Inorganic fouling control in reverse osmosis wastewater reclamation by purging carbon dioxide

Abstract

Inorganic fouling on the membrane surface is one of the major prevalent issues affecting the performance and cost of reverse osmosis system. Chemical dosage is a widely adopted method for the inhibition of inorganic scale on the membrane surface. In this study, CO was used to control inorganic scale formation on surface of reverse osmosis (RO) membrane in wastewater reclamation. The pH of influent could be lowered by purging CO. It caused an increase in solubility of inorganic salts in water resulting in discharge of principle ions in concentrate stream. A pilot plant study was conducted with four different RO modules including control, with dosage of antiscalant, with purging CO and with co-addition of antiscalant and CO. The effectiveness of CO purging was assessed on the basis of operational analysis, in-line analysis and morphological results. Ryznar stability index was used to determine the scaling potential of system. The examined data indicated that CO purging was successful to inhibit scale formation on the membrane surface. Moreover, CO was found more eco-friendly than antiscalant, as no by-products were generated in concentrate stream.

Recent Drifts in pH-Sensitive Reverse Osmosis

“…The term NF appears to have been first used commercially by the Film-Tec Corporation (now the Dow Chemical Company) in the mid-1980s to describe a new line of membrane products having properties between UF and RO membranes. Owing to the uniqueness and meaningfulness of the word NF, other membrane scientists have begun using it [9][10][11].…”

“…From the solution diffusion model, the solute flux is written as v w c P ¼ Bc m À c P ðÞ (11) where B is a constant. Combining Eqs.…”

Sustainable Membrane-Based Wastewater Reclamation Employing CO2 to Impede an Ionic Precipitation and Consequent Scale Progression onto the Membrane Surfaces

“…Besides several cleaning approaches, the utilization of antifouling agents and the acidification of feed water are widely adopted approaches for the kinetic control of scale deposition; however, their application is conditioned with toxic byproducts and the threshold levels [ 22 ]. We have been introduced to the CO 2 utilization for scale inhibition in RO processes [ 23 ]. Principally, the addition of CO 2 in feed water causes a significant drop in pH, which facilitates the dissociation of salts in their respective ions and finally discharge in concentrate stream [ 24 ].…”

“…Principally, the addition of CO 2 in feed water causes a significant drop in pH, which facilitates the dissociation of salts in their respective ions and finally discharge in concentrate stream [ 24 ]. Earlier, we reported the scale inhibition utilizing CO 2 in constant flux mode of membrane operation and the major part of the existing literature addresses the same operational schemes [ 23 ].…”

Membrane backwash cleaning using CO2 nucleation

“…As they nucleate and move away from the surface, these bubbles provide an extra physical cleaning process and chemical cleaning at the same time, via reduction of the pH of the solution that then acts as a new acid-cleaning medium. Only a few investigations on the CO 2 nucleation in membrane cleaning are reported in the literature; these include removing fouling deposits from membrane filtration surfaces and spacers experimentally (Ngene et al, 2010;Michałek et al, 2015) and numerically (Krzysztoforski and Henczka, 2018;Shahid et al, 2017;Lee and Tien, 2009), and reverse electrodialysis membranes (Moreno et al, 2017). These studies showed that the performance of this technique was superior to any other conventional technique.…”