How to filter water

How to filter water

On a Season 5 episode of the popular, post-apocalyptic television show “The Walking Dead” a group of survivors find themselves out of clean water in an unfamiliar area. The character Rosita takes an empty plastic bottle, cuts off the bottom and begins to fill it with sand and rocks. She then begins to slowly pour cloudy water from a nearby stream through it. The episode didn’t show the necessary step of sterilizing the water after filtering (whether through boiling, disinfection with a chemical agent such as bleach, or UV exposure to sunlight) This method does work and can keep you heathly if clean potable water or a manufactured water filter system are unobtainable.

It is important to try and find the cleanest water available, and under no circumstances should you try and filter sewage runoff or irradiated water using this process.

How to filter water

Materials Needed

  • Plastic bottle or comparable food-safe container
  • Another container for clean water
  • Clean cotton or cheese cloth
  • Coffee filter or porous cloth
  • Charcoal
  • Sand (fine and coarse)
  • Gravel or pebbles

How to filter water

Step 1 – Cut Bottom Off

Use scissors or a knife to cut off the bottom part of the bottle you will be putting the filter material in.

How to filter water

Step 2 – Cut Drain Hole

Use scissors or a knife to poke a small hole in the cap. If there is no cap, cut off top of the bottle instead of the bottom for previous step then poke several small holes in the bottom of the bottle.

How to filter water

Step 3 – 1st Layer: Straining Fabric

Stuff the bottom of bottle with a fine cloth or paper fabric, such as a coffee filter, cheese cloth or cotton stuffing.

Sand and grass can also be used in this first stage. Fill the bottom with about 3 inches of grass clippings to filter out larger particulates and help give water a clean taste from chlorophyll contained in the grass. Then fill with 3-4 inches of very fine sand.

Be careful not to use poisonous or unidentified weeds when collect grass clippings. Do not use Highway Department sand, as it can be full of road salt and chemicals.

How to filter water

Step 4 – Break Up Charcoal

Take charcoal from campfire or BBQ charcoal (do not use match/instant light type because it’s soaked in chemicals) and use hammer or rock to break it down into smallest particles you can.

How to filter water

Step 5 – Layer 2: Pulverized Charcoal

Pour about 3 inches of pulverized charcoal into bottle. If available, cover with another coffee filter to prevent charcoal from being displaced to much during filtering.

How to filter water

Step 6 – 3rd Layer: Fine Sand

Add a 2-3 inch layer of the finest sand you can find. This and the subsequent layers you will add are to filter out particulates in the water.

Do not use Highway Department sand, as it can be full of road salt and chemicals.

How to filter water

Step 7 – 4th Layer: Coarse Sand

Add a 2-3 inch layer of coarse sand or very small small pebbles.

How to filter water

Step 8 – 5th Layer: Fine Sand

Add an additional 2-3 inch layer of the fine sand. Multiple varying filter stages (like a reverse osmosis system) ensures that most of the particles present in the water are caught.

How to filter water

Step 9 – 6th Layer: Gravel

Add a 2-3 inch layer of gravel or small rocks to prevent the water being poured in from displacing the sand.

How to filter water

Step 10 – Top Strainer

Cover top of filter with a piece of porous cloth, such as a bandana or cheese cloth. This step is optional but helpful in straining any large debris from the water and stop the pouring from displacing the sand inside the filter.

How to filter water

Step 11 – Pouring & Collecting

Pour water slowly into filter while holding it over the second container.

Make sure to wipe off or clean the collection container. Pour water slowly so as not to disturb filter layers too much or to cause filter container to overflow and possibly spilling unfiltered water into collection container.

How to filter water

Step 12 – Sterilize Water

Even though you have filtered the water through many different layers, microbes can still exist in the water and it still needs to be sterilized. Boiling the water in a pot or kettle is the easiest way.

You can also use sunlight to sterilize water. Pour filtered water into a clean, clear plastic or glass bottle up to 3/4 full and screw on cap. Shake for thirty seconds to add more oxygen to the water. Place on light or reflective surface in direct sunlight. The amount of exposure it needs it dependant on weather conditions. A clear day requires 6 hours of exposure whereas 50% or more cloud coverage will require 2 days of sunlight.

