The Role of Zeta Potential in the Optimization of Water Treatment
Abstract and Figures
Drinking water is typically treated to remove contamination, both mineral and organic. Zeta potential provides a measurable value to monitor optimal water clarification capabilities. Optimal conditions for water production can be obtained by monitoring zeta potential, turbidity, and flocculating agent concentration.
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... The Al and Fe salts are the main coagulants consumed in water treatment industry. In the other studies alum, polyaluminum ferric chloride (PAFCl), Al 13 polymer, and polyaluminium chloride (PACl), ferric chloride, and ferric sulfate were wildly used to remove humic acid and turbidity . ...
... These values indicated the high surface charge of the coagulants as well as their strong ability to neutralize charges. In similar studies, zeta potential values to remove humic acid and turbidity using alum, ferric sulfate, ferric chloride, Al 13 polymer, and PACl were reported near zero in optimum conditions [7,19,20,34]. These result were in agreement with the current study observations. ...
... Table 2 shows that the ORP values of Zamzam water increased to -58.7 mV, probably redox potential varied with type of microbial contamination of water (Okouchi et al., 2002). Certain studies have demonstrated that the ORP value of healthy human biological fluids, such as oral fluid and mother's milk, have an ORP of -7 (Nobbmann et al., 2010;Rael et al., 2009;USP, 2005;Okouchi et al., 2002). Therefore, a negative ORP value helps in the maintenance of healthy body physiology. ...
The objective of the study was to evaluate the quality of Zamzam water, holy water for Muslims and consumed for its medicinal value. The present study demonstrates the physicochemical characterization and wound healing property of Zamzam water. The physicochemical characterization of Zamzam water samples was analyzed for dissolved oxygen, pH, conductivity, total dissolved solids, redox potential, zeta potential, polydispersity index, and zeta size. The microbial quality of Zamzam water was also assessed by exposing water samples to open air. In this work, Zamzam water was also screened for the medicinal value through wound healing properties in Wistar rats. Zamzam water exhibited a unique physicochemical characterization with high levels of dissolved oxygen, zeta potential, polydispersity index, redox potential, total dissolved solids, and conductivity before exposure to open air. After open air exposure, Zamzam water resisted the growth of bacteria. The wound healing properties of Zamzam water in vivo showed a 96% of healing effect on 12th day observation. The wound healing was achieved by modulating pro-inflammatory cytokine such as interleukin -1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor -α (TNF-α). Followed by the level of apoptosis markers caspase-9 and caspase-3 were reduced. The present study proved that Zamzam water is a good-quality water and showed excellent wound healing property. Therefore, Zamzam water can be used for pharmaceutical formulations.
... Further increase in ferric chloride dosage could lead to the restabilization of oil droplets resulting from the excessive presence of cations . The overdose of FeCl 3 led to a charge reversal as the initially destabilized oil droplets underwent secondary adsorption of FeCl 3 , which leads to restabilization . Although the optimal oil removal efficiency of 87.5% was acceptable, it was achieved at a very high dosage of ferric chloride. ...
Dissolved air flotation (DAF) is a separation technology widely used in the industry to reduce oil concentrations in wastewater. However, there are some issues with the existing DAF system, including high chemical cost, environmental pollution by chemical residual in the effluent, and generation of non-biodegradable sludge. In this study, an environmentally friendly and cost-effective DAF process was proposed and tested for separating emulsified oil from water. A hybrid coagulant/flocculant system with ferric chloride as a coagulant and chitosan as a bio-degradable flocculant was used to enhance the efficiency of oil/water separation. The findings of this study showed that the hybrid configuration led to (i) 37% reduction in chemical costs (ii) 90% reduction in the use of non-biodegradable ferric chloride and (iii) 50% reduction in flocculator footprint when compared to individual coagulants. This proposed dosing strategy also has a broader operating pH range between 5 and 9 and wider applicability for both fresh and high salinity water. The results from this study contribute to the wider, environment-friendly, and cost-effective application of air flotation for oil/water separation.
... Zeta potential (surface charge) has been used in water treatment processes for many years to help determine coagulant dosages that depend on the charge of the suspended particles, pH, and conductivity . Zeta potential is a measure of the electrical potential between particles, showing the repulsive interaction between particles; a zero zeta potential means that the particles in the water are unstable, that is, the conditions for aggregation are maximized . ...
