hydrodynamic and mass transport model, and validated using the field data obtained in North Han River, Korea. The model incorporated the inflow and outflow loadings, production of geosmin by metabolism of cyanobacteria, and the degradation by photolysis, biolysis, and loss by volatilization through a lumped first-order decay rate (K 1 ), which was determined through calibration with the field data. Sensitivity analysis showed that K 1 is very sensitive to the simulation results, and should be accurately measured to improve the model performance. The model successfully captured the outbreaks of geosmin production by cyanobacteria ( Anabaena spp.) and following decline due to physical and biological processes during the four years of simulation period from 2009 to 2012, except the abnormal winter outbreak occurred in December, 2011. The performance of the model could be enhanced by incorporation of diverse sources of geosmin including benthic source and watershed runoff, and the long-term contribution of cell-bound (particulate) fraction. The model could enable water suppliers to predict taste-and-odor episodes caused by cyanobacteria bloom through simulations of spatial and temporal relations between physical, biological and chemical dynamics in the water body.

With its high economic impact, off-flavor in fish is still one of the most serious problems in the aquaculture industry worldwide. Until now, the highly cost- and time-intensive, as well as capacity demanding depuration procedure by moving the fish to clean and odor-free water for a certain time prior to harvest is the only reliable way to counteract off-flavors in aquaculture. Alternative strategies and processes for efficient off-flavor prevention are still lacking. Hence, the aim of this study was to investigate the potential of ultrasonic water treatment to decrease the concentration of the relevant off-flavor compounds geosmin (GSM) and 2-methylisoborneol (2-MIB) in aquaculture water. Therefore, different water matrices, varying in their organic and inorganic load and composition (tap water, RAS fresh water, RAS sea water), were spiked with 2-MIB and GSM standard and subsamples of 250 mL were subsequently treated for 15 min using a lab-scale ultrasound transducer at 850 kHz. For verification samples from commercial RAS containing biogenic 2-MIB and GSM were treated equally. The effects of ultrasound frequency and salinity on the removability of 2-MIB and GSM via ultrasonic treatment were investigated by comparing the removal efficiency of high (850 kHz) vs. low (20 kHz) frequency ultrasound and by adding artificial sea salt (10 ppt) to different freshwater samples prior to ultrasound treatment, respectively. Results have demonstrated that ultrasonically induced cavitation significantly reduces the tested off flavor compounds GSM and 2-MIB in all tested water types, seemingly irrespective of the (in)organic load. In general, the reduction of GSM was slightly higher compared to that of 2-MIB. Furthermore, the reduction of tested off-flavor compounds was significantly enhanced at high frequency ultrasound (850 kHz) compared to low-frequency ultrasound (20 kHz). The addition of artificial sea salt to fresh water samples caused an additional improvement in removability of both off-flavor compounds. Our results evidence high frequency ultrasound as a potential treatment process for significant removal of the relevant off-flavor compounds 2-MIB and GSM from RAS process water. In particular, the seemingly low dependency of the ultrasound-induced removal of GSM and 2-MIB on the organic and inorganic process water load predestines ultrasonically induced cavitation as a potential strategy for off-flavor prevention in RAS compared to alternative strategies such as advanced oxidation processes or adsorption processes. (C) 2015 Elsevier B.V. All rights reserved.

Helicoverpa zea (Boddie) is a major insect pest of corn and other agricultural crops. An improved understanding of semiochemcials that control adult behavior is needed to develop alternative control measures. In this study, overnight SPME collection of volatiles from corn ears enclosed in Teflon bags in the field at two stages of development were made. C8–C10 aldehydes, a C8-alcohol, C6–C9 alcohol acetates, and numerous monoterpenes, sesquiterpenes, sequiterpene alcohols, and geosmin were identified after thermal desorption and GC/MS. Structural assignments of the alcohol acetates, Z-3-hexenyl acetate, 2-heptyl acetate, 2-nonyl acetate, and 4-nonyl acetate, the monoterpenes, α- and β-ocimene, and geosmin were made by analysis of standards that were purchased or prepared in the laboratory. All other assignments were based on published Kovat’s retention time indices (KI) and mass spectra. Pair-wise comparison of the relative amounts of each component between two groups of corn ears defined by silk weight did not identify significant differences, thus it is unknown whether or not silk weight impacted volatile emission composition and rate. To our knowledge three compounds detected in SPME collections, 2-heptyl acetate, 2-nonyl acetate, and 4-nonyl acetate have not been previously reported in corn ear or silk volatiles. Their impact on the flight response of gravid earworm females was evaluated in a flight chamber. No significant response to the individual compounds or a blend of all three was observed. Thus, their impact on moth behavior remains uncertain.

