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MgO is added during warm lime softening (WLS) to remove silica from steam-assisted gravity drainage produced water. Although it is a general practice in the oil sand industry to avoid MgO slaking t...

Since the 1970s, The University of Texas at El Paso and El Paso Water have had a synergistic university-utility partnership, and in 2002, we began a sequence of investigations of enhanced recovery of water from silica-saturated reverse osmosis concentrate: (a) two-pass nanofiltration (NF) and reverse osmosis (RO) treatment, (b) lime softening for silica removal, (c) vibratory shear enhanced processing (VSEP), (d) continuous-flow seawater RO treatment of brackish RO concentrate, and finally (e) high-recovery concentrate enhanced-recovery reverse osmosis (CERRO) process. Studies funded by El Paso Water, Texas Water Development Board, U.S. Bureau of Reclamation, and WateReuse Research Foundation were conducted at the Kay Bailey Hutchison (KBH) Plant in El Paso and the Brackish Groundwater National Desalination Research Facility in Alamogordo, NM, and showed that as much as 88% of the water could be recovered from silica-saturated KBH concentrate using the CERRO process. Full-scale implementation of the CERRO process at well sites in El Paso has resulted in 70%-75% recovery of RO concentrate with a specific energy consumption of 1.23 kWh/m3 (4.6 kWh/kgal) and total estimated cost of approximately $0.59/m3 ($2.25/kgal). Cost-effective high-recovery desalination technologies such as CERRO are essential for drought-proof water supply in arid cities such as El Paso. PRACTITIONER POINTS: This two-decade UTEP-EPW research partnership was sustained by a long-term commitment to research and consistent financial support from EPW. Universities can collaborate to leverage utility funding toward larger external grant funding to advance research and development in a win-win partnership. The high-recovery CERRO process was developed through multiple phases of concentrate management research, which would not have been possible without long-term research commitment and risk tolerance from EPW. CERRO systems are being implemented at full scale in El Paso to recover water from silica-saturated RO concentrate at an estimated specific energy consumption of 1.23 kWh/m3 (4.6 kWh/kgal) and total amortized cost of $0.59/m3 ($2.25/kgal).

The objective of this study was to investigate the swelling potential of compacted lime-softening sludge for application in landfill liners. The study involved the assessment of the effect of compaction and moulding moisture content (30–40%), corresponding to the Proctor standard compaction test. One-dimensional oedometer swell tests were conducted using distilled water, tap water, and municipal landfill leachate, resulting in the determination of the expansion indices. Moreover, changes in the moisture content and dry density during the swelling process were investigated. The expansion index was significantly influenced by the initial moisture content and liquid chemistry. Subsequently, these factors also affected the sludge dry density decrease, and its moisture content increase, whereas the impact of the initial dry density on expansion was of low importance. An increase in the sludge moulding moisture content, limited swelling in all liquids used. The highest expansion, dry density, and moisture content changes due to swelling were identified for leachate at w wopt. It should be underlined that the effect of liquid on the swelling potential faded away along with a further increase in the moisture content w > wopt. The novelty of the work lies in identifying a significant plunge of the expansion index at w ≈ wopt for the leachate swelling test. The lime-softening sludge non-swelling moisture content was defined as wnon ≈ (wopt + 4.0%) − (wopt + 4.5%). For practical engineering implications, the moisture content between (wopt + 2.0%) and (wopt + 4.0%) was provided for the most suitable sludge application in landfill liners.

SYNOPSIS To conserve fresh water resources and comply with environmental regulations, DRDGOLD, a South African gold producer re-treating surface tailings, has transitioned to a fully closed water circulation system. Consequently, the accumulation of contaminants, as well as addition of reagents, has led to changes in water composition that have compromised leach performance and overall gold recovery. A two-sample t-test confirmed a significant difference in gold recoveries between the use of Rand Water, which was used as a benchmark, and untreated process water. Atomic absorption analysis of ERGO's process water, confirmed the presence of iron, nickel, zinc, and manganese. A study of the effect of the identified contaminants on gold recovery showed that iron, nickel, and zinc have the largest negative effect on gold recovery, with iron and nickel being more detrimental than zinc. Sulphates were shown to have a possible passivation effect, which also influenced gold recoveries, although to a lesser extent than the heavy metals. Calcium, when present in excess, had a positive influence on gold recovery indicating the possible formation of a calcium aurocyanide complex. Lime softening successfully reduced the heavy metal and sulphate concentrations, and the gold recoveries obtained with the treated process water were similar to those as achieved with Rand Water. Keywords: gold tailings, re-processing, water quality, gold recovery.

This analysis explores the implications of technology options for steam-assisted gravity drainage (SAGD) surface facilities on cost, energy, greenhouse gas (GHG) emissions, and water consumption. Water integration in the form of distributed effluent treatment system design as well as heat integration considerations are the basis of this study. Cost savings are accomplished by sequentially employing water network optimization and energy integration techniques. Total annual cost savings of 2.7 to 7.8% are achieved at the surface facility through water integration. Additional operating cost savings of 9.2–10.2% are found due to heat integration. Of the technology options considered in this study, hot lime softening (HLS) with blowdown evaporation and hot lime softening with blowdown recycle are the most promising when considering the tradeoffs between energy, greenhouse gas emissions, and water consumption. However, these options are quite different (i.e., blowdown evaporation has lower water consumption but higher greenhouse gas emissions than blowdown recycle, whereas blowdown recycle has lower greenhouse gas emissions but higher water consumption than blowdown evaporation). Deciding between these options requires placing a value on these environmental externalities. The approach described in this work can be applied to inform decisions in the face of tradeoffs between a range of performance metrics. In addition, the analysis framework described in this paper can be adapted to consider new technology pathways as they become available.

