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• CEE 3310, or equivalent Fluid Dynamics course
• CEE 4540 co-requisite
• Students must be comfortable with coding
• Students should be familiar with the AguaClara design
• AutoCAD and/or MathCAD knowledge is a plus
• We are willing to train new members

Challenges

Design

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support for the APP/AguaClara team in Honduras

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Chemical Doser

We are currently switching from the LFOM and laminar flow controller to a submerged orifice flow meter and orifice based flow controller.

• Need to develop AutoCAD code to draw this part of the plant
• Need to develop the design algorithms for the orifice based dose controller

Entrance tank

• A first draft of this code has been created, but it has not yet been reviewed.
• The Rapid mix and Chemical Doser needs to be drawn in the entrance tank.

Rapid mix components

Requires review and possible upgrade to the first draft of the rapid mix design and then coding of the MathCAD to AutoCAD (MtA) code.

Chemical storage tanks

• These tanks need to be drawn. These may be an item that the onsite civil engineer will relocate to fit site conditions, but the design tool should show them at the correct elevation and in a reasonable location.

Floc Hopper Drain Valves

• The floc hopper can be put on hold for this semester because we haven't been able to create a floc blanket in a full scale AguaClara plant. This task can wait until we develop a method to create a floc blanket.

Horizontal Flocculator

Continue coding the flocculator to include the option for horizontal flocculation for large plants and determine the flow rate for the transition from vertical to horizontal flow.

• Document and describe the solution algorithm for the vertical flow flocculator
• Design a horizontal flow flocculator and develop a clear algorithm for the solution process
• Create the equation or system of equations that will determine whether a design will have a horizontal or vertical flow flocculator. The minimum flow for a vertical flow flocculator will be related to the minimum channel width given a channel width that is about 3 x the baffle spacing and the requirement that the baffle spacing be at least 45 cm for constructability.
• Develop a method to design both horizontal and vertical flow flocculators.
• Code the necessary drawing algorithms. Make the flocculator code as generic as possible to be able to handle both vertical and horizontal flocculators.
• Design and draw the drain system for horizontal flocculators.

Vertical Flocculator

• Need to ensure that the size of the ports between channels does not exceed the size available on the floc tank wall. Also, ensure that the spacing of the baffles in the last channel does not force them into the exit channel space (this may be taken care of by switching to horizontal flow).
• The drain system for vertical flow flocculators that are large enough that the baffles are ferrocement needs special attention. Code and draw the flocculator drain system.

Sedimentation Inlet and Exit Tanks

• The tanks at the end of the inlet and exit channels that hold the pipes leading to the distribution tank and to waste no longer need to be as tall as they are currently drawn. Rather they can just cantilever off the side of the sedimentation tank. Also the pipes in these tanks that lead to waste should be drawn as Tee's that connect to one another and then lead to waste.

Sedimentation Tank Control Pieces

• The pieces that allow the sedimentation tanks to be shut off need to be drawn (caps for the inlet channels, and exit channels). In addition, the caps should have a 1" PVC pipe that extends above the surface of the water in order to prevent air being trapped in the pipes delivering flocculated water to the sedimentation tank, and also to serve as a handle for removing the caps.

Materials List

• This list has been started and needs to be edited with input from the engineers in Honduras.

Documentation

• Continue the effort to create an AutoCAD video that will show the assembly of the plant with descriptions of each part. This video could serve as the documentation that gets sent to a user who designs a plant with the Design Tool that explains the technology behind each piece. This video will also be used for training and teaching. Ideally the video should be made using a series of commands based on the plant dimensions so that the video can be created automatically for different plant designs.
• Explore the possibility of creating

Research

Tube Floc

The development of FReTA and the data processing methods used to analyze its measurements has given AguaClara a powerful research tool. The investigation by Ian Tse into fluid shear influences on hydraulic flocculation was the first of many studies that could be performed with the tube floc/FReTA apparatus.

*Extend the experimental range evaluated by Ian Tse by increasing the length of the tube flocculator. One of the goals of this research is to measure the effect of collision potential on the residual turbidity.

Results of this study suggest several directions for future research into fluid shear influences on hydraulic flocculator performance. Present results clearly show that shear induced breakup significantly affects both the mean floc size and residual turbidity. Steady state floc sizes were observed at high velocity gradients, but not at low velocity gradients. Perhaps extending the length of the tube flocculator to twice or even three times the current length will provide new insights on how floc sizes and residual turbidities are affected at low velocity gradients.

Additionally, an investigation into the utility of tapered flocculation designs should be performed. Hydraulic flocculators in AguaClara plants are currently designed such that the energy dissipation rates incrementally decrease over the length of the flocculator. The present study showed that while the influences of shear induced breakup was evident early on in the flocculator, floc sizes were not nearly as limited by shear as they were later on in the flocculator.

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Review the Agalteca design and make sure that design improvements created since May of 2009 are incorporated in the design

• Eliminate floc hopper
• Add weirs at the end of the inlet and exit channels
• Add a drain line to the exit channel (it won't be possible to drain the exit channel with the weir in place unless we add a new drain line)
• Add a removable drain port in the bottom of the sed tank to facilitate cleaning
• Consider making the bottom of the sed tank have a steeper slope to facilitate cleaning of the distribution tunnels
• Consider making the sludge drain have fewer orifices that are then larger in diameter (perhaps eliminate half of the orifices)
• Set the maximum energy dissipation rate at the end of the flocculator to match the maximum energy dissipation rate at the end of the Marcala flocculator. Refer to the CEE 4540 notes on Flocculation

AguaClara Design Tool (ADT)

• Check that all pieces are scaling properly
• Identify design errors and work with the team in Honduras to develop improved design algorithms
• Update the list of variables that are returned to the user to ensure that all relevant parameters are returned.
• Eliminate variables in the Variable Naming Guide that aren't used.
• Develop a protocol to release new versions of the ADT. Begin by developing a method to create a stable release of the MathCAD files. Also develop a testing protocol that will use an independent check to verify that the plant dimensions are correct before releasing a new version.

Chemical Doser

We are currently switching from the linear flow orifice meter (LFOM) and laminar flow controller to a submerged orifice flow meter and orifice based flow controller.

• Need to develop AutoCAD code to draw this part of the plant
• Need to develop the design algorithms for the orifice based dose controller

Entrance tank

• A first draft of this code has been created, but it has not yet been reviewed.
• The Rapid mix and Chemical Doser needs to be drawn in the entrance tank.

Rapid mix components

The rapid mix design algorithm has been updated in the past year and consists of macroscale mixing followed by microscale mixing. The macroscale mixing could be a simple inline static mixer. The alum must be injected (through a submerged injector) immediately upstream from the inline static mixer. The microscale mixer is a submerged orifice at the bottom of the dividing wall between the entrance tank and the flocculator. This orifice is designed to have approximately 50 cm of head loss since it is this head loss that will also be used to measure the plant flow rate and drive the chemical dose controller. A PowerPoint presentation on the rapid mix process is available from the CEE 4540 syllabus.

This task should begin with a manual drawing showing how the rapid mix unit, entrance tank, flocculator, and chemical dose controller would fit together. After that drawing is reviewed by Monroe and by Agua Para el Pueblo staff it the MathCAD to AutoCAD (MtA) code can be written.

Chemical storage tanks

• These tanks need to be drawn. These may be an item that the onsite civil engineer will relocate to fit site conditions, but the design tool should show them at the correct elevation and in a reasonable location.

Floc Hopper Drain Valves

• The floc hopper can be put on hold for this semester because we haven't been able to create a floc blanket in a full scale AguaClara plant. This task can wait until we develop a method to create a floc blanket.

Horizontal Flocculator

Continue coding the flocculator to include the option for horizontal flocculation for large plants and determine the flow rate for the transition from vertical to horizontal flow.

