Filtering Polluted Water: Does It Remove Germs?

Water filtration is an increasingly common practice due to deteriorating water quality from aging infrastructure, the growing threat of pollution from industrialization and urbanization, and increasing awareness about waterborne diseases. While filtering polluted water can purify it, it does not always remove germs. The presence of germs in drinking water is a leading cause of disease outbreaks, and there are only a few ways to remove them. Water filters certified to NSF/ANSI 244 or P231 standards can effectively remove bacteria, as can distillation and UltraViolet water treatment systems (certified to NSF-55 standards). Boiling, iodine, and chlorine addition can also remove some bacteria. Slow sand and membrane filters can remove nearly all tiny pollutants, including microplastics, and are more effective than ozonation or activated carbon filtration. However, most home water filters are not designed to remove germs, and some filters can even promote microbial growth in plumbing. Therefore, it is essential to test water for harmful germs and choose a filter that removes them.

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Water filters certified to NSF/ANSI 244 or P231 standards can remove bacteria

Water filters are essential in ensuring that drinking water is safe for human consumption. While there are many sources of water contamination, there are only a few ways to remove the bacteria from water.

Water filters certified to NSF/ANSI 244 standards can remove bacteria. This certification is one of the most uncommon of all. Filters with this certification are able to protect against intermittent bacteria and virus contamination. Manufacturers of these types of filters can claim bacteria, viruses, and cysts reduction for their products.

NSF/ANSI P231 is another standard that water filters can be certified under to remove bacteria. This standard applies to drinking water purifiers that offer microbiological contaminant reduction. Companies that apply for this certification need to allow their products to undergo rigorous testing by the NSF to prove they are capable of converting a microbiologically compromised water source into clean, purified drinking water. P231 filters are verified as microbiological purifiers in accordance with guidelines from the EPA.

Other NSF/ANSI standards that water filters can be certified under to remove bacteria include standard 53, which covers the reduction of specific health-related contaminants, and standard 55, which applies to filters that use a UV light system to kill or deactivate bacteria, viruses, and cysts.

In addition to these standards, NSF/ANSI 42 certifies filters to reduce aesthetic impurities such as chlorine, taste, and odor, while NSF/ANSI 62 applies to drinking water distiller systems that have been proven to remove specific microbiological and chemical contaminants, including bacteria.

It is important to note that not all water filters and purifiers are effective at removing bacteria from water. Some methods that can remove some, but not all, bacteria include boiling, iodine, and chlorine addition.

Distillation and UltraViolet water treatment systems can kill bacteria

Distillation and UltraViolet (UV) water treatment systems are effective methods for killing bacteria in water. Distillation units heat water to boiling, killing most bacteria and viruses. The water is heated to form steam, which rises and leaves impurities behind. The steam then cools and condenses into purified water, which is stored in a tank. Distillation removes over 99.9% of dissolved materials, including heavy metals, dissolved solids, and inorganic materials such as nitrate, sodium, fluoride, and sulfate. However, distillation is ineffective against most volatile and semi-volatile organic compounds and may not remove all bacteria. Distillation units are generally installed as point-of-use systems at the faucet and require regular maintenance to flush out unevaporated pollutants and mineral buildup. They are also more expensive to operate due to the energy required for heating.

UV light disinfection systems are another effective method for killing bacteria in water. These systems use UV light to disinfect water at the point of contact, but recontamination can occur after the water leaves the system. Well-designed UV treatment systems locate the UV light disinfection process as close to the point of use as possible to minimize the risk of recontamination. UV light tubes and lamps require regular replacement, and the system as a whole needs maintenance to remove algae and other deposits. All UV light disinfection systems sold in Australia are required to carry a standard WaterMark symbol, indicating their effectiveness in killing bacteria.

Boiling, iodine and chlorine addition can remove some bacteria

Boiling water is a well-known method for removing bacteria and other microbes. Sources suggest that water should be boiled for at least one minute to ensure bacteria are killed. Boiling is not suitable for water with high levels of contamination, such as raw sewage, as particulate matter can impair boiling's effectiveness. In such cases, alternative water sources must be used.