The research goal was to investigate the hydraulic conductivity of compacted lime-softening sludge as a material to be applied to landfill liners. In doing so, the effect of compaction and moulding moisture content on the sludge hydraulic conductivity was assessed. An approximate polynomial k10meanat hydraulic gradients ≥30 for degree of compaction (0.95–1.05) and moulding moisture content (28%–36%) was determined. The results of short-term tap water permeation tests revealed that all hydraulic conductivity values were less than 2.5•10–8 m/s. A lowest hydraulic conductivity of 6.5•10–9 m/s, as well as a corresponding moisture content of 31% were then established. The long-term hydraulic conductivity was measured with tap water, distilled water, NaOH and HCl solutions and municipal waste leachate. The factors of permeating liquids and permeation time significantly affected the initial hydraulic conductivity. The long-term hydraulic conductivity increased for NaOH and HCl solutions and decreased for tap and distilled water. A significant reduction of hydraulic conductivity was observed for leachate permeation. The investigated material met the requirements for the liner systems of inert landfill sites regardless of pH and the limit value for hazardous and non-hazardous waste landfills.

Warm lime softening is commonly used to reduce hardness, silica, and a small fraction of organic matter from steam-assisted gravity drainage (SAGD) produced water through the addition of lime, soda ash, MgO, coagulant and flocculant. We report a systematic study on the impact of solution chemistry on the epichlorohydrin-dimethylamine coagulant demand for the treatment of synthetic SAGD produced water. Concentrations of magnesium, calcium, sodium bicarbonate, clay (mimicking suspended solids), sodium metasilicate (representing silica), and humic acid (mimicking dissolved organic matter) were varied to study their impact on coagulant demand. The impact of the concentration of lime, soda ash, and MgO on coagulant demand was also studied. Within the studied concentration range, the coagulant dose increased linearly with increasing concentration of humic acid (Ycoagulant = 29 + 0.703XHA) and silica (Ycoagulant = 52 + 0.537Xsilica), and increased slightly with increasing concentration of lime and soda ash, but remained almost unchanged with increasing concentration of dissolved hardness, clay, or MgO. The observations were correlated to the understanding of the electrokinetic properties of CaCO3 and Mg(OH)2 particles in lime softening. The findings provide insights for evaluating onsite coagulant dose and optimizing the process.

Significant effort has been made to measure and understand the surface charge of CaCO3 and Mg(OH)2 particles. Many laboratory experiments have been reported on zeta potential of natural and prepared CaCO3 and a few have also been published for Mg(OH)2, however, there are very few reported measurements of zeta potential of CaCO3 and Mg(OH)2 particles at conditions relevant to lime softening, despite lime softening being a common and established process for water treatment. The present study aims to understand the interactions and electrokinetic properties of these two particles in lime softening. Effects of various experimental parameters such as pH, temperature, aging, inorganic carbon (CO32−/HCO3−), and divalent cations (Ca2+/Mg2+) on the electrokinetic properties (i.e. zeta potential) of CaCO3 and Mg(OH)2 particles were individually studied. The interactions between humic acid (mimicking natural organic matter), silicate (representing silica), clay (mimicking suspended solids) and CaCO3/Mg(OH)2 particles were studied, as well as the interactions between CaCO3 and Mg(OH)2. Thermodynamic modeling was used to predict precipitates as a function of solution chemistry and assist with data interpretation. The results provide considerable insight into factors that are of importance to lime softening.

This study used computer simulation to select appropriate process designs to make coal seam gas (CSG) associated water comply with beneficial reuse regulations. The hypothesis was that computational simulation may predict the unit operations required for treatment of CSG associated water over a wide range of salinities. AqMB software facilitated complete analysis of water treatment from initial storage pond to final pH and sodium adsorption ratio (SAR) adjustment. Three samples of CSG associated water ranging from 3650 to 22123 mg/L total dissolved solids content were evaluated. Common to each process design was a settling pond, coarse & fine filtration, softening, anti-scalant addition, and reverse osmosis. When the water hardness was very hard, then a lime softening system may be required. Both microfiltration and ultrafiltration were considered, and in both cases the level of suspended solids was reduced to close to zero. Sodium exchanged WAC resin removed the majority of alkaline earth ions and inhibited downstream scale formation. The presence of substantial alkalinity was addressed by use of acid exchanged WAC resin in combination with an air stripper. However, process economics indicated this option was not favourable. A two-stage Reverse Osmosis system not only recovered from ca. 74–79 % water with all CSG associated water types but also the water quality was compliant with beneficial reuse regulations. The computer predictions mirrored actual data from operating industry sites.

