Theses and dissertations (Applied Sciences)
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Item Development of paper-based microfluidic strips for quantification of ammonia(2019) Nxumalo, Nonhlazeko Loveday; Mdluli, Phumlane S.; Madikizela, Lawrence MzukisiWater is one of the most valuable and crucial of life and therefore accurate monitoring and assessment of water resources for sustainability is imperative. Conventional water investigation includes manual gathering of tests, their transportation and resulting examination in the research center. This is time and labour-intensive, costly and requires exceptionally qualified personnel. Sovereign of this procedure empowers more continuous examination, sparing time and cash for analysts, ventures and administering bodies. Consequently, there is requirement for advancement of minimal effort ecological microfluidic paper-based expository gadget that is fundamental for compelling administration of our profitable water assets. This will address the huge and growing demand for low-cost ammonia sensors as legislation becomes more stringent and as more frequent monitoring becomes essential for legislative compliance. Subsequently, this thesis reports on the development of a low-cost, colorimetric, wax- printed microfluidic paper-based analytical device (µPAD) to detect ammonia in industrial wastewaters. Microfluidic innovation was utilized to facilitate the examination of analytes on the colorimetric explanatory techniques onto a convenient detecting gadget. This therefore empowers the blending of little volumes of analytes with synthetic reagents to form a coloured/hued product in the sight of the analyte of interest. The µPAD fabricated was an oval shaped pattern which was designed on Corel draw software. The hydrophilic segments were made by printing a chromatographic paper with hydrophobic paper sizing agents utilizing a standard Xerox wax printer (Xerox colorqube 8570). The quantification of ammonia in wastewater was performed on the µPADs using two typical colorimetric methods namely, Nessler reagent and Salicylate. The reaction of ammonia with the Nessler reagent resulted in a brown or intense yellow colour whereas with the salicylate method, the final colour was green. For both methods, the colour intensity increased proportionally with the analyte concentration, and all images of the μPADs were captured and colorimetrically analyzed with ImageJ software for quantification. The analytical performances of the µPAD were linear from 0 to 5 mg L-1 with a limit of detection of 3.37 mg L-1 and 3.20 mg L-1 for the Nessler vii reagent and salicylate methods respectively. The validity and accuracy of aforementioned methods was supported by the standard UV Visible spectrophotometric method and applied to the measurement of wastewater effluent samples. Wastewater samples were analyzed and the results obtained were similar to those obtained with a spectrophotometric method, demonstrating that the µPAD is suitable to determine ammonia in wastewater.Item Synthesis and characterization of membrane with molecularly imprinted polymers for selective adsorption of triclosan(2019) Mntambo, Siyabonga Aubrey; Mdluli, Phumlane S.; Mahlambi, Mphilisi MciniseliAmongst many tenacious emerging traces of lethal organic pollutants in wastewater, triclosan (TCS) is typically the often-encountered compound. This pollutant has been reported in the water circle, including surface water, wastewater treatment plants, groundwater, aquatic sediments and aquatic organisms and, to a lesser extent, drinking water, at levels in the nanograms to low micrograms per litre range. Triclosan mainly find its way into the human system through its extensive use in pharmaceutical industries over the recent years. Excessive exposure to this water pollutant may result in adverse conditions like hematological disorders such as blood cancer. Despite the variety of its negative effects, triclosan is still used as a preservative in many pharmaceutical personal care products (PPCPs), e.g. toothpaste, disinfectants, hand wash, cosmetics, soaps and medication. In light of the aforementioned applications, it is imperative to remove triclosan to accepted levels and find more efficient, low-cost and less energy consuming methods of its removal in order to counter the challenges of water scarcity in the country and its wastewater channels. In this study, a “fractionated approach” was used, as it accounts for the synthesis of selective polymeric membranes using a phase inversion by immersion precipitation technique. Hence, the quest to address these water challenges was through the application of polyvinylidene fluoride (PVDF) polymeric membranes for the removal of triclosan in effluent treatment plant (ETP) water. This was carried out by fabricating this polymer