Steel plants use a tremendous amount of water for waste transfer, cooling, and dust control. The plants have sintering mills, coke plants, electricity and gas for furnaces, chemical by-products and chemical processes, water cooled rolls, pumps, slab furnaces, mandrels, extrusion equipment, waste water treatment, transfer lines for sludge and slurries.
The production of iron from its ores involves powerful reduction reactions in blast furnaces. Cooling waters are inevitably contaminated with products especially ammonia and cyanide. Production of coke from coal in coking plants also requires water cooling and the use of water in by-products separation. Contamination of waste streams includes gasification products such as benzene, naphthalene, anthracene, cyanide, ammonia, phenols, cresols together with a range of more complex organic compounds known collectively as polycyclic aromatic hydrocarbons (PAH).
• Rolling plants use a tremendous amount of water to cool the rollers and flush the impurities away from the finished stock. This coolant is a mixture of oils and water which gets contaminated with bacteria and must be disposed of as a hazardous waste.. Eventually the bacteria die off.
Treatment of Industrial waste water
The different types of contamination of wastewater require a
variety of strategies to remove the contamination
Technologies used in Steel plants are:
1. Cooling Tower
2. D.M. Plant
|The first unit consists of high capacity strongly acidic cation exchange resin, which converts positive ions of salt and replaces them with hydrogen ions to form respective acids, which are absorbed in next vessel by strongly basic anion exchange resin. The water obtained by this process shows conductivity less than 30 µS/cm and Total Dissolved Solids less than 10 ppm.Further high purity water can be achieved by Mixed Bed Deionizers, which are designed to produce high purity treated water. They can be used as polishing units after two beds DM Plant to obtain high purity water.|
A Conventional Method
• Primary treatment consists of
temporarily holding the sewage in a quiescent basin where heavy solids can
settle to the bottom while oil, grease and lighter solids float to the surface.
The settled and floating materials are removed and the remaining liquid may be
discharged or subjected to secondary treatment.
B Ozonation Method
A sewage transfer pump will transfer the raw effluent into a manual self cleaning filter, and then pressure sand filter & then onward to an ozonator. Ozone will be injected into the raw sewage and mixed in to a contact chamber / holding tank. The ozone will oxidize the organics present in the sewage, thereby reducing the BOD / COD levels of the sewage to acceptable limits.
4. River water treatment
Water purification is a process of removing undesirable chemicals, materials, and biological contaminants from raw water. The goal is to produce water fit for a specific purpose. Water purification may also be designed for a variety of other purposes, including meeting the requirements of medical, pharmacology, chemical and industrial applications. In general the methods used include