RESIN TESTING AND ANALYSIS
To track the condition of ion exchange resin and determine the best time for cleaning it, the resin should be periodically sampled and analyzed for physical stability, foulant levels, and the ability to perform the required ion exchange.
Samples should be representative of the entire resin bed. Therefore, samples should be collected at different levels within the bed, or a grain thief or hollow pipe should be used to obtain a "core" sample. During sampling, the inlet and regenerant distributor should be examined, and the condition of the top of the resin bed should be noted. Excessive hills or valleys in the resin bed are an indication of flow distribution problems.
The resin sample should be examined microscopically for signs of fouling and cracked or broken bead. The level of organic and inorganic foulants in the resin should be determined and compared to known standards and the previous condition of the resin. Finally, the salt splitting and total capacity should be measured on anion resin samples to evaluate the rate of degradation or organic fouling.
Since the 1940's, ion exchange resins have been used to remove dissolved salts from water. These resins exchange ions in t he water for ions on the resin exchange sites and hold them until released by a regeneration solu tion (see Chapter 8 for a more detailed discu ssion). Many ion exchange processes exist for a variety of industrial water and wastewater applications. The ion exchange process consumes large quantities of regeneration chemicals, such a s brine, acid, and caustic materials that can presen t significant handling and disposal problems.
In recent years, membrane proccesses have been used increasingly for the pro duction of "pure" waters from fresh water and se awater. Membrane processes are also being a pplied in process and wastewater systems.
Although typically thought to b e expensive and relatively experimental, mem brane technology is advancing quickly becoming less expensive, improving performance, and extending life expectancy.