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Author: Mehrnaz Mirzaei Barzi
Publisher:
ISBN: 9780494437469
Category :
Languages : en
Pages : 210
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Book Description
Over the past century chlorine has been a reliable disinfectant to reduce transmission of waterborne diseases in drinking water. Concerns about chlorination have increased since it was discovered in the 1970s that use of chlorine in drinking water produces trihalomethanes (THMs), when chlorine reacts with natural organic matter (NOM), which has been observed in increased levels in surface water during the past decades. THM and other disinfection by-products (DBPs) such as some of the haloacetic acids (HAAs) and some nitrosamines are considered probable human carcinogens by USEPA. Since DBPs are still formed even when using alternative disinfectants such as chloramines, treatment processes by which disinfection by-product precursors are removed continue to be studied. Many researchers have demonstrated that the use of pre-ozonation/biological processes in the production of drinking water has the potential to decrease levels of disinfection by-products in finished water more than conventional treatment alone. Two of the parameters which affect the efficiency of DBP precursor removal in biofilters are filter media and filter flow rate. In this research, the biofiltration process was examined using pilot-scale filters receiving ozonated water to determine the relative effectiveness of these parameters for influencing the removal of natural organic matter. The research presented in this thesis initially focuses on determining the effects of flow rate and filter media including GAC (granular activated carbon) and anthracite on decreasing the levels of THM, HAA and nitrosamine precursors in biologically active filters. In the second part, the performances of full-scale and pilot-scale filters at the Mannheim Water Treatment Plant were compared. THM and HAA precursor removal was found to decrease when loading rates were increased, likely due to associated shorter contact times in the filters. Also, higher THM and HAA precursor removal was always observed in the GAC filters than in the anthracite filters. However, removal of nitrosamines was not affected by flow rate or the type of filter media. In general, the pilot-scale filter performance was representative of full-scale filter performance, especially in regards to THM precursor and chlorine demand removal. Statistical evaluation and interpretation of the data for HAA and NDMA precursor removal was more difficult, likely due to the low concentrations of these DBPs which was near their method detection limits (MDLs) and also because of some operational problems with pilot filter #1. Despite these limitations, the results of this study add to the literature concerning the use of different types of media to support biofiltration and reduce DBP precursor concentrations during drinking water treatment.
Author: Mehrnaz Mirzaei Barzi
Publisher:
ISBN: 9780494437469
Category :
Languages : en
Pages : 210
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Book Description
Over the past century chlorine has been a reliable disinfectant to reduce transmission of waterborne diseases in drinking water. Concerns about chlorination have increased since it was discovered in the 1970s that use of chlorine in drinking water produces trihalomethanes (THMs), when chlorine reacts with natural organic matter (NOM), which has been observed in increased levels in surface water during the past decades. THM and other disinfection by-products (DBPs) such as some of the haloacetic acids (HAAs) and some nitrosamines are considered probable human carcinogens by USEPA. Since DBPs are still formed even when using alternative disinfectants such as chloramines, treatment processes by which disinfection by-product precursors are removed continue to be studied. Many researchers have demonstrated that the use of pre-ozonation/biological processes in the production of drinking water has the potential to decrease levels of disinfection by-products in finished water more than conventional treatment alone. Two of the parameters which affect the efficiency of DBP precursor removal in biofilters are filter media and filter flow rate. In this research, the biofiltration process was examined using pilot-scale filters receiving ozonated water to determine the relative effectiveness of these parameters for influencing the removal of natural organic matter. The research presented in this thesis initially focuses on determining the effects of flow rate and filter media including GAC (granular activated carbon) and anthracite on decreasing the levels of THM, HAA and nitrosamine precursors in biologically active filters. In the second part, the performances of full-scale and pilot-scale filters at the Mannheim Water Treatment Plant were compared. THM and HAA precursor removal was found to decrease when loading rates were increased, likely due to associated shorter contact times in the filters. Also, higher THM and HAA precursor removal was always observed in the GAC filters than in the anthracite filters. However, removal of nitrosamines was not affected by flow rate or the type of filter media. In general, the pilot-scale filter performance was representative of full-scale filter performance, especially in regards to THM precursor and chlorine demand removal. Statistical evaluation and interpretation of the data for HAA and NDMA precursor removal was more difficult, likely due to the low concentrations of these DBPs which was near their method detection limits (MDLs) and also because of some operational problems with pilot filter #1. Despite these limitations, the results of this study add to the literature concerning the use of different types of media to support biofiltration and reduce DBP precursor concentrations during drinking water treatment.
