Understanding The Impact Of Assimilable Organic Carbon On Biological Stability And Biofilm Development Within Drinking Water

The increasing occurrence and severity of cyanobacterial harmful algal blooms (HABs) in freshwater have continuously challenged the safe drinking water supply. During HAB, public attention mainly focuses on the cyanotoxins, which associated with health issues, while HAB also generated massive amounts of algal cells, increasing the loading of algal organic matter (AOM) in the drinking water treatment plants (DWTPs). AOM is an algae-derived autochthonous natural organic matter (NOM), which contains high fraction of hydrophilic and nitrogenous compounds. Conventional treatment processes, comprised of coagulation, sedimentation, and granular media filtration, are known to be ineffective in completely removing NOM, including AOM [1, 2]. Although ozone has been widely adopted by water utilities to break down complex organic compounds and reduce DBP formation, ozonation practices can adversely increase concentrations of assimilable organic carbon (AOC), which in turn can be rapidly utilized and support biofilm growth in downstream filters and drinking water distribution systems [3, 4]. Currently, remain largely unknown for the growth of biofilms under the impacts of different NOM, including AOM in the filters and drinking water distribution systems (DWDSs). Therefore, the main research goal of this study is to investigate the impacts of organic matter on microbial biofilms in engineered drinking water systems (EDWSs). Specifically, the first objective of this study aimed to examine how the assembly processes and their associated factors (e.g., influent characteristics, biological interactions) drive the temporal dynamics of bacterial communities in full-scale BAC filters, which underwent ozone implementation to better handle the adverse effects of HABs. The obtained results revealed that along with the increase of bacterial taxonomic richness and evenness, stochastic processes became more crucial to determine the bacterial community assembly in the summer and autumn after ozone implementation. Moreover, their corresponding networks possessed simple network structures with lower modularity than other seasons, which implied lesser biological interactions among bacterial populations. Among the monitored physiochemical properties of filter influents, temperature and nutrient bioavailability (i.e., AOC concentrations) as well as biological interactions can be crucial drivers that impact the balance between these two processes and the taxonomic diversity of bacterial communities in BAC filters. The second objective of this study was to examine the effects of two widely present NOM, treated AOM and humic substances (HS), on biofilm development under unchlorinated DWDS conditions. Although great efforts have been made to remove NOM in DWTPs, remaining NOM still exists in the filter effluent and subsequently enter DWDSs. This unremoved NOM can support the growth of microbial biofilms in DWDS. Thus, the impact of AOM and HS on the formation, chemical composition, and microbial community structures of biofilms was evaluated. The 16S rRNA gene sequencing analyses revealed that the bacterial communities in biofilms were clustered with the organic matter types in bulk water, where Family Comamonadaceae was the most dominant but showed different temporal dynamics depending on the organic matter characteristics in bulk water. Higher diversity was observed in the biofilms grown in AOM-impacted bulk water (BFAOM) than biofilms grown in HS-impacted (BFHS) and R2A-impacted bulk water (BFR2A) as the biofilms matured. In addition, some taxa (e.g., Rhodobacteraceae, and Sphingomonadaceae) were enriched in BFAOM compared to BFHS and BFR2A. The biofilm image analysis results indicated that compared to BFHS, BFAOM and BFR2A had relatively thinner and heterogeneous physical structures with lower amounts of cell biomass, extracellular polymeric substances (EPS), and higher EPS protein/polysaccharide ratios. The third objective of this study was to elucidate how different types of organic matter, including AOM and HS, affect biomolecular compositions of biofilms and subsequent DBP formation. In order to control biofilm formation in DWDS, water utilities apply disinfectants such as chlorine or monochloramines. However, these applied disinfectants can lead to the formation of toxic DBPs due to the presence of organic-rich substances within biofilms. Therefore, the impact of organic matter composition on biomulecular composition of biofilms and their correlations with DBP formation were explored. The obtained results indicated that all biofilm samples comprised mostly of protein-like components (~90%), and to a lesser extent, humic-like components (~10%). Strong correlations were generally found between tryptophan-like substances and the studied DBP formation (R2min ≥ 0.76, P

