Civil Engineering

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Development of an automation model for leakage reduction and energy harnessing through optimised placement and setting of pressure reducing valves and pump as turbine placement in water distribution networks.
(2021) Pillay, Ethan.; Adu, Joy Tuoyo.; Kumarasamy, Muthukrishna Vellaisamy.
Water leakage is of paramount interest in South Africa. Due to the increasing population density access to drinking water will be scarcer, as much of the water produced is lost through leakages. South Africa’s non-revenue water (NRW) accounts for approximately 30% of the total water supply, with leakages accounting for more than 70% of NRW in a network. Water leakage losses are defined as water lost during transportation to the consumer from the water source. Reducing leakage losses in existing networks is a major task for engineers, as replacing pipes is costly. There is a direct relationship between the pressure in a water distribution network (WDN) and the network’s leakage losses. Network pressure is affected by many factors such as consumer demand, nodal elevation differences and network characteristics. The easiest and most cost-efficient method of pressure reduction in existing WDNs is through efficient pressure management. Developing methods to reduce the excess network pressure will reduce the leakage losses in the network. There is currently little research that incorporates optimising pressure-reducing valve (PRV) placement to regulate network pressure and reduce leakage losses. Furthermore, the use of pumps operating as turbines (PATs) to harness energy in WDNs has not been fully explored. Literature gaps encompass optimising and automating these processes and creating an algorithm applicable to complex WDNs. This dissertation presents a new optimisation model aimed at minimising network leakage losses within a WDN by determining the optimal placement and setting of additional PRVs. Energy generation from excess pressure is a secondary benefit and by-product of pressure reduction and can be harnessed by replacing PRVs with PATs. Replacing PRVs with PATs to harness renewable energy from the WDN is also incorporated into the new optimisation model. Automation of the model has been achieved using MATLAB and EPANET. The objectives of this study are to create a mathematical model to optimise the placement and setting of additional PRVs within a WDN, following all hydraulic, mathematical, and linear constraints. The model must determine which PATs can feasibly replace PRVs within a WDN to generate electricity and the PAT’s potential power output and potential gross margin. The mathematical model must be automated using MATLAB and EPANET. The newly created objective function is made up of two stages to account for the multiple objectives. The model has been applied to two real-world networks: the Cornubia Integrated Human Settlement Development Phase 2A- Zone 1 network and the Pat Marshal Housing Project. The proposed methodology’s ability to reduce network pressures, reduce associated leakage losses, and generate energy has been demonstrated. The network leakage losses minimisation accounts for the hydraulic characteristics and constraints of each WDN in the form of mass continuity equation constraints at the nodes, momentum balance constraints along the pipes, network constraints, and pressure reducing equipment constraints. Five successful additional PRVs have been optimally placed and set within the Cornubia WDN, achieving a 12.8011% leakage rate reduction. Two successful additional PRVs have been optimally placed and set within the Pat Marshal WDN, achieving a 27.907% leakage rate reduction. The model has determined that nine of the 36 PRVs in the Cornubia WDN can be feasibly replaced by PATs to harness 135.48 kW of energy, equivalent to a Mini-hydropower plant, with a 948.67 MWh per annum output. One PAT can feasibly replace a PRV in the Pat Marshal WDN to harness 24.55 kW of energy, equivalent to a Micro-hydropower plant, with a 131.6 MWh per annum output. The energy produced could be sold to realise gross margins of approximately R920 211.17 and R127 662.30 per annum for the Cornubia and Pat Marshal WDNs, respectively. The results obtained from the newly proposed method are positive, significantly reducing the leakage rate in both networks. The excess pressure from the networks can be efficiently harnessed to generate renewable energy to be utilised or sold.
Feasibility of run-of-river hydropower for rural and agricultural productivity in South Africa.
(2021) Makalima., Lazola Qhawe Mfundo.; Adu, Joy Tuoyo.; Kumarasamy, Muthukrishna Vellaisamy.
