Coagulation And Flocculation Questions Flashcards
What you call the clumping together of very fine particles into large particles (floc) after the edition of a chemical?
Coagulation
WTP operators are mainly concerned with particles that have what type of charge?
Negative charge
The capacity of water to neutralize acid is called?
Alkalinity
What parameter is measured when water is titrated with 0.2 N (H²SO⁴) to a pH of 4.5?
Total alkalinity
Water color that includes not only the color due to substances in the water, but suspended matter as well is called?
Apparent color
Water color that includes not only the color due to substances in the water, but suspended matter as well is called?
Apparent color
Water color of a sample that has had turbidity removed is called ?
True color
A polymer that has a positive charge is?
Cationic polymer
A polymer that is often used as a filter aid is called?
Non-ionic
Where is the filter aid added?
Filter influent
A negatively charged polymer is called
Anionic
A collection of individual samples obtained at regular intervals, usually every one or two hours during a 24-hour period and combined in proportion to the flow is called?
Composite sample
⭐ A contaminant formed by the reaction of disinfection chemicals, with other substances in the water being disinfected is called?
Disinfectant by- product ( DBP)
The gathering together of fine particles after coagulation to form large particles by a process of gentle mixing is called?
Flocculation
A single sample of water collected at a particular time and place, which represents the composition of the water only at the time and place, is called?
Grab sample
What test is used to determine the correct chemical dose during water treatment?
Jar test
⭐ The sum of the atomic weight of the element in a compound is used to determine?
Molecular weight
A sample portion of water that is as nearly identical in content and consistency as possible to that in the larger body of water being sampled is called?
Representative sample
⭐ a condition that occurs in tanks or basins when some of the flowing water entering a tank or basin flows along a nearly direct pathway from the inlet to the outlet is known as?
Short- circuiting
⭐ The cloudy appearance of water caused by the presence of suspended and colloided matter is called?
Turbidity
⭐ What parameter is obtained when you measure the optical property of water based on the amount of light reflected by suspended particles?
Turbidity
What are three types of solids found in water?
Settable, suspended, and dissolved
When the coagulant sodium aluminate is added to water, what happens to the pH?
pH goes up
When aluminum Sulfate (alum) is added to the water. What happens to the pH?
The pH goes down
When the alum dosage is decreased, what generally happens with the lime dosage?
Lime dosage decrease
When the alum dosage is increased, what normally takes place with the lime dose?
Lime dosage increases
A physical and chemical reaction occurring between the alkalinity of the water and the chemical added which results in the formation of insoluble floc is called?
Coagulation
When using alum as a coagulant, the most effective pH range for the water is?
Between 5 and 7 pH
What is the best pH range for coagulation?
It depends on the coagulant used
What water treatment process is known as “flashmix”?
Coagulation
The coagulation process requires what amount of detention time?
Less than a minute, a few seconds
The flocculation process takes place in what length of time?
5 to 30 minutes
Reducing the speed of the mixers in each succeeding tank to lower the turbulence is called?
Tapered energy mixing
What type of floc should be formed during flocculation?
Discrete and fairly dense, popcorn. Flake
What is considered the best chemical dosage obtained during coagulation?
The dosage, which produces finish water that meets drinking water standards at the lowest cost.
During the jar test, the floc starts to settle before the mixer is turned off, and 80% of the floc is settled within 1 to 2 minutes. What does this indicate?
Overdosage
Jar tests are useless unless?
Applied and verified
During a jar test, the floc starts settling after the mixer is turned off and 80% of the flock settles within 15 minutes. What does this indicate?
Good settling dosage
During a plant tour, the operator notices a small, well dispersed floc throughout the flow. What action is needed?
None. This is good treatment
⭐ If the operator does not notice a small, well-dispersed floc, what is a likely cause?
Chemical dosage or feed rate too low; flash mixer not providing effective mixing
The water treatment plant is using alum as a coagulant. The floc being formed is tiny. What does this indicate?
Under dosage
In the solids contact unit, the water appears to have a bluish tiny or milky color. What is the likely cause?
Overdose of alum
As the floc enters the flocculation basin, the size of the floc increases. As it flows through the basin the floc starts to break up. What is the likely cause?
Flocculator/ floc mixer speed too high
In question 43, what action is needed to correct the problem?
Reduce flocculator speed or increase dosage
⭐ during a plant tour, the operator notices floc flowing over the laundering Weirs. What is the likely cause?
Floc too light for the detention time produced by the flow rate / coagulant underdosage / alkalinity too low
⭐ in problem 45, alum is the coagulant being used. The floc is too tiny and has a very fine appearance. What is the likely cause?
Alum underdose, correct by increasing the dosage.
If alkalinity is an important factor in coagulation, what parameters in the water must the operator measure?
Alkalinity
⭐ if the turbidity of the raw water increases, what action is usually taken to ensure good coagulation?
Increase coagulant dosage
When water temperature decreases, what action is needed to ensure good coagulation?
Increase coagulant dosage
In enhanced coagulation, where is the acid added?
Prior to coagulation
