Dissertations / Theses on the topic 'Clarification of water'

Orientador: Cassiana Maria Reganhan-Coneglian<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia<br>Made available in DSpace on 2018-08-26T04:53:56Z (GMT). No. of bitstreams: 1 Canale_Ivan_M.pdf: 7288933 bytes, checksum: 93678fbce9055e79b05000fd1cab8c23 (MD5) Previous issue date: 2014<br>Resumo: Estações de Tratamento de Água (ETA) de ciclo completo. Como o volume de ALF pode representar de 3 a 6% do volume de água tratada produzido na ETA, existe interesse cada vez maior no tratamento desse efluente para fins de recirculação junto com a água bruta aduzida à ETA. Entretanto, existe uma preocupação de que essa água residuária possa conter matéria orgânica, sólidos totais, metais, carbono orgânico, precursores de trihalometanos, cistos/oocistos de protozoários ou outras impurezas concentradas durante o processo de filtração. Este trabalho de pesquisa tem como objetivo caracterizar com base em parâmetros físico-químicos, microbiológicos e parasitológicos a água de lavagem de filtros gerada e recirculada na ETA Capim Fino, em Piracicaba / SP - Brasil. Foram avaliadas 12 amostras da água bruta do manancial que abastece a ETA (rio Corumbataí), ALF bruta, ALF clarificada (com o uso de polímeros auxiliares ou por simples sedimentação) e água filtrada da ETA. Para caracterização da ALF foram analisados os parâmetros físico-químicos: cloro residual, cor, turbidez, pH, alumínio solúvel, sólidos totais fixos, sólidos totais voláteis, sólidos sedimentáveis, carbono orgânico total e o potencial de formação de trihalometanos; os parâmetros microbiológicos: coliformes totais, Escherichia coli; e os protozoários patogênicos: Giardia spp. e Cryptosporidium spp. O monitoramento da ALF bruta apontou como principais características físico-químicas deste efluente elevados teores de turbidez, alumínio, carbono orgânico total, sólidos totais (fixos e voláteis), sólidos sedimentáveis e potencial de formação de THM. A clarificação da ALF com polímero aniônico possibilitou a redução na concentração dos diversos constituintes analisados. Giardia spp. foi detectada na água bruta (cinco resultados positivos e concentração de cistos variando de <LMD a 75,0 cistos/litro) e na ALF clarificada (dois resultados positivos e concentração de 50 cistos/litro). A pré-cloração realizada na ETA, bem como o uso de água tratada (clorada) para lavagem dos filtros garantiu praticamente ausência de E. coli na água de lavagem. A avaliação da água filtrada da ETA apresentou resultados em conformidade com a Portaria 2914/2011 (padrão de potabilidade) do Ministério da Saúde, com exceção da turbidez, onde foram observados quatro resultados acima do limite de 0,5 NTU estabelecido pela Portaria (1,53, 0,54 , 0,59 e 0,74 NTU), o que pode indicar um transpasse de partículas no efluente filtrado nos primeiros minutos seguintes à lavagem dos filtros. Não foram detectados E. coli ou protozoários na água filtrada. Diante do fato que a recirculação da ALF clarificada junto com a água bruta está ocorrendo numa vazão de 60 L/s, que corresponde a 4,5% da vazão de água bruta (1300 L/s) e de forma intermitente, provavelmente não deverão ocorrer efeitos indesejáveis ao processo de tratamento ou o comprometimento da qualidade da água tratada. Com intuito de precaução, é importante que seja dada toda a atenção ao tratamento (clarificação) da ALF antes da recirculação, para redução da turbidez a níveis mínimos possíveis e que a recirculação do efluente clarificado seja realizada na vazão de 4,5% ou menor<br>Abstract: Filter backwash water (FBWW) is the largest liquid waste generated in a conventional water treatment plant (WTP). As the volume of FBWW can represent from 3 to 6% of the volume of treated water produced in the WTP, there is an increasing interest in treatment and recycling of this effluent with raw water adducted to WTP. But FBWW would contain concentrated organic matter, total solids, metals, organic carbon, trihalomethanes (THM) precursors, cysts/oocysts of protozoa and other impurities which could be a concern. This research aims to characterize FBWW generated and recirculated in Capim Fino WTP in Piracicaba / SP - Brazil by physico-chemical, microbiological and parasitological analyses. Twelve samples of raw water from the river that supplies the WTP (Corumbataí river), raw FBWW, clarified FBWW (using auxiliary polymers or simple sedimentation) and filtered water were collected and evaluated. The physico-chemical parameters were: residual chlorine, color, turbidity, pH, soluble aluminum, total fixed and volatile solids, settleable solids, total organic carbon and THM potential formation; microbiological parameters: total coliforms and Escherichia coli; and pathogenic protozoa Giardia spp. and Cryptosporidium spp. Monitoring the raw FBWW pointed as the main physicochemical characteristics high levels of turbidity, aluminum, total organic carbon, total solids (fixed and volatile), sedimentary solids and THM potential formation. Clarification of FBWW with anionic polymer resulted in a reduction in the concentration of the various parameters. Giardia spp. was found in raw water (five positive results and cyst concentration ranging from <Minimum Detection Limit to 75 cysts/liter) and in clarified FBWW (two positive results, concentration of 50 cysts/liter). The pre-chlorination performed in the WTP and the use of treated water (chlorinated) for washing the filters virtually assured absence of E. coli in the FBWW. The filtered water were in compliance with the Brazilian drinking water standards, with the exception of turbidity. Four samples were above the maximum limit of 0.5 NTU (1.53, 0.54, 0.59 and 0.74 NTU), which may indicate a passage of particles in the first minutes after the washing of the filters. E. coli and protozoa were not detected in the filtered water. Because of the recirculation of clarified FBWW is mixed with raw water at a flow of 60 L/s, which corresponds to 4.5% of the flow of raw water (1300 L/s) and intermittently, it is probable that no undesirable effects would occur in the treatment and in the quality of the drinking water. It is important that full attention is given to treatment (clarification) of FBWW before recirculation to reduce turbidity to the minimum levels that are possible and that the recirculation of clarified effluent is conducted at a flow rate of 4.5% or less<br>Mestrado<br>Tecnologia e Inovação<br>Mestre em Tecnologia

The thesis deals with the use of dissolved air flotation (DAF) in water treatment technology in the Czech Republic. It summarizes the knowledge gained at pilot plant studies as well as the experience with full-scale flotation units which have been built in potable water treatment plants in the Czech Republic in years 2006-2018. This thesis provides a broad background of experimental studies of a modern separation process, which does have great advantages in the removal of natural organic matter and microorganisms from water in the drinking water treatment industry. In this thesis, there are presented some examples of the excellent efficiency of the microorganisms removal, both under the experimental conditions as well as water treatment plants, which were improved by DAF units installation in full scale. In addition to the high separation efficiency, it is shown, how DAF units could influence the subsequent separation steps as for example filtration through the granular media. The negative influence of the pre-ozonization on the DAF separation efficiency in Hradec Králové WTP is demonstrated too. The results of the pilot experiments support the idea, that the key condition for high removal efficiency is the optimal coagulation process chemistry. Design of pilot experiments was based on the factorial planning theory and some results are discussed in this thesis. The very big portion of the pilot experiments was made for estimating of the full-scale DAF design parameters before the water treatment plants reconstruction phase

Foi pesquisada a aplicação de métodos, em nível de laboratório, através dos quais é possível otimizar, tratar e dispor resíduos de lavagem de filtros de estações de tratamento de água (Caso ETA do rio Descoberto - ETA-RD Brasília). Na clarificação da água de lavagem dos filtros, observou-se o efeito favorável da adição de polímero para melhorar a separação líquido-sólido é, portanto, as eficiências de remoção de turbidez, cor aparente, sólidos suspensos e coliformes totais. Observou-se melhor sedimentabilidade do lodo a ser desaguado. Os ensaios de centrifugação, em escala de bancada, mostraram que o método aplicado auxilia na determinação da dosagem a ser usada numa centrífuga em escala real. Foram avaliados três métodos de disposição do lodo adensado da ETA-RD em ETE: 1) sedimentação com esgoto sanitário e posterior digestão anaeróbia do lodo; 2) Digestão anaeróbia e 3) digestão aeróbia. Os melhores resultados foram obtidos com a digestão anaeróbia. Os estudos realizados mostraram que há diversas alternativas de tratamento e disposição desses resíduos, mas é necessário, sempre que possível, a avaliação das diferentes alternativas para selecionar a(s) mais apropriada(s) a cada caso em particular, pois fatores como custos e disponibilidade de de sistemas ou equipamentos, definirão a aplicabilidade ou não de determinado método.<br>It was researched the application of methods on laboratory bench scale to optimize the reuse, treatment and disposal of wastes from filter backwash of Water Treatment Plant - WTP (WTP-RD Descoberto River, Brasília case). In the clarification process of this waste, favorable effect of addition of polymer for best liquid-solid separation and, thus, better removal efficiencies of turbidity, apparent color, suspended solids and total coliforms was observed. Better sedimentability of the sludge occurred. The centrifugation tests showed that the applied method help on determination of dosagem to be used in full scale. Three methods to dispose thickened sludge of WTP-RD on wastewater treatment Plants - WWTP were evaluated: 1) Sedimentation with domestic sewage and anaerobic digestion of sludge; 2) Anaerobic digestion and 3) Aerobic digestion. Best results were obtained with anaerobic digestion. The results showed that there are alternatives of treatment and disposal of wastes of WTP, but is necessary, if possible, to make the evaluation of this alternatives to select the most appropriate(s) in each case because factors as costs, systems or equipments availability, will define the applicability or not of a particular method.

