Rinsing water treatment from degreasing baths

For their surface treatment process and post-activity rinsing, the washing baths need to be supplied with demineralized water at a rate of 1m3/h and in a conductivity range of 0.3 to 50 microsiemens. The washing tunnel in question generates wastewater at a rate of 300L/h. With five wash tunnels operating in two 8-hour shifts, our customer generates up to 24,000L of wastewater per day. This wash water is mainly loaded with cleaning products, oils, greases, metal particles and abrasive dust.
 

With no wastewater treatment plant, the wash water has to be stored before being removed for disposal by an external service provider, involving relatively high disposal and reprocessing costs. Our customer called on the NISKAE team to determine a suitable physico-chemical treatment solution for the treatment and disposal of their rinse water, in compliance with current regulations. 

Several representative samples of the wash water were collected on site and sent to our laboratory experts. A series of flocculation tests and analyses were carried out to obtain a coagulant-flocculant formulation corresponding to our customer’s specific needs. 


The sample from the first degreasing bath is initially opaque and gray in color. The addition of a coagulating and flocculating mono-reagent, at a minimal dosage of 2.0 g/L, produces a clear, clean and translucent filtrate after treatment. The reaction is achieved within a few minutes, with a reduction in iron concentration from 1.22 mg/L to less than 0.01 mg/L.


For the second degreasing bath, the sample received was characterized by its slight yellow-brown hue. The same coagulant-flocculant determined for the first sample is applied at a dosage of 1.0 g/L. After treatment, the water is completely clarified and colorless. Concentrations of heavy metals, particularly iron and copper, are reduced to below 0.01 mg/L. Treatment sludge from both trials is stable, and easily dewatered for use in filter presses.