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Purification

Drinking Water Treatment Technologies for Household Use

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Filtration

  • Filtration is a physical process that occurs when liquids, gases, dissolved or suspended matter adhere to the surface of, or in the pores of, an absorbent medium.
  • Filtration of contaminants depends highly on the amount of contaminant, size of the contaminant particle, and the charge of the contaminant particle. Depending on the household’s water needs, pretreatment before filtration may include the addition of coagulants and powdered activated carbon, adjustments in pH or chlorine concentration levels, and other pretreatment processes in order to protect the filter’s membrane surface.

Microfiltration

  • A microfiltration filter has a pore size of approximately 0.1 micron (pore size ranges vary by filter from 0.05 micron to 5 micron);
  • Microfiltration has a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);
  • Microfiltration has a moderate effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli);
  • Microfiltration is not effective in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);
  • Microfiltration is not effective in removing chemicals.

Ultrafiltration

  • An ultrafiltration filter has a pore size of approximately 0.01 micron (pore size ranges vary by filter from 0.001 micron to 0.05 micron; Molecular Weight Cut Off (MWCO) of 13,000 to 200,000 Daltons). Ultrafiltration filters remove particles based on size, weight, and charge;
  • Ultrafiltration has a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);
  • Ultrafiltration has a very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli);
  • Ultrafiltration has a moderate effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);
  • Ultrafiltration has a low effectiveness in removing chemicals.

Nanofiltration

  • A nanofiltration filter has a pore size of approximately 0.001 micron (pore size ranges vary by filter from 0.008 micron to 0.01 micron; Molecular Weight Cut Off (MWCO) of 200 to 2000 Daltons); Nanofiltration filters remove particles based on size, weight, and charge;
  • Nanofiltration has a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);
  • Nanofiltration has a very high effectiveness in removing bacteria (for example,
    Campylobacter, Salmonella, Shigella, E. coli);
  • Nanofiltration has a very high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);
  • Nanofiltration has a moderate effectiveness in removing chemicals.

Reverse Osmosis Systems

  • Reverse Osmosis Systems use a process that reverses the flow of water in a natural process of osmosis so that water passes from a more concentrated solution to a more dilute solution through a semi-permeable membrane. Pre- and post-filters are often incorporated along with the reverse osmosis membrane itself.
  • A reverse osmosis filter has a pore size of approximately 0.0001 micron.
  • Reverse Osmosis Systems have a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);
  • Reverse Osmosis Systems have a very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli);
  • Reverse Osmosis Systems have a very high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);
  • Reverse Osmosis Systems will remove common chemical contaminants (metal ions, aqueous salts), including sodium, chloride, copper, chromium, and lead; may reduce arsenic, fluoride, radium, sulfate, calcium, magnesium, potassium, nitrate, and phosphorous.

Distillation Systems

  • Distillation Systems use a process of heating water to the boiling point and then collecting the water vapor as it condenses, leaving many of the contaminants behind.
  • Distillation Systems have a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);
  • Distillation Systems have a very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli);
  • Distillation Systems have a very high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);
  • Distillation Systems will remove common chemical contaminants, including arsenic, barium, cadmium, chromium, lead, nitrate, sodium, sulfate, and many organic chemicals.

Ultraviolet Treatment Systems (with pre-filtration)

  • Ultraviolet Treatment with pre-filtration is a treatment process that uses ultraviolet light to disinfect water or reduce the amount of bacteria present.
  • Ultraviolet Treatment Systems have a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);
  • Ultraviolet Treatment Systems have a very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli);
  • Ultraviolet Treatment Systems have a high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);
  • Ultraviolet Treatment Systems are not effective in removing chemicals.

Water Softeners

  • Water Softeners use ion exchange technology for chemical or ion removal to reduce the amount of hardness (calcium, magnesium) in the water; they can also be designed to remove iron and manganese, heavy metals, some radioactivity, nitrates, arsenic, chromium, selenium, and sulfate. They do not protect against protozoa, bacteria, and viruses.