with selective micro composite particles called molecularly imprinted polymers (MIPs). This improved the mechanical behaviour and strength of the membrane. The MIPs were synthesised using a two-step bulk polymerisation process. The synthesized MIPs possess specific binding cavities within its structure. The PVDF membrane were functionalised with MIPs and were characterised using Scanning Electron Microscopy (SEM), for their morphological properties. Thermogravimetric analysis (TGA) was used to study their thermal behaviour and the Fourier transform infrared coupled with universal attenuated total reflectance (FTIR- ATR) was utilized to determine the functional groups present in the membrane. The dynamic mechanical analysis (DMA) was used to study the mechanical behaviour and strength of the membranes. The SEM images showed the equal distribution of micro particles on the membrane surface. The TGA analysis revealed that all the studied polymeric membranes were thermally stable up to an average temperature of 502°C. The FTIR-ATR analysis showed new absorption peaks that were brought by the functionalisation and revealed that the PVDF membrane does not interfere with the MIP chemical integrity despite being infused within the polymeric membrane. DMA revealed an improved stability and behaviour once the concentration of the additives was increased. Moreover, the water and porosity content percentage of the MIP infused PVDF membranes increased as the concentration of the adsorbent was increased. Wastewater samples were collected from an effluent treatment plant (ETP)and pre- treated before analysis. Experimental parameters such as sample size, contact time, stirring speed were optimised. The synthesised PVDF/MIP membranes had an adsorption efficiency of 97% TCS in membranes compared to PVDF/NIP and PVDF bare membrane which had 92%, 88%, respectively. This might be due to the effect of the binding sites of the additives. The analytical method had limits of detection (LOD) and limits of quantification (LOQ) of 0.22, 0.71 µgL-1 in wastewater effluent, respectively. The percentage recovery for the effluent samples was 68 %. The results obtained therefore shows that MIPs have the potential modifier for the development and continuous progress in PVDF membranes.Item Toxicity and biodegradability assays for hazardous landfill leachate and textile size effluents(2005) Rakgotho, Thabisile; Odhav, Bharti; Buckley, ChrisThe cumulative effects of pollution have led to increased public concern, which is resulting in strict legislation on the discharge of wastes in whatever state they are present, i.e. solid, liquid or gas. Currently, in South Africa, effluents with a high organic load are sent to landfills or marine outfall because the cost of discharge to sewer is prohibitive. In regions where there is a net surplus of rainfall, landfill sites have the potential to pollute the groundwater due to saturated soil conditions. Therefore, many landfill sites should not receive liquid effluents. If liquid wastes are disposed onto landfills, then an alternate sink is required for the treatment of the high volumes of leachate that are generated. These concentrated effluents could then be treated by biological, chemical or physical methods to reduce the pollution load in the natural water resources. In this study, anaerobic digestion has been identified as one of the biological processes that can be applied to treat high-strength or toxic organic liquid effluents, since a survey conducted by Sacks (1997) indicated that many anaerobic digesters in the KwaZulu-Natal region have spare capacity. However before high strength industrial wastes can be treated in existing anaerobic digesters, their impact on the digestion process, i.e. their toxicity and biodegradability under anaerobic conditions, needs to be determined. During this project, several high-strength or toxic industrial effluents were tested to assess their toxicity and biodegradability under anaerobic conditions. These include three synthetic textile size effluents from the textile industry (Textile effluent 1, 2, and 3) and three hazardous landfillieachates (Holfontein, Shongweni and Aloes). In addition, the components of a textile effluent, i.e., starch and wax, were tested to determine whichItem Detection and evaluation of the fate of estrogen endocrine disrupting chemicals in wastewater treatment(2014) Surujlal-Naicker, Swastika; Bux, FaizalAll over the world concerns have been raised over the possible adverse effects that may occur when exposed to chemicals that have the potential to interfere and affect the endocrine system. The concern is directed at both humans and wildlife. There is still a lack of public awareness regarding Endocrine Disrupting Chemicals (EDCs) and the harmful effects on humans and wildlife. It