Iodine can also be used to purify water and remove bacteria. It is often used in survival situations, and can also be used as a disinfectant for wounds. Iodine is toxic in large doses, but in small amounts, it is required for the body to function properly. Filtering water before adding iodine is ideal, as pathogens tend to cling to large particles, making the iodine more effective.

Chlorine is the most common type of drinking water disinfection. It is used in 98% of treated water supply systems in the US. When added to water, chlorine reacts with it to form hypochlorous acid, which penetrates the cell walls of microbes and collapses proteins in bacterial cells, killing them. Chlorine is also effective at killing viruses, although the method by which it does so is less understood. Chlorine can take up to 15 minutes to kill some viruses, so it is best used in water supplies or pools where it can sit.

Reverse osmosis systems can deliver purified water

Reverse osmosis (RO) systems are a popular choice for those seeking additional water purification. They are considered one of the most effective ways of eliminating water contaminants, including dissolved solids and other impurities. RO systems work by forcing water through a semi-permeable membrane with tiny pores, typically measuring about 0.0001 microns. This membrane allows only water molecules to pass through while blocking and removing dissolved salts, chemicals, microorganisms, and other pollutants. The result is clean, high-quality water that can be used for various purposes, such as cooking or in aquariums.

While RO systems are effective in removing a wide range of contaminants, they may not be as successful in eliminating all bacteria and viruses. However, some RO systems are now being combined with UltraViolet (UV) sterilisers to address this issue. The UV component kills bacteria, ensuring that the water is safe for consumption. Additionally, certain brands of water filter pitchers use silver technology and extremely small pore sizes to remove and inhibit bacterial growth.

One of the main advantages of RO systems is their ability to maximise water efficiency. They are designed to minimise wastewater, making them more sustainable than other filtration methods. While the initial investment in an RO system can be significant, it can save money in the long run compared to buying bottled water. Additionally, RO systems protect appliances such as refrigerators and coffee makers from damage caused by mineral deposits.

However, RO systems also have some disadvantages. They are known for their high water usage, with most systems wasting about four gallons of water for every gallon produced. They also have higher installation and maintenance costs, making them more suitable for those who require extremely purified water for specific uses or who do not have access to any fresh water. Despite these drawbacks, RO systems remain a popular choice for water purification due to their effectiveness and ability to provide high-quality water.

Slow sand and membrane filters can remove pollutants

Slow sand filters (SSFs) are one of the oldest municipal drinking water treatment systems. They are ideal for low-resource regions, especially in rural areas, as they are easy to operate and can be constructed locally. SSFs improve water quality by removing suspended particles, dissolved organic chemicals, and other contaminants, effectively reducing turbidity and associated taste and odour problems. The removal of turbidity and dissolved organic compounds from the water enables the use of low-cost disinfection methods, such as chlorination.

The performance of slow sand filters can be quantified by several measurable parameters, including the reduction in water turbidity, water colour, total organic carbon (TOC) concentration, pathogen concentration, and specific organic chemical pollutant concentrations of regional concern. The key design parameter controlling the effluent water quality is the hydraulic residence time (HRT), which is influenced by the flow rate, total volume of sand, and sand porosity. The porosity of sand is generally in the range of 0.35 to 0.5, and the sand should be of reasonably uniform size to maintain a high porosity.

Membrane filtration systems are another effective method for removing pollutants from water. These systems use synthetic polymer membranes to physically separate or strain substances from water, such as sand or algae. Membrane filtration has been shown to be highly effective in removing micro- and nano-plastic particles from wastewater, with a 2021 study finding 100% efficiency in both laboratory and real-scale filtration results. Membrane filtration is expected to outperform slow sand filtration in terms of retaining micro- and nano-plastic particles.

While slow sand filters and membrane filters can remove various pollutants, it is important to note that they may not effectively remove all types of bacteria. Water filters certified to NSF/ANSI 244 or P231 standards, distillation, and UltraViolet water treatment systems (certified to NSF-55 standards) are effective at removing bacteria. Additionally, boiling water and adding iodine or chlorine can remove some, but not all, bacteria.

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