Water Contamination and Filtration 101, by MHN

*For those of us who prep, I am tailoring this guide to contaminants that would be found anywhere: radiation from fallout, chemical contamination from industry, contamination from urine and feces, natural sources that one might encounter on a homestead, and the technologies and techniques like filtration that would be most widely available in a SHTF scenario. I am an engineer who has specialized in water treatment in the chemical industry.

Most of us rely on clean tap or bottled water for everything from drinking to cooking to showering. We pay little attention to the process that takes raw water and transforms it into safe clean potable water. Once upon a time our ancestors drank right from streams and lakes. While the quality of this water was most likely better than the quality of water from most modern day surface sources, it was still contaminated with various pathogens and minerals. Even though our ancestors’ digestive tracks were heartier than ours, waterborne illnesses ranging from minor stomach bugs to cholera and dysentery took their tolls.

Many of us believe that a high quality particulate filter coupled with an activated carbon filter will make any source of water safe for human consumption. However, that isn’t necessarily true. Contaminants come in many shapes and sizes. In addition, different contaminates require different technologies and processes. Geography and human development determine where contaminants are found. Consequently, suburbia is not likely to contain agricultural chemicals. PCB’s (polychlorinated biphenyls) aren’t likely to be found rural locations. BTEX compounds (benzene, toluene, ethylbenzene, and xylene), found in both gasoline and diesel, can be found anywhere.

Rain catches are excellent ways to provide contaminant-free softened water, as long as there are no airborne contaminants. (This articles does not thoroughly discuss rain catches though.)

In order to understand how to make water safe for human consumption, we have to learn what’s in it and what treatment options can deal with each kind of contaminant.

What’s in Water

Suspended Solids

Suspended solids are plankton, algae, organic debris, soil, sewage, or other particulate matter found in water that do not dissolve. So you can usually see them with the naked eye in many cases. While not always an issue by themselves, pathogens are usually carried on solids. This is why removal of suspended solids is typically the first step in any water filtration. Fortunately, for you, it is the simplest step.

Dissolved solids

Minerals and organics compounds disolved in water are called dissolved solids. Dissolved solids are salts or organic compounds that dissociate in water and form ions. Minerals containing calcium, magnesium, iron, and manganese give water its hardness and make water taste poor. Additionally, dissolved solids from limestone deposits or iron-rich soils are from natural sources and are not harmful. In fact, dissolved minerals found in water are part of a balanced diet. These minerals provide a good source of trace minerals like sodium, potassium, and calcium. Other dissolved solids, like lead, mercury, barium, arsenic, and chromium, may be natural from man-made sources and have acute and chronic toxicities, depending on the dosages.

Harmful Inorganics

While any contaminant may be harmful in high enough doses, for the sake of this essay I shall classify “harmful inorganics” as any inorganic material that may cause acute or chronic toxicity at exposures typically encountered in water supplies. Several harmful inorganic chemicals listed above– lead, mercury, barium, arsenic, and chromium– have both natural and human sources. Some harmful inorganic chemicals, like nitrates and nitrites, usually come from fertilizer runoff. Others, like mercury and antimony, come from industrial waste.

Organic Chemicals

Nearly all harmful organic chemicals in drinking water come from human activities. The “biggies” are BTEX (benzene, toluene, ethylbenzene, and xylene), vinyl chloride, PCB’s, and dioxins. A laundry list of other minor organic chemicals, including glyphosates (common herbicide), organochlorides (common class of pesticide), and pharmaceuticals, can also be found in drinking water supplies. Many people falsely believe their water is free of all organic contaminants because of where they live. However, one gallon of gasoline has the potential to contaminate hundreds of thousands of gallons of water.

Radiological Contaminants

Radiological contaminants, like most contaminants, can be natural or man-made. Radon, the most prevalent radiological contaminant in water, is naturally occurring. well water contains the Radon almost exclusively. Other sources of radiological contamination could be fallout from nuclear weapons or accidental releases from commercial nuclear power plants. Fortunately, hydrogen and oxygen are very stable and don’t easily undergo neutron activation (the process by which stable atomic nuclei are turned radioactive). So, removing radioactive contaminants from water will render the water safe for human consumption.

