What does Lime/Soda ash precipitate from water treatment processes?

The process of using lime and soda ash in water treatment primarily focuses on softening water by precipitating hardness-causing substances, specifically calcium and magnesium ions. When lime (which provides calcium ions) is added to water, it reacts with bicarbonate ions and precipitates calcium carbonate. Soda ash (sodium carbonate) also contributes to this process by increasing the carbonate concentration, which helps to further precipitate both carbonates and non-carbonate hardness.

This precipitation is essential in reducing water hardness, which can lead to scaling in pipes and appliances as well as interfere with many water uses. The specific focus on carbonates and non-carbonates highlights the types of compounds that are being targeted within this treatment process, making the choice especially relevant.

The other options revolve around substances that are not typically addressed directly in the lime/soda ash treatment process. Silicates and phosphates, while they may be present in some water sources, do not primarily precipitate out due to lime and soda ash treatment. Similarly, nitrates and sulfates, as well as chlorides and fluorides, are not the main targets of this specific water treatment method and do not form precipitates from lime or soda ash usage.