Seawater desalination: from salt water into potable water

For those who live or have lived in desert areas such as in Saudi Arabia and surrounding areas, must have terbesit in our minds, whence the source of water we consume daily ?? While we are aware that the area we live in is mostly desert ... Of course there is the technology behind it. Let's look at the following article:

WATER CRISIS

In addition due to the geographical location, limited access to clean water sources has become a global problem. Clean water crisis has become a threat in almost all parts of the world. This happens because the natural water sources are no longer able to meet the growing needs of the high growth rate skyrocketing human population and the vigorous industrialization in various fields. In this case, the industry beperan particularly on water pollution source of sewage discharge.

The presence of water on Earth is apparently not much. In the picture below looks that clean water are in a very limited portion compared to other sources of water (sea water). In this number, as well as of the serving of contaminated waste water, so the water is getting smaller net amount.

From the picture above, clear sea water into the huge potential if it can be used as raw material for clean water. With the innovation of technology, the production process and potable water from sea water can be done by utilizing seawater desalination technology.

WORTH DRINKING WATER from AIR SEA?

Sea water has become a raw material for production of clean water since even 60 years ago through a desalination process. Desalination of sea water is a general term that describes the allowance of salt and other impurities that are naturally present in seawater.

Process water production by desalination method is done through several stages, including: making sea water, seawater pretreatment, salt separation process, and final processing.

Intake seawater

The earliest stages in the process of making seawater desalination is a process feedstock. A common method is to install pipes seaward to a distance of several kilometers from the coast. This is done to obtain a good quality of sea water with the sediment surface to avoid movement that generally occurs in shallow ocean depths. Flow rate of sea water sampling done slowly to prevent the entry of marine life into the pipe.

The above method becomes top choice for ease of system installation. However, in terms of performance, the technique is very sensitive to changes in sea conditions that occur along with changes in season and climate. Prevention of marine life to enter into the system is also not as effective as expected.

Alternative methods are being crowded discussed is to utilize the local geological conditions to the coast with the sea water filter systems well (beach wells). With this method, the sea water is extracted from the subsurface (subsurface) beach. In addition, the technology being developed is the type of gallery with a structure resembling a sand filtration mounted beneath the sea surface (seabed) to obtain high quality raw materials. The methods above are covered in the subsurface intake system.

initial processing

Initial treatment is aimed at conditioning the raw material, in terms of impurity content, so friendly to the main desalination processes. Usual impurities contained in sea water include macromolecules (sand and marine life including fish, algae, etc..) And mikromolekul (the causative agent of sedimentation, crystallization and fouling). Technique performed generally include coagulation-flocculation-sedimentation (coagulation-flocculation-sedimentation), low-pressure membrane (low pressure membrane), filtration media (filter media) and cartridge filters.

Initial processing of key importance because it determines the smoothness of the desalination process stability and process performance with the high quality of the feed water. From an economic perspective, as of the beginning of the processing of almost 30% of the overall cost of the process. Cost savings in the initial processing is feasible with alternative applications making sea water as described previously. With raw material quality is better when, pretreatment will be lighter, thereby reducing the consumption of chemicals and the process of reducing the number of process equipment and ultimately decreased the operational costs and improve the performance and stability of the process.

Core process

At this stage, the raw materials that have undergone initial processing will undergo a process of elimination to produce salt water. Based on the salt separation techniques, desalination processes are categorized into two: heat-based and membrane-based.

In the heat-based process, the raw materials are conditioned boiling at low pressure to produce water vapor at low temperatures. In this process, only water evaporation are experiencing, so after collecting and condensing the steam, will produce clean water without salt and impurities. Multistage flash distillation and multi-effect distillation desalination technology is an example of the heat-based.

Unlike the case in the above process which uses heat energy to separate the salt from sea water, using energy-pressure membrane technology. Membrane is a general term for a thin filter which facilitates the separation of selectively - only certain materials that can be passed and retained by this membrane. Membrane type used is very dependent on the application. Especially for desalination, use reverse osmosis (RO) membrane with a non-porous character who is able to perform separation on ion levels, including salt dengang main composition of sodium and chloride ions.

RO membrane filtration is done by pressing the raw material sea water on the membrane surface so pure pass water on the product side, while holding the salt content and other impurities into the waste stream. The resulting product is very pure water with very low ion concentration.

end processing

Conditions of pure water with a low concentration of ions in the desalination products need to be adjusted for comfort when consumed and does not damage the distribution pipes. For consumption, pure water does not taste, the need for the addition of minerals so it seems according to the quality of drinking water: refreshing taste of water comes from mineral deposits. Minimum ion content which can lead to corrosion of the pipe distribution process due to the tendency of the binding of metal ions to pipe water's chemical balance is reached. At the end of the addition of mineral phases performed on the product stream to produce a product water with drinking water quality.

Seawater desalination process to this day continues to grow around the world to meet the needs of clean water and alleviate the problem of water crisis. Very intensive research activities conducted and thorough at every stage of the process to make this process more environmentally friendly, energy efficient and cheap. The process is also suitable to be implemented in Indonesia, which is a maritime country with a long coastline. The study of the energy that led to the economic viability needs to be done further on the implementation of this process.