Projects
Bioremediation of hexavalent contaminated groundwater (New Project)
Groundwater in the Durban South basin is contaminated with hexavalent chromium with the plume of approximately 3 km. The current remedial approach is focusing on ‘pump and treat’ technology. However, the project also invloves isolating indigenous bacteria from the contaminated soil with the intention of bioremediation of the contaminated soil. Focus will also be on bioaugmentation/biosupplementation to stimulate the indigenous microbial population to facilitate reduction to tri-valent form.
Microbial community analysis of a full-scale membrane bioreactor (MBR) (New Project)
Currently there is an increased focus on water reuse projects and for more feasible advanced wastewater treatment technologies. In the near future, disposal of effluent into the sea will not be permitted. Companies already within this practice are currently given the opportunity to seek alternative methods for their disposal. The MBR process is an emerging advanced wastewater treatment technology that has been successfully applied at an ever increasing number of locations around the world primarily due to the system meeting an increasing demand for a low maintenance treatment system capable of treating a wide range of effluents and subsequently allowing for on-site water reclamation with the effluent quality passing stringent discharge standards. South Africa in particular has a need to develop new strategies for water management and reuse. In addition to the above, one of the key benefits of a membrane bioreactor system is that it effectively overcomes the limitations associated with poor settling of sludge in conventional activated sludge (CAS) processes. An industrious producer of sugar and prominent manufacturer of downstream products in South Africa, introduced a Kubota™ Submerged Membrane Bio-Reactor to address their wastewater treatment problems. Sugar manufacturing requires large volumes of water for raw material cleaning, sugar extraction, furfural extraction, cooling and cleaning equipment. Thus the recycling of process wastewater is essential and the application of an SMBR proved feasible. for optimization and greater efficiency of the plant, fundamental and comprehensive knowledge of the microbial communities present is imperative. Thus far, such knowledge is limited. The elucidation of the bacterial community and their associated roles within the SMBR will allow for increased optimization of the plant. Fluorescent in situ hybridization is a unique molecular method that may be used for the identification of microorganisms within the SMBR. The problem the company faces with identification of the microorganisms in SMBR, is the inadequacy of microbiological equipment and expertise. FISH allows for the quick, simple and accurate detection of bacterial species without the need to culture. The application of the FISH technique is useful to determine the abundance of respective populations in microbial community samples.
Microbial carotenoid production from cooling tower brine effluent (Ongoing project):
Two carotenoids, Beta-carotene, which are highly pigmented (red, orange, yellow), fat-soluble compounds naturally present in many fruits, grains, oil and vegetables, and Astaxanthin (red), which belongs to a larger class of phytochemicals known as terpenes, will be produced from two algae, Dunaliella salina and Haematococcus pluvalis respectively using cooling tower brine effluent as a substrate. Dunaliella salina is a halophilic micro-alga found especially in sea salt fields. It is the only eukaryotic alga which can accumulate maximum amounts of beta-carotene in its inter-thylokoid space of chloroplast when subjected to optimum conditions. It is commonly used in cosmetic and dietary supplement, for its antioxidant activity. Beta-carotene will be extracted from Dunaliella salina, which will be maintained on Zarrouks medium. A flat plate bioreactor containing brine effluent will be used to grow the alga. Brine effluent will be supplemented with various components using statistical design of experiments to optimise the supplements. Five ml samples will be removed every 24 hours and centrifuged at 5000xg for 20 minutes. The remaining pellet of cells will be dried under a vacuum at 50oC. A two ml aliquot of solvents, absolute ethanol and 99.5% acetone will be used to extract beta-carotene from the cells respectively. Following incubation of the cells with the solvents on a rotary shaker at 130 rpm for two hours, the amount of beta-carotene extracted will be read at 450 nm using a diode array WPA Lightwave S2000 spectrophotometer. Astaxanthin is a very potent antioxidant with applications in Cosmetic, Nutraceutical, Food and Feed Industries. It is responsible for the colouration of crustaceans and salmonoids. Astaxanthin enhances the immune system, prevents oxidative stress and can cross the blood-brain and retina barriers. While astaxanthin is a natural nutritional component, it can be found as a food supplement. The supplement is intended for human, animal, and aquaculture consumption. Haematococcus pluvalis can produce over 40 g/L of astaxanthin under optimal conditions and it is one of the most promising microorganisms for the production of astaxanthin commercially. This study will attempt to produce astaxanthin by growing H. pluvalis in cooling tower brine effluent and supplementing with various components in order to maximise astaxanthin production. Production will be scaled up using flat plate and tube bioreactors to determine the best reactor configuration for astaxanthin production. Statistical design of experiments will be used to choose and optimise the amounts of supplements required. To measure the astaxanthin concentration, a 10 ml broth culture is centrifuged (5,000x g, 10 min) and is maintained at -800C for two hours. Two mL of 2.5 M HCl is added and the cells are heated in a water bath for 2.5 minutes. After cooling, the cells are centrifuged (5,000x g, 10 min) and washed with deionized water. Six mL of acetone is added and the samples are kept at 400C for 1.5 hours. Excess water is removed by the addition of Na2SO4 powder and the cells are maintained at 40C for 30 minutes. After centrifugation (5,000x g, 10 min), the absorbance will be measured at 478 nm using a WPA Lightwave S2000 spectrophotometer.