The Southern African Community Development (SADC) intends to increase its irrigated area to increase the agricultural productivity of the land. Run-of-river hydropower systems present an attractive solution of providing energy where it is not feasible for alternative energy sources and extend the grid infrastructure to improve the livelihood of rural communities and increase agricultural productivity. The site geographical location and topography of power plants have made it impossible to guarantee fixed costs from suppliers and manufacturers, leading researchers to develop formulae that predict the cost behavioural tendencies of the electro-mechanical components of the power plant as a function of hydropower parameter inputs and other costs. Hydropower systems are very site-specific as they are affected by their geographical location and the site's topography. The difficulties from suppliers and manufacturers in failing to guarantee fixed costs have resulted in designers using developed formulae to determine the scheme's costs. This investigation aimed to develop a model that would allow designers to determine whether run-of-river hydropower would be feasible or not for a specific location in South Africa. This was achieved through a pre-feasibility model based on a '3 Pillar Concept' of social, environmental, and economic test for sustainability, which according to research, has 49 sustainability indicators for run-of-river hydropower systems measured directly or indirectly. The Levelised Cost of Electricity (LCOE) from hydropower was used to determine the economic feasibility of hydropower systems. From previous research, LCOE evaluation for small hydropower projects in developing countries ranged between 0.02USD/kWh and 0.10USD/kWh, making small scale hydropower systems very cost competitive for electricity generation to the grid or schemes for off-grid rural electrification. Run-of-River hydropower systems are classified as small hydropower systems and generate from 1MW to 20MW. The projects demonstrated in this report were Micro and Mini hydropower systems which are significantly larger than Pico hydropower systems. The sites selected for the study are U2H014 located downstream of Albert Falls dam, U3H005 downstream of the Hazelmere dam, U2H052 downstream of Inanda dam, and V1H002 downstream of Woodstock dam. The potential power of the available energy was quantified using available streamflow data. Flow duration curves were developed from streamflow data and were used to develop power duration curves for the hydropower plants. LCOE for the investigated sites ranged between 0.02USD/kWh and 0.10USD/kWh. The power duration curves showed that the smallest power plant was U3H005 and generated 48kW. The groundwater pumping requirements for rural and agricultural productivity is found to be 31.1kW. Results obtained at sites U2H014 and V1H002 were 238kW and 314kW, respectively. The smallest power plant could generate enough power for rural and agricultural productivity with power savings that could be sold to the grid or power the community. The results obtained at the sites were positive and acceptable.
A mathematical model development for simulating in-stream processes of non-point source pollutants.
(2018) Adu, Joy Tuoyo.; Kumarasamy, Muthukrishna Vellaisamy.
In coming years, chronic water stress is inevitable owing to the unavailability of fresh water. This situation is occasioned by rapid urbanisation, climate change, rising food demand, and production. The increasing rate of water scarcity associated with water pollution problems, makes water quality management an issue of great concern. Rivers owe their existence to the relationship of rainfalls, soil properties and land use within a catchment. The entire hydrological processes that occur in the catchment area has a direct effect on occurrences and quality of the rivers there-in. A principal part of the hydrological cycle is runoff generation. Runoff characterises soil erosion, sediment transport, pollutants and chemicals all otherwise referred to as non-point source pollutants and released into water bodies. Most non-point source pollutants are generated from agricultural fields, informal settlements, mining fields, industrial areas, and roads. These sources produce increased nutrient concentrates (sewage effluent from informal settlements and fertilisers from agricultural fields) and toxic substances which alter the water quality in uncertain quantities. This affects aquatic biota and ultimately human health negatively. Non-point source pollution is a major source of water quality degradation globally and is the single most significant threat to subsurface and surface sources of usable water. Developed countries, unlike many developing countries, have long sought ways to stop the release of non-point source pollution directly into natural rivers through the establishment of best management practices but unfortunately with little success in actual practice. Numerous non-point source models exist which are basically watershed based and are limited to simulate the in-stream processes of non-point source pollution in water channels. Most existing non-point source models are site-specific, cumbersome to manipulate, need high-level operational skills and extensive data sets. Consequently, these models are difficult to use in areas apart from where they were developed and with limited data sets, as is the case with developing countries. Hence, to