has only been within the last decade that South Africa began the actual task for proper management and control for water and wastewater quality. There are many ways to detect these EDCs all of which are very laborious and most of the cases these EDCs are either in the pico or nano gram per litre range, too minute for many methods to detect effectively; so therefore the research project aimed to use rapid and sensitive techniques to determine the quickest means to detect the very low concentrations of theses EDCs. Two techniques were researched, i.e., Enzyme Linked immunoassays (ELISAs) and Radio-immunoassays (RIAs). The research study thus assessed the solid phase extraction (SPE) technique for total recovery of hormones; the ELISA and RIA techniques for rapid detection of natural (estrone (E1), estradiol (E2) and estriol (E3) and synthetic ethinylestradiol (EE2) by validating the precision and reproducibility . These techniques were then applied to determine hormone EDC removal first at laboratory scale investigations and then applied to full scale wastewater treatment plants (WWTP) with different configurations in order to deduce removal efficiency of each type of plant. The next phase assessed the toxicity of individual and combined estrogen standards as well as the toxicity in the WWTPs and classify and to determine if there was a correlation between hormone concentration and toxicity in final effluents. The assessment of the SPE and the immunoassay procedures (ELISA AND RIA) using standards and controls found that both these assays can be utilised to quantify hormone estrogens in wastewater. The small sample volume required reduced the labour time and application of the procedure made it cost effective and reliable techniques. The intra-assay and inter-assay validation procedures as well as the standard recoveries confirmed reproducibility and precision of the immunoassays. The % CV were <10% for both the intra-assay and inter-assay validations. The laboratory scale investigations included the operation of a modified Ludzak-Ettinger (MLE) process which enabled control and manipulation over the operational parameters in order to establish how certain parameters influenced the removal of hormone EDCs. One such parameter that was manipulated was the sludge retention time (SRT). The MLE tests showed that the SRTs definitely have an effect on the removal of hormones from the influent as well as the overall performance of sewage treatment. The 10 day SRT proved that longer SRTs will definitely aid in the removal of hormones and possibly other EDCs in raw sewage. During the 10 day SRT the influent hormone concentrations (E1: 59.11 ng/L, E2: 61.40 ng/L) were almost double than the influent hormone concentrations (E1: 26.46 ng/L, E2: 27.60 ng/L) during the 5 day SRT, which impacted on the removal efficiency. The 5 day SRT had an overall average E2 and E1 removal of 78.11% and 81.71% respectively while the 10 day SRT had average E2 and E1 removal of 91.24 % and 80.56% respectively. The 24 hour batch test provided evidence of the reversible metabolism of the E2 hormone. This was seen by the rapid decrease of E2 and the rapid increase of E1 in less than 3 hours, which proved that E2 can be metabolized in to E1. An average reduction of 94.44% of E2 was seen after 5 hours and after 10 hours was no longer detected. After 13 hours E1 could no longer be detected. This finding also provided clarity as to the lower percentage removal of E1 during the 10 day SRT of the MLE process. The Vibrio fischeri biotox method implemented was the most economic and easiest way to conduct the toxicity tests. The validation of the test used a 52.9 mg/L K2Cr2O7 standard which provided a Cr (VI) concentration of 18.7 mg/L in the final test suspension which is the theoretical effective concentration causing 50% inhibition (EC50). This specific concentration of the Cr (VI) exhibited an EC50 at 20.08 mg/L. The toxicity investigations of the individual and mixed hormone standards revealed that at the 10 ng/L concentration the individual E2 standard had the highest percentage inhibition (%INH) of 45.99% after the 30 minute contact time (T30), and when this standard was further diluted to 5 and 1 ng/L also showed higher % INH (26.04 and 23.66 %INH, respectively) than the individual EE2 standard (21.92 %INH) at 10 ng/L. . According to the toxicity classification system and after interpretation of the data, all the hormone standards were classified as Class II as they all exhibited slight acute toxicity. The 10 ng/L E2 standard had Toxicity Units (TU) of 0.8 which was close to the Class III level; however when it was in a mixture with E1 and E3, the TU was much lower (0.6 TU). The synthetic EE2 hormone also showed slight acute toxicity and had the lowest TU of 0.4. The application of the