Electrodialysis applied to the treatment of an university sewage for water recovery

Abstract

The objective of this study was to evaluate the application of electrodialysis (ED) as tertiary treatment of a university effluent aiming at the water recovery and reuse in three alternatives: agricultural, urban and fish farming. The study evaluated the behavior of membranes and effluent quality after successive batches of electrodialysis treatment, without cleaning the system, using the same effluent and with the monitoring of the electrical potential of the system during the treatment. Despite the electrical potential of the system increase at the end of each batch treatment, the transport of ions through the membranes was not compromised. The results showed the removal of ammoniacal nitrogen (95–98%), total (80–99%) and dissolved (80–97%) solids, total inorganic carbon (40–97%), cations (>80%) and anions (>70%), indicating that, for these parameters, the treatment by electrodialysis was an interesting alternative. Besides the aim of ED is the removal of electric charged compounds, it was observed the removal of color (23–44%), turbidity (48–62%), Chemical Oxygen Demand (COD) (49–62%), Biochemical Oxygen Demand (BOD5,20) (38–52%), total carbon (29–45%) and total organic carbon (16–36%), but, in lower levels than that obtained for ions removal. These data suggest the application of another type of treatment before or after electrodialysis. Based on these results, the agricultural or urban reuse alternatives are indicated, where only pH and turbidity correction are necessary. For the use in fish farming, pH correction should be performed.