Heavy metals and fluoride removal from wastewater in the metal plating industry
Customer Application and Activity
A leading global automotive supplier located in northern France uses the Henkel process to endow different components in its heating, ventilation and air-conditioning systems, with anticorrosion and hydrophobic properties.
Problem to be solved
The wastewater generated by the operation contains heavy metals and fluorides. Before being discharged into natural water ways, the site utilized a combination of reagents to treat the effluent:
NaOH for its neutralization
CaCl2 for the precipitation of fluorides and heavy metals
The resulting CaF2 and metal hydroxides were then removed by flocculation and filtration. However, this did not always prove effective in meeting the maximum fluoride concentration imposed by the local authorities (15 mg/l).
Key Achievements
Together with a new treatment process, the characteristics exhibited by Neutralac® SLS45 allowed for the:
Elimination of fluctuating pH levels by maintaining a steady pH at 6.5, which previously ranged between pH 5-12 at the beginning of the process
Increase the pH during the treatment phase from 8.0 to 9.5 for a better precipitation of fluorides
Simplification of the process by using one single reagent to replace the two reagent combination of NaOH and CaCl2
Conclusion
An improved performance in using Neutralac® SLS45 over the previous treatment system was noted, with the calcium hydroxide flocs absorbing most of the fluoride present in the effluent. Using Neutralac® SLS45 yielded:
A more consistent fluoride removal performance that met environmental consent levels
Improved sludge volumes together with the use of alternative flocculants
Effective acid neutralization and improved pH control
