Nutrient removal and biofuel potential of MaB-floc biomass from an integrated algal pond system treating domestic sewage
- Authors: Sibelo, Linda
- Date: 2020
- Subjects: Biomass energy , Waste products as fuel , Algal biofuels , Sewage -- Purification -- Nutrient removal
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/144955 , vital:38395
- Description: Integrated algal pond systems (IAPS) are a passive water treatment technology derived from the Oswald designed advanced integrated wastewater pond systems (AIWPS®) and effect wastewater treatment based on biological activity of microorganisms within the system, solar energy and gravity. The technology consists of an advanced facultative pond (AFP), a series of interconnected high rate algal oxidation ponds (HRAOP) and algal settling ponds. The symbiotic relationship between microalgae and bacteria facilitated by paddlewheel mixing of HRAOP results in the formation of biomass aggregates known as MaB-flocs. MaB-floc formation enhances nutrient abstraction, gravitational sedimentation and separation from water hence forming two product streams; recyclable water and biomass, both with valorisation potential. This work aimed to determine the suitability of MaB-floc biomass generated in the HRAOP of an IAPS treating domestic sewage as feedstock for biofuel production based on the content of carbohydrate and lipid. Nutrient removal efficiency, biomass productivity and bulk lipid and carbohydrate concentration were monitored for two consecutive three-month periods in the winter and summer seasons of 2018/19. Maximum removal efficiencies of nitrogen and phosphorus were determined as 71% and 75% respectively, demonstrating the efficiency of IAPS as a wastewater treatment technology. MaB-floc biomass productivity in winter and summer was 9.4 g/m2/d and 16.5 g/m2/d respectively indicating the heavy influence of seasonal temperature, possibly day length, and solar irradiation on biomass productivity in the HRAOP. Summer productivity was lower than the maximum theoretical productivity of 25 g/m2/d possibly due to photoinhibition of photosynthesis as well as grazing pressures caused by the proliferation of rotifers mainly of the Brachionus genus. MaB-floc biomass consistently contained higher amounts of carbohydrate than lipid despite the changes in species dominance from Scenedesmus sp. and Desmodesmus sp. in winter to Pediastrum sp. in summer. Variations in MaB-floc biomass carbohydrate content were linked to changes in nitrogen concentration, mainly in the form of nitrates. Lower nitrogen concentration significantly increased the carbohydrate content of MaB-floc biomass from 17.5 ± 0.15% to 33.5 ± 0.3 % recorded in summer. In winter, biomass carbohydrate increased from 18.3 ± 1.2% to 35.8 ± 0.3%.To induce accumulation of carbohydrates through nitrogen starvation, isolated microalgal species native to the HRAOPs of the IAPS at Institute for Environmental Biotechnology Rhodes University(EBRU) were used. The outcome from the laboratory studies showed that carbon partitioning within isolated strains could be altered from carbohydrate to lipid which is more energy-rich. Hence, exploring the biodiesel production option using HRAOP MaB-floc biomass, which had a lipid content ranging between 12.1 ± 0.64 % and 13.9 ± 0.5 %, would require a preconditioning step in the form of nitrogen starvation to enhance its lipid content. Overall, the outcome of outdoor monitoring studies on biomass biochemical composition indicated that HRAOPs operating under natural environmental conditions preferentially generated a biomass rich in carbohydrate. Therefore, anaerobic digestion may be a more viable option for HRAOP MaB-floc biomass because of the high carbohydrate levels ranging between 24.9 ± 0.6 % and 25.6 ± 1.3 % of the dry MaB-floc biomass weight. Despite the low biomass C/N ratio (7.1 to 7.8), the MaB-floc biomass can be anaerobically co-digested with a higher C/N ratio (24) substrate such as in-pond digester sludge, to improve methane yields calculated to be between 0.31 m3 CH4/ kg MaB-floc biomass and 0.33 m3 CH4/ kg MaB-floc biomass. Anaerobic digestion of biomass also produces CO2 which can be recovered and added to HRAOPs to enhance MaB-floc biomass productivity while lowering greenhouse gas emissions from a wastewater treatment plant. The digestate from the anaerobic process, which is rich in nitrogen and phosphorus can be used as a biofertiliser. Thus, a potential MaB-floc biomass biorefinery consisting of biogas and bio-fertiliser pathways can be established using IAPS treating sewage as the platform technology. IAPS is a system designed to operate in a way that is passive and without substantial environmental impact but technological innovations and a reduction in the size of the system are required to make the technology more acceptable.
