Application of DVC-FISH method in tracking <i>Escherichia coli</i> in drinking water distribution networks

Sporadic detection of live (viable) <i>Escherichia coli</i> in drinking water and biofilm with molecular methods but not with standard plate counts has raised concerns about the reliability of this indicator in the surveillance of drinking water safety. The aim of this study was to determine spatial distribution of different viability forms of <i>E. coli</i> in a drinking water distribution system which complies with European Drinking Water Directive (98/83/EC). For two years coupons (two week old) and pre-concentrated (100 times with ultrafilters) water samples were collected after treatment plants and from four sites in the distribution network at several distances. The samples were analyzed for total, viable (able to divide as DVC-FISH positive) and cultivable <i>E. coli</i>. The results showed that low numbers of <i>E. coli</i> enters the distribution sytem from the treatment plants and tend to accumulate in the biofilm of water distribution system. Almost all of the samples contained metabolically active <i>E. coli</i> in the range of 1 to 50 cells per litre or cm² which represented approximately 53% of all <i>E. coli</i> detected. The amount of viable <i>E. coli</i> significantly increased into the network irrespective of the season. <br><br> The study has shown that DVC-FISH method in combination with water pre-concentration and biofilm sampling allows to better understand the behaviour of <i>E. coli</i> in water distribution networks, thus, it provides new evidences for water safety control

Separation of reducing sugars from lignocellulosic hydrolysate: Membrane experiments & system dynamic modelling

Separation of fermentable sugars after hydrolysis of lignocellulosic biomass plays a vital role in second-generation biofuel production. Byproducts and solid fractions generated during pretreatment and hydrolysis can have adverse effects on fermentation efficiency. Previous studies have shown that a maximum of 40% (w/w) of sugar yield can be obtained by sequential UF and NF permeate recovery. This study aimed to introduce a multi-step membrane filtration process to recover fermentable sugars while removing inhibitory bi-products. Fermentable sugar recovery was investigated using a recirculation flow between various stages of separation. The experimental results demonstrated that by introducing NF permeate recirculation to the UF unit a sequential UF/NF system can achieve 60% (w/w%) recovery of reducing sugars. Based on the experimental results, a ‘Simultaneous ultrafiltration and nanofiltration model’ was developed using system dynamics. The model was used to predict the final sugar concentration and sugar yield using sugar permeability in each membrane as the dynamic variability. The model predicts that high sugar permeability (or selective permeability) through the ultrafiltration mostly affects the efficiency of the system, which still is a challenge

ON-LINE DRINKING WATER CONTAMINATION EVENT DETECTION METHODS

A task of water supply systems is to provide safe drinking water to every customer, which is a basic human need. Aging of water supply networks and increased precaution of terrorism risks led to re-evaluation of drinking water supply system reliability and vulnerability to accidental and intentional contamination. Contamination of drinking water can cause health, social, psychological and economic issues. During the last decade, early warning systems (EWS) were often used to ensure the safety of drinking water. EWS are driven by conventional sets of drinking water quality sensors, and the collected data are analyzed in real time. For detection of contamination events, numbers of algorithms have been developed. Most of the algorithms are based on statistical analysis or machine learning. The aim of this study was to compare existing methods and to identify the method, which is suitable for contamination detection in drinking water from non-compound specific sensors and requires relatively low computational resource. A detailed review of 11 different algorithms was presented in the current study with the primary focus on detection probability. Cluster analysis in combination with Mahalanobis distances of feature vectors and Canonical correlation analysis (CCA) approach were selected as the most promising methods for application in a new generation of EWS to detect and classify possible contamination events and agents. While canonical correlation analysis method was the most accurate for detection of contamination events, an advantage of Mahalanobis distances was that it not only detects the contamination events but also could identify the type of contaminant. In this study, we conclude that CCA and Mahalanobis distance methods might be applied for detection of contamination events with relatively high and reliable precision

Effect of biostimulation on biodegradation of dissolved organic carbon in biological filters

The addition of labile organic carbon (LOC) to enhance the biodegradation rate of dissolved organic carbon (DOC) in biological columns was studied. Acetate standard solution (NaAc) and Luria Bertrani (LB) medium were used as LOC as biostimulants in glass column system used for measurements of biodegradable dissolved organic carbon (BDOC). The addition of LOC related with the increase of total DOC in sample. The concentration of BDOC increased up to 7 and 5 times and was utilized after 24 min. contact time. The biodegradation rate constant was increased at least 26 times during adaptation-biostimulation period. There was a strong positive correlation between the biodegradation rate constant and the concentration of BDOC. Biostimulation period ranged from 24 to 53 h for NaAc biostimulant and from 20 to 168 h for LB. The study has shown that LOC could be used as stimulator to enhance the biodegradation rate of DOC during biofiltration

Photocatalytic Activity of TiO2 Coatings Obtained at Room Temperature on a Polymethyl Methacrylate Substrate

Titanium dioxide (TiO2) coatings have a wide range of applications. Anatase exhibits hydrophilic, antimicrobial, and photocatalytic properties for the degradation of organic pollutants or water splitting. The main challenge is to obtain durable anatase nanoparticle coatings on plastic substrates by using straightforward approaches. In the present study, we revealed the preparation of a transparent TiO2 coating on polymethylmethacrylate (PMMA), widely used for organic optical fibres as well as other polymer substrates such as polypropylene (PP), polystyrene (PS), and polycarbonate (PC). The films were spin-coated at room temperature without annealing; therefore, our approach can be used for thermo-sensitive substrates. The deposition was successful due to the use of stripped ultra-small (<4 nm) TiO2 particles. Coatings were studied for the photocatalytic degradation of organic pollutants such as MB, methyl orange (MO), and rhodamine B (RB) under UV light. The TiO2 coating on PMMA degraded over 80% of RB in 300 min under a 365 nm, 100 W mercury lamp, showing a degradation rate constant of 6 × 10−3 min−1. The coatings were stable and showed no significant decrease in degradation activity even after five cycles. © 2022 by the authors. --//-- This is an open access article Iesalnieks M, Eglītis R, Juhna T, Šmits K, Šutka A. "Photocatalytic Activity of TiO2 Coatings Obtained at Room Temperature on a Polymethyl Methacrylate Substrate", Int J Mol Sci. 2022 Oct 26;23(21):12936. doi: 10.3390/ijms232112936 published under the CC BY 4.0 licence.European Union’s Horizon 2020 FET Open program under Grant Agreement No. 899528; Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2

Comparison of phosphorus removal efficiency of conventional activated sludge system and sequencing batch reactors in a wastewater treatment plant

The aim of this study was to evaluate the effectiveness application of sequencing batch reactors (SBRs) for phosphorus removal compared to the conventional activated sludge (CAS) treatment system. The results showed that the removal efficiency of phosphorus reached about 99% at wastewater treatment plant with CAS system. At the same time, the maximum phosphorus removal efficiency can be achieved to 88% if the SBRs system operating parameters are optimized. Finally, this study demonstrated that even if granules are not fully developed, the SBR system is working with a good efficiency

Management of wastewater from landfill of inorganic fiberglass

ArticleSustainability is one of the key factors in smart environment management and include the reduction of environment footprint. The waste and wastewater management plans are aimed on actions to reduce the amount of waste and environmental pollution. This includes collection of waste, logistics, storage, processing or valorisation and also treatment. The aim of this research was to evaluate environmental pollution risk and to demonstrate one of the wastewater management schemes to reduce the pollution level. Evaluation of the better management scheme was performed in one of the landfills in Latvia, where fiberglass waste and other inorganic waste is stored. Onsite evaluation results demonstrated the need to develop a better wastewater management scheme of inorganic fiberglass landfill. After that, laboratory–scale experiments for conventional coagulation and biodegradation tests have been performed for efficient management

APPROBATION OF MICROBIALLY AVAILABLE PHOSPHORUS (MAP) DETERMINATION METHOD BY FLOW CYTOMETRY

Phosphorus (P) is among the most important nutrients required for bacterial growth. It has a great influence on microbial activity even at very small concentrations. Existing chemical methods are not able to determine P at low enough concentrations and to quantify biologically available phosphorus fractions. Therefore, a method of microbially available phosphorus (MAP) determination is used to quantify the amount of P at concentrations below 20 µg/l. Additionally, this method determines the amount of P that can be directly used by microorganisms. Originally it was determined by inoculating sample by Pseudomonas fluorescens (now Ps. brenneri) P17 strain and spread-plated on R2A agar for enumeration. Further, a more rapid method was developed by replacing heterotrophic plate count (HPC) by flow cytometry (FCM). In this paper the use of FCM for MAP determination is validated and compared with HPC method. The results of calibration are presented. The original pure P17 strain was used as inoculum and standards with different PO4-P concentrations were inoculated at 30°C. The gained yield factor by FCM was 1.59x108. FCM results showed strong correlation (R2=0.99) with HPC results, as pure culture was used. Therefore, flow cytometry is a rapid alternative to heterotrophic plate count method for microbially available phosphorus determination

ALTERNATIVE UV LIGHT SOURCES FOR SURFACE DISINFECTION

Mercury UV-C light sources are long known to be efficient for microbial inactivation and have been widely used. At the same time, the radiation, if used in inappropriate doses and spectral regimes, can also cause harmful effects to human tissue. The aim of the study was to evaluate the applicability of the novel UV light sources from thallium – antimony at different UV-C. For the research specially made light sources were produced. The influence of UV-C radiation in the range of 200 - 280 nm was tested on Gramnegative bacterium Escherichia coli, both with mercury and thallium. More than 99.99 % inactivation of E. coli cells was obtained after 10 min contact time for thallium – antimony UV-C light source, demonstrating the potential of the produced lamps

Monitorização em contínuo da qualidade microbiológica da água e biofilmes associados utilizando um sistema de células de fluxo

A VIMÁGUA, Empresa de Água e Saneamento de Guimarães e Vizela E.I.M., criada em 19 de Fevereiro de 2002, tem por missão o abastecimento de água para consumo humano. Como tal, a manutenção da qualidade da água potável desde a estação de tratamento de água até aos consumidores é uma das nossas preocupações. Contudo, os sistemas de distribuição de água potável estão continuamente expostos a um fluxo de matéria orgânica biodegradável e de microrganismos. Estes últimos podem formar estruturas nas paredes das condutas – biofilmes – que lhes permite uma maior resistência à desinfecção. Com o propósito de monitorizar a formação de biofilmes e a sua interacção na qualidade da água instalou-se um sistema de amostragem in situ – reactor de células de fluxo - para a monitorização da formação de biofilmes em sistemas de água potável, e testar métodos de detecção de microrganismos patogénicos. Ao longo do tempo foi monitorizado o número de bactérias cultiváveis e totais, assim como parâmetros físico-químicos da água que abastecia o reactor. Em paralelo, foram desenvolvidas sondas de PNA para a detecção rápida de vários microrganismos (Escherichia coli; Helicobacter pylori) e testadas em laboratório, estando já a ser aplicadas no sistema de células de fluxo.Os autores gostariam de agradecer o apoio financeiro concedido pela FCT (Bolsa de doutoramento SFRH/BD/4705/2001) e pelo projecto europeu SAFER (Contrato n°EVK1-CT-200200108).info:eu-repo/semantics/publishedVersio