Methods for Wastewater Treatment
The bulk of waste of the I-IV class is the combustion residue, animal and plant waste as well as industrial wastewater resulting from wastewater treatment. The large amounts of such waste are due to the outdated technologies that make it impossible to efficiently and quickly purify water. Also there is a lack of treatment facilities.
Continuous development of the society and urbanization lead to an increase in industrial production and, consequently, to an increase of wastewater amounts. The hydrosphere pollution increases, which adversely affects the health of people and the development of fauna and flora. Therefore, an important problem today is the treatment of wastewater, because industrial wastewater contains a variety of contaminants. Especially dangerous is the waste water contaminated with chromium, because this chemical element belongs to the I hazard class.
Methods for Wastewater Treatment. Wastewater treatment uses the following methods: reagent, ion exchange, electrochemical and biological. The most common for chromium wastewater treatment is the reagent method which uses expensive reagents like sodium sulfite, hydrazine, salts of iron (II) and others, the degree of purification is 65-80%. Another effective approach is ion exchange, but it is not widely used because of its duration and cost.
There is also wastewater treatment from chromium by electrochemical method that uses steel electrodes. The drawback of this method is more than four time increase of solid sludge. The biochemical method for purifying wastewater from chromium uses special microorganisms, which consume chromate-bound oxygen; they survive and grow in oxygenated environment. These microorganisms reduce chromate and dichromate ions to chromium hydroxide.
The purification of wastewater by filtration is carried out at the beginning of the treatment, or at the end of the treatment in order to achieve the required physical and chemical characteristics of wastewater.