What types of precipitates are commonly removed during filtration processes?

Filtration processes in water treatment are designed to remove various contaminants, including precipitates formed during prior treatment steps. Metal salts from coagulation and lime-softening processes are a primary focus. During coagulation, chemicals like aluminum sulfate or ferric chloride are added to the water to aggregate suspended particles, which can include organic matter, microorganisms, and inorganic particles. The resulting larger particles, known as flocs, can then form metal salts as they settle out of solution, especially when lime is used to adjust pH and remove hardness.

Lime softening involves adding lime to the water, which leads to the precipitation of calcium and magnesium salts. These precipitates are significant because they help reduce hardness and can also remove heavy metals as part of a broader purification strategy. The role of filtration here is to physically remove these precipitated solids from the water, ensuring that the end product is safe for consumption.

In summary, the correct understanding is that filtration specifically targets these metal salts and lime-softening precipitates to enhance the quality of potable water. Other types of contaminants, such as gaseous contaminants and solely organic or mineral deposits, may not be effectively removed during traditional filtration processes, making the focus on metal salts particularly relevant in this context.