A bioelectronic nose for the real-time assessment of water quality was constructed with human olfactory receptor (hOR) and single-walled carbon nanotube field-effect transistor (swCNT-FET). Geosmin (GSM) and 2-methylisoborneol (MIB), mainly produced by bacteria, are representative odor compounds and also indicators of contamination in the water supply system. For the screening of hORs which respond to these compounds, we performed CRE-luciferase assays of the two odorants in heterologous cell system. Human OR51S1 for GSM and OR3A4 for MIB were selected, and nanovesicles expressing the hORs on surface were produced from HEK-293 cell. Carbon nanotube field-effect transistor was functionalized with the nanovesicles. The bioelectronic nose was able to selectively detect GSM and MIB at concentrations as low as a 10 ng L(-1). Furthermore, detection of these compounds from the real samples such as tap water, bottled water and river water was available without any pretreatment processes.

The presence of earthy-musty odors in drinking water is a major concern for water suppliers and consumers worldwide. While geosmin and 2-methylisoborneol are the most studied earthy-musty odor-causing compounds, pyrazine and its alkyl and methoxy compounds possess similar odors and are widely distributed in nature, foods, and beverages. In this study, odor characteristics of pyrazines and their presence in natural and treated waters were determined. Pyrazine, 2,6-dimethyl-pyrazine (DMP), 2,3,5-trimethyl-pyrazine (TrMP), 2-ethyl-5(6)-methyl-pyrazine (EMP), 2,3,5,6-tetramethyl-pyrazine (TeMP), 2-isobutyl-3-methoxy-pyrazine (IBMP) and 2-isopropyl-3-methoxy-pyrazine (IPMP) were measured in source and finished drinking water across China. 2-Methoxy-3,5-dimethyl-pyrazine (MDMP), IBMP, and IPMP were investigated in rivers in Virginia, USA. The results showed that “musty” and “sweet” were the most common descriptors for pyrazine, DMP, MDMP, TrMP, and TeMP. While IBMP and IPMP were never detected in 140 source or drinking water samples from across China, pyrazine, DMP, MDMP, TrMP, and TeMP occurred throughout with concentrations of n.d.−62.2 ng/L-aq in source water and n.d.−39.6 ng/L-aq in finished water. IBMP, IPMP, and MDMP were present in two Virginia rivers; MDMP occurred in 18% of the samples with concentrations of n.d.−4.4 ng/L, many of which were above the aqueous odor threshold of 0.043 ng/L MDMP. The removal efficiencies through conventional water treatment were poor, ranging from negative removals to ∼10%. Advanced oxidation water treatment could only remove EMP and TrMP. The widespread presence of earthy-musty-sweet pyrazines in source and drinking waters on two continents, their poor removal during water treatment, and ng/L odor threshold concentrations confirm their potential to be T&O issues for consumers.

