Bissoy.com
Doctors Medicines MCQs Q&A

Statement I): Incrustation of sand occurs in rapid sand filter when water softened by lime-soda is fed in for filtration. Statement II): The sand gets coated with precipitates of Ca(OH)2 and Mg(OH)2 generated during softening of water by lime-soda process which leads to incrustation of sand.

Statement I): Incrustation of sand occurs in rapid sand filter when water softened by lime-soda is fed in for filtration. Statement II): The sand gets coated with precipitates of Ca(OH)2 and Mg(OH)2 generated during softening of water by lime-soda process which leads to incrustation of sand. Correct Answer Statement I) is true but Statement II) is false

Incrustation of sand occurs in rapids sand filter when water softened by lime soda is fed in for filtration. During lime soda process, PPT of calcium carbonate (not calcium hydroxide) is formed along with magnesium hydroxide which leads to incrustation.

If water containing such amount of sludge is passed through, it may choke the filter i.e. precipitated sludge gets filled in voids of filter media particles or sand incrustation occurs.

Sand incrustation may also occur either due to deposition of sticky gelatins materials from the influent water or due to crystallization of calcium carbonate.

Related Questions

The following are certain operating problems of a rapid sand filter: 1. Sand depth should never be depleted by more than 10 cm. 2. Air binding results due to development of negative head and formation of air bubbles in the filter sand. 3. Water softening with lime-soda leads to incrustation of sand. 4. Bumping of filter bed is caused due to negative head. Which of the above statements are correct?
Consider the following statements in respect of slow sand filter and rapid sand filter: 1. The two filters differ in respect of the standards regarding the non-uniformity of the sand used in their filtering media. 2. The two filters do not differ in respect of the effective size of the sand used in them. 3. The two filters differ in respect of their respective under-drainage system. 4. The two filters differ in respect of their respective rate of filtration. Which of the above statements are correct? 
Which of the following statements are correct pertaining to the value of uniformity coefficient Cu for filter sand? (1) For slow sand filters, Cu = 1.8 to 2.5 (2) For rapid sand filters, Cu = 1.3 to 1.7 (3) For slow sand filters, Cu = 1.3 to 1.7 (4) For rapid sand filters, Cu = 1.8 to 2.5
A rotary drum filter with 30% submergence is used to filter concentrated aqueous slurry of calcium carbonate containing 15lb of solids per cubic foot of water. The pressure–drop is 2011Hg. If the filter cake contains 50% mixture (wet basis), calculate the filter area required to filter 10 gal/min of slurry. The filter cycle time is 5 min. The specific cake resistance depends on the pressure–drop as: α (ft/lb) = α (Δp)0.26, where α = 2.90×1010 Viscosity of the filtrate = 6.72×10-4 lb/ft-s. Density of calcium carbonate = 168.8 lb/ft3. Neglect filter medium resistance.
Consider the following statement. i. Slow sand filter is not flexible in variation in demand ii. The rapid sand filter is flexible in fluctuations in demand iii. The method of cleaning of a slow sand filter involves agitation and back-washing Which of the above statement is/are correct?
Consider the following statement. i. The penetration of suspended matter is deep in the slow sand filter ii. The penetration of suspended matter is superficial in the rapid sand filter iii. Coagulation is not required in the slow sand filter Which of the above statement is/are correct?
In a batch process, the reaction takes place in the presence of an acid medium. The acid is drained from the reaction vessel at the rate of 15ml/s as a result of the density difference of the acid from the reacting component. To avoid wastage of acid, it is recycled to an acid tank which has 1000 L capacity. The acid drained from the reaction vessel, picks up 50 g/L solids from the reactor. Acid is fed once again to the process from acid tank. When the process is started, the acid is almost pure in the tank as a result of filtration. As the reaction proceeds, acid in the tank gets more and more contaminated with the solids. The concentration of the solids should not exceed 100 g/L from the process point of view. The batch time is 16h. Estimate whether the concentration of the solids will exceed 100g/L during the batch reaction.
Statement 1: Incrustation may lead to under deposit-corrosion. Statement 2: Scrapers can be used as an agitated medium to avoid incrustation.
A sum of Rs. 12,500 is distributed among A, B, C and D such that A gets Rs. 800 more than what B gets, C gets twice of what B gets and D gets Rs. 900 more than what A gets. The ratio in which D, C, B and A receive the sums is:
Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters.Reason R: The sand used in slow sand filters is finer than that in rapid sand filtersSelect your answer based on the coding system given below: