Domestic water quality

Introduction

Domestic water quality refers to the quality of water used for household purposes such as drinking, cooking, bathing, and cleaning. It's important to maintain good water quality because contaminants in water can pose a health risk to humans and cause damage to plumbing and appliances.

Factors that impact domestic water quality include source of water (groundwater or surface water), treatment processes, distribution systems, and potential environmental or human-made contamination. There are many physical, chemical, and biological parameters used to evaluate water quality. Physical parameters include temperature, color, odor, and turbidity. Chemical parameters include pH, total dissolved solids (TDS), total hardness, and contaminants like heavy metals, pesticides, and microorganisms. Biological parameters include the presence of microorganisms like bacteria, viruses, and parasites.

It's essential to regularly test your household water to determine its quality and identify any contaminants that may be present. In some areas, the local water authority is responsible for testing and treating the water supply, but in many cases, it's the homeowner's responsibility to test and treat their water if necessary. To maintain good domestic water quality, it's important to use a reliable water treatment system, such as a water filtration system or a water softener, if necessary. Additionally, it's essential to regularly clean and maintain any plumbing and appliances to prevent the buildup of harmful substances.

Indian standards of drinking water

In India, the Bureau of Indian Standards (BIS) is the primary organization responsible for setting standards for drinking water quality. The standards set by BIS are known as IS 10500: 2012 and are based on the guidelines provided by the World Health Organization (WHO).

According to IS 10500: 2012, the parameters for drinking water quality in India include:

1. Physical parameters: color, odor, taste, turbidity, and temperature.
2. Chemical parameters: pH, total dissolved solids (TDS), total hardness, chloride, fluoride, iron, manganese, nitrates, and sulphates.
3. Microbiological parameters: presence of bacteria, viruses, and parasites.

The maximum permissible limit for each parameter is specified in the IS 10500: 2012 standards, and water that exceeds these limits is considered unfit for human consumption. For example, the maximum permissible limit for TDS is 500 mg/L, and for fluoride, it's 1.5 mg/L.

In addition to these standards, the BIS also recommends the use of point-of-use (POU) water purifiers to ensure the safe and hygienic supply of drinking water. POU water purifiers work by removing impurities from the water at the point of use, and they come in various forms, including UV-based purifiers, activated carbon filters, and reverse osmosis systems.

Table 1. Desirable limits of some standard parameters for drinking water.

S. No.	Parameter	Desirable limit
1	Turbidity	1-5
2	pH	6.5-8.5
3	Total Hardness	200-600
4	Calcium	75-200
5	Magnesium	30-100
6	Chlorides	250-1000
7	Sulphates	150-400
8	Nitrate	45
9	Fluoride	0.6-1.2
10	Chromium	0.05
11	Alkalinity	200-600
12	BOD	30-100
13	TDS	500-2000
14	Color	5
15	Iron	0.3
16	Pesticides	absent

It's important to regularly test drinking water for quality and comply with the standards set by BIS to ensure the health and safety of individuals consuming the water. In cases where the drinking water quality is found to be poor, appropriate measures should be taken to treat and improve the water, such as using a POU water purifier or seeking the assistance of a water treatment professional.

Water treatment for safe drinking

Water treatment is the process of making water safe for human consumption by removing harmful contaminants and reducing the levels of certain minerals to meet drinking water standards. There are several mechanisms involved in water treatment, including:

Coagulation and Flocculation

In this process, chemicals such as aluminum sulfate or iron chloride are added to water to neutralize the electric charges of contaminants. This causes particles to stick together (coagulation) and form larger particles (flocculation) that can be easily removed by settling or filtration. Coagulation and flocculation are two important mechanisms in water treatment that help to remove suspended solids, organic matter, and pathogens from raw water.

Coagulation involves the addition of chemicals, known as coagulants, to the water. These coagulants neutralize the electric charges of contaminants, causing them to clump together, or coagulate. The most commonly used coagulants are aluminum sulfate (Al2(SO4)3), iron salts (such as ferric chloride (FeCl3) or ferric sulfate (Fe2(SO4)3)), and polyaluminum chloride (PAC).

Once the coagulants have been added, the next step is flocculation. Flocculation is the process of agitating the water in order to allow the coagulated particles to collide and form larger, heavier particles known as flocs. This is typically done using slow-moving, large-diameter mixing tanks. The flocs formed during flocculation are easier to settle and remove from the water.

