OpenUCT :: Browsing by Author "Armitage, Neil P"

Browsing by Author "Armitage, Neil P"

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Open Access
Assessing the energy implications of exploiting stormwater, through artificial aquifer recharge, as an alternative water source in the Cape Flats, South Africa
(2018) Gobin, Aumashvini; Sparks, Debbie; Ahjum, Fadiel; Armitage, Neil P
South Africa has been facing challenges in both its energy and water sectors over the past few years. They are heavily dependent on each other and a better understanding of the linkages between the two sectors is crucial for sustainable development and planning in both sectors. While the water-energy nexus has been widely explored in developed countries, there is a limited amount of literature found on the significance of the nexus in South Africa. With the current critical drought in the region, alternative water sources are being considered by the City of Cape Town including seawater desalination, water re-use and abstraction of groundwater, to increase potable water supplies. The Cape Flats Aquifer represents a significant water resource for Cape Town and its yield can be further augmented by using artificial recharge with stormwater. Due to the location and water quality of the resource, several possible approaches have been identified for its exploitation. This study investigates quantitatively the energy implications of the three selected approaches in order to exploit the Cape Flats Aquifer as an alternative water source for Cape Town and further provides the potential carbon emissions from their respective energy usages. The three approaches consist of a Centralised Approach to treat the abstracted water for potable uses at two existing Water Treatment Plants (Blackheath and Faure); a Decentralised Approach to supply neighbouring suburbs with minimally treated water for non-potable uses through four proposed treatment plants and a Desalination Approach to treat brackish groundwater to potable quality at a proposed desalination plant. The energy implications of the approaches were evaluated using both direct energy usage during the abstraction, conveyance and treatment stages and the embodied energy of the consumables used during the treatment processes. These were then used to compare the shares of direct electricity intensities and embodied energy intensities of the alternatives at each stage to determine their viability. The individual stages' and overall energy intensities were quantified in form of the total energy required to produce a kl of treated water. The minimum energy required to abstract and convey the water was estimated using basic hydraulic principles. The energy usage at treatment plant levels was computed using the installed electrical capacities at the two existing water treatments for the Centralised Approach while the Decentralised Approach's demand was estimated by determining the treatment processes required to produce non-potable water, which is fit for usage. Energy requirements at the desalination plant were estimated using the salinity levels of the brackish groundwater and target salinity concentration of the treated water. The energy intensities of the approaches were then used as a basis to calculate the current and future electricity costs and their associated carbon footprints using the CSIR (2016) least cost scenario and the IRP (2016) base case future electricity mixes, as the higher and lower threshold for electricity generation costs and carbon emissions. The study found that the electricity intensities of all three alternatives depended significantly on the spatial layout of their respective systems, that is, the topography, distance and extent of their transmission networks. However, the embodied energy intensity of the Centralised alternative was found to be comparable to its electricity intensity, since more chemicals were to purify the water to potable levels. The Decentralised Approach's extensive pumped transmission networks contributed the most to its electricity intensity during the treatment process. The Desalination option was found to be the most energy intensive alternative, with energy intensities ranging from 7.41 to 9.62 MJ/kl, of all three options (1.16 to 1.57 MJ/kl for the Centralised Approach and 3.57 to 7.31 MJ/kl for the Decentralised Approach) and had the highest costs and emissions intensities, mostly caused by the country's coal intensive electricity mix. The Centralised option was found to be the least energy and carbon intensive of the three options and the most viable approach investigated. Desalination, nonetheless, can still considered as an alternative, given the issue of water scarcity, to increase water supplies. Despite its high energy demands, its carbon footprint could potentially decrease with a larger uptake of renewable energy technologies as sources of electricity. The importance of holistic planning across sectors was brought out quantitatively by using current and future water and energy mixes, providing valuable insights on the water-energy nexus, in this study.
Open Access
Development of the simple economic model (SEM) for stormwater management
(2011) Fisher-Jeffes, Lloyd N; Armitage, Neil P
Sustainable urban Drainage Systems (SuDS) are increasingly being implemented around the world. A common barrier to the wider use of SuDS in South Africa is the uncertainty regarding their total cost. The need for reasonable predictions of life cycle cost is vital, both in terms of ensuring the viability of the proposed projects as well as to allow for comparison with more conventional designs that have historically relied on concrete pipes and culverts to transport the stormwater to nearby receiving water bodies as quickly and efficiently as possible.
