Water, Sewage & Effluent January February 2019 | Page 33

Table 1: Water quality of the effluent prior
to P-AOP treatment (May–September
2016)
7.3 ± 0.7
Electrical conductivity
(mS/m) 125.1 ± 5.6
COD (mg/L) 81.3 ± 6.7
TSS (mg/L) 28.6 ± 3.4
Nitrate/nitrite-N (mg/L) 11.2 ±1.9
Ammonium-N (mg/L) 1.9 ± 0.4
Ortho-phosphate (mg/L) 2.3 ± 0.2
Faecal coliforms
(CFU/100 mL) 1.6 × 10 5 ±
0.3 × 10 5
For a typical irrigation set-up, treatment is
continuous and irrigation water directed
to the P-AOP system for ozonation under
pressure, followed by injection of H 2 O 2
(see Chapter 7 of EPA 815-R-99-014).
For the purposes of our evaluation, we
used three scenarios. First, continuous
treatment of IAPS effluent to simulate the
standard irrigation set-up; second, low-
dose peroxone treatment by continuous
circulation of 10 000L of IAPS effluent
for a 24-hour period; and third, high-
www.waterafrica.co.za
Dissolved oxygen (mg/L)
Installation of the Puricare-AOP water system at EBRU: Dr Derek Askew (centre) and
Richard Laubscher (right).
Water Sewage & Effluent January/February 2019
33
8.1 ± 0.2
Professor A Keith Cowan is a director
at the Institute for Environmental
Biotechnology, Rhodes University
(EBRU) and principal investigator.
Taobat A Jimoh is a PhD student
at EBRU. Richard K Laubscher is a
research officer at EBRU. Dr Derek
Askew is the general manager of
Puricare International – Agriculture,
and in charge of scientific and
technical support.
pH
About the authors
innovations
IAPS water quality parameter (units)
between sanitation and irrigation that
the technology is most needed. Indeed,
development and implementation of
wastewater treatment systems like
IAPS are crucial in the fight against
poor sanitation, waterborne diseases,
infections, and contamination of our
limited water resource.
In addition to its efficient nutrient
removal and disinfection, IAPS is also
a bioprocess system with potential
for value recovery. As mentioned, in
addition to water for recycle and/or re-
use, methane and biomass are typical
by-products of wastewater treatment by
IAPS. It is these products that are most
desired for agricultural activity within the
peri-urban space and position IAPS at
the water-energy-food nexus. The in situ
sustainable provision of quality water for
irrigation, a valorised biomass for use as
a soil amendment or fertiliser, and biogas
are precisely the commodities required
to support peri-urban agriculture and
food production. 
dose peroxone treatment by continuous
circulation of 1 500L of IAPS effluent for
a 24-hour period. The latter treatment
protocols confirmed that changes in
water quality were a consequence of
P-AOP peroxone process.
Results revealed that P-AOP peroxone
treatment of IAPS water using the
standard
irrigation
configuration
reduced COD by ≥5%, TSS by ≥7%,
NH 4 +-N by ≥20%, and faecal coliforms by
≥6%. Primary peroxone targets appeared
to include suspended solids and faecal
coliforms. Indeed, low-dose peroxone
treatment reduced both faecal coliforms
and TSS by >40%. Higher doses of
peroxone did not appear to impact TSS
(~45% reduction) but reduced COD,
NH 4 +-N, and faecal coliforms by ≥22%,
≥65%, and ≥95%, respectively. Based on
these findings, it is evident that addition
of a P-AOP to the IAPS process can treat
secondary water to a quality suitable
either for irrigation or discharge into
a water resource that is not a listed
water resource for volumes up to 2ML
of treated wastewater on any given day.
Thus, quality water within the limits and
conditions of the general authorisation
is possible and without any substantial
increase in process footprint.
Even though IAPS can be adapted
to bolster conventional wastewater
treatment processes such as waste
stabilisation ponds, biofilters, and
activated sludge plants that either
underperform, are overloaded, or in
a state of disrepair, it is perhaps as an
intermediary in the peri-urban space
required to apply for a water use license,
provided water use is within the limits
and conditions of said authorisation
(Government Notice No. 665; Revision
of General Authorisations in terms of
Section 39 of the National Water Act
No. 36 of 1998, Government Gazette
Vol. No. 36820, Cape Town). To meet the
conditions of this authorisation requires
that an appropriate tertiary treatment
system be included in the IAPS process.
At treatment capacities of between
1ML/d and 1.5ML/d, the land area for
tertiary treatment processes is in the
range 2 400–2 900m 2 /1 000PE. By contrast,
use of a P-AOP requires very little land
area, as peroxonation of the water takes
place during delivery to the irrigation
system. Also, peroxone acts to remove
chemical deposits biofilm and inhibits
formation of further deposits, keeping the
irrigation system constantly clean in an
environmentally friendly manner.
We therefore initiated a series of
experiments to examine the effect of
peroxone as a tertiary treatment process
on COD and TSS of effluent from an IAPS
treating domestic sewage. Water quality
of the effluent prior to P-AOP treatment
during the period May to September
2016 is summarised in Table 1.