Please remember

  • Point of Use (POU) water treatment systems typically treat water in batches and deliver water to a single tap, such as a kitchen sink faucet or an auxiliary faucet.
  • Point of Entry (POE) water treatment systems typically treat most of the water entering a residence. Point of entry systems, or whole-house systems, are usually installed after the water meter.
  • The treatment technologies described can be used in conjunction with each other for greater pathogen reduction. The addition of coagulants, carbon, alum, and iron salts to filtration systems may aid in chemical removal from water.

Coliform Bacteria in Drinking Water Supplies

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What are Coliforms?

Coliforms are bacteria that are always present in the digestive tracts of animals, including humans, and are found in their wastes. They are also found in plant and soil material.

 

“Indicator” Organisms

 

Water pollution caused by fecal contamination is a serious problem due to the potential for contracting diseases from pathogens (diseasecausing organisms). Frequently, concentrations of pathogens from fecal contamination are small, and the number of different possible pathogens is large. As a result, it is not practical to test for pathogens in every water sample collected. Instead, the presence of pathogens is determined with indirect evidence by testing for an “indicator”organism such as coliform bacteria. Coliforms come from the same sources as pathogenic organisms. Coliforms are relatively easy to identify, are usually present in larger numbers than more dangerous pathogens, and respond to the environment, wastewater treatment, and water treatment similarly to many pathogens. As a result, testing for coliform bacteria can be a reasonable indication of whether other pathogenic bacteria are present.

Total Coliforms, Fecal Coliforms, and E. Coli

The most basic test for bacterial contamination of a water supply is the test for total coliform bacteria. Total coliform counts give a general indication of the sanitary condition of a water supply.

 

A. Total coliforms include bacteria that are found in the soil, in water that has been influenced by surface water, and in human or animal waste.

 

B. Fecal coliforms are the group of the total coliforms that are considered to be present specifically in the gut and feces of warm-blooded animals. Because the origins of fecal
coliforms are more specific than the origins of the more general total coliform group of bacteria, fecal coliforms are considered a more accurate indication of animal or human waste than the total coliforms.

 

C. Escherichia coli (E. coli) is the major species in the fecal coliform group. Of the five general groups of bacteria that comprise the total coliforms, only E. coli is generally not found growing and reproducing in the environment.

 

Consequently, E. coli is considered to be the species of coliform bacteria that is the best indicator of fecal pollution and the possible presence of pathogens.

Are Coliform Bacteria Harmful?

Most coliform bacteria do not cause disease. However, some rare strains of E. coli, particularly the strain 0157:H7, can cause serious illness. Recent outbreaks of disease caused by E. coli 0157:H7 have generated much public concern about this organism. E. coli 0157:H7 has been found in cattle, chickens, pigs, and sheep. Most of the reported human cases have been due to eating under cooked hamburger. Cases of E. coli 0157:H7 caused by contaminated drinking water supplies are rare.

Coliform Testing

  • Testing for bacteria is the only reliable way to know if your water is safe. You cannot tell by the look, taste, or smell of the water if disease-causing organisms are in it. The New York State Department of Health recommends that well owners test their water for coliform bacteria at least once a year. If you have experienced bacteria problems in the past, it is recommended that you test your well more frequently.

When Should I Test?

  • Late spring or early summer are the best times to test your well, since coliform contamination is most likely to show up during wet weather. Whether your test results are positive or negative, understand that the sample you collected is just a “snapshot” of your well’s water quality. The more samples you have tested, the more confident you can be about the quality of the water you are drinking.

What do the Results Mean?

  • If coliform bacteria are present in your drinking water, your risk of contracting a water-borne illness is increased. Although total coliforms can come from sources other than fecal matter, a positive total coliform sample should be considered an indication of pollution in your well. Positive fecal coliform results, especially positive E. Coli results, should be considered indication of fecal pollution in your well.

What Should be done if Coliform Bacteria are Detected in a Well?

  • When coliforms have been detected, repairs or modifications of the water system may be required. Boiling the water is advised until disinfection and retesting can confirm that contamination has been eliminated. A defective well is often the cause when coliform bacteria are found in well water.

