Precipitation softening processes are used to reduce raw water hardness, alkalinity, silica, and other constituents. This helps prepare water for direct use as cooling tower makeup or as a first-stage treatment followed by ion exchange for boiler makeup or process use.
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What is the reduction of hardness of water?
The reduction of hardness, or softening, is a process commonly practiced in water treatment. Chemical precipitation and ion exchange are the two softening processes most commonly used. Softening of hard water is desired (for domestic users) to reduce the amount of soap used, increase the life of water heaters, and reduce encrustation of pipes.
What is chemical precipitation in wastewater treatment?
Chemical precipitation in water and wastewater treatment is the change in form of materials dissolved in water into solid particles. Chemical precipitation is used to remove ionic constituents from water by the addition of counter-ions to reduce their solubility.
What is the chemical name of precipitate in hardness removal?
Chemistry of Hardness Removal Process During precipitation softening, calcium is removed form water in the form of CaCO 3 precipitate and magnesium is removed as Mg(OH) 2 precipitate (Frederick W. Pontius).
What is precipitation softening?
Precipitation softening accomplished at ambient temperatures is referred to as cold lime softening. When hydrated lime, Ca(OH) 2, is added to the water being treated, the following reactions occur: If the proper chemical control is maintained on lime feed, the calcium hardness may be reduced to 35-50 ppm.
What is precipitation softening?
What is the chemical that removes the hardness of water?
What is the temperature of lime softener?
Why is water contaminated in cold process softening?
Does heating reverse the solution reaction?
What is Chapter 07?
Does sludge reduce silica?
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What does selective precipitation mean?
Selective precipitation is a technique of separating ions in an aqueous solution by using a reagent that precipitates one or more of the ions, while leaving other ions in solution.
What is selective precipitation used for?
Selective precipitation of proteins can be used as a bulk method to recover the majority of proteins from a crude lysate, as a selective method to fractionate a subset of proteins from a protein solution, or as a very specific method to recover a single protein of interest from a purification step.
How do you selectively precipitate?
1:354:18Selective Precipitation - YouTubeYouTubeStart of suggested clipEnd of suggested clipIt is the case that a mixture of the halide ions must be slowly added to a solution of silver ions.MoreIt is the case that a mixture of the halide ions must be slowly added to a solution of silver ions. This way the few halide ions that are in solution will precipitate without competition.
What is precipitation in wastewater treatment?
Chemical precipitation in water and wastewater treatment is the change in form of materials dissolved in water into solid particles. Chemical precipitation is used to remove ionic constituents from water by the addition of counter-ions to reduce their solubility.
Which of the following can be used for selective precipitation of proteins?
Ammonium sulfateWhich of the following can be used for selective precipitation of proteins? Explanation: Ammonium sulfate is commonly used for selective precipitation of proteins. It is highly soluble in water and has high ionic strength.
What is the precipitation method?
Chemical precipitation is the process of conversion of a solution into solid by converting the substance into insoluble form or by making the solution a super saturated one. From: Journal of King Saud University - Science, 2019.
What is selective solubility?
[si′lek·tiv ‚säl·yə′bil·əd·ē di‚fyü·zhən] (chemical engineering) The transmission of fluids through a nonporous, polymeric barrier (membrane) by an adsorption-solution-diffusion-desorption sequence.
What is precipitation agent?
Precipitation gravimetry is an analytical technique that uses a precipitation reaction to separate ions from a solution. The chemical that is added to cause the precipitation is called the precipitant or precipitating agent.
Why precipitation occurs in a solution?
The precipitation of a compound may occur when its concentration exceeds its solubility. This can be due to temperature changes, solvent evaporation, or by mixing solvents. Precipitation occurs more rapidly from a strongly supersaturated solution. The formation of a precipitate can be caused by a chemical reaction.
What are precipitation reactions?
A precipitation reaction is one in which dissolved substances react to form one (or more) solid products. Many reactions of this type involve the exchange of ions between ionic compounds in aqueous solution and are sometimes referred to as double displacement, double replacement, or metathesis reactions.
What are the advantages of precipitation?
Precipitation can be used to obtain good results with a number of substances that are difficult to remove with other techniques. Another advantage of this technique is that very specific components can be removed, while not removing other substances; thus there is a high degree of selectivity.
What is precipitation tank?
A Precipitation Tank is a tank which wastewater streams are run into to give an opportunity for any solid matter carried in it to be precipitated. Generally, precipitation is promoted in the tank by adding certain (acid or caustic) is to adjust the PH of the wastewater.