Granular activated carbon (GAC) is widely used by drinking water treatment plants in the Great Lakes region to control 2-methylisoborneol (MIB) and geosmin associated with summertime algal blooms. Recently, however, taste and odour events are being detected in the winter, but there is limited information in the literature about the effect of temperature on GAC performance. In this study, batch isotherm experiments were conducted at 4 °C, 10 °C, and 20 °C to evaluate the temperature impact on adsorption thermodynamics. Pilot-scale column tests were then performed at the same temperatures to evaluate the temperature effect on overall removal, including both thermodynamics and kinetics. The pore and surface diffusion model (PSDM) was applied to fit the experimental data of the pilot-scale column tests, which allowed the kinetic parameters to be determined at each temperature. The isotherm results showed that water temperature did not have a significant effect on the equilibrium adsorption capacity (i.e., the thermodynamics) of MIB and geosmin adsorption under the conditions tested, but the pilot tests showed an increased removal of MIB and geosmin by 20–30% at 20 °C compared to the lower temperatures. This demonstrates that water temperature has more impact on kinetics than thermodynamics. Numerical simulations showed that the overall external mass transfer coefficient, Kf’, had the greatest impact on breakthrough. An exponential equation was proposed to correlate temperature and Kf’, and it could be incorporated into a site-specific PSDM to predict the removals of MIB and geosmin in GAC contactors at different temperatures. The model could then be used by a utility, for example, to predict the required increase in empty bed contact time needed to control taste and odour in the winter to the same extent as in the summer.

Geosmin (trans-1, 10-dimethyl-trans-9-decalol), a volatile organic compound, has been widely detected in aquatic ecosystems. However, the ecological effects of geosmin are not clear. Here, using zebrafish (Danio rerio) embryo as a model, we investigated biological activity effects of environmentally relevant concentrations (50, 500, 5000 ng/L) of geosmin on the developing zebrafish starting from 2 h post-fertilization (hpf) to 96 hpf. Results showed geosmin had no effect on hatchability, malformations and mortality. However, we observed that geosmin exposure significantly increased zebrafish body length in a concentration dependent manner. This effect was possibly due to up-regulation of expression of genes along the growth hormone/insulin-like growth factor (GH/IGF) axis and hypothalamic-pituitary-thyroid (HPT) axis. In addition, superoxide dismutase (SOD) activities and catalase (CAT) activities significantly increased at 96 hpf when the embryos were exposed to 500 and 5000 ng/L of geosmin. The malondialdehyde (MDA) contents and glutathione S-transferase (GST) activities decreased significantly after the exposure to 5000 ng/L geosmin. Simultaneously, exposure to geosmin resulted in significant increase in cell apoptosis, mainly in the heart area. The mRNA levels of the genes related to oxidative stress and apoptosis were also altered significantly after geosmin exposure. These findings indicated that geosmin can simultaneously induce multiple responses during zebrafish embryonic development, including oxidative stress, apoptosis pathways, and endocrine disruption.

Excessive proliferation of cyanobacteria blooms resulting in metabolic musty-earthy odor materials such as geosmin (GSM) pose potential risks to aquatic ecosystems and human health. In this paper, a high-yield OH equipment was developed to be installed in drinking water treatment system with a capacity of 12,000 m3/day in the Xiang’an Water Plant, Xiamen, China, and the comparison of OH and NaClO on GSM degradation in the process of algae colonies inactivation were studied. The results showed that with OH inactivation at 1.0 mg/L within 20 s algae colonies were scattered to individual algae that still had intact shape, while with the NaClO inactivation at 2 h algae still mainly existed as colonies form but were deformed and ruptured due to extensive damage of cell membrane. After the coagulation sedimentation with injection of OH at 1.0 mg/L and the sand filtration at 0.5 mg/L, the GSM were both degraded to below 10 ng/L (Chinese standard limit) within only 20 s, while the NaClO degraded GSM slightly until 2 h later. Based on the intermediates analyses with mass spectra database, pathways of GSM degradation by OH or NaClO were obtained. With OH disinfection at 0.5 mg/L, all water quality and disinfection by-product indexes satisfied the limits of Chinese Standards. Therefore, the OH method based on the strong ionization discharge showed great prospect for large-scale industrial application in inactivation of algae colonies meanwhile degradation of odorous material GSM.

