Performances of full-scale biological nitrogen pre-treatment process for drinking water source: Seasonal variations and microbial community.

This study investigated the performance of the full-scale unit over a two-year period to enhance nitrification efficiency and provide operational strategies. Results indicated that raw water quality from Donggan River was notably influenced by seasonal variations, particularly during dry and wet seasons, impacting the nitrification efficiency of the biological pretreatment process. Factors such as influent concentrations of ammonia and total Kjeldahl nitrogen were found to have significant effects on nitrification, with temperature and conductivity also showing correlations. The specific rate of ammonia removal was calculated to be approximately 0.1 kg-N/m3/d under the existing operational setup. Moreover, elevating dissolved oxygen levels above 4 mg/L was proposed to potentially boost ammonia oxidation based on findings from experiments conducted in lab-scale bioreactors. In times of increased influent ammonia levels, the elimination of about 1-3 mg-N/L of total nitrogen signified the activation of denitrification processes. This observation was corroborated by results from next-generation sequencing techniques, verifying the existence of denitrifying microorganisms. The real-time PCR analysis results indicated that the abundance of comammox amoA gene was comparable with the abundance of the AOB amoA gene, indicating the presence of comammox Nitrospira and their potential role on nitrification in the system.

First principles modelling of the ion binding capacity of finger millet.

Finger millet, a cereal grain widely consumed in India and Africa, has gained more attention in recent years due to its high dietary fibre (arabinoxylan) and trace mineral content, and its climate resilience. The aim of this study was to understand the interactions between potassium (K+), calcium (Ca2+) and zinc (Zn2+) ions and the arabinoxylan structure and determine its ion-binding capacity. Three variations of a proposed model of the arabinoxylan structure were constructed and first principles Density Functional Theory calculations were carried out to determine the cation-binding capacity of the arabinoxylan complexes. Zn2+-arabinoxylan complexes were highly unstable and thermodynamically unfavourable in all three models. Ca2+ and K+ ions, however, form thermodynamically stable complexes, particularly involving two glucuronic acid residues as a binding pocket. Glucuronic acid residues are found to play a key role in stabilising the cation-arabinoxylan complex, and steric effects are more important to the stability than charge density. Our results highlight the most important structural features of the millet fibre regarding ion-storage capacity, and provide valuable preliminary data for confirmatory experimental studies and for the planning of clinical trials where the bioavailability of bound ions following digestion may be tested.

Challenges in Environmental Science/Engineering and fate and innovative treatment/remediation of emerging pollutants.

Solid waste Management: There are two articles in this section. Shi et al. (2021) investigated the unbalanced status and multidimensional influences of municipal solid waste management in Africa. It was identified that economic growth, urbanization and geographical location are the most critical factors influencing the unbalanced statue of MSW management in Africa.

Precision early detection of invasive and toxic cyanobacteria: A case study of Raphidiopsis raciborskii.

Blooms of the toxic cyanobacterium, Raphidiopsis raciborskii (basionym Cylindrospermopsis raciborskii), are becoming a major environmental issue in freshwater ecosystems globally. Our precision prevention and early detection of R. raciborskii blooms rely upon the accuracy and speed of the monitoring method. A duplex digital PCR (dPCR) monitoring approach was developed and validated to detect the abundance and toxin-producing potential of R. raciborskii simultaneously in both laboratory spiked and environmental samples. Results of dPCR were strongly correlated with traditional real time quantitative PCR (qPCR) and microscopy for both laboratory and environmental samples. However, discrepancies between methods were observed when measuring R. raciborskii at low abundance (1 - 105 cells L - 1), with dPCR showing a higher precision compared to qPCR at low cell concentration. Furthermore, the dPCR assay had the highest detection rate for over two hundred environmental samples especially under low abundance conditions, followed by microscopy and qPCR. dPCR assay had the advantages of simple operation, time-saving, high sensitivity and excellent reproducibility. Therefore, dPCR would be a fast and precise monitoring method for the early warning of toxic bloom-forming cyanobacterial species and assessment of water quality risks, which can improve prediction and prevention of the impacts of harmful cyanobacterial bloom events in inland waters.

Combined impact of silver nanoparticles and chlorine on the cell integrity and toxin release of Microcystis aeruginosa.