Step 3: Consider how the filter fits your home, lifestyle, and budget.

Many different types of filters are available to consumers. Determining which type is most appropriate for you—or whether you need a filter at all—depends on what functions you want a filter to provide. No filter eliminates all contaminants, so understanding what filters do and do not do is important.

What does the filter remove?

Read the label to see if it is NSF-certified. If it is, you can search NSF’s database external icon to learn more about what a particular model is certified to protect you against. Labels on water filters also typically state the contaminants that are reduced, which can help to guide your choice. Be sure to read labels carefully yourself and verify the manufacturer’s claims with an independent source, as not all sales representatives will be familiar with your needs.

Keep in mind that most brands include many different types of filters. Sales people might be able to help you make an appropriate selection, but remember that they are sometimes paid to sell a particular brand. You should check claims and read the fine print on filter packaging for yourself and ensure that it will work for your purposes before purchasing.

Don’t assume that if the filter removes one contaminant, it also removes others. Filters that remove chemicals often do not effectively remove germs, and vice versa. Some water treatment devices that remove chemicals, such as reverse osmosis, ion exchange, or distillation systems, might also remove fluoride. Children who drink water with levels of fluoride <0.6 ppm might need a fluoride supplement. Check with your child’s pediatrician or dentist for specific recommendations.

How much does the system cost?

The prices of different filtration systems can vary widely, from simple systems that can cost under $20 to complex systems costing hundreds of dollars and requiring professional installation. In addition to the price of purchasing and installing the system, consider the cost, schedule, and ease of maintenance, such as changing filter cartridges. In order to continue to work properly, all water treatment systems require maintenance.

How much filtered water do you need?

Some filters are slow, while others can filter large amounts of water quickly. If you only need the filter for personal drinking water, you may not need a fast filter.

What kind of system do you need, and how does it fit into your home?

Filters commonly found in homes and stores include water filter pitchers, end-of-tap or faucet-mounted filters, faucet-integrated (built-in) filters, on-counter filters, under-sink filters, and whole-house treatment units. No filters or treatment systems are 100% effective in removing all contaminants from water, and you need to know what you want your filter to do before you go shopping (see Step 1). Not all filters of a particular type use the same technology, so you should read the label carefully.

Water filter pitchers are pitchers that are filled from the top and have built-in filters that water must pass through before being poured out for drinking or other use.

  • Pros: Inexpensive to purchase, no installation, easy to use
  • Cons: Vary by model and pore size, filters must be replaced regularly, slow filtering

Many refrigerators have a built-in filter that supplies water through the door and supplies an automatic icemaker.

  • Pros: Come with many refrigerators, often improve water taste, may also filter water used for making ice, easy to use
  • Cons: Filters must be replaced regularly

Faucet-mounted filtration systems attach to a standard faucet and can be switched on and off between filtered and unfiltered water flow.

  • Pros: Can easily switch between filtered and unfiltered water, relatively inexpensive
  • Cons: Do not work with all faucets, may slow water flow

Faucet-integrated filtration systems are faucets designed with built-in filters (instead of an attached filter, like a faucet-mounted system) and require installation.

  • Pros: Can easily switch between filtered and unfiltered water
  • Cons: Often expensive, require installation

Faucet-integrated filtration systems are faucets designed with built-in filters (instead of an attached filter, like a faucet-mounted system) and require installation.

  • Pros: Can easily switch between filtered and unfiltered water
  • Cons: Often expensive, require installation

Under-sink filtration systems are installed under a sink and send water through a pipe to the filter’s own specially installed faucet.

  • Pros: Filter large amounts of water, do not take up countertop space
  • Cons: Often expensive, may require modifications to plumbing

Whole-house water treatment devices treat all water entering the house, not just the water used for drinking.

  • Pros: Treatment is applied to all water entering your home, which may be important for hard water and volatile organic compounds (VOCs)
  • Cons: Often expensive, may require modifications to plumbing, may require professional maintenance, filtering that removes chlorine might increase growth of germs in all the pipes in your house

Treatment devices

This table shows some benefits and limitations of a few popular home water treatment technologies. It does not include information on all filter types including many those that might remove germs via simple pore size filtration. Also see Technical Information on Home Water Treatment Technologies.