Maintaining the microbial quality in distribution systems and connected installations remains a challenge for the water supply companies all over the world, despite many years of research. This book identifies the main concerns and knowledge gaps related to regrowth and stimulates cooperation in future research. Microbial Growth in Drinking Water Supplies provides an overview of the regrowth issue in different countries and the water quality problems related to regrowth. The book assesses the causes of regrowth in drinking water and the prevention of regrowth by water treatment and distribution. Editors: Dirk van der Kooij and Paul W.J.J. van der Wielen, KWR Watercycle Research Institute, The Netherlands

Biofiltration is a promising green drinking water treatment technology that can reduce the concentration of biodegradable organic matter (BOM) in water. Direct biofiltration or biofiltration without pretreatment (BFwp) limits the use of chemicals such as coagulants or ozone commonly employed with conventional biofiltration, making BFWP a more environmental friendly pre-treatment. BFWP was proven to be an efficient pretreatment to reduce fouling of low pressure membranes, and can also improve the biological stability of the final treated drinking water to limit bacterial regrowth in the distribution system. One major operational problem for high pressure membranes (i.e. nanofiltration and reverse osmosis membranes) is membrane biofouling due to biofilm growth inside the feed channel of the membrane module, resulting in higher energy requirements and more frequent membrane cleaning. BFWP can potentially be applied to reduce biofouling of nanofiltration membranes, which can reduce the energy requirements of high pressure membranes. Three pilot-scale parallel biologically active filters with different empty bed contact times, and bench-scale nanofiltration membrane fouling simulators, were designed and constructed in this study. A challenging surface water source (the Grand River in Kitchener, ON) was used as source water for the investigation. Initial work assessed the effect of biofiltration on the treated water quality and how the biofilter performance is affected by changes in water temperature. A protocol was developed to better characterize the biofilter attached biomass and extracellular polymeric substances (EPS), in order to understand their possible relationship to biofilter performance. Flow cytometry was applied to measure both planktonic cell concentrations in water and also to perform assimilable organic carbon (AOC) analysis using a natural microbial inoculum. BFWP was found to be an efficient pre-treatment for the removal of large molecular weight biopolymers and AOC over a wide range of water temperatures. Lower water temperatures had a significant impact on biopolymer removal, unlike AOC which was efficiently removed at lower water temperatures, and this proved the robustness of such a pre-treatment technology. Other fractions of the natural organic matter (NOM) such as humic substances, buildings blocks and low molecular weight organics were removed to a lower extent than biopolymers or AOC. Empty bed contact time (EBCT) as a design parameter had a limited effect on the biofilter performance. Most of the observed removal for BOM and total cell count happened at the shortest EBCT of 8 minutes, and increasing the EBCT up to 24 minutes had a significant but less proportional impact on biofilter performance. Regarding biofilter attached biomass, no direct linkage was found between biofilter performance and attached biofilter biomass characteristics using any of the commonly used analytical methods such as adenosine triphosphate (ATP) or biofilm cell count, however, cellular ATP content was found to be indicative of biofilm activity. Biofilm EPS composition was not related to biofilter performance but it was largely affected by the water temperature. Through community level physiological profiling (CLPP) analysis it was evident that the microbial community was changing due to a drop in water temperature, however, this was a minor effect and it is likely that the overall drop in biomass activity was the main reason behind the drop in biofilter performance. Finally, BFWP was tested as a potential pre-treatment technology to control high pressure membrane biofouling, which is a major operational problem. BFWP was able to reduce the amount of available nutrients measured as AOC, reduce the presence of conditioning molecules such as large molecular weight biopolymers, and modify the microbial community of the feed water. A 16 minute EBCT biofilter was able to extend the lifetime of nanofiltration membranes by more than 200% compared to the river water without biofiltration, both at low and high water temperature conditions. The 16 minute EBCT biofilter performance was also comparable to that of a full scale conventional biofilter with prior coagulation, sedimentation and ozonation. The biofiltration pre-treatment efficiently affected the amount of biomass present in the biofouling layer and affected the biofilm microbial community as determined using CLPP analysis. The findings of this study provide the basis upon which further and larger scale testing of the BFWP as a pre-treatment for membrane applications can be done. A sound technology could include a hybrid membrane system with a high pressure membrane proceeded with a low pressure membrane. BFWP can then be used at the start of the treatment train to limit both low pressure membrane fouling at the same time limit the biofouling of the pressure membrane. This treatment train can provide a high water quality with limited footprint compared to conventional treatment trains and long service time. Monitoring of the treatment unit performance can be efficiently done using some of the proposed analytical methods presented in the study, such as AOC monitoring and flow cytometry to study microbiological water quality and biofilter biomass. Fluorescence spectroscopy and size exclusion chromatography can also be used to monitor large molecular weight biopolymers, which are responsible for several operational problems in water treatment in general and specifically for membrane applications.

