Dissertations / Theses on the topic 'Sedimentation water treatment'

Tunnels have become increasingly important in the development of road networks to meet rising transportation demands. Washing of road tunnels must be performed regularly to ensure traffic safety. The washing procedure generates significant amount of polluted wash water. Before discharge to a receiving water body, treatment is necessary to avoid potential degradation of the water quality. In this study, 12 in situ sedimentation experiments were conducted to evaluate treatment efficiency of sedimentation, with and without the addition of chemical flocculent. The findings showed that untreated tunnel wash water was highly polluted with total suspended solids (804-9690 mg/l), PAHs (0.4–29 μg/l) and heavy metals. Most pollutants were associated with the particulate material. Significant correlations (r2 > 0.95) were found between suspended solids and metals. Efficient removal of pollutants was possible by sedimentation with addition of flocculent. Within 20 hours of sedimentation low concentrations were reached of suspended solids (<15mg/l), PAHs (<0.1 μg/l), Cd (<0.05 μg/l), Cr (< 8 μg/l), Hg (<0.02 μg/l), Pb (<0.5 μg/l) and Zn (< 60 μg/l). The results confirm the possibility to treat tunnel wash water with sedimentation and flocculation and to discharge treated wash water to a recipient, provided particular attention is given to very sensitive water bodies.

För att simulera aktivslamprocessen på ett reningsverk krävs en dynamisk modell som realistiskt beskriver processen. 1987 kom IWA, International Water Association med ASM1, Activated Sludge model no. 1 som fortfarande är den mest använda modellen för att beskriva denna process. I detta examensarbete har ASM1 används för att beskriva aktivslamprocessen på Henriksdals reningsverk i Stockholm. Arbetet har utförts som en del i ett europeiskt projekt, HIPCON (Holistic Integrated Process CONtrol) på IVL, Svenska Miljöinstitutet AB.

Arbetet har gått ut på att ta fram en modell som realistiskt beskriver aktivslamprocessen och eftersedimenteringen. För att göra detta har en referensmodell i MATLAB/Simulink använts som grund och byggts om för att likna processen vid Henriksdal. Denna modell i Simulink använder ASM1 för att beskriva aktivslamprocessen. Eftersedimenteringen modelleras med en massbalansmodell där sedimenteringshastigheten beskrivs av en dubbelexponentiell sedimenteringsfunktion. Både ASM1 och sedimenteringsfunktionen använder en mängd olika parametrar för att beskriva processerna och dessa måste kalibreras fram för den process som skall modelleras. Aktivslamprocessen är en biologisk process som beror på en mängd yttre och inre faktorer och är unik för varje reningsverk. Därför finns det inte något enkelt sätt att kalibrera en modell på och information för det enskilda reningsverket i fråga måste tas fram. I detta arbete har två mätkampanjer utförts på Henriksdal för att få mätserier till kalibrering och validering samt information om avloppsvattnets sammansättning. Litteraturstudier har också genomförts för att få information om vilka parametervärden som är av störst intresse för modellen samt i vilket område varje parameter kan förväntas finnas.

Arbetet har sedan gått ut på att efter riktlinjer för kalibrering funna i litteraturen ta fram en modell som så realistiskt som möjligt beskriver processen på Henriksdal. Först genomfördes en kalibrering med medelvärden för att hitta jämviktstillstånd och därmed en stabil modell på länge sikt. Utifrån den modellen utfördes sedan en dynamisk kalibrering för att få en modell som beskriver även kortsiktiga och snabba förändringar. Till sist utfördes en validering för att kontrollera om modellen fungerar även för en dataserie som ej använts vid kalibrering. Den framtagna modellen fungerade mycket bra för att modellera medelvärden på lång sikt. För snabba förändringar verkade modellen ligga fel i tiden och troligtvis var den reella uppehållstiden kortare än den teoretiska och bidrar till sämre modellanpassning.

To simulate the activated sludge process at a wastewater treatment plant a dynamic model that describes the process is needed. In 1987 IWA, International Water Association presented ASM1, Activated Sludge Model No.1 which still is the most widely used model for this process. In this thesis the ASM1 has been used to describe the activated sludge process. The work is a part of a European project, HIPCON (Holistic Integrated Process CONtrol) at IVL, Swedish Environmental Research Institute.

The main objective of the work was to calibrate a model that realistically describes the activated sludge process and secondary sedimentation at Henriksdal wastewater treatment plant in Stockholm. A benchmark model in MATLAB/Simulink was used as a base and rebuilt and extended to fit the process of Henriksdal. In the model ASM1 is used to describe the activated sludge process. The settler is modelled with a mass balance model where the settling velocity is described by a double exponential function. The parameters used in both models have to be calibrated to fit the wastewater treatment plant. To find information about Henriksdal two measuring campaigns were performed to provide data for calibration and validation and to gather information about the composition of the incoming wastewater. From this data a model was developed and calibrated for the process at Henriksdal. After calibration the obtained model worked very well for modelling average values but did not adjust quite as well to fast dynamic changes.

I detta projekt har experiment utförts med mål att förse kommunalförbundet Norrvatten med data som kan användas som underlag för beslutsfattande angående om deras fällningslinjer i vattenreningsprocessen ska köras i flotation eller sedimentering. För detta ändamål har koncentrationen av poly- och perfluorerade alkylsubstanser (PFAS) samt karaktär av agglomererade partiklar (flockar) undersökts och jämförts mellan fällningslinjer som körs i olika konfigurationer. För flockkaraktär har skapandet och stabiliteten av flockar varit av intresse, eftersom flotation har ett mer turbulent flöde där flockarna riskerar att brista. Partikelstorlek, storleksfördelning och zeta potential identifierades som egenskaper som reflekterar flockarnas karaktär, dessa analyserades i en zetasizer. Koncentrationen av elva vanligt förekommande PFAS ämnen analyserades i projektet. Resultatet av flockkaraktär tyder på att det ej fanns någon större skillnad i skapandet av flockar samt deras stabilitet mellan de olika fällningslinjerna som undersökts. Detta eftersom zeta potentialen var identisk (-6.45 mV) för de analyserade proverna från respektive process. Analyserna och provberedningen bedömdes ha en hög mätosäkerhet, och några förbättringar som föreslås för att öka säkerheten är genomförande av komplementerande fotoanalys för att bekräfta likheter i utseende mellan flockar, samt att genomföra mer analyser så att en statistisk giltighet av analysen kan kvantifieras. För PFAS koncentrationen så var koncentrationen av PFAS lägre i utgående vatten från fällningslinje som körs i sedimentation (7.5 ng/l), jämfört med prov från linje som körs i flotation (9.2 ng/l). För fällningslinjen som kördes i flotation så skapades skum med höga koncentrationer av PFAS (3800 ng/l) jämfört med analyserade vattenprover (5.5–9.2 ng/l), detta identifierades som en potentiell källa för PFAS-avlägsning. Resultaten av PFAS baserades endast på en provtagningsserie, och förbättringar av validitet kan åstadkommas genom samling av mer analysdata för samma processer, och genom att analysera ett av proverna i två olika instrument, som båda analyserar PFAS koncentration.
In this project, attempts have been made to collect data that allows the municipal association Norrvatten in the decision-making process on the  flotation/ sedimentation step of their water treatment process. In this sense, poly- and perfluorinated alkyl substances (PFAS) concentration and the characteristics of agglomerated particles (flocs) have been investigated and compared between the two modes that the process can be operated. For the floc characteristics, the creation and stability of the flocs were investigated, and the particle size, size distribution and zeta potential was identified as important properties and thereafter analysed using the instrument zetasizer. The concentration of eleven different PFAS compounds were analysed. The results of floc characteristics show that there is no major difference in creation and breakage of flocs in the two investigated modes, since the analysed samples had the same zeta potential, -6.45 mV. The results were deemed uncertain because of varying results, and improvement suggestions include using photoanalysis to confirm similar floc appearances and to produce more data so a statistical validity can be quantified. As for the PFAS concentration, the concentration of PFAS were slightly lower in the treatment step in which sedimentation was utilized (7.5 ng/l) compared to when flotation was utilized (9.2 ng/l). The flotation mode did, however, create foam with a high PFAS concentration (3800 ng/l) compared to the liquid samples (5.5-9.2 ng/l), so a potential PFAS removal source was identified. The results were based on one sample series, so improvements of validity can be achieved by gathering more data, analysing more samples, and analysing the same sample in two different instruments measuring PFAS concentrations.

