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ABSTRACT
The main constituents of the different effluents produced by surface treatment workshops during the cleaning and coating processes of metal parts are reviewed. The ministerial decree of June 30th, 2006 defines the procedures to respect regarding the permissible discharges. The requirements to be respected concerning direct and connected discharges are introduced and compared with those of September 26th, 1985. They relate to the specific consumption of water defined by per square meter of surface treated and concentrations referred to the emission limit values. The respect for specific water consumptions while respecting the necessary rinsing quality imposes a plating line layout with a static rinse tank and a counter current rinsing system having a sequence of either two or three rinsing tanks. The drag-over mass balance for each treatment station allows us to establish the relationship between the drag-in and the drag-out and the concentrations of the various components of the treatment bath.
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Read the articleAUTHOR
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Alain VIDONNE: Senior lecturer at IUT Besançon-Vesoul
INTRODUCTION
The ministerial decree of June 30, 2006, published in the Journal Officiel of September 5, concerns classified installations subject to authorization under heading 2565: metal coating or surface treatment by electrolytic or chemical means. These facilities have a total tank volume in excess of 1,500 liters.
The decree sets concentration emission limits for metals and certain pollutants, as well as specific water consumption which must not exceed 8 liters per square meter of surface treated, or 2 liters in continuous sheet and wire operations.
Some water emission concentration values have been revised upwards or downwards (zinc, nickel, chromium and lead) compared with those set by the decree of September 26, 1985. Others, on the other hand, are unchanged or concern new parameters (silver, arsenic, mercury, total nitrogen, AOX and tributylphosphate).
Regulations on specific consumption and the need to achieve adequate rinse quality call for lines with a rinse configuration that usually combines static and dynamic rinsing. The relationships between flow rates and treatment solution concentrations are established by writing material balances for different parts of the line.
In order to comply with emission concentration limits, effluent must be treated according to a more or less complex protocol, or the process must be "zero discharge".
The various stages and techniques involved in carrying out these operations are described in the "Continuous physico-chemical treatment and zero discharge" dossier at
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Wastewater treatment in surface treatment plants
Different effluents
Regulations
Ministerial order of June 30, 2006.
Ministerial order of September 26, 1985.
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