An updated guide to the growing field of nanofiltration including fundamental principles, important industrial applications as well as novel materials With contributions from an international panel of experts, the revised second edition of Nanofiltration contains a comprehensive overview of this growing field. The book covers the basic principles of nanofiltration including the design and characterizations of nanofiltration membranes. The expert contributors highlight the broad ranges of industrial applications including water treatment, food, pulp and paper, and textiles. The book explores photocatalytic nanofiltration reactors, organic solvent nanofiltration, as well as nanofiltration in metal and acid recovery. In addition, information on the most recent developments in the field are examined including nanofiltration retentate treatment and renewable energy-powered nanofiltration. The authors also consider the future of nanofiltration materials such as carbon- as well as polymer-based materials. This important book: Explores the fast growing field of the membrane process of nanofiltration Examines the rapidly expanding industrial sector's use of membranes for water purification Covers the most important industrial applications with a strong focus on water treatment Contains a section on new membrane materials, including carbon-based and polymer-based materials, as well as information on artificial ion and water channels as biomimetic membranes Written for scientists and engineers in the fields of chemistry, environment, food and materials, the second edition of Nanofiltration provides a comprehensive overview of the field, outlines the principles of the technology, explores the industrial applications, and discusses new materials.

Use this new book to solve water treatment problems related to toxicity, taste and odor, and bacteria regrowth. Influence and Removal of Organics in Drinking Water presents the latest advances in oxidation technologies, ozonation, membrane technology, micropollutant removal, and filtration processes. Fundamental aspects of coagulation, flocculation, adsorption, ozonation, preozonation, and granular activated carbon are discussed. Filtration methods covered include biological filtration, membrane filtration, and ultrafiltration. The book will provide a useful reference for water treatment plant managers and operators, water engineers, water supply managers, and consultants.

In the summer of 1999, an international group of experts convened in Jerusalem, Israel, in order to define the major environmental challenges facing humanity at the dawn of the new millennium and - where possible - propose ways of addressing them. Almost 50 selected articles are collected in the present book, which constitutes a striking interdisciplinary combination of state-of-the-art science with the latest views on environmental law, education, and international cooperation. Whilst a major fraction of the book is devoted to water-related issues (water quality monitoring, water and wastewater treatment, water-based international cooperation, and more), other sections deal with timely topics relating to air pollution, biodiversity, conservation, and education. The book is intended for environmental scientists, professionals, and students of all disciplines.

This book provides a state-of-the-art assessment on a variety of biofiltration water treatment systems from studies conducted around the world. The authors collectively represent a perspective from 23 countries and include academics/researchers, biofiltration system users, designers, and manufacturers. Progress in Slow Sand and Alternative Biofiltration Processes - Further Developments and Applications offers technical information and discussion to provide perspective on the biological and physical factors affecting the performance of slow sand filtration and biological filtration processes. Chapters were submitted from the 5th International Slow Sand and Alternative Biological Filtration Conference, Nagoya, Japan in June 2014. Authors: Nobutada Nakamoto, Shinshu University, Japan, Nigel Graham, Imperial College London, UK, M. Robin Collins, University of New Hampshire, Durham, NH, USA and Rolf Gimbel,Universität Duisburg, Essen, Germany.