(c) Inadequate backwashing will lead to reduced permeability of the
sand and eventual channeling.
(d) In some cases where high rate sand filters have not removed
turbidity satisfactorily, alum can be used. Alum leads to better water quality with no
Part 4. Algae Control in Swimming Pools.
1-15. GENERAL INFORMATION
These plant forms are brought into the pool by the wind, with the bathers, and
with makeup water. If uncontrolled, they will grow abundantly in the presence of
sunlight. They are found in the free floating and clinging varieties. The clinging type will
embed itself into pores and crevices in concrete and is a more difficult type to treat. An
inspector must ensure that Army pool operators control algae growth.
1-16. ALGAE CONTROL
a. Objectionable Features of Algae.
(1) Chlorine demand. Algae will create a high chlorine demand. Once they
have become established in the pool, the maintenance of residual chlorine is difficult.
(2) Water turbidity. The increased turbidity in the pool due to algae is not
only unattractive but prevents proper swimmer supervision.
(3) Slipping. Algae growths may increase pool accidents from bathers
slipping on pool bottoms, sides, walkways, and ladders.
(4) Effect on bacterial growth. Algae protect bacteria from the effects of
chlorine by creating high chlorine demand themselves and may actually encourage
Odor. Algae create odor problems, particularly when reacting with
b. Detecting Algae Growth Early. Algae require carbon dioxide in order to
manufacture food. In the process of removing carbon dioxide from water, there is a
definite increase in the pH. This may be seen in a radical jump in pH (from 7.5 to 8.0 as
an example) in several hours, before there is any noticeable growth in the water.
c. Methods of Control.
(1) Routine chlorination. The maintenance of free available chlorine in the
pool at all times will help prevent the start of algae troubles.