Reverse Osmosis, simply called as RO, is a water purification method that removes ions, molecules and other larger particles from water using a semipermeable membrane. Desalination or removing salt from seawater is done by using reverse osmosis.

A solvent is forced into a region of low soluble concentration from a high solute concentration by applying pressure. This solution passes through a semipermeable membrane and while it does, unwanted particles and molecules are removed.

Usually, a single-pass seawater RO system has the following:
1. Intake – A pump at the source of water to be purified.
2. Pre-treatment – This stage involves removal of solids, sediments, carbonic acid from water, and dosing of oxidising biocodes to kill bacteria.
3. High-pressure pump – This allows the water to pass through the membrane. The pressure needed for seawater ranges from 800 to 1180 psi, and for brackish water, 225 to 376 psi.
4. Membrane – There is a pressure vessel with a membrane, allowing feed water to be pressed against the membrane. RO system membranes are made in a range of configurations and the two most common are spiral-wound and hollow-fiber.
5. Energy recovery – This is used to reduce the energy consumption.
6. Remineralisation and pH adjustment – desalinated water needs to be stabilized to protect downstream pipelines and storage by adding lime or caustic soda which prevents corrosion.
7. Disinfection – This secures secondary protection against downstream and membrane problems.

One example of such technology is the Hitachi Aqua-tech Standardised RO Desalination Systems. These systems are built into. brand new 20- and 40-foot containers that meet international quality standards, and can pump out at least 2,000 liters of water per hour

Each system can be broken down into these parts or modules:

RO systems are most efficient where ground or fresh water is not readily available but a supply of seawater is present. Also, due to the amount of water and energy needed, it is also suitable where the demand of water is high.

Do you know of any communities that can benefit from this innovation? Let us know! We are excited to work with you in bringing sustainable development solutions. To help achieve clean and safe drinking water for all, send us an email at giftinglife@force21.cwtlimited.com

Liezel Salera, Assistant Manager
Community Outreach and Development