63 Questions
What is the main difference between intermittent and continuous sedimentation tanks?
Intermittent tanks keep water in complete rest, while continuous tanks only reduce flow velocity.
Why are long rectangular basins preferred over circular basins for settling tanks?
Long rectangular basins are hydraulically more stable.
What is the purpose of the sludge zone in a long rectangular settling tank?
To collect sludge below the settling zone.
Why is the bottom of a long rectangular settling tank slightly sloped?
To facilitate sludge scraping.
How is the flow controlled in long rectangular settling basins?
By reducing flow velocity.
What functional zone in a long rectangular settling tank collects and discharges clarified effluent?
Outlet zone
What type of inlets should be designed to distribute water equally and at uniform velocities?
Inboard weirs
Why are peripheral weirs not acceptable in settling basins?
They cause excessive short-circuiting
What is the purpose of having a baffle close to the inlet in a settling basin?
To provide uniform flow
What determines the size particle that can be completely removed in the settling zone?
$Q/As$
What is the retention time in the settling zone for particle removal?
$t_0=Z_0/v_0$
Which velocity component is used to determine the path of particles in a settling basin?
Vertical component ($v_t$)
What is not a factor in determining the size particle that can be removed completely in the settling zone?
Depth of the basin
Why are circular settling basins easier to maintain compared to long rectangular basins?
They require less maintenance for sludge removal mechanisms
$t_0=V=LZ_0W$. If $t_0$ corresponds to the time required for a column to be carried horizontally across the settling zone, what will happen to particles with $v_t
$Z_p/v_t=t_0$
$Q$ is mentioned in connection with which of the following factors to determine overflow rate?
$v_0=Q/AS$
What is the assumed detention period for the design of the sedimentation tank?
3 hours
What is the relationship between the length (L) and breadth (B) of the rectangular tank?
L = 3B
Which type of colloids are solvent hating and irreversible upon heating?
Lyophobic colloids
What is the main reason for the stability of colloids?
Preferential adsorption of ions
What mechanism is responsible for destabilizing a colloidal dispersion by changing the characteristics of the medium?
Compression of double layer
'Flocculation' in water treatment refers to...
The stimulation of destabilized particles into fast settleable flocs
What does the electrical double layer in a colloidal dispersion contain?
A balanced quantity of counter ions
'Tyndall effect' is observed in colloidal solutions due to...
Brownian motion
'Brownian motion' in colloids is caused by...
Bombardment by molecules of dispersion medium
What is the purpose of rapid mixing in water treatment?
To achieve uniform dispersion of a coagulant
In what type of flocculation do colloidal particles collide due to fluid motion from stirring?
Orthokinetic flocculation
What is the acceptable range for head loss during rapid mixing in water treatment?
20 to 60 cms
Which factor is used to estimate velocity gradient (G) in a fluid system?
Viscosity of the fluid
What is the mechanism by which Al(III) and Fe(III) salts destabilize colloids in water treatment?
Charge neutralization and precipitation of metal hydroxides
What purpose does a jar test serve in water treatment?
To determine the optimum operating conditions
Which type of flocculation involves colloidal particle collisions due to Brownian motion?
Perikinetic flocculation
What is the primary role of mechanical flocculators in water treatment?
To facilitate collisions between colloidal particles
How do Al(III) and Fe(III) salts destabilize colloids when added to water?
By inducing charge neutralization and sweep floc formation
What allows adjustments of pH, coagulant dose, and mixing speed in water treatment processes on a small scale?
Jar tests
What is the purpose of the jar testing apparatus?
To determine optimal operating conditions by adjusting variables like pH and coagulant dosage.
What is the purpose of the rapid mix stage in the jar test procedure?
To disperse the coagulant throughout each container.
Which filtration mechanism is due to the force of gravity and settling velocity of particles?
Sedimentation
What is the role of gravel in the filtration process using sand as a filter media?
To allow filtered water to move freely to the under drains.
How is the size of sand particles expressed?
By effective size, which is the size of sieve through which 10% passes.
What does slow sand filter consist of?
Fine sand supported by gravel.
In the jar test procedure, what is done after allowing containers to settle for 30 to 45 minutes?
"Reducing stirring speed to promote floc formation."
"What does diffusion towards media granules occur for according to the text?"
"Very small particles like viruses."
What is the Carman-Kozeny equation used to calculate?
Head loss
What is the recommended action if a filter run reaches a given hour of operation?
Backwash the filter
What phenomenon occurs if the resistance offered by the filter media exceeds the static head of water above the sand bed?
Air binding
What is the main cause of cracking in rapid sand filters?
Shrinkage of fine sand in the top layers
What is the primary function of backwashing a rapid sand filter?
To expand and agitate the filter media
What should be done to prevent formation of mud balls in rapid sand filters?
Wash the filter with a caustic soda solution
What action is recommended if the filter no longer produces water at the desired rate?
Backwash the filter
What is the main issue associated with long filter runs without backwashing?
Increased turbidity in filter effluent
How does air binding affect the filtering process in rapid sand filters?
Halts filtering process
What is the purpose of breaking the top fine mud layer with rakes in rapid sand filters?
To remove accumulated mud
What is the primary method of cleaning Rapid-sand filters?
Backwashing the filter bed
Which filter consists of two or more layers of different granular materials?
Multimedia filter
What process removes impurities in slow sand filters by straining and adsorption?
Physical-chemical action
What is the purpose of the layer referred to as 'Schmutzdecke' in slow sand filtration?
To break down organic material
Which filter type is suitable for treating waters with low colors, low turbidities, and low bacterial contents?
Slow sand filter
What is the primary base material size difference between Sand Filters and Rapid Sand Filters?
3 to 65 mm in SSF and 3 to 40 mm in RSF
Which filter type requires post-treatment disinfection as a must?
Rapid-sand filter
What is the primary method of cleaning Slow Sand Filters?
Scraping the top layer of sand
What is one major difference between Slow Sand Filters and Rapid Sand Filters?
Rate of filtration - Large vs. Small
Which characteristic makes Rapid Sand Filters more flexible compared to Slow Sand Filters?
Ability to handle varying demands
Learn about the design requirements for inlet and outlet devices in water treatment systems. Understand how to ensure equal water distribution, uniform velocities, and minimize short-circuiting for effective settling in basins.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