Figure 1. Coagulation mechanism.

The combination of coagulation and flocculation effectively removes suspended solids and organic matter from water, improving its clarity and color. It also helps to remove pathogens, such as bacteria and viruses, by either physically removing the particles they are attached to or by destabilizing the particles they are attached to, making it easier to remove them with other processes, such as filtration or disinfection.

Figure 2. Coagulation and flocculation mechanism.

It's important to note that the specific coagulants used and the conditions under which they are added will vary depending on the water source and the specific contaminants present. The process of coagulation and flocculation must be carefully controlled to ensure that the right balance of coagulants and flocculants is used and that the water is mixed for the appropriate amount of time to produce the desired results.

Sedimentation

 

In this process, the water is stored in large tanks or basins to allow the larger particles formed during coagulation and flocculation to settle to the bottom. The clear water is then removed from the top and sent to the next stage of treatment. Sedimentation is a physical process used in water treatment to remove suspended solids from water by allowing them to settle to the bottom of a tank or basin. The process is typically performed after coagulation and flocculation, which work to create larger, heavier particles that are easier to settle.

In sedimentation, water is stored in a large, circular tank or basin. The water is allowed to remain in the tank for a sufficient period of time, usually several hours, to allow the larger particles to settle to the bottom. The clear water is then removed from the top and sent to the next stage of treatment.

Figure 3. Sedimentation tank.

The sedimentation process is facilitated by the use of a lamella clarifier, which is a set of parallel plates that increases the settling area and reduces the height of the sedimentation tank. This helps to increase the efficiency of the sedimentation process by providing more area for the particles to settle and reducing the vertical distance the particles have to travel before reaching the bottom.

Sedimentation is an effective method for removing suspended solids, such as silt, clay, and algae, from water. It is also used to remove particles created during coagulation and flocculation, including flocs and coagulated particles. The process is relatively simple and inexpensive, and it provides a clear, relatively contaminant-free water source that can be used for further treatment or distribution as drinking water.

Figure 4. Cross section of sedimentation tank and associated major components.

It's important to note that sedimentation is only effective in removing larger, heavier particles and may not remove all contaminants, particularly dissolved contaminants. For this reason, it is typically combined with other treatment processes, such as filtration or disinfection, to produce safe drinking water.

Filtration

 

After coagulation and sedimentation, the water is passed through filters made of sand, gravel, and anthracite coal to remove suspended particles and organic matter. Filters may also contain activated carbon, which can remove volatile organic compounds, chlorine, and other dissolved substances.

Figure 5. Cross section of a pressure filtration unit.

Filtration is a process used in water treatment to remove suspended solids, organic matter, and pathogens from water by passing the water through a physical barrier. There are several types of filtration used in water treatment, including sand filtration, multimedia filtration, and reverse osmosis.

Sand filtration is one of the most commonly used filtration methods in water treatment. It involves passing water through a bed of sand and gravel, which acts as a physical barrier to remove suspended solids. The sand and gravel trap the particles, while the clear water passes through. Multimedia filtration uses multiple layers of materials, such as sand, gravel, and anthracite coal, to remove a wide range of contaminants. The different materials have different sizes and densities, which allows them to trap different size particles. Multimedia filtration is often used as a pre-treatment for reverse osmosis or to remove particles too small for sand filtration to effectively remove.

Figure 6. Cross section of filtration unit.

Reverse osmosis is a high-pressure filtration process that uses a semi-permeable membrane to remove a wide range of contaminants, including dissolved solids, organic matter, and pathogens. The water is pressurized against the membrane, which allows only water molecules to pass through, leaving the contaminants behind. Reverse osmosis is often used as a final step in water treatment to ensure that the water is safe for drinking. In all filtration methods, the water must be properly pre-treated to ensure that the filtration system is not clogged by large particles or organic matter. This often includes sedimentation and coagulation/flocculation to remove larger particles and pathogens before filtration.

It's important to note that filtration is not effective in removing all contaminants, particularly those that are dissolved in the water. For this reason, it is typically combined with other treatment processes, such as disinfection, to produce safe drinking water. Additionally, the specific filtration method used will depend on the water source and the specific contaminants present, as well as the required level of water treatment.