MEng. (Chemical Engineering), North-West University, Potchefstroom Campus Water is a scarce commodity in South Africa and one of the largest consumers of water is the industrial sector. Within the industrial sector, power generation uses a vast amount of water. This water is necessary for cooling equipment, as well as for steam generation for turbines. In this study chemical treatment processes adequate for the treatment of raw water as well as RO-reject water from the Grootvlei power station were developed through identification of suitable coagulants and flocculants as well as optimum operating conditions. Such initiative was carried out to assist Eskom in achieving its goal of zero liquid effluent discharge policy; thereby, to minimise its environmental footprint and reduce the amount of water abstracted from rivers. Two mechanisms of water treatment were considered, based on the nature of pollutants in the water, namely, the flocculation mechanism, which involves charge neutralisation and agglomeration of flocs, and the crystallisation mechanism, whereby super saturation occurs to promote crystal growth. The flocculation mechanism was applied to the treatment of raw water. Coagulants and flocculants were used to remove dissolved solids from the water; therefore, reducing turbidity of the water. Coagulants were used to neutralise the charge of the particles in the water, and flocculants were used to aid in the agglomeration of the particles. The optimal conditions were achieved using polyaluminium chloride (PAC) as a coagulant, at a dosage of 30 mg/L, and ARFLOC100 as a flocculant, at a dosage of 0.8 mg/L. This combination yielded turbidity as low as 2 NTU. Settling was relatively slow and a duration of 30 minutes was needed to achieve a 10 mL floc bed. With the treatment of RO-reject water, the crystallization mechanism was considered whereby lime and NaOH were used to reach super-saturation. With the super saturation, scaling agents, which are the main problem with the RO-reject water, would be insoluble, and crystals will form and precipitate. The optimal conditions when using lime were Rheofloc5023, 0.5 mg/L, ARFloc100, 0.2 mg/L and lime, 220 mg/L, at 60°C. This combination yielded a conductivity removal of 36%, a turbidity increase of 59%, a total hardness removal of 54% and an alkalinity removal of 71%. When NaOH was used, the treatment was more efficient at 40°C. Rheofloc5414 was found to be the best flocculant to use with a dosage of 220 mg/L NaOH. This yielded a conductivity removal of 1.26%, a turbidity removal of 58.75%, a total hardness removal of 20.3% and an alkalinity removal of 50.6%. The settling velocity and stability of the crystals were, however, superior at higher temperatures with lime and NaOH, the Rheofloc5414 with the NaOH being more stable and quicker to settle and precipitate. The difference between these two mechanisms could be seen clearly in this study, as flocculation occurred more rapidly, and less slow mixing time was necessary to treat the raw water. It was clear that super-saturation was necessary for the crystallisation process to take place during the treatment of RO-reject water. The latter mostly contains ion pollutants, while raw water contains mostly organic pollutants. It can also be concluded that temperature is important in the crystallisation process initiated by lime, as the treatment was more efficient at higher temperatures. Lastly, it was seen that crystals are more stable and settle faster than the flocs that formed in the treatment of the raw water. Masters

South Africa is an arid country with an annual average rainfall less than half of the world’s average rainfall. The industrial sector uses 11% of this limited amount of water. Eskom is one of these users. Within the water treatment system at the Grootvlei power station, reverse osmosis (RO) is used. The retentate from the membranes is pumped into a sump. This water can be treated for further usage, which ensures that the plant abstracts less water from the environment. Rheofloc, an inorganic polymeric flocculant was used in this study in conjunction with lime treatment, to reduce the conductivity of the water. As the conductivity decreases, the number of ions in the water decreased. The jar test method consisted of the addition of the coagulant and flocculant during rapid mixing for 5 minutes at 240 rpm, thereafter the lime was added to increase the pH to 10.1 during slow mixing which occurred for 90 minutes at 80 rpm. This was done at 40°C and at 60°C to observe the effect that temperature has on the reduction of the conductivity in the water. Results showed that the reduction of conductivity levels was higher at 60°C. This is due to the increase of the rate of reaction with an increase in temperature. Thus the treatment of RO- reject is preferred at 60°C to achieve effective removal of ions with the potential of scale formation

