Reverse Osmosis System

What is Reverse Osmosis system?

Before introducing you to reverse osmosis, you need to understand osmosis first. What is Osmosis? Osmosis is the movement of the solvent through the membrane in order to equalize the concentration between two sides of the membrane. This occurs because the osmotic pressure of the fluid is not equal. The solvent with lower concentration tends to have higher osmotic pressure, therefore tends to give water to the higher concentration solvent to dilute the concentration. Pic 1.

On the other hand, if you give enough pressure to the higher concentration side until it exceeds the osmotic pressure of the pure water side. the water will go from higher concentration side to pure water side Pic 2.

Pic. 1

Pic. 2

Application of RO system

Since RO is the most popular method in TDS removal system. Hence RO has been used in many application.

1. Fresh water Application

Drinking water
Waste water recycle
Food industry
Hydrogen Production
Reef Aquarium

2. Desalination System

Membrane

RO membrane can filter up to 0.0001-micron in perspective 500,000 times smaller than a human hair. therefore only pure water can pass the membrane. RO system can remove bacterias and viruses. which can be proved by laboratory

Disadvantages of RO system

Since RO system has very high resolution of the filtration system. Sometimes membrane can be damaged, usually because of these cause.

Hardness, The inlet water should have SDI under 5 to prevent the formation of sediment inside the membrane. We can achieve this using softener system to absorb hardness as a pre-treatment for RO system

Chlorine, Chlorine cause corrosion to membrane and may cause leakage to membrane to prevent this we need to keep chlorine level under 1 ppm

Turbidity not more than 5 NTU.

If the user cannot control these parameters it will reduce membrane lifespan, normally membrane can last up to 2-3 years. In the case of fouling user can clean the membrane using acid and base. The user will gain the flow rate back but the water quality will be slightly dropped.

How Reverse Osmosis Works

Normal RO system requires a well-trained operator, Therefore to reduce the complexity of the system Treat Chemical use PLC system to reduce the workload and increase the system life span. Also, PLC system can send alarm or report any problems that might happen to operator

The system start from getting the inlet water from pre-treatment system then pump into membrane around 7-13 bar, the membrane will divide water into 2 partitions.

First part, Permeate

This part of water is the pure water that passes through the membrane, with Treat Chemical Design we can produce up to 70% permeate (Recovery rate 70%).

Second part, Concentrate

The concentrate is the by-product of the membrane filtering process. Concentrate will contain all of the impurity that cannot pass the membrane eg. Bacteria, Viruses, Hardness.