High-grade water can be used in many propose such as household and community sector that used for consumption and industrial sectors that used in the production process and the cooling tower but the process to get high-grade water depends on raw water quality.

There are many types of raw water sources to be used. If a raw water source is surface water, it used just general filtration systems. If it is groundwater, brackish water, or some surface water that containing contaminants and minerals over the standard, the general filtration system (sedimentation and sand filter) not able to remove contaminants. So RO system (Reverse Osmosis) is the best system for mineral and pesticide removal. The main technology is a membrane inside the R.O. that can filter small particles that larger than 0.0001 microns. This means the RO system can remove salinity, odor, color, and microorganisms (the smallest size of microorganism = 0.22 micron). RO system also filters chemicals, toxic, and pesticides out of water. It is concluded that the RO system is one of the best performance filters in the present day.

Normally, the water source of tap water treatment plants is underground water and surface water because it was economical and uses simple technology. On the other hand, in drought regions that do not have enough raw water to produce tap water for supply the whole community. They need to discover another water source to produce clean water. Seawater is the biggest water source on earth but it has much salinity and mineral. It needs to use high and expensive technology than a typical system. RO seawater (SWRO) is the RO membrane technology that can purify saltwater to be clean and clear water with no salt deposits left. This technology is suitable for island areas that do not have enough freshwater sources for consumption.