Building a Backyard Water Treatment Plant

Clean drinking water is critical to your survival, because without potable water you will die within a few days. I don’t intend to hammer away on this point, because everyone who visits this blog generally knows how important it is to have access to clean water, and this subject has been covered many times from many different angles. Many of us have several hundred gallons of water stored away in containers, some more portable than others. Some plan to rely solely on a Berkey water filtration system to filter surface water collected from ponds or rain catchment barrels. While the Berkey filters are excellent and water storage is a must, having these will not be good enough in a prolonged grid-down scenario. Your water storage may run dry, and your Berkey filters have a limited lifetime and may not be able to handle long-term filtering.

The Lord handed us a pristine planet, and though we may have polluted much of the water we have been entrusted with, He has given us the materials and intelligence necessary to purify our water. Most of the modern world relies on municipal water treatment facilities to provide them with clean water. Water flows from faucets and toilets flush with the flip of a lever as surely as the sun rises and sets. By paying the water company every month we are guaranteed an almost unlimited supply of clean water. Most of the time the public shows no appreciation for the system that delivers the water or knowledge of the process by which it is treated and delivered, but most everyone expects to be provided with water as though it were a birthright. The public generally does not question the quality or safety of their water while the nameless, faceless technicians at the utility company work their “magic”, and we generally put our faith in them to deliver. However, some of that faith has been shown to be eroding over the last few decades as more people have been relying increasingly on water filtration systems and bottled spring water.

I hope that the reader will understand that there is no magic taking place at water treatment plants, and that individuals are capable of treating contaminated water in their own home in much the same way as it is done at a water treatment plant. I should note that I do not advise anyone to drink water that may be unsafe, or to treat unsafe water for drinking. The materials and methods I describe may be hazardous if proper care and proper safety equipment are not used. Because I have no control over the quality of your source water, or the procedures you employ, I can not make guarantees and will take no responsibility for injury or illness that may result from this information. I am not providing explicit instruction or advice. In an extended grid-down scenario, however, almost every activity will come with a heightened degree of risk, and at that time only you will be responsible for making risk assessments concerning water availability and water quality.

I can say that I have personally used the method I am presenting here to treat and drink small amounts of water from a canal in the downtown area of a large southwestern city. The water I drank did not pass through a water filtration system as I advise in the final step below to insure absolute safety. I felt there would be no point in using the Berkey as part of the test because the Berkey is quite capable of handling contaminated water without prior filtering or treatment. My method is intended for a maximum production of just over 12 gallons of water per hour. This volume of water is more than suitable for bathing and cooking, and somewhat suitable for drinking. However, the final step for absolute safety would be a pass through a Berkey or similar filtration system or by boiling.

Required Materials

  • This is a list of materials you will need to set up your water treatment system and should not cost more that $200. [In 2014 USD]
  • Aluminum Sulphate – Known as Alum, a 5lb. tub can be purchased at any pool supply store for $15. This is a type of flocculent which will make suspended solids in cloudy or turbid water stick together and sink to the bottom of the container. See flocculation in action in this video.
  • Calcium Hypochlorite, commercially known as pool shock. A one pound bag costs $5 or less.
  • Five gallon white food grade buckets, at least two.
  • Five gallon colored non-food grade buckets, such as Homer bucket from Home Depot, at least three.
  • Sturdy glass bottles with ground glass stoppers (laboratory grade glass) to safely store the calcium hypochlorite. These can be expensive.
  • Basic pool chlorine/PH test kit. Buy additional of testing solution.
  • Fifty-five gallon plastic drums. You should already have several of these in your backyard.
  • Cloth filter. I use a Singed Polyester Felt Filter Media Fabric Sheet for use in aquariums.
  • Hydraid Biosand Filter. See contact information below.
  • Pool filter sand.
  • Aquarium gravel. Ten pounds with smooth rounded edges approximately 1/8 of an inch in diameter to 1/4 of an inch in diameter
  • Aquarium gravel. Ten pounds with smooth rounded edges approximately 1/2 of an inch in diameter to 3/4 of an inch in diameter.
  • One gallon plastic jugs. Two or three will be enough, and they should be clean. Do not use milk jugs.
  • Measuring spoons. This set should be dedicated for water purification and not used for cooking.
  • Tuna Fish can, 4.8 ounce to 5 ounce. Can should be cleaned thoroughly.
  • Twelve ounce jar or can with lid removed.
  • Five pounds of non-galvanized iron nails, three to four inches long. The rustier the better, and if they are new out of the box, make sure they are wiped clean, and completely free of grease. This is only necessary if you are concerned about mitigating the arsenic in your source water.
  • Activated carbon or charcoal pellets.

