Exploration

banner reads: exploration: basics of filtration and water quality.

Why is it important to filter water?

If we were to open our mouths and catch rainfall in our mouths, there is a good chance that nothing would happen to us. When water falls from the sky it has undergone a process in which minerals are generally dissolved and it is free of solid particles. But when we use our stored rainwater, it goes through several surfaces that may not be clean, and can pick up dirt, leaves, germs, fungi and viruses. Some things that can be found in unfiltered water are:

  1. Dirt and solid particles
  2. Germs (E.coli, Salmonella, etc.)
  3. Viruses
  4. Fungi
  5. Parasites
  6. Microplastics (Learn about how these are starting to enter water resources in the United States)
  7. Sulfuric and nitric acids

Even water directly from the clouds can now carry sulfuric and nitric acids. This phenomenon is more commonly known as acid rain. In the first module, we saw this revised diagram of the water cycle:

Image labeled: Some consequences of human interference with the water cycle. Consequences are colored by primary cause: human changes in climate (orange), land cover (green), water use (blue). Volatility of endorheic lake levels from agricultural and urban land use (green). Extreme weather (drought and flood) and overall intensification of hydrological cycle (orange). Increased temperature and intermittency of river flow (orange). Flood damage from modified flow regimes (e.g. dikes, dams, and drains) and loss of floodplains and wetlands (green). Discharge from ice sheets, glaciers, and permafrost or water use (orange). Long-distance trade of actual and virtual water (blue). Groundwater depletion and contamination as reliance on subsurface water increases (blue). Land conversion alters evapotranspiration, affecting atmospheric transport to downwind catchments (green). Expansion of dead zones from nutrient loading and warmer water (blue). Sea level rise and saltwater intrusion (orange). Known and novel pollutants from agriculture, industry, and domestic activity (blue). Alteration of ocean currents and associated teleconnections with terrestrial climate (orange).

This diagram shows the impact of human activities on the water cycle. Impacts like these- like fossil fuel burning and air pollution- cause phenomena like acid rain. To learn more, check out this video from National Geographic explaining what acid rain is.


What water can we consume?

There are three general classifications for usable water that can be used when trying to identify how to appropriately use water in our surroundings. These are:

  1. Clean – clean water is water that has been filtered for solid particles and pathogens. It includes:
    • Bottled water.
    • Water that has been properly filtered.
    • In certain areas, water from the tap can be considered clean. To be safe, check with your local water service provider.
  2. Rainwater – water that has been captured from rainfall. It is considered safe for human consumption after undergoing filtration.
  3. Greywater – water that results from any household activity that is not flushing the toilet (toilet water is known as waste water). Fore more information, see the Washington Department of Health and from New Mexico State University more information. Greywater is not considered safe for human consumption, but is a good alternative for watering plants and other secondary uses. Domestic sources of greywater include:
    • Kitchen sink
    • Shower
    • Bathroom sink or other sink
    • Laundry machine
    • Dishwashing machine
    • Condensate from air conditioners and other appliances
  4. Waste – wastewater that contains any type of biological waste or materials undergoing decomposition. Water from toilets and urinals are in this category. It is the most dangerous water for human or animal consumption, it should not be used for secondary uses and should be discarded following local authorities regulations.

What are some water quality indicators?

There are several ways to test the quality of water. Depending on your country, different water testing kits or services might be available. These kits are a great alternative as they can test for pathogens as well as the pH of water. Some kits that can be ordered online are:

However, if you do not have access to these tests or find yourself in an emergency situation you might have to use other indicators to see if the water is drinkable.

  1. Color & Smell – Your senses can be important resources when trying to discern the quality of water. If water smells very strongly- like sulfur, musk or dirt- looks dark, brown, mud-colored, or anything but transparent, the safest thing to do is to assume that it is NOT drinkable.
  2. Source – Even if the water does seem fairly clear, you should always check the source of the water. For example, if you are sourcing your water from an underground well, you should routinely monitor the condition of the well to ensure that animals do not have access to it and decomposing organic matter is not being accumulated in it. On the other hand, if you are sourcing your water from the tap you can find the local organization’s reports on water quality to determine if it is potable. In Puerto Rico, the main water provider reports on water quality every two years, and these reports are accessible on their website. A simple internet search or a call to the company may help you track down the report. 

If you are not able to verify these two conditions, then you should assume that the water you have is not safe to drink and should undergo a filtration process.

Filtering at home and/or during an emergency

Learning water filtration methods is a skill that can literally help save lives during an emergency. Before jumping into emergency filtration methods, let us first understand an overview of the different filtration stages and what they work to remove.

image reads: Stage First Second Third What does it remove Particles and solids Organic Matter and other chemicals Pathogens (bacteria, viruses) How does it remove Different size meshes which work together to trap particles. Particle sizes are measured in microns, which are very small units. For a comparison of micron sizes check this comparison below: The diagram below illustrates how the size of the openings in a mesh serve to trap the particles. It also shows that thinner openings can mean a lower flow rate. Because of this, it is recommended to use several mesh filters, starting with a wider one and working your way to a thinner one to avoid blocking the mesh. Activated carbon is used to trap and adsorb organic particles within the water. Some of the things that we want to remove from water at this stage are: chlorine, pesticides, hydrogen sulfide, and others. These chemicals and natural compounds are some of the things that can give water weird tastes and smells! Uses chemicals like chlorine, specially treated filters or UV light to kill pathogens in water. Example Any type of mesh that removes particles and debris from water can be a first stage filter. Whenever you are trying to filter out very small particles, we can use pleated filters. These will vary depending on the size of particle you want to filter out (given in microns). For this stage of filtering, any activated carbon or activated charcoal filter can be used. There are even specially treated filters that kill bacteria! However, if the label does not specify that it kills viruses and bacteria, then the filter only removes organic compounds. Chlorine is most commonly used in this stage of filtering, in very small amounts. However if you want to avoid chemicals, you can use UV filters, specially treated activated carbon filters or even heat!

In an emergency, we might not have access to all the resources required for all of these stages of filtering. In this case, the priority is making sure that we can get water that has the least amount of solids and pathogens as possible. In these cases filtering might look like something more similar to this:

Stage First Second What does it remove Particles and solids Pathogens (bacteria and viruses) Description/example In the case of an emergency, you can filter the water through a cotton mesh (like a t-shirt) to capture most sediments. During the emergency, we can employ DIY home methods to minimize the risk of ingesting pathogens. This guide from the EPA describes different home methods that you can use to disinfect water.

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