Spreadsheets for Lime Soda Water Softening Calculations
Where to Find Spreadsheets for Lime Soda Water Softening Calculations. For Excel spreadsheets to make lime soda water softening calculations, click here to visit our spreadsheet store. Obtain convenient, easy to use spreadsheets for lime soda water softening calculations at reasonable prices. Read on for information about the use of Excel spreadsheets for this application.
Water Softening | Water Treatment | Water Softener
Water is a universal solvent. Soft rainwater picks up naturally occurring dissolved minerals, including calcium and magnesium carbonates, as it passes over rocks and through soil, which begins to make it hard.
CHEMICAL PRECIPITATION: WATER SOFTENING
iv LIST OF FIGURES AND TABLES Caption Page No. Figure 1: Variation of hardness, alkalinity and pH for varying lime dosages (run1) 6 Figure 2: Variation of hardness, alkalinity and pH for varying lime dosages (run2) 7 Figure3: Comparison of replicate runs 8 Setup and Samples with lime dosages 16
What is the name of the process that precipitates impurities from water?
Chemical precipitation or reagent coagulation, precipitates impurities from purified water via change of pH, electro-oxidising potential or co-precipitation using precipitating agents (coagulants) such as ferrous or aluminium sulphates.
What is chemical precipitation?
Chemical precipitation is a pH adjustment process mainly used for removal of dissolved metals from aqueous wastes. An acid or base is added to a solution to adjust the pH to a point where the constituents to be removed reach their lowest solubility. The solubility of metals decreases as pH increases and the metal ions precipitate out of the solution as hydroxide. Metals can be precipitated by adding alkaline agents, such as lime or caustic soda to raise pH. To remove
How is the rate of metal reduction determined?
The rate of metal chemical reduction from solutions is determined by kinetic factors, by a constant process rate, and the duration of the induction period . The slow reaction in the initial stage depends on the formation of stable particles of solid phase, which show an autocatalytic effect in the following stages. During the initial stage, the reaction proceeds by successive coarsening of nonstable fine particles of the solid product. For example, the crystallization of silver nuclei is performed step by step through the formation of successively coarsening clusters:
What is the most commonly used process for ferrofluids?
Chemical precipitation is the most often employed process although grinding is useful in some circumstances. Chemical decomposition and vapor-liquid reaction are used to produce certain specialized ferrofluids. In all cases, a repulsive layer is provided that envelopes each particle to prevent them sticking to each other.
What is the most effective method for the removal of heavy metals from wastewater?
Chemical precipitation is considered to be the most effective method for the removal of heavy metals from wastewater. It is widely employed in industries since it is relatively inexpensive and easy to operate.
How is a metal colloid precipitated?
A metal colloid is precipitated by a chemical method and a metallized dispersed carrier is produced in a brief contact of the metal colloid with the carrier particles as a result of colloid adsorption. The method is possible if the rate of colloid adsorption is higher than its aggregation rate. •.
Which is denser, sludge or sulfide?
Greater consumption of reagents, as the process proceeds through the formation of hydrocarbonates and an excess of reagent is required to complete the reaction. Sludge is denser and has better dewatering characteristics (apart from Zn and Ni carbonate) Formation of carbon dioxide bubbles. Sulfide.
How to soften water with high TH?
softening through carbonate removal. When the water has a high TH accompanied by a significant M-alk., the water can be softened by using lime to remove the carbonate. This carbonate removal can be carried out: "catalytically" by Gyrazur when no concomitant clarification is needed and when the magnesium content is low; ...
How to re-instate M-alk?
will have to be re-instated by mixing the water with a fraction of water from which the carbonates have not been removed. Both of the following examples illustrate the range of systems that can be used to treat surface water.
Is water a modified anions?
The anions are not modified. Water obtained in this way has a zero TH: it is corrosive and unpleasant to the palate; a certain residual TH needs to be maintained (8 to 15°F) by only softening part of the output which is then mixed into the remaining output.
What happens to precipitation in the absence of crystallisation seeds?
in the absence of crystallisation seeds, precipitation will be very slow, water will remain supersaturated and precipitation of the few suspended substances will tend to take place but mainly over available surfaces, especially if they are metal surfaces (reactor walls, agitators, channels, valves…).
What is the best way to remove permanent hardness?
using sodium carbonate. Removal of permanent hardness is carried out cold with sodium carbonate which may or may not be combined with calcium and magnesium bicarbonate precipitation using lime. This elimination takes place according to the following reactions:
What is settling zone?
a zone where recirculated crystals, water to be treated and lime are thoroughly combined; a settling zone from which the crystals that have been formed are removed and partially returned to the 1 st zone.
Does caustic soda reduce water hardness?