Pathogens and Microorganism

Simply put, harmful pathogens and microorganism are any live biological agents that can reproduce in a human body. They range from organisms that may cause minor stomach irritations to deadly pathogens with high mortality without modern medical intervention. Think of pathogens like cholera, hepatitis, coronovirus, cryptosporidiosis, dysentery, polio, et cetera.

Removing Contaminants

Now that we know what kinds of harmful contaminants are in water, we need to learn what techniques and technologies we can use to effectively remove them. One single technique will rarely work on all contaminants. You must use a combination of methods to make water potable. Especially when contaminated from many sources. While dozens of techniques exist to deal with water contamination, I will focus on those technologies that are most widely available and least expensive.

Slow Sand filtration

Slow sand filtration uses a container,  lined with drain tile and a thick layer of sand. Additionally, four feet or more of sand is placed on top of the drain tile. Within a few weeks of use, a biological film will form just below the surface of the sand, removing pathogens and microorganisms. As a result, a separate settling tank is recommended for use in highly turbid (cloudy) water. The settling tank must be upstream of the filter.

  • Will Remove: suspended solids, most protozoa, and bacteria
  • Won’t Remove: viruses, dissolved solids, organic chemicals, soluble radiological contaminants
  • Pros: inexpensive, simple to build, uses common materials, relatively high filtration rates, operates via gravity, low power consumption, low maintenance, no consumables required
  • Cons: backwashing can disturb the biological film. This requires time for regeneration. You cannot use the process  immediately after construction. Sand filtration fouls quickly in highly turbid water

Ion exchange

Ion exchange units are commonly seen in households as water softeners. These filtration units  remove positively charged ions.

  • Will Remove: calcium and magnesium ions with NaCl or KCl softeners. Additionally, sodium resin units can remove nitrates, nitrites, and radium (the source of radon gas).
  • Won’t Remove: viruses, protozoa, and bacteria, organic chemicals, inorganic chemicals, most dissolved solids, or suspended solids.
  • Pros: inexpensive, easy to install
  • Cons: uses a consumable, limited in what they will remove, it also requires pressurized water.


Air is introduced into the water through a process called Aeration. Similarly, the water fountains in ponds or air bubblers in fish tanks are aeration systems.

  • Will Remove: iron and manganese, by oxidizing them into insoluble particles, hydrogen sulfide. Good for reducing filtration loading on downstream filtration processes.
  • Won’t Remove: viruses, protozoa, and bacteria, organic chemicals, inorganic chemicals, most dissolved solids with the exception of iron and manganese, suspended solids
  • Pros: Simple, inexpensive
  • Cons: Requires power (usually), does not remove many contaminants.

Reverse Osmosis

Reverse osmosis utilizes a semi-permeable membrane to remove certain contaminants from water.

  • Will Remove: viruses, protozoa, and bacteria, dissolved solids, reduces most harmful inorganic chemicals (arsenic, lead, radium, and nitrates, depending on membrane specification).
  • Won’t Remove: most organic chemicals.
  • Pros: highly effective at removing pathogens and dissolved solids, inorganic chemicals, affordable.It is also widely available.
  • Cons: removes beneficial minerals from water, membrane requires periodic replacement, it also uses a great deal of power to pressurize the water, uses anywhere from 3-10 gallons of water for each gallon of water produced. Use to remove suspended solids will quickly plug the membrane.

Solar Disinfection

Solar disinfection uses UV radiation from the sun or any high-powered ultraviolet source to destroy pathogens in water. Water is placed in a clear container that can pass UV light. You then place the container in the sun for six to eight hours. Also, manufacturer’s recommend polyethylene terephthalate (PET) bottles.

  • Will Remove: viruses, protozoa, and bacteria
  • Won’t Remove: dissolved solids, organic chemicals, inorganic chemicals, suspended solids
  • Pros: inexpensive, simple, highly effective
  • Cons: none

Activated Carbon

Activated carbon (AC) is a form of highly porous pure carbon with an extremely high surface area to mass ratio. This surface area, as well as AC’s affinity for many organic chemicals, makes it very useful for water treatment

  • Will Remove: most organic chemicals, some inorganic chemicals, organic and inorganic mercury
  • Won’t Remove: dissolved solids, most inorganic chemicals, suspended solids, nitrates, viruses, protozoa, and bacteria
  • Pros: One of the only methods to remove organic chemicals. It is also relatively inexpensive to purchase in bulk, widely available.
  • Cons: non-reusable. You cannot manufacture a unit as effective as an industrial produced AC. (Despite rumors to the contrary). There is a very narrow range of what it will remove.

