Description:The most widely and commonly distributed air pollutant among the options provided is "a. Carbon monoxide." Carbon monoxide is often found in the air due to the incomplete combustion of fossil fuels, such as in cars and industrial processes. It can be widespread in urban areas and poses health risks when inhaled in high concentrations.

Description:The best indication of air pollution among the options provided is "a. SO2," which stands for sulfur dioxide. Sulfur dioxide is a common pollutant emitted from burning fossil fuels, especially in industrial processes and power generation. It is a key indicator of air pollution and can have harmful effects on both human health and the environment. Monitoring levels of sulfur dioxide helps assess air quality and pollution levels in a given area.

Description:Temporary hardness of water is typically removed by "a. Boiling." When you boil water that has temporary hardness due to the presence of dissolved calcium and magnesium bicarbonates, the heat causes these ions to precipitate and form solid particles. These solid particles can then be removed by filtration or simply by allowing them to settle at the bottom of the container. Boiling effectively reduces the temporary hardness and makes the water more suitable for various domestic and industrial purposes.

Description:The optimum level of fluoride in drinking water per liter is "c. 0.7-1.2 mg/L." This range is generally considered safe for drinking water to help prevent dental cavities without causing adverse health effects from excessive fluoride consumption.

Description:The most effective method of well disinfection is typically done using "d. CaOCl2," which stands for calcium hypochlorite. Calcium hypochlorite is a strong disinfectant that is commonly used for treating water sources, including wells, to kill harmful bacteria, viruses, and other pathogens. It releases chlorine when dissolved in water, making it an effective method for disinfection and ensuring that the water is safe to drink

Description:Slow sand filters are effective at removing impurities from water, but they operate at a relatively slow filtration rate compared to other filtration methods. This means that it takes a longer duration of time for the water to pass through the filter and be purified. While they may require less maintenance and occupy less space compared to some other filtration methods, their slower filtration rate is a characteristic of slow sand filters.

Description:Slow sand filters are known for their effective removal of bacteria and other microorganisms from water. The slow filtration process allows for a biofilm to develop on the surface of the sand bed, which plays a crucial role in microbial removal. In contrast, rapid sand filters are primarily designed for the physical removal of particulate matter and are not as effective at microbial removal as slow sand filters.

Description:Rainwater is often considered one of the purest forms of natural water. It starts as condensation in the atmosphere and falls to the ground as precipitation. It doesn't contain the impurities and contaminants that can be found in surface water sources like rivers, or in groundwater sources like deep wells, which can be influenced by the surrounding geology and human activities. However, the purity of rainwater can be influenced by atmospheric pollution, so in very polluted areas, it may not always be entirely pure.

Description:The residual chlorine concentration after chlorination of water should typically be: c. 0.5 mg/L after 1 hour This concentration ensures that there is a sufficient amount of chlorine remaining in the water to continue disinfection and to provide protection against microbial contamination. The specific residual chlorine levels may vary depending on local regulations and water treatment practices, but 0.5 mg/L after 1 hour is a common guideline for maintaining water quality.

Description:The minimum recommended level of residual chlorine in drinking water for one hour is typically: b. 0.5 mg/L This level of residual chlorine helps ensure that the water remains adequately disinfected and safe for consumption by preventing the regrowth of harmful microorganisms in the distribution system.

Description:The hardness of water is typically expressed as: b. mg/L (milligrams per liter) Hardness refers to the concentration of calcium and magnesium ions in water and is commonly measured in milligrams of calcium carbonate (CaCO3) equivalent per liter of water (mg/L).

Description:The amount of chlorine tablet required to disinfect a specific volume of water can vary depending on the tablet's concentration and the desired chlorine residual. However, a common guideline is to use: c. 0.5 g (grams) This is a general approximation, and the exact dosage may vary based on factors such as water quality, temperature, and contact time. It's essential to follow local guidelines and manufacturer recommendations for precise dosing when using chlorine tablets for water disinfection.

Description:Adding sodium carbonate (soda ash) into water can help precipitate calcium and magnesium ions, thus reducing hardness. The ion exchange process (base exchange process) involves the use of ion exchange resins to replace calcium and magnesium ions with sodium ions, effectively softening the water. Chlorination is primarily used for disinfection and does not directly remove hardness. However, in some cases, chlorination can help precipitate calcium and magnesium, but it's not a primary method for water softening.

Description:The contact time for chlorination typically recommended for disinfecting water is: b. 1 hour However, the specific contact time may vary depending on local regulations and water treatment practices. It's essential to follow recommended guidelines for the proper chlorination of water to ensure effective disinfection and safety.

Description:The disinfecting action of chlorine on water is mainly due to: b. Hypochlorous acid Hypochlorous acid (HOCl) is the active form of chlorine responsible for its disinfection properties when it reacts with microorganisms in water. It effectively kills or inactivates bacteria, viruses, and other pathogens, making the water safe for consumption.

Description:The orthotolidine test is a chemical method used to determine the presence of chlorine that is chemically combined or bound to other substances, often referred to as "bound chlorine." This test helps measure the chlorine residuals that are not readily available as free chlorine in water.

Description:The orthotolidine test is used to detect both free and combined chlorine in water. It provides a measure of the total chlorine present, including the chlorine that is free and available for disinfection and the chlorine that is combined with substances in the water.

Description:Bleaching powder, also known as calcium hypochlorite, is a chemical compound used for disinfection and bleaching purposes, and it typically contains a significant amount of chlorine. The exact chlorine content may vary slightly depending on the manufacturer and specific product formulation, but it is typically around 33% chlorine by weight.

Description:Temporary hardness is caused by the dissolved bicarbonate ions of calcium (Ca²⁺) and magnesium (Mg²⁺) in water. When water with temporary hardness is heated or when the bicarbonates are exposed to air, they can precipitate as carbonate solids, leading to the formation of scale. This type of hardness can be removed through processes like boiling or adding chemicals that precipitate the ions.

Description:Hard water can lead to increased soap consumption because it forms insoluble soap scum when mixed with soap, making it less effective for cleaning. The other options listed (increased fuel consumption, erosion of lead pipes, and scaling of boilers) are common features or problems associated with hard water.

Description:Coliform tests are conducted to detect the presence of coliform bacteria in water, which can indicate contamination by fecal matter or other pathogens. It is a common method used to assess the quality of drinking water and to ensure that it is safe for consumption.

Description:E. coli is a common and specific indicator of fecal contamination in water. Its presence suggests that water may be contaminated with sewage or other sources of fecal material, which can carry harmful pathogens. Monitoring E. coli levels is a key aspect of assessing the safety of water for human consumption.

Description:E. coli is a specific indicator of fecal contamination in water. Its presence suggests that the water may be contaminated with sewage or other sources of fecal material, which can carry harmful pathogens and pose a health risk if consumed. Monitoring E. coli levels is important for assessing the safety of drinking water.

Description:Streptococci, specifically fecal streptococci, are used as indicators for recent fecal contamination of water. Their presence suggests recent contamination with fecal material, which can carry harmful pathogens. Monitoring fecal streptococci levels is one way to assess the quality and safety of water.

Description:Clostridium spores are not typically used as indicators of recent contamination in water. Instead, they are more commonly associated with the presence of anaerobic bacteria and are not specific indicators of fecal contamination or recent contamination events in the same way that coliforms or fecal streptococci are. The other options listed are more accurate in the context of water quality estimation.