Disinfection

Disinfection is a process used in water treatment to destroy or inactivate harmful pathogens, including bacteria, viruses, and parasites, to make the water safe for human consumption. There are several methods of disinfection used in water treatment, including chlorine, ultraviolet (UV) light, and ozone.

Chlorine disinfection is one of the most commonly used methods of water disinfection. Chlorine is added to the water, where it reacts with the pathogens to kill or inactivate them. The amount of chlorine required to effectively disinfect the water depends on several factors, including the type of pathogens present, the temperature, and pH of the water.

UV light disinfection uses ultraviolet light to destroy pathogens in the water. The water is passed through a UV light chamber, where the UV light penetrates the cell walls of the pathogens and disrupts their DNA, effectively killing them. UV light disinfection is a chemical-free method of water treatment, which makes it an attractive alternative to methods that use chemical disinfectants.

Ozone disinfection uses ozone gas to destroy pathogens in the water. Ozone is a highly reactive molecule that is produced by passing oxygen through an electrical discharge. The ozone is then added to the water, where it reacts with the pathogens to kill or inactivate them. Ozone disinfection is a chemical-free method of water treatment and is often used as a secondary treatment step to provide additional disinfection after chlorine or other methods have been used.

Figure 7. Disinfection process.

Regardless of the method of disinfection used, the water must be properly pretreated to ensure that the disinfection process is effective. This often includes sedimentation, coagulation/flocculation, and filtration to remove larger particles and pathogens before disinfection. Additionally, the water must be properly tested to ensure that the disinfection process has been effective and that the water is safe for human consumption.

It's important to note that disinfection does not remove all contaminants from water and may not be effective in removing certain types of pathogens, such as Cryptosporidium and Giardia. For this reason, it is typically combined with other treatment processes, such as filtration, to produce safe drinking water. Additionally, the specific method of disinfection used will depend on the water source, the specific contaminants present, and the required level of water treatment.

pH Adjustment

pH adjustment is a process used in water treatment to control the acidity or basicity (alkalinity) of water. pH is a measure of the concentration of hydrogen ions in water, and it is expressed on a scale from 0 to 14, where 7 is neutral, below 7 is acidic, and above 7 is basic.

The pH of water is important because it can affect the effectiveness of other water treatment processes, such as coagulation, flocculation, and disinfection. For example, if the pH of the water is too low (acidic), coagulation and flocculation may not be effective, and disinfectants may not be as effective in destroying pathogens. On the other hand, if the pH of the water is too high (basic), it can interfere with the effectiveness of disinfectants, and it can cause corrosion of pipes and other equipment.

To adjust the pH of water, a chemical is added to the water to either raise or lower the pH. To raise the pH (make the water more basic), sodium hydroxide or another alkaline chemical is added to the water. To lower the pH (make the water more acidic), sulfuric acid or another acidic chemical is added to the water. The amount of chemical added to adjust the pH of the water depends on several factors, including the pH of the water, the desired pH, and the type of chemical used. The pH of the water is continuously monitored during the adjustment process to ensure that the desired pH is achieved.

It's important to note that pH adjustment should be done carefully and only by trained professionals. Improper pH adjustment can result in water that is not safe for human consumption, and it can also cause damage to pipes and other equipment. Additionally, the pH of the water must be monitored continuously to ensure that it remains within a safe range for human consumption.

Softening

Water softening is a process used in water treatment to remove hard water minerals, such as calcium and magnesium, that can cause a variety of problems, including scaling and buildup of minerals in pipes and appliances, and the formation of soap scum.

There are two main types of water softening processes: ion exchange and reverse osmosis.

Ion exchange water softening is a process in which hard water minerals are removed from the water by exchanging them for sodium ions. The water is passed through a tank filled with a resin material that has sodium ions attached to it. As the water passes through the tank, the calcium and magnesium ions in the water exchange places with the sodium ions on the resin. The softened water then exits the tank, and the resin material is regenerated by flushing it with a concentrated solution of sodium chloride.

Reverse osmosis (RO) water softening is a process in which water is forced through a semi-permeable membrane, and hard water minerals are left behind. The water passes through the membrane, leaving the calcium and magnesium ions on one side of the membrane and the softened water on the other. Reverse osmosis water softening is a highly effective method of water softening, but it can also remove other desirable minerals and ions from the water, so it is often used in combination with other water treatment processes.

Both ion exchange and reverse osmosis water softening can effectively remove hard water minerals, but they have different pros and cons, and the best method for a particular water source depends on the specific water quality and the desired end product.

It's important to note that water softening does not remove all contaminants from water, and it may not be effective in removing certain types of contaminants, such as lead and other heavy metals. For this reason, water softening is typically combined with other water treatment processes, such as filtration and disinfection, to produce safe drinking water. Additionally, the specific method of water softening used will depend on the water source, the specific contaminants present, and the required level of water treatment.

Fluoridation

Fluoridation is the process of adding fluoride to drinking water to prevent tooth decay. Fluoride is a naturally occurring mineral that is found in many water sources, and it has been shown to strengthen tooth enamel, making teeth more resistant to decay.

In drinking water treatment, fluoride is typically added to the water in the form of a compound, such as sodium fluoride or fluorosilicic acid. The exact amount of fluoride added to the water depends on several factors, including the natural level of fluoride in the water, the desired level of fluoride for optimal dental health, and the size of the water system. Once the fluoride is added to the water, it is evenly distributed throughout the system, and it becomes available to users when they drink the water or use it for cooking. The fluoride in the water reacts with the surface of the teeth, forming a protective layer that makes the teeth more resistant to decay.

The effectiveness of fluoridation in reducing tooth decay has been well established, and it is widely considered to be one of the most effective public health measures for improving oral health. However, some concerns have been raised about the safety of fluoride, particularly with respect to high levels of fluoride in drinking water, which can cause a condition known as fluorosis, in which the teeth become discolored and mottled.

To ensure that fluoride levels in drinking water are safe, the levels of fluoride are carefully monitored by water treatment facilities, and they are adjusted as necessary to maintain the desired level for optimal dental health. It's important to note that not all communities add fluoride to their drinking water, and individuals who are concerned about fluoride levels in their drinking water can have their water tested by a laboratory or they can purchase a home testing kit.

In conclusion, fluoridation is a widely used and effective water treatment method for preventing tooth decay, but it is important to monitor fluoride levels in drinking water to ensure that they are safe for human consumption. These steps are usually performed in a specific order to ensure the maximum removal of contaminants and the production of safe drinking water. It's important to note that the specific treatment processes used can vary depending on the quality of the source water and the contaminants it contains.

Importance of sanitation

Sanitation is the process of maintaining cleanliness and hygiene in the environment to protect human health and prevent the spread of disease. The importance of sanitation cannot be overstated, as it plays a crucial role in promoting public health and preventing the spread of infectious diseases. Adequate sanitation is essential for maintaining a safe and healthy environment, especially in areas where there is a high risk of infectious disease transmission. In developing countries, lack of proper sanitation can lead to serious health problems, including water-borne diseases like cholera, dysentery, and typhoid fever, as well as diseases caused by poor hygiene, such as diarrhea and malnutrition.

Figure 6. Environmental sanitation.

Sanitation is also important for reducing the risk of food-borne illness. Inadequate sanitation in food preparation and storage areas can lead to contamination of food, which can cause serious health problems, especially in individuals with weakened immune systems. Proper sanitation practices, such as hand washing, food storage, and preparation, can help prevent food-borne illness and ensure that food is safe for consumption.

Another key aspect of sanitation is the proper disposal of waste. Inadequate waste management can lead to the spread of disease, as well as environmental problems, such as air and water pollution. Effective waste management practices, such as proper disposal of human waste and waste from animals, are crucial for maintaining a safe and healthy environment.

Sanitation is also important for promoting personal hygiene, especially for individuals who are at increased risk of infectious disease transmission, such as children and people with weakened immune systems. Regular hand washing with soap, as well as regular bathing and changing of clothes, are essential for preventing the spread of disease and promoting personal hygiene.

In conclusion, sanitation is a critical component of public health and plays a crucial role in preventing the spread of infectious diseases. Adequate sanitation helps maintain a safe and healthy environment, promotes personal hygiene, and helps prevent food-borne illness and environmental problems. It is essential for ensuring the well-being of individuals and communities, and it is an important aspect of development and progress.