Water Contamination: Pollutants Altering Taste And Odor

Water that is aesthetically unacceptable can lead to consumer complaints and a loss of confidence in the water supply. While consumers have no means of judging the safety of their drinking water, their attitude towards their drinking water supply and suppliers will be affected by the aspects of water quality that they can perceive with their senses. Many contaminants are found in water supplies, and some of the major organic causes of taste and odour issues are methyl isoborneol and geosmin, which are often associated with algal blooms. Other causes include high concentrations of dissolved solids, which can make water taste salty, and high levels of manganese and iron, which can cause black or brownish-red stains, respectively, and an unpleasant taste.

Dissolved iron in groundwater can cause an unpleasant taste

Iron in water generally comes in two forms: ferrous iron, which is soluble in water, and ferric iron, which is not. Water containing ferrous iron is typically visually indistinguishable from pure water because the iron dissolves evenly, and the water remains clear. However, when the water reaches a home pressure tank or is exposed to air, the iron becomes oxidized and turns into the insoluble ferric form. It then becomes visible and begins to affect water quality.

The presence of iron in water can have several noticeable effects on its appearance, smell, and taste. Iron concentrations as low as 0.3 mg/L can cause water to turn a reddish-brown color and leave stains on fixtures, tableware, and laundry that are challenging to remove. When exposed to air, the oxidized iron precipitates out, and the water turns cloudy. This oxidized iron can also give the water a metallic taste and smell, making it unpleasant or even undrinkable for some.

Additionally, iron can affect how food and beverages prepared with iron-rich water taste. For example, when combined with tea, coffee, or other beverages, iron produces an inky black appearance and a harsh, unacceptable taste. Vegetables cooked in water containing excessive iron turn dark and look unappetizing.

While iron in water is not usually a direct health risk, it can be a concern if harmful bacteria are present. Certain harmful organisms require iron to grow, and the presence of iron may make it more challenging to eliminate these bacteria. In some cases, the combination of iron and specific bacteria can form a smelly biofilm, resulting in an offensive odor.

To address the issue of dissolved iron in groundwater, several treatment methods can be considered. One option is to construct a new water well, extending the "well casing" or "screen" deeper into the groundwater to access water with lower iron levels. Another alternative is to use Manganese Greensand, a naturally occurring mineral or manufactured material capable of absorbing dissolved iron through chemical regeneration. Catalytic filtration is also an option, as it enhances the reaction between oxygen and iron before filtering the insoluble iron.

Salty taste caused by chloride ions and/or sulfates

Salty-tasting water is often caused by the presence of chloride ions and/or sulfates in the water supply. While the salty taste of water is usually unpleasant, it is not typically hazardous to humans. However, in some cases, it can cause diarrhea.

Chloride ions are one of the two components of table salt, the other being sodium ions. When salt is dissolved in water, it dissociates into these two ions. The salty taste of water is perceived when the taste receptors on the tongue are activated by the sodium and chloride ions. Interestingly, studies have shown that minuscule amounts of salt can be perceived as sweet by some individuals. This may be because the chloride half of salt drives the sweet taste.

The presence of chloride ions in water can be attributed to various factors. Firstly, industrial processes that utilise calcium, potassium, and sodium chlorides can lead to the presence of chloride ions in the water supply through surface runoff or weathering. Additionally, seawater entering local reservoirs can introduce chloride ions into the water supply.

Sulfates, such as magnesium sulfate and sodium sulfate, can also cause water to taste salty. These sulfates may occur naturally in certain types of soil and rocks. As groundwater or rainwater moves through the earth, these sulfates can dissolve and make their way into the local water supply. This is particularly common during winter when melting snow and rain carry road salt runoff into reservoirs.

While the salty taste of water due to the presence of chloride ions and/or sulfates is generally not a health concern, it can indicate the presence of other harmful contaminants. For example, high levels of dissolved solids, which contribute to the salty taste, can signal elevated concentrations of arsenic, uranium, or other trace elements in the groundwater. Therefore, it is recommended to test the water to determine the specific contaminants and take appropriate steps to address the issue.

Sweet taste caused by high calcium or iron concentration

While water tasting sweet may not always be a cause for concern, it could indicate high concentrations of certain minerals or contaminants.

Calcium and Iron

Calcium and iron are two common minerals that can cause water to taste sweet. While calcium is generally harmless, iron can cause issues like stained laundry or sinks, and clogged water-using appliances.

Calcium can contribute to hard water, which can cause issues like stiff laundry, dry skin and hair, and mineral buildup on faucets. Iron, on the other hand, can have an unpleasant taste, making it undrinkable for some. It can also cause corrosion and leaching of rust flakes into the water, which can be a sign of contaminated water.

