Inlet and Outlet Arrangement in Water Treatment
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Questions and Answers

What is the main difference between intermittent and continuous sedimentation tanks?

  • Intermittent tanks are circular in plan, while continuous tanks are long rectangular.
  • Intermittent tanks keep water in complete rest, while continuous tanks only reduce flow velocity. (correct)
  • Intermittent tanks have horizontal flow, while continuous tanks have radial flow.
  • Intermittent tanks have high flow velocity, while continuous tanks bring water to complete rest.

    • Why are long rectangular basins preferred over circular basins for settling tanks?

  • Circular basins facilitate easier sludge scraping.
  • Circular basins have a shorter settling zone.
  • Long rectangular basins are hydraulically more stable. (correct)
  • Long rectangular basins have radial or spiral flow.

    • What is the purpose of the sludge zone in a long rectangular settling tank?

  • To collect sludge below the settling zone. (correct)
  • To uniformly distribute flow over the cross section.
  • To collect and discharge clarified effluent.
  • To facilitate settling under quiescent conditions.

    • Why is the bottom of a long rectangular settling tank slightly sloped?

    <p>To facilitate sludge scraping.</p> Signup and view all the answers

    How is the flow controlled in long rectangular settling basins?

    <p>By reducing flow velocity.</p> Signup and view all the answers

    What functional zone in a long rectangular settling tank collects and discharges clarified effluent?

    <p>Outlet zone</p> Signup and view all the answers

    What type of inlets should be designed to distribute water equally and at uniform velocities?

    <p>Inboard weirs</p> Signup and view all the answers

    Why are peripheral weirs not acceptable in settling basins?

    <p>They cause excessive short-circuiting</p> Signup and view all the answers

    What is the purpose of having a baffle close to the inlet in a settling basin?

    <p>To provide uniform flow</p> Signup and view all the answers

    What determines the size particle that can be completely removed in the settling zone?

    <p>$Q/As$</p> Signup and view all the answers

    What is the retention time in the settling zone for particle removal?

    <p>$t_0=Z_0/v_0$</p> Signup and view all the answers

    Which velocity component is used to determine the path of particles in a settling basin?

    <p>Vertical component ($v_t$)</p> Signup and view all the answers

    What is not a factor in determining the size particle that can be removed completely in the settling zone?

    <p>Depth of the basin</p> Signup and view all the answers

    Why are circular settling basins easier to maintain compared to long rectangular basins?

    <p>They require less maintenance for sludge removal mechanisms</p> Signup and view all the answers

    $t_0=V=LZ_0W$. 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

    <p>$Z_p/v_t=t_0$</p> Signup and view all the answers

    $Q$ is mentioned in connection with which of the following factors to determine overflow rate?

    <p>$v_0=Q/AS$</p> Signup and view all the answers

    What is the assumed detention period for the design of the sedimentation tank?

    <p>3 hours</p> Signup and view all the answers

    What is the relationship between the length (L) and breadth (B) of the rectangular tank?

    <p>L = 3B</p> Signup and view all the answers

    Which type of colloids are solvent hating and irreversible upon heating?

    <p>Lyophobic colloids</p> Signup and view all the answers

    What is the main reason for the stability of colloids?

    <p>Preferential adsorption of ions</p> Signup and view all the answers

    What mechanism is responsible for destabilizing a colloidal dispersion by changing the characteristics of the medium?

    <p>Compression of double layer</p> Signup and view all the answers

    'Flocculation' in water treatment refers to...

    <p>The stimulation of destabilized particles into fast settleable flocs</p> Signup and view all the answers

    What does the electrical double layer in a colloidal dispersion contain?

    <p>A balanced quantity of counter ions</p> Signup and view all the answers

    'Tyndall effect' is observed in colloidal solutions due to...

    <p>Brownian motion</p> Signup and view all the answers

    'Brownian motion' in colloids is caused by...

    <p>Bombardment by molecules of dispersion medium</p> Signup and view all the answers

    What is the purpose of rapid mixing in water treatment?

    <p>To achieve uniform dispersion of a coagulant</p> Signup and view all the answers

    In what type of flocculation do colloidal particles collide due to fluid motion from stirring?

    <p>Orthokinetic flocculation</p> Signup and view all the answers

    What is the acceptable range for head loss during rapid mixing in water treatment?

    <p>20 to 60 cms</p> Signup and view all the answers

    Which factor is used to estimate velocity gradient (G) in a fluid system?

    <p>Viscosity of the fluid</p> Signup and view all the answers

    What is the mechanism by which Al(III) and Fe(III) salts destabilize colloids in water treatment?

