Water hardness

As we all know water is an elixir of life most of the living tissue is made up of water. Water is mainly odorless, transparent, colorless, and tasteless liquid and is required for the survival and growth of all living organisms. As per the chemical property, water is mainly categorized as hard water and soft water (1). Water hardness is mainly due to the presence of two main ions calcium and magnesium (2) and due to the presence of nitrogen, iron, phosphorus, and sulfur in minor quantity (3). Heavy metals can also cause hardness in water like lead, chromium, and mercury. Minerals like calcium bicarbonate also contribute to the hardness of the water.

Why it is important to know the hardness of water

Knowing the hardness of water is important because it helps in evaluating its use as a domestic or industrial water supply. Hard water interferes with laundering, washing, bathing, and personal uses (3). Besides this hard water is also not suitable for drinking and causes some serious health hazards.

Difficulties of using hard water in a day to day life (1)

1. Hard water interferes with cleaning tasks like laundry, dishwashing, and cleaning of glasses. Due to the presence of calcium in hard water, hard water leaves calcium deposits on everything.

2. Hard water also interferes with bathing and personal grooming. Bathing with soap in hard water leaves sticky soap curd on the skin. Soap curd on hair may make it dull, lifeless, and difficult to manage. Skin washed with hard water can become itchy and dry.

3. Hard water leaves calcium deposits in the form of a thin film on glass shower doors, shower walls, bathtubs, sinks, faucets, etc. which are impossible to remove.

Types of water hardness

There are two types of water hardness (8)

1. Temporary hardness

This type of hardness of water can be removed easily by boiling as it promotes the formation of carbonate from bicarbonates and precipitates calcium carbonates. Another way to remove temporary hardness is by adding lime known as lime softening.

2. Permanent hardness

This type of hardness is mainly due to calcium and magnesium sulfate and chlorides. It can not be removed by boiling and lime method. For the removal of permanent hardness water softener and ion-exchange columns are used.

What is soft water (pure water)

When the hardness is less than 50 mg/l it is known as soft water. Soft water is free from a high amount of magnesium, calcium, and heavy metals. It also does not contain carbonates, bicarbonates, and any inorganic materials.

How to determine the hardness of water

The hardness of water can be determined by the amount of soap needed to produce suds. Therefore it is also known as the soap-wasting property of water. Hard water does not produce any suds or requires a large amount of soap to produce suds. This is because soap is required to remove the hardness of water when all the ions in the water get bonded with the soap only suds will form (2).

Water hardness is measured as ppm (parts per million) of calcium carbonate. Based on this (4).

Effect on the body due to the hardness of water

According to WHO the health effect of hard water is mainly due to the salt’s calcium and magnesium present in it (5). Although the absorption mechanism of the body protects against the excessive intake of calcium. But it may affect the absorption of other minerals like iron and zinc. Intake of these minerals in adequate amounts is good for the body. However, excessive intake may cause some serious health problems. Some of the health effects due to the hardness of water are as follows

1. Excessive intake of calcium

Although our body is designed in such a way that excessive intake of minerals is either not absorbed or excreted out. However, people with some kind of malfunction may suffer from excessive intake. People with hypercalcemia, metabolic alkalosis, and renal insufficiency can interact with iron, zinc, magnesium, and phosphorus within the intestine, thereby reducing the absorption of these minerals (6).

2. Hyper magnesia

It is the malfunction of the kidney to excrete excess magnesium from the body (7). Which ultimately results in diarrhea and constipation.

3. Hard water causes reproduction problems

Studies suggested that excessive calcium and magnesium show the occurrence of reproductive failure and stillborn. Excessive calcium also shows a negative influence on fertility or infertility in men (5).

4. Eczema

Studies suggested that hard water increased soap usage which further resides on the skin or clothes. These soap salt residues result in irritation and cause eczema (6). Additional studies are underway.

Water hardness in drinking water

According to WHO the degree of hardness in drinking water is important for the acceptability of the consumers. Softening of hard water depends on various circumstances like the locality from where the water is taken, quality issues, and piping material and corrosion. It is important to know the adequate amount of calcium magnesium and other minerals required in drinking water before its modification (6).

How to determine the hardness of water

The hardness of water is determined by the amount of CaCo₃ in mg/l. There are two main methods to determine which are as follows

1. Titration method using EDTA

This method mainly uses ethylenediaminetetracetic acid (EDTA), chelating agents, which form complex ions with Ca²⁺ and Mg²⁺ and other divalent ions causing hardness. The reaction between the ions can be shown by using an indicator like Eriochrome Black T (EBT) (blue color solution).

2. Determining titration by calculation

In this method, the concentration of cations should be known and then all concentrations are expressed in terms of CaCO₃.

Are hardness and alkalinity the same or different

Both hardness and alkalinity are different from each other. In simple words, we can say water hardness is the amount of calcium and magnesium ions present in it. Whereas alkalinity is the measure of solutions’ ability to neutralize the acid.