How to filter water

Is it safe to drink this water? I ask myself that question often and most of the time the answer is no. There often is the risk that bacteria, chemicals, and pathogens, specifically Giardia, are in the water. Rainwater or dew that is resting on non-poisonous plants such as moss is safe to drink as is. There are a few ways to process water to make it safe to drink: boiling it, using chemical purifiers, and filtration. This article will provide tips on how to make and use a survival water filter.

What Does a Survival Water Filter Do?

Passing water through a filter will make the water safe to drink. High-quality water filters from a store will ensure that no harmful pathogens or microorganisms are getting into your drinking water. But sometimes using store-bought, high-quality water filters might not be an option. Few people carry one of these around with them all the time. Also, the problem with store-bought water filters is they need to be cleaned, or the filter needs to be replaced fairly often. And you must remember to carry it when you’re out exploring.

Filtering Water with What You Have

The basic process of filtering water in a survival situation is to remove debris such as soil, dirt, sediment, sticks, leaves, and any animals living in the water. To create a survival water filter you will need to gather various materials such as pebbles, sand, cloth, and charcoal. If you realize you are in a survival situation, take some time to think about what needs to be done. Figure out what you have with you and how it can be used to your advantage. Most people who are lost are found within 24 hours. So don’t freak out! Keep in mind that it is not possible to filter saltwater into drinkable freshwater—regardless of the kinds of water filters you have.

Making a Basic Survival Water Filter From Scratch

The first thing to consider when collecting water is to think about how soon you will need to drink. If you have time, collect standing water in a container and let it sit for a few hours. This will allow anything that floats to rise to the surface, and you can skim off any debris.

If you have two containers, try this method for filtering water: Take the first container and fill it with water. Then, put your shirt or some sort of porous layer over the other container. Put your pebbles on top of the cloth and filter your water by pouring it over the stones and into the container. Next, remove the pebbles and put sand, a finer material, on top of the cloth. Filter your water again.

Finally, the most effective way to filter is to crush up charcoal, put it on your cloth and let the water run through it. Charcoal filters remove sediment, many contaminants, and improve the taste. Charcoal is used in store-bought home and backcountry water filters. You can make your own charcoal by making a campfire, covering it with dirt and ash, and allow it to cool completely. Once it has cooled, crush it into small pieces. Pour the water through the charcoal several times.

If at all possible, build a contraption that will combine all three filtering steps, letting the water flow from one material to another. This will make the water gradually clearer as you filter it again and again.

If you don’t have a manmade container, some natural materials are great alternatives. Bamboo is a prime example. It is hollow in the center and water can flow through it easily. There are many other plants with hollow centers. Use these to your advantage. A hollow log can be a great option. Place the materials (pebbles, sand, cloth, and charcoal) in layers through the various parts of the bamboo or log. Remember to think about what materials you are carrying and check out your surroundings in any survival situation.

This should provide you with a basic insight on how to create a survival water filter. Realize that it is still possible to get sick, even if you follow the guidelines in this article. Always contact a physician after you drink questionable water. The side effects of pathogens and microorganisms will take at least a week to start affecting you. If you are in a survival situation, keep hydrated, and worry about those side effects later.

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Not with soap! You need a filter, a device that removes impurities, like dirt, from water. The filter you’ll make here—with the help of an adult—is a super strainer, and it’ll help you clean up your act.

you will need

  • 2-liter plastic bottle, empty and clean
  • Utility knife
  • Dirty water (make your own with stuff like coffee grounds, dirt, crunched-up old leaves, cooking oil, or tiny pieces of foam)
  • Measuring cup
  • Spoon
  • Stopwatch or clock with a second hand
  • Pencil and paper
  • As many of the following filter materials as you can get: activated charcoal (available in the fish section at a pet store), gravel, sand (coarse and / or fine), cotton balls
  • Coffee filter (A bandanna, old sock, napkin, or paper towel works too!)

Step 1

Ask a grown-up to cut the bottle in half. Then flip the bottle’s top half over and put it in the bottom, so the top looks like a funnel. You’ll build your filter in the top part.

Step 2

Place the coffee filter (or bandanna, sock, etc.) at the bottom of your filter.

