Can I use a storm-water pond as a back-up source of water?

Storm-water ponds are the closest alternative source of water for many people living in urban areas. In an emergency this source of water may be all that is available to you.  Eventually any water you have stored will be consumed and the water in a storm-water pond may be the difference between life and death.  With the proper treatment your local storm-water pond can be a great backup source of drinking water.

Industrial storm-water pond (source: info.evergreen.ca)

Storm-water presents a unique set of challenges during treatment. Because storm-water ponds collect surface water, the water is exposed to all the contaminants on the ground in the catchment area. This includes but is not limited to pesticides and fertilizers applied to lawns, motor oil and gasoline leaking from vehicles and litter like cigarette buts. It all ends up is the storm-water pond. Those chemicals are already in storm-water ponds on a normal day. During an emergency there may be additional contamination from sewage runoff from an overloaded or broken sewage system. The water in the pond will also contain all the microorganisms like ecoli, giardia and cryptosporidium normally in surface water. Any one of these will make you very sick if you get infected with them.
Finally, there will be high levels of nitrates in storm-water ponds. Too much nitrates consumed by young children can cause blue baby syndrome.

The first step in treating water from a storm-water pond is straining. Straining the water through a cloth or loose sand filter will remove large particles (ones you could pick up with your fingers). Remove as much of the suspended particles from the water as you can. Straining the water first will extend the life of your proper water filter.

If you have a clarifying agent like aluminum sulfate, this is the best time to add it to the water.  It will make contaminants too small to be filtered become attracted to each other and become significantly larger.  Larger particles are easier to remove from the water. Let the water sit still for at least 30 minutes without disturbing it.  All the newly formed large particles (called floc) will sink to the bottom.  When you take the water from this container, make sure you leave the majority of the settled material at the bottom of the container.

Urban Storm-water pond (source: greenbmp.blogspot.com)

The next step is to filter the water. Filter the water even if it looks clear, the human eye is five times too weak to detect dangerous levels of particles. Filter the water at least once through an activated carbon filter. Activated carbon is known to remove many different chemicals from water including pesticides, chlorine and fluoride. Activated carbon is not the same as charcoal. Charcoal is similar, it can remove toxins from water but it is nowhere near the efficiency of activated carbon.

The third step is oxidation. Oxidation will help with disinfection as most disinfectant chemicals are also oxidizers. Chemicals like sodium hypochlorite and potassium permanganate are both oxidizers and disinfectants. Oxidation will break down many of the remaining contaminants and inactivate many of the remaining bacteria. Keep adding the oxidizer/disinfectant till you can detect a residual after 20 minutes. The 20 minutes is the minimum you should wait for a gallon of water. Wait longer for larger volumes. This is because oxidation is a chemical reaction that isn’t instant. It needs time to complete the reaction.

The fourth step is to filter the water again. Filtering again is necessary because the disinfection/oxidation step will create some potentially carcinogenic byproducts. We filter before oxidation to minimize the amount of chlorine (or other chemical) and to limit the possibility of forming dangerous byproducts. We filter the second time to remove any byproducts that have been formed.

The final step is to boil the water.  This will help with disinfection, but the main goal of boiling at this point is to remove any volatile chemicals.  Any chemical with a boiling point lower than water will be removed after boiling.

A note about disinfection.  If all of these steps are followed there is no need for a step dedicated for disinfection.  Between the oxidation and the boiling of the water any microorganisms will be inactivated.  If you are storing the water for a long time then add some sodium hypochlorite for a residual disinfectant.  The residual disinfectant will prevent the water from becoming recontaminated before you drink it.

One additional possible step is to aerate the water.  Ponds are frequently stagnant.  Stagnant water is green with algae, it smells bad and tastes worse. After the water is made potable, transfer the water back and forth between two glasses. This adds oxygen to the water and will make the water taste better.

This may seem like a lot of work for something as small as a storm-water pond.  What I have described are the basic steps to turn the potentially toxic water in the pond into clean and safe drinking water.

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Why?, How? And How Much? Of Storeing Water

Storing water is often the fist step in becoming more prepared. People need water everyday for a variety of reasons. Humans can go up to three days without water, however the effects of dehydration can be felt in as little as a few hours if you aren’t careful. In an emergency water use and water needs will change and they will never change in ways where you need less water.