    <p>Charge neutralization and precipitation of metal hydroxides</p> Signup and view all the answers

    What purpose does a jar test serve in water treatment?

    <p>To determine the optimum operating conditions</p> Signup and view all the answers

    Which type of flocculation involves colloidal particle collisions due to Brownian motion?

    <p>Perikinetic flocculation</p> Signup and view all the answers

    What is the primary role of mechanical flocculators in water treatment?

    <p>To facilitate collisions between colloidal particles</p> Signup and view all the answers

    How do Al(III) and Fe(III) salts destabilize colloids when added to water?

    <p>By inducing charge neutralization and sweep floc formation</p> Signup and view all the answers

    What allows adjustments of pH, coagulant dose, and mixing speed in water treatment processes on a small scale?

    <p>Jar tests</p> Signup and view all the answers

    What is the purpose of the jar testing apparatus?

    <p>To determine optimal operating conditions by adjusting variables like pH and coagulant dosage.</p> Signup and view all the answers

    What is the purpose of the rapid mix stage in the jar test procedure?

    <p>To disperse the coagulant throughout each container.</p> Signup and view all the answers

    Which filtration mechanism is due to the force of gravity and settling velocity of particles?

    <p>Sedimentation</p> Signup and view all the answers

    What is the role of gravel in the filtration process using sand as a filter media?

    <p>To allow filtered water to move freely to the under drains.</p> Signup and view all the answers

    How is the size of sand particles expressed?

    <p>By effective size, which is the size of sieve through which 10% passes.</p> Signup and view all the answers

    What does slow sand filter consist of?

    <p>Fine sand supported by gravel.</p> Signup and view all the answers

    In the jar test procedure, what is done after allowing containers to settle for 30 to 45 minutes?

    <p>&quot;Reducing stirring speed to promote floc formation.&quot;</p> Signup and view all the answers

    "What does diffusion towards media granules occur for according to the text?"

    <p>&quot;Very small particles like viruses.&quot;</p> Signup and view all the answers

    What is the Carman-Kozeny equation used to calculate?

    <p>Head loss</p> Signup and view all the answers

    What is the recommended action if a filter run reaches a given hour of operation?

    <p>Backwash the filter</p> Signup and view all the answers

    What phenomenon occurs if the resistance offered by the filter media exceeds the static head of water above the sand bed?

    <p>Air binding</p> Signup and view all the answers

    What is the main cause of cracking in rapid sand filters?

    <p>Shrinkage of fine sand in the top layers</p> Signup and view all the answers

    What is the primary function of backwashing a rapid sand filter?

    <p>To expand and agitate the filter media</p> Signup and view all the answers

    What should be done to prevent formation of mud balls in rapid sand filters?

    <p>Wash the filter with a caustic soda solution</p> Signup and view all the answers

    What action is recommended if the filter no longer produces water at the desired rate?

    <p>Backwash the filter</p> Signup and view all the answers

    What is the main issue associated with long filter runs without backwashing?

    <p>Increased turbidity in filter effluent</p> Signup and view all the answers

    How does air binding affect the filtering process in rapid sand filters?

    <p>Halts filtering process</p> Signup and view all the answers

    What is the purpose of breaking the top fine mud layer with rakes in rapid sand filters?

    <p>To remove accumulated mud</p> Signup and view all the answers

    What is the primary method of cleaning Rapid-sand filters?

    <p>Backwashing the filter bed</p> Signup and view all the answers

    Which filter consists of two or more layers of different granular materials?

    <p>Multimedia filter</p> Signup and view all the answers

    What process removes impurities in slow sand filters by straining and adsorption?

    <p>Physical-chemical action</p> Signup and view all the answers

    What is the purpose of the layer referred to as 'Schmutzdecke' in slow sand filtration?

    <p>To break down organic material</p> Signup and view all the answers

    Which filter type is suitable for treating waters with low colors, low turbidities, and low bacterial contents?

    <p>Slow sand filter</p> Signup and view all the answers

    What is the primary base material size difference between Sand Filters and Rapid Sand Filters?

    <p>3 to 65 mm in SSF and 3 to 40 mm in RSF</p> Signup and view all the answers

    Which filter type requires post-treatment disinfection as a must?

    <p>Rapid-sand filter</p> Signup and view all the answers

    What is the primary method of cleaning Slow Sand Filters?

    <p>Scraping the top layer of sand</p> Signup and view all the answers

    What is one major difference between Slow Sand Filters and Rapid Sand Filters?

    <p>Rate of filtration - Large vs. Small</p> Signup and view all the answers

    Which characteristic makes Rapid Sand Filters more flexible compared to Slow Sand Filters?

    <p>Ability to handle varying demands</p> Signup and view all the answers

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