Step 3

Add cotton balls, charcoal, gravel, sand, and / or other materials in layers. You can use just one of them or all of them. Tip: Think about which order to add them. Bigger filter materials usually catch bigger impurities.

Step 4

Write down which filter materials you used and in what order you layered them.

Step 5

Stir your dirty water and measure out a cup of it.

Step 6

Get your timer ready!

Step 7

Pour a cup of dirty water into your filter. Start the timer as soon as you begin pouring.

Step 8

Time how long it takes for all the water to go through the filter. Then write down how long it took.

Step 9

Carefully scoop out the filter materials, one layer at a time. What did each layer take out of the water?

Step 10

Experiment! Clean the bottle and try again. Put the filter materials in a different order each time, and time each experiment. What do you discover?


The slower, the better! The longer it takes for water to move through a filter, the cleaner it gets. Water slips easily through the filter materials, but bigger gunk, like dirt, gets trapped. The filter materials usually get finer and finer, so they can catch whatever was missed earlier. Activated charcoal can be near the end of the water’s path, because it uses an electrical charge to grab particles too small for us to see.

Drinking unpalatable water is not beneficial for anybody. However, you may be in a region where the only drinking water available will give you the worst bout of diarrhea. If this is the case, then ensuring measures of natural water filtration is crucial. Certain regions of America do not enjoy the luxury to drink water straight from the tap and water treatment is common in regions like Orlando.

The cost of installing a water filtration system can be seen as an unnecessary expense but it is worthwhile at the end of the day. However, when you do not have a filtration system at hand, here’s how you can filter water naturally:

  • Sedimentation – making use of natural sediment is one of the easiest ways to filter water naturally as this involves the use of soil and rock. Sand will remove particles and if you’re also using charcoal, it will aid as an active carbon (charcoal removes volatile organic compounds, chlorine, odor and taste)
  • Only sand – using sand on its own will also work as this will pump the water through the sand by using either a slow sand filter method (removes certain pathogens), or a rapid gravity filter method (removes impurities and particles)
  • Ultraviolet light – this acts as a natural water purification system

What are water filtration systems and how will they help you purify your water?

Water filtration systems are used to make water safe to drink by removing all harsh impurities, bacteria, and pollutants, which can be life-threatening. Getting your home fitted with an efficient water filtration system will go a long way in ensuring the good health of your family. Household purification systems include the likes of reverse osmosis water purification and domestic ultrafiltration water purification.

For more information and tips on how to enjoy safe drinking water contact us today.

How to filter water

It’s extremely important to confirm your water has been purified or treated before drinking. If your water is contaminated and you don’t have bottled water, there are various water purification methods that are used today, and each method has its merits and demerits. Filtering is good for basic water tasks such as sediment and chlorine removal, but in the long run reverse osmosis is the best option. At Schultz Soft Water we focus on reverse osmosis units because they require a lot less energy and time required to make water versus distillation.

When reverse osmosis is not available, there are 4 water purification methods that you can use to make your water safe for drinking.

1 – Boiling

Boiling water is the cheapest and safest method of water purification. Water sources and or channels of distribution may render your water unsafe. For example, parasites and germs are things you may not see by bare eyes, but their effects can be life threatening.

In this method, clean water should be brought to boil and left at rolling-boil for 1-3 minutes. For people living in high altitude areas, it is recommended to boil your water for longer than water boiled at lower altitudes. This is because water boils at lower temperatures in higher altitudes. Boiled water should be covered and left to cool before drinking. For water drawn from wells, leave it for compounds to settle before you filter out clean water for use.

2 – Filtration

Filtration is one of the effective ways of purifying water and when using the right multimedia filters it’s effective in ridding water of the compounds. This method uses chemical and physical processes to purify water and make it safe for human consumption. Filtration eliminates both large compounds and small, dangerous contaminants that cause diseases with a simple and quick filtration process.. Since filtration does not deplete all the mineral salts, water that has been filtered is considered healthier compared to water purified using other methods. It’s one of the effective water purification methods that utilize chemical absorption process that effectively removes unwanted compounds from water.

