The Gold Standard: Settling, Filtration/Flocculation, Chemical Sterilisation (chlorine-based) and Boiling.

Water filtration can be achieved with Xylem water filters, sustainably and without expensive equipment. MIT engineers have made filters from tree branches to purify drinking water. Prototypes tested in India show promise as a low-cost, natural filtration option. My own experiments with pine and gingko have been very successful, and this is the method I teach, coupled with boiling.

There are 3 options for removing suspended impurities:

1. Gravity settling.
2. Filtration screens
3. Flocculants

Settling, Filtration & Flocculants

If you have the luxury of a clear-running stream, then the process of settling suspended particles isn’t necessary; to make it drinkable, treat it with iodine or chlorine, then boil it.

If the water is turbid (cloudy, milky, or opaque), it will require settling, which can be achieved naturally by gravity or with flocculants.

Filtration

Rudimentary filters can be made from cloth, Sand, gravel, and charcoal to reduce particles, odour, and taste, but filters do not remove pathogens. Filtered water can then be boiled.

The Millbank Millbag is a cloth bag; it is a primitive mechanical system that removes larger contaminants, but it won’t remove microscopic suspended particles, viruses, cysts, bacteria, or amoebae.

There are a couple of easy solutions for flocculation.

The Puribag: A professional disaster-relief water purification system that can be air-dropped to people trapped by floodwaters, providing a low-cost emergency water purification method.

The Puribag system is designed to purify water with high levels of suspended particles that would otherwise clog most professional filter systems within minutes, rendering them useless. I use the Puribag because it is fast, and the P&G chemical flocculant also contains chlorine to ensure the water is free from other contaminants. Puribag is an alternative to moving vast amounts of bottled water into flood disaster zones.

The Puribag uses the P&G Flocculant sachets, which contain:

Ferric sulfate (or ferrous sulfate): An iron salt that acts as a coagulant and flocculant. It neutralises the electrical charges of suspended dirt, silt, and microorganisms, causing them to clump together into heavy flocs that sink to the bottom. Calcium hypochlorite: A chlorine-based disinfectant that is released on a timed schedule to inactivate remaining bacteria, viruses, and parasites. Buffers, clay, and polymers: Additional inert and functional ingredients that help adjust pH, assist with coagulation, and aid in forming solid waste clumps.

For Water Purification on a larger scale, Aquatabs come in camping-size and 1kg buckets.

Did You Know Flocculants Have Been Used in Antiquity To Purify Water?

Alum, or Phitkari, is a miracle stone, sometimes known as a shaver or deodorant stone. This mildly antiseptic, vasoconstrictive, astringent mineral has been used in medicine since the earliest Egyptian dynasties. Trace amounts of aluminium have been detected in ancient Egyptian mummy bones. Archaeologists suggest this is a result of the Egyptians using potassium alum to purify their drinking water and reduce cloudiness—a historical water treatment technique that left residual traces in their remains:

“Mohamed Kasem of Cairo University said the researchers detected lead, aluminium, and other elements in the bones that they think reflect the toxicity of the ancient Egyptian environment. The aluminium is thought to have come from the potassium alum compound added to drinking water to reduce cloudiness,” archaeology.org/

The Romans (and earlier Egyptians) used alum (aluminium sulfate) as a natural coagulant to purify drinking water. It acted as a flocculant, causing suspended mud and microscopic particles to clump together into larger, heavy masses (“floc”) that sank to the bottom, allowing for clearer water at the top

Alum clarifies water through a chemical process called coagulation and flocculation:

1. Neutralisation: Alum is introduced into the muddy or turbid water.
2. Clumping: The alum neutralises the electrical charges of microscopic, suspended silt and organic particles that make the water cloudy.
3. Settling: These neutralised particles aggregate into larger, heavier clumps (flocs).
4. Separation: Over a few hours, these heavy clumps sink to the bottom of the container, leaving the clear water above ready to be drawn off.