• Document and describe the solution algorithm for the vertical flow flocculator
• Design a horizontal flow flocculator and develop a clear algorithm for the solution process (see Flocculator PowerPoint from CEE 4540)
• Create the equation or system of equations that will determine whether a design will have a horizontal or vertical flow flocculator. The minimum flow for a vertical flow flocculator will be related to the minimum channel width given a channel width that is about 3 x the baffle spacing and the requirement that the baffle spacing be at least 45 cm for constructability.
• Develop a method to design both horizontal and vertical flow flocculators.
• Code the necessary drawing algorithms. Make the flocculator code as generic as possible to be able to handle both vertical and horizontal flocculators.
• Design and draw the drain system for horizontal flocculators.
• Determine if the client should be able to choose the flocculator depth (as independent from the sed tank depth) or if the client should be able to choose a design for either a vertical or horizontal flow flocculator.
  • If the client chooses horizontal or vertical flow, then the ADT would design for a depth equal to the sed tank when possible, but would design shallower floc tanks for small flows if horizontal flow is selected.
  • If the client chooses the flocculator depth then the ADT should default to horizontal flocculator design whenever possible to eliminate the problem with the drains.

Vertical Flocculator

• Need to ensure that the size of the ports between channels does not exceed the size available on the floc tank wall. Also, ensure that the spacing of the baffles in the last channel does not force them into the exit channel space (this may be taken care of by switching to horizontal flow).
• The drain system for vertical flow flocculators that are large enough that the baffles are ferrocement needs special attention. Given that the Marcala plant performs better than any of the other AguaClara plants and given that the Marcala plant uses ferrocement baffles with small ports at the bottom of the lower baffles, it seems reasonable to adopt the use of ports in the baffles for draining. This will require the use of the MathCAD code for draining tanks in series to choose the port size. Monroe has a version of this code. Code and draw the flocculator drain system. This drain system should only be drawn when the flocculator baffles are rigid and the flocculator is vertical. We need a method to determine if the flocculator baffles are rigid. One possible method would be to set a criterion based on the thickness of the baffles that the client specified.

Sedimentation Inlet and Exit Tanks

• The tanks at the end of the inlet and exit channels that hold the pipes leading to the distribution tank and to waste no longer need to be as tall as they are currently drawn. Rather they can just cantilever off the side of the sedimentation tank.
• The PVC pipe component that is embedded in concrete needs to be drawn as a PVC coupling
• The removable pipes that are connected above the coupling should be long enough that they reach the same elevation as the top of the sedimentation tank walls (include freeboard).
• The waste pipe leaving the inlet tank should be drawn as a Tee that connects to the waste line from the exit tank.

Sedimentation Tank Control Pieces

• The pieces that allow the sedimentation tanks to be shut off need to be drawn (caps for the inlet channels, and exit channels). In addition, the caps should have a 1" PVC pipe that extends above the surface of the water in order to prevent air being trapped in the pipes delivering flocculated water to the sedimentation tank, and also to serve as a handle for removing the caps.
• Design and draw the caps for the effluent manifolds that are used for refilling the sedimentation tanks with clean water after the tank is cleaned. The caps for this purpose have an orifice that is sized to fill the sed tank in as short a period of time as possible without using all of the plant flow.

Plant drain system

Most of the plant waste flows enter an open channel that runs along the end of the tanks corresponding to the end with the sedimentation tank entrance channel. The following items must be designed and then drawn.

• Drain channel built of concrete
• Drain valves for all the tanks (many are already sized, but none are drawn)
• Concrete covers for the drain channel with access ports

Materials List

This list has been started and needs to be edited with input from the engineers in Honduras. Calculate the following

• Total wall area
• Total tank plan view areas

Documentation videos

Create an AutoCAD video that will show the assembly of the plant with descriptions of each part. This video could serve as the documentation that gets sent to a client who designs a plant with the AguaClara Design Tool (ADT) that explains the technology behind each piece. This video will also be used for training and teaching. Ideally the video should be made using a series of commands based on the plant dimensions so that the video can be created automatically for different plant designs.

Scale model

Create a scale model of an AguaClara plant that can be disassembled to show maintenance operations and to show the water path. This scale model should be should be small enough that it can be easily transported.

