66 Questions
What type of tanks keep water in complete rest for a certain period?
Intermittent tanks
Which type of settling basins are generally preferred due to their hydraulic stability?
Long rectangular basins
What is the function of the inlet zone in a long rectangular settling tank?
Uniformly distribute the flow
What is the primary function of the sludge zone in a settling tank?
Collect settled material
Why are long rectangular settling basins considered easier for flow control?
They are hydraulically more stable
What distinguishes continuous flow type tanks from intermittent tanks?
Flow velocity is reduced
What is the purpose of constructing a baffle close to the inlet in a settling basin?
To distribute water equally and at uniform velocities
Why are peripheral weirs not acceptable in settling basins?
They cause excessive short-circuiting
In circular settling basins, what is the path of particles as the flow moves radially towards the perimeter?
Parabola
What is the formula for the vertical settling velocity of particles in a settling basin?
$vt = \frac{(ρp - ρ )gd^2}{18μ}$
What is the surface area of the rectangular sedimentation tank designed to treat 2.4 million litres of raw water per day?
100 m2
How is the horizontal velocity of water affected in a circular settling basin as the distance from the center increases?
Decreases
What is the assumed depth of the rectangular sedimentation tank designed to treat 2.4 million litres of raw water per day?
3.0 m
What is the determining factor for the size particle that can be completely removed in the settling zone?
$Q/As$
What is the detention period recommended for coagulated sedimentation in settling basins?
2 to 2.5 hours
What determines the magnitude of energy barrier that must be overcome before aggregation occurs in a colloidal dispersion?
Charge on the colloidal particles
Which type of colloids are described as irreversible upon heating?
Lyophobic colloids
What are the recommended tank dimensions for rectangular settling basins?
$L:B = 3:1$
What process involves stimulation by mechanical means to agglomerate destabilized particles into compact, fast settleable flocs?
Flocculation
What is the velocity of flow recommended for horizontal flow in settling basins?
< 30 cm/min
What is the term used for the motion of colloidal particles due to bombardment by molecules of the dispersion medium?
Brownian motion
What is the surface overflow rate recommendation for thoroughly flocculated water in settling basins?
$24000$ to $30000$ L/d/m2 tank area
Which step in the aggregation of colloidal particles involves particle transport to effect interparticle collision?
Flocculation
What is responsible for providing bridges that lead to enmeshment in a precipitate and adsorption and interparticle bridging?
Providing bridges
What effect occurs when colloidal particles pass through the pores of filtration media due to their small size?
Tyndall effect
"The stability of colloids is mainly due to preferential adsorption of ions" reflects which property of colloids?
Electrical properties
What is the purpose of reducing the stirring speed to 25 to 35 rpm in the jar testing apparatus?
To promote floc formation by enhancing particle collisions
Which filtration mechanism is only important for particles with diameters less than 1 micron?
Brownian diffusion
What is the term used to express the size of sand particles that will pass through a sieve?
Effective size
Which material can sometimes be used as an alternative to sand as filter media?
Anthrafilt
What does the sedimentation mechanism rely on to capture particles?
Gravity and settling velocity of particles
What is the purpose of allowing the containers in the jar testing apparatus to settle for 30 to 45 minutes?
To remove impurities still further
What is the role of gravel in the filtration process?
Support the layers of sand
Which type of filter consists of fine sand supported by gravel?
Slow sand filter
What is the mechanism responsible for capturing large particles that follow streamlines close to the media surface?
Interception
What does Brownian diffusion mechanism rely on for particle movement?
Thermal gradients
What is the purpose of rapid or flash mixing in the water treatment process?
To form the nucleus for floc formation
In perikinetic flocculation, how do colloidal particles come into contact for floc formation?
Through Brownian motion of colloidal particles
Which parameter is utilized to estimate the velocity gradient in a system involving orthokinetic flocculation?
$P$ (Power)
How do Al(III) and Fe(III) salts accomplish destabilization in water treatment?
By absorption and charge neutralization
What is the key factor that controls the precipitation of amorphous metal hydroxides during coagulation?
$ ext{pH}$ (Hydrogen ion concentration)
What is the primary function of a jar test in water or wastewater treatment?
To predict large-scale treatment operation outcomes
Which type of flocculation involves contacts or collisions of colloidal particles due to Brownian motion?
Perikinetic
What is the purpose of mechanical flocculation in water treatment?
To create contacts between colloidal particles
${Al(H_2O)_3^+}$ and ${Fe(HO)_3^+}$ are examples of what in water treatment?
Soluble species
${Alum}$ reacts with natural alkalinity in water to produce what compound?
${Al(OH)_3(s)}$
What is the base material size range in Rapid Sand Filters?
3 to 40 mm
Which process helps slow sand filters remove impurities mainly during the first few days?
Sedimentation
How is a slow sand filter's rate of filtration compared to a rapid sand filter?
Smaller
What is the effective size range of filter sand in Rapid Sand Filters?
0.35 to 0.55 mm
Which method is used for cleaning Rapid Sand Filters?
Agitating and backwashing
What does the 'Schmutzdecke' refer to in slow sand filtration?
Living quarters of micro-organisms
What type of water is obtained directly from Slow Sand Filters?
'Almost' pure water
How does the loss of head compare between Slow Sand Filters and Rapid Sand Filters?
Initial loss is higher in SSF
'Schmutzdecke' becomes living quarters for micro-organisms that break down organic material and convert it into what products?
'Water, carbon dioxide, and other oxides'
'Multimedia filters' consist of how many layers of different granular materials?
$3$ layers
What is the formula for head loss in the Carman-Kozeny equation?
h = f (1 - n) Lvs^2 Φ n^3 dg
What does the porosity 'n' represent in the Carman-Kozeny equation?
Particle shape factor
Why is it not recommended for filters to run for longer periods without backwashing?
To avoid packing down of filter media
What is the condition that indicates the need for backwashing a filter according to the text?
High turbidity in filter effluent
What issue arises when the frictional resistance exceeds the static head of water in a newly commissioned filter?
Air binding
What is the phenomenon known as when air binds to the sand grains in a filter?
Air binding
Why does the bottom sand layer act like a vacuum in a filter experiencing air binding?
To aid water filtration
What is done to prevent shrinkage cracks in a filter bed according to the text?
Washing with caustic soda solution
What is generally used to clean filters that have mud balls formed on them?
Caustic soda
What is recommended to be not less than 60 times its diameter in a Rapid Sand Filter?
Lateral length
This quiz covers the design requirements for inlet and outlet devices in water treatment basins, focusing on distributing water equally, dissipating inlet velocities, and maintaining suitable velocities for settling. Test your knowledge on proper water flow arrangements!
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