Many different stormwater control measures (SCMs) can be implemented in order to mitigate issues with polluted stormwater flows into receiving water bodies.  The treatment function of  SCMs is commonly based on the removal of particles by sedimentation, thereby also removing pollutants associated with particles. In recent years, more attention has been given to characterizing and understanding of different particle size fractions and their association with pollutants commonly found in stormwater. It has become increasingly clear that the smaller sized particles are very important pollutant transporters and should be considered when designing and implementing SCMs. However, the settling velocities for smaller sized particles are very low and may not be effectively removed in existing SCMs. One treatment process with a proven ability to enhance sedimentation is coagulation/flocculation, widespread in water and wastewater treatment, but with very few accounts of it being used in a stormwater context. This thesis aims to investigate the treatability of stormwater with a coagulation/flocculation process. This includes the determination of operating conditions, the dominating coagulation mechanism and the reduction efficiency of stormwater related pollutants. The objectives of the thesis were achieved in laboratory tests treating stormwater in a jar-testing procedure. An initial screening of primary coagulants and flocculant aids was conducted using an urban snowmelt mixture. Five of the chemicals were then selected for an extended testing regime which was setup up to determine the operating conditions where maximal turbidity reduction was attained by measuring the pH, conductivity, alkalinity and zeta-potential over the tested doses for each coagulant. Criteria used for chemical selection included high turbidity reduction, low dose requirement and low pH/alkalinity impacts. Charge reversal was observed at positive zeta-potential indicating that the dominating coagulation mechanism was charge neutralization. The content of turbidity/total suspended solids, total organic carbon, total metals and hydrocarbons by >90%. Dissolved copper was reduced by 40% on average, and the reduction rates for dissolved zinc were varying with up to a 300% increase, presumably due to changes in pH, leading to a higher mobility. Changes in the particle size distribution after coagulation/flocculation as compared to sedimentation indicated an effect on the size fraction corresponding to smaller particles. The performance of the coagulation/flocculation process was also tested on road runoff collected from a central road in Luleå with a high traffic intensity. Two coagulants were tested, iron chloride and pre-hydrolyzed aluminum chloride. Reduction rates for the total metal fraction were >90% on average for both coagulants, but for the dissolved metal fractions differences could be observed between the coagulants with the iron chloride resulting in higher reductions for dissolved chrome (57% compared to 34%) and copper (47% compared to 30%). Both products increased the dissolved fractions of nickel and zinc due to lower final pH.

Nessa pesquisa são relatados os resultados da determinação das concentrações de microcistina e de biomassa algal após as várias etapas de tratamento de amostras de água coletadas junto ao reservatório de Barra Bonita-SP visando obtenção de água potável. O tratamento foi realizado em escala de laboratório com e sem aplicação de carvão ativado em pó (CAP) e as etapas foram: coagulação com aplicação de cloreto férrico, sedimentação, filtração em papel de filtro. Foi possível observar que a pré-clarificação desse tipo de água por coagulação seguida de sedimentação requereu dosagens relativamente elevadas de cloreto férrico (80 mg/L), tendo sido verificada eficiência muito baixa de remoção de microcistina nas etapas de tratamento por sedimentação seguida de filtração, quando não foi aplicado CAP. Apenas com a aplicação de CAP a microcistina foi reduzida à níveis que atendessem os padrões de potabilidade previstos na Portaria 518/04 (concentração menor que 1 μg/L). A determinação de microcistina pelo método que utiliza Imunoadsorventes Ligados à Enzima (ELISA) mostrou-se uma ferramenta útil e confiável para detectar e quantificar essa toxina, embora ainda apresente custo relativamente elevado.
This report presents the results of the quantification of microcystins and algae biomass concentrations after treatment of water samples taken from the Barra Bonita reservoir, for production of potable water. Bench-scale tests were carried out with and without powdered activated carbon (PAC) and the treatment processes used were: coagulation with ferric chloride (FeCl3), sedimentation and filtration with paper filter. It was determined that pre-clarification followed by sedimentation required substantial dosages of ferric chloride (80 mg/L). The removal of microcystins using sedimentation followed by filtration was ineffective without PAC. The use of PAC is required to produce water that meets current potability standards for microcystins removal as specified in Decree 518/04 (concentration less than 1 μg/L). Analysis of microcystins using the Enzime-Linked Immunosorbent Assay Method (ELISA) has proven to be an effective and reliable procedure to detect and quantify this toxin, although relatively expensive.

