A continuous nanofiltration + evaporation process for high strength rubber wastewater treatment and water reuse

In the rubber parts industry, the treatment of wastewater from the demolding process utilising polymeric agents, traditionally poses a challenge. This is due to the high strength (COD > 10,000 mg/L) and the low biodegradability of the main organic content in the wastewater.

Typically, a thermal process of boilers followed by evaporators is commonly employed to treat the wastewater. Besides frequent boiler maintenance due to severe fouling caused by the nature of the wastewater, high energy costs are nearly prohibitive. At Cikautxo, a Spanish rubber parts manufacturer, the energy costs are in the region of €4.2/m3 treated wastewater.

Following an initial lab scale membrane screening, a pilot study was carried out at Cikautxo in 2012. Nanofiltration using a NF270 membrane was tested and the reject stream was collected and used to feed a full size evaporator.

Without pretreatment, the rate of the nanofiltration process was maintained at a permeate flux of 11 L/m2-h for periods of over 30 h in between flux recovery cleaning. The use of the NF process gave a significantly improved feed water quality, consequently improving the total capacity of the evaporator when compared with the use of the boiler blow down method. The NF + evaporator solution was shown to effectively reduce energy costs by 55% (from €4.2/m3 to €1.9/m3 treated wastewater).

Authors: Xin G., Lopez M. P., Crespo J. G. and Rusten B.

Full publication: https://doi.org/10.1016/j.seppur.2013.08.036