Hemodialysis (HD) centers in Baghdad show high endotoxin concentrations. This reflects the removal of endotoxin was not under consideration in the dialysis units. The objective of this research is to evaluate several treatment processes to eliminate free endotoxin released from the ruptured cell wall of gram-negative bacteria in dialysis water. The studied treatment options include ultraviolet (UV), ultrafiltration membrane (UF), and zeta potential control was employed to improve the efficacy of the UF. Hybrid treatment was also considered by joining two or more of the above treatments. A lab-scale unit was built to implement the experiments and synthetic water (feed solution) was prepared with a known level of endotoxin (0.48 EU/mL). The test for Limulus amebocyte lysate was used to assess concentrations of endotoxin in treated water. The observed experimental results showed significant changes in the zeta potential of endotoxins when compared with both (UV alone) and (UV and UF). This kind of treatment reduced the concentration of endotoxin to 0.24 EU/mL by enhancing UF efficacy through zeta potential control and UV treatment. This study serves as a basis for applying physical treatment methods to the currently used water treatment techniques to produce dialysis water in compliance with the international dialysis fluid quality standards.
... A sample was drawn off after settling for 5 min for dissolved nutrient testing and measurement of zeta potential. Zeta potential is a measure of the electrostatic charge repulsion and attraction between particles and can be used to monitor coagulant dosing efficiency (Nobbmann et al., 2010). The coagulant dose was incrementally increased and new batch volumes started until a neutral zeta potential was reached. ...
The objective of this research was to assess specific side-stream treatment processes for biodegradation and precipitation of dissolved nutrients in dewatering centrate. In this study, characterization was made of a conventional suspended growth deammonification treatment process for transforming dissolved polyphosphate (poly-P), dissolved organic phosphorus (DOP) and dissolved organic nitrogen (DON) in two types of dewatering centrate. The deammonification process was configured as a sequence batch reactor (SBR), combining partial nitrification and anaerobic ammonia oxidation (anammox) in a single tank. The first centrate feed studied was from the full-scale Annacis Island wastewater treatment plant (AIWWTP) located in Metro Vancouver, Canada. The second centrate feed was from a lab-scale anaerobic digester (AD) fed waste sludge from the existing City of Kelowna Wastewater Treatment Facility (KWTF), located in the Okanagan Valley, Canada. In addition, poly aluminum chloride (PACL) dosing was assessed for final polishing of dissolved nutrients. The deammonification SBR (DeSBR) process showed similar treatment characteristics for both the KWTF and AIWWTP centrates with excellent DON removal and poor non-reactive dissolved phosphorus (NRDP) removal. A statistical comparison of the DOP and poly-P through the DeSBR process suggests that DOP has a higher biodegradation potential. Future research focused on understanding the variables associated with degradation of DOP could lead to better NRDP removal through deammonification processes. Utilization of a post-anammox PACL chemical dosing stage can achieve the objective of precipitating any residual DON and NRDP and producing an effluent that has lower dissolved nutrients than the pre-digestion KWTF dewatering centrate scenario.
. Науковий супровід заходів, спрямованих на забезпечення централізованим водопостачанням сільських населених пунктів, був покладений на Відділ сільськогосподарського водопостачання УкрНДІГіМ (нині ІВПіМ НААН), починаючи з 1991 р. Головним завданням цього підрозділу Інституту стала розробка науково-технічних рішень для надійного забезпечення всіх споживачів у сільській місцевості водою в потрібній кількості, належної якості та з необхідним вільним напором при мінімізації капітальних і експлуатаційних витрат, раціональному та економному витрачанні водних ресурсів і захисті довкілля від забруднення стічними водами. Одним із головних фундаментальних теоретичних питань, які потребують подальшого розвитку, є нові підходи у теорії фільтрування. Так, з часів Д.М. Мінца відбувся застій цього напряму. Особливо це відчувається у вітчизняних розробках, при тому що відбувся суттєвий прорив у створенні фільтрувальних матеріалів (головним чином це стосується фільтрувальних матеріалів, легших за воду, які у часи Д.М. Мінца взагалі не використовували). Так само відбувся прорив у розвитку вимірювальної апаратури і вона зараз дозволяє вимірювати електрокінетичні і розмірні характеристики колоїдів вихідної води і зерен фільтрувального завантаження, а це обумовлює можливість розглядати процес фільтрації, і особливо адсорбції колоїдів на поверхні зерен фільтрувального завантаження, вже під іншим кутом зору. Результати наукових досліджень, виконаних у лабораторії сільськогосподарського водопостачання за 28 років її існування, впроваджені на діючих локальних і групових сільськогосподарських водопроводах. Матеріали наукових досліджень опубліковані в 4-х монографіях і понад 100 статтях і тезах доповідей у вітчизняних і зарубіжних збірниках. Запропоновані рішення запатентовано у 46 патентах на винаходи. Із використанням наукових досліджень колективу лабораторії було захищено 3 докторські (Хоружий В.П., Новохатній В.Г. і Чарний Д.В.) і 14 кандидатських дисертацій.
