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
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
typically thought to b e expensive and relatively experimental, mem brane
technology is advancing quickly becoming less expensive, improving performance,
and extending life expectancy.