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Hilchenbach, November 28, 2018

Biological wastewater treatment cleans cooling water from galvanizing line

Since July 2017, the Russian company Magnitogorsk Iron & Steel Works (MMK) has been processing cold strip for use in the construction and packaging industries (see newsletter 1/2018) in a new hot-dip galvanizing line supplied by SMS group. The water management system, including water treatment facility, for this line was supplied by SMS group, too.

Wastewater treatment to the biological method

Wastewater resulting from the galvanizing process in a galvanizing line must be conditioned before it is discharged to the public sewage system. For this purpose, there are strict environmental regulations to be observed at any rate. For the first time, SMS group equipped a wastewater treatment system with an additional biological cleaning section. Once the water has been pretreated by demulsification, neutralization, precipitation and flocculation, the actual cleaning process takes place in the membrane biological stage which is the heart of the system. The input of oxygen and nutrient stimulates bacteria to degrade contaminants. The bacteria mass, also called activated sludge, is filtered from the cleaned water via the membrane system to leave just low-contaminated wastewater to be conveyed to the public sewage system.

Cooling water circuit

To supply cooling water in the amount, quality and temperature required, the water management system was designed for the furnace of the galvanizing line to be cooled by the primary, indirect cooling circuit. This circuit is recooled by means of heat exchangers via the secondary cooling circuit which, in turn, is cooled down by cooling towers.

Sieve filters are installed to clean the secondary circuit. The cooling water is stabilized by adding chemicals. To compensate losses due to vaporization in the cooling towers and losses through leakages in the primary circuit, a reverse osmosis system produces demineralized water.

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