contact clarifiers. In addition to the basic topics, information is provided on waste
disposal and equipment maintenance. Table 35 (Section 11) presents a summary of
maintenance procedures for rapid-mix basins, flocculators, and clarifiers.
Filtration. In conventional water treatment, filtration is used to remove
floc, suspended matter, and microorganisms carried over from the preceding unit
filtration removes chemical precipitates. Basic information on filter operation can be
found in par. 2.1.5. Topics include conventional filtration, direct filtration, slow sand
filtration, diatomaceous earth filtration, filter media, underdrain systems, surface
agitators, filter control equipment, backwashing procedures, and optimizing filter
Detailed filter maintenance procedures are included in pars. 11.5.5
through 11.5.7. Additional, related information is contained in the publications listed in
pars. 2.2.21, 2.2.26, and 2.2.46.
Disinfection. In water treatment, disinfection is usually the last barrier to
prevent disease-causing organisms from reaching the consumer. Disinfection does not
sterilize water--that is, completely destroy all living organisms. However, experience
has shown that disinfection, in combination with effective filtration, can protect humans
from most waterborne pathogens (disease-causing agents). This section focuses on
chlorine and hypochlorite compounds, but information on other disinfectant/oxidants
such as ozone, permanganate, and chlorine dioxide is provided. General topics
include chlorine chemistry, application points, chlorine handling and storage, chlorine
equipment, and regulations including trihalomethanes (THMs) and other disinfection
byproducts (DBPs), as well as concentration and contact time (CT). Applicable
references are listed in pars. 2.1.2, 2.1.5, 2.2.13, 2.2.46, and 2.3.12.
Maintenance procedures for chlorination equipment are described in pars.
11.8.3, 11.8.4, and 11.8.5.
Fluoridation. Fluoride ion is added to public water supplies to reduce
tooth decay in children. Where fluoridation is practiced, it is strictly regulated by state
and local health departments. Although there are no federal regulations requiring
fluoridation, EPA endorses the practice. This section provides information on
chemicals, chemical feed equipment, dosage requirements, and testing. For specific
guidance on these and related topics, see pars. 2.1.2, 2.1.5, and 2.2.3.
General guidance on maintenance of fluoridation equipment can be found
in pars. 11.8.6 and 11.8.7.