(3) Locating the aeration process after chlorination will remove
volatile DBPs from the finished water. However, organic precursors not removed in the
water treatment process continue to react with the remaining chlorine residual after
aeration to raise DBP levels in the distribution system. Therefore, removing volatile
DBPs from finished water by aeration is not considered a viable control method.
State Approval of Treatment. A facility must obtain state approval before
significantly modifying its treatment process to comply with DBP requirements. The
facility is required to submit a detailed plan of proposed modifications and safeguards it
will implement to ensure that the bacteriological quality of the drinking water serviced is
not decreased by such changes. Each system must comply with the provisions set
forth in the state-approved plan.
include information on meters, recorders, alarms, and automatic control systems.
Specific information is provided on flow, pressure, and level measurement in
pars. 2.1.5, 2.2.1, and 2.2.24.
Chemicals and Chemical Application. Information about chemicals
commonly used in the water works industry are listed in Table 8. For additional
information on specific chemicals used in given unit processes--including application,
storage, handling, and chemical safety--refer to the appropriate unit process heading
in this section. Maintenance of mechanical equipment is covered in Section 11.
Water Treatment Plant Residues. The most common residues from water
treatment processes are designated as either "slurries" or "sludges." Slurry solids are
usually spent activated carbon or waste diatomaceous earth from diatomaceous filters.
Sludges may be mud-like, natural sediments; gelatinous aluminum, magnesium, or iron
oxides and hydroxides; or calcium carbonate (lime sludge). Water treatment processes
that produce these sludges are presedimentation of raw water; chemical coagulation,
flocculation, and sedimentation; lime-soda ash softening; iron and manganese removal;
Other residues are surface water intake screenings; aqueous solutions of
sodium, calcium, and magnesium chlorides that result from regeneration of cation
exchange water softening resins; and reject stream from membrane processes.
Refer to the applicable paragraphs in this section for a discussion of the
residue characteristics and appropriate solids concentration and dewatering techniques
for the various water treatment processes.