Some important notes on materials:
Pool Shock
Calcium Hypochlorite is a dry form of bleach with chemical compound Ca(CIO)2 better known as “pool shock” and can be purchased at Walmart, Home Depot, or any pool supply store. Avoid pool shock with clarifiers or anti-foaming agents. A concentrations of 78% or higher is preferred, but do not buy anything lower than 65% Ca(CIO)2.

This powdered form of chlorine is superior to liquid bleach because it has a very long shelf life, very compact and is highly portable. Calcium Hypochlorite is very caustic to the skin. The fumes can burn eyes, lungs, nasal passages and sinuses; seep into your food storage; ruin the biolayer in your biosand filter; and it will rust every tool in the shed if not stored properly. You must wear chemical resistant gloves and eye protection and work in a ventilated area when handling this stuff. I always handle Calcium Hypochlorite on the back patio, and only if there is no breeze. You do not want to be down wind if there is a breeze.

Pool shock must be stored in glass labware with ground glass stoppers only. Do not use mason jars, Dutch beer bottles with ceramic stoppers and rubber gaskets, or corked wine bottles. Over time, the chlorine gas will eat through rubber gaskets, plastic, cork, and even metal. So, do not take a shortcut on this because chlorine gas is no laughing matter.

For safety reasons, pool shock must be kept dry like regular dry pool chlorine. Refer to the safety guidelines on the packaging.

I keep my pool shock in reagent bottles, and I carefully pack the sealed bottles inside Home Depot buckets with bubble wrap to cushion the glass. I then seal the bucket tightly with the bucket lid. The bottles and buckets are clearly labeled with information about the contents, with warnings like “keep dry”, “caustic”, and “fragile”.

You might be thinking at this point, “Why take the risk? Why not just keep a few bottles of Clorox around instead of this dangerous dry chlorine?” Understand that liquid bleach has a short shelf life. It loses its efficacy at an unacceptable rate, and within a year or two your bleach will be useless. You cannot rely on weak bleach to disinfect your water. With unknown potency, you will be playing a guessing game with ratios, and over time you will effectively have no bleach at all. Consider the following:

  • Currently, a one pound bag of pool shock costs about $10.00 or less.
  • This one pound bag of pool shock has an unlimited shelf life, if it is stored properly.
  • A one pound bag of pool shock will make 128 gallons of stock chlorine solution, the equivalent of 128 gallons of bleach.
  • This 128 gallons of stock chlorine solution will disinfect 12,800 gallons of contaminated water.
  • If you factor in weight, cost, and value, there is no other item in your preps that can come close to a bag of pool shock. Twenty pounds of pool shock stored at your retreat translates into 256,000 gallons of clean water. Should you ever need to bug-out, one or two pounds would be very easy to pack.

Hydraid Biosand Filter
The filter
The Hydraid biosand filter stands two and a half feet high. It is roughly one and a half feet wide at the top with a taper leading down to a smaller diameter base. Unlike traditional concrete filters, which are often constructed on site, the Hydraid is plastic and very light weight when empty. The Hydraid looks a lot like a small round plastic recycle bin with a PVC pipe running up the length on the outside. For those unfamiliar with biosand filters, please look at this video.
The design of the filter is brilliantly simple in one sense because it looks to be just a plastic trashcan filled with four inches of rocks on the bottom, a few feet of sand on top and a PVC pipe running out of the bottom and up the side. The complexity of the design is not so apparent. The biosand filter works several ways:

  1. The first phase is biological predation where micro-organisms feed on dangerous pathogens. The top surface of the sand at the top of the filter perpetually sits below several inches of water, and develops a biological layer of beneficial organisms which consume and remove parasites and pathogens up to 99.8%.
  2. The second phase is mechanical filtration. The sand acts as a mechanical filter, physically trapping debris and pathogens.
  3. The third phase of filtration is adsorption. The filter media emits an electrical charge of sorts and pulls the remaining debris to it like a magnet.
  4. From this point, the water slowly filters down through the last few feet of sand which is devoid of light, food and oxygen, killing off any remaining organic pollutants and pathogens.

