Page 38 - Energize November 2021

Coal ash amelioration of sewage impacted soil Within 12 months, no evidence of the
sewage spill and little, if any, of ash
remained, having been covered with robust
by AKJ Surridge (SANEDI), KA Reynolds- such, a lower volume of coal is required grass growth. Visible biological indicators
Clausen (Eskom), and HJ Davel (SANDF) in order to generate an equivalent power of the soil health, such as the dark green
output, leading to lower carbon dioxide colour of the grass layer as well as bird and
collaboration between SANEDI, emissions. In addition, the ash produced insect activity in the area, were clear signs
Eskom Holdings and the Department contains a higher amorphous (glass) phase, of the rehabilitation of the impacted area.
A of Defence has mitigated a potential causing it to be more reactive to both
health threat caused by a spill of raw human carbon and water (increased pozzolanicity).
sewage from informal ablution facilities at a Effectively, this means that once
temporary Covid-19 support station. placed into the environment, the ash will
Before this could become an ecological dissolve and release its components more
issue, the quick-action and teamwork of readily, therefore allowing a more rapid
the three partners remediated the situation remediation response.
through the use of a unique approach in Coal ash consists of all inorganic elements
environmental amelioration. contained in the parent coal, so there are
During the first wave of the Covid-19 several trace elements within its composition Figure 2: Showing seasonal surface growth
rehabilitation of the area at 11 months after
pandemic of 2020 in Lephalale, a raw which are required for plant growth. The main application and during winter (May 2021)
sewage spill occurred between 1 and 28 July elements provided in coal ash which are used
2020, which formed a gully flowing into a for healthy, sustained plant growth include: As of October 2021, the area is deemed
grassland area. Unfortunately, more often aluminium, silica, iron, calcium and a small successfully and completely rehabilitated,
than not, human excreta contain seeds of amount of unburnt carbon. and it displays an enriched flora/grass
exotic plants due to people’s dietary intake. A rapid solution to the situation was layer with a healthy activity of various
The impacted area is mainly used for required; to this end, the partners agreed interactions between all-natural role-
recreational purposes such as physical on swift action and subsequently six tons of players within a balanced diversity.
sport and training exercises. From a military fresh run-of-station ash were secured from Aesthetically, the area recovered to its
utilisation perspective, it was therefore Medupi Power Station and applied to the former condition having no odours or
imperative that the area remains as it was affected area on 28 July 2020. The ash was sludge detectable.
before the sewage spill incident occurred not included in the soil, but merely spread
(relating to basal cover and soil pH). on the surface and into the gully which had
Therefore, ideally, the existing grass cover formed through the liquid sewage runoff.
(Cynodon dactylon – “kweek grass”) should
remain vigorous and intact to ensure alien Seasonal photographs were taken over the
plants do not establish in the area. subsequent 15 months in order to visually
Thus, this spill presented not only track the environmental rehabilitation
a potential health hazard, but also a progress. The potential health threat
potentially negative ecological impact, was immediately neutralised through
which required immediate remediation the high pH pasteurisation ability of the
in order to limit the possible spread of coal ash, offering the partners peace of
several diseases. Due to the urgency of mind that sound action had been taken.
this environmental contamination, a rapid Over the ensuing six months, the ash was
response was required to neutralise the incorporated into soil through natural
potential health threat. weathering processes and grass cover
Historical research has indicated that remained healthy and pristine.
sewage sludge soil contamination can
be pasteurised by a pH-driven process Figure 3: Showcasing complete rehabilitation as of
October 2021.
through the addition of coal ash, improving
structure, fertility, pH and water holding Scientifically it has been proven in other
capacity. As a result, it was expected studies that soil with slightly higher lime
that due to the coal ash reactivity, the content (pH), improves the palatability and
known pasteurising ability and soil health nutritional value of plants and although
benefits, the sewage spill would be rapidly this was not evaluated, it can be assumed
ameliorated and the organic compounds to have occurred in this instance. This
from the sewage and coal ash trace collaboration between government entities
elements would be absorbed into the soil. has once again proven that teamwork and
Ash produced at Medupi Power swift action benefited the community and
Station is generated from a single coal environment.
source, offering an ash of uniform quality
and consistency. The power station Contact Barry Bredenkamp, SANEDI,
operates supercritical boilers, which run at Phone 011 038-4302,
higher temperatures and pressures than information@sanedi.org.za,
conventional coal-fired power stations. As Figure 1: Ash applied on soil/spill surface (28 July 2020) www.sanedi.org.za

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