Za pridobivanje pitne vode iz studenčnice se lahko uporablja proces reverzne osmoze. Podzemne vode, kamor po večini uvrščamo studenčne vode, so bogate z raztopljenimi minerali ter posledično vsebujejo veliko kalcijevih in magnezijevih hidrogenkarbonatov, ki povzročajo trdoto vode. V procesih s povišanim tlakom ali temperaturo kot je reverzna osmoza, se skupaj s suspendiranimi delci kot je SiO2 obarjajo ter mašijo membrane. Rešitev tega problema so različni postopki predobdelave, ki problematične snovi odstranijo oziroma dovolj zmanjšajo. V diplomski nalogi smo iskali primerno metodo, da bi čim bolj zmanjšali vsebnost kalcijevih in magnezijevih hidrogenkarbonatov ter silicijevega dioksida, ki je prav tako prisoten v uporabljeni studenčni vodi. Preizkusili smo različne postopke obdelave te vode, pri katerih smo za večjo učinkovitost med samimi postopki višali temperaturo in pH vrednost. Uporabljene metode so bile mehčanje z apnom, koagulacija ter njuna kombinacija. Pri koagulaciji smo uporabili dva koagulanta, in sicer PACl ter Al2(SO4)3. Vzorčeni vodi smo pred in po obdelavi določali: SiO2, celokupno, karbonatno, kalcijevo, magnezijevo in nekarbonatno trdoto motnost, pH, elektroprevodnost, temperaturo, skupne raztopljene snovi (TDS), železo, zeta potencial ter velikost delcev. Rezultati so pokazali, da je najučinkovitejša metoda bilo mehčanje z apnom pri temperaturi med 58 °C in 60 °C in pH 10, ki smo ga dosegli z dodatkom NaOH. Precej učinkovita je bila tudi koagulacija s PACl in apnom pri enakem temperaturnem območju. Pri tem se je sicer odstranilo veliko SiO2 vendar precej manj trdote. One of the ways of purifing well water to meet drinking water criteria is by using reverse osmosis. Well water which is usually classified as ground water is enriched with dissolved minerals and consenquently contains a great amount of calcium and magnesium bicarbonates. These ions cause hardness of the water and along with suspended particles such as SiO2 they precipitate causing membrane fouling in processes with increased pressure or temperaure such as reverse osmosis. A solution to this are different pretreatment processes that reduce or even remove problematic substances. In this thesis we were searching for a suitable method for reducing calcium and magnesium bicarbonates of the water and silica it contains to the maximum extent. We tested different pretreatment processes where we increased temperature and pH value to achieve greater efficiency. The used methods were lime softening, coagulation and the combination of both. For coagulation we used coagulants PACl and Al2(SO4)3. Before and after treatment, we measured: SiO2, total hardness, carbonate hardness, calcium hardness, magnesium hardness, non carbonate hardness, turbidity, pH value, conductivity, temperature, total dissolved solids (TDS), iron, zeta potential and particle size of the sampled water. The results showed that the most efficient was the lime softening pretreatment method with temperature between 58 °C and 60 °C and pH value of 10, which we achieved with the addition of NaOH. Also quite effective was coagulation with PACl and lime in the same temperature interval, which removed a great deal of SiO2 but a lot less hardness.

The given research is devoted to the development of the technology of utilization of lime-softening sludge to obtain calcium nitrate.Water treatment waste by chemical composition differs from natural raw materials such as limestone, which is traditionally used to obtain calcium nitrate. Sludge obtained at the stage of lime-softening contains about 70% calcium carbonate, a fairly large amount of iron, which enters the precipitate with solutions of coagulants, as well as organic impurities. Organic impurities come from river water and precipitate as a result of coagulation.The process of extracting calcium by the acid solution is stable. The results are well reproduced on two kinds of waste from different enterprises. This is explained both by the high dissolution rate of calcium carbonate in nitric acid, and the similar chemical composition of the waste.Not only calcium compounds, but also iron ones together with the organic component of liming sludge fall into the solution. A process scheme is proposed for cleaning the solution, which should include the stages of oxidation of the solution and subsequent precipitation of iron.The concentration of iron in the experimental solutions was up to 6 g/l. With the help of the calculations of the precipitate-solution equilibrium, it has been stated that iron in the area of low concentrations of nitric acid precipitates in the solution, and calcium stays in it. The decrease of the acid concentration was carried out by the addition of pure calcium carbonate.Kinetic studies of the process of iron precipitation on model solutions of iron (III) nitrate have been carried out. The second-order kinetic equation is obtained. The calculation of the process activation energy is available in the paper. The value of the energy is ~37 kJ/ mole, which is the evidence of the precipitation process in the transition area. The undissolved residue contains about 40% iron and can be used to obtain coagulants.Thus, the application of the proposed method will allow the best use of water treatment waste, Исследование посвящено разработке технологии утилизации известкового шлама водоподготовки с получением кальциевой селитры.Установлено, что отходы водоподготовки по химическому составу отличаются от природного сырья – известняка, который традиционно используют для получения кальций нитрата. Шлам, получаемый в процессе известкования воды, содержит около 70 % кальций карбоната, достаточно большое количество железа, попадает в осадок с растворами коагулянтов, а также, органические примеси. Органические примеси поступают с речной водой и осаждаются в результате коагуляции.Процесс извлечения кальция раствором кислоты является устойчивым. Результаты хорошо воспроизводились на двух видах отходов различных предприятий. Это объясняется как высокой скоростью растворения кальций карбоната в азотной кислоте, так и схожим химическим составом отходов.В раствор попадают не только соединения кальция но и железа и органическая составляющая шламов известкования. Для очистки раствора предложена схема процесса, в которую должны входить стадии окисления раствора и последующего осаждения железа.Концентрация железа в экспериментальных растворах составляла до 6 г/л. С помощью расчетов равновесия осадок – раствор установлено, что в области низких концентраций азотной кислоты железо будет выпадать в раствор, а кальций в нем оставаться. Уменьшение концентрации кислоты проводили добавлением чистого кальций карбоната.Проведено кинетические исследования процесса осаждения железа на модельных растворах железо (III) нитрата. Получено кинетическое уравнение второго порядка. Рассчитана энергия активации процесса, значение которой ~ 37 кДж/моль свидетельствует о протекании процесса осаждения в переходной области. Нерастворившийся остаток содержит около 40 % железа и может использоваться для получения коагулянтов.Применение предложенного метода позволит наиболее полно использовать отходы водоподготовки, Дослідження присвячено розробці технології утилізації вапняного шламу водопідготовки з одержанням кальцієвої селітри.Встановлено, що відходи водопідготовки за хімічним складом відрізняються від природної сировини – вапняку, який традиційно використовують для одержання кальцій нітрату. Шлам, що утворюється на стадії вапнування води містить близько 70 % кальцій карбонату,досить велику кількість заліза, що потрапляє до осаду з розчинами коагулянтів, та органічні домішки. Органічні домішки надходять з річковою водою і осаджуються в результаті коагуляції.Процес вилучення кальцію розчином кислоти – сталий. Результати добре відтворювались на двох видах відходів різних підприємств. Це пояснюється як високою швидкістю розчинення кальцій карбонату в нітратній кислоті, так і схожим хімічним складом відходів.До розчину потрапляють не тільки сполуки кальцію але й заліза та органічна складова шламів вапнування. Для очищення розчину запропоновано схему процесу, до якої повинні входити стадії окиснення розчину та наступного осадження заліза.Концентрація заліза в експериментальних розчинах складала до 6 г/л. За допомогою розрахунків рівноваги осад – розчин з’ясовано, що в області низьких концентрацій нітратної кислоти залізо буде випадати в розчин, а кальцій в ньому лишатися. Зменшення концентрації проводили додаванням чистого кальцій карбонату.Проведено кінетичні дослідження процесу осадження заліза на модельних розчинах залізо (ІІІ) нітрату. Одержано кінетичне рівняння другого порядку. Розраховано енергію активації процесу, значення якої ~ 37 кДж/моль свідчить про перебіг процесу осадження в перехідній області. Залишок містить близько 40 % заліза і може застосовуватися для одержання коагулянтів.Застосування запропонованого методу дозволить найбільш повно використовувати відходи водопідготовки

