Water & Wastewater Asia January/February 2021

IN THE FIELD 21
1.2
Organism Relative Abundance ̶ %
1.0
0.8
0.6
0.4
0.2
0.0
SBR 1 SBR 2 Pond 1 Inlet Pond 2 Outlet WWTP Effluent
Nitrospira
Nitrosomonas
Figure 3: Relative abundance of Nitrospira and Nitrosomonas throughout the treatment process
reducing the nitrogenous BOD. The
relative abundance of the organisms
throughout the treatment process is
shown in Figure 3. Both SBR cells had
high relative abundances of Nitrospira
and Nitrosomonas, which is consistent
with the process data that showed
near-complete ammonia removal.
The inlet of Pond 1 had much lower
relative abundance of both organisms.
The sample from the Pond 1 inlet was
taken just after the mixing point of the
raw influent and the SBR influent.
that adding an additional pond would
not increase the capacity of the
treatment system. No further BOD
removal occurs after Pond 1 and
nitrifiers are not present in the pond
system.
The lack of nitrifiers is likely due
to influent toxicity caused by high
hydrogen sulphide concentrations. Pond
systems also do not have the benefit of
recycling beneficial sludge to the front
of the treatment process to overcome
potential toxicity issues. The audit
was able to mitigate capital spending
on an upgrade that would not have
helped the facility meet effluent quality
requirements.
It was determined that a new solution
would be required to overcome the
treatment challenges. A potential
solution includes modifying the SBR to
discharge further into the pond system
once hydrogen sulphide has been air
stripped from the system.
Therefore, the SBR was likely the
source of Nitrospira and Nitrosomonas
at this location. No nitrifying organisms
were detected in the rest of the pond
system. This showed that components
– likely hydrogen sulphide – in the
incoming raw wastewater was likely
toxic to nitrifying organisms.
ECONOMIC ANALYSIS
The municipality had planned to add
a fourth aerated pond to the system
to increase treatment performance
and ensure compliance is met.
The expected capital cost of this
upgrade would be in excess of one
million dollars. By conducting an
audit (estimated cost: $5000), the
consultants were able to determine
Problem: A municipal wastewater
treatment plant (WWTP) was
planning to carry out an expensive
capital upgrade to improve treatment
performance and bring the plant into
compliance. A study was done to
determine if alternative solutions to
the upgrade could be found.
Facility: 3-pond WWTP with SBR pretreatment
for high-strength waste
streams
Investment: Six LuminUltra
GeneCount NGS tests were done at
different areas of the wastewater
system. Process monitoring was
also done throughout the system.
The total estimated cost was
$5000.
Economic Analysis: The NGS
results combined with the process
data showed that the planned
capital upgrades would not improve
the treatment performance of the
systems. The planned upgrades
were estimated at an excess of one
million dollars, which ultimately
would not have solved the problem.
January / February 2021 • waterwastewaterasia.com