Other Causes of Sweet-Tasting Water

Other causes of sweet-tasting water include hard minerals like magnesium and limescale, which can alter the pH of the water. While these minerals are generally not harmful, they can cause issues like pipe clogging and skin and hair irritation.

In some cases, sweet-tasting water can be caused by medical conditions like sinus infections, diabetes, or acid reflux. Additionally, water can absorb minerals like magnesium and bicarbonates as it passes through soil and rock, giving it a sweeter taste.

Identifying the Source of Sweet Taste

To identify the source of the sweet taste in water, it is recommended to have a professional water test conducted. Experts can evaluate water samples and provide insights into the condition of the water, as well as recommend filtration solutions if necessary.

Pollutants Affecting Water Taste and Odour

Water taste and odour can be affected by various pollutants, including:

• Algal growth: Algal blooms can produce volatile organic compounds (VOCs), which can give water an unpleasant taste and odour.
• Chlorophenols: Formed when raw water contains phenols and is then chlorinated, resulting in an 'antiseptic' taste.
• Groundwater constituents: Naturally occurring constituents in groundwater, such as dissolved solids, can cause water to taste salty.
• Bacteria: Certain types of bacteria can cause a fishy odour in water.
• Chlorine: Used to treat city water, chlorine can sometimes be detected through taste or odour, even at safe levels.

It is important to note that taste and odour issues in water are not always indicative of harmful pollution but can signal the presence of nuisance constituents or more serious contaminants.

Metallic taste caused by pH outside of acceptable ranges

A metallic taste in water can be unpleasant and off-putting, and is often caused by a pH level that is outside of the acceptable range. This can occur when the water has a high concentration of dissolved solids, which can also give water a salty taste.

While a metallic taste in water is usually not a health concern, it can indicate broader issues with water quality and safety. In some cases, it may be a sign of high concentrations of other, more harmful contaminants. For example, high levels of dissolved solids can indicate elevated concentrations of arsenic, uranium, or other trace elements in groundwater.

It is important to note that a metallic taste in water is different from a metallic taste in the mouth, which can be caused by various medical issues, medications, or even oral health problems. Dysgeusia, a change in the sense of taste, can be a side effect of certain medical conditions, such as kidney problems, liver issues, or even early pregnancy. It can also be caused by certain medications, such as antibiotics, antihistamines, or antidepressants.

To address a metallic taste in water, it is recommended to have the water tested to identify any potential contaminants and ensure it meets acceptable pH levels. Maintaining proper water treatment and distribution systems is crucial to preventing unpleasant tastes and odours.

In summary, a metallic taste in water caused by pH levels outside the acceptable range can be unpleasant and may indicate the presence of other contaminants. However, it is important to distinguish this from a metallic taste in the mouth, which can have various medical or oral health-related causes.

Chlorinated tap water can cause an 'antiseptic' taste

Chlorinated tap water can cause an antiseptic taste. Chlorine is added to drinking water as a disinfectant to protect public health. Water treatment plants monitor chlorine concentrations closely to keep the levels as low as possible while keeping water supplies safe. However, some people are sensitive to the taste and smell of chlorine.

The antiseptic taste of chlorinated tap water is more noticeable due to several factors. Firstly, proximity to a water treatment plant can result in higher chlorine levels in the water supply, leading to a stronger antiseptic taste. Secondly, colder water has a higher capacity to retain chlorine, which can intensify the antiseptic flavour. Additionally, during peak water usage times, such as early morning and evening, water travels faster from the treatment plant, potentially containing higher levels of chlorine. Local incidents, such as a burst water main, can also lead to increased chlorine levels and a more pronounced antiseptic taste.

Chlorinated tap water can also develop an antiseptic taste due to interactions with plumbing materials and appliances. Non-metallic plumbing components, such as rubber washers and hoses, can react with residual chlorine in the water. This reaction is more prevalent when the water is heated, resulting in the formation of antiseptic-tasting compounds. Kettles, for instance, often contain rubber seals and plastic parts that can react with chlorine, impacting the water's taste. Similarly, appliances like washing machines and dishwashers connected directly to the water supply may contribute to the antiseptic flavour if they lack the appropriate non-return valves.

While chlorinated tap water with an antiseptic taste is generally not harmful, it can be unpleasant. To mitigate this issue, individuals can let the water stand in a closed container in the fridge or boil the water before storing it, although this water should be consumed within 24 hours. Alternatively, home water treatment devices, such as water filters, can be used to absorb chlorine and improve the taste.

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