Silver nanoparticles (AgNPs) have shown to be toxic to freshwater cyanobacterial species, and sodium hypochlorite (NaOCl) is a common oxidant for the treatment of cyanobacterial cells. AgNPs have a high possibility of co-existing with the cyanobacterial cells in the aqueous environments leading to its exposure to NaOCl during water treatment; however, their combined effects on the cyanobacterial cells are largely undocumented. This work compares the individual and combined effect of AgNP and NaOCl on the integrity and toxin (microcystins) release of Microcystis aeruginosa at varying levels. The results show that the AgNP (0.2-0.6 mg/L) alone has negligible effects on the cell lysis, while NaOCl alone shows concentration-dependent (0.2 < 0.4 < 0.6 mg/L) rupturing of cells. In contrast, the AgNP + NaOCl (0.2-0.6 mg/L) samples show increasing loss in cell integrity at higher AgNP (0.4 and 0.6 mg/L) levels than the NaOCl only samples. NaOCl exposure results in increasing dissolution of AgNPs with time, releasing silver ions (Ag+), affecting its size and morphology. The cell-associated total Ag declines over time with an increase in NaOCl levels, maybe due to increasing cell-lysis or NaOCl induced oxidative dissolution of AgNPs. The cell-associated total Ag and released Ag+ possibly weaken the cellular membrane, thus assisting NaOCl in faster cell-lysis. The combined exposure of AgNP and NaOCl also results in a higher release of toxin from the cells. This work collectively reveals that the AgNPs combined with NaOCl can enhance the cell lysis and release of toxins.

Quantitative PCR based detection system for cyanobacterial geosmin/2-methylisoborneol (2-MIB) events in drinking water sources: Current status and challenges.

Taste and odor (T&O) are an important issue in drinking water, aquaculture, recreation and a few other associated industries, and cyanobacteria-relevant geosmin and 2-methylisoborneol (2-MIB) are the two most commonly detected T&O compounds worldwide. A rise in the cyanobacterial blooms and associated geosmin/2-MIB episodes due to anthropogenic activities as well as climate change has led to global concerns for drinking water quality. The increasing awareness for the safe drinking, aquaculture or recreational water systems has boost the demand for rapid, robust, on-site early detection and monitoring system for cyanobacterial geosmin/2-MIB events. In past years, research has indicated quantitative PCR (qPCR) as one of the promising tools for detection of geosmin/2-MIB episodes. It offers advantages of detecting the source organism even at very low concentrations, distinction of odor-producing cyanobacterial strains from non-producers and evaluation of odor producing potential of the cyanobacteria at much faster rates compared to conventional techniques.The present review aims at examining the current status of developed qPCR primers and probes in identifying and detecting the cyanobacterial blooms along with geosmin/2-MIB events. Among the more than 100 articles about cyanobacteria associated geosmin/2-MIB in drinking water systems published after 1990, limited reports (approx. 10 each for geosmin and 2-MIB) focused on qPCR detection and its application in the field. Based on the review of literature, a comprehensive open access global cyanobacterial geosmin/2-MIB events database (CyanoGM Explorer) is curated. It acts as a single platform to access updated information related to origin and geographical distribution of geosmin/2-MIB events, cyanobacterial producers, frequency, and techniques associated with the monitoring of the events. Although a total of 132 cyanobacterial strains from 21 genera and 72 cyanobacterial strains from 13 genera have been reported for geosmin and 2-MIB production, respectively, only 58 geosmin and 28 2-MIB synthesis regions have been assembled in the NCBI database. Based on the identity, geosmin sequences were found to be more diverse in the geosmin synthase conserved/primer design region, compared to 2-MIB synthesis region, hindering the design of universal primers/probes. Emerging technologies such as the bioelectronic nose, Surface Enhanced Raman Scattering (SERS), and nanopore sequencing are discussed for future applications in early on-site detection of geosmin/2-MIB and producers. In the end, the paper also highlights various challenges in applying qPCR as a universal system of monitoring and development of response system for geosmin/2-MIB episodes.

Prediction of adsorption capacity for pharmaceuticals, personal care products and endocrine disrupting chemicals onto various adsorbent materials.

Adsorption is a common process used to remove pharmaceuticals, personal care products and endocrine disrupting chemicals (PPCPs/EDCs) from water. However, as PPCPs/EDCs cover a wide range of molecules and chemical structures, prediction of the adsorption capacity is very challenging. In this study, a novel model was developed to predict adsorption isotherms of PPCPs/EDCs onto various types of adsorbents using a combination of Polanyi potential theory, molecular connectivity indices (MCIs) and molecular characteristics. Polanyi theory provided the basic mathematical form for the correlation. MCIs, hydrophobicity and H-bond count were used to normalize the Polanyi equation based on the molecular structure and interactions among the chemicals, the adsorbents, and the solution. In total, adsorption data were collected from 158 reports for 55 PPCPs/EDCs onto 306 different adsorbent materials. The correlation was first trained with 46 PPCPs/EDCs adsorbed onto 162 carbonaceous adsorbents (CAs), with 44.8% SDEV. Then the model was employed to predict 46 PPCPs/EDCs onto 118 other CAs and 9 new PPCPs/EDCs onto 23 CAs in ultrapure water, with error from 42 to 48% SDEV. When applying to non-carbonaceous adsorbents, the models can still predict the adsorption of PPCPs/EDCs with 90.09% SDEV. For the first time, a model, the PD - MCI - hydrophobic - H bond model, was developed to predict adsorption of a wide group of complicated PPCPs/EDCs onto a big variety of carbonaceous and non-carbonaceous adsorbents. The proposed model approach may provide a simple means for predicting adsorption capacities of PPCPs/EDCs onto various adsorbents.

Roles of Silver-Chloride Complexations in Sunlight-Driven Formation of Silver Nanoparticles.

In aerobic natural surface water, a silver ion (Ag+) exists in various Ag+-Cl- complexes because of a strong affinity for a chloride ion (Cl-); however, little information is available about the role of the Ag+-Cl- complex in the formation of silver nanoparticles (AgNPs). This study demonstrates that soluble AgClx(x-1)- species act as a precursor of AgNPs under simulated sunlight irradiation. The AgNP photoproduction increases with Cl- levels up to 0.0025 M ([Ag+] = 5 × 10-7 M) and decreases with continued Cl- level increase (0.09 to 0.5 M). At [Cl-] ≤ 0.0025 M (freshwater systems), photoproduction of AgNP correlates with the formation of AgCl(aq), suggesting that it is the most photoactive species in those systems. Matching the ionic strength of experiments containing various Cl- levels indicates that the trend in AgNP photoproduction correlates with Cl- concentrations rather than ionic strength-induced effects. The photoproduction of AgNPs is highly pH-dependent, especially at pH > 8.3. The UV and visible light portions of the solar light spectrum are equally important in photoreduction of Ag+. Overall, we show evidence that AgClx(x-1)- species irradiated under sunlight conditions contributes to the formation of nanosized silver (Ag) in the environment.

A molecular-based method to estimate the risk associated with cyanotoxins and odor compounds in drinking water sources.

A biomolecular-based monitoring approach for the assessment of water quality hazards and risks associated with cyanobacteria was developed and validated in drinking reservoirs in Taiwan and the Philippines. The approach was based upon the measurement of gene abundances of toxigenic Microcystis and Cylindrospermopsis; for cyanotoxins; and for aesthetically offensive earthy-musty odor compounds. This was compared to conventional monitoring approaches, which included cell enumeration by microscopy, and toxin and odor compound analysis by instrumental analytical methods and immunoassays as appropriate for the metabolites. The validation involved samples from ten major reservoirs on Taiwan's main island, nineteen reservoirs on the offshore islands, and Laguna de Bay in the Philippines. The gene-based approach was successfully validated statistically and compared to conventional widely utilized risk assessment schemes which have employed 'Alert Levels' for toxic cyanobacteria. In this case a new integrated scheme of 'Response Levels' is proposed which incorporates odor metabolite hazards in addition to cyanotoxins and is based upon gene copy numbers to derive quantitative triggers. The comprehensive scheme evaluated from these locations is considered to be more precise and efficient for both monitoring and as a risk assessment diagnostic tool, given that it offers the capacity for analysis of the abundance of genes for cyanobacterial metabolites in large numbers of natural water samples in a significantly reduced period of time compared to the approaches of cell enumeration by microscopy or metabolite analytical techniques. This approach is the first time both the hazard and risk for both odors and cyanotoxins from cyanobacteria have been considered together in a monitoring scheme and offers an improved means for determining the Response Levels in the risk assessment process for cyanobacteria and their metabolites in drinking water sources.

Application of molecular biological tools for monitoring efficiency of trichloroethylene remediation.

Trichloroethylene (TCE) is one of the most ubiquitous halogenated organic compounds of concerns of carcinogens in groundwater in Taiwan. Bioremediation has been recognized as a cost-effective approach in reducing TCE concentration. Five pilot-scale wells were constructed to monitor TCE concentrations in contaminated groundwater. With injection of EOS®, TCE was effectively degraded to 42%-93% by the end of 175 days. The biostimulation with EOS® was useful in establishing a micro-site anaerobic but with limited contribution. Dilution of the aquifer movement also caused the TCE reduction among injection and monitoring wells. The degradability was affected by the location and the proximity from the injection well. TCE concentrations found to be negatively correlated with the associated Dehalococcoides spp. and functional genes levels. Dhc concentration of 108 copies L-1 caused the initial 40% of TCE degradation. The well with the optimal degradation owned tceA of 109 cells L-1. T-RFLP results indicate the wells with the superior TCE degradability also performed the highest Shannon index number (means the highest diversity), which occurred on the same day that Dhc levels started to enlarge. Desulfovibrio desulfuricans and Desulfuromonas chloroethenica were predominant species identified in the T-RFLP fingerprint profile. In brief, a variety of different factors including well locations, geochemical indicators, and microbial contribution were useful to explain the site-specific optimal TCE remediation approach. The consistence among TCE degradation, Dhc growing pattern, functional gene levels, and the dynamics of the microbial community structure present the novelty of this study.

Oxidation of cyanobacterial neurotoxin beta-N-methylamino-L-alanine (BMAA) with chlorine, permanganate, ozone, hydrogen peroxide and hydroxyl radical.

Beta-N-methylamino-L-alanine (BMAA), a new cyanobacterial neurotoxin produced by more than 20 genera of cyanobacteria, has been associated with amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) or Alzheimer's disease. Although BMAA has been shown to be removed in drinking water treatment plants (DWTPs), studies regarding the reactions between BMAA and the commonly used oxidants in DWTPs are limited to chlorine under specific conditions. In this study, the reaction kinetics between BMAA and five oxidants commonly used in DWTPs, including chlorine, potassium permanganate, ozone, hydrogen peroxide and hydroxyl radical were investigated. The oxidation of BMAA by chlorine, ozone or OH radical followed the second order reaction rate law, and the reaction rate was in the order of OH radicals > ozone >> chlorine. The rate constants increased by 20 times from 2 × 103 M-1s-1 at pH 5.8 to 4.93 × 104 M-1s-1 at pH 7, and kept in a relatively stable level at pH 7-9.5; rate constants of OH radicals were 1.11 × 108 M-1s-1 at pH 6.5 and 5.51 × 109- 1.35 × 1010 M-1s-1 at pH > 6.5. For both permanganate and H2O2 only, the removal of BMAA was negligible. The pH dependency of chlorine and the OH radical may be attributed to the neutral form of BMAA with free lone pair electrons readily to be attacked by oxidants. However, for ozonation of BMAA, the rate constants were 1.88 × 106-3.72 × 1010 M-1s-1, with a linear dependency on pH, implying that the hydroxide concentration governs the reaction. In addition, the rate of BMAA degradation was found to be slower in natural water if compared with that in deionized water.

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.

Exposure of Microcystis aeruginosa to hydrogen peroxide and titanium dioxide under visible light conditions: Modeling the impact of hydrogen peroxide and hydroxyl radical on cell rupture and microcystin degradation.

The aims of this study are to evaluate, under visible light conditions, the ability of H2O2 and TiO2 to produce OH, their quantitative impacts on the cell integrity of Microcystis, and the subsequent release and degradation of microcystins (MCs). A sequential reaction model was developed, including one sub-model to simulate the rupture kinetics for cell integrity of Microcystis, and another to describe the release and degradation of MCs. For cell rupture, the dual-oxidant Delayed Chick-Watson model (DCWM) and dual-oxidant Hom model (HM) were first proposed and developed, giving excellent simulation results of cell rupture kinetics. Kinetic rate constants between Microcystis cells and H2O2 [Formula: see text] as well as OH (k•OH, Cell) under visible light successfully separated the individual effects of H2O2 and OH on Microcystis. The dual-oxidant models were further validated with additional experiments, making the models more convincing. Finally, the dual-oxidant cell rupture models were integrated with the MC degradation model and well predicted the observed MCs concentrations in the experimental systems. The results of this study not only demonstrate the potential application of H2O2 and TiO2 for the control of cyanobacteria and metabolites in natural water bodies, but also provide a new methodology to differentiate the individual contributions of the two oxidants, H2O2 and OH, on cell rupture, thus giving a novel way to more precisely determine the effective doses of applied oxidants for cyanobacteria control.

Pilot study of cold-rolling wastewater treatment using single-stage anaerobic fluidized membrane bioreactor.

A pilot-scale single-stage anaerobic fluidized membrane bioreactor (AFMBR) was firstly used in this study to treat cold-rolling emulsion wastewater from steel industry. It was continuously operated for 302 days with influent COD concentration of 860-1120 mg/L. Under a hydraulic retention time of 1.5 d, the average effluent COD concentration of 72 mg/L achieved corresponding 90% of COD removal. The permeate flux was varied between 1.7 and 2.9 L/m2/h during operation which decreased with increased biomass concentration inside AFMBR. The trans-membrane pressure (TMP) was generally around 35-40 kPa, however, it increased up to 60 kPa when volatile suspended solid increased to above 2.5 g/L. Both flux and TMP data reveal the importance of biomass control for AFMBR operation. Results from terminal restriction fragment length polymorphism (T-RFLP) show the genus Methanosaeta was dominant on GAC and it shared dominance with the genera Methanomethylovorans and Methanosarcina in suspended sludge.

N-nitrosamines in drinking water and beer: Detection and risk assessment.

Occurrence and risk related to nitrosamines, a group of carcinogenic compounds found in some drinking waters and beer, are studied. An analytical method using a solid-phase micro-extraction (SPME) along with gas chromatography (GC) and mass spectrometry (MS) was developed to determine seven N-nitrosamines in drinking water and beer, including N-nitrosomethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosodimethylamine (NDMA), N-nitrosodi-n-propylamine (NDPA), N-nitrosopyrrolidine (NPyr), N-nitrosopiperidine (NPip), and N-nitrosodinbutylamine (NDBA). The analysis can be completed in 70 min, and only a 4 mL sample is required, with a detection limit of 0.1-0.8 ng/L for the seven nitrosamines in water and 6-15.7 ng/L in beer. The method was applied to analyze water samples collected from 11 reservoirs and their associated drinking water treatment plants in Taiwan and 10 beer samples from 6 brands with factories located in 6 countries. In the drinking water samples, all seven N-nitrosamines were detected, with NDMA having the highest level at 10.2 ng/L. In the beer samples, NDMA was detected at much lower concentrations (0.12-0.23 µg/L) than the 5 µg/L US standard, while NPip was detected at much higher concentrations (4.1-5.3 µg/L) compared to NDMA. The risk assessment indicates that the risk associated with NDMA is the highest among the studied N-nitrosamines in Taiwan's drinking water, with an average cancer risk of 6.4 × 10-06. For other nitrosamines, the risks are all below 10-6. For the risks associated with N-nitrosamines in beer, NDMA, NDEA, NDPA, and NPip are in the range of 1.5 × 10-05 to 4.6 × 10-04, while that for other nitrosamines are much lower. As for beer, no information for NPip and no modern information for NDEA and NDPA have previously been available, more studies about nitrosamines in beer are suggested for better estimation and control of the risks associated with consumption of beer.

Evaluation of potassium ferrate as an alternative disinfectant on cyanobacteria inactivation and associated toxin fate in various waters.

Potassium ferrate (K2FeO4) is an effective oxidant that may be used as a pre- or post-oxidant in the purification of source water with cyanobacterial issues. To provide a better basis for the application of this oxidant during water treatment processes, the impacts of K2FeO4 on the cell viability of Microcystis aeruginosa and the fate of associated microcystins (MCs) were investigated in various water matrices. The results showed that a water matrix can significantly affect the effectiveness of K2FeO4 on cyanobacteria inactivation. 10 mg L-1 K2FeO4 induced significant cell lysis of M. aeruginosa in Ran Yi Tan Reservoir (RYTR) water while the membrane integrity was relatively unaffected in ASM-1 media and Cheng Kung Lake (CKL) water. The reduced efficiency of K2FeO4 oxidation may be attributed to the manganese (Mn2+) and organic matter (Ethylenediaminetetraacetic acid, EDTA) in the ASM-1 media and high concentrations of natural organic matters (NOMs) in the CKL water. A delayed Chick-Watson model was applied to simulate the experimental data for cyanobacterial cell rupture, and the cell lysis rates of the M. aeruginosa samples were determined to be 128-242 M-1 s-1 (mol L-1 s-1). Generally, no significant increases in extracellular MCs were observed in the three different waters, even in the RYTR water where the membrane integrity of the cyanobacterial cells was severely disrupted. Therefore, K2FeO4 could be a potential pre-oxidant to enhance subsequent treatments for cyanobacteria removal without affecting the cell integrity, or could serve as a post-oxidant to inactivate cyanobacterial cells and degrade MCs effectively, depending on the specific water matrix.

Optimization of the Determination Method for Dissolved Cyanobacterial Toxin BMAA in Natural Water.

There is a serious dispute on the existence of ß-N-methylamino-l-alanine (BMAA) in water, which is a neurotoxin that may cause amyotrophic lateral sclerosis/Parkinson's disease (ALS/PDC) and Alzheimer' disease. It is believed that a reliable and sensitive analytical method for the determination of BMAA is urgently required to resolve this dispute. In the present study, the solid phase extraction (SPE) procedure and the analytical method for dissolved BMAA in water were investigated and optimized. The results showed both derivatized and underivatized methods were qualified for the measurement of BMAA and its isomer in natural water, and the limit of detection and the precision of the two methods were comparable. Cartridge characteristics and SPE conditions could greatly affect the SPE performance, and the competition of natural organic matter is the primary factor causing the low recovery of BMAA, which was reduced from approximately 90% in pure water to 38.11% in natural water. The optimized SPE method for BMAA was a combination of rinsed SPE cartridges, controlled loading/elution rates and elution solution, evaporation at 55 °C, reconstitution of a solution mixture, and filtration by polyvinylidene fluoride membrane. This optimized method achieved > 88% recovery of BMAA in both algal solution and river water. The developed method can provide an efficient way to evaluate the actual concentration levels of BMAA in actual water environments and drinking water systems.

A qPCR-Based Tool to Diagnose the Presence of Harmful Cyanobacteria and Cyanotoxins in Drinking Water Sources.

Harmful cyanobacteria have been an important concern for drinking water quality for quite some time, as they may produce cyanotoxins and odorants. Microcystis and Cylindrospermopsis are two common harmful cyanobacterial genera detected in freshwater lakes and reservoirs, with microcystins (MCs) and cylindrospermopsin (CYN) as their important metabolites, respectively. In this study, two sets of duplex qPCR systems were developed, one for quantifying potentially-toxigenic Microcystis and Microcystis, and the other one for cylindrospermopsin-producing cyanobacteria and Cylindrospermopsis. The duplex qPCR systems were developed and validated in the laboratory by using 338 samples collected from 29 reservoirs in Taiwan and her offshore islands. Results show that cell numbers of Microcystis and Cylindorspermopsis enumerated with microscopy, and MCs and CYN concentrations measured with the enzyme-linked immuno-sorbent assay method, correlated well with their corresponding gene copies determined with the qPCR systems (range of coefficients of determination R² = 0.392-0.740). The developed qPCR approach may serve as a useful tool for the water industry to diagnose the presence of harmful cyanobacteria and the potential presence of cyanotoxins in source waters.