Beginning of the 21 century develops an awareness of the importance of preserving the environment, including water, but that process is ongoing. Water is the most common substance in the composition of all living beings and includes most of the Earth's surface, about 70.8% while 29.2% is land. Any use of water from many water supply systems for different purposes, there is a change of its physical, chemical and biological properties and it results wastewater whether industrial, household, agricultural or storm. Such water must be collected and appropriately purified and returned to the receiver without consequences to the environment. Lately more and more is important wastewater treatment and construction of wastewater treatment plant at the end of the city's sewage system but also in the industrial plant before entering the city sewer system. It is also important to know the nature and composition of the waste water to be able to apply the appropriate process of purification and to improve the effect. In the industry wastewater after preliminary and primary treatment stage are further processed by biological process.