Bacteria-Killing Methods For Water Purification

Bacteria are everywhere in our environment, including surface waters and groundwater. While some bacteria are harmless, others can be harmful to human health. The presence of pathogenic bacteria in water can cause diseases such as cholera, typhoid fever, bacillary dysentery, and diarrhea. Therefore, it is essential to ensure that drinking water is free from harmful bacteria. The detection and removal of pathogenic bacteria from water is a complex process due to their sporadic and erratic occurrence and the challenges in isolating and culturing these bacteria. However, various methods and technologies are employed to address water pollution caused by bacteria, and in some cases, bacteria themselves can be used to break down dangerous chemicals and pollutants in water.

Characteristics and Values of Methods to Kill Bacteria in Water Pollution

Indicator organisms, such as E. coli, are used to assess pathogen levels in water

Indicator organisms are used to assess the levels of pathogens in water. This is because it is not practical to test drinking water for every type of pathogen, but it is simple to test for indicator organisms. The presence of these indicator organisms suggests that there may be harmful pathogens in the water.

The most common indicator organisms are total coliforms, faecal coliforms, and E. coli. These are all types of bacteria that are present in human and animal faeces. They are used to evaluate the level of faecal contamination in water environments and to assess the pathogen removal efficiency of water treatment plants. The presence of these bacteria indicates that there may be harmful pathogens in the water that can cause diseases such as cholera, typhoid fever, and bacillary dysentery.

The use of indicator organisms to assess pathogen levels in water is based on the concept of "fecal indicator bacteria". These are bacteria that are present in high numbers in the human intestine and faeces, are easily detectable in water, and are not pathogenic to humans. The ideal indicator organism should be present in greater numbers than the associated pathogen and have a similar survival rate.

While the use of indicator organisms is a common approach for quantifying potential pathogen loads in water, there is debate about their ability to represent the potential presence of pathogenic bacteria accurately. Studies have shown that there is a poor correlation between traditional indicators of faecal contamination and certain pathogens, such as H. pylori. Additionally, there may be pathogens present in water even when indicator organisms are absent, and vice versa.

Despite these limitations, the use of indicator organisms remains an important tool for assessing water quality and public health officials continue to rely on them to evaluate water safety.

Bacterial indicators of faecal pollution should be harmless to humans

Bacterial indicators of faecal pollution, or FIBs, have been used for over 150 years to indicate faecal contamination of water and the associated health risks. FIBs are a group of typically harmless Gram-negative bacteria that constitute part of the natural gut microbiota in humans and other warm-blooded animals. They are valuable investigative tools to identify faecal pollution and are detectable in the host intestine, faeces, and faecal-polluted environmental waters.

FIBs are a simple and reasonably reliable tool for diagnosing sewage pollution in drinking water samples due to their high concentrations in sewage and ease of culture. They are also important because they allow for the detection of unknown waterborne pathogens that would be overlooked if only known pathogens were monitored.

A good bacterial indicator of faecal pollution should fulfil the following criteria:

• Exist in high numbers in the human intestine and faeces
• Not be pathogenic to humans
• Easily, reliably, and cheaply detectable in environmental waters
• Not multiply outside the enteric environment
• Exist in greater numbers than eventual pathogenic bacteria
• Have a similar die-off behaviour as the pathogens
• Not be very common in the intestine of farm and domestic animals if human faecal pollution is to be separated from animal pollution

Despite the usefulness of FIBs, there are some limitations to their use. For example, FIBs lack host specificity, which is a problem when determining the specific source of faecal pollution. Additionally, FIBs have imperfect sensitivity and specificity, and the detection of some waterborne pathogens can be labour-intensive, time-consuming, and require specialized expertise and biosafe laboratory settings.

To address these limitations, alternative fecal microbes have been proposed, such as coliphages, viruses that infect E. coli bacteria, and obligate anaerobes, which are thought to have host specificity and to derive exclusively from recent faecal contamination. These alternative indicators are expected to better represent the risks to human health.

Perchlorate-decontaminating bioreactors use bacteria to break down dangerous chemicals in water

Perchlorate is a chemical that comes from rocket fuel, munitions, fireworks, and certain fertilizers and potash ores. It is dangerous to humans as it can impair thyroid function by inhibiting the uptake of iodine. Perchlorate is water-soluble and chemically stable, so it can persist in groundwater and surface water for decades.

Perchlorate-decontaminating bioreactors are an innovative solution to this problem. These bioreactors are large tanks that provide the ideal environment for perchlorate-destroying bacteria to break down perchlorate into harmless chloride and oxygen. The contaminated water is pumped into these bioreactors, which are full of bacteria with the right nutrients and minerals to thrive. Once the bacteria have broken down the perchlorate, the water is filtered and sterilized to remove the bacteria. The decontaminated water can then be consumed or pumped back into the ground.