One of the most direct means for human exposure to nanoparticles (NPs) released into the environment is drinking water. Therefore, it is critical to understand the occurrence and fate of NPs in drinking water systems. The objectives of this study were to develop rapid and reliable analytical methods and apply them to investigate the fate and transportation of NPs during drinking water treatments. Rapid single particle ICP-MS (SP-ICP-MS) methods were developed to characterize and quantify titanium-containing, titanium dioxide, silver, and gold NP concentration, size, size distribution, and dissolved metal element concentration in surface water and treated drinking water. The effectiveness of conventional drinking water treatments (including lime softening, alum coagulation, filtration, and disinfection) to remove NPs from surface water was evaluated using six-gang stirrer jar test simulations. The selected NPs were nearly completely (97 ± 3%) removed after lime softening and alum coagulation/activated carbon adsorption treatments. Additionally, source and drinking waters from three large drinking water treatment facilities utilizing similar treatments with the simulation test were collected and analyzed by the SP-ICP-MS methods. Ti-containing particles and dissolved Ti were present in the river water samples, but Ag and Au were not present. Treatments used at each drinking water treatment facility effectively removed over 93% of the Ti-containing particles and dissolved Ti from the source water.

Phosphorus (P), calcium (Ca) and natural organic matter (NOM) naturally occur in all aquatic ecosystems. However, excessive P loads can cause eutrophic or hyper-eutrophic conditions in these waters. As a result, P regulation is important for these impaired aquatic systems, and Ca-P co-precipitation is a vital mechanism of natural P removal in many alkaline systems, such as the Florida Everglades. The interaction of P, Ca, and NOM is also an important factor in lime softening and corrosion control, both critical processes of drinking water treatment. Determining the role of NOM in Ca-P co-precipitation is important for identifying mechanisms that may limit P removal in both natural and engineered systems. The main goal of this research is to assess the role of NOM in inhibiting Ca and P co-precipitation by: (1) measuring how Ca, NOM, and P concentrations affect NOM's potential inhibition of co-precipitation; (2) determining the effect of pH; and (3) evaluating the precipitated solids. Results showed that Ca-P co-precipitation occurs at pH 9.5 in the presence of high natural organic matter (NOM) (≈30 mg L(-1)). The supersaturation of calcite overcomes the inhibitory effect of NOM seen at lower pH values. Higher initial P concentrations lead to both higher P precipitation rates and densities of P on the calcite surface. The maximum surface density of co-precipitated P on the precipitated calcite surface increases with increasing NOM levels, suggesting that NOM does prevent the co-precipitation of Ca and P.

This article provides a state-of-the-art review on the uses of magnetic ion exchange (MIEX) resin in drinking water and wastewater treatment, with emphasis on removal of dissolved organic matter (DOM) from drinking water and wastewater, regeneration efficiency, removal of inorganic and synthetic organic chemicals, comparison with other anion exchange resins, and integration with other physical-chemical processes. Through laboratory jar tests, pilot plant tests, and full-scale installations for a variety of drinking water sources, MIEX resin can achieve 30–80 % removal of dissolved organic carbon (DOC), which is often higher than alum or ferric coagulation. In addition, MIEX resin has been shown to remove hydrophilic, transphilic, and hydrophobic fractions of DOM and a wide range of molecular weight fractions of DOM. As a result, MIEX pretreatment results in substantial reductions in the formation of trihalomethanes and haloacetic acids upon chlorination. MIEX resin can achieve bromide removal in the range of 10–50 %, with higher bromide removal in waters with low DOC, low alkalinity, and low sulfate. However, there are commercially available anion exchange resins that are more selective for bromide than MIEX resin. MIEX resin has been investigated in combination with coagulation, activated carbon adsorption, membrane separation, lime softening, and ozonation. MIEX pretreatment has been shown to reduce downstream chemical requirements and improve the operation of downstream processes. This is most evident for coagulation and ozonation where the coagulant dose can be reduced by 50–75 % and the ozone concentration can be increased by 40–65 %. In general, MIEX pretreatment shows minor reductions in membrane fouling. Future research should continue to investigate the integration of MIEX treatment with other processes.