Open Access
The impact of unwashed aggregate on water quality emanating from permeable pavements
(2016) Biggs, Benjamin; Armitage, Neil P; Winter, Kevin
Sustainable Drainage System (SuDS) technologies set out to mitigate the adverse effects of urban stormwater runoff, through a multi-objective approach. Permeable pavement systems (PPSs) are one of the most widely-adopted SuDS technologies in South Africa. South Africa is a water scarce country and the sustainable provision of water to its citizens is one of the most significant challenges facing the country. The demand on the potable water supply system could potentially be alleviated by substituting stormwater for potable water in a 'fit for purpose' manner. A Water Research Commission (WRC) pilot study is attempting to provide locally-relevant data on the treatment efficacy of PPS for possible use in stormwater collection, treatment and storage. A laboratory experiment comprising four separate units was set up to determine the capability of various different PPS designs to reduce selected pollutants from stormwater for South African conditions. Permeable concrete block pavers of the type commonly used in the City of Cape Town (CoCT) area were laid over four different layer-work options, one in each unit, using aggregate largely collected from stockpiles used to construct a nearby PPS in a parking area at the University of Cape Town. In the first phase of the experiment - the 'flushing phase' - clean tap water was applied to each unit over a period of time in quantities roughly representative of a typical rainy season in the CoCT and the discharge was collected and analysed. The measured parameters included: orthophosphate, ammonia, suspended solids, pH and conductivity. After the initial approach proved insufficient for flushing purposes, an accelerated flushing process was then implemented to prepare, as far as reasonably possible, the unwashed in-situ aggregate for the next phase of testing. The second phase examined the pollutant retention capacity of each PPS by comparing the concentrations of various pollutants before and after treatment. However, due to the unforeseen delayed release of the pollutants from the aggregate, the attempted flushing of the insitu stone again proved insufficient for flushing purposes. The pollutants continued leaching into the effluent showing an excess of the flushing volumes applied and thus the treatment efficacy results after the accelerated flushing were contaminated. Nonetheless, these findings provide useful insights for stormwater practitioners and indicated that failure to adhere to accepted international practice with respect to the washing of the aggregate prior to construction and the prevention of the ingress of dirt into the pavement layers during construction, have an adverse impact on the treatment performance of PPS. Therefore, the selection of base materials, in particular, the use of unwashed aggregate and the variation of the treatment layers and the layer material, affect the treatment performance of the permeable paving system and can pollute storm runoff passing through the PPS substantially for an extended period of time. Further research is needed to: determine suitable flushing methods when PPS are constructed with unwashed aggregate; and conduct additional laboratory testing using pre-washed stone to assess treatment efficacy of design variations. Thereafter, suitable fit-for-purpose applications for the treated effluent can be recommended. Keywords: Permeable pavement, stormwater harvesting, Sustainable Drainage System (SuDS), treatment efficacy, pollutant retention, fit for purpose, South Africa, unwashed aggregate.
Open Access
Quantifying stormwater pollutants and the efficacy of sustainable drainage systems on the R300 highway, Cape Town
(2017) Robertson, Abby Jane; Armitage, Neil P; Zuidgeest, Mark
Stormwater provides a direct link between urban infrastructure and the urbanised natural environment. In particular, highway drainage presents a high risk of pollution when compared to other urban land use areas (Ellis et al., 2012); introducing heavy metals, suspended solids and hydrocarbons to urban waterways. This research investigated runoff from the R300 highway, located in the greater Cape Town area. The City of Cape Town Management of Urban Stormwater Impacts Policy requires the treatment and attenuation of stormwater from developments within the city, and proposes Sustainable Drainage Systems (SuDS) as a means to achieve this (CSRM, 2009b). SuDS are structural and process controls that attenuate surface drainage, improve runoff water quality, provide amenity and deliver ecosystem services. This study characterized the R300 runoff through a sampling program and modelling exercise in order to provide an indication of the ability of SuDS to manage highway runoff in South Africa. Sediment and runoff samples were collected from the road surface and an undeveloped parcel of land adjacent to the highway. The sampling results showed that heavy metals, suspended solids and phosphorus are present in significantly greater concentrations in road runoff compared to rainwater from the same area. The concentration of aluminium, copper, lead, zinc and phosphorus exceed the Department of Water and Sanitation's water quality guidelines for aquatic ecosystems in excess of 1000%. The concentration of heavy metals, phosphorus and fats, oils and greases was significantly greater in road sediment compared to sediment from the surrounding area. Barring copper, all contaminant concentrations in the road surface sediment are less than the maximum concentration required to protect ecosystem health. The R300 rainfall-runoff response was modelled in PCSWMM to evaluate the performance of SuDS such as infiltration trenches, bioretention areas and swales for managing highway runoff in terms of quantity and quality. The modelling exercise showed SuDS to be a viable means to attain the City of Cape Town's stormwater objectives, provided that SuDS are implemented in treatment trains along the entire road length.
