Date of Award
Doctor of Philosophy
Membrane fouling due to silica precipitation during reverse osmosis (RO) continues to be documented as the most common challenge in attaining stable continuous operation of RO systems across water treatment plants (1). Silica scale precipitation is time dependent and involves multiple steps leading to aqueous polymerization, condensation of polymers to form colloids, and deposition onto a solid surface (2). Exceeding the solubility of silica, widely considered to be in the range of 100-140 ppm, under a pH of 8 at 25 °C by various researchers, results in the precipitation of silica on the membranes, thereby limiting water recovery. Once the precipitation occurs, removal and cleaning of the same are nearly impossible (3).
Therefore, pretreatment of silica becomes necessary in regions that have high a concentration of silica in the feed water. The purpose of this research was to develop a treatment system that could treat the concentrate generated by the KBH desalination plant in El Paso with the aim to recover more water for beneficial use, thereby reducing the disposal quantity and increasing the overall recovery of the plant.
The concentrate from the desalination plant was treated with three different processes i.e. first stage RO followed by nanofiltration and second stage RO, first stage RO followed by lime treatment and second stage RO, and first stage RO followed by seawater RO.
The seawater RO treatment process developed above as part of this research, called concentrate enhanced recovery reverse osmosis (CERRO©), has proved to be highly effective in treating the concentrate from the desalination plant containing high levels of silica. The results also showed that the overall recovery at the plant could be maximized without fouling the membranes.
Furthermore, the research also attempted to identify some of the important parameters that aided the recovery process. The effect of parameters like pH, cross flow velocity, permeate flux, initial silica concentration, alkalinity, presence of salts, precipitation time, and the use of antiscalants was studied.
Received from ProQuest
Patwardhan, Gautam, "Water Recovery from Silica Saturated RO Concentrate by the Concentrate Enhanced Reverse Osmosis Process" (2014). Open Access Theses & Dissertations. 1322.