It is important that no chlorinated water, tap water, iodine, or chlorine gas ever come into contact with the biolayer because the disinfectant will kill off the beneficial organisms, thus destroying the biolayer. It is also important to place the filter indoors and in an area where it will not be disturbed. If the filter is placed in a high traffic area and it gets bumped or rocked, the biolayer may be damaged.

Contaminated water should always be poured onto the diffuser plate where it will drip gently down onto the biolayer. Water should never be poured directly onto the biolayer, as that too will damage it. By being consistent with your source water, the biolayer will develop organisms specifically catered to treat water from that source. A biolayer formed from canal water may not be so effective against pathogens from harvested rain water.

According to the Hydraid brochure, the filter is capable of producing 12.4 gallons per hour with intermittent use. This amount of water serves the daily needs of eight to ten people. If you consider that one person requires one gallon of water per day just to survive, 12.4 gallons per hour would be a luxury for you and your family in a long term survival scenario.

Triple Quest Company and ordering information
Before ordering, you must understand the intended application for this filter. The filter needs to be set up correctly with the filtration media. It needs to be primed for several weeks to let a biolayer develop, and it needs to be used and maintained on a consistent basis. None of this is especially difficult, but it does require some commitment, unlike ceramic or carbon filters which are more “plug and play”. In an extended grid-down scenario, as in months or years, the biosand filter would be a perfect choice. The biosand filter is not a good choice for those prepping for short term events like hurricanes, floods, or temporary civil unrest. Someone living in a remote area without well water but access to a stream or pond, could definitely rely on one or two Hydraid filters. A Hydraid would not be suitable for a vacation cabin because it would not be used and maintained with regularity.

From what I understand, the Hydraid is not intended for use in this country, and it is not marketed as a retail item. Triple Quest manufactures these filters for Non Governmental Organizations (NGO’s) like UNICEF who provide aid to families in developing countries. Triple Quest is geared for handling orders by the pallet load to be shipped overseas. Triple Quest is not accustomed to filling orders of one or two units for domestic use, so please take this into consideration when ordering your filter. By doing business with Triple Quest, you are supporting their humanitarian operations. Whether they would admit to it or not, they are doing God’s work by providing, free of charge to the poorest of the poor, a device to filter horribly contaminated water.

Though research has shown the Hydraid to be incredibly effective against biological contaminants, parasites, and pathogens, Triple Quest will not recommend it for general use in this country. The filter is intended for use by people in developing countries living in squalid conditions. It may be that another reason Triple Quest cannot promote these filters for the American market is because they have no control over the water source that the user may attempt to filter with their product. Should the user not follow the installation and maintenance instructions properly or try passing water contaminated with diesel fuel or chlorinated tap water through the filter, the end result would reflect poorly on the product and could leave the company exposed to endless litigation. This is just my guess as to why these filters are not marketed to the public.

To order a Hydraid BioSand filter, contact Triple Quest at (616) 254-4222.

Sourcing local filtration media
When you place your order for a Hydraid filter, do your wallet a favor and order the filter only. If you order the filtration media, you will have to pay shipping on 106 pounds of sand and rock, all of which can be purchased at a swimming pool store and aquarium supply store for a lot less. When you place your order, ask how many pounds of each type of media you will need. By purchasing just the filter, which includes the plastic body, lid, diffuser plate, and outlet pipe, you can probably spend about $70.00, including shipping. If you opt to pay for the load of sand and rocks, the cost will be at least twice that amount. It would make more sense to spend that money on an additional filter to give to a family member or friend.

Inferior designs and short circuits
Do not attempt to rig a common trash can with a PVC standpipe for use as a biosand filter. Most trash cans are made out of low density polyethylene and will easily flex and bow out at the sides, creating a short circuit of sorts where the water on top bypasses the sand filter entirely, running down the sides to the bottom where it will enter the outlet tube. The Hydraid is made from a higher density polyethylene and is rigid enough to prevent a short circuit. Likewise, never build a biosand filter with the standpipe tube running up the inside of the filter. This will also create a short circuit, as the water on top will follow the outer wall of the PVC pipe right down to the bottom, bypassing the filtration media. I have seen several how-to videos on how to construct one of these dangerously designed filters on Youtube, many of which are too painful to watch. This video demonstrates the wrong way to build a biosand filter.
Because the consequences of drinking contaminated water are so severe, stick with the design that is tried and true.