Author: Fei Feng
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Previous studies have reported that biofilm extracted from full-scale biofilters can serve as nitrogenous disinfection by-product (N-DBP) precursors. Detached biofilm could escape during filter ripening and form N-DBP upon chloramination. This study examined the potential breakthrough of biofilm and N-DBP precursors during filter ripening at two water treatment plants (WTPs). The presence of biofilm was estimated by total adenosine triphosphate levels (tATP); N-DBP formation potential (FP) tests were conducted to quantify N-nitrosodimethylamine (NDMA) and haloacetonitrile precursors. While tATP peaks in filter effluent were observed post backwash at both WTPs, temporary increases of effluent NDMA FP were only observed during filter ripening where particle-associated NDMA precursors served as the dominant contributor. Overall, biofilters examined in this study demonstrated a consistent removal of NDMA FP regardless of the filter ripening process.
Author: Amina K. Stoddart
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Natural organic matter (NOM) is a complex mixture of organic material ubiquitous in natural waters. NOM can affect nearly all aspects of drinking water treatment. It can exert a demand on treatment chemicals, promote regrowth in distribution systems and can form genotoxic and/or carcinogenic disinfection by-products (DBPs) when exposed to disinfectant. Biofiltration is one treatment strategy that has potential to provide additional removal of NOM following coagulation. In biofiltration, bacteria indigenous to the source water form biofilms on filter media and use organic material as an energy source. This type of biological treatment within a filter has advantages over filtration with relatively biologically inert granular media because of its potential to provide additional NOM removal through biodegradation. This thesis investigated conversion of full-scale anthracite-sand drinking water filters to biofilters through the removal of prechlorination. Results showed that filters operated in direct filtration mode could be converted in this way to reduce DBP formation in the plant effluent and distribution system without compromising water quality or filter performance. Biomass monitoring using adenosine triphosphate (ATP) showed that filter media biomass increased as a result of conversion. Further interpretation of the biomass data with a growth model demonstrated that consistency in biomass sampling within the context of the operational state of the filter or following significant process changes was critical information for long-term performance assessment. A concurrent pilot-scale investigation tested nutrient, oxidant and filter media enhancement strategies with the goal of improving NOM removal and further reducing DBP formation. Results showed that nutrient and oxidant addition could increase the filter biomass and alter the microbial community, but would not improve NOM removal or further reduce DBP formation potential. Ultimately, despite reductions in DBP formation and increases in biofilter biomass, NOM removal across the biofilters remained unchanged with conversion and enhancements, posing a challenge for process monitoring. A novel method to measure oxygen demand was optimized for use in a drinking water matrix and used to evaluate NOM removal and transformation in the biofilters.