Monitoring Of Specific Endocrine Disrupting Chemicals In The Environment Due To Industrial Discharges (Ongoing Project):
The study focused on isolating microorganisms from industrial wastewater capable of aerobic degradation of PCBs. The degradation potential of the selected isolates were investigated by using different analytical techniques viz. ultra violet or visible spectrophotometer (UV/Vis), thin layer chromatography (TLC) and gas chromatography electron capture detector (GC-ECD). There were two unknown organisms selected for further investigations. The isolates were presumptively identified by a 20E API kit as Acinetobacter sp. and Pseudomonas sp. The degradation potential was analysed by comparative GC analysis of selected PCB congeners. Comparison of Aroclor 1254 and Aroclor 1260 found that in the mixed culture the Pseudomonas sp. was influential in the degradation process than the Acinetobacter sp. It was concluded that the mixed culture of Acinetobacter sp. and Pseudomonas sp. proved efficient to transform both Aroclor 1254 and Aroclor 1260. While the pure isolate; Pseudomonas sp. showed the most efficient transformation of Aroclor 1254 and Aroclor 1260. Further studies will involve the molecular identification of the Acinetobacter sp. and Pseudomonas sp. The potential degradation of these organisms will be investigated in a soil environment.
Characterization Of Filamentous Bacteria From Activated Sludge Treating Industrial Wastewater (On-going Project)
This research aims at profiling predominant filamentous bacteria from an activated sludge process treating industrial wastewater in Durban (Kwa-Zulu Natal). Most research has been focused on filaments occurring in domestic wastewater and not much work has been done on filaments occurring in industrial wastewater. Isolation has been greatly dependent on conventional isolation methods whereas micromanipulation provides an added advantage by directly isolating specific filaments from the sludge. Samples will be collected from Harmmarsdale, Southern wastewater works and Darvill wastewater works. This research will be carried out in a period of two years and is planned to achieve the following objectives:
- To isolate predominant filamentous bacteria from industrial wastewater using micromanipulation
- To select appropriate media for growth of isolates & optimize conditions for maintenance of culture
- To study the phylogenetic relationship amongst isolates using 16S rDNA region
- To identify isolates using FISH (fluorescent in situ hybridization) and DNA sequencing
- To ensure purity and characterization of using Eikelboom identification methods
- To determine physiological, biochemical and morphological characteristics of isolates
Analysis of problematic filamentous bacteria in activated sludge wastewater treatment plants (On-going project):
Bulking and foaming have drawn considerable interest, as they are the major problems affecting activated sludge process efficiency. Both are direct consequences of poor solid separation caused by filamentous bacteria. The identification and characterisation of filamentous bacteria and their association with specific operating conditions and influent characteristics were the first steps taken towards establishing methods of control. The amelioration of filamentous bacterial related activated sludge problems would significantly facilitate enhanced plant operation and possibly permit the treatment of higher influent loadings. The project aims at investigating the filamentous bacterial population dynamics in conjunction with the plant operating conditions and the respective influent characteristics. This type of work has been documented in Europe, Australia and some parts of the United States. However, the results of these studies are not applicable to South Africa because South Africa experiences different climatic conditions, has different treatment processes/plant configurations with different influent types and loadings. Novel molecular techniques will be used to identify the filamentous bacteria. The techniques that will the applied are Fluorescent in Situ Hybridisation (FISH), DNA sequencing, Polymerase Chain Reaction (PCR) and gel electrophoresis. Real-time PCR will also be used to quantify the bacteria to draw a possible correlation between filamentous bacterial numbers and process performance.