The wastewater treatment depends on the water conditions and the requirements of the evacuation in the emissary. This is the reason why there are two kinds of sewage treatment plants: the simple mechanical and biological sewage treatment plants and the complex ones.
The inorganic wastewater is usually treated in sewage plants just by physical-chemical processes of retention and neutralization such as: sedimentation, precipitation, coagulation, flocculation, ion exchanges and more. The wastewater with organic nature is treated by chemical-biological processes.
The scheme of treatment is chosen based on some technical-economical calculations considering the following factors: the existence of an available land for building a sewage treatment plant, the possibility to ensure sanitary protection areas around the sewage treatment plant, the obligation to ensure the degree of the required treatment, the possibility to ensure the distance from the overflowing waters which are purified, the quantities of sludge which are a result of the whole process, the possibility to hire qualified personnel for the sewage treatment plant and so on. Also, it is important to know that, the normal sewage treatment plants require monitoring. And this is achieved through periodic review of the equipment used and by measuring the water quality.
The first sewage treatment plants were built in England in the nineteenth century. Initially, there was created a sewerage and it discharged into the Thames River. But, because the bad smell, the sewage treatment plants were considered a better idea. In the US, in 1984, there were 15.438 sewage treatment plants, serving a population of 172 millions residents. But, nowadays, another country which has a lot of sewage treatment plants is United Arab Emirates.
Due to the fact that the population of the UAE is concerned about the quality of wastewater, a lot of sewage treatment plants have been built recently. Given the fact that the UAE is an industrial country, visited by millions of people every year, the water consumption is very high. The water is used in almost every domain, starting with washing the dishes and the clothes and ending with the water used for taking showers.