operations can have a significant impact on biological
treatment efficiency. Activated sludge is traditionally used
to seed new treatment systems and supplement others
that need bioaugmentation. A common issue in activated
sludge systems is sludge bulking (SB), or the uncontrolled
growth of filamentous bacteria (FB).1 Impacts of a bulking
sludge include (but are not limited to) poor settleability,
impaired biological nutrient removal, and increased facility
maintenance.
Predicting whether SB will occur in a newly seeded
wastewater process is difficult, because the FB in activated
sludge respond differently to varying system conditions. One
method to prevent bulking is to quantify the proportion of
FB in activated sludge before inoculation. Previous studies
have found that SB can occur in systems with a volume
fraction of FB as low as 1-20%.2,3
Even when filament forming organisms are in low abundance,
they can still cause treatment issues. Bioaugmentation with
a specifically designed microbial community can be a more
reliable alternative to using activated sludge as seed. The
following case study outlines the use of ProBiotic Scrubber®
II (PBII) in a 0.7 MGD mechanical wastewater treatment
plant (MWTP) to restore a healthy biomass after the plant
was seeded with FB.
The wastewater from a small resort town in Colorado was
processed at a mechanical plant with rotating bed contactors
for nutrient removal. The plant was operating properly until
a concentrated load of petroleum based toxic waste was
introduced to the system. The biological treatment was
inhibited so severely by this event that the MWTP needed
reseeding. To reinstate their plant biomass, the operators
brought in activated sludge from a neighboring wastewater
treatment facility and added several loads to the plant.
1 Jenkins, D., Richard, M.G., Daigger, G.T., 2003. Manual on the Causes and Control
of Activated Sludge Bulking, Foaming, and Other Solids Separation Problems.
Lewis Publishers, Boca Raton, FL.
2 Krhutkova O, Ruzickova I, Wanner J. Microbial evaluation of activated sludge
and filamentous population at eight Czech nutrient removal activated sludge
plants during year 2000. Water Sci Technol 2002;46(1/2):471–8.
3 Palm JC, Jenkins D, Parker DS. Relationship between organic loading, dissolved
oxygen concentration and sludge settleability in the completely mixed
activated sludge process. J Water Pollut Control Fed 1980;52:2484–506.
What the operators didn’t know was that they had seeded
their system with FB that would cause issues in the future.
Shortly after inoculation, the plant was having troubles with
foaming, solids settling, and continuously clogged filters.
Facility personnel were scheduled around the clock just to
keep up with backwashing the filters. After examining a mixed
liquor sample from the plant, the head operator realized
that FB accumulated in the reactor and were preventing
solids and nutrient reduction from occurring. They needed
to decrease the abundance of these organisms to resume
proper wastewater processing. The facility management
contacted BioLynceus® to provide a bioaugmentation plan
to reinstate a healthy biological community in the treatment
Figure 1. MWTF aeration basin after the PBII treatment with
regular foam development.
BioLynceus® PBII was supplied to the aeration tank of the 0.7
MGD system. 24 hours after PBII was applied, nitrification
was restored in the basin. Suspended solids were gradually
reduced in the plant effluent over several weeks. This
indicated that the biology in the facility was shifting to a
more desirable composition; one that was allowing settling
to occur. Foaming was also reduced in the aeration basin
to normal amounts (Figure 1). The operators were relieved
to see such an improvement in their biological treatment,
because they had to meet stringent NPDES permit limits to
discharge into the Blue River.
After treating the MWTP with PBII, the system established
a better settling and more equipped biomass for processing
influent waster. The facility now keeps PBII on hand to restart
the plant instead of hauling activated sludge.
BioLynceus® ProBiotic Scrubber® II is an effective seed for restarting MWTPs.