Common off-flavor compounds including geosmin (GSM) bioaccumulate in fish cultured in recirculating aquaculture systems (RAS) resulting in unpalatable fillets that are objectional to consumers. Most RAS facilities relocate fish from grow-out tanks to separate depuration systems with increased water flushing to remediate pre-harvest off-flavors, but certain aspects of this procedure have not been optimized including characterization of water exchange rates that effectively diminish off-flavor. To this end, a study was carried out to evaluate the effects of flushing rate and associated depuration system hydraulic retention time (HRT) on GSM removal from Atlantic salmon Salmo salar originally produced in a semi-commercial scale freshwater RAS. Twenty-six fish (5−7 kg each) were stocked into twelve replicate depuration systems operated with system HRTs of 2.4, 4.6, and 11.3-h, respectively (N = 4). Geosmin was assessed at intervals in system water and fish flesh over a 10-day feed withholding period. Waterborne GSM concentration was affected by flushing rate and associated system HRT (P

Aesthetics and water quality are primary issues of concern for sustainable water reuse since aesthetically unpleasant color and odor are likely to induce public misgiving. This study utilizes aesthetic indicators and other bulk water quality parameters for evaluation. It is found that ozonation during advanced treatment processes in a full-scale water reclamation plant (WRP) could achieve satisfactory performance in decolorization and oxidation of aromatic and humic contents. As limited efficacy on odor removal was detected in the WRP, this study further researched the removal of the main odorant substances 2-methylisokanol (2-MIB) and geosmin (GSM) with different ozone dosage using solid-phase extraction (SPE) and gas phase mass spectrometry (GC–MS) techniques. According to the first-order reaction kinetics, it is inferred that competitive reactions during ozonation by organic matters and restricted CT values are major factors affecting the odor removal. As such, additional treatment approaches such as nanofiltration (NF) are suggested to be consider for aesthetic control towards sustainable and long-term reclaimed water use.

Since excreted feed nitrogen is bio-transformed efficiently in a fully functional mixotrophic biofloc technology production system, re-using this biofloc water over multiple production cycles should be beneficial. The present study, conducted in an outdoor biofloc technology production system, evaluated impacts on fish production characteristics and mineral status, common microbial off-flavors, and water quality dynamics for channel catfish (Ictalurus punctatus) reared in one-year-old waters with low or high total suspended solids used previously for two consecutive catfish biofloc studies or in unused (new) water. Total suspended solids were maintained at 300 to 400 mg/L in the unused and low total suspended solids used water treatments and allowed to accumulate in the high total suspended solids used water treatment. Tanks (18.6 m2, 15.7 m3) were stocked with fingerlings (47.5 ± 0.8 g/fish) at 13.5 fish/m2 (16 fish/m3) and grown for 181 days. Channel catfish production characteristics did not differ significantly among treatments. Overall, gross fish yield averaged 10.2 kg/m3 and fish averaged 642 g/fish. Nitrate accumulation rate was affected by total suspended solids concentration with a significant reduction observed at the highest discharge of solids from the system, suggesting wash-out of nitrifiers. Treatment effects on water quality dynamics, macro- and trace-mineral status of water, feed, and fish, 2-methylisoborneol and geosmin off-flavors and associated phytoplankton populations also are discussed. Results of this study suggest that one-year-old biofloc water can be used without adverse impact for a second year of channel catfish production in the biofloc system.

Effect of water treatment on concentrations of the off-flavor geosmin was examined in a RAS facility for commercial production of pikeperch (Stizostedion lucioperca). Short-term (minutes) and long-term (days) variations in concentrations of geosmin were measured in grow-out tanks, at inlet and outlet of biofilters and at the denitrification unit. Geosmin in water of the grow-out tanks ranged typically from

Organic matter-induced black bloom frequently occurs in a number of large eutrophic shallow lakes; this can result in the release of malodorous compounds and has a negative impact on water quality. In the study, a microcosm system containing Zizania latifolia (Z. latifolia), a common aquatic plant, was established and the release of seven taste and odour compounds, dimethyl sulphide (DMS), dimethyl disulphide (DMDS), dimethyl trisulphide (DMTS), 2-methylisoborneol (MIB), geosmin (GSM), β-cyclocitral, and β-ionone, was investigated. The results showed that these compounds were all detected during Z. latifolia decay, and that volatile organic sulphur compounds (VOSCs), such as DMS, DMDS, and DMTS, were the main factors responsible for the strong foul odour (the maximum reached 5.0 μg L−1). The release of odorous compounds was stronger during the initial seven days, and then progressively decreased in the middle stage of the experiment. Furthermore, large amounts of nutrients were released into the overlying water; nutrient concentration increased with increasing plant biomass. A positive correlation was observed between the odorant concentration and plant biomass. These results indicate that the density of aquatic plants should be controlled as part of future management of aquatic ecosystems.

