Once we have established what may be in the water (and we are only talking about drinking water), let's see how this applies to our water so we can make a strategy to remove the challenges, and have clear clean and safe water at all taps in the house.
Refresh - the water can have insoluble or solid contaminants (1), dissolved chemicals (2) or organics (3), biological contaminants or pathogens (4) and radiological contaminants (5).
1. Solid Contaminants
These occur only in water from surface sources or wells. City water typically does not contain solids.
Solid, insoluble substances or sediments are small impurities like sand, rust, dirt, silt or scale.
They are generally not harmful for human health but can be considered an aesthetic contaminant and are physically filtered out.
2.1 Generally Harmless Dissolved Chemical Contaminants
Soluble chemical substances can be present in all water for drinking (city water, well water, surface water) in various concentrations. They come in form of molecules and formulas and can not be filtered out with physical filtration methods.
There are harmless chemicals and minerals (calcium, magnesium, potassium, sodium), harmless heavy metals (iron, manganese), and harmless gases (hydrogen sulfide), they show up as scale or precipitation, colourization or they impart odour. These can be removed for aesthetic reasons.
2.2 Harmful Dissolved Chemical Contaminants
There are harmful chemicals and heavy metals (arsenic, lead, copper, cadmium, antimony, mercury, fluoride) and harmful gases (carbon dioxide, radon). “Forever chemicals” Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are part of a large group of man-made chemicals known as perfluoroalkyl and polyfluoroalkyl substances (PFAS).
These chemicals need to be removed for safety resons if the concentration is above the MCL (Maximum Concentration Level) set by the EPA.
3. Organic Contaminants
Organic Contaminants are substances containing carbon and hydrogen. They are dissolved and appear as chemical compounds. Some are naturally occurring, others are man-made, and there can be a combination of both.
Organic chemicals reach the water supply from industrial and agricultural runoff, from improper disposal of household products (paint and cleaning products), or domestic animals.
They include pesticides, herbicides, solvents, petroleum-derived products, and many other types of compounds.
There are two main categories of organic contaminants: Total Organic Carbon (TOCs) and Volatile Organic Compounds (VOCs).
TOCs are all-organic carbon compounds including decaying plant and animal matter. High TOC levels may be found in some surface water supplies (streams, rivers, lakes, reservoirs)
VOCs are contaminants like solvents, hydrocarbons, alcohols and other industrial compounds (eg. Benzene, Trichlorethylene, Vinyl chloride, Styrene, Tetrachlorethylene.)
3.1 Not Harmful Organics
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Decaying plant matter shows up in the water as tannins and lignins, they are seasonal and climate dependent. These are generally not a health hazard, even in higher concentrations, but are an aesthetical problem, they have staining quality and can have an effect on the taste and smell of the water. Tannins are easily removed from drinking water. |
3.2 Harmful Organics |
There can be harmful chemical compounds or byproducts of chemical reactions and traces of industrial processes in the water supply (solvents, cleaning agents, paint removers, chemical extractors, adhesive components), resulting in toxic pollution. Trace amounts of pharmaceuticals may be present in some cases, they accumulate in the water over time. Pesticides, herbicides and insecticides are organics from runoff that can contaminate the water supply. |
4. Pathogens / Biological Contaminants
Biological contaminants are any organisms that are in the water, they can be bacteria, parasites, protists, viruses or fungi. Bacteria and viruses are everywhere in our environment, including in surface waters and groundwater. They are microbial, so they will not be caught in a filter.
Typically they are harmful, especially in high concentrations, so they need to be removed from drinking water to make it safe.
4.1 Bacteria
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Bacteria that can be present in drinking water are Bacillus anthracis, Campylobacter jejuni, Cyanobacteria, Escherichia coli, Legionella, Listeria, Pseudomonas aeruginosa, Salmonella enteritidis, Shigella dysenteriae, Vibrio cholerae and many more. It is not practical to test drinking water for every type of pathogen, but it is simple to test drinking water for coliform bacteria. The presence of coliform bacteria can indicate there may be harmful pathogens in the water. |
4.2 Pathogenic Protists and Parasites
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Some severe diseases of humans are caused by protists and parasites in drinking water (protists are primarily blood parasites): Malaria, Trypanosomiasis, Leishmaniasis, Toxoplasmosis, Amoebic dysentery. Cryptosporidium parvum, Giardia lamblia, Acanthamoeba spp. (cysts), Chlorella vulgaris, Naegleria fowleri (cysts), Paramecium spp, Toxoplasma gondii are pathogenic protists. |
4.3 Viruses and Fungi
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Microbiologically contaminated drinking water can transmit viral diseases such as diarrhoea, cholera, hepatitis, typhoid and polio. Pathogenic viruses in water can be Coxsackie, Enterovirus, Norovirus, Rotavirus, Adenovirus, Hepatovirus, Hepevirus. Pathogenic fungi are Candida albicans, Candida parapsilosis, Aspergillus, Fusarium, Exophiala dermatitidis, microsporidia. Biofilms are an important habitat for fungi in drinking water. Their development is influenced by many factors including temperature, nutrient concentration, pipe material and water flow rate. |
