The water supply for a midwestern city contains the following impurities: coarse sand, finely divided particulates, nitrate ions, trihalomethanes, dissolved phosphorus in the form of phosphates, potentially harmful bacterial strains, dissolved organic substances. Which of the following processes or agents, if any, is effective in removing each of these impurities: coarse sand filtration, activated carbon filtration, aeration, ozonization, precipitation with aluminum hydroxide?

Verified step by step guidance

1. Identify the type of impurity and match it with the appropriate removal process.
2. Coarse sand can be removed by coarse sand filtration, which physically separates larger particles from water.
3. Finely divided particulates can be removed by precipitation with aluminum hydroxide, which helps in coagulating and settling these particles.
4. Nitrate ions are typically not removed by the processes listed, but biological denitrification or ion exchange methods are effective.
5. Trihalomethanes can be removed by activated carbon filtration, which adsorbs organic compounds and chlorine by-products.
6. Dissolved phosphorus in the form of phosphates can be removed by precipitation with aluminum hydroxide, forming insoluble aluminum phosphate.
7. Potentially harmful bacterial strains can be effectively removed by ozonization, which disinfects water by oxidizing and destroying bacteria.
8. Dissolved organic substances can be removed by activated carbon filtration, which adsorbs organic molecules from the water.

Key Concepts

Filtration

Filtration is a physical separation process that removes solid particles from liquids or gases by passing the mixture through a filter medium. Coarse sand filtration is effective for removing larger particles, such as sand and debris, while activated carbon filtration targets smaller organic compounds and impurities, including trihalomethanes and dissolved organic substances.

Chemical Precipitation

Chemical precipitation involves adding a chemical agent to a solution to form solid particles that can be removed from the liquid. In this context, aluminum hydroxide can precipitate dissolved phosphates, effectively reducing phosphorus levels in water, which is crucial for preventing eutrophication in aquatic systems.

Ozonization and Aeration

Ozonization is a water treatment process that uses ozone gas to oxidize organic and inorganic contaminants, including bacteria and trihalomethanes, making them easier to remove. Aeration, on the other hand, introduces air into water, promoting the removal of volatile compounds and enhancing the oxidation of dissolved substances, which can help in reducing harmful bacterial strains.