Mechanical Cartridge Filters

Mechanical cartridge-style devices use a porous filtration membrane to remove particles from the water. Think reverse osmosis but with much larger pores. Furthermore, the smaller the pore, the more the filter will remove. Consequently,  Ceramic membrane filters have also become quite popular in recent years, due to their effectiveness and reusability.

  • Will Remove: suspended solids, viruses, protozoa, and bacteria (depending on the size of the filter)
  • Won’t Remove: dissolved solids, inorganic chemicals, suspended solids, nitrates, organic chemicals
  • Pros: may be reusable, inexpensive, widely available
  • Cons: requires power to operate, either hand-powered or pressurized water source. Additionally, it has a relatively low volume of water production. Finally, it requires regular cleaning


Distillation is the process of separating a mixture based on differences in evaporation points of a solution. It is operated to selectively evaporate and condense only one component of a solution, just like an alchohol “still”.

  • Will Remove: nearly everything! suspended solids, viruses, protozoa, and bacteria, dissolved solids, inorganic chemicals, suspended solids, nitrates, organic chemicals.
  • Won’t Remove: organic chemicals that boil at temperatures lower than water.  You can manage this though.
  • Pros: very effective at removing contaminates, if operated properly can remove organic chemicals whose boiling point is significantly lower than water if the first portion of the condensate is discarded.
  • Cons: removes beneficial minerals, requires a fuel/heat source, use of non-corrosive materials for construction may increase costs.

Chemical Treatment

The use of chemical disinfectants for water purification is standard for municipal water supplies. Sodium hypochlorite, iodine, and bleach are also widely available and highly effective disinfectants.

  • Will Remove: viruses, protozoa, and bacteria
  • Won’t Remove: suspended solids, dissolved solids, inorganic chemicals, suspended solids, nitrates, organic chemicals
  • Pros: Complete removal of all pathogenic agents. Furthermore, it provides a residency for disinfection, meaning water can sit without fears of immediate incidental recontamination.
  • Cons: Use of dangerous chemicals. Requirement of consumable components.

As you can see, not all water purification solutions are appropriate for all purification requirements. If you receive water from a municipal supply, check with them to verify the quality of the water you do receive. Likewise, get your well or surface water tested to confirm your treatment method is appropriate for your water source. Remember though, in a SHTF scenario, your water source’s quality can change dramatically overnight. Additionally, pollution from chemicals, human waste, and radiological contamination should incentivize you to be proactive in how you make your water safe to drink. Disaster prep is all about contingencies. Identify your risks and prepare accordingly.

SurvivalBlog Writing Contest

This has been another entry for Round 70 of the SurvivalBlog non-fiction writing contest. The nearly $11,000 worth of prizes for this round include:

First Prize:

  1. A $3000 gift certificate towards a Sol-Ark Solar Generator from Veteran owned Portable Solar LLC. The only EMP Hardened Solar Generator System available to the public.
  2. A Gunsite Academy Three Day Course Certificate that is good for any one, two, or three day course (a $1,195 value),
  3. A course certificate from onPoint Tactical for the prize winner’s choice of three-day civilian courses, excluding those restricted for military or government teams. Three day onPoint courses normally cost $795,
  4. DRD Tactical is providing a 5.56 NATO QD Billet upper with a hammer forged, chrome-lined barrel and a hard case to go with your own AR lower. It will allow any standard AR-type rifle to have a quick change barrel, which can be assembled in less than one minute without the use of any tools and a compact carry capability in a hard case or 3-day pack (an $1,100 value),
  5. An infrared sensor/imaging camouflage shelter from Snakebite Tactical in Eureka, Montana (A $350+ value),
  6. Two cases of Mountain House freeze-dried assorted entrees in #10 cans, courtesy of Ready Made Resources (a $350 value),
  7. A $250 gift certificate good for any product from Sunflower Ammo,
  8. Two cases of Meals, Ready to Eat (MREs), courtesy of CampingSurvival.com (a $180 value).