Research

Tube Floc

The development of FReTA and the data processing methods used to analyze its measurements has given AguaClara a powerful research tool. The investigation by Ian Tse into fluid shear influences on hydraulic flocculation was the first of many studies that could be performed with the tube floc/FReTA apparatus.

*Extend the experimental range evaluated by Ian Tse by increasing the length of the tube flocculator. One of the goals of this research is to measure the effect of collision potential on the residual turbidity. We have preliminary evidence that the residual turbidity continues to increase as the collision potential is increased. The challenge is to determine how long that trend continues. Increase the total flocculator length by a factor of 2 and then by a factor of 3.

• Investigate tapered flocculation designs. Hydraulic flocculators in AguaClara plants are currently designed such that the energy dissipation rates incrementally decrease over the length of the flocculator. Begin with an experimental setup that has two energy dissipation rates and determine if there is any benefit. The energy dissipation rate in the second section of the flocculator can be independently controlled by using a peristaltic pump to remove a fraction of the flow. Thus the same size tubing can be used for both sections of the flocculator.

• Investigate the influence of microscale mixing. For these tests use a well designed flocculator that produces very low residual turbidity. It is unclear what influence rapid mix parameters have on plant performance. Compare performance of systems with no rapid mix to systems that have a high energy dissipation rate (of at least 1 W/kg). Measure the effects of changing the energy dissipation rate (perhaps 0.1 W/kg to 10 W/kg) and the residence time (1 s with a single orifice mixer to 100 s with a long small diameter coil) in the rapid mix unit.

• Measure the potential impact of poor macroscale mixing by adding approximately 10% of the turbidity AFTER the rapid mix process.

• measure the effects of the influent synthetic water compositions (particle type, particle concentration, introduction of organic acids, pH, alkalinity

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• , etc.). For example, performing experiments with different initial turbidities can provide insight into how particle concentration affects floc strength and turbidity removal efficiencies. Likewise, varying the pH of the influent may help elucidate changes in floc strength as a function of pH. It is possible that floc strength (as measured by floc size) is well correlated with optimal alum dose

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• and pH.

• A laboratory scale hydraulic flocculator that operates under turbulent conditions that are relatively homogeneous and easy to characterize could go a long way into understanding turbulent flocculation. Comparison of residual turbidity and floc sedimentation velocity from turbulent and laminar flow flocculators could be used to validate flocculation

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• models. Design a turbulent tube flow flocculator by using a larger diameter tube. Determine the required flow rates and assess the capabilities of the temperature controlled water source and the peristaltic pumps to deliver the required flows. Design an upgrade to the experimental apparatus to deliver the higher flow rate if needed.

Plate Settler Spacing

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Current Subteam Leader: Rachel Philipson

Number of team members needed: 3-4

Important team member skills:

• CEE 3310 or equivalent Fluid Dynamics Background
• Self-motivated
• Curious student
• Eager to learn
• course

Challenges

• Run experiments to test characterize the conditions that cause floc roll-up

• Continue investigating the velocity gradient by varying the floc density and plate settler spacing

• Develop a way to Improve the Theoretical Analysis of the Velocity Gradient by including the Reynolds Number dependence on velocity and then solving fo the theoretically model and calculate the particle size that will roll up the tube settler
• Investigating the same effect of influent parameters such as natural organic matter, pH, and alkalinity on floc performance and plate settler performance
• Velocity gradient studies on an influent turbidity with natural organic matter

• The effects of biological flocs

• Continue to investigate the filter foam

Chemical Dose Controller

Challenges for Fall 2009

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Non-Linear Chemical Dose Controller

• Determine whether a single or multiple orifices should be used to connect rapid mix chamber and flocculation Write the algorithms for the microscale mixing orifice that connects the rapid mix chamber to the flocculator for optimum energy dissipation, head loss, and float sizing. See the Rapid Mix for equations to size the orifice.
  • We have tentative results in the mathCAD file, however, we did not have enough time to optimize the functions created.

• Construct non-linear CDC and run experiments to evaluate design and ensure experimental results align with theoretical results.
  Evaluate the optimal

For additional challenges, see the suggested challenges our team did not address this semester.

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