Author: Douglas M. Owen
Publisher: American Water Works Association
ISBN: 0898679419
Category : Carbon, Activated
Languages : en
Pages : 322
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Book Description
Author: Gerald E. Speitel Jr
Publisher: American Water Works Association
ISBN: 184339930X
Category : Science
Languages : en
Pages : 246
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Book Description
In response to current and anticipated disinfection by-product (DBP) regulations, many utilities have begun to use chloramines as a secondary disinfectant. Chloramination produces DBPs such as haloacetic acids (HAAs), trihalomethanes (THMs), and haloacetonitriles (HANs) in lower concentrations than chlorination. Previous research has demonstrated that dihalogenated haloacetic acids (DXAAs) are the most commonly formed HAAs during chloramination. Some utilities may have difficulty meeting the new maximum contaminant level (MCL) for HAAs because chloramination does not limit the formation of DXAAs to the same extent as it does other DBPs. The objectives of this project were to: better understand the reactivity of key natural organic matter (NOM) fractions and the effects of treatment processes with respect to dihaloacetic acid (DXAA) formation, better delineate the influence of pH and Cl2/N ratio on DXAA formation, characterize DXAA formation kinetics and the impact of treatment processes on the kinetics, especially the impact of prechlorination, calculate the rate and extent of DXAA formation at elevated summer water temperatures, and determine the effect of bromide concentration on DXAA speciation and kinetics.
Author: Caroline Di Tommaso
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Biofiltration can be effective for disinfection by-product (DBP) precursor control, however few studies have considered its role in the potential formation of DBPs. The objective of this study was to determine the contribution of biofilm-related materials to form nitrogen-containing DBPs upon chloramination and to determine the influence of cyclical biofilter operation on DBP precursor removal. Biologically active media was sampled from a full-scale biofilter operating under cold-water conditions (3.6 ± 0.5°C) and its components were extracted with a cation exchange resin into a phosphate buffering solution. N-nitrosodimethylamine (NDMA) and haloacetonitrile (HAN4) formation potential tests conducted on extracted biofilm yielded 0.80 ± 0.27 ng NDMA/g media and 18.7 ± 3.3 ng dichloroacetonitrile (DCAN)/g media. However, an analysis of NDMA formation potential and biological surrogates in the effluent of a full-scale cyclically-operated biofilter did not show release of NDMA precursors during filter start-up after stagnation periods of 6 hours or more.
Author: Scott Berger
Publisher: Amer Inst of Chemical Engineers
ISBN: 9780816908011
Category : Technology & Engineering
Languages : en
Pages : 184
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Book Description
This report details the results of a collaborative project investigating biofiltration as a method to control volatile organic compound (VOC) emissions. The report summarises what is currently known about this technology from literature, as well as from the experience of project team members with biofiltration at the bench-, pilot-, and full-scale levels. The report goes on to define the regime of applicability of biofiltration, and the data that must be gathered during bench- and pilot-scale evaluations. Two database tools on CD-ROM are included in the report to help practitioners identify whether a specific VOC application is a viable candidate for biofiltration.
Author: Mika Sillanpää
Publisher: Butterworth-Heinemann
ISBN: 0128242752
Category : Technology & Engineering
Languages : en
Pages : 374
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Book Description
Natural Organic Matter in Water: Characterization, Treatment Methods, and Climate Change Impact, Second Edition focuses on advanced filtration and treatment options, as well as processes for reducing disinfection by-products, making it an essential resource on the latest breakthroughs in the characterization, treatment and removal of natural organic matter (NOM) from drinking water. Based on the editor's years of research and field experience, the book covers general parameters, isolation and concentration, fractionation, composition and structural analysis, and biological testing, along with removal methods such as inorganic coagulants, polyelectrolytes and composite coagulants. In addition, sections cover electrochemical and membranes removal methods such as electrocoagulation, electrochemical oxidation, microfiltration and ultrafiltration, nanofiltration, and membrane fouling. This book is a valuable guide for engineers and researchers looking to integrate methods, processes and technologies to achieve desired affects. - Provides a summary of up-to-date information surrounding NOM - Presents enhanced knowledge on treatment strategies for the removal of NOM - Covers conventional as well as advanced NOM removal methods
Author: United States. Congress. House. Committee on Science. Subcommittee on Energy and Environment
Publisher:
ISBN:
Category : Law
Languages : en
Pages : 1612
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Book Description
Author: Ahmed Mohamed Elsayed ElHadidy
Publisher:
ISBN:
Category : Biofilms
Languages : en
Pages : 235
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Book Description
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.