Open Access
Stormwater harvesting: Improving water security in South Africa’s urban areas
(2017) Carden, Kirsty; Armitage, Neil P; Winter, Kevin; Fisher-Jeffes, Lloyd
The drought experienced in South Africa in 2016 – one of the worst in decades – has left many urbanised parts of the country with limited access to water, and food production has been affected. If a future water crisis is to be averted, the country needs to conserve current water supplies, reduce its reliance on conventional surface water schemes, and seek alternative sources of water supply. Within urban areas, municipalities must find ways to adapt to, and mitigate the threats from, water insecurity resulting from, inter alia, droughts, climate change and increasing water demand driven by population growth and rising standards of living. Stormwater harvesting (SWH) is one possible alternative water resource that could supplement traditional urban water supplies, as well as simultaneously offer a range of social and environmental benefits. We set out three position statements relating to how SWH can: improve water security and increase resilience to climate change in urban areas; prevent frequent flooding; and provide additional benefits to society. We also identify priority research areas for the future in order to target and support the appropriate uptake of SWH in South Africa, including testing the viability of SWH through the use of real-time control and managed aquifer recharge.
Open Access
Sustainability index for integrated urban water management (IUWM) in southern African cities : case study applications : Greater Hermanus region and Maputo City
(2007) De Carvalho, Sheilla; Armitage, Neil P
The critical situation in the water sector continues to jeopardize developmental principles and undermine strategies for poverty eradication. On the assumption that the failure in service provision can be largely attributed to an inability to holistically address all aspects of urban water management, a systems approach was used to develop a relevant and robust sustainability index which assesses the capacity of a city or a portion thereof to be sustainable. This thesis details the process of developing the Sustainability Index (SI) for a multidimensional assessment of urban water systems. In this research, an analysis of the current problems facing developing cities, particularly in Sub-Saharan countries, was undertaken. This was done so as to provide some insight into the current developmental issues hindering sustainable development. An examination of the urban water cycle was also carried out to illustrate the links within the cycle and between the various water uses and services. A process model was developed which addresses the multi-dimensionality of sustainability and the dynamism of urban water systems. This model combines aspects of the iterative procedure for assessing environmental sustainability introduced by Lundin et al. (2002) with the step-wise process proposed by Nardo et al. (2005).
Open Access
The viability of rainwater and stormwater harvesting in the residential areas of the Liesbeek River Catchment, Cape Town
(2015) Fisher-Jeffes, Lloyd Norman; Armitage, Neil P
The sustainable provision of water to South African citizens is a significant challenge facing the country. In order to avert a crisis, municipalities will need to reduce their reliance on traditional water sources. Rainwater harvesting (RWH) and stormwater harvesting (SWH) are two alternative water resources that could supplement traditional urban water supplies. To date, the potential benefits of RWH and SWH within an urban setting have not been adequately considered or investigated in South Africa. The only way to quantify the benefits and potential viability of rainwater and stormwater harvesting was to select and model a representative catchment - the Liesbeek River Catchment, Cape Town South Africa was selected. An Urban Rainwater Stormwater Harvesting Model was developed to model the use of RWH and SWH in the catchment. Additionally, a Storm Water Management Model (SWMM) of the catchment was developed to investigate the stormwater management benefits of RWH and SWH. The study found, inter alia, that: RWH was viable for only a minority of property owners; climate change would have limited impact on the performance of RWH systems; and RWH is an unreliable - even for small storm events - means of attenuating peak flows. On the other hand, SWH has the potential to reduce potable water demand in the Liesbeek River Catchment by up to 20%. However, for SWH to be viable there would need to be a high level of adoption by residents, at least for non-potable uses such as flushing toilets and outdoor irrigation. SWH is also of benefit in the attenuation of peak flows during storm events. Finally, the research found that the implementation RWH and SWH together would be unwise, as both are most cost-effective under conditions of maximum demand. The study concluded that SWH could be a viable alternative water resource for urban residential areas in South Africa - depending on the scale at which it is implemented, the end use for which it is utilised, and the population density that drives the water demand. RHW, on the other hand, has limited potential - depending on climatic conditions; it may, for example, be viable in areas with year-round rainfall.