Made available in DSpace on 2014-12-17T15:01:47Z (GMT). No. of bitstreams: 1 PatriciaGSL.pdf: 4325839 bytes, checksum: ed5182708cd9548f2c8eca5937447cd6 (MD5) Previous issue date: 2008-12-22<br>Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior<br>This work aims to investigate the process of Dissolved air Flotation (DAF) for clarifying water samples with low turbidity using aluminum sulphate and Moringa oleifera seeds as coagulants. The experimental procedure was carried out in a bench scale flotation unit. The influences on the pre-treatment conditions (coagulant dosage and flocculation time) and flotation parameters (superficial application rate and recirculation rate) were evaluated considering the efficiency of the process. The efficiency was evaluated by determining the turbidity of the untreated and treated water samples. The results obtained showed that turbidity reduction can be obtained very efficiently by using DAF and the latter coagulant in low turbidity water. Using aluminum sulphate in pH?s 5.0 and 6.0 better efficiencies were obtained with low concentrations (15 mg/L), achieving values of 92% of turbidity reduction. In the case of use of Moringa oleifera better efficiencies of reduction of turbidity were reported when using a concentration of 50 mg/L in all range of pH?s, achieving 86% of reduction. The zeta potential was also determined, in an attempt to aid comprehension of the coagulation mechanisms involved. The coagulation mechanisms with Moringa oleifera seeds were shown to be adsorption and charge neutralization, as well as adsorption and bridging. Concerning aluminum sulphate, the predominant mechanisms are adsorption and charge neutralization and enmeshment in a precipitate. The results indicate that for low turbidity water, Moringa oleifera seeds could potentially be a viable substitute for aluminum sulphate<br>O presente trabalho tem como objetivo investigar o processo da flota??o por ar dissolvido sob press?o - FAD para clarifica??o de ?guas com baixa turbidez utilizando sulfato de alum?nio e sementes de Moringa oleifera como coagulantes. O procedimento experimental foi realizado em uma unidade de flota??o em escala de bancada. Foram avaliadas as influ?ncias das condi??es do pr?-tratamento (dosagem de coagulante e tempo de flocula??o) e par?metros de processo da flota??o (taxa de aplica??o superficial e taxa de recircula??o) na efici?ncia do processo. A efici?ncia foi avaliada pela determina??o de turbidez nas amostras de ?gua bruta e tratada. Os resultados obtidos mostraram que elevadas efici?ncias de redu??o da turbidez podem ser conseguidas com o uso da FAD em ?guas com baixa turbidez utilizando estes coagulantes. Para o sulfato de alum?nio, nos pHs 5,0 e 6,0 as melhores efici?ncias foram alcan?adas com baixas dosagens (15 mg/L), alcan?ando valores de at? 92% de redu??o. Para a Moringa oleifera, as melhores efici?ncias de redu??o de turbidez foram ? dosagem aproximada de 50 mg/L para todos os pHs, alcan?ando valores de 86% de redu??o. Determinou-se tamb?m o potencial zeta, com o objetivo de auxiliar na compreens?o dos mecanismos envolvidos na coagula??o. Os mecanismos de coagula??o com sementes de Moringa oleifera indicam ser adsor??o e neutraliza??o de cargas e adsor??o e forma??o de pontes. No que diz respeito ao sulfato de alum?nio os mecanismos predominantes s?o adsor??o e neutraliza??o de cargas e varredura. Os resultados indicam que para ?guas de baixa turbidez, as sementes de Moringa oleifera podem ser um substituto potencialmente vi?vel em rela??o ao sulfato de alum?nio

Includes bibliographical references.<br>This dissertation presents a review of relevant literatre to provide a foundational understanding of the concepts, principles, processes and mechanisms involeved firstly in the coagulation of organic colour, and secondly in floc blanket clarification. The dissertation then presents an investigation of the effect of the addition of clay-kaolin-as a process aid, in floc blanket clarification of South African organically coloured natural surface waters.

碩士<br>國立臺東大學<br>教育學系(所)<br>101<br>Abstract This study aimed to clarify the misconceptions of water resources possessed by five second graders, to develop their correct conceptions and values, and to convert the water resources protection into their actual behaviors in daily life. The students’ water resources misconceptions were understood through interviews whose guidelines named “interview guidelines of water resources conceptions” were expert validated. Then, according to their misconceptions, the researcher planned teaching activities with three picture books and films related to water resources as teaching materials. Students’ water resources misconceptions were clarified through discussions and further activities, and finally these students carried out cherishing and sparing water actions in real life. For result analyses and discussion, interviews, teaching observation, teaching logbooks, worksheets, and checklists were applied during this action study. Results revealed as the following. In consideration of design and process of the water resources instruction, 1.The pictorial content can impress the students with their understanding and rehearsal. 2.The questions and answers to the picture books reading can improve students’ observation and thinking and impress them further. 3.Although picture book instructions are complicated and detailed in planning procedures and lengthy in teaching time, the teaching effects are excellent. 4.Students with high academic achievement are willing to involve and enjoy in a variety of teaching activities while others with low academic achievement prefer the picture book teaching. 5.It may help students learn efficiently that designing multi–faceted and appropriate further activities. 6.The teacher can transparently find the puzzles and the key for problem–solving from subsequent review of the video–taped lessons. Students’ learning effects after the water resources instructions: 1.Water resource misconceptions of the students were clarified after teaching them water resource courses, except one student’s conception concerning water formation. Moreover, students’ behaviors regarding cherishing and sparing water were significantly improved. 2.The higher the level of the support and involvement from the children’s family, the better they learn. With respect to the teacher’s professional achievement, the capability of creating the electronic presentation files about the picture books, techniques of asking questions, and employing this action study in education field are improved significantly.

Yes<br>The character of dissolved organic matter (DOM) present in drinking water treatment systems greatly impacts its treatability by coagulation–flocculation. Powdered activated carbon dosing has been suggested to enhance DOM removal when combined with coagulation–flocculation. However, optimising powdered activated carbon (PAC) dosing requires further research. In this study, fluorescence spectroscopy combined with parallel factor analysis (PARAFAC) and liquid chromatography with organic carbon detection (LC–OCD) has been used to characterise DOM removal in three ways: (a) coagulation–flocculation–sedimentation without PAC dosing, (b) PAC dosing prior to- and (c) PAC dosing during coagulation–flocculation–sedimentation treatment. It was shown that only coagulation–flocculation–sedimentation preferentially removed biopolymer and humic substance chromatographic fractions and fluorescent DOM, whereas dosing PAC preferentially removed building blocks and low molecular weight neutral chromatographic fractions. The DOM treatability that was achieved when PAC was dosed both prior to- and during coagulation–flocculation–sedimentation was comparable, but higher than what was achieved without any PAC dosing. Introduction of PAC to the coagulation–flocculation–sedimentation process significantly improved DOM removal, with fluorescent components removed by 97%. This study also highlights that a combination of fluorescence spectroscopy and LC–OCD is essential to track the removal of both, fluorescent and non-fluorescent DOM fractions and understand their impacts on DOM treatability when using different treatment processes. Overall, lower residual DOM concentrations were obtained in the treated water when PAC adsorption and the coagulation–flocculation–sedimentation processes were combined when compared to treating the water with only one of the processes, despite differences in source water character of DOM.<br>The full-text of this article will be released for public view at the end of the publisher embargo on 16 Jun 2021.

Natural organic matter (NOM) is composed of a complex matrix of organic compounds originating primarily from plant and animal degradation products, including both carbon and nitrogen, and is found in all natural waters. The removal of NOM in drinking water treatment plants is of importance as its presence is associated with qualities responsible for adverse aesthetic concerns such as colour, taste, and odour. It can also substantially impact treatment processes, as it has been shown to increase coagulant and disinfectant demand, corrosion and bacterial regrowth in distribution systems, and interfere with adsorption processes. More critically, certain NOM fractions have been identified as being precursors to potentially harmful disinfection by-products (DBPs) which over time can cause a variety of cancers in humans. The goal of this research was to determine the removal of carbon and nitrogen NOM components through a full-scale municipal drinking water treatment plant employing advanced treatment strategies aimed at reducing NOM, including sand-ballasted clarification (SBC), ozonation, and biological filtration (biofiltration). Investigation into the effect of seasonal changes in raw water quality and temperature on process performance, and determination of biofilter biomass quantity and activity were also carried out. The approach used to accomplish these goals involved sampling water and biofilter media from the Holmedale Water Treatment Plant (HWTP), located in Brantford, Ontario over a period of 14 consecutive months. NOM components were identified using a recently developed NOM characterization technique, liquid chromatography-organic carbon detection (LC-OCD), which fractionates NOM based on size and provides information about the concentration of five operationally defined NOM fractions. The fractions include biopolymers, humic substances, building blocks, low molecular weight (LMW) acids & humics, and LMW neutrals. The carbon fraction of NOM was quantified further using traditional water quality indicators, such as total organic carbon (TOC), dissolved organic carbon (DOC), assimilable organic carbon (AOC), ultraviolet absorbance at 254 nm (UVA254), and specific ultraviolet absorbance (SUVA). The nitrogen fraction of NOM was primarily investigated by quantification of inorganic nitrogen forms, such as total nitrogen, nitrate and ammonia. Throughout the sampling campaign, considerable removal of carbon compounds through sand-ballasted clarification was observed. Ozonation led to a substantial increase in AOC, which was anticipated (and for the most part removed through downstream biofiltration). The performance of both sand-ballasted clarification and ozone did not change considerably with seasonal temperature changes. The biofilters were capable of considerable removal of most carbon containing compounds, although the removal of certain fractions, suspected as being biodegradable, was reduced at cold raw water temperatures. Somewhat unexpectedly, no removal of total nitrogen, nitrate, or ammonia was observed through SBC, ozonation, and/or biofiltration. Due to the limited number of peer-reviewed articles on full-scale biofilter biomass characterization, investigation into the biomass quantity, as determined by adenosine triphosphate (ATP), and biomass activity, as determined by fluorescein diacetate (FDA) hydrolysis was undertaken. A review of the available literature demonstrated that the ATP concentration at the surface of active, acclimated biofilters (with granular activated carbon [GAC] or anthracite media) is typically in the order of 102-103 ng ATP/cm3 media. Compared to this benchmark, the biofilters at the HWTP appeared to contain a considerable quantity of active biomass. Nonetheless, results from the literature review and from this investigation demonstrate that no relationship exists between biofilter performance, in terms of organic matter removal, and ATP concentration at the surface of biofilters. Further investigation was also performed to determine if the biomass within the biofilters was receiving sufficient essential nutrients, namely carbon, nitrogen, and phosphorus, for growth. Determination of the carbon:nitrogen:phosphorus (CNP) ratio in the biofilter feed, and comparison to a widely accepted benchmark of roughly 100:10:1, suggested a potential phosphorus limitation. However, good biofilter performance, in terms of AOC removal, biomass quantity, and biomass activity was consistently observed. Still, no relationship between CNP ratio and biofilter performance, biomass quantity, and biomass activity could be identified. Somewhat unexpectedly, raw water temperature did not appear to impact the biomass quantity (ATP), activity (FDA), or the CNP ratio in the biofilter feed. The results from this research provide valuable information to municipal drinking water treatment providers whose plants employ SBC, ozone, or biofiltration. For the HWTP, although seasonal changes in raw water led to decreased biofilter performance for some monitored parameters, overall NOM removal through the plant remained considerable throughout the year. These findings provide insight to municipalities and consultants as it pertains to treatment process selection during the design or upgrade of drinking water treatment plants.

碩士<br>國立臺灣師範大學<br>衛生教育研究所<br>90<br>The main purposes of this experimental study was to apply values clarification approach to make the teaching models of water resource education , and to explore the differences of the effects between values clarification approach and traditional approach. The non-equivalent pretest-posttest control group design was used in this study. Two classes of the 7th grade students from Shuangchi Junior High School in Taipei county were selected as the sample and randomly assigned the experimental（n=34） and control group（n=34）.（There were only two classes in Shuangchi Junior High School .）Meanwhile, one class of the 7th grade students from Kuyan-in Junior High School in Tauyan were selected as the out-of-school control group to detect the possible unexpected effects caused by the interaction between the students of the experimental and the in-school control group（n=31）. There were ninety-nine students in this study. The main findings of this study were as follows： （1）The knowledge of water resource of the subjects mainly came from television（71.7﹪）and then schools’ teachers. （2）Most students didn’t participate in water resource-related activities（60.6﹪）.As to the students taking part in water resource-related activities, there were about twenty-five（24.3﹪）percentage of subjects participated in outdoor teaching activities . （3）There were significant differences of knowledge, attitude, behavior and environmental sensitivity of water resource of the experimental between pretest and posttest. That is, values clarification approach could enhance knowledge, attitude, behavior and environmental sensitivity of water resource of the experimental. While, control group and out-of-school control group showed the opposite results. That is, traditional approach couldn’t enhance knowledge, attitude, behavior and environmental sensitivity of water resource of control group and out-of-school control group. （4）There were significant differences of knowledge, attitude, behavior and environmental sensitivity of water resource of posttest among the experimental, control group and out-of-school control group. And values clarification approach on enhancing knowledge, attitude, behavior and environmental sensitivity of water resource was better than traditional approach. （5）On the atmosphere of class, reflections of the students, values clarification approach was better than traditional approach. The teaching model of values clarification was favorable for students. （6）The teaching model of values clarification approach could promote thinking and creativity of students and impressed the subjects. While traditional approach didn’t. According to main results of this research, we explored that appling values clarification approach to water resource education was helpful to the subjects. The researcher suggested that schools’ teachers could use values clarification approach in water resource education in order to enhance environmental knowledge, attitude, behavior and sensitivity of students.

碩士<br>國立臺灣師範大學<br>環境教育研究所<br>97<br>Abstract The main purpose of this study was to investigate how applying values clarification teaching approach to the Shihmen Reservoir related water resource environmental education could influence the fifth-grade students from Taoyuan County (local school) and Taipei City (non-local school) in terms of their knowledge, attitude and behavior of water resource environment. The researcher worked with a teacher from Taoyuan County and applied same teaching activities to their classes. A total of 59 students participated in this study (32 from the local school and 27 from the non-local school). Data were collected and analyzed quantitatively and qualitatively. Quantitative data were collected from “The Knowledge, Attitude and Behavior of Water Resources Environmental Education Questionnaire” used as the pretest and the posttest, supplemented by descriptive data collected from the class sessions in both schools. The results are summarized as follows: 1. Before teaching, there were no significant differences in the water resource environmental knowledge and behavior in the pretest between students from both local and non-local schools. However, local students outperformed non-local students in the water resource environmental attitude, which reached a significant difference. After teaching, there was a significant difference in the knowledge of water resource environment, for which, non-local students outperformed local students. However, there were no significant differences in students’ attitude and behavior between two schools. 2. Significant differences in knowledge, attitude and behavior of water resource environmental education between pretest and posttest were found for both schools. That is, values clarification approach enhanced students’ knowledge, attitude and behavior of water resource environmental education. 3. No causal relations could be found between students’ performance and their genders, parental socioeconomic statuses and participation in water resource-related activities. 4. Students benefited from values clarification approach when making choices, clarification, and response to watershed related water resources environmental questions. Based on the results, the researcher made suggestions for environmental education advocators, learners, local schools, and future research. Keywords: watershed related water resources environmental education, values clarification approach

Lead is a known toxin, with the ability to accumulate in the human body from as early as fetal development. Lead exposure is known to cause a myriad of health effects which are more prominent among children. Health effects upon exposure can range from renal and heart disease or potentially cancer in adults to neurotoxicity in children. The continued presence of old lead service lines and plumbing in distribution systems as well as lead-containing solders and brass fixtures in homes may contribute lead to drinking water. Recent studies have highlighted the importance of a predictor known as the chloride-to-sulfate mass ratio (CSMR) in controlling lead release. A ratio above 0.5 – 0.6 theoretically increases the aggressiveness of lead leaching in galvanic settings, while a lower ratio controls lead corrosion. A switch in coagulant type could significantly alter the ratio. However, a coagulant switch could also trigger changes in finished water turbidity and organics, including disinfection by-product (DBP) precursors, as well as impact sludge production. Anecdotal evidence from an Ontario water treatment utility suggested the potential applicability of a newly formulated polymer, cationic activated silica (CAS), in improving DBP precursor removal when used in concurrence with a primary coagulant. No previous scientific research had been dedicated to testing of the polymer. The present research had three primary objectives: The first was to investigate the effect of conventional coagulation with six different coagulants on the chloride-to-sulfate mass ratio as it pertains to lead corrosion in two Ontario source waters of differing quality. Additionally, the effect of coagulant choice on pH, turbidity, and organics removal was investigated. The second objective was aimed at testing potential reductions in CSMR and organics that could be brought about by the use of two polymers, cationic and anionic activated silica (CAS and AAS, respectively), as flocculant aids. Finally, the performance of a high-rate sand-ballasted clarification process was simulated at bench-scale to gauge its performance in comparison with conventional coagulation simulation techniques. The first series of jar-tests investigated the effectiveness of CAS as a primary coagulant on Lake Ontario water. In comparison with the conventional coagulants aluminum sulfate and polyaluminum chloride, CAS did not offer any apparent advantage with respect to turbidity and organics removal. Testing of CAS and AAS as flocculant aids was also conducted. Results from a full factorial experiment focused on CAS testing on Lake Ontario water showed that coagulant dose is the most significant contributor to CSMR, turbidity, DOC removal, and THM control. Generally, improvements resulting from CAS addition were of small magnitude (<15%). Reductions in CSMR were attributed to the presence of the sulfate-containing chemicals alum and sulfuric acid in the CAS formulation. Testing of sulfuric acid-activated AAS on Grand River water showed that pairing of AAS with polyaluminum chloride provides better results than with alum with respect to DOC removal (39% and 27% respectively at 60 mg/L coagulant dose). Highest turbidity removals (>90%) with both coagulants were achieved at the tested coagulant and AAS doses of 10 mg/L and 4 mg/L respectively. CSMR reductions in the presence of AAS were also attributable to sulfate contribution from sulfuric acid. Bench-scale simulation of a high-rate sand-ballasted clarification process on Grand River water showed comparable removal efficiencies for turbidity (80 – 90% at 10 mg/L), and DOC (30 – 40% at 50 mg/L). Finally, six different coagulants were tested on the two source waters for potential applicability in CSMR adjustment in the context of lead corrosion. The two chloride-containing coagulants polyaluminum chloride and aluminum chlorohydrate increased CSMR in proportion to the coagulant dose added, as would be expected. Average chloride contribution per 10 mg/L coagulant dose was 2.7 mg/L and 2.0 mg/L for polyaluminum chloride and aluminum chlorohydrate, respectively. Sulfate-contributing coagulants aluminum sulfate, ferric sulfate, pre-hydroxylated aluminum sulfate, and polyaluminum silicate sulfate reduced CSMR as coagulant dose increased, also as would be expected. The highest sulfate contributors per 10 mg/L dose were pre-hydroxylated aluminum sulfate (6.2 mg/L) and ferric sulfate (6.0 mg/L). The lowest CSMR achieved was 0.6 in Lake Ontario water at a 30 mg/L dose and 0.8 in Grand River water at a 60 mg/L dose. Highest DOC removals were achieved with the chloride-containing coagulants in both waters (35 – 50%) with aluminum chlorohydrate showing superiority in that respect. DOC removals with sulfate-containing coagulants were less, generally in the range of 22 – 41%. Specificity of critical CSMR values to source water needs to be investigated. Additionally, long term effects of sustained high or low CSMR values in distribution systems need to be further looked into. Finally, the effect of interventions to alter CSMR on other water quality parameters influencing lead corrosion such as pH and alkalinity still represent a research deficit.