These bioreactors are highly efficient; for example, a bioreactor-based groundwater treatment plant in Rialto, California, can decontaminate 2,000 gallons (over 7,500 liters) of perchlorate-polluted water per minute, amounting to more than a billion gallons per year. Perchlorate-decontaminating bioreactors have been successfully implemented in California, Kansas, Texas, and Utah.

In addition to perchlorate, bioreactors can also remove other contaminants from water, such as trichloroethene, uranium, and other metals. One such bioreactor, designed by Bruce Rittmann, can address a range of water pollutants.

The use of bacteria in bioreactors is a promising approach to tackling water contamination. While challenges exist, such as creating the right conditions for bacteria to survive, the potential for using bacteria to break down harmful chemicals in water is significant.

Escherichia coli is the indicator of faecal contamination in water

Bacteria are everywhere in our environment, including in surface waters and groundwater. While some of these bacteria are harmless, others can be harmful to human health. Drinking water contaminated with disease-causing bacteria, viruses, or parasites (collectively called pathogens) can make you sick.

One of the most important bacterial diseases transmitted through water is cholera, which can cause severe diarrhoea, vomiting, and nausea. To prevent such waterborne diseases, it is essential to monitor the microbiological quality of drinking water. This is typically done by testing for the presence of indicator bacteria, such as Escherichia coli (E. coli), which indicates faecal contamination.

E. coli is a type of coliform bacteria that is commonly found in the human gastrointestinal tract and is a specific indicator of faecal pollution. It is not pathogenic to humans and can be easily, reliably, and cheaply detected in water. The presence of E. coli in drinking water suggests that the water may be contaminated with harmful pathogens. Therefore, the U.S. Environmental Protection Agency (EPA) requires public water systems to regularly test for E. coli and issue public notices if it is detected.

The use of E. coli as an indicator of faecal contamination is supported by various studies. For example, a study in rural Kitui County, Kenya, used whole genome sequencing to investigate the links between E. coli and recent faecal contamination in drinking water. The results contributed to the understanding of non-clinical E. coli populations and provided insights into the occurrence of E. coli in drinking water supplies and household storage.

However, there are some uncertainties and challenges associated with using E. coli as a faecal indicator. For instance, it is difficult to determine the health hazards associated with changes in E. coli concentration between points of collection and points of use. Additionally, the presence of E. coli in the environment, unrelated to faecal contamination, has been observed, raising questions about its specificity as an indicator. Nonetheless, E. coli currently appears to be the best bacterial indicator of faecal contamination in drinking water due to its prevalence in human and animal faeces and the availability of affordable and sensitive detection methods.

Bacterial water pollution is caused by effluent from hospitals, industry, and cattle farms

Bacterial water pollution is a severe issue, and effluents from hospitals, industries, and cattle farms are significant contributors. These sources introduce harmful bacteria and other contaminants into water bodies, posing risks to both environmental and human health.

Hospitals generate large volumes of liquid waste, or effluents, that contain various hazardous pollutants. These include pharmaceutical residues, chemical substances, radioisotopes, and microbial pathogens. The untreated discharge of hospital effluents can lead to the development of antibiotic-resistant bacteria and the transmission of water-related diseases, especially in developing countries. The high organic matter charges and the presence of disinfectants, drugs, bacteria, viruses, and parasites in hospital effluents further exacerbate the problem.

Industries and commercial activities also contribute to bacterial water pollution through the release of untreated wastewater. This wastewater contains metals, solvents, toxic sludge, and other chemical pollutants such as arsenic, mercury, and pesticides. These substances can contaminate water sources, leading to health issues in humans, including skin rashes, respiratory infections, and even cancer.

Cattle farms, particularly dairy farms, are another major source of bacterial water pollution. Cattle produce large amounts of manure and urine, which often end up as untreated fertilizer on fields. This waste contains bacteria, excess nitrates, and nutrients that seep into groundwater, threatening the drinking water sources for millions of people. Additionally, the dairy industry's use of pesticides and insecticides further contributes to water pollution, as these toxic substances leach into water sources, harming ecosystems and the general public.

The combined impact of effluents from hospitals, industries, and cattle farms on water pollution is significant. The discharge of untreated or improperly treated waste allows bacteria and other contaminants to enter water bodies, leading to ecological damage and severe health consequences for humans and other organisms. It is crucial to address these sources of pollution through proper waste treatment, regulation, and sustainable practices to protect water quality and safeguard public health.

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