- Full Text:
- Date Issued: 2020
Evaluation of Fungcoal as a bioprocess technology for self-cladding of waste coal dumps
- Authors: Sekhohola, Lerato M
- Date: 2016
- Subjects: Coal mine waste , Fungi -- Biotechnology , Coal -- Biodegradation , Bermuda grass -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5959 , http://hdl.handle.net/10962/d1019992
- Description: Low-grade coal, a poor source of energy, has long been regarded as waste material by the coal mining industry. Biological degradation of this coal material by ligninolytic fungal strains presents a viable strategy towards eliminating this unusable fossil fuel. To this end, a novel and patented bioprocess termed Fungcoal was developed. Fungcoal is a biological process utilised in the in situ treatment of waste coal and is based on the mutualistic relationship between the fungus Neosartorya fischeri and the graminaceous species Cynodon dactylon. The process facilitates the rapid conversion of waste coal into soil-like material that stimulates establishment of vegetation for eventual coal dump rehabilitation. While a number of in vitro studies have identified various fungal strains as efficient coal degraders, the mechanisms involved in the Fungcoal-stimulated degradation process have not been fully elucidated. Furthermore, implementation of Fungcoal at both pilot and commercial scale has not been achieved. Thus the objective of this work was to investigate Fungcoal as a bioprocess via examining the role of coal degrading fungi (CDF) and grasses as biocatalysts in coal biodegradation and for the self-cladding of waste coal dumps. Initially, waste coal degradation by N. fischeri, strain ECCN 84, was investigated, specifically focusing on the mechanisms underpinning the process. In vitro studies showed the addition of waste coal induced active fungal colonisation resulting in increased fungal biomass. Increased extracellular laccase (LAC) activity, occuring concomitantly with an increase in hyphal peroxisome proliferation, was also observed in the coal supplied fungal cultures. Analysis of the colonised waste coal revealed a time dependent reduction in the percentage weight of elemental carbon coupled with an increase in elemental oxygen. The results supported metabolism and degradation of waste coal by N. fischeri strain ECCN 84 and involvement of fungal extracellular laccase. The contribution of C. dactylon, a C4 grass species to in situ biodegradation of waste coal in the presence of coal degrading and mycorrhizal fungi (MF) was also investigated. Enhanced degradation of the waste coal into a humic soil-like material was observed within the rhizosphere. Analysis of the resultant substrate revealed an increased concentration of highly oxidised humic-like substances (HS). Fungi remained viable in the rhizosphere up to 47 weeks post-inoculation and cultivation of C. dactylon, indicating the resultant humic substance-rich rhizosphere provided an environment conducive for microbial proliferation and activity. Furthermore, humic substance enrichment of waste coal substrates supported germination and seedling emergence of several agronomic species including Zea mays (corn), Phaseolus vulgaris (bean), Pisum sativum (pea), and Spinacia oleracea (spinach). Use of various cladding materials to support coal biodegradation, by fungus-grass mutualism and rehabilitation of waste dumps was evaluated at commercial scale. While substantial physico-chemical changes were not evident in the absence of cladding or where waste coal was used as cladding material, successful establishment of grass cover and diversity was achieved within three hydrological cycles on dumps cladded with weathered coal. Work presented in this thesis successfully demonstrates the degradation of waste coal by N. fischeri. The biodegradation process included enhanced extracellular LAC activity coupled with increased 3 waste coal oxidation. Increased HS concentration of waste coal substrate supported germination and early seedling establishment of several agronomic species. At commercial scale a co-substrate in the form of carbon-rich weathered coal was essential to support fungus-grass mutualism and Fungcoal-induced rehabilitation. These findings support the developed Fungcoal concept and the underpinning rationale that the phyto-biodegradation of waste coal indeed depends on the mutualistic interactions between grass root exudates and the ligninolytic and mycorrhizal fungi. Taken together, these findings provide practical evidence of the contribution of fungi and grasses as mutualists in the biodegradation of waste coal and sustainable rehabