The maintenance operation frequency and
schedule of inspections for filtration equipment are
shown in appendix III, table F.
Q15. Backwashing should be performed on gravity
filters at what intervals?
When severe algae growth exists on filter sand or
walls, what corrective action should be taken?
Sodium hydroxide is used in filter underdrain
systems of porous plate to correct what
What are the two types of flow rate controllers?
What is the major difference between a pressure
filter system and a gravity filter?
To remove iron oxide in a diatomite filter, a
solution of what chemical and at what percent
should you use?
MAINTENANCE OF AERATION
LEARNING OBJECTIVE: Identify and
understand basic maintenance for aeration
Proper maintenance of aerators is another
important area in water treatment activities.
The recommended maintenance procedures for
waterfall-type aerators (cascade or step, and tray or
splash pan) is as follows:
Weekly, inspect the aerator surfaces for algae or
other growths, precipitated iron oxide, and for
nonuniformity of water distribution and
staining. Clean when necessary. Treat with
copper sulfate or hypochlorite solution to
Every 6 months, clean and repair tray aerators,
removing the trays as necessary. Inspect the
coke tray aerators for biological growths and
coke deterioration. Replace the coke if the
cleaning is not effective. Repair the screen and
enclosures if necessary.
Annually, repair or replace the surfaces on
cascade or step aerators.
INJECTION OR DIFFUSER AERATORS
Injection or diffuser aerators may be either porous
medium design or injection nozzles.
Porous Ceramic Diffusers
The maintenance procedures for porous ceramic
diffusers-plate or tube-is as follows:
Upon evidence of the nonuniform distribution
of air or clogging that impairs operation,
dewater the tank; inspect and clean diffusers if
Every 6 months, drain the aeration tank and
inspect the diffusers for joint leaks, broken
diffusers, and clogging. Porous ceramic
diffusers may suffer clogging of either the
waterside or the air side (underside).
For waterside (porous plate diffusers), use
oxidizing acids to clean organic growths from
the plate surface.
NOTE: Chlorine gas introduced into the air line at
intervals between inspections will help hold down
Removable plates should be soaked in 50
percent nitric acid. Plates grouted in place
cannot be treated with nitric acid; use chromic
acid (made by adding 1 gram of sodium
dichromate to 50 ml of sulfuric acid). Pour
approximately 2 fluid ounces on each plate 2
days in a row.
Acids must be handled carefully. DO NOT
pour water into sulfuric or chromic acid, as it
will explode or splatter. Such acid will cause
severe burns to the skin and clothes. AL-
WAYS pour acid SLOWLY into the water,
while stirring continuously. Acid treatment
should only be done only upon the approval of
the Public Works Officer under supervision
of a chemist or other qualified personnel.
Air side (porous plate diffusers). When
clogging is caused by iron oxide particles
from pipes, treat this condition with a