A proposta deste trabalho foi utilizar quatro diferentes coagulantes - sulfato de alumínio, cloreto férrico, hidroxicloreto de aluminio e sulfato ferrico; construir os diagramas de coagulação; e assimilar as regiões de maior ou menor eficiência da remoção de turbidez ou da cor. Para permitir uma avaliação de custos na utilização dos coagulantes, observo-se nos diagramas as regiões onde os valores de turbidez remanescente são aproximadamente iguais para diferentes coagulantes. Com essa consideração, foi stabelecida a relação entre consumo e custo dos produtos quimícos utilizados. Os coagulantes que apresentaram particularidades para as águas estudadas foram: o cloreto ferrico que mostrou melhor desempenho para valores de ph baixos; o sulfato ferrico que mostrou-se mais economico; e o hidroxicloreto de aluminio que atua numa grande faixa de ph. Na conclusão dos estudos, verifica-se que cada água a ser tratada deve ser analisada através de diagramas de coagulação, visando a otimização dos parâmetros de ph versus dosagem e buscando o melhor coagulante pelo menor custo.
The purpose of this study was to use four different coagulants - aluminum sulphate, iron chloride, polyaluminum hidroxichloride and ferric sulphate; to build the coagulation diagrams; and to mark the regions of higher or lower efficiency in the removal of turbidity or color. To allow a cost appraisal in the use of the coagulants, the region where the values of remaining turbidity, which are approximately the same for different coagulants, was examined in the diagrams. This being taken into consideration, the relation between consumption and cost of the chemical products was established. The coagulants that presented certain peculiarities for the studied waters were: iron chloride, that showed better performance for low pH values; the ferric sulphate, that showed itself as more economical; and the polyaluminum hidroxichloride, that functions in a large interval of pH. In the conclusion of the study, it was observed that each type of water to be treated must be analyzed through coagulation diagrams, aiming at the optimization of pH parameters versus dosages and looking for the best coagulant with lower cost.

Магістерська дисертація: стр.59, табл. 11, рис. 11, 88 першоджерел. Мета роботи: оцінка ефективності застосування катіонних та неіоногенних флокулянтів для освітлення стічних вод з високою каламутністю. Об’єкт дослідження: інтенсифікація процесів очищення стічних вод. Предмет дослідження: освітлення зворотної води гірничо-збагачувальних виробництв з допомогою флокулянтів В роботі представлено результати досліджень флокуляційної очистки водних суспензій, з вихідною каламутністю на рівні 5-7 г/дм3. Досліджено основні фізико-хімічні характеристики вихідної води, які впливають на технологічні властивості флокулянтів: природа та гідравлічна крупність завислих речовин, їх концентрація, електрокінетичний потенціал, виконано розширений аналіз води за різними показниками.
Master's Thesis: p. 59, Table 11, fig.11, 88 primary sources. Purpose: to evaluate the efficiency of the use of cationic and nonionic flocculants for high-turbidity sewage treatment. Object of study: intensification of wastewater treatment processes. Subject of research: backwater illumination of mining and processing industries with the help of flocculants The results of studies of flocculation purification of aqueous suspensions with initial turbidity at 5-7 g / dm3 are presented in the paper. The basic physicochemical characteristics of the source water that influence the technological properties of flocculants are investigated: nature and hydraulic size of the suspended substances, their concentration, electrokinetic potential, advanced analysis of water according to various parameters is performed.