The relevance of research. The analysis of the aqueous suspension filtration initial stage through clean polystyrene foam filtration media carried out. Such feature of its work as hydro-sorting is considered. The degree of imbalance and interaction with other electrostatic systems in aqueous suspension determines the layer of potential-forming ions, which is formed around the core of the system. It determines system’s sign and most of the electrical double layer charge. It is usually determined using a physical quantity such as electrostatic or ζ-potential. The aim of this work is to determine the electrostatic properties of polystyrene foam granules and the degree of influence on the process of retaining various nature colloidal particles on their surface when filtering an aqueous suspension through them. Research results. The relationship between the sizes of polystyrene foam granules and the concentrations of electrostatic charge on their surface analyzed. Using the Poison-Boltzmann theory, a relationship between an electrostatic charge and an electric double layer of polystyrene foam granules in aqueous suspension showed. The importance of the ζ-potential researching for controlling of colloidal suspensions filtering process substantiated. The electrostatic properties of different morphology colloids studied. Analysis of research data confirms the hypothesis of a very close connection between the various morphologies colloids ζ-potential magnitude and their electric double layer interaction force with electric double layer of polystyrene foam granules in an aqueous suspension. This means that the polystyrene foam filter “charging” time is closely connected to the values of colloids ζ-potential in the filtered aqueous suspension. Conclusions. The initial filtration stage through clean polystyrene foam media is significantly different from the main stage of filtration due to the electrostatic interaction forces predominance. The time difference of the colloidal crusts complete formation completion on polystyrene foam granules of different diameters is so insignificant that it can be neglected and this time is considered the same for polystyrene foam granules of different diameters. Regardless of the origin nature, the retention intensity of the colloids by polystyrene foam filtration media granules and, consequently, the polystyrene filter “charging” time is directly depends on their z-potential value.
Wastewater from dairy manufacturing generally contains high concentrations of organic compounds and high biological oxygen demand (BOD). Existing treatment technologies have not always fully delivered the desired effluent standards and they can also be expensive. This study proposes to recover the organic components (proteins, lipids and carbohydrates) from alkaline dairy waste streams using ferric chloride (FeCl3) as a low-cost food grade inorganic precipitant. Ninety-nine percent of sample turbidity was removed, 80% of protein was recovered and 80% of BOD was reduced at optimum conditions (pH 10.0, FeCl3 concentration of 0.07% w/v). In alkaline conditions, Fe³⁺ ions effectively neutralised negatively charged colloidal particles leading to coagulation and sweep flocculation. This method was highly effective under alkaline but not under acidic condition. At the optimum conditions, 27% of total fat, 16% of total carbohydrates and 39% of total calcium were also precipitated and recovered upon 2 h of settling. The final pH of the treated water self-neutralized to 7.0 and the iron content was reduced to 1 ppm. The treated water may be used for certain applications and the recovered organic components are suitable for animal feed stock.
The Fort Collins Water Treatment Facility (Colorado) is a 70‐mgd (270‐ML/d) plant that uses two raw water sources: Horsetooth Reservoir, and the Cache la Poudre River. Due to water rights, the treatment plant desires to treat 100 percent Poudre River water during the period of spring snowmelt, when the river is at peak flow. Due to the challenging water quality of the river during runoff, the plant has been forced to blend river water with that of the reservoir to meet its in‐house finished water quality standards. To avoid blending and to treat 100 percent of the source water, it was necessary to conduct extensive bench‐ and pilot‐scale experiments to develop the desired process chemistry. The results presented here are the culmination of three runoff seasons' worth of experiments.
