Water Scarcity is a major world problem. It affects a huge area, including every world continent. 2.8 billion people one month a year have problems with water scarcity, and more than 1.2 billion people lack access to clean drinking water. Water Scarcity has many causes. One is climate change, global warming has resulted in weather change, moving rain and floods. Another cause is overuse of water: animals, factories, and people are overusing water, not leaving enough for the rest of the world. Water is often polluted, far away, controlled by the government or nonexistent due to a drought. This problem results in a lack of clean drinking water, poverty, disease, lack of education (kids are too sick or busy getting water to go to school). The problem also results in sanitation issues.
The Theoretical Solution
You probably have seen biofilters on Instructables. Simple, survival water filters using increasingly small layers of material and a bed of activated carbon to filter out material. Activated carbon works through its chemical properties and surface area. 1 pound of activated carbon has about 100 acres of surface area. This surface area catches materials and impurities, taking them from the water. Active carbon filters are most effective at removing chlorine, sediment, volatile organic compounds (VOCs), taste and odor from water. They are not effective at removing minerals, salts, and dissolved inorganic compounds. In a rural village, they will need a higher level of filtration to remove viruses and other tiny deadly organisms from the water.
So, the theoretical part. For a higher level of filtration, one would use microfiltration or ultrafiltration method. These require pressure to push water through the membrane. Microfiltration removes everything up to viruses, ultrafiltration removes these viruses so it would be favorable. These membranes require pressure to push the water through. People have made electric water pumps that gain energy from the peddling of a bike, but these are complicated, expensive, hard to repair in a rural village and generally complicated. I have made a plan for a purely mechanical pump that uses the peddling of a bike to spin a centrifugal pump that pushes water through a large surface area micro, or potentially ultrafilter. Now, let's go into how to build the simple biofilter that would serve as the first level of filtration before going through the bicycle pump.
Step 1: Simple Bio Filter Materials
The first step of this project is to build the biofilter. This is a simple but effective water filter suitable for filtration in developing countries to a water cleaner in the apocalypse. It is very easy to make, only requiring a few simple supplies.
1. Large(ish) water/soda bottle (I used an extra large plastic water bottle, some other options could be 2-liter soda bottle or a small water bottle. Make sure it has a cap)
2. Gravel or pebbles
4. Activated Carbon (I found mine at a fish store, it came in a carton used to clean tank water. Another option could be activated charcoal, but that results in hazy looking water that needs to be boiled.)
5. Cloth1. Large(ish) water/soda bottle (I used a extra large plastic water bottle, some other options could be 2 liter soda bottle or a small water bottle. Make sure it has a cap)
2. Gravel or pebbles 3. Sand 4. Activated Carbon (I found mine at a fish store, it came in a carton used to clean tank water. Another option could be activated charcoal, but that results in hazy looking water that needs to be boiled.) 5. Cloth1. Large(ish) water/soda bottle (I used a extra large plastic water bottle, some other options could be 2 liter soda bottle or a small water bottle. Make sure it has a cap)
2. Gravel or pebbles 3. Sand 4. Activated Carbon (I found mine at a fish store, it came in a carton used to clean tank water. Another option could be activated charcoal, but that results in hazy looking water that needs to be boiled.) 5. Cloth
Step 2: Preparing the Bottle
Making the water bottle into a fill ready filter is easy. First, I cut the bottom off to make an area for water to be poured in. I then drilled three holes in the cap and screwed it back on. Last, I cut a circle of fabric and pushed it into the bottom to hold back the activated carbon.
Step 3: Filling the Filter
First, I poured the entire carton of carbon into the filter. On top of that, I poured the sand. Last, I took the pebbles that I had scrubbed clean and washed of any traces of soap, and pouring those on top of the sand, creating three fairly equal sized layers. I didn't want the filter materials falling out the top, so I wrapped it with plastic wrap and a few rubber bands.
Step 4: Using the Biofilter
The biofilter is simple to use, just pour the dirty water into the top and watch it drip out the bottom in a crystal clear stream. One important maintenance piece is backwashing. Over time and use a filter will build up with the waste it filters out. To clear this out I held closed the bottom, filled the filter with clean water and let it overflow over the top for about five minutes until it seemed clear
Step 5: The Theoretical Bicycle Filter
This activated carbon bottle serves as a decent filter and would be easy to put together in a village with very unclean water. But, it does have setbacks. Activated carbon-only doesn't filter out viruses.
The ultimate goal of this project would be a 3d printable kit that includes an easy to assemble centrifugal pump with a spinning bowl that will be spun by a tire. The kit would include a few removable microfilters and a stand for the bike.
In order to give the centrifugal pump enough water pressure to pump through, the water from the biofilter would not go directly into the pump. Instead, it would gather in a reservoir, then be emptied into the pump. This is where it gets theoretical.
The biggest problem to deal with is the required pressure to get water through a micro/ultrafilter. A microfilter takes 5-45 psi, a ultrafilter 7-150 psi. Going into the pump water will have 14-20 psi from gravity.
An average bike tire spins 840 rpm, and so will the centrifugal pump. 2 3/4 to 1 1/4 inch PVC pipes would lead into and leave the pump (see diagram). They would be made of schedule 40 PVC pipe.
The spinning part itself would need to be put tightly into the pump, so most of the water going in gets moved. if the size of the pump was done right, the pump could potentially reach 40-80 psi of water leaving the pump, enough to do both filtration methods.
In order to maximize surface area, the filter itself would not be flat. It would be deep and round, the water goes in a comes out the sides, then flows into a container. This deep membrane would need less psi than a smaller one.
If anyone has any ideas about this pump or its construction, leave an idea in the comments.