above mentioned techniques to full scale WWTPs with different configurations showed different removal efficiencies. The WWTPs ranged from the most primary consisting of just oxidation ponds to biological trickling filters, to biological nutrient removal (BNR) to conventional activated sludge (AS) plants. Removal rates ranged from 29% to 96% for E2, 0% to 89% for E1 and 0% to 100% for EE2. The overall ranking of the WWTPs from the most efficient to least efficient in terms of hormone removal were as follows: Plant E (91%) = Plant D (before UF) (91%) > Plant B (east side) (88%) > Plant B (west side) (77%) > Plant C (east side) (71%) > Plant D (after UF) (57%) > Plant A (56%) > Plant C (west side) (12%). Using the Vibrio fischeri method to evaluate the reduction of toxicity in WWTPs C, D and E proved effective. It was seen immediately after secondary biological treatment in the clarifier effluent the toxicity was reduced. Plants C, D and E had reduced the toxicities by 100, 80 and 97 % immediately after secondary biological treatment, while after the addition of the Chlorine disinfectant in the final stage of treatment the toxicity increased having %INH of 99.9, 15.7 and 99.9 respectively. In conclusion the SPE can be used as an extraction procedure for hormones in wastewater and the immunoassays can be used as rapid techniques for quantification of hormone EDCs in wastewater. The ELISA technique proved to be the slightly superior to the RIA in terms of facilities required. The laboratory scale procedures proved that some hormones can be oxidised to other hormones and therefore longer sludge retention times may be required to improve the removal. The study of the different WWTPs configuration showed that plant configuration and operational parameters impact the removal of hormone EDCs. The composition of the influent received by the plant also has an effect on the removal, i.e., whether it’s industrial, domestic or a mixture of both. Results concluded that plants which have either mixing and/or aeration with activated sludge and longer SRTs of more than 10 days have a higher rate of hormone removal than those plants with shorter SRTs and that the activated sludge processes were capable of reducing the toxicity of the influent. Overall results indicated that hormone EDCs are indeed being discharged with the effluents from WWTPs in South Africa. However whether the concentrations left in the final effluents will still have an adverse effect on the aquatic life is a question that still remains unanswered. The aquatic ecosystems are inevitably being polluted with these EDCs and their breakdown products.Item Functional characterisation of heterotrophic denitrifying bacteria in wastewater treatment systems(2005) Ramdhani, Nishani; Bux, FaizalAtmospheric nitrogen pollution is on the increase and human activities are directly or indirectly responsible for the generation of the various nitrogen polluting compounds. This can lead to the two major problems of eutrophication and groundwater pollution. Therefore, the removal of nutrients such as nitrogen and phosphorus from wastewater is important. Nitrogen removal from wastewater is achieved by a combination of nitrification and denitrification. Thus, there is a need to identify and characterise heterotrophic denitrifying bacteria involved in denitrification in wastewater treatment systems. The aim of this study, therefore, was to characterise heterotrophic denitrifying bacteria through detailed biochemical and molecular analysis, to facilitate the understanding of their functional role in wastewater treatment systems. Drysdale (2001) isolated heterotrophic denitrifiers to obtain a culture collection of 179 isolates. This culture collection was used to screen for nitrate and nitrite reduction using the colorimetric biochemical nitrate reduction test. The isolates were thereafter Gram stained to assess their gram reaction, cellular and colonial morphology. Based on these results identical isolates were discarded and a culture collection of approximately 129 isolates remained. The genetic diversity of the culture collection was investigated by the analysis of polymerase chain reaction (PCR)-amplified 16S ribosomal DNA (rDNA) fragments on polyacrylamide gels using denaturing gradient gel electrophoresis (DGGE). Thus DNA fragments of the same length but different nucleotide sequences were effectively separated and microbial community profiles of eight predominant isolates were created. Batch experiments were conducted on these eight isolates, the results of which ultimately confirmed their characterisation and placed them into their four functional groups i.e. 3 isolates were incomplete denitrifiers, 2 isolates were true denitrifiers, 2 isolates were sequential denitrifiers and 1 isolate was an exclusive nitrite reducer.