Using caustic soda will, therefore, lower water hardness to a level that is equal to twice the reduction in bicarbonates belonging to the alkaline-earths.
What is the hard water level?
In the United States, hard water is mostly found in the mid western and western states. It ranges between 120-250 mg/L as CaCO3or beyond 250 mg/L as CaCO3 for very hard waters.
How much magnesium noncarbonate hardness is needed for removal?
If the magnesium noncarbonate hardness and lime are expressed as CaCO3 , stoichiometric ratios suggest that for each mg/L of magnesium noncarbonate hardness present, 1 mg/L of lime expressed as CaCO3will be needed for its removal.
What is the most effective method of removing bacteria and viruses from raw water prior to conventional treatment?
zooplankton) and macro-invertebrate filter feeders also reduce pathogen numbers. Apart from pre-chlorination, storage is the most effective method of removing bacteria and viruses from raw water prior to conventional treatment.
How to remove hardness from water?
Softening is another technique commonly used to remove hardness in case water is hard, which is performed by the addition of lime and subsequent precipitation of calcium as calcium carbonate and magnesium as magnesium hydroxide.
What are the most important problems in water?
If the water originates from a surface water supply such as a river, lake, or dam, then the suspended particles are the most important problem. Different techniques to remove suspended particles include the addition of coagulants and the use of membranes.
What is biological waste water treatment?
Biological waste water treatment is the primary method of preparing food-processing waste water flows for return to the environment. Increasing waste water loads on existing plants and more stringent government discharge requirements have put considerable pressure on the food-processing industry to refine and understand better the design and management of biological waste water treatment processes. Though activated sludge and other biological treatment processes are still frequently operated by general guidelines and ‘rules of thumb,’ facility design and operation must be guided by consideration of both the physical and biological aspects of waste water treatment. Various modifications and combinations of aerobic and anaerobic biological treatment processes are commonly used in the food-processing industry.
What is MF water treatment?
MF is used to remove turbidity and larger microorganisms. Water treatment in existing installations uses immersed membrane modules that are simply placed in water tanks where a vacuum at the permeate side drives the collection of purified water.
How to improve the taste of water?
1. Understand the treatment need: For many consumers, simply improving the taste of the water is their primary treatment need. For some, there may be health contaminants that must be treated. And others may have very hard water, causing issues with lime scale around fixtures and possibly damaging appliances. 2.
What will the future of brewing water systems be like?
Brewery water treatment systems of the future will be very flexible, allowing breweries to tailor-make their water for different products. At the same time, these future water treatment systems will aim to achieve optimum efficiency in terms of operating cost and especially wastewater produced. The advances in analysis techniques will inevitably lead to further challenges, as it will be possible to detect certain components that are not an issue today but will then need to be removed. It will also continue to be vital for brewers to pay attention to their water supply to avoid surprising and unexpected quality defects in the finished product.
What is the process of precipitation softening?
Precipitation Softening Process. Precipitation is typically accomplished with the lime-soda process. When lime is added to hard water, it causes a reaction with the carbonate hardness present producing solids that then must be removed from the water.
What happens if water is too soft?
Excessive hardness of finished water released in the distribution system may cause scaling and if the water is too soft, it can cause corrosion of the pipes. Thus, leaching out lead and copper which may lead to violation of the lead and copper rule (LCR).
Why use a digital titrator for hardness?
This is because the digital titrator dispenses the EDTA solution in very small increments with higher precision. Hardness test kits with digital titrator use the ManVer ® indicator.
What causes scale in water heaters?
This is the primary cause of scale formation in water heaters and boilers. Non-carbonate hardness is caused primarily by calcium and magnesium nitrates, chlorides and sulfates. Non-carbonate hardness is sometimes referred to as permanent hardness.
What are the minerals that precipitate with soap?
The minerals that precipitate with soap are represented by cations of polyvalent metals such as calcium, magnesium, iron, manganese and zinc. The concentration of calcium and magnesium in natural waters generally far exceeds that of any other polyvalent cation. Therefore, hardness is generally considered to be the concentration of calcium and magnesium ions in water.
Why is water softening necessary?
Therefore, water softening by either precipitation or ion exchange is often necessary to remove hardness.
Why is water important to mining?
Water is essential to metal and mining operations, but the industry is seldom the only consumer of water near extraction or processing sites. By monitoring and treating source water, mining companies not only ensure their own quality standards are met, but they also can contribute to the health of communities, agricultural resources and wildlife ecosystems in the process. Whether obtained from groundwater or precipitation, oceans or lakes, rivers or streams, through commercial or municipal supply—the water utilized in mining is interconnected with the water cycle of the entire region.
What happens when you raise the pH of a solution?
By raising the pH value of a solution with a common alkaline material such as lime, or sodium hydroxide the corresponding metallic hydroxide compounds become insoluble and precipitate from solution. Below is a metal hydroxide solubility curve showing the solubility of the common heavy metal ions and their respective solubility versus pH.
How to destroy ammonia ion?
The ammonia ion may be destroyed by oxidation with chlorine or ozone. Eliminating the ammonia destroys the complex. However, the cost is prohibitive when compared to other methods.
Is ferric hydroxide a co-precipitate?
Ferric hydroxide and/or aluminum hydroxide precipitate and tend to form co-precipitate with nickel and chromium. The net is a metallic ion concentration lower than would be predicted from the solubility curve.
What is hard water?
Hardness. Hard wateris usually defined as water which contains a high concentration of calcium and magnesium ions. Measurements of hardness are given in terms of the calcium carbonate equivalent (CaCO3), which is an expression of the concentration of hardness ions in water in terms of their equivalent value of calcium carbonate.
How hard is softened water?
In each of the treatment processes, the goal is the same. Softened water should have a hardness of about 80 to 90 mg/L as calcium carbon ate. If the water is softened further (as in the ion exchange process) then the hard water must be mixed with the softened water to achieve the desired hardness.
How does resin affect water hardness?
The depth of the resin bed will influence how much hardness can be removed from the water, with deeper beds removing more hardness. Operation of the softener during the softening phase can also influence efficiency. Specifically, the flow rate of the water through the softener influences how much hardness is removed.
Why is it important to soften water?
Hardness can cause soap scum, or scale inside of pipes, so softening the water is sometimes necessary to aid in household maintenance. The two main methods for softening drinking water is chemical precipitation, through the addition of lime-soda ash or caustic soda, and ion exchange.
What is the process of softening water?
Chemical precipitation and ion exchange are the two softening processes most commonly used. Softening of hard water is desired (for domestic users) to reduce the amount of soap used, increase the life of water heaters, and reduce encrustation of pipes. In each of the treatment processes, the goal is the same.
Which type of deposits have more hardness?
Areas with limestone (CaCO3) and dolomite (CaCO3and MgCO3) deposits have more hardness than others. Bicarbonates of calcium and magnesium are the most common forms of hardness. They are formed by the reaction of carbonic acid (H2CO3), which is carbon dioxide (CO2) dissolved in rain water, with carbonate deposits.
What is breakthrough in water softening?
Breakthrough requires the regeneration of the medium by bringing it into contact with a concentrated solution of sodium chloride. Ion exchange used in water softening has both advantages and disadvantages. One of its major advantages is that is produces a softer water than does chemical precipitation.
What is precipitation softening?
Precipitation softening processes are used to reduce raw water hardness, alkalinity, silica, and other constituents. This helps prepare water for direct use as cooling tower makeup or as a first-stage treatment followed by ion exchange for boiler makeup or process use. The water is treated with lime or a combination of lime and soda ash ...
What is the chemical that removes the hardness of water?
The water is treated with lime or a combination of lime and soda ash (carbonate ion). These chemicals react with the hardness and natural alkalinity in the water to form insoluble compounds. The compounds precipitate and are removed from the water by sedimentation and, usually, filtration.
What is the temperature of lime softener?
The warm lime softening process operates in the temperature range of 120-140°F (49-60°C). The solubilities of calcium, magnesium, and silica are reduced by increased temperature. Therefore, they are more effectively removed by warm lime softening than by cold lime softening.
Why is water contaminated in cold process softening?
Because the reactions in cold process softening are not complete, the water contaminant levels leaving the unit are unstable. With additional time and/or increased temperature, further precipitation will occur downstream of the unit. Frequently, acid or carbon dioxide is added to stabilize the water.
Does heating reverse the solution reaction?
In effect, heating reverses the solution reaction: Reduction of noncarbonate hardness, by contrast, requires chemical addition. A combination of lime and soda ash, along with coagulant and flocculant chemicals, is added to raw water to promote a precipitation reaction. This allows softening to take place.
What is Chapter 07?
Chapter 07 - Precipitation Softening. Precipitation soften ing processes are used to reduce raw water hardness, alkalinity, silica, and other constituents. This helps prepare water for direct use as cooling tower makeup or as a first-stage treatment followed by ion exchange for boiler makeup or process use.
Does sludge reduce silica?
Good sludge contact enhances silica reduction. To ensure optimum contact, sludge is frequently recirculated back to the inlet of the unit. Cold or warm process softening is not as effective as hot process softening for silica reduction. However, added magnesium oxide and good sludge contact will improve results.