A full-scale case study is presented where coagulation of water characterized by high total organic carbon (TOC) concentrations is optimized using measurements of zeta potential. Each spring, snowmelt runoff water percolates through the forest floor of the Cache la Poudre River (Poudre River) watershed resulting in high TOC, low alkalinity water that must be treated by the City of Fort Collins, Colorado, Water Treatment Facility (FCWTF). During the 2005 snowmelt runoff period, the raw Poudre River TOC ranged up to 13 mg/L, with the TOC at or above 8 mg/L for 23 days. The increased TOC is predominantly made up of humic substances that control the coagulant demand. Modification of the coagulation process to treat this water at the FCWTF consists of conditioning the raw water with a 30% lime slurry and carbon dioxide gas prior to alum addition in order to achieve a coagulated water pH within the range of 6.5 to 6.8. The rapidly changing water quality conditions that occur during the spring snowmelt runoff period require the operators to make rapid decisions about alum dose changes. During the 2005 snowmelt runoff, the alum dose was adjusted to keep the zeta potential within the ± 3 mV range as the TOC rose to its peak and then descended back down towards its baseline value. A new generation of zeta potential instruments allows for frequent measurements of zeta potential that are reliable and that are not user-dependent. The adjustment of the alum dose based on zeta potential resulted in the alum dose closely following the TOC, with the alum dose being adjusted by about 3.5 mg/L for each mg/L change in raw water TOC. While maintaining the postcoagulation targets for pH and zeta potential, the full-scale process performance was evaluated with respect to the ability to meet the multiple goals of a combined filter effluent turbidity of less than 0.1 ntu, a TOC removal greater than 50%, and a residual aluminum less than 100 ug/L. The results of this full-scale case study showed that zeta potential measurements can be successfully used by plant operators as a key process control and optimization tool during challenging conditions of high TOC water, allowing them to meet their multiple plant effluent goals. © 2006 American Water Works Association WQTC Conference All Rights Reserved.
At present little is known about the relationship between raw water characteristics, such as natural organic matter (NOM) content, and the universal applicability of coagulation optimisation through surface charge measurement. This research aims to investigate this issue by comparing case study sites in the US (Poudre River, Fort Collins, Colorado) and the UK (Albert Reservoir, Halifax) across periods of elevated organic levels. During the period of April to June 2004 in raw Poudre River water dissolved organic carbon (DOC) levels increased rapidly from 3.5 to 7.4 mg L-1 as a direct result of the spring snowmelt runoff, whereas at Albert reservoir, which is a moorland peat catchment, DOC concentrations varied between 7.8 and 10.1 mg L-1 during the period of January to March 2004. NOM is a highly heterogeneous mixture of organic compounds that vary with regards to acidity, molecular weight, hydrophobicity and charge density. XAD resin adsorption techniques were employed to fractionate the water into its hydrophobic and hydrophilic components. Results revealed that NOM composition and characteristics can vary both temporally and spatially, with increased DOC concentrations associated with both an increase in hydrophobic content and charge density. Optimising coagulation based on a zeta potential range (-10 to +5 mV) produced stable average DOC residuals for both locations, although the exact value is also dependent on the hydrophilic composition of the water and the coagulant used, with alum removing approximately 0.5 mg L-1 less DOC compared with ferric.
Conventional coagulation is still the main treatment process for algae removal in water treatment. The coagulation efficiency can be significantly improved by the preoxidation of algae-containing water. Jar test was conducted to determine the optimal condition for the removal of diatoms, especially Cyclotella sp. by preoxidation and the subsequent coagulation. The effects of various concentration of PAC (Polyaluminum chloride) on coagulation with and without preoxidation using chlorine or potassium permanganate at different pHs (7.7 and 9.0) were evaluated. At pH 7.7, preoxidation with 2ppm followed by coagulation with 7.5 ppm PAC coagulant could reduce Cyclotella sp. concentration by 86%. At pH 9.0, preoxidation with 1 mg followed by coagulation with 12.5 ppm PAC coagulant reduced Cyclotella sp. concentration by 85%. Non-linear regression was applied to determine the optimal condition. At pH 7.7 and 9.0, R was over 0.9, respectively. The pH of algal blooming water is over 9.0. Algae (diatom; Cyelotella sp.) can be controlled in the following ways: preoxidation with 1 mg followed by coagulation with 12.5 ppm PAC coagulant can remove 80% algae from water. If water pH is adjusted to 7.7, it was expected that less amount of coagulant (7.5 or 10 mg PAC /L) after preoxidation ( 2 ppm or 0.33, 1 ppm) would be needed to achieve similar level of algae removal. The oxidation with 0.33ppm followed by coagulation with 7.5 ppm PAC coagulant was preferable due to cost-effectiveness of treatment condition and color problem after treatment.
