PROBLEM

     PROBABLE                  CAUSE

           CORRECTIVE ACTION

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 or decrease WAS, 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 hydraulic 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 or DAF.  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.

   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!"