Exam Question

(a) In osmosis, the pure water flows from a dilute solution to a concentrated solution when it passes through a semipermeable membrane. A semipermeable membrane will only allow small particles to move through it, and it will block all large particles.
Reverse osmosis (RO) is a type of process that is opposite of the osmosis principle. Reverse osmosis is a process wherein a concentrated solution passes through a membrane in a direction opposite to the natural osmosis process due to external pressure, which is higher than the osmotic pressure.
(b)
The RO plant consists of a seawater pump, which ensures continuous circulation throughout the system. A dosing pump that pumps anti-scaling chemicals into the seawater before a set of micro filters, both of which prevent dirt and silt from going into the membrane and protect the membrane from clogging. A high-pressure pump pressurises the system above osmotic pressure, causing the separation of fresh water by the semi-permeable membrane. A salinometer constantly monitors the salinity of the separated water, and water is collected in the freshwater tank. Brine is discharged to the sea.