Open Access
The viability of using the stormwater ponds on the Diep River in the Constantia Valley for stormwater harvesting
(2017) Rohrer, Alastair, R; Armitage, Neil P
Harvesting stormwater to supplement water demands has attracted a growing interest in South Africa as concerns over the security of the country's water supply increase. Whilst stormwater harvesting has been shown to offer a viable alternative water resource, there are often concerns about its storage requirements due to space constraints in urban areas. Stormwater ponds offer a potential solution to these concerns. Since stormwater ponds are typically designed for the sole responsibility of attenuating the periodic peak stormwater flows that are associated with large storm events, they often remain underutilised. By introducing Real Time Control (RTC) systems to operate stormwater pond outlets, ponds could potentially be used to store stormwater. This could increase the benefits that stormwater ponds provide as well as offer a viable alternative water resource. To investigate the economic viability of harvesting stormwater from existing stormwater ponds, a case study was performed on a representative urban catchment – the Diep River subcatchment, located in Cape Town, South Africa. The catchment contains seven stormwater ponds, which could be retrofitted for harvesting purposes. Sixteen different stormwater harvesting scenarios were developed that modelled various non-potable demands in the vicinity as well as different storage and harvesting arrangements, created using RTC strategies, of the catchment's existing ponds. These scenarios were modelled using an assortment of modelling tools which include: a catchment stormwater model; water distribution network models; and a Life Cycle Cost Analysis (LCCA). The economic viability of harvesting stormwater from the Diep River subcatchment's stormwater ponds was most susceptible to the cost of the system's water distribution infrastructure. Consequently, stormwater harvesting was most economically viable if used to supply toilet, clothes washing and irrigation demands to residential properties situated in close vicinity to the system's harvesting pond as this minimised the extent of the water distribution network. The results also revealed that distributing storage amongst ponds situated throughout the catchment is an effective method of increasing the volume of stormwater a stormwater harvesting system could yield without reducing its economic viability. However, this is on the condition that the system only extracts stormwater from the most downstream pond in the catchment. Importantly, the study also revealed that the attenuation of peak flows of large storm events (up to 1-in-20 year return period), achieved when harvesting stormwater from the existing stormwater ponds would be comparable to what the ponds currently provide. The study concluded that harvesting stormwater from existing stormwater ponds is potentially viable. It also demonstrated an effective method to maximise a catchment's storage capacity using distributed storage. For stormwater harvesting to be viable however, stormwater should be used to supplement a large percentage of non-potable end-uses and requires significant uptake amongst catchment residents.
Open Access
'What is to be sustained for whom?': Equity as a key to sustainable sanitation in South African informal settlements
(2016) Pan, Sophia; Armitage, Neil P; Van Ryneveld, Mark
Universal access to sustainable and equitable sanitation is a Sustainable Development Goal on the 2030 Agenda for Sustainable Development. The South African government has taken strides to try and meet both international and domestic development goals with its Free Basic Sanitation policy, for which a national implementation strategy was developed in 2008. Although the policy was formulated at a national level, municipal governments are delegated the authority to ensure service delivery at the local level. Municipalities have adapted and interpreted the policy to suit their own contexts. In particular, they have attempted to address the challenge of providing sanitation services to informal settlements using different approaches with varying degrees of success and often without explicit consideration or guidance for how to incorporate sustainability and equity principles. The aims of this thesis are thus to explore how the concepts of sustainability and equity can be applied to improve municipal sanitation services in South African informal settlements and to explore how various dimensions of sanitation and equity relate to sanitation. A comparative case study method using the lens of sustainability and equity was used to critique the approaches to providing sanitation services to informal settlements in three of South Africa's largest municipalities: eThekwini (Durban), Johannesburg and Cape Town. Each municipal case study incorporated an embedded case study that was used to examine sanitation services in selected informal settlements at a programme, project or settlement level. Primary data was collected using interviews and field visits. Secondary data was obtained from national and municipal records such as water and sanitation department reports, census data from Statistics South Africa, and municipal geographical information system databases. Findings from the thesis indicate that there is a need to better incorporate multiple stakeholders' perspectives on what sustainable and equitable sanitation services should be like. Strengths and weaknesses of each municipality's approach to sanitation service provision were compared and used to identify factors relating to sustainability and equity. A major conceptual gap identified in sanitation service delivery approaches is the need to emphasise equity as a core tenet of sustainability, especially in a socio-economic context of extreme inequality. This thesis makes a contribution towards knowledge by highlighting the importance of equity to support sustainable sanitation service delivery in South African informal settlements, adding new perspective into different dimensions of equity in sanitation and a suggested framework for how they could be incorporated into M&E practices.

Browsing by Author "Armitage, Neil P"

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