There will be two take home prelims. All prelims are open notes, open internet, and in Colab Notebook format.

See the Syllabus to find out when the exams will be given.

Recent prelims

Note that the aguaclara repository has been evolving rapidly and thus the code used in the older prelims may not be supported.

• Prelim 1 2017
• Prelim 1 Spring 2019
• Prelim 2 2017

Prelim 1 Study Guide

Flow Control and Measurement

• What is the "hole in a bucket" solution to flow control and why doesn't it work well?
• How can the "hole in a bucket" solution be used to design the drain system for a tank?
• What determines the maximum flow that can be obtained from a laminar flow dosing tube?
• How does a dose controller work, what are the major components, and how does it integrate flow measurement and flow control?

Rapid Mix

• What is the role of turbulence in generating mixing?
• What is the significance of the Kolmogorov length scale?
• How does temperature influence the rapid mix process?

Vena Contracta

• Be able to draw (roughly) the critical streamline when the flow geometry causes a change in direction and a vena contracta
• Know whether or not a vena contracta will occur
• Mechanical vs. Hydraulic Flocculators
• What is the difference between horizontal and vertical flow hydraulic flocculators?
• How could a mechanical flocculator be designed to be more energy efficient?

Flocculation Model

• Understand the basic assumptions of the flocculation model
• What factors control collision rate?
• Approximately how many collisions are required to produce a large floc?
• What evidence do we have that suggests that colloids can't attach to large flocs?
• Why does it take less time to convert the first 90% of the colloids into flocs than it takes to convert the next 9% of the colloids into flocs?

Prelim 2 Study Guide

Sedimentation Theory and Design

• What determines the capture velocity for a horizontal flow sedimentation tank without plate settlers?
• What determine the capture velocity for a vertical flow sedimentation tank without plate settlers?
• The capture velocity for a sedimentation tank (horizontal flow, vertical flow, or vertical flow with plate settlers) is equivalent to the flow rate divided by the projected horizontal area where flocs can settle. Explain the advantage of plate settlers!
• What are the three zones (in addition to inlet and outlet zones) of a sedimentation tank and what function does each zone have?
• What is the capture velocity given geometry specifications and flow rate?
• How do you get a plate settler spacing given an upflow velocity and a plate length?
• What goes into calculating the depth of an AguaClara sedimentation tank?
• Why is the advantage of using plate settlers with a decreased spacing?
• What is the failure mode for decreasing plate settler spacing too far?
• Why are flocs that are less dense more prone to floc roll up?
• What problem did high horizontal velocities in the bottom of AguaClara sedimentation tanks cause and what was the source of this horizontal velocity?
• What problem did we discover at Agalteca with the inlet manifold pipes that appears to be responsible for causing flocs to flow up between the plate settlers at the end of the sed tank away from the inlet?
• How does the AguaClara design reduce horizontal velocities in the sedimentation tanks?
• If we decided we could increase the capture velocity of our sedimentation tanks without a significant decrease in performance…What would we spend less money on? (higher capture velocity means less plate settler material required)
• What is the advantage of using plate settlers that are spaced more closely than the 5 cm that is traditionally used? (Which do we use less of: concrete or plastic?) We save concrete because the tanks aren't as deep.
• Should the slide capture velocity be less than or greater than the settle capture velocity? (Slide capture velocity should be less than settle capture velocity. We want flocs that settle to the plate surface to slide down. If the slide capture velocity is greater than the settle capture velocity, then some flocs that settle will end up sliding up the plate.)

Floc Blankets

• How do floc blankets reduce the turbidity of the water leaving the sedimentation tank?
• Why is the Gtheta per small particlecollision in a floc blanket less than at the end of the flocculator?
• Why is it that AguaClara sedimentation tanks prior to Atima were not able to produce a floc blanket?
• What problem do flat sections in the bottom of sedimentation tank cause?
• What is the optimal upflow velocity for a floc blanket?
• Why can't conventional horizontal flow sedimentation tanks incorporate floc blankets?
• How are flocs removed from a sedimentation tank that incorporates a floc blanket?
• Why is the top of the floc blanket a horizontal surface?
• Why do flocs flow over the floc hopper weir?
• What is in the floc hopper before it fills with flocs?

Filtration

• How do the sizes of the various unit processes compare?
• How is the head loss through a fluidized bed obtained?
• What is the role of the dynamic filter in a multistage filtration plant?
• How is the upflow gravel filter cleaned?
• What is the advantage of the multistage filtration system?
• What is the head loss through a fluidized bed and how does it change with flow rate?
• What equation is used to estimate head loss through a clean filter bed?
• How do you estimate treatment plant size based on different treatment trains?