Tratamiento de agua

Tech Manual Excerpt

FILMTEC Membranes Water Chemistry and Pretreatment: Introduction
Introduction To increase the efficiency and life of reverse osmosis and nanofiltration (RO/NF) systems,effective pretreatment of the feed water is required. Selection of the proper pretreatment will maximize efficiency and membrane life by minimizing: • Fouling • Scaling • Membrane degradation Optimizing: •Product flow • Product quality (salt rejection) • Product recovery • Operating & maintenance costs Fouling is the accumulation of foreign materials from feed water on the active membrane surfaceand/or on the feed spacer to the point of causing operational problems. The term fouling includes the accumulation of all kinds of layers on the membrane and feed spacer surface, including scaling. Morespecifically, colloidal fouling refers to the entrapment of particulate or colloidal matter such as iron flocs or silt, biological fouling (biofouling) is the growth of a biofilm, and organic fouling isthe adsorption of specific organic compounds such as humic substances and oil on to the membrane surface. Scaling refers to the precipitation and deposition within the system of sparingly solublesalts including calcium carbonate, barium sulfate, calcium sulfate, strontium sulfate and calcium fluoride. Pretreatment of feed water must involve a total system approach for continuous and reliableoperation. For example, an improperly designed and/or operated clarifier will result in loading the sand or multimedia filter beyond its operating limits. Such inadequate pretreatment often necessitatesfrequent cleaning of the membrane elements to restore productivity and salt rejection. The cost of cleaning, downtime and lost system performance can be significant. The proper treatment scheme forfeed water depends on: • Feed water source • Feed water composition • Application The type of pretreatment system depends to a large extent on feed water source (i.e., well water, surface water, and...