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Subject: search.filters.subject.Water quality

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    Development of a multi-criteria decision-support tool for improving water quality to assist with engineering infrastructure and catchment management
    (2024-05) Ngubane, Zesizwe; Sokolova, Ekaterina; Stenström, Thor-Axel; Dzwairo, Bloodless
    Research combining water quality modelling, quantitative chemical/microbial risk assessment, and stakeholder engagement to prioritise catchment areas facing water pollution problems to devise effective pollution mitigation strategies are limited. This research therefore aimed to address this gap by providing a practical and comprehensive framework that supports wellinformed decision-making processes in water pollution alleviation. By integrating multiple criteria and catchment aspects, this framework can assist infrastructure, operational, and ecological managers within a catchment in prioritising best management practices (BMPs) to reduce pollution and mitigate against potential resultant impacts. Given this context, uMsunduzi catchment, in KwaZulu-Natal, South Africa was chosen as a study site. UMsunduzi River is a major tributary of uMngeni River that is used for water supply to the cities of Pietermaritzburg and Durban. The study begins with the data synthesis from diverse sources of scientific data to identify chemical and microbial hazards, utilising a water quality modelling tool to map point and nonpoint source pollution in the catchment. The assessment encompasses the presence of pathogens such as Cryptosporidium and Escherichia coli (E. coli) in the catchment, with rural areas showing a greater contribution from animal sources, while urban areas are affected by impaired wastewater infrastructure. Quantitative microbial risk assessment (QMRA) was conducted, assuming no water treatment within the catchment. The investigation considered multiple exposure routes, including domestic drinking and recreational activities for both adults and children. The results indicate that the probability of infection from Cryptosporidium and E. coli exceeds acceptable levels set by South African water quality guidelines and the World Health Organization. The assessment further included a chemical risk assessment on various chemical groups, including organochlorinated pesticides (OCPs), pharmaceuticals and personal care products (PPCPs), heavy metals, nitrates, and phosphates. Elevated carcinogenic risks were observed for most OCPs, while noncarcinogenic pesticide effects pose long-term risks. Heavy metals and PPCPs are within sub-risk levels, but phosphates have notable ecological and health impacts, particularly in Inanda Dam, a key source of potable water for Durban. In this study, a unique contribution is made by incorporating both chemical and microbial risk assessment. Furthermore, the risk assessment methodology not only encompasses various chemical pollutants and exposure pathways but addresses the nuanced issue of water consumption variability between children and adults. To address these identified risks, a multi-criteria decision analysis methodology is employed to engage stakeholders in the risk management process. Affected, involved, and interested stakeholders, along with economic, environmental, and social criteria, contribute to the selection of Best Management Practices (BMPs). The Simple Multi-Attribute Rating Technique for Enhanced Stakeholder Take-up (SMARTEST) is utilised to identify suitable interventions. The study culminates in the recommendation of BMPs that aim to change behaviour, including public education on livestock grazing management, safe medication disposal, and responsible fertilizer and pesticide use. Pollution management measures, such as solid waste control and river cleanup, are suggested, along with infrastructure management improvements, like sewer system maintenance. This research strived to bridge the gap in water pollution alleviation by presenting a practical and comprehensive framework designed to support well-informed decision-making processes. This framework, with its integration of multiple criteria and considerations, stands poised to aid infrastructure, operational, and ecological managers within a catchment in prioritising BMPs aimed at reducing pollution and mitigating resultant health impacts.
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    Treatment of industrial effluent using specialized, magnetized coagulants
    (2023-05) Sibiya, Nomthandazo Precious; Rathilal, Sudesh
    The rapid degradation of water quality caused by industrial effluent presents a significant threat to public health and the ecosystem. This necessitates ecologically sustainable solutions through the coagulation treatment method. Coagulation with chemical coagulants (e.g. alum) is costeffective, but comes with non-recoverability, health and environmental risks. As a result, this study proposes a magnetic-coagulation separation technique as an alternative. Against this brief, the goal of this research was to produce specialized magnetic coagulants for the treatment of industrial wastewater. Three magnetized coagulants (MCs) viz. chitosan magnetite (CF), eggshell magnetite (EF), and rice starch magnetite (RF) were synthesized via the co-precipitation technique by using chitosan, eggshell, or rice starch with Fe3O4 nanoparticles (F) in three distinct ratios (1:2, 1:1, and 2:1). The analytical results via the Fourier-transform infrared (FTIR) spectroscopy, Brunauer– Emmett–Teller (BET) analyzer, X-ray diffraction (XRD) analyzer, and scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) spectroscopy respectively affirmed the success of MCs functional and molecular properties, surface area, crystal structure, surface morphology, and elemental compositions. Following that, a series of investigations were carried out utilizing coagulation and dissolved air flotation (DAF) methods to investigate the application and treatability performance of the MCs. Amongst the MCs, the RF(1:1) was found to be the most successful, removing over 75% of the turbidity, total suspended solids (TSS), and over 50% of the chemical oxygen demand (COD) from a local industrial effluent. Furthermore, response surface methodology (RSM) based on a Box–Behnken design (BBD) was used to optimize and compare the coagulation and DAF methods. With coagulant dose (2 – 4 g), settling/flotation time (10 – 60 min) and mixing rate (50 – 150 rpm), the optimum coagulation conditions of 4 g dose, 30 minutes of settling time, and a mixing rate of 50 rpm, achieved a desirability of 87.20%. A 15-min flotation time, with a mixing rate of 50 rpm, and a coagulant dose of 4 g resulted in 77.4% desirability in the DAF method. The DAF method was considered to be more favorable with a shorter settling/flotation time and a desirability of 75% with 95% confidence. Notably, the RSM-BBD models demonstrated a strong correlation (0.9 < R 2 < 1) with predicted results that were consistent with the experimental data. The recent findings indicate that the prospects of MCs are possible for wastewater treatment, and hence magnetic separation technology should be given consideration in water and wastewater treatment settings.
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    Green roofs and stormwater runoff quality in the urban landscape in South Africa
    (National Research Council Canada, 2021-06-20) Sucheran, Arisha; Sucheran, Reshma
    A number of sustainable urban drainage systems (SuDS), such as green roofs, are being developed and implemented in cities around the world to help reduce stormwater runoff and improve stormwater runoff quality. This study compares the water quality of green roofs with that of conventional roofs in the eThekwini region, South Africa. Samples of stormwater runoff from the different green roof systems on the eThekwini Green Roof Pilot Project were collected to test their level of contaminants and pollutants. The tests focused on all physical, aesthetic, chemical, and microbiological determinants pertaining to stormwater runoff. For all tests, the level of contaminants and pollutants were measured against the South African Water Quality Guidelines Volume 7 for Aquatic Ecosystems. The data revealed significant variations in pollutant concentrations between the green roofs and the conventional roof. Moreover, runoff water quality varied across the various roof types, which may indicate that the substrate composition has the greatest impact on green roof performance regarding rainwater quality. Overall, the results suggest that these green roof systems do not have the ability to filter pollutants out of stormwater runoff, but rather increase their levels of concentration.
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    Hydrological characterization of twelve water catchments in Nigeria
    (AJER, 2014-01) Afolayan, S.O.; Adeyemo, Josiah; Otieno, Fredrick Alfred O.; Ojo, Olumuyiwa I.
    Twelve water catchments (WCs) in Ogbomosho, south west of Nigeria were evaluated for their hydrological characterization with respect to domestic and irrigation activities. Both physiochemical and biological parameters (limnological properties) were determined which include pH, total alkalinity (TA), CO32-, HCO3-, NO3-N, SO42-, N, P, K, Na, Ca, Mg, dissolved oxygen (DO), electrical conductivity (ECw), biochemical oxygen demand (BOD), total solids (TS), total dissolved solids (TDS), chlorophyll a,b,c and phaeophytin. Temperature fluctuation of the water catchments was measured in-situ to avoid samples coming into contact with the surrounding air using mercury in glass thermometer. Soil samples collected from the bottom of the water catchments were determined for chemical properties such as N, P, K, Na, Ca, Mg, and SO4-2 following recommended procedures. These parameters were investigated based on the perceived research consent of their efficacy in characterizing water catchments hydrologically along safety and pollution divides. The limnological properties were configured into ranking compared with standards to evaluate the degree of contamination or suitability of the WCs for domestic and irrigation purposes. Results obtained indicated pH values of the catchments ranging from 5.8 to 7.4 with corresponding TA between 0 and 296 mgL-1 suggesting high level of dissolved carbon dioxide (DCO2) and traces of untreated wastewater in most of the catchments. Based on ranking of the limnological properties of the WCs, WC4, WC5, WC6 recorded indices between 65 and 95 signifying that cumulatively these three WCs were more prone to pollution and could affect human health at consumption while WC2, WC3, WC 7 and , WC 10, aligned between 95 and 120 indicating mild to medium pollution and WC1, WC 11, and WC 12 oscillated between 120 to 145 picturing WCs approaching standards (132) while WC8 ranged between 145 and 170 revealing WC 8 as catchment with little or no tendency for hazards at drinking. Similarly, WC2, WC8, recorded soil reference (SR) between 50 and 60 suggesting possible interference of organic decomposition between the soil stratum and water in the catchment, however, WC1, WC4, WC5, WC6, WC7 and WC 12 recorded SR between 40 and 50 showing possible adjustment of the soils in the WCs of various salinity levels and WC 3, WC9, WC 11 revolving between 30 and 40 projecting the WCs with minimal pollution. Moreover, WC 10 only recorded value between 20 and 30, an inference of the soil stratum void of absolute contamination. Generally, WC2, WC8, appeared polluted both in limnological properties and basic soil conditions while WC9, WC10, WC11, and WC3 reflected high scale of ranking on limnological properties with low scale of SR possibly indicating little or no interaction between the soil base and the water in the catchments. Contrary wise, WC6 was high in SR but low in limnological properties. This trend suggests the presence of oxygen saturation in some of the WCs. Overall results indicated that WC4, WC5, WC6 require major water treatment prior to its usage for irrigation to avoid salt deposition at the crop root base, while WC2, WC3, WC7, WC9 and WC10 were considered relatively safe for drinking. WC1, WC11, WC2 requires some measure of precaution before drinking, however, WC12, and WC 8 could be consumed with little or no fear of infection.