Concentrations of viable microbial cells were monitored using culture-based and culture-independent methods across multichamber ozone contactors in a full-scale drinking water treatment plant. Membrane-intact and culturable cell concentrations in ozone contactor effluents ranged from 1200 to 3750 cells/mL and from 200 to 3850 colony forming units/mL, respectively. Viable cell concentrations decreased significantly in the first ozone contact chamber, but rose, even as ozone exposure increased, in subsequent chambers. Our results implicate microbial detachment from biofilms on contactor surfaces, and from biomass present within lime softening sediments in a hydraulic dead zone, as a possible reason for increasing cell concentrations in water samples from sequential ozone chambers. Biofilm community structures on baffle walls upstream and downstream from the dead zone were significantly different from each other ( p = 0.017). The biofilms downstream of the dead zone contained a significantly ( p = 0.036) higher relative abundance of bacteria of the genera Mycobacterium and Legionella than the upstream biofilms. These results have important implications as the effluent from ozone contactors is often treated further in biologically active filters and bacteria in ozonated water continuously seed filter microbial communities.

The City of Fargo completed a Facility Plan of their Water Treatment Plant (WTP) in 2011 to address two main issues: increasing water demands and high sulfate concentrations within a raw water source (Sheyenne River) primarily due to Devils Lake flooding. Reverse Osmosis (RO) was recognized as the most appropriate technology for sulfate reduction, and recommended for use in the WTP expansion. An RO pilot study was performed to evaluate its feasibility for two operational scenarios. RO membranes experienced rapid fouling in the Polishing Scenario, which used RO to further treat filtered water from the existing WTP (pretreatment, lime softening, ozone, and granular filtration). RO membranes exhibited superior performance in the Parallel Scenario, which was a separate treatment process (coagulation/flocculation/sedimentation + microfiltration/ultrafiltration +RO) parallel to the existing WTP. RO membrane autopsies indicated that membrane fouling was organic and biological for the Polishing Scenario while organic and scaling for the Parallel Scenario. Optimization studies were performed in the Parallel Scenario to determine optimal coagulation conditions for pretreatment as well as flux, recovery, and membrane cleaning regimes for both the MF/UF and the RO. Uniquely, an RO membrane selection pilot was conducted for both scenarios to evaluate RO membranes from four different manufacturers. The slight difference surface chemistry among various RO membrane can cause substantial different performance. It was found that one RO membrane could not be cleaned adequately, although it has many successful applications elsewhere. This one year pilot study proved that RO technology is feasible to reduce sulfate concentrations to acceptable levels in the City’s finished water.

The sludge generated in the lime softening of recirculating cooling water has a large bulk volume and is difficult to dehydrate. The current study tested the effect of fly ash addition on the pollutant removal efficiency and the sludge properties improvement in the softening process. The hardness and alkalinity removal efficiency before and after the addition of fly ash were evaluated. The effects of fly ash addition on chemical sludge properties, such as the sludge water content, particle size, and microstructure, were also investigated. With a fly ash dosage of 270 mg/L, the removal rates of calcium hardness, total hardness, and total dissolved solids increased by 20.7, 11.5, and 6.1% compared with those obtained in the absence of fly ash. The addition of fly ash can improve the stability of treated water by reducing the scaling potential. Fly ash can improve the sludge properties. At a fly ash dosage of 200–250 mg/L, the median diameter of the flocs is four times bigger than the flocs produced ...

Lime softening is a well-established process for partially separating of hardness ions from water. Currently, the lime softening process is adjusted manually based on chemical titration tests aimed at maintaining the simple and total alkalinities in a certain range. Analysis of experimental data from bench and full-scale lime clarifier showed that the current control based on alkalinity is often not correct. It was found in this work that electrical conductivity (EC) can be used as a good indicator for evaluating the performance of lime clarifiers. Therefore, an eco-friendly and very cost effective alternative technique based on EC is introduced in this paper for successful control of lime softening process.

In the present article, the major treatment methods applied for uranium removal from groundwater, with specific applications in drinking water treatment, are reviewed. These include pump-and-treat technologies, such as membrane filtration methods, anion exchange, and the use of adsorbents, such as iron oxides, or titanium dioxide, as well as the application of coagulation processes with the addition of Fe/Al salts, or by lime softening. In all cases, uranium removal is mainly dependent on its speciation, which is greatly affected by the (usually coexisting) carbonate ions in the contaminated water. Under circumneutral pH values, uranium forms anionic complexes with carbonate of the type , or . In situ treatment technologies comprise mainly the use of permeable reactive barriers. These contain reactive materials, such as zero valent iron or hydroxyapatite, and uranium is usually removed by reduction to the respective insoluble products of U(IV); reducing bacteria, when present, can play a suppleme...