Advanced oxidation processes (AOPs) can be used to destroy taste and odour-causing compounds in drinking water. This work investigated both pilot- and full-scale performance of the novel ultraviolet (UV)/chlorine AOP for the destruction of geosmin, 2-methylisoborneol (MIB) and caffeine (as a surrogate) in two different surface waters. The efficiency of the UV/chlorine process at pH 7.5 and 8.5 was comparable to that of the UV/hydrogen peroxide (UV/H2O2) process under parallel conditions, and was superior at pH 6.5. Caffeine was found to be a suitable surrogate for geosmin and MIB, and could be used as a more economical alternative to geosmin or MIB spiking for site-specific full-scale testing.

The increasing frequency and intensity of taste and odour (TO) producing cyanobacteria in water sources is a growing global issue. Geosmin and 2-methylisoborneol (MIB) are the main cyanobacterial TO compounds and can cause complaints from consumers at levels as low as 10 ng/L. However, literature concerning the performance of full-scale treatment processes for geosmin and MIB removal is rare. Hence, the objectives of this study were to: 1) estimate the accumulation and breakthrough of geosmin and MIB inside full-scale water treatment plants; 2) verify the potential impact of sludge recycling practice on performance of plants; and, 3) assess the effectiveness of aged GAC for the removal of these compounds. Sampling after full-scale treatment processes and GAC pilot assays were conducted to achieve these goals. Geosmin and MIB monitoring in full-scale plants provided the opportunity to rank the performance of studied treatment processes with filtration and granular activated carbon providing the best barriers for removal of total and extracellular compounds, correspondingly. Geosmin was removed to a greater extent than MIB using GAC. Geosmin and MIB residuals in water post GAC contactors after two years of operation was 20% and 40% of initial concentrations, correspondingly. Biological activity on the GAC surface enhanced the removal of TO compounds. These observations demonstrated that a multi-barrier treatment approach is required to ensure cyanobacteria and their TO compounds are effectively removed from drinking water.

This paper describes the results of measurements from one year period on the existence of fishy and musty odor in drinking water at low temperatures (1–2 °C) in Baotou, China, using an open-loop stripping analysis (OLSA) systems and Gas chromatography spectrometry (GC). The main results show that it is micro-contaminated water body of the raw water in Huajiang Reservoir. The average phytoplankton abundance was 2.06×107 L−1, Cyanobacteria counts were at 2.0×106 L−1 and the dominate family of the algae are Chlorophyta, Cryptophyta, and Bacillariophyta. Experimental results indicated that under the ice whose thickness was 0.55 m, the photosynthetically active radiation (PAR) of the surface varied from 70 to 636 W m−2 from November to March of next year. The average surface PAR was 114.8 W m−2, and the lowest value was 70.57 W m−2 (in December) and the average bottom PAR was 19.04 W m−2, and the lowest value was 3.84 W m−2 (in December). The surface PAR, bottom PAR, eutrophic conditions in ice-covered Huajiang reservoir satisfied the growth and MIB/geosmin production of Cyanobacteria algae in winter. The 2-methyl-isoborneol (MIB) concentration ranged from 29 ng L−1 to 102 ng L−1. The concentration of trans-1,10-dimethyl-trans-9-decalol (geosmin) ranges from 20 ng L−1 to 65 ng L−1 and it is 2 to 5 times of the odor threshold concentrations (OTC). The correlations between MIB/geosmin and nitrogen are 0.63–0.37. Eutrophication is the most important factor influencing synthesis of taste and odors, but not temperature. Using bypassing pipe pumping Yellow River water directly to the Water treatment plant (WTP) is an efficient way about T&O compounds׳ control in drinking water of Baotou city in winter.

