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

M OTIVATIONS FOR P ROJECT More than 1 billion people lack access to safe water for drinking, personal hygiene, domestic use 3.6 million people die each year of water-related diseases; 98% of deaths occur in developing world Diatomaceous earth filters are low cost, locally producible solution

T ARGET P OPULATION AND F ILTER U SAGE Majority of those without proper sanitation live in Southern Asia and Sub-Saharan Africa Over 2/3 live on less than $2/day Target 3 liters daily per person for household filters serving 5-7 people UNICEF / WHO Progress on Drinking Water and Sanitation Report, 2008

G OALS Development and production of a filter that balances Performance Filtered water meets WHO standards for clean drinking water Can filter liters/ day in reasonable time Lifetime Lasts long enough that total cost is less than 25 cents/ day (1/8 of estimated daily income) Durability Withstand strains of daily usage and child tampering Can be cleaned with abrasive without breaking Cost Inexpensive raw material Cheap to produce/ assemble locally

D IATOMS Common name for over 200 genera of often unicellular organisms encased within cell walls made of silica Own the ability to create exact replicas of themselves with micro or nano-scale definition. Often diatomaceous earth, the fossilized remains of diatoms, is mined for many uses. University of Washington: Emily Marshall

D IATOMACEOUS E ARTH Soft, chalk-like sedimentary rock, which is often ground into an off-white powder (if no other minerals are present). The powder is abrasive and porous. Common uses: - Organic pesticide - Pool filters - De-wormer of livestock - Thermal Insulator

D IATOMACEOUS E ARTH F ILTERS Used for filtration of: - Pool water - Drinking Water - Beer and wine - Syrups and Sugar Size of the pores range from.5 to 2 microns.

D IATOMACEOUS E ARTH F ILTERS Bacteria can range in diameter from 0.2 to 2 microns. But, diatomaceous earth is still effective at filtering even small pathogens.

E XISTING F ILTER T ECHNOLOGY Filter Candles -The ceramic of a filter candle is cast in such a way that it has one domed closed end. The other end of the ceramic is open. This open end is closed off with a food grade plastic mount, which enables the candle to fit into a filter housing. Water passes from the outside of the candle to the inside, leaving particles of dirt, bacteria, etc. on the outside of the ceramic. The filtered water then passes out of the candle through the mount. - Cost: $30-50

D ARCY ’ S L AW Flow through a porous media is governed by: Q (volume/time) = Total Discharge k (area) = 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 Only valid for slow viscous flow

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

S PECIFIC T ESTING D ETAILS Both Filters Flow Rate Gravity driven Pressurized Filtering Ability Check filtering of microorganisms Fouling Rate Liters filtered before clogging Improve to minimize cost Sintered Filter Abrasion Test Ability to withstand cleanings Yield Strength Must be robust Elastic Modulus

S INTERING A T A G LANCE 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.

S INTERING C ONCERNS Densification is the enemy We want to maximize surface and vapor transport and minimize boundary and lattice diffusion SiO 2 has high Tm! Sintering can occur far below Tm and our “sharp” material should have a large driving force to sinter Reactivity? Luckily SiO 2 is already oxidized so air is OK Plan: Short, low temperature sinter in air

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

P ROJECT G OAL T IMELINE

THANK YOU! QUESTIONS?