The operation and efficiency of a modern, high-tech industrial full-scale water treatment plant was investigated in the present study. The treated water was used for the supply of the boilers, producing steam to feed the steam turbine of the power station. The inlet water was the effluent of municipal wastewater treatment plant of the city of Bari (Italy). The treatment stages comprised (1) coagulation, using ferric chloride, (2) lime softening, (3) powdered activated carbon, all dosed in a sedimentation tank. The treated water was thereafter subjected to dual-media filtration, followed by ultra-filtration (UF). The outlet of UF was subsequently treated by reverse osmosis (RO) and finally by ion exchange (IX). The inlet water had total organic carbon (TOC) concentration 10–12 mg/L, turbidity 10–15 NTU and conductivity 3500–4500 μS/cm. The final demineralized water had TOC less than 0.2 mg/L, turbidity less than 0.1 NTU and conductivity 0.055–0.070 μS/cm. Organic matter fractionation showed that most of the final DOC concentration consisted of low molecular weight neutral compounds, while other compounds such as humic acids or building blocks were completely removed. It is notable that this plant was operating under “Zero Liquid Discharge” conditions, implementing treatment of any generated liquid waste.

The City of Miramar, located in South Florida, has two water treatment plants which utilize two different water treatment processes. The East Water Treatment Plant (EWTP) uses lime softening, while the West Water Treatment Plant (WWTP) uses reverse osmosis treatment. Biscayne aquifer is used as the source water for both plants. Effectiveness of lime softening and reverse osmosis processes were evaluated in terms of trihalomethane (THM) levels in the distribution system with distance and at cul de sacs (dead end streets). The water treated by lime softening had significantly higher levels of THMs in comparison to the water treated by reverse osmosis. With the aging of reverse osmosis membranes (after 5 years), the THM levels exhibited similar levels in both distribution systems. The THM concentrations at the cul de sacs receiving water treated by lime softening were significantly higher in comparison to the system wide water quality. At the cul de sacs receiving water treated by reverse osmosis, T...

An experimental study was carried out to demonstrate and quantify the feasibility of antiscalant (AS) removal from brackish water RO concentrate of high gypsum scaling propensity via lime treatment prior to seeded gypsum precipitation. Based on studies with model solutions, it was shown that sufficient AS removal (up to ∼90%) from RO concentrate is feasible via a lime treatment step (at a dose significantly lower than that required for conventional lime softening) to enable effective subsequent seeded gypsum precipitation. This two-step chemically-enhanced seeded precipitation (CESP) treatment of primary RO concentrate is suitable as an intermediate concentrate demineralization (ICD) stage for high recovery desalting employing secondary RO desalination. Analysis of gypsum precipitation and lime treatment kinetic data suggests that, after adequate CaCO 3 precipitation has been induced for effective AS scavenging, CaSO 4 desupersaturation can be achieved via seeded gypsum precipitation without retardation due to seed poisoning by AS. Also, the lime dose required to prevent seed poisoning during subsequent gypsum desupersaturation via seeded gypsum precipitation can be adequately assessed with a precipitation kinetics model that considers AS seed poisoning based on a Langmuir adsorption isotherm. The degree of AS removal after lime treatment increased linearly with the logarithm of the single lime dose additions. Staged lime dosing (i.e., multiple lime additions), however, removed a higher degree of AS relative to an equivalent single lime dose addition since a higher driving force for CaCO 3 precipitation could be maintained over the course of the lime treatment period.

At one time the raw water naturally available influenced the development of typical regional beer styles. With the development of reliable and efficient water treatment technologies, breweries became independent of the local raw water quality. The proliferation of large breweries is still closely linked to progress in water treatment. The prevailing question is always how to best condition the raw water for the different purposes within the brewery in the most efficient way. The raw water starting points are very different and can range from well water, to surface water, to municipal water, and in some cases to more exotic water sources such as rain or even treated wastewater. The impact of different water ions on the brewing process is discussed, with a special focus on technological requirements, as well as microbiology and corrosion issues. The requirements of divergent water types commonly used for brewing, dilution, service and boiler feed water, and available treatment steps based on examples of large-sized plants are discussed, including traditional methods such as lime softening and ion exchange, as well as more recent treatment systems. Membrane technology is highlighted, as it has had a great impact on treatment technology. Following the success story of reverse osmosis, and more recently developed ultrafiltration, there is now more focus on special applications such as the substitution of lime saturators to produce clear lime water with membranes. This requires higher performance and robustness of the membranes. Finally, some future challenges for water treatment in breweries are outlined. Copyright © 2012 The Institute of Brewing & Distilling

The water source of one ultra-supercritical fossil-fueled power plant is municipal reclaimed water and reservoir water. Techno-economic comparison of several schemes for recirculating cooling water treatment system show that the side stream lime softening treatment system is an optimal scheme. It has comprehensive functions of scale prevention, corrosion prevention and removing suspended solids, and the system combines the make-up water softening treatment system and the side stream suspended solid removal treatment system of recirculating cooling water, which reduce the investment and the operation cost, and meet the requirement of maximum water saving. The side stream lime softening treatment system is energy saving and discharge reduction.

