The first stage of treatment at the reverse osmosis plant in Carlsbad, California, is to flow the water through rock, sand, and gravel as shown here. Would this step remove particulate matter? Would this step remove dissolved salts?
[Section 18.4]

Verified step by step guidance

1. The first step in understanding this problem is to recognize the purpose of flowing water through rock, sand, and gravel. This process is known as filtration.
2. Filtration is primarily used to remove particulate matter, which includes larger particles such as sand, silt, and organic material.
3. Particulate matter is physically trapped by the layers of rock, sand, and gravel, effectively removing it from the water.
4. However, dissolved salts are ions that are too small to be captured by physical filtration methods like those involving rock, sand, and gravel.
5. Therefore, while this step is effective at removing particulate matter, it does not remove dissolved salts from the water.

Key Concepts

Filtration

Filtration is a physical separation process that removes solid particles from liquids or gases using a filter medium that allows the fluid to pass while retaining the solid. In the context of reverse osmosis plants, the initial filtration through rock, sand, and gravel effectively removes larger particulate matter, such as sediments and debris, ensuring that the water is cleaner before further treatment.

Dissolved Salts

Dissolved salts refer to ionic compounds that have dissociated into their constituent ions in a solution. Common examples include sodium chloride (table salt) and calcium carbonate. The filtration process through rock, sand, and gravel does not remove dissolved salts, as these ions are too small to be captured by the solid filter media, necessitating further treatment methods like reverse osmosis to effectively eliminate them.

Reverse Osmosis

Reverse osmosis is a water purification process that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water. In this process, water is forced through the membrane under pressure, allowing only water molecules to pass while rejecting dissolved salts and contaminants. This step is crucial for removing dissolved salts that were not eliminated during the initial filtration stage.