Compared to reverse osmosis, filtration is considered effective when it comes to selective elimination of much smaller molecular compounds such as chlorine and pesticides. The other factor that makes filtration less costly is that it does not require a lot of energy needed in distillation and reverse osmosis. It is an economic method of water purification because little water is lost during purification.

3 – Distillation

Distillation is a water purification method that utilizes heat to collect pure water in the form of vapor. This method is effective by the scientific fact that water has a lower boiling point than other contaminants and disease-causing elements found in water. Water is subjected to a heat source until it attains its boiling point. It is then left at the boiling point until it vaporizes. This vapor is directed into a condenser to cool. Upon cooling, vapor is reversed into liquid water that is clean and safe for drinking. Other substances that have a higher boiling point are left as sediments in the container.

This method is effective in removing bacteria, germs, salts and other heavy metals such as lead, mercury and arsenic. Distillation is ideal for people who have access to raw, untreated water. This method has both advantages and disadvantages. A notable disadvantage is that it is a slow process of water purification. In addition, it requires a heat source for the purification to work. Although cheap sources of energy are being developed, distillation remains a costly process of purifying water. It is only ideal (effective and least costly) when purifying small quantities of water (It is not ideal for large scale, commercial or industrial purification).

4 – Chlorination

Chlorine is a powerful chemical that has been in use for many years to treat water for home consumption. Chlorine is an effective water purification method that kills germs, parasites and other disease-causing organisms found in ground or tap water. Water can be purified using chlorine tablets or liquid chlorine. As an off-the-shelf water purification product, chlorine is cheap and effective. However, caution should be taken when using chlorine liquid or tablets to treat drinking water. For example, people suffering from thyroid problems should talk to a medical practitioner before using this product. When using chlorine tablets, it is important to apply them in heated water, as they dissolve well in water that is at 21 degree Celsius or higher. Chlorine tablets kill all bacteria leaving your water clean and safe.

If you are looking for the best ways of treating your water, Schultz Soft Water is your best source of advice on best water purification methods and custom solutions to your water purification needs. Reverse osmosis is the best option, whereas filtering is good for basic water tasks such as sediment and chlorine removal. Reverse osmosis covers a larger spectrum of contaminant removal.

Contact our team of experienced water purification experts to give you the best water treatment solutions. We will help achieve better health for you, your family and guests.

Design and build a device that can clean a dirty water sample using materials around your home. You’ll follow the same design process used by NASA engineers and scientists when they developed the water filtration system for the International Space Station orbiting Earth. To do so, you’ll use an iterative process, meaning you’ll test multiple designs, look at how your materials get you closer to your goal, and record your findings to build the best filter possible.

Important safety note! This activity is not designed to make drinkable water. No matter how “clean” your filtered water looks, you should never drink it because it still may contain pollutants you can’t see.

› Educators, explore how to turn this into a standards-aligned lesson for students

Watch the Tutorial

See below for materials and step-by-step instructions. For more video tutorials and activities like this one, visit Learning Space.

Watch en Español: Seleccione subtítulos en Español bajo el ícono de configuración.

In this episode of Learning Space, you’ll use materials from around your home to build a device that can clean a dirty water sample like the water filtration system on the International Space Station. | Watch on YouTube

How to filter water


1-2 empty plastic water bottles

Towel or paper towels (for spill clean up)

Cheesecloth or gauze to cover the mouth of the bottle

Any materials you think will make a great filter (cotton balls, sand or gravel, uncooked pasta noodles, coffee filters, etc.)

*Don’t worry if you don’t have all of the materials. Get creative and substitute materials with what you have! It’s all part of the design process.

How to filter water

1. Create a dirty water sample

Start by preparing the water you’re going to filter. This can be done in many ways that change how difficult it is to filter the water. For example, mix some soil or dirt with tap water for an easier challenge. Try also adding food coloring or vinegar for a bigger challenge.

This dirty water sample will simulate wastewater. On the space station, this wastewater is made up of everything from the fuel that powers the station to astronauts’ sweat.

How to filter water

2. Build your filter cartridge

Until a few years ago, water needed to sent up to the space station in large containers the size of duffel bags. But in 2010, a filtration system was installed that made it so that water could be cleaned and reused onboard the space station.