You can buy Alum (powder) or Phitkari (lumps) in most Asian supermarkets, and do this experiment at home:

Flocculation is a process used by water companies in the UK to treat the water we get from the taps.

Ground Moringa seed is a flocculant.

Xylem Water Filtration: Free micro-screen capillary water filter using plant fibre filters. You can DIY a Xylem microscreen water filter.

You can make a plant-based biodegradable water filter using plant Xylem. The Xylem Water Filter can remove “99.9% of bacteria and viruses” from synthetic test waters. In field tests, the filters removed coliform bacteria from contaminated spring, tap, and ground waters.

The plant-based water filter was so important that engineers at MIT tested the idea with great success. The image below shows the simplicity of the invention. This could save millions of lives

In the video below, the author demonstrates alum flocculation in water containing a fine-particle suspension (turbid). After flocculation, the water was poured through a pine xylem screen.

Commercially bought filters need special care. The alternative is to understand the science behind capillary filtration and then imitate it with plants. I have made my own xylem water filters in my backyard lab, as seen in the video. The 2 best branches were Pine and Ginkgo.

REMEMBER: Boiling is the GOLD STANDARD for Safe Drinking Water

Caution: Floodwater is Toxic. It should only be processed with the Puribag in extreme circumstances.

Caution

Boiling does not remove:

• PFAS, including persistent compounds such as PFOA and PFOS
• Lead and other heavy metals
• Nitrate and nitrite
• Arsenic
• Industrial solvents
• Most pesticides
• Excess minerals and salts
• Oil and detergents

Boiling unfiltered dirty water in an emergency is not advisable:

• If the water is contaminated with microbes, boiling makes it safer.
• If the water contains chemical pollutants, boiling may do nothing, or even make the problem worse by concentrating them.
• If the water comes from a visibly dirty source, boiling does not remove sediment, dirt, or chemical residues.

A few practical tips can make boiling more effective:

• Use a clean pot or kettle
• Bring the water to a full, rolling boil, not just a few bubbles
• Let it cool naturally before transferring it to a clean container
• Store boiled water separately from untreated water to avoid recontamination or cross-contamination.

Single-walled metal water bottles are ideal for small-scale boiling water over a small fire. A Trangia pot holder is perfect for handling them.

Labelling Your Containers

Cross-contamination, poor labelling, and poor organisation could be fatal.

Clearly label containers with understandable labels. For example:

• Raw, unfiltered, contaminated water only NOT FOR CONSUMPTION ->
• -> Filtered, contaminated only NOT FOR CONSUMPTION ->
• -> Flocculant container NOT FOR CONSUMPTION -> Suitable for washing -> Recycle into garden through grey water system.
• -> Chemically treated, ready for boiling NOT FOR CONSUMPTION ->
• -> Charcoal treated to reduce chlorine, ready for boiling NOT FOR CONSUMPTION ->
• -> Boiled DRINKING WATER ONLY -> Safe to consume

If you are processing water at community level, the processing area should only be accessible to trained water handling staff.

Recontamination is easy to overlook. You can boil water perfectly, only to contaminate it again with a dirty ladle, a poorly cleaned bottle, or an unwashed storage container. Purified water is only as good as the container it ends up in.

This means that purifying floodwater, which some preppers think can be filtered, is actually dangerous too. The Use of floodwater for drinking with the Puribag is only for emergencies when nothing else is available. The Puribag is the only system suitable for floodwater, but it does not guarantee the removal of toxic chemicals.

Just like any other water, rainwater needs to be made safe for drinking, but beware: it contains PFAS, or “forever chemicals.” I use food-grade MDPE 220-litre resealable barrels that once contained olives. These barrels are opaque, and so Algae doesn’t grow in them. 2,200 litres have a footprint of 2.5 sqm.

Water purification is a knowledge-based skill; you are responsible for ensuring the water you produce is free from pathogens and safe to drink. Source: Solidarity Prepping

Additional Resources

Solidarity Prepping: Water in the Ecological Crisis