No presente trabalho foram realizados estudos para verificar as interferências do lançamento de resíduos de Estações de Tratamento de Água nas Estações de Tratamento de Esgoto com decantação primária. A ETA estudada utilizava cloreto férrico como coagulante primário e possuía decantadores com descarga de fundo diária. As interferências nos decantadores primários da ETE foram simuladas por meio de testes de sedimentação e nos digestores de lodo, por meio de testes de tratabilidade anaeróbia. Testes e análises complementares também foram realizados para verificar eventuais interferências no tratamento biológico da fase líquida do esgoto e no tratamento físico da fase sólida do esgoto. Os resultados indicaram aumento na eficiência de sedimentação em conseqüência do aumento da quantidade e concentração do resíduo de ETA introduzido no esgoto. Obteve-se, por exemplo, um incremento de até 50% na remoção de sólidos suspensos e turbidez, 40% na de DQO e fosfatos e 30% na de nitrogênio. No entanto, obteve-se um maior volume de lodo primário, embora de menos concentrado. De acordo com os resultados dos testes de tratabilidade anaeróbia, os resíduos da ETA não foram tóxicos ao processo. Com relação ao tratamento biológico da fase líquida do esgoto e ao tratamento físico do lodo, não foram verificadas interferências significativas no desempenho dos mesmos, embora recomenda-se o desenvolvimento de pesquisas mais específicas, especialmente sobre o processo de adensamento. Pode-se concluir que resíduos similares aos gerados na ETA estudada poderão ser dispostos em ETEs com decantação primária, sem interferências prejudiciais no seu desempenho.
In the present work simulations studies were conducted to verify the impact of Water Treatment Plants (WTP) residuals on the performance of Wastewater Treatment Plants (WWTP). The WTP under investigation used ferric chloride as primary coagulant, was type Complete Cicle with sedimentation tanks with daily bottom discharge. The interferences in the primary sedimentation tanks were simulated using sedimentation tests, while the sludge digesters were simulated using anaerobic treatability tests. Complementary tests and analysis also were realized to verify eventual interferences in the wastewater biological treatment and in the physical treatment of the sludge. The results indicated an increment in the sedimentation eficiency caused by increasing the WTP residuals dose added into the wastewater. As WTP residuals was added at up to 225 mg dry weight solids per liter of wasterwater, the removal of solids, COD, phosphate and nitrogen, for example, increased in 50%. However, the primary tanks settled sludge volume increased considerably. According to the anaerobic treatability tests results, the WWP residuals had not toxical effects on the process, interfering positively on the methane production. Concerning the wastewater biological treatment and sludge physical treatment, no significant impacts on their performance were observed. Therefore, it can be concluded that conventional WWTP can receive similar WTP residuals as those of the WTP here studied without any negative impacts on their performance.

The goal of this thesis was to determine the operational and technical parameters of the separation objects in water treatment. The first part is a theoretical and provides basic information on this issue. The second part contains the evaluation criteria created by the obtained information for individual objects and gained in practice by personal visits of selected treatment plants of water. In the last part we can find application of these criteria in water treatment in practice. There is also included the final evaluation of the researched condition.

The aim of this thesis was to conduct a survey in selected water treatment plants to identify possible faults with which treatment providers may encounter. Within the thesis has been visited these treatments: ÚV Troubky, ÚV Hosov, ÚV Příkazy, ÚV Černovír. Further was performed evaluation of the collected information, specification and frequency disturbances occurring on those premises.

Proposition d'une nouvelle approche de l'elimination des effluents des ateliers de traitement de surface. Separation zinc/nickel en solution concentree et separation du chrome hexavalent dans des effluents chromates

碩士
國立中央大學
環境工程研究所
96
This study was to investigate turbidity removal and residuals generation in sedimentation and filtration processes of Ping-Jan Water Treatment Plant. Furthermore, physical-chemical characteristics of residuals were also analyzed. According to the statistical data, the probability of raw water turbidity lower than 15 NTU in Ping-Jan Water Treatment Plant was 63%. However, raw water turbidity might higher than 10,000 NTU due to typhoon events. By changing the location of collecting raw water, the probability of turbidity over 10,000 NTU reduced from 4 to 1%. When influent turbidity was between the range of 15 to 500 NTU, the removal efficiency of turbidity and probability of settled water turbidity in sludge blanket clarifiers below 5 NTU were upon 90%. Moreover, the probability of settled water turbidity in tube settlers below 5 NTU was under 60% resulting from improper design of overflow weir when influent turbidity over 15 NTU. In addition, 7 NTU was the limit for the influent turbidity of Hardinge and Wheeler filters. Consequently, 3 and 6 NTU were suggested for these limits, respectively. For coagulation sludge from sludge blanket clarifiers, the SS was 3,955 mg/L, BOD5 was 5 mg/L, and COD was 172 mg/L. In addition, the characteristics of coagulation sludge of tube settlers including 6,262 mg/L SS, 35 mg/L BOD5, and 362 mg/L COD were increased with settled time. The routine amount of coagulation sludge from sludge blanket clarifiers and tube settlers were 1,975 and 2,014 kg/day, respectively. However, sludge production was 73 times of routine amount during typhoon seasons. The analysis results of the filter backwash water (FBW) produced by Hardinge and Wheeler filters revealed that the SS was 252 and 223 mg/L, BOD5 was <1 mg/L, and COD were 17 and 11 mg/L, respectively. FBW was typically only a small fraction of filtered water volume for Harding and Wheeler filters (0.2~0.3% and 1.9~2.5%, respectively). Additionally, the amount of FBW from Wheeler filters was 7~14 times comparing to that from Hardinge filters. When raw water turbidity was below 5 NTU, direct filtration might decrease PAC dosage in coagulation process and reduce the amount of coagulation sludge. Also, changing the strategy of two-stage coagulation sedimentation and adding flocculent while raw water turbidity was over 10,000 NTU might be reasonable. In addition, monitoring turbidity of FBW from Wheeler filters ensure media wasn’t too clean due to too long backwashing. Therefore, it might keep removal efficiency and reduce the amount of FBW of Wheeler filters.