To build your own filtration system, you’ll need a filter cartridge. Start by carefully cutting your water bottle in half, across the width of the bottle. Remove the cap from the bottle. Put gauze or cheesecloth over the opening and secure it with a rubber band. Turn the top half of the bottle upside down (so the part with the cheesecloth or gauze is facing down) and place it into the bottom half of the bottle.

If you want to fit more materials in your filter, you can use two bottles. You can also use larger bottles or try other containers. Note: Clear containers will help you see the filtration as it takes place.

How to filter water

3. Design your filter

The filtration system on the space station has several stages that first filter out larger debris, then smaller impurities and even bacteria. You may want to use similar layers in your filter.

Mix or layer the filter materials you’ve collected in the top of your filter cartridge. Write down what filtration materials you use and how much.

How to filter water

4. Test and evaluate the results

Pour your simulated wastewater into your filter and observe the water that comes out at the bottom of the filter. How effective was your filter at cleaning the water? Write down what you notice. How long did it take to filter the water? What worked well? What could be improved?

Important safety note! No matter how “clean” your filtered water looks, you should never drink it because it still may contain pollutants you can’t see.

How to filter water

5. Revise and try, try again!

Revise your filter based on what you saw during the last step. Then, test it again. Consider using the same amount of wastewater for each test so you can better evaluate how well your filter is working not just in terms of the color of your filtered water, but how much you’re able to clean, or reclaim.

The filtration system on the space station reclaims 93% of the water onboard. Every drop counts!

As you revise, you’ll find that some filter materials work better than others – not just at filtering out solids like dirt, but also in removing colors. Keep redesigning and testing your filter. Your goal is to produce as much clean water as possible during a single time through the filter.

How to filter water

Are you going to explore the great outdoors? It is very important that you plan for your water needs as potable water may not always be available, especially in backcountry and wilderness areas. “Potable water” is clean water that’s safe to drink, brush your teeth with, wash your hands with, and use for preparing food. Before you head out, check out the “Plan Your Visit” section on the park’s website or contact the park to find out if there are potable drinking water sources in the park and along your adventure route. Learn about any water quality alerts, such as harmful algal bacteria or chemical spills, that would affect drinking it.

Never drink water from a natural source that you haven’t purified, even if the water looks clean. Water in a stream, river or lake may look clean, but it can still be filled with bacteria, viruses, and parasites that can result in waterborne diseases, such as cryptosporidiosis or giardiasis. It is essential that you purify natural water. Purifying water involves filtering to remove large particles and treating by boiling or with chemicals to kill organisms such as bacteria, viruses and parasites.

If you plan to use natural water along your adventure, follow these steps to collect and purify water from a natural water source.

Step 1: Collect water from your source

The first step in the process is to collect the water you will drink. Here are some tips on how to safely collect water from a natural source:

Start with a clean container that preferably has been disinfected prior to use.

Wash your hands with soap and water or use hand sanitizer before collecting water so you don’t contaminate it.

Chose a collection spot that is:

On higher elevations or near the water’s source

Away from established campsites

Away from animal grazing areas.

Collect water from areas of moving water in rivers and streams, or the top few inches of a lake. Stagnant (standing or non-moving) water is a breeding ground for insects, bacteria and viruses and should be avoided.

Step 2: Filter the water

The next step in the water purification process is filtration. Filtration by itself does not purify water. It must be followed by boiling or disinfection to purify water for drinking.

Most water filters are made of a screen with many tiny holes in it. These filters can remove protozoa and some bacteria, but they cannot filter out viruses because viruses are too small.

Filters also remove bigger contaminants like leaves, silt, dirt, and sand. If the water is cloudy or has floating material in it, you should filter it even if you plan to boil or disinfect it.

Filtration systems with absolute pore size less than or equal to 1 micron filter (NSF Standards 53 or 58 rated “cyst reduction / removal) have a high effectiveness in removing cryptosporidium and giardia.

Be sure to use and care for your filter according to the manufacturer’s instructions. Filters don’t work as well if they aren’t taken care of over time.

Step 3: Disinfect the water

The final step of purification is disinfecting the water which can be done by either boiling or treating with a disinfectant. This is the most important step as these methods will kill any remaining organisms in the water, especially those that could make you sick.

Boiling is the best way to kill disease-causing organisms, including viruses, bacteria, and parasites. The high temperature and time spent boiling are very important to effectively kill the organisms in the water. Boiling will also effectively treat water if it is still cloudy or murky.

If you’re at an elevation below 6,500 feet, put the water in a container over a heat source, such as a campfire or propane stove, and bring to a rolling boil for 1 minute.

If you’re at an elevation over 6,500 feet , bring the water to a rolling boil for 3 minutes.

Your water is now ready for drinking! You can make tea or coffee if you like it hot. Let it cool down first before you put it into your container.

Disinfection happens when a chemical or UV light is added to water to kill bacteria, viruses, and other potentially harmful organisms. Many factors can impact the effectiveness of these methods including water temperature, pH, and cloudiness. With disinfectants, it is important to allow the chemical or UV light enough time to treat the water and kill the organisms before drinking – this is called contact time.

Chemical Disinfection
Chemical disinfection involves adding one or more chemicals to your filtered water that are effective at killing waterborne organisms.

Chemical tablets or liquid drops are the most common ways to disinfect natural water. Iodine or chlorine dioxide are the most frequently used disinfection agents. National Sanitation Foundation (NSF) approved products are recommended

Follow the manufacturer’s instruction for disinfecting the water. Contact time to disinfect the water varies by product (example: 30 minutes to 4 hours). If the water is cloudy or has floating debris, it will be more effective to pre-filter the water before disinfecting.

WARNING: Do not use pool-cleaning tablets to disinfect drinking water! Pool-cleaning tablets are not intended to be consumed.

WARNING: Consult with your physician before using any disinfection products. Some tablets or drops, especially iodine, may not be safe for pregnant women, people with thyroid issues or iodine hypersensitivities, or for user over long periods of time.

UV Light Purifiers

Visitors using UV purifiers to disinfect their water
NPS Photo

Portable battery-operated UV purifiers can be used to reduce bacteria, viruses and protozoa in water from natural sources. However, these purifiers are only effective in disinfecting small quantities of clear water, are battery dependent and require correct contact time with the water.

To achieve maximum disinfection, make sure you:

Pre-filter your water as small particles and sediment may shield microorganisms from the UV light.

Check that you have enough battery power. If the battery power falls below a certain level, it will not be able to safely disinfect water.

Make sure you allow for enough contact time with the water . Follow the manufacturer’s instructions because inadequate exposure to the UV light may fail to disinfect your water.

As an extra precaution: Add a small amount of your preferred chemical disinfectant to the water in your container to maintain water quality and reduce the growth of organisms in the container.

Stay Hydrated

Remember – it takes time to prepare your water for drinking. Plan ahead so it’s ready for drinking before you get thirsty, especially in hot weather. If you think you have the symptoms of water-borne disease or were exposed to potentially contaminated water, be sure to consult with your healthcare provider after your trip.

Water filtration is the process of removing or reducing the concentration of particulate matter, including suspended particles, parasites, bacteria, algae, viruses, and fungi, as well as other undesirable chemical and biological contaminants from contaminated water to produce safe and clean water for a specific purpose, such as drinking, medical, and pharmaceutical applications.

Related terms:

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Nonwoven fabric filters

10.4.2 Nonwoven water filters

Water filtration is the process of removing or reducing the concentration of particulate matter, including suspended particles, parasites, bacteria, algae, viruses, and fungi, as well as other undesirable chemical and biological contaminants from contaminated water to produce safe and clean water for a specific purpose, such as drinking, medical, and pharmaceutical applications. The filtration systems for drinking water usually incorporate a five-stage filtration process: sediment, mechanical, chemical, mineral, and bacterial.

With consideration of the requirements of avoidance of fibre shedding in the filtration process, nonwoven fabrics made from continuous fibres such as melt blown, spunbond, and hydroentangled nonwovens and electrospun/centrifugal spinning nanofibre nonwovens, as well as their composite combinations comprising both microfibres and nanofibres, are widely used in microfiltration as a water filtration media. They functions as either an independent microfiltration media or prefilters to remove a high contaminant content within the fluid to protect membrane filters.