What Kinds of Defects can Allow Contamination?

  • a missing or defective well cap – seals around wires, pipes, and where the cap meets the casing may be cracked, letting in contaminants
  • contaminant seepage through the well casing – cracks or holes in the well casing allow water that has not been filtered through the soil to enter the well. This seepage is common in the wells made of concrete, clay tile, or brick
  • contaminant seeping along the outside of the well casing – many older wells were not sealed with grout when they were constructed
  • well flooding – a common problem for wellheads located below the ground in frost pits that frequently flood during wet weather.

Long-Term Options for Dealing with Bacterial Contamination of a Well

  • Connecting to the regional public water system, if possible
  • Inspecting wells for defects and repairing them if possible
  • Constructing a new well.
  • Installing continuous disinfection equipment
  • Using bottled water for drinking and food preparation

The following problems can be identified

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Chlorine Taste

Chlorine, a powerful oxidiser, is commonly used to sterilise municipal drinking water and water in storage tanks. The chlorine is added to kill most germs and pathogens that could be harmful to us, however, this spoils the taste and smell of your water. Overdosing of chlorine make your water smell and taste even worse at times.In the long run, the consumption of chlorine can be damaging to your health and Disinfectant by-products of Chlorine are Carcinogenic. Chlorine is effective in killing germs and bacteria, but should be removed from the water before consumption.

Bacteria

The presence of bacteria in water is a common problem; sources of contamination can include: contaminated ground water; exposed infrastructure (e.g. burst pipes or open storage tanks) or when water is collected from open or exposed areas e.g. roofs for rainwater harvesting.If you suspect your water source to be contaminated indicated by illness in the household you should request a water test report. When requesting a water test report to determine the pathogen (including bacteria, spores, viruses etc.) content of the water; specifically request a micro biological report.

Hard Water / Lime Scale

We call water “hard” when it contains high quantities of calcium and magnesium.Hard water is not harmful when consumed, but it causes damage to household appliances.It causes “scale” to form on the inside of pipes and especially on heating elements. The scale does not conduct heat very well, causing the heating elements to use more electricity then would normally be required. Scale also reduces the flow through pipes and eventually, pipes
can become clogged. It also poses a nuisance in personal hygiene by preventing soap from lathering.Hardness is measured in ppm (parts per million); mg/l (milligrams per litre), mg/l and ppm are considered equal.

Hard water levels are classified as follows (Total hardness):

  • Soft: 0 – 50 ppm
  • Moderately Soft: 50 – 100 ppm
  • Slightly Hard: 100-150 ppm
  • Moderately Hard: 150 – 200 ppm
  • Hard: 200 – 300 ppm
  • Very Hard: more than 300 ppm

Sediment

Sediment is a general term for all sand, organic material and other small solid particles suspended in your water. This is caused when infrastructure gets older, as well as when maintenance is done. Dam, river and bore-hole water can also have high levels of sediment.Sediment in your water is abrasive and can cause damage to your appliances that work with water such as: washing machines, dishwashers, taps, geysers etc. Sediment also damages and clogs up irrigation systems.Sediment never travels alone, but is accompanied by dissolved components. The visible particles are not always harmful to your health, but some of the dissolved components such as heavy metals can be harmful. These solid particles can be removed by means of a mechanical process; either sifting or creating a barrier.Sediment removal is always the primary stage in a filtration process.

Salt / Brackish Water

Brackish water is water with a high salt content (high TDS). To turn brackish water into fresh drinking water, the process of reverse osmosis is used.

Iron and Metals

Iron is one of the most common elements found in nature and in some areas the ground water contain a measurable amount. Iron stains bathtubs, toilets, sinks and walls etc. with a characteristic reddish-brown colour. Staining will occur even at low concentrations.High levels of Iron in your drinking water is unhealthy in the long run. Iron-rich water is characterised by a metallic taste and a metallic or sulphurous smell and the water is a reddish-brown colour.When taking a water sample of iron-rich water ensure that there no air is present in the sample bottle.