This article synthesizes work done over the past few decades to better understand the removal of organic contaminants by the coagulation process, alone and in combination with other processes. Published data demonstrate that coagulation can substantially reduce the concentration of certain organic contaminants found in drinking water supplies, and that an understanding of the fundamental mechanisms by which coagulation removes organic contaminants facilitates qualitative prediction of the types of contaminants likely to be removed and the effects of process control variables. Data also demonstrate that removal of organic contaminants by coagulation can be influenced by other processes, such as preozonation, and that coagulation can influence the removal of organic contaminants by subsequent treatment processes, such as filtration and activated carbon adsorption. Este trabajo sintetiza la contidad vasta de trabajos hecho sobre la última década para entender mejor el proceso de coagulación, mostrando áreas de donde investigadores estan de acuerdo tanto corno especulando sobre áreas de desacuerdo. El autor concluye que coagulación puede disminuir sustancialmente la concentratión de ciertos contaminantes orgânicos encontrados en provisiones de agua potable; un entendimiento de los mecanismos fundamentales por cual coagulación remove contaminantes orgánicos facilita predicción cualitativo de los tipos de contaminantes que más probable pueden ser removidos y la influencia de los variables del proceso; remoción de contaminantes orgánicos por coagulación puede ser influida por otros procesos, tal corno preozonización; y coagulación puede influir la remoción de contaminantes orgánicos por procesos de tratamiento subsiguientes, tales como f iltración y adsorción de carbón activado.
IntroductionFresh Water Primary TreatmentAerationCoagulation, Flocculation and ClarificationFiltrationDisinfection ChlorinationOzoneBoiler WatersRefrigerant WatersWaste Water Types of Waste from Food Processing OperationsPhysical TreatmentChemical TreatmentBiological Treatments Aerobic Treatment – Attached FilmsAerobic Treatment Suspended BiomassAerobic Treatment Low TechnologyAnaerobic TreatmentsBiogas UtilisationSludge DisposalFinal Disposal of Waste Water Primary TreatmentAerationCoagulation, Flocculation and ClarificationFiltrationDisinfection ChlorinationOzoneBoiler WatersRefrigerant Waters ChlorinationOzone Types of Waste from Food Processing OperationsPhysical TreatmentChemical TreatmentBiological Treatments Aerobic Treatment – Attached FilmsAerobic Treatment Suspended BiomassAerobic Treatment Low TechnologyAnaerobic TreatmentsBiogas Utilisation Aerobic Treatment – Attached FilmsAerobic Treatment Suspended BiomassAerobic Treatment Low TechnologyAnaerobic TreatmentsBiogas Utilisation
Optimization of coagulant dosage in water treatment is becoming more critical as a result of increased attention to the removal of micropollutants, trihalomethane (THM) precursors, and pathogens resistant to disinfection. At the same time, the availability of a large number of coagulants, flocculents, and other additives, and the recent introduction of technologies for the continuous characterization of coagulated flows, has increased the ability to optimize coagulation while increasing the complexity of this optimization process. One method identified by the U. S. Environmental Protection Agency (EPA) for reduction in THM precursors is improved clarification. Implicit in such improvement is better control of the coagulation process. Improved removal of total organic carbon (TOC) by coagulation reduces the oxidant demand, which facilitates the use of alternative disinfectants. Alum coagulation has also been reported to selectively remove organics responsible for chloroform production. Inorganic pollutants of increasing concern include heavy metals such as lead, mercury, cadmium, and chromium. Even when removal of these contaminants is substantially less than 100 %, maximizing removal assists in obtaining an increased overall removal through all processes employed at a plant. (Korn-PTT) 35 007532037