Examples of such nonwoven filters comprising one or more layers of microfibres and nanofibres for microfiltration of specific biological contaminants were reported in US patents 2004/0038014, 2007/0075015, and 2007/0018361. Prefilters are commonly pleated or wound filter fabrics. Prefilters have a large band of retention ratings. The most common retention rating of these filters is 20 or 50 nm, and it can be engineered to all necessary applications.

In the water filtration system, membrane filters are highly efficient in filtering submicron contaminants in water, but have a deficiency of very limited filtrate holding capacity. Nanofibre nonwoven fabrics are widely used in membrane water filtration system as viral removal filters. They have two roles in the composite filter structure: they act as a separate prefilter to separate out particles of larger size than the rating of the membrane to promote the high filtration efficiency of membrane filters, and they also provide depth filtration to the membrane to improve the particle holding capacities of the membrane filtration system to extend the lifetime of the membranes. Examples of such composite liquid filtration media, comprising a layer of nanoweb adjacent to a microporous membrane, were reported in US patent 8038013 146 ; a nanofiber web containing liquid filtration medium that simultaneously exhibits high liquid permeability and high microorganism retention was reported in patent EP2408482. 147 Log Reduction Value (LRV) has been used to quantify the filters in liquid sterilisation filter tests, it is defined as the logarithm of the ratio of the total micro-organisms in challenge to the micro-organisms in filtered fluid. Microorganisms such as bacteria Brevundimonas diminuta, Mycoplasma, and other bacteria are removed from a liquid by passing the liquid through a porous nanofiber containing a filtration medium having a bacteria B. diminuta LRV (Log Reduction Value) greater than about 9, and the nanofiber(s) has a diameter from about 10 nm to about 1000 nm.

Biofouling from bacterial, fungi, and other microorganisms in the water decrease nonwoven prefilter membrane performance and increase the frequency and cost of its chemical cleaning. There are many ways to make nonwoven filters antibacterial and biocidal. Water filters could be made to incorporate biocides, including quaternary phosphonium salt, 148 polymeric phosphonium salts, 149 and onium-functionalized polymers, 150 into nonwoven filters to remove bacteria and other microorganisms. Nanoparticles having antimicrobial functionalities are also employed to remove microorganisms from water. Examples of such filters include covalently or ionically tethering antimicrobial nanoparticles (eg, silver (Ag) nanoparticles encapsulated in positively-charged polyethyleneimine (PEI)) into the surface of oxygen plasma modified polysulfone ultrafiltration membranes, 151 nanofibrous nonwoven membranes made from a mixture of poly(lactide-co-glycolide) (PLGA), and chitosan functionalized with graphene oxide (GO)–Ag nanocomposites 152 and carbon nanotubes 153 to prevent bacterial colonization on the membrane surfaces. The GO–Ag nanoparticles are bonded onto the nanofibrous membrane via a chemical reaction between the carboxyl groups of graphene and the primary amine functional groups on the PLGA–chitosan fibres using 3-(dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide as cross-linking agents.

Nonwovens made from polymers having antibacterial activities are another route to achieve antimicrobial filters. One of such polymers against Escherichia coli and Staphylococcus hyicus was synthesed 154 via copolymerization of three monomers of N,N′-dimethyl-N-alkylmethacryloxylethyl ammoniumbromide (DMAEA) with different lengths of alkyl chains (DMAEA-RB) (R-ethyl/hexyl/dodecyl), acrylic acid (AA), and acrylamide.

Water filters containing fibres, especially nanofibers, of ion exchange properties 155 have been applied in the fields of biotechnology, pharmaceutical processing, producing ultrapure water for the semiconductor industry, catalytic conversion processing, and battery technologies. 156 Polymers containing ionic functional groups might be difficult to be made into ion exchange fibres using electrospinning methods because polymer solutions with a high electric conductivity (eg, polyelectrolyte solution) prevent electric field-induced charging of the solution and lead to a low electrospinnability. Therefore, ion exchange nanofibers formed using electrospinning methods have relied on the following three approaches 157 : (1) the addition of water soluble and electrospinnable polymers to the spinning solution as the carrier; and (2) electrospinning of a nonionic polymer or inorganic materials (eg, sol–gel and carbon precursors) and successive chemical modification. 158,159