碩士
嘉南藥理科技大學
環境工程與科學系暨研究所
95
In Taiwan, the filter backwash water needs to be recycled back to rapid-mixing tank in most of water treatment plants. However, this process caused several critical problems, including unstable chemicals control and accumulation of microorganism, which seriously affect the treated water quality. In this research, the supernatant of the waste backwash water treated by Dead-end type microfiltration (MF) process combined with coagulation and sedimentation was evaluated. The raw backwash water samples in this research were collected from Tanding Water Treatment Plant, Pingding Water Treatment Plant and Chang-Hwa Third Water Treatment Plant. First of all, water qualities for each treatment plants. First, the raw water qualities were analyzed. And then, several treatment processes were considered and executed, such as coagulation/sedimentation combined with MF Process and direct MF Process. PACl, alum and Chitosan were used as coagulation agents in the coagulation/sedimentation process. In the membrane process, there were two different MF membranes used in this research, including 0.5 µm and 2.0 µm pore sizes, which were filtered by vacuum pump at fixing pressure (0.65 kg/m2). The results indicated that the backwash wastewater from surface water source treated directly by sedimentation only combined with MF process was confirmed to demonstrate the serious scaling problems. However, the water treated by coagulation/sedimentation combined with MF Process (0.5 µm and 2.0 µm pore sizes) reached high efficiency of clean water. Coagulation/sedimentation combined with MF Process specifically for (0.5 µm pore size) executed the optimal result that reached the standards of turbidity, coliforms and total bacterial counts. As the result, this process was considered to be the best one for backwash water reclamation using MF process. This research also executed that the backwash wastewater from groundwater source treated by MF process (0.5 µm and 2.0 µm pore sizes). The result indicated that the 0.5 µm pore size exhibited higher treatment efficiency than 2.0 µm pore size. Moreover, the water quality treated by 0.5 µm pore size reached drinking water standards in turbidity, coliforms and total bacterial counts, no mater combined with filtration only or with coagulation /sedimentation. Therefore, direct filtration combined with MF process (0.5 µm pore size) was consider to be the optimal backwash water reclamation for Chang-Hwa Third Water Treatment Plant.

This diploma thesis is aimed at the evaluation of the efficiency of surface water treatment technology in water treatment plant U svaté Trojice (Kutná Hora, Vrchlice reservoir). The plant performs destabilisation of impurities by coagulant aluminium sulphate (Al2(SO4)3 . 18 H2O) followed by aggregation induced by mixing with perforated baffles. Suspension is removed by double-stage separation process by means of sedimentation and filtration. When increased concentrations of manganese occur in raw water, manganese is removed by means of oxidation by potassium permanganate. Firstly, the quality of raw water was analysed. Then, the reaction conditions for the effective destabilisation (pH, dose of coagulant) were set using the jar tests. Moreover, sedimentation analysis was used to evaluate the properties of formed suspension and the length of filter cycles was assessed. Measurements were conducted between September 2012 and February 2013. Average value of raw water pH was 7.3, alkalinity was 1.64 mmol/l. DOC concentrations during September and October 2012 were equal to 6.7 mg/l and during November 2012 - February 2013 were 7.6 mg/l. Very low concentrations of aluminium (< 0.02 mg/l) were ascertained throughout the whole period investigated. Results of the jar tests showed that the optimum pH for...

