Browsing by Author "Jacklin, Dylan Michael"
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- ItemPlant biofiltration for urban stormwater runoff purification in South Africa(Stellenbosch : Stellenbosch University, 2022-04) Jacklin, Dylan Michael; Brink, Isobel; Jacobs, Shayne Martin; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: A major consequence of urbanisation is the large-scale conversion of pervious to impervious surfaces, which significantly alters the natural hydrological cycle in terms of both hydrology and quality. Together with climate change, urbanisation and the associated stormwater runoff are regarded as major threats to water resource security worldwide, due to the variety of pollutants generated and transported. Conventional urban stormwater management rapidly collects and transports runoff for discharge into the nearest watercourse, triggering a plethora of public and ecological health concerns. In response, the Water Sensitive Urban Design (WSUD) concept, of which plant biofiltration is a component, is increasingly preferred as a sustainable alternative to conventional systems as it considers stormwater as a resource to protect rather than a substance of which to dispose. Plant biofiltration promotes a spatial network of passive, ecologically sound treatment solutions to the diffused nature of urban stormwater pollution, for discharge into existing drainage systems or watercourses. South Africa, one of the most rapidly urbanising countries in Africa, experiences some of the worst environmental deterioration globally. Stormwater runoff discharge, together with aging and defective conventional treatment systems, threaten the country’s already limited freshwater resources. Therefore, the South African Water Research Commission seeks to promote the adoption of WSUD, thus representing a significant shift from the linear drainage strategy currently adopted at local level to a holistic management approach of the urban water cycle and its integration into urban design. Although the value of ecosystem services is increasingly recognised, WSUD and particularly plant biofiltration as one of its components, is under-utilised, as the current framework in South Africa only provides broad philosophical guidance lacking scientific premise for practical design considerations. Variable performances have been reported in standard and modified plant biofilters, stagnating treatment optimisation knowledge. The difficulty of plant biofilter optimisation stems from the complex pollutant removal processes, which vary between physical designs and operational conditions. Therefore, appropriate design demands that both engineering hydrology and the scientific functioning of natural elements be considered; however, the latter is not currently included in the training of the civil engineer who can be the professional responsible for plant biofilter planning and design. Furthermore, current plant biofilter models insufficiently account for design modification and its associated removal processes. Limited local research and design specifics are currently available, which has resulted in injudicious plant selection and erroneous plant biofilter design, inhibiting treatment performance and threatening the recipient site’s natural biodiversity. Thus, the main aim of this research is to advance knowledge in stormwater plant biofiltration for improved urban water management in South Africa. This research initially presents potential phytoremediators, plants for the in situ treatment of pollutants, which are indigenous to the Western Cape, South Africa, as an aid to the practicing engineer for use in local plant biofiltration initiatives. Although chosen plant species were from the local Western Cape area for logistic reasons (the University is situated in the Western Cape), the techniques presented to identify species are transferable to other biogeographic areas. Informed by this undertaking, a phyto-guide is developed for identifying novel phytoremediators, adept at adjusting to the recipient habitat’s dynamic conditions and further incentivised by South Africa’s extensive biodiversity. The initial approach to plant biofilter optimisation investigated four engineered materials as potential growth media amendments, promoting attapulgite combinations for use in small-scale stormwater biofilters in the spatially constrained urban area. Progressing with plant biofilter optimisation, nine indigenous South African biofilters were investigated as effective yet sustainable alternatives to exotic phytoremediators, and Prionium serratum, among others, was found to exhibit enhanced removal capabilities. Physically modifying the plant biofilter as the final component to optimisation, following growth media and plant species, showed that combining standard biofiltration techniques with upflow filtration, plenum aeration and anaerobic zone saturation is the most efficient solution; removing on average 96% of synthetic stormwater loads. The novel sequential modifications between designs highlighted pollutant-specific removal processes and proffered plant biofilter designs for optimised treatment performance. Empirical findings based on the data captured by the preceding investigations contribute statistical output for future local in-depth modeling endeavours. Additionally, in developing the conceptual deterministic plant biofilter model for stormwater treatment, possible applications of existing models for the various nutrient, and potentially heavy metal, removal processes are summarised. In conclusion, this research contributes physical design specifics and both experimental and mathematical models to urban stormwater treatment researchers and practitioners, constantly improving the understanding of plant biofilter complexity.
- ItemThe potential use of wetland plant species within a renosterveld setting for the phytoremediation of glyphosate and fertiliser(Stellenbosch : Stellenbosch University, 2018-12) Jacklin, Dylan Michael; De Waal, Jan; Brink, I. C.; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography & Environmental Studies.ENGLISH ABSTRACT: In South Africa, fertiliser and herbicide pollutants resulting from various agricultural practices lead to a degradation of surface freshwater and groundwater quality. Nitrogen and phosphorous, and glyphosate derived from agricultural fertiliser and herbicide applications, respectively, significantly contribute to watercourse toxicity. Adjacent to many of the surface freshwater systems are some of the South Africa’s most productive agricultural fields, which convert the surrounding natural ecosystems in favour of the crops produced. As a result, the degradation of natural vegetation and deterioration of freshwater quality is observed. The critically endangered status of some Renosterveld vegetation types is the product of agricultural expansion, nutrient loading through fertilisation and the spraying of herbicides. The characteristics of phytoremediation provide an attractive alternative for the pollutant biofiltration of freshwater aquatic ecosystems. A buffer of Renosterveld vegetation along river corridors may be a solution for agricultural pollutant remediation prior to entering the watercourses. As a result of its successful uptake and metabolism capabilities of fertilisers and herbicides, inexpensiveness, aesthetic advantages and long-term use, it has become a remediation technology of choice in developing countries. The utilisation of wetland plants occurring within Renosterveld vegetation for pollutant extraction from agricultural practices will increase river corridor biodiversity, creating indigenous refuges, and facilitating habitat connectivity. Considering this, the study aims to delineate the potential use of wetland plant species indigenous to Renosterveld for the effective removal of agricultural pollutants. The evaluation of plant species’ pollutant removal efficiency in comparison to unvegetated soil will substantiate its use in vegetative buffer strips. The potential use of indigenous species as an alternative to invasive alien plant (IAP) species, currently considered successful phytoremediators, will aid in conserving the Renosterveld ecoregion. An experimental phytoremediation system was designed and constructed under laboratory conditions to investigate the pollutant removal potential of indigenous vegetation. Five pollutant parameters, namely ammonia, nitrate, soluble reactive phosphorous and two glyphosate concentrations (0.7 and 225 mg/L), were selected to reflect environmental stresses on 14 indigenous wetland species. The high but non-lethal glyphosate dosage strength was selected by means of a dual species dilution series experiment, where two plant species were subjected to ten different glyphosate concentrations. The dosage strength was selected at a concentration where plants did not display signs of mortality. Effluent analyses indicated the exceptional removal efficiencies of the indigenous wetland species across both fertiliser and herbicide pollutants, with the two most beneficial species identified as the species selected for this test aquic Phragmites australis and Cyperus textilis. The unvegetated soil control further exhibited efficient pollutant removal. However, indigenous vegetation consistently displayed greater pollutant removal than the unvegetated soil control. When compared to the IAP and Palmiet (Prionium serratum) multi-plant community assemblage, the indigenous species indicated similar pollutant removal efficiencies, justifying the use of indigenous plant species over the alien invasive equivalent. Phytoremediation presented significant potential for the utilisation of non-invasive wetland plant species in agricultural pollutant remediation, ameliorating freshwater aquatic ecosystems, and aiding the conservation of the already fragmented landscape.