Reuse of Electroplating Wastewater: An Investigation into Factors Affecting Reliability of Reverse Osmosis

Membrane filtration processes such as ultrafiltration and reverse osmosis have great potential in significantly reducing water consumption in metal finishing industries by allowing recycling of treated electroplating effluent that is currently discharged. This research attempted to identify potential foulants in electroplating wastewaters and to study the effect of operating conditions on the performance of selected reverse osmosis membranes. Total dissolved solids of the electroplating waste from a local facility ranged from 3600 to 18,000 ppm. The primary contributors were sodium and sulfate ions which varied from 950 to 7600 ppm and 2200 to 14,200 ppm respectively. The pH of the waste varied from 8.0 to 9.3. With the Dow-FilmTec SW30 membrane, flux with model 10,000 ppm sodium sulfate was about 50 liters per square meter per hour (LMH) at a pressure of 500 psi and 30°C. It reduced to 20 LMH at 5% total solids. With the real waste stream, flux was 8-15 LMH under similar conditions. On-site trials in a continuous feed-and-bleed mode at 3X showed a 75% drop in flux over 7 days without membrane cleaning. Permeate quality was consistently excellent with less than 100 ppm total solids in the permeate.Hazardous Waste Research Fund ; HWR00-163.Ope

Production processes of fermented organic acids targeted around membrane operations: design of the concentration step by conventional electrodialysis

Organic acids are increasingly used for various industrial applications. Their production is mainly achieved by fermentation. Precipitation or extraction stages, which generate big amount of effluents, are then traditionally used to get the acid in a suitable form. To lower the impact on the environment, the implementation of cleaner operations are investigated. In this context, a complete process targeted around membrane operations for clarification, concentration and conversionwas studied. The present paper is devoted to the study of the concentration step, carried out by conventional electrodialysis (EDC). A model, based on the description of the solute and solution fluxes through the membranes is developed. Dedicated procedures are proposed to determine the different contributions, i.e. electromigration and diffusion, to these fluxes so as to feed the model. This approach is then applied to the concentration of sodium lactate solutions. The preponderance of electromigration is thus demonstrated as well as the existence of a maximum achievable concentration, the predicted value of which is confirmed experimentally. Comparison between EDC of sodium and ammonium lactate solutions shows that the counter ion has negligible influence on the transport of lactate. The influence of the membrane characteristics is also drawn from comparison with previously published results. Finally, the predictions of the model are compared with the experimental results concerning the concentration of a fermentation broth and a good agreement is stated. The approach proposed in this paper can be used as well to design EDC concentration of any other organic acid salt than lactate