Water, Sewage & Effluent January February 2019 | Page 32

a technology with an ability to mitigate
climate change (WRC TT 649/15).
A fundamental for food production
and food security in contemporary
water-scarce South Africa, is access to
inexpensive but quality irrigation water.
However, irrigation water from rivers,
dams, and boreholes in the peri-urban
equivalent to ~55kWh/PE/y (that is, ~1880
kgCH4/y), and >3 tonnes DW/y biomass.
Furthermore, modelling of energy
flows and greenhouse gas emissions
of the Belmont Valley pilot-scale IAPS,
revealed that an equivalent commercial
system would yield –0.16 tonnes CO 2e /
ML of wastewater treated, indicating
IAPS with facultative pond (top) and raceways (middle) linked via a buffer to the
Puricare-AOP system (bottom).
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Water Sewage & Effluent January/February 2019
space has become more contaminated
with chemicals, bacteria, chlorides,
salts, and various heavy metals. Poor
water quality has a direct impact on
irrigation system efficiency, harms
the soil, poses a major threat for food
production, and farmers struggle to
find cost-effective solutions. To address
irrigation water quality, Dr Derek
Askew and his colleagues developed
the specialised Puricare-Advanced
Oxidation Process (P-AOP). In brief,
advanced oxidation processes employ
reactive oxidising agents such as ozone
(O 3 ) and hydrogen peroxide (H 2 O 2 ) or
both in water treatment.
Reaction of H 2 O 2 together with O 3 is
termed peroxone. The peroxone process
requires an O 3 generation system and
a H 2 O 2 feed system and involves two
essential steps: O 3 dissolution and
H 2 O 2 addition. As reported in the US
Environmental
Protection
Agency
manual titled Alternative Disinfectants
and Oxidants (EPA 815-R-99-014),
peroxone is widely used due to its
simplicity and cost-effectiveness in
generation of radicals for oxidation of
micropollutants, and removal of odour
and colour from wastewater. Indeed,
and as confirmed by Dr Derek Askew,
the P-AOP implemented in South African
agriculture has improved the quality of
irrigation water and cleaned the irrigation
systems. Furthermore, the benefits of the
improved water are passed onto the soil,
resulting in reduced soil compaction.
The P-AOP has also been associated
with reduced equipment maintenance
costs, increased water infiltration, and
improvement in soil aeration and biology.
“Golden Pond” by Ian Laxton
emphasised the suitability of IAPS for
small remote communities in South
Africa. More accurately, it is perhaps
in the peri-urban space that IAPS may
find its best fit. Sufficiently small so as
not to adversely impact the region while
providing a sanitation amenity that in
addition delivers water for irrigation and
biogas for heat and power. Peri-urban
environments are considered zones of
transition between rural and urban and
present an opportunity to demonstrate
approaches that effect sustainable
service delivery and bolster community
resilience. It is within these zones that
full integration of the water, energy,
food, and land nexus can be realised to
ensure, among others, food security.
Techno-economic
perspective
research at Rhodes University has
shown that IAPS is ideally commissioned
with capacity of 1–1.5ML/d (that is,
~7 500PE) and, according to the general
authorisation, the user is therefore not
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