Authored by: AKJ Surridge (SANEDI), KA Reynolds-Clausen (Eskom), HJ Davel (SANDF) A collaboration between SANEDI, Eskom Holdings and Department of Defence, has mitigated a potential health threat caused by a spill of raw human sewage from informal ablution facilities at a temporary Covid-19 support station.
Before this could become an ecological issue,the quick-action and teamwork of the three partners remediated the situation through the use of a unique approach in environmental amelioration. During the first wave of the Covid-19 pandemic of 2020 in Lephalale, Limpopo in South Africa, a raw sewage spill occurred between 1 to 28 July 2020, which formed a gully flowing into a grassland area. Unfortunately, more often than not, human excreta carries seeds of exotic plants due to our dietary intake. The impacted area is mainly used for recreational purposes such as physical sport and training exercises. From a military utilisation perspective, it was therefore imperative that the area remains as it was before the sewage spill incident occurred (relating to basal cover and soil pH).
Therefore, ideally, the existing grass cover (Cynodon dactylon – “kweek grass”) should remain vigorous and intact to ensure alien plants do not establish in the area. Thus, this spill presented not only a potential health hazard, but also a potentially negative ecological impact, which required immediate remediation in order to limit the possible spread of several diseases. Due to the urgency of this environmental contamination, a rapid response was required to neutralise the potential health threat. Historical research has indicated that sewage sludge soil contamination can be pasteurised by a pH-driven process through the addition of a coal ash, improving structure, fertility, pH and water holding capacity.
As a result, it was expected that due to the coal ash reactivity, the known pasteurising ability and soil health benefits, the sewage spill would be rapidly ameliorated and the organic compounds from the sewage and coal ash trace elements would be absorbed into the soil. Ash produced at Medupi Power Station is generated from a single coal source, offering an ash of uniform quality and consistency. The power station operates supercritical boilers, which run at higher temperatures and pressures than conventional coal-fired power stations. As such, a lower volume of coal is required in order to generate an equivalent power output, leading to lower carbon dioxide emissions. In addition, the ash produced contains a higher amorphous (glass) phase, causing it to be more reactive to both carbon and water (increased pozzolanicity).
Effectively, this means that once placed into the environment, the ash will dissolve and release its components more readily, therefore allowing a more rapid remediation response. .