wastewater treatment is essential when starting a new
plant. Monitoring the growing biology during a startup
provides the insight plant staff need to adjust operations
to achieve a high treatment efficiency. Settleometer
testing of aeration basin effluent in activated sludge
processes can indicate whether the biomass will settle
properly or cause bulking in the system. From evaluation
of settleometer readings and facility mixed liquor
suspended solids (MLSS) concentrations, operators can
calculate sludge volume index (SVI) values that describe
biomass settleability. SVI values are variable in activated
sludge systems, but Jenkins et al. (2003) found that sludge
bulking occurs at SVI numbers greater than 150 ml/g.1
The following case study outlines the startup of a 1 MGD
integrated fixed-film activated sludge (IFAS) process using
ProBiotic Scrubber® II (PBII) as seed.
A wastewater treatment facility in Colorado, servicing
6,600 people, needed an upgrade of their current
infrastructure. The original mechanical plant was built
in 1956 and was last upgraded in 1985. In 25 years, the
plant had deteriorated to the point where the effluent
ammonia levels were exceeding permit limits. This was an
issue because their effluent was released to the Arkansas
River, an essential water resource for downstream farmers
and municipalities. To get the plant discharge back in
compliance, the management of the facility decided
to add on a new treatment train to the existing system.
They added an IFAS process that had a higher treatment
capacity than the old trickling filter plant.
After construction was completed, the system needed to
be seeded with the proper biology for efficient wastewater
treatment. The operators were hesitant to seed the new
IFAS process with activated sludge from the old plant. They
did not want to transmit the same treatment issues from
the existing system to the new one. Because of logistical
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.
concerns and expenses, the project engineer decided to
use BioLynceus® PBII to startup the plant. The IFAS process
was inoculated with PBII in the aeration basin under low
flow conditions. After 10 days of treatment, the biomass
in the new process had aggregated and was ready to start
processing the full influent load.
Figure 1. Settled sludge volume (SSV (grey)), settled sludge
concentration (SSC (blue)) determined from aeration basin
effluent sampling throughout the first month of IFAS operations.
SSVs of the wastewater samples were recorded over 60 minutes
in a settleometer test. MLSS were acquired on settleometer
testing days. SSC values were calculated using the SSVs and MLSS
Settleometer testing was conducted throughout the first
month of IFAS system operations. The results from the
settleometer tests showed SSV decreased over time and
SSC increased. These parameter trends indicated proper
settling in the aeration basin effluent. Additionally, SVI
values were calculated from the 30-minute SSV for each
settleometer test. The averaged SVI number in the first
month of operations was 130 ml/g which was under the
threshold for a poor settling biomass.
After adding PBII for a month, the operations reports
showed that the clarifiers were fully functioning, and
discharge was within NPDES limits. The PBII treatment
provided the facility with an optimal biomass for
wastewater processing. The system was working so
efficiently, the plant was selected as wastewater system of
the year in 2013 by the Colorado Rural Water Association.
BioLynceus® ProBiotic Scrubber® II is an effective biological seed for IFAS system startups.