Second Prize:

  1. A Model 175 Series Solar Generator provided by Quantum Harvest LLC (a $439 value),
  2. A Glock form factor SIRT laser training pistol and a SIRT AR-15/M4 Laser Training Bolt, courtesy of Next Level Training, which have a combined retail value of $589,
  3. A gift certificate for any two or three-day class from Max Velocity Tactical (a $600 value),
  4. A transferable certificate for a two-day Ultimate Bug Out Course from Florida Firearms Training (a $400 value),
  5. A Trekker IV™ Four-Person Emergency Kit from Emergency Essentials (a $250 value),
  6. A $200 gift certificate good towards any books published by PrepperPress.com,
  7. A pre-selected assortment of military surplus gear from CJL Enterprize (a $300 value),
  8. RepackBox is providing a $300 gift certificate to their site, and
  9. American Gunsmithing Institute (AGI) is providing a $300 certificate good towards any of their DVD training courses.

Third Prize:

  1. A Royal Berkey water filter, courtesy of Directive 21 (a $275 value),
  2. A custom made Sage Grouse model utility/field knife from custom knife-maker Jon Kelly Designs, of Eureka, Montana,
  3. A large handmade clothes drying rack, a washboard, and a Homesteading for Beginners DVD, all courtesy of The Homestead Store, with a combined value of $206,
  4. Expanded sets of both washable feminine pads and liners, donated by Naturally Cozy (a $185 retail value),
  5. Two Super Survival Pack seed collections, a $150 value, courtesy of Seed for Security, LLC,
  6. Mayflower Trading is donating a $200 gift certificate for homesteading appliances,
  7. Montie Gear is donating a Y-Shot Slingshot and a $125 Montie gear Gift certificate.,
  8. Two 1,000-foot spools of full mil-spec U.S.-made 750 paracord (in-stock colors only) from www.TOUGHGRID.com (a $240 value), and

Round 70 ends on May 31st, so get busy writing and e-mail us your entry. Remember that there is a 1,500-word minimum, and that articles on practical “how to” skills for survival have an advantage in the judging.


  1. Great article. Wanted to inquire about any follow up that would provide necessary direction around how to test/what to test in a water source. When I get the list of tests from the Ag. store, it makes absolutely no sense to me. If I test “everything” then it would be a very expensive option. What indicators would help direct folks what to test for? (i.e. on a farm – test for a,b,c,z – In a city/town, test for d,e,f,z – in the north-east test for (farm/city list + g,h,k). Thank you !!

    1. If you are on a municipal water supply they test every shift for common contaminates like pathogens and do regular testing for other contaminants, you can call and request it. If you have a private well you should test every few years. Most big box home improvement stores sell water testing kits that you mail off to a lab. A good indication is your senses: does the water taste different, are your clothes and disghes not coming clean (surfactants need the right water chemistry to work properly).

  2. How bout UV from Lamp to disinfect? I use a polyester filter ( sediment) then a carbon paper pleated ( carbon block is better) followed by UV at 3 gallons a minute and run off a 12vdc supply from a rain catchment system with 60psi demand pump to pressure same. ( 120 vac is same set up)

  3. Enjoyed reading this article very much because of the clear, easy to understand format. Good reminder to those with well water to get their wells checked periodically too. Years ago, I lived on a ranch and our family well became contaminated. Thank you!

  4. Back in the 1990’s, I did some work on water quality in Georgia for the USGS. To my surprise, I found that the highest frequency of occurrence of many herbicides and pesticides in water was clearly in urban/suburban areas, not in agricultural areas. My reasoning at the time was that homeowners over-apply chemicals for their lawns and small gardens in a manner that would be cost-prohibitive for farmers. You may wish to modify your statement to the contrary.

  5. My son and I hike in a national forest here in Ohio. We wanted to try our Life Straws but there were posted warnings about not drinking the water due to dissolved metals from mining. The water looked great but you don’t know what’s in it. This got me thinking about finding a home test kit to check water quality. There are some basic kits that test for bio contaminants but it seems the only option to test for chemicals and dissolved metals is to send a sample to a lab. Do you know if there is economical way to completely test water with a kit of some type, used by the average person?

  6. Get a Gravity Feed filtration unit with the Imperial filter elements.

    see: jmccanneyscience.com/SecWebOrderPg.htm

    Spec Sheet: jmccanneyscience.com/FilterElementSpecSheet.HTM

  7. Several municipal water supplies have been caught falsifying tests and supplying contaminated water (Camp Lejeune was the first). What about the industrial waste fluoride? What is the best method to remove it?

Comments are closed.