On the surface storing water is just filling containers with water and walking away. If that is all you do then you will regret walking away relatively quickly. The only thing worse than ignoring your stored water is not having any stored water.

Why store water? It buys you time. Time to “wait it out” or time to find more water. This time will allow you to focus on and accomplish other tasks. Other demands for your time will abound in even a minor emergency. If keeping some water around means you can focus on security or damage control then it is definitely worth the effort.  I have written another article about why a back up supply of water is important.

Plastic Bottles are a Simple Way to Store Water (source: quiet-environmentalist.com)

How water can be stored depends on a few factors. Cost and storage space are the biggest factors affecting how you store water. Purchasing bottled water is a good way to start for small places with small amounts of storage. Bottled water is can be very expensive if you want to store a lot of water (more than 72hrs).

The next option is a larger container designed holding water. These containers are available is almost every size. If you can’t find the size you want in a store, there are companies that can make custom shapes and sizes. There are very few limits to the type of container. I mentioned earlier that the container needs to be designed for water. This is for two reasons. First, not all plastics are created equal. Some plastics can leach harmful chemicals like BPA into the water. The best type of plastic is high density polyethelene (HDPE).  HDPE is used on all sorts of applications, including water/chemical tanks and watermains.  Look for the symbol of a triange made of arrows around the number 2 and the letters HDPE underneath to make sure it is the correct one.

HDPE Symbol (source: termoplasticos.com)

Second, water is heavy. One liter of water weighs one kilogram (2.2 pounds). If the container isn’t designed for water there is a good chance it will break. For example a rain barrel holds around 400L, that barrel full of water will weigh over 400kg (or approximately 881lbs).  Below is a photo of a 1000L container, when full this container weighs one metric tonne (1000kg or 2204lbs).  The surface under this container needs to be secure and able to support the weight.  You also need to factor this weight into the support for the container and the shelving unit you store the water on.

1000L or 275 Gal Tote Excellent for Storing Water (source: http://www.theoldbarrelhouse.com)

Larger tanks need to be air tight. Otherwise the water remains open to contamination. Read here to learn what to do when your back up source of water becomes contaminated. The access point if it is on the top also needs to be air tight when closed. The access point needs to be raised above the rest of the tank so no water/cleaners/dust flows into the tank. If the water does become contaminated, read What to do when your back up supply is contaminated.  The tank will also need a spigot for accessing the water in the tank. The spigot should be installed just above the bottom of the tank (like it is in the picture above). Keeping the spigot just off the bottom avoids drawing any sediment that has settled on the bottom of the tank. Raising the spigot also makes it easier to fill containers.

There is are many theories for what kind of container is best. One big one or many little ones or a combination of sizes. This is a decision everyone needs to decide for themselves.  The general theory for using small bottles is that you can rotate your supply and if a small container becomes contaminated or leaks then you still have a safe supply in other bottles.  The general theory in support of large containers is that you can store a lot more water. You can also put pumps into large tanks an pump water to other areas.  With a pump and some tubing you can have a back up plumbing system or pump directly into your existing plumbing.

Now for the big question, how much water do you need to store?  According to the USGS, the average American household uses 80 to 100 gallons per person of water a day (302 to 378 L/person/day).  Now this is for ALL uses, many of which are in our appliances like dishwashers and washing machines.  But if you want everything to be EXACTLY as normal, then 100 gallons per person per day is what you need to store.  A family of four, will need 400 gallons/day and most emergencies are longer than one day.  This will quickly become an unreasonable amount of water to store.  This is where water conservation comes in.  Using less water makes your supply last longer.  I can’t give you a minimum storage volume.  The minimum amount of water that a human needs is variable on too many factors, like age (seniors and babies need more), climate, external temperature (hot and cold), altitude, health conditions, illnesses, type of disaster (some require a lot more washing), pregnancy, activity level, existing hydration levels and this list can be a lot longer. I will say this, having more water than you need is better than not having enough.  Listen to what your local authorities are recommending you store for your area and treat that as a minimum.  The correct answer of how much water to store is in between the 100 gal/person/day and the minimum recommended for your area and time of year.

I hope this article helped you understand a little more about the importance of storing water and a lot more on how to get your water supply started.  Everyone’s water storage solution is unique to them.  Balancing space and money mean that you will have to develop a system that works for you.