Large Particle Filtration Methods

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Large Particle Filtration Methods

1. Pre-coat Filters:

Use:

Filtration media is pre-coated with diatomaceous earth (non-toxic safe substance made from crushed fossils of freshwater organisms and marine life- acts as glass shards that puncture harmful insects and particles) to remove very small particulate and some bacteria.

Pros:

Uses natural methods, not harmful to humans

Cons:

Only practical for limited volume use

Would be expensive ($7 for 6oz)

2. Screen Filters:

Use:

Coarse screen to filter out large particles at the intake point. Commonly used to filter out physical matter such as fine sand and large inorganic debris. Typically made from metal, plastic or synthetic cloth

Pros:

Simple and economical

Made from materials possibly available in area

Can be used for large scale operation

Cons:

Will clog is algae is present

3. Bag Filters:

Use:

Constructed of non-woven media such as polypropylene in the shape of a bag.

Water is placed in the bag and filters through (using gravity or pressure) Once bag is clogged it can be discarded.

Pros:

Very Portable

If tweaked design possibly re-usable

Each person could have his own

Possibly “Bag Concept” can be used in design

Cons:

Polypropylene is not prevalent in Africa

If used as described wasteful

Need to search for new material that would work as well

4. Plate and Frame Filters:

Use:

Thick woven materials such as cotton or polypropylene mounted on a frame. Rows of the filters are lined up and fluid pushes through them.

Pros:

Uses materials that are abundant in Africa

Can be easily broken into components for protability

Cons:

May have many parts difficult to assemble

May need pressure source to filter water??

5. Sand Filters:

Use:

Position coarse sand on top, then have layers with fine sand/clay on bottom. Run water through each material, to filter out physical matter

Pros:

Cheap

Process large volumes

Uses abundant materials

Easy to replace

Multilayer prevents clogging

Cons:

Need to allow time for materials to pack closely for better filtration

Heavy

Still need to add on two part filtration

6. Active Carbon:

Use:

Remove large particles and absorb low molecular weight organics and chlorine by running through active carbon

Pros:

May be able to use abundant charcoal?

Light

Cons:

Must be back washed frequently and changed periodically to avoid bacterial growth and efficiency

Not good for large scale use (possibly)

7. Depth Filters:

Use:

Most common particle filter and most suitable for majority of applications. Water flows through a thick wall filter, where particles are trapped. (Thick wall- cotton, cellulose, synthetic yarns, polypropylene) The best depth filters have lower density on the outside and higher density on the inside. This traps coarse particles toward the outside, fine particles on the inside, leading to a longer life.

Pros:

Could use materials that are abundant as media

Large scale applications

Removes bulk of particles

Cons:

Need to look into how to have varying screening materials in one screen

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