COMPARISON OF PRE-TREATMENT TECHNOLOGIES FOR ZERO-LIQUID DISCHARGE APPLICATIONS

Abstract

RO brine pre-treatment by membrane-based Zero Liquid Discharge (mZLD) was presented as a critical unit process to reclaim the growing quantities of waste RO brine from desalination and water reuse. This thesis compared precipitative softening (PS) and electrocoagulation (EC) pre-treatment for synthetic and augmented industrial RO brines at the bench-scale. In Phase 1, 2-level partial factorial experiments were conducted to study the effect of process operating variables on specific foulant removals. Phase 2 evaluated additional response factors as a function of the Phase 1 operating variables. Finally, response surface methodology aided in elucidating optimal PS and EC operating conditions for mZLD applications. The experimentally verified optimal operating parameters yielded effluents with LSI less than -0.5 using either treatment. However, effluent supernatant turbidity (PS: 47.8; EC: 3.7 NTU) and dissolved aluminium residual (EC: 1.45 ppm) were higher than accepted RO influent quality guidelines. DOC removals ranged from 14.9 – 28.5%.