The best filtration media for the biosand filter is pool filter sand. This sand can be found at Home Depot and swimming pool supply stores. Do not use masonry sand, play sand, or beach sand. The size of a coarse grain of sand like what you would find in a sandbox is measured in fractions of a millimeter. The size of a fine grain of sand, like pool filter sand, is so small it is measured in microns. The organisms we are trying to keep from entering our bodies are in the micron range and will easily pass right through coarse sand. The size of the grains in a bag of pool sand are very consistent, ranging between 10-40 microns.

Activated Carbon (Charcoal)
If you do not have a Berkey system, you can make a carbon filter with activated charcoal/carbon pellets from Walmart or an aquarium store packed into a 2 liter plastic bottle with the bottom cut out. This carbon filter is in no way as capable as a Berkey, but it will remove excess chlorine, heavy metals, and fluoride from your water, making it safer and giving it a much cleaner taste. These pellets are relatively cheap and easy to store in bulk. Never filter your water with charcoal intended for BBQ grills, whether it was treated with lighter fluid or not. Grilling charcoal is not activated, so it makes for a poor filter. This type of charcoal is also very good at absorbing airborne contaminants right through its paper bag as it sits on the shelf at the hardware store for months on end. The charcoal will absorb nearby pesticides from the garden section and petrochemicals from the quick light charcoal bags sitting a few feet away.

Before beginning, understand that this process is not guaranteed to remove pesticides, heavy metals, or petrochemicals, unless a Berkey filter is used in the final step. It is important to find the cleanest water source possible. However, do not collect chlorinated water or add chlorine or any other disinfectants on the front end of this process. Chlorine and other chemicals will damage the biolayer of the filter. Once your biosand filter is set up and primed, you can begin. You can see the proper set up in this video.

  1. Collect surface water in colored 5 gallon bucket. Filtered water should never be poured into a colored bucket, and raw untreated water should never come in contact with a white food grade bucket.
  2. Cover the bucket and let the water sit undisturbed for a day.
  3. Sediment should have settled to the bottom. Place a cloth or a Singed Polyester Felt Filter Media Fabric Sheet over another colored bucket and carefully pour the clear water into the bucket, making sure not to let any sediment enter the second bucket. Clean out first bucket and rinse the Singed Polyester Felt Filter Media Fabric Sheet.
  4. Place a clean empty white bucket underneath the vinyl outlet tube of the Hydraid biosand filter.
  5. Remove the lid from the top of the filter and gently pour the water onto the diffuser plate. Be very careful that not even a drop of the contaminated water drips down into the clean white bucket sitting on the floor. Pour the water slowly and carefully. Place the cover back on top. Filtered water should begin flowing into the white bucket as the water in the filter finds equilibrium.
  6. Store the filtered water in a clean 55 gallon drum designed specifically for water storage.
  7. Repeat the filtration process until the drum is nearly full. Leave a little room for your chlorine solution.
  8. Put on eye protection and chemical resistant gloves.
  9. Pour a half gallon of water into a one gallon jug. Add 1/8 of an ounce (about 1/4 teaspoon) of pool shock to the jug. Cap the jug and gently shake or swirl the contents until they are dissolved. Fill the jug with water until it is about full.
  10. Pour one half gallon of the chlorine stock solution into the 55 gallon drum and let it sit for a day.
  11. Collect a small amount of treated water from the drum and run a chlorine test with your pool test kit. A chlorine reading under 0.2 parts per million (ppm) is too low, and is not considered safe according to the EPA. A higher chlorine reading around 3.5 to 4.0 will make for very unpleasant tasting water and can cause health problems over time, but you can be assured that all pathogens are dead. If your water has a chlorine level between 0.2 and 4.0 ppm, it is safe to bathe with, wash clothes, and probably safe enough to drink.
  12. For additional peace of mind and for improved taste, it would be a good idea to run your drinking water through a Berkey or other charcoal filter one or more times to remove all chlorine and any residual contaminants. The pre-filtering and slow sand filtering with the Hydraid will no doubt greatly extend the life of your Berkey filters.

If you wish to bypass the biosand filter altogether and run all of your water through a Berkey or other carbon filter, I suggest the use of Alum in addition to performing steps 1 through 3 above . The Alum acts as a flocculent, which pulls together all of the undissolved solids floating around in the water, most of which are too tiny to be seen. I have not been able to find any information regarding Alum and potential interference with the biolayer of the filter, so I never flocculate water before running it through the biosand filter. I imagine that the Alum would be indiscriminate, and remove many of the beneficial micro-organisms from the water as well as the dangerous pathogens.