The freshwater dinoflagellate species, Ceratium hirundinella (C. hirundinella) possesses unique characteristics, such as a thecal-plate cell covering of cellulose, spines and flagella. Unlike most other algae and cyanobacteria, C. hirundinella cells are relatively large in size (up to 450 μm in length and 50 μm in width). These unique characteristics (e.g. cell covering and flagella) and adaptations (e.g. spines) give the dinoflagellate cells the ability to reduce their sinking rate from the euphotic zone and to migrate easily through the water column. When source water contains high concentrations of C. hirundinella cells, water treatment problems and poor aesthetic water quality can be expected. These water treatment problems may include 1) the disruption of coagulation and flocculation, 2) clogging of sand filters and 3) taste and odour problems when cells penetrate into the final water. In Chapter 9 of this study, a list of operational guidelines (including alert levels) and recommendations to assist managers and operators of plants when C. hirundinella cells are causing water treatment problems. During events of high C. hirundinella concentrations in source water, managers and operators of conventional water treatment plants need strategies to optimize coagulants and unit processes. Thus when source water contains motile nuisance algae, such as C. hirundinella, in moderate or abundant quantities, it is advisable to conduct jar stirring test experiments using both turbidity and total photosynthetic pigment (or chlorophyll-a) analyses as indicators of appropriate coagulant choice and dosages. The aims of this study are summarized as follows:  To optimize coagulants and conventional water treatment processes by implementing relevant algal removal strategies and indicators during jar stirring test experiments,  To investigate the changes in surface charge (known as zeta potential) on C. hirundinella cells before and after adding coagulants as part of the treatment processes,  To investigate the physical and chemical impacts on the morphology of C. hirundinella cells after coagulation, flocculation and sedimentation,  To identify organic compounds that may be responsible for taste and odour problems associated with C. hirundinella,  To investigate the efficiency of pre-chlorination on the removal C. hirundinella cells when dosing various coagulants, and  Give recommendations and operational guidelines relevant for a conventional water treatment plant to improve C. hirundinella removal A combined water treatment system (Phipps and Bird Model), consisting of a six paddle jar test apparatus and six sand filter columns, was used to simulate conventional processes (coagulation, flocculation, sedimentation and rapid sand filtration). Source water samples containing relatively high C. hirundinella concentrations (> 500 cell/mℓ) were collected from Benoni Lake (26º10’50.40’’S; 28º17’50.11’’ E) in plastic containers and stored as a homogenous sample in a 200 litre container under laboratory conditions (± 22 °C). Samples were collected from the source water as well as after sedimentation (from the supernatant or sludge) to determine turbidity, total photosynthetic pigment analyses (chlorophyll) and for phytoplankton analyses. Flocs (containing C. hirundinella cells) were collected from the sludge or sediment for scanning electron microscopy investigations and to perform zeta potential analyses. Concentrated C. hirundinella samples were frozen at -80 °C according to the proposed sampling protocol for organic compound analyses. Results obtained from this study proved that using the relevant indicators to determine the appropriate coagulant dosages during jar stirring tests may generally improve the removal of problem-causing algae, such as C. hirundinella cells. Improved algal removal efficiencies will subsequently ensure final water with good aesthetic quality. The surface charge (zeta potential) on C. hirundinella cells can be used to evaluate the best coagulation conditions within an operating window of -10 mV to +3 mV when dosing various coagulants. Scanning electron microscopy investigations revealed major damaging effects to C. hirundinella cells when dosing high Ca(OH)2 concentrations. However, when dosing lower Ca(OH)2 concentrations, in combination with organic polymer, better C. hirundinella cell removal efficiencies with less damaging effects to cells was observed. This study also indicated that the pre-chlorination, without causing cell lyses, can be applied to render the highly motile cells immobile which will subsequently assist the coagulation unit process. The aesthetic quality (e.g. tastes and odours) of drinking water may be influenced when C. hirundinella cells release organic material into the water as a result of cell lyses. Organic compounds, such as fatty acids and dicarboxylic acids can lead to taste and odour problems which associate with the presence of C. hirundinella. Organic compounds also serve as precursors for the formation of harmful chlorine by-products formed during chlorination.
PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

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.