Laserfiche WebLink
<br />with a single treatment technology. <br /> <br />4.1 Types of Membrane <br /> <br />Membrane technology can broadly be classified into two categories, high-pressure <br />membranes and low-pressure membranes. High-pressure membranes remove <br />molecular contaminants and are suitable for the treatment of TDS. Depending on the <br />concentration of TDS or other contaminants in the water, nanofiltration (NF) or RO <br />membranes can be used for brackish water treatment. High-pressure membranes are <br />configured with individual spiral wound elements contained in a pressure vessel. <br />Hydraulically, the pressure vessels are connected in a multistage array in which water <br />retained by one stage of the array is fed to the next stage. This is done to increase the <br />volume of drinkable water produced by the process. Generally, the pressure vessels are <br />assembled on a skid, making for a very compact arrangement that is easy to operate <br />and automate. Figure 4.1 provides an illustration of a multistage array configuration and <br />a picture of an actual multistage array installed on a skid. High pressure membranes <br />create a residuals stream containing concentrated molecular contaminants and TDS that <br />is difficult to disposal of. <br /> <br />Low-pressure membranes are typically used for the removal of particulates, colloids and <br />turbidity. Microfiltration (MF) and ultrafiltration (UF) membranes are classified as low- <br />pressure membranes. Both MF and UF membranes are ineffective in removing <br />molecular sized contaminants or TDS. However, these membranes are becoming <br />increasingly popular because of their superior ability to remove pathogens such as <br />protozoa, bacteria and viruses from water. A UF membrane cassette is pictured in <br />Figure 4.2. The residuals stream from low-pressure membranes is similar to that of a <br />conventional drinking water treatment process and posses no unique disposal problems. <br /> <br />Feed <br /> <br />3 to 6 Elements <br />per Pressure Vessel <br /> <br /> <br />Pressure Vessel <br />(Typical) <br /> <br /> <br />Permeate <br />80 - 85% Flow <br /> <br />4, 2, 1 Array Configuration <br /> <br />8 <br />