Dissolved organic nitrogen (DON) derived from wastewater effluent can participate in reactions that lead to formation of nitrogenous chlorination by-products, membrane fouling, eutrophication, and nitrification issues, so management of DON is important for both wastewater reuse applications and nutrient-sensitive watersheds that receive discharges from treated wastewater. This study documents DON occurrence in full-scale water/wastewater (W/WW) treatment plant effluents and assesses the removal of wastewater-derived DON by several processes (biodegradation, coagulation, softening, and powdered activated carbon [PAC] adsorption) used for advanced treatment in wastewater reuse applications. After varying levels of wastewater treatment, the dominant aqueous nitrogenous species shifts from ammonia to nitrate after aerobic processes and nitrate to DON in tertiary treatment effluents. The fraction of DON in total dissolved nitrogen (TDN) accounts for at most 52% in tertiary treated effluents (median=13%) and 54% in surface waters impacted by upstream wastewater discharges (median=31%). The 5-day biodegradability/bioavailability of DON (39%) was higher, on average, than that of dissolved organic carbon (DOC, 26%); however, upon chlorination, the DON removal (3%) decreased significantly. Alum coagulation (with ≥8 mg/L alum per mg/L DOC) and lime softening (with pH 11.3-11.5) removed

Arsenic may be found in water that has fl owed through arsenic-rich rocks. Arsenic is a toxic, trace element that is ubiquitous in nature. It can easily be transported from the sediment to the surrounding pore-water. Severe health effects have been observed in populations drinking arsenic-rich water over long periods in countries worldwide. A 2007 study found that over 137 million people in more than 70 countries are probably affected by arsenic poisoning of drinking water. In groundwater, arsenic combines with oxygen to form inorganic pentavalent arsenate and trivalent arsenite. Most arsenic treatments fall into four process categories: ion exchange, membrane process, adsorption, or chemical precipitation. This study investigates the potential of removing arsenic from groundwater by using two process categories ‐ activated alumina and lime softening. Arsenic adsorption by commercially available activated alumina is surveyed and its effi ciency investigated. We have incorporated some of the valuable literature on arsenic remediation by adsorption. According to results of three activated alumina pilot studies, considering infl uence of adsorption time, temperature, pH, alumina quantity, arsenic concentration, and different alumina production resources, it has high effi ciency for arsenic removal. Adsorption isotherm for both species of arsenic (III and V) is compatible with both Freundlich and Langmuir models (correlation coeffi cient >0.93). The prevalent pH range for arsenate was between 6 and 8. Modifi ed activated alumina can remove arsenate at the infl uent pH of 8.1 ± 0.4 to below the maximum concentration level (MCL). The exhausted media passed the Toxicity Characteristic Leaching Procedure (TCLP) test with respect to arsenic. Lime softening operated within the optimum pH range of more than 10.5 is likely to provide a high percentage of arsenic removal (90%) for infl uent concentrations of up to 0.05 mg/L. It may be diffi cult to reduce consistently to 0.01 mg/L by lime softening alone. Systems using lime softening may require secondary treatment to meet that goal.

This paper describes the development and validation of an equilibrium model of an industrial hot-lime-softening boiler-water-treatment unit for a large-scale nickel processing facility in which approximately 6.6 ML per hour of water is processed. In the industrial process, multiple water sources of varying quality are combined before the softening treatment, which makes control and optimization of the softening unit complicated and has brought about the necessity of a robust numerical model of water treatment. In this paper, the numerical thermodynamic and adsorption relations describing the softening treatment process are presented. Lime, magnesia, and soda ash additions are modeled. Emphasis has been placed on calcium, magnesium, and silica treatments as these are of most relevance to the industry. Jar tests described in this paper are used to determine adsorption relations, estimate statistical uncertainties, validate the model performance, and optimize the model parameters. Parameter estimations for equilibrium constants are undertaken and provide insights into the range of model validity and interactions between additions and softened water quality. Further jar testing is utilized to evaluate the effectiveness of using the model to numerically derive optimal chemical additions.

Advances in the application of ion exchange membrane processes for material separation provide new approaches for improving the sustainability of industrial operations. In this work, we report on the application of Donnan dialysis to recover metal cations from lime softening sludge, a byproduct of drinking water production. A cation exchange membrane, which preferentially allows the transport of cations, was used in the Donnan cell. Slurries containing lime softening sludge, gypsum, or calcite were placed on the feed side of the cell and an acidic solution was placed on the sweep side. A concentration gradient between the two sides of the cell extracts metal cations from the feed in exchange for hydrogen ions in the sweep side solution. The influence of acid type, starting pH, and time were evaluated. Although the limited solubility of calcite inhibited its study, significant calcium ion recovery was measured from the feed solutions with gypsum. The results were consistent with theoretical expectations and demonstrated that the pH of the sweep side solution controlled the extent and rate of cation recovery. For the treatment of the lime softening sludge, over 99% of the hydrogen ions were exchanged in the recovery of up to 20% of the calcium and 50% of the magnesium from the lime softening sludge. Over time, depletion of the sweep-side hydrogen ions resulted in the preferential recovery of magnesium from the softening sludge. Our results suggest the process exhibits promise in treating the sludge by recovering metal cations for reuse.

Synthetic musk fragrances are common personal care product additives and wastewater contaminants that are routinely detected in the environment. This study examines the presence eight synthetic musk fragrances (AHTN, HHCB, ATII, ADBI, AHMI, musk xylene, and musk ketone) in source water and the removal of these compounds as they flow through a Midwestern conventional drinking water plant with lime softening. The compounds were measured in water, waste sludge, and air throughout the plant. HHCB and AHTN were detected in 100% of the samples and at the highest concentrations. A mass balance on HHCB and AHTN was performed under warm and cold weather conditions. The total removal efficiency for HHCB and AHTN, which averaged between 67% to 89%, is dominated by adsorption to water softener sludge and its consequent removal by sludge wasting and media filtration. Volatilization, chlorine disinfection, and the disposal of backwash water play a minor role in the removal of both compounds. As a result of inefficient overall removal, HHCB and AHTN are a constant presence at low levels in finished drinking water.