develop a non-point source pollution model that would adequately and effectively, simulate non-point source pollution in water bodies, towards restoring good river health is needed. This is required to enhance the proper monitoring and remediation of water sources affected by Non-Point Source Pollution especially in areas that have scarce data. Using the concept of the Hybrid Cells in Series model in this study, a hydrodynamic riverine Non-point source pollution model is conceptualized to simulate conservative pollutants in natural rivers. The Hybrid Cells in Series model was conceptualized to address the limitations identified in the classical advection dispersion model which is the foundation for all water quality modelling. The proposed model is a three-parameter model made up of three zones, which describes pure advection through time delay in a plug zone, and advection and dispersion occurring in two other thoroughly mixed zones linked in sequence. The model considers lateral inflow and pollutant loading along the river reach in addition to the point source pollutant entry and flow from upstream stations. The model equation for water quality along with hydrodynamic equation has been solved analytically using Laplace Transform. The derived mathematical formulation is appropriately coded, using FORTRAN programming language. Other components such as hyporheic exchange process and first order kinetic reaction simulations are incorporated to the proposed model. The response of these models matches the numerical solution of the classical Advection Dispersion Equation model satisfactorily when compared. The potential of the proposed model is tested using field data obtained from verifiable existing literature. A performance evaluation at 95 percent confidence is carried out. The correlation results of the observed and simulated data are seen to be in good agreement. The breakthrough curves obtained from the proposed model shows its capability to simulate Non-point source pollution transport in natural rivers effectively. The simplicity of the Hybrid Cells in Series model makes it a viable model for simulating contaminant transport from non-point sources. As the model has been validated using recorded data collected from the field for a specific tracer injection event, it is imperative to carry out investigation on changes in model parameters before, during and after storm events. However, this study adequately addressed and attempted to develop, validate new model components for simulating non-point source pollutant transport processes in stream.
The optimisation of baffle arrangements for minimal sediment washout in standard stormwater sumps.
(2022) Paideya, Leshalen.; Adu, Joy Tuoyo.; Kumarasamy, Muthukrishnavellaisamy.
Sediment in stormwater drainage systems is a matter of great concern due to its ability to collect within stormwater pipes to form blockages. Furthermore, sediments transport harmful pollutants, depositing them in stormwater discharge areas and disturbing the ecology of those areas. Standard stormwater sumps are a reliable and cost-effective solution to trap and retain sediment within stormwater drainage systems for manual removal. However, under high flowrate and fine sediment conditions, the effectiveness of standard sumps drastically decreases. A solution to this issue is the installation of baffles that can be retrofitted into the standard sump as a method of reducing flow velocities to allow sediments to settle to the sump bed. An aspect of this solution, as equally important as sediment trapping, is the prevention of sediment washout. During a storm event, sediment previously trapped in a stormwater sump can be washed out before the routine cleaning period. Therefore, it is paramount to ensure that the baffle arrangement effectively prevents the resuspension and washout of sediment already present in a standard sump. This dissertation investigates the use of baffle arrangements to minimise sediment washout in standard sumps and determine a baffle arrangement that will provide the best sediment retention results while remaining a feasible and practical solution in a real-world context. Three baffle arrangements, consisting of a combination of solid and semi-porous baffle plates of varying dimensions placed in different orientations, were chosen for this investigation based on their previous success with sediment trapping. The primary methodology of this research compared the effectiveness of these baffle arrangements in minimising sediment washout by comparing them to a control setup with no baffles, using a simple mass-balance process. Additional experimentation involved using an Acoustic Doppler Velocimeter (ADV) to develop flow velocity fields to motivate the observations made in the mass-balance tests. All baffle arrangements performed better than the control setup, with the least effective of the three designs improving sediment retention efficiency by 22% and the most effective by 71.5% under the worst-case condition. These results were then dimensionally analysed to determine the results of such testing under real-world conditions. The results of this analysis were also promising, with the best baffle arrangement achieving retained effluent concentrations of up to 0.4 kg/m3 when calibrated for typical standard sump dimensions and peak flowrate.

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Browsing Civil Engineering by Author "Adu, Joy Tuoyo."