Not all plants have foam due to Nocardia- Some have Microthrix- Some just
have too many solids and some low D.O.. . . . . .. . Some have zoogleal bulking-
Foaming at a plant with Microthrix
or Zoogleal bulking
Are you having problems with Grease? or low nutrients and high loading due to
industry?
This is a
picture of foam from a wastewater treatment plant that everyone said had to have
problems with Nocardia or Microthrix. No one had ever looked under the
microscope at the actual filaments or did a Gram or Neisser stain. In reality,
this plant had too many solids in one of three basins and was also holding
solids too long in the clarifier. The biomass had N. Limicola as the dominant
filament. The plant needed to make a number of process changes as opposed to
just " adding bacterial product" as a quick fix.
Process monitor and control were big recommendations to this plant. All three
basins were "not alike" in reality. Flows to each were changed over the years as
old pipes became clogged. MLSS was not measured in each basin. Too many solids
in one of the basins that only had the foaming problem were detected. Changes to
step feed were also recommended since the final basin was also low on F/M. D.O.
levels were not checked in each basin. Small changes in that also helped create
conditions that literally caused the filamentous bacteria to thrive when they
finally reached the last basin in the process.
Always do a walk through on your plant, look for trouble areas. Are you
creating dead spots in the primary that can cause problems? In the secondary, in
the clarifier, in the sludge holding tank, digestors or in the dewatering and
returned supernatant?
Not all foam is
bad- but it usually indicates a condition
that is going on in your basin- learn what the colors mean. . . .
White, stiff, billowing or
sudsy foam covering a large part of or the entire aeration basin.
a) Start-up or high BOD shock
load condition resulting in high F/M and low MCRT.
b) Excessive wasting or
hydraulic washout.
c) Toxic wastes or temperature shock.
d) RAS flow too low or off.
e) Excessive dairy fats, detergents or other foaming materials or
surfactants.
a) Increase RAS, do not waste
until MLSS level comes up to proper F/M range. Maintain adequate DO levels
(1 to 3 mg/l).
b) Reduce wasting and adjust RAS until normal conditions
are reached.
Segregate stormwater lines from process water collection system.
Divert excessive flows to collection basin if possible for later
treatment.
Add hyraulic equalization basin.
c) re-establish activated sludge organisms. Waste sludge from plant if
possible. Re-seed if possible (bioaugmentation).
Re-establish normal temperature if possible or adjust MCRT if situation
is to continue.
d) Re-establish adequate RAS rate.
e) Pre-treat with anti-foam. Improve primary oils and grease removal.
Consider bioaugmentation to more aggressively degrade waste substrate.
Shiny, thin, dark tan foam on
much of aeration basin surface.
Aeration basin approaching
under loaded (low F/M) condition due to insufficient sludge wasting (too
many solids in the system).
* Increase WAS rate (not more
than 10% per day) until process approaches normal control parameters and
only a modest amount of l light tan foam remains on aeration basin surface.
Check MLVSS, F/M and MCRT to optimize.
Thick, greasy dark- tan foam
covering most of the aeration basin surface.
Aeration basin is critically
under loaded (excessive solids due to insufficient wasting)
Increase WAS rate (not more
than 10% per day) until the excess solids are removed from the system and
normal balance is restored. Check MLVSS, MCRT and F/M ratio to optimize
process parameters.
Normal
healthy foaming on an aeration basin with no problems
Thick
dark brown greasy foam that can get thick enough to have a crust- plant with
Microthrix problems due to grease problems in the lift station
Foaming at plant with filaments
Very white crisp foam from very young sludge
during start up of a new plant
PROBLEM
PROBABLE CAUSE
CORRECTIVE ACTION
Thick, greasy dark- tan foam
covering most of the aeration basin surface, and carries over to the
clarifier (and sometimes over the basin sidewalls).
Filamentous organisms (Nocardia,
M. parvicella)
Increase WAS rate (not more
than 10% per day) to reduce MCRT. Normal filamentous control with chlorine
or peroxide must include treatment (in water spray) and removal of surface
scum (foam) in addition to RASS/MLSS as these organisms tend to concentrate
in the foam. Check MLVSS and F/M ratio to optimize process parameters.
Dark brown, almost black
sudsy foam with detectable septic or sour odor. Mixed liquor is also very
dark brown to black in color.
a) Anaerobic conditions
within the aeration basin.
b) Industrial waste containing dyes or inks.
a) Check DO levels in basin,
and increase aeration / mixing. Reduce organic loading if possible.
b)
Investigate pre-treatment strategies.
Modest amount of fresh, light
tan foam.
Not a problem! Usually a sign
of a well operated process.
"If it ain't broke, don't fix
it!"
Keeping track in a daily log sheet, using photographs, correlating data to
MLSS and to settlometer data as well as using the microscope are all ways to
help you understand what is going on in your system. Remember- it is in reality
a "bug factory- you are growing bacteria to make clean water! Start thinking
like a bug. . .
Information on additional topics, training programs and audits are available
from Environmental Leverage.
Our goal is to help bring new solutions to you
!
Whether that means products, new programs, training, consulting, audits or
lab work.
Normal
healthy foaming on an aeration basin with no problems 
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