regulations, operation of the ion exchange process, process control tests, and common
operating problems. Recordkeeping and safety precautions are also discussed.
Maintenance of ion exchange equipment is discussed in par. 11.5.8.
Adsorption. Carbon adsorption has historically been used to improve the
appearance and flavor of water. Today, the adsorption process is gaining wider use in
the water works industry to remove a broad range of organic contaminants.
Paragraph 2.1.5 includes information on the principles of adsorption plus the facilities
for applying powdered activated carbon (PAC) and granular activated carbon (GAC).
Aeration. Aeration is used to reduce the concentration of certain
objectionable dissolved gases such as hydrogen sulfide, carbon dioxide, and volatile
organic chemicals (VOCs) and to oxidize dissolved metals. Aeration is often the first
process used in a water treatment plant. At other installations, aeration and
disinfection may be the only treatment provided. Information on various types of
aerators can be found in par. 2.1.5. Maintenance of aeration equipment is discussed in
Membrane Processes. In this process, water is forced through a porous
membrane while contaminants are held back or rejected. The references listed in
pars. 2.1.5, 2.2.28, and 2.3.15 provide information on the types of membrane
processes, operating principles, membrane types, feedwater concerns, post-treatment,
membrane cleaning, and reject water disposal.
Taste and Odor Control. Controlling tastes and odors is one of the most
troublesome problems in water treatment. Tastes and odors appear in both ground and
surface water supplies. The main means of control are aeration (par. 5.4.12),
adsorption (par. 5.4.11), and oxidation (par. 5.4.5). Additional information on taste and
odor can be found in par. 2.3.6.
Controlling Organic Chemicals. The SDWA regulates four categories of
organic contaminants: pesticides, volatile organic compounds (VOCs), synthetic
organic chemicals (SOCs), and DBPs. Effectively removing organic chemicals requires
special treatment techniques. See par. 3.7 for monitoring and reporting requirements.
Pesticides Group--Treatment. Activated carbon adsorption is the most
effective method available for removing pesticides. Some pesticide removal occurs
during conventional treatment by coagulation, sedimentation, and filtration. However,
removals are very small, usually less than 10 percent. Chemical oxidation with
chlorine, ozone, or potassium permanganate also removes pesticides, also generally
less than 10 percent.