1. C LEAN W ATER 4 A LL Revolutionizing the way you view dirt.

2. DIATOMACEOUS FILTER Our goal is to create a filter that… ….produces clean water fast. …removes dangerous parasites and bacteria. …lasts a long time. …costs next to nothing. http:// www.firstbaptistclinton.org/clientimages/33351/child-with-dirty-water.jpg

3. SINTERED FILTER DESIGN Good Water Bad Water (Pressurized) Pressurized Sintered System D.E. Maybe? http://www.faireyceram ics.com/images/produ cts/filter_candles2.gif

4. Testing Pathway Slurry-based Resistance to resuspension Optimal thickness Sintered solid Geometric shapes Abrasion testing Mechanical testing Flow rate Bacterial Filtration Ability Production Cost Fouling Rate D EVELOPING O PTIMAL F ILTER D ESIGN We are here

5. Clean Water 4 All Timeline Wk 5Wk 6Wk 7Wk 8Wk 9Wk 10Wk 11Wk 12Wk 13 3/12- 3/19 3/19- 3/26 3/26- 4/2 4/2- 4/9 4/9- 4/16 4/16- 4/23 4/23- 4/30 4/30- 5/7 5/7- 5/14 Pre-Design A1 - Establish Pure Slurry Baseline make thick filter cake and test A1 A2 - Sintering Process produce solid (bound) filter cakes determine optimal temperature A2 Product Design B1 - Flow modeling (Solid Works) B1 B2 - Mechanical Testing (3-Point Bending) B2 B3 - Filter Quality Testing microspheres as substitute filter bacteria B3 B4 - Abrasion Testing B4 B5 - Fouling Testing B5 Product Finalization C1 - Optimize to find final prototype C1 C2 - Determine materials & production costs C2 C3 - Make final presentation C3

6. N EW D ECISIONS / T RADEOFFS Added new step to filter production: sanding Filter thickness ~0.6cm Thin enough to fit in pipe vs. increased filtration, fouling lifetime Mechanical strength Sintering filter cakes for longer time to increase mechanical strength vs. overdensification (decrease filtering ability), time + energy used in process

7. D ARCY ’ S L AW Flow through a porous media is governed by: Q (volume/time) = Total Discharge k (area) = Intrinsic Permeability of Media A (area) = Cross Sectional Area P b – P a (Pressure) = Pressure Drop u (Pressure second) = Dynamic Viscosity L (Length) = Length the Pressure Drop is Taken Over

8. Why do we care? Intrinsic permeability, k, gives us a way to quantitatively compare the flow characteristics of different samples. 500°C for 1 hr 700°C for 2 hr 2 D 1 3 Driven by Surface Energy and Capillary Pressure Material Moves by Boundary diffusion (1) Lattice diffusion (3) Surface diffusion and vapor transport (2) Densification occurs when material moves from between centers, reducing D. Sintering Sinterting

9. INITIAL PERMABILITY TESTS We’ve done some initial tests with our prototype (600°C for 30 min) and found: Q = 2.1[cm 3 /s] A = ~1 cm 2 Pb – Pa = Pressure Drop [cN/cm 2 ] μ = 1 x 10 -7 [cN/(cm 2 s)] L = 0.6 cm Then we calculated: k (area) = 9.01 x 10 -10 [cm 2 ]

10. WHAT DOES THIS MEAN? K Sintered, DE = 9.01 x 10 -16 [m 2 ] From C Hall and W D Hoff: Transport in brick, stone, and concrete, 2002. From Jurcă ştefania-alina: Water Density and Soils Intrinsic Permeability Dependent on Temperature.

11. QUALITY FILTERING TESTS Beer’s Law constant = 2 x 10 9 ; can now back- calculate concentration Instrument range of detection known: maximum concentration ~ 10 8 beads/ ml

12. THREE POINT BENDING TEST To calculate the Flexural Modulus (E f ): http://www.zwick.co.uk/images/biege3lv.jpg where m is the initial straight line slope of the load- deflection curve.

13. P OTENTIAL S TUMBLING B LOCKS Sintering Technology/Ability Inconsistent structure leading to poor filtering and reproducibility Poor durability Cost If DE was the solution, why hasn’t it been done? Balancing Flow Rate and Filtering Ability May find we can filter effectively or filter fast, but not both Inability to filter solutes Filter only effective against biological threats Feared Scenarios: Slurry too slow and sintered too expensive Inability to produce consistent well-sintered filters Produce filters that work almost as well as existing tech at 5x the cost

14. P ROTOTYPE Pressure Tester: PVC pipe unit Pressurized with Argon Easy sample removal Problems: Does not seal Sample breaks Too small z-direction: filters too thick

15. M ECHANICS Written on page in foundry I forgot and left.

16. I NITIAL R ESULTS Chronology of Prototype use pos-construction: Many samples show cracking from drying step Samples too small for pressure-side 0-ring Step down fitting was made Samples too thick, began sanding to thin them Sanding down samples resulted in cracking >50% of the time Leaking from every possible junction when loaded Tightening resulted in sample failure

17. S OLUTION : S ILICONE Liberal application of silicone: Allowed thicker sample Sealed sample/gasket and gasket/PVC interface Sealed leaking threads Temporary solution only Prevents re-use of PVC junction Increases material cost and testing time Enabled 1 sample run:

18. T EST R UN Un-pressurized Observed no leaking from joints Gravity flow-rate exceeded prior tests Due to filter thickness? Cracking? Water column? Pressurization to 20 psi No leaking Slight increase in flow rate observed Pressurization to 30 psi Catastrophic failure of sample

21. M OVING F ORWARD Optimal cake thickness ~0.6cm Sintering for several hours instead of 30mins, try different temperatures Maximum pressure = 30pSi? Find exact pressure at which filter ruptures Stay with silicone as sealant

22. Q UESTIONS ?