Water, Sewage & Effluent March April 2019 | Page 25

Tanks
The need for compact systems
for small lots and for systems in
environmentally sensitive areas is
a catalyst for tank innovation. On
difficult or remote sites, the new
generation of plastic tanks enable
shallow, low-profile installation to
leverage available space. Advances
in manufacturing processes for plastic
tanks have improved this option over
the tanks of the past. Significant
manufacturing
advances
have
increased tank strength and durability
and enabled lightweight tanks of more
than 5 000 litres to be manufactured
that can also be shipped in ‘halves’ to
remote sites.
An Ontario school’s FFBR system in summer (left) and winter (right).
innovations
Advanced wastewater treatment units
(ATUs) are favoured in areas with
poor soils, shallow vertical separation
distances to limiting conditions,
horizontal setback restrictions, tight
lots, high-strength wastewater, and
nitrogen removal needs. These units are
most often installed inside a plastic tank.
www.waterafrica.co.za
Decentralised systems offer many
benefits for rural or remote residential
or community applications and the best
approach varies from case to case.
Community leaders and residents need
to define the community’s environmental
challenges and anticipated growth to
make the best wastewater treatment
choice. Local codes, proximity to water
bodies, and anticipated daily flows are
additional key factors for individual,
commercial, or community systems. In
most cases, the decentralised approach
can offer lower cost, high performance,
and versatility when compared to a
centralised option. 
Conclusion
The final ECOPOD unit polishes the final effluent, removing any carbon not used in the
denitrification
Water Sewage & Effluent March/April 2019
23
Advanced wastewater
treatment units
Chambers
Chambers are highly adaptable and
effective for specialised system
designs and treatment needs and
are commonly used in sand filters,
mound systems, evapotranspiration
beds, community (cluster) systems,
constructed wetlands, large-scale
wastewater treatment plants, with
pre-treatment devices, and even on
toxic waste remediation sites.
A fixed-film bioreactor (FFBR) system at
an Ontario, Canada, school has a flow
rate of 4 500 gallons per day, influent
strength of 300 mg/L BOD, 300 mg/L
TSS, and 60–75 mg/L of total nitrogen.
Stringent nitrogen effluent requirements
dictated primary treatment, first-
stage
nitrification,
second-stage
denitrification, and a polishing stage to
remove any excess carbon.
Operations test data demonstrated
that the primary effluent was nearly
completely nitrifying the available
ammonia in the influent. The first stage
ECOPOD FFBR unit, equipped with
an alkalinity feed, reduced that total
nitrogen load by a minimum of 53 per
cent. With recirculation, the nitrogen
is reduced to the permit level of less
than 20 mg/L. The ECOPOD reactor
was installed with a carbon source
dose system into the dilution zone to
feed the denitrification process. The
final ECOPOD unit polishes the final
effluent, removing any carbon not
utilised in the denitrification process
prior to effluent discharge.
After some fine-tuning of the
recirculation rates and feed rates to
accommodate the variety of influent
flows at this site, the system has a
consistent effluent output of less than 10
mg/L total nitrogen.
Case study 3: Ontario, Canada
performance, ease installation, and
reduce management dilemmas.