Preliminary Detailed Design
Team Vision for Preliminary Detailed Design Phase
- We planned to develop two prototypes simultaneously. One with automatic pumping capability and one that is manually operated. We planned to have a parts list for a proof-of-concept device and test sub-systems of the device, like purification, pumping, and power management.
- Since our last review, we have ordered nearly all the parts needed for the manual-operated filtration device. The CAD models reflect the current progress and we have performed testing on 3D printing the housing as well as UV purification.
Simplistic View of Physical Contaminant Removal from Water With Different Membranes (Pore Size Decreases From Top to Bottom)
The opportunity for this project comes in the nonexistence of a lower cost portable water purification system that not only produces water that is safe for human consumption, but a system that also produces water that is absent of odors and tastes commonly associated with organic contaminants (i.e. Hydrogen Sulfide). By the inclusion of UV purification to handle micro-organisms; we aim to lower system cost by being able to choose a filter with smaller pore size such as a micro-filter. A micro-filter will still be able to remove many dissolved solids, which contribute to turbidity, and if a carbon block micro-filter is used then absorptive filtering can also take place.
According to the World Water Assessment Programme’s national water development report for Kenya, some of the common contaminants in Kenya’s surface water are:
- Organic residues from municipal sewage
- Toxic wastes from heavy metals and pesticide discharges
- Fertilizers from agricultural activities
- Detergents from domestic use
- Microorganisms from municipal sewage
- Inert suspensions from soil sediments and mine waste
Based on our filter selections...
- Our Carbon and Sediment Filters should be able to handle the organic residues, fertilizers, detergents, and some of the inert suspensions from soil sediments and mine waste.
- Our UV bulb will handle the microorganisms present in the water
- Heavy metals are not accounted for, but the modular design of our system could easily accommodate the inclusion of a resin cartridge, or a carbon filter that is capable of lead removal could be included.
- It is our goal by the end of MSDII to test the effectiveness of our system in handling some of the contaminants noted above.
UV Bulb and Quartz Sleeve Selection
UV Batch Treatment
Originally we were planning on treating the water with UV continuously as water flowed through the system. After discussing this concept with Sarah Brownell it was decided that it may be infeasible to go through the testing and validation to complete this process in the MSD timeline, therefore a more conservative approach will be executed using the design chosen above. We will implement batch treatment.
In UV Batch Treatment a floating switch will trigger the batch treatment process to begin once the UV compartment is full of water. The pumps will shut down; the inlet valve will close; UV bulb will be turned on and will treat the water to about 40mJ/cm^2 (NSF/ANSI 55); the outlet valve will open; head pressure will be applied by pumps or a third valve that allows access to atmosphere; outlet valve will close and inlet valve will open and the system will start to filter water again and fill the UV compartment. With this process we are better able to assert control over the UV exposure of the water.
UV Dosage Vs. Class A and B (40 and 60, respectively) Standards NSF/ANSI 55 at Different Tube Radii)
From this model the flowrate coming from the filters was approximated to be 1gpm, as you can see batch treatment (according to this model) does not dramatically hinder the flowrate through the system. Also, according to this model, flowrate will not be hindered by or optimized by the diameter of the UV housing (calculated as the volume released divided by the time required to: fill the UV compartment with 1gpm from the filters; treat the water to the standard dosage; then allow the water to drain from the compartment), because both volume and time to completion of a cycle are equivalently proportional to the diameter of the compartment.
A document explaining these calculations will be posted (for now the MATLAB code can be found in the directory of our EDGE folder archive). The model will likely change, however, as it contains many assumptions that limit its accuracy. This model is based on the inverse square law, but a more appealing model is the LSI multiple point source summation model, which takes into consideration the geometries and photon propagation from a cylindrical tube.
Bill of Material (BOM)
The following is the Bill of material thus far. The bill is a combination of the parts needed for the housing (seen in the cad drawing below) and the components that are purchased (link to the spreadsheet).
Test PlansFor Preliminary Test Plans Click: Here
Tests are in their early stages of development, since most of this preliminary design period was spent performing feasibility analyses. Test plans will be drastically extended upon further by next review.
NSF Protocol P248
Design and Flowcharts
Risk AssessmentFor Updated Risk Assessments Click: Here (Changes are Highlighted in Yellow)
Design Review MaterialsDesign Review Presentation
Plans for next phaseFuture Work
- Evaluate Purchased Parts
- Finish Modeling for 3D Printed Components
- Print Preliminary Parts
- Assemble Subsystems
- Perform Process Evaluations
- Construct Preliminary Proof of Concept
- Finalize Flow and Physical Analysis