It is the process of utilizing energy, such as heat, electricity and other energy, to separate the dissolved mineral salts, organisms, bacteria and viruses and solids of seawater. According to the separation process, the classification of seawater desalination technology is shown in Fig.1. Multi-stage flash (MSF), multi-effect distillation
In the UAE, the number of desalination plants is about 70, and this is about 14% of the total world operating capacity and two-thirds of these are located in Abu Dhabi (Hamdan, 2014). Methods of production of desalinated water include using reverse osmosis (RO) technology and thermal desalination. According to Hamdan (2014), thermal desalination may consist of Multi-Stage Flash and Multi-Effect Distillation among other processes. Multi-Stage Flash desalination accounts for 75% of the desalination while the Multi-Effect Distillation technology accounts for about 18% of the desalination. Reverse Osmosis technology only accounted for 7% of Abu Dhabi’s capacity in 2011 (Hamdan, 2014).
The first ever desalination plant, which was used, was in United Sates of America during the mid-20th century (1955). How Do Desalination Plants Work? There are many desalination techniques; the thermal distillation, reverse osmosis and many more. Thermal distillation is one of the processes that make desalination (removing salt from sea water) possible. The thermal distillation process uses heat to evaporate water and then later liquefy again.
With the development of temperature and pressure measurements, together with an understanding of the properties of gases, land desalination began to play an important role from the early 1950’s. The expansion of oil discoveries in the Arabian Gulf countries, USA, Caribbean Island, and a few others, where drinking water is rare, also affected desalination development. The first commercial land-based seawater desalination plant was installed by the Ottomans in Jeddah, Saudi Arabia. This crude distillation unit was a boiler working under atmospheric pressure, but this unit suffered from severe scale deposits and With the improvement in submerged-tube technology, the first evaporators with a total capacity in excess of 45,000 m3/d were built in Kuwait Curacao in the early
When P and N discharged into lake or water bodies, its can promote eutrophication. So that both N and P must be removed to prevent oxygen deficit in water bodies. There are numerous processes that can be used to remove N and P such as Nitrification, Nitrification/denitrification, A/O , A2/O, Bardenpho, UCT, VIP, Air stripping, Breakpoint chlorination, ion exchange, and chemical precipitation. All of methods have pros and cons. The selection of appropriate method which match with the wastewater characteristic is important.
The methods used involved among others the heating of water in order to purify it. Other means of treating water involved sand and gravel filtration, boiling and straining. At the time the main objective was to make the water taste better since people at the time had no/little knowledge about micro-organisms or chemical contaminants found in water. The principle of coagulation was then discovered by the Egyptians after 1500 BC .In this process, solids were removed by sedimentation (settling) prior to filtration. It is after 500 BC that the Hippocrates came up with the practice of sieving water and inventing the first bag filter which was named the Hippocrative sleeve.
These conventional water treatments were developed to advance treatments and a variety of new treatment technologies were introduced at various times in response to more complex treatment goals such as removing of organic and non-organic impurities these technologies includes Ion exchange, reverse osmosis, Membrane technologies, activated carbon etc. (Crittenden et al., 2012). In Iraq all water treatment plant is conventional and working on removing of suspended and pathogenic impurities only with ought any removing to dissolved impurities. In These conventional plants sedimentation and filtration with coagulant aid are used to remove suspended and colloidal particles and chlorine are used for pathogenic removing. After water Submission to treatment several tests were conducted to measure its parameters and compere these parameters with a standards in order to evaluate its quality and to which extent it matching with required standards.
The membranes are cleaned by air scouring; this way prevents waste water from being produced. Ultraviolet Désinfection-ultraviolet lampes are provided. These lamps protect water from pathogens. Chlorination-Finally, chlorine is added to the water which it protects it while the water is stored. It is the only time any chemicals are used throughout the treatment process.