2-methylisoborneol (2-MIB) and geosmin are two odor-causing compounds that are difficult to remove and the cause of many consumer complaints. In this study, we assessed the degradation of 2-MIB and geosmin using a UV/persulfate process for the first time. The results showed that both 2-MIB and geosmin could be degraded effectively using this process. The process was modeled based on steady-state assumption with respect to the odor-causing compounds and either hydroxyl or sulfate radicals. The second order rate constants for 2-MIB and geosmin reacting with the sulfate radical ( SO 4 − ) were estimated to be (4.2 ± 0.6) × 10 8 M −1 s −1 and (7.6 ± 0.6) × 10 8 M −1 s −1 respectively at a pH of 7.0. The contributions of the hydroxyl radical (OH ) to 2-MIB and geosmin degradation were 3.5 times and 2.0 times higher, respectively, than the contribution from SO 4 − in Milli-Q water with 2 mM phosphate buffer at pH 7.0. The pseudo-first-order rate constants ( k o s ) of both 2-MIB and geosmin increased with increasing dosages of persulfate. Although pH did not affect the degradation of 2-MIB and geosmin directly, different scavenging effects of hydrogen phosphate and dihydrogen phosphate resulted in higher values of k o s for both 2-MIB and geosmin in acidic condition. Bicarbonate and natural organic matter (NOM) inhibited the degradation of both 2-MIB and geosmin dramatically through consuming OH and SO 4 − and were likely to be the main radical scavengers in natural waters when using UV/persulfate process to control 2-MIB and geosmin.

Frequent off-flavor events caused by geosmin and 2-methylisoborneol (MIB) have attracted research on the main producers, cyanobacteria. This study evaluated the effects of light and temperature on the odor production of MIB-producing Pseudanabaena sp. Lauterborn and geosmin-producing Anabaena ucrainica (Schhorb.) Watanabe. The maximum MIB production and lowest growth rate (indicated by the chlorophyll a (Chi a)) were observed at 35 degrees C compared with that at 10 degrees C and 25 degrees C Cultures grown under a light intensity of 60 mu mol photons m(-2) s(-1) demonstrated the highest MIB production and minimum growth rate, whereas the minimum MIB production and maximum growth rate were obtained under 10 mu mol photons m(-2) s(-1). Similar patterns were observed for geosmin production. A. ucrainica had the highest geosmin production and lowest Chl a concentration under 10 degrees C and 60 mu mol photons m(-2) s(-1). Moreover, greater proportions of geosmin and MIB were released into extracellular under growth-inhibiting temperatures and light intensities. An inverse correlation between odor production and the cell growth rate was suggested, and this relationship may reflect the competition for substrates of odor and Chl a synthesis. Thus, the accumulation of geosmin and MIB was probably the result of decreased cellular metabolic activity in cyanobacteria. (C) 2014 Elsevier Ltd. All rights reserved.

Geosmin and 2-methylisoborneol (MIB) are muddy/earthy off-flavor metabolites produced by a range of bacteria. Cyanobacteria are the major producers of the volatile metabolites geosmin and MIB which produce taste and odor problems in drinking water and fish worldwide. Here we detected geosmin and MIB by studying 100 cyanobacteria strains using solid phase microextraction gas chromatography mass spectrometry (SPME GC–MS). A total of 21 geosmin producers were identified from six cyanobacteria genera. Two of the geosmin producers also produced MIB. A PCR protocol for the detection of geo A and MIB synthase genes involved in the biosynthesis of geosmin and MIB was developed. The geo A and MIB synthase genes were detected in all strains shown to produce geosmin and MIB, respectively. Cyanobacterial geo A and MIB synthase sequences showed homology to terpene synthases genes of actinobacteria and proteobacteria. Additional off-flavor compounds, nor-carotenoids β-ionone and β-cyclocitral, were found from 55 strains among the 100 cyanobacterial strains studied; β-ionone was present in 45 and β-cyclocitral in 10 strains. Six of the cyanobacteria which contain off-flavor compounds also produced toxins, anatoxin-a or microcystins. The molecular method developed is a useful tool in monitoring potential cyanobacterial producers of geosmin and MIB.