Consider the following statements regarding desalination technology and recent developments in India:

1. The Defence Research & Development Organisation (DRDO) has developed an indigenous high-pressure nanoporous multilayered polymeric membrane for seawater desalination.

2. Reverse Osmosis (RO) desalination works by applying external pressure to push water from a low solute concentration to a high solute concentration through a semi-permeable membrane.

3. The new desalination membrane technology is designed for use onboard Offshore Patrol Vessels (OPVs) of the Indian Coast Guard.

4. Seawater typically has a Total Dissolved Solids (TDS) level of about 35,000 ppm, which is reduced to 200–500 ppm after RO treatment.

How many of the above statements are correct?