  1. Collect surface water in colored 5 gallon bucket.
  2. Cover the bucket and let the water sit undisturbed for a day.
  3. Sediment should have settled to the bottom. Place a cloth filter or Singed Polyester Felt Filter Media Fabric Sheet over another colored bucket and carefully pour the clear water into the bucket, making sure not to let any sediment enter the second bucket. Clean out first bucket and rinse the Singed Polyester Felt Filter Media Fabric Sheet.
  4. Fill the empty tuna can with Alum, then scoop the Alum into an empty water jug. Fill the jug about half way with water, cap it and gently shake for a few seconds.
  5. Pour the alum solution into the bucket of water, cover and let sit for a day. Rinse out the jug that contained the Alum solution.
  6. After 24 hours, the water should be very clear and clean looking, and a fair amount of sludge and scum will be resting on the bottom of the bucket. Again, carefully pour the clear water into a clean bucket, making sure not to let any sediment enter the second bucket. Clean out first bucket.
  7. Add 16 drops of your chlorine stock solution, mix well, cover and let sit for a few hours. See step 9 above for instructions on making chlorine stock solution.
  8. This water is now ready to be poured into your Berkey or homemade carbon filter.

If you wish to treat more than five gallons of water at one time, refer to the following ratios to create a flocculent solution.

  • Five gallons of turbid (cloudy) water requires one half gallon of Alum solution made up of 5 ounces (empty tuna can full) of Alum powder mixed with one half gallon of water.
  • Ten gallons of turbid water requires one gallon of Alum solution made up of 10 ounces of Alum powder mixed with one gallon of water.
  • Twenty five gallons of turbid water requires two and a half gallons of solution made up of 25 ounces of Alum powder mixed with two and a half gallons of water.
  • Fifty gallons of turbid water requires five gallons of solution made up of 50 ounces of Alum powder mixed with five gallons of water.

One gallon of chlorine stock solution will treat one hundred gallons of biologically unsafe water.

One quarter teaspoon (1/8 of an ounce) of pool shock added to one gallon of water will make enough stock chlorine solution to treat 100 gallons of water.

Twelve to sixteen drops of stock chlorine solution will treat one gallon of water. Depending on the concentration of Ca(CIO)2 in the pool shock you use to make the solution, it may require more or less. Test chlorine levels with your pool test kit.

The process described in detail above can be broken down into four steps:

  1. Screening and pre-sedimentation.
  2. Coagulation, flocculation, and sedimentation.
  3. Filtration.
  4. Disinfection

These are the same basic four steps that your municiple tap water is subjected to before it reaches your faucet. The chemicals, agents, and methods presented here are very similar to those used by water treatment facilities.

If you suspect that you have arsenic in your source water, there is a simple modification that can be made to a biosand filter. I tacked this on the end because most people will not have to worry about this problem. Parts of Southern California, Arizona, North Dakota, South Dakota, Minnesota, Maine, South Texas, North Texas, Massachusetts, and Montana have concentrations of 50 or more micrograms per liter in their ground water.

Some arsenic is naturally occurring and enters the water supply through runoff of eroded natural deposits. Runoff from farms and waste from glass and electronics production are other sources of arsenic. The modification I made to my Hydraid is a simple one, and it involves nothing more than a few pounds of non galvanized rusty iron nails placed on top of the diffuser plate of the biosand filter.

Without getting too technical, arsenic in the water is attracted to the iron oxide in the rust, which then flakes off and becomes trapped in the sand, never making it more than an inch or two into the filter. Without the rust, arsenic would pass through the sand unobstructed.

I hope that I have demystified the process for treating water and that there is no magic taking place at water treatment plants. All of these steps to treat water, except for chlorination, are just an accelerated simulation of the natural process of filtration and sedimentation. With these basic materials and instructions, anyone can begin learning how to treat contaminated water. By familiarizing yourself with the Hydraid biosand filter, you will learn the mechanics of how these filters work, and you will carry this knowledge with you wherever you go, whatever the circumstances. At some point, if the need should arise, you may even be able to construct a large capacity biosand filter out of concrete or masonry block, with scavenged materials. Now is the time to learn and perfect this skill.

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