[Solved] What will happen when the alum is mixed with water as coagul (2024)

FAQs

What will happen if the alum mix with the water as a coagulant decrease pH value of water Dosent change pH value increase pH value none of the above? ›

Addition of alum in water treatment increases the acidity of water as carbon dioxide gas is released, which leads to the formation of carbonic acid, thereby, increasing the acidity of water and decreasing the pH.

Alum removes the suspended clay particles from water. Alum helps to remove odour from water.

In this case, aluminum hydroxide (Al(OH)2) precipitates forming a “sweepfloc” that tends to capture suspended solids as it settles out of suspension. The pH of the water plays an important role when alum is used for coagulation because the solubility of the aluminum species in water is pH dependent.

Operators add alum to the pretreatment process to increase the efficiency of the sand filters as they make irrigation water from wastewater.

Detailed Solution. Concept: When alum is added in water, it reacts with alkalinity present in water and leads to formation of sticky gelatinous precipitate of Aluminium hydroxide which attracts fine suspended impurities in water over its surface and gets easily settled in the following sedimentation process.

Coagulation treatment is usually carried out before sedimentation and filtration. During the process, a coagulant is added to water, and its positive charge neutralizes the negative charge of suspended contaminants. Neutralization causes suspended particles to bind together (hence the term).

Aluminium sulfate or alum is used as a flocculant to remove colour and turbidity from water supplies. The alum promotes coagulation of fine particles. Once coagulated, they sediment down.

results in increase of pH of the treated water.

The most commonly used inorganic chemical coagulants in water treatment. Aluminium sulfate is the most commonly used chemical for coagulation in wastewater treatment. Additional commonly used coagulants include sodium aluminate, ferric sulfate, and ferric chloride.

Ferric hydroxides can be formed over a relatively wide pH-range between pH 5 and pH 11 while the use of alum coagulants is restricted to pH 6 to 7.2.

When coagulants are dissolved in water and thoroughly mixed with it they produced a thick gelatinous precipitate This precipitate is known a? ›

Principle of coagulation

When coagulants are dissolved in water and thoroughly mixed with it, they produce a thick gelatinous precipitate. This precipitate is known as floc and this floc has got the property of arresting the suspended impurities in water during its downward travel towards the bottom of tank.

By adding alum, alkalinity of water is reduced and infact alkalinity reduces, ph reduces. Alum works when water is alkaline(6.5 - 8.5)pH. When alum added to water, then pH decrease i.e., the alkalinity of water increase.

One widely used class of such additives are termed coagulants and are typically inorganic salts with polyvalent ions. Unfortunately, addition of too much coagulant (overdosing) causes charge reversal resulting in restabilization of the suspended solids with a resultant deterioration in subsequent processing.

This is because of higher alkaline nature of coagulants. In this series of studies, it was revealed that alum works quite effectively in removing turbidity in muddy water, and its efficiency gets improved with low pH at or around 6.

Blood clots and coagulation

Blood vessels shrink so that less blood will leak out. Tiny cells in the blood called platelets stick together around the wound to patch the leak. Blood proteins and platelets come together and form what is known as a fibrin clot. The clot acts like a mesh to stop the bleeding.

The coagulated substance can be removed by filtration or decantation. Hence, alum is added to water containing suspended impurities to coagulate the suspended particles. So, option b) is the correct answer to the given question.

Aluminum sulfate (alum) is the most common coagulant used for water purification. Other chemicals, such as ferric sulfate or sodium aluminate, may also be used. Coagulation is usually accomplished in two stages: rapid mixing and slow mixing.

Explanation: Alum is the most common and universal coagulant used in water treatment having chemical composition Al₂ (SO₄) ₃. 18H₂O.

(iii) Coagulants used are Aluminium sulphate (Alum), Ferrous sulphate (Copperas), Ferric sulphate and ferric chloride, and Sodium aluminate. Alum is a universal coagulant. It produces effective floc in the water when the pH of water is in the range of 6.5-8.5(alkaline range).

Explanation: Alum or ​Aluminium sulphate is most commonly used as coagulants in water treatment.

What is the process of coagulation in water? ›

Coagulation is the chemical water treatment process used to remove solids from water, by manipulating electrostatic charges of particles suspended in water. This process introduces small, highly charged molecules into water to destabilize the charges on particles, colloids, or oily materials in suspension.

Coagulants and flocculation processes are used to remove colloidal impurities: suspended particles such as bacteria, clay, silts, and organic matter from the contaminated water. This produces large flock aggregates that can be removed from the water in subsequent clarification/filtration processes.

The coagulation process involves adding iron or aluminum salts, such as aluminum sulphate, ferric sulphate, ferric chloride or polymers, to the water. These chemicals are called coagulants, and have a positive charge.

pH EFFECTS

pH that is too low may not allow the coagu- lation process to proceed, while high pH can cause a coagulated particle to redisperse. The size of the coagulated particles is also affected by pH, which, in turn, determines the density of the flocculated slime and its tendency and rate of settling out.

The high ionic strength promotes flocculation of the blood and the astringent chemical causes local vasoconstriction. Thus, blood is negative sol and sol particles are coagulated more efficiently by Al3+ ions. Was this answer helpful?

Since pH values affect the surface charges and forms of the coagulants and impurities to be removed, controlling the level of pH would significantly improve the coagulation process. Therefore, not only coagulant dosage, but also pH value should be optimized to maximize the removal of impurities present in raw water.

The experiment showed that the pH value was reduced after settling with alum. When alum is added, the pH and alkalinity of water tend to decrease. Because alum is added in the sample, the reaction is broken down into cations and negative ions.

Alum (aluminum sulfate; Al2(SO4)3. 14H2O) is acidic in water and can reduce total alkalinity and pH by neutralizing carbonate and bicarbonate compounds with a greater decline in pH when applied to water with low initial total alkalinity (Boyd 1979a; 1990; Wilkinson 2002).

pH EFFECTS

At varying sample pH values, the coagulation process may suffer from less than optimum ions being formed in solution. pH that is too low may not allow the coagu- lation process to proceed, while high pH can cause a coagulated particle to redisperse.

One widely used class of such additives are termed coagulants and are typically inorganic salts with polyvalent ions. Unfortunately, addition of too much coagulant (overdosing) causes charge reversal resulting in restabilization of the suspended solids with a resultant deterioration in subsequent processing.

How does coagulant work? ›

Coagulation treatment neutralizes the negative electrical charge on particles, which destabilizes the forces keeping colloids apart. Water treatment coagulants are comprised of positively charged molecules that, when added to the water and mixed, accomplish this charge neutralization.

Since pH values affect the surface charges and forms of the coagulants and impurities to be removed, controlling the level of pH would significantly improve the coagulation process. Therefore, not only coagulant dosage, but also pH value should be optimized to maximize the removal of impurities present in raw water.

The Purpose of Coagulants is to Coagulate

Everything else is just a side effect. While alum and ferric-based coagulants are acidic in nature and produce a drop in pH when added to wastewater, their main purpose is to neutralize electrical charges of fine particles in water and clump them together.

Make an alum solution by adding 7.5 grams of alum to one liter of tap water.

The factors that influence coagulation–flocculation are, among others, temperature, pH, effluent quality, dosage and coagulant type (Nnaji 2012; Jin 2005; Ma et al. 2001). The suspended particles vary considerably in source, composition charge, particle size, shape, and density.

The vast majority of coagulation problems are related to improper pH levels. The optimum pH range varies depending on the coagulants used, but is usually between 5 and 7. These lower pH values mean that there are more positively charged particles loose in the water to react with the negatively charged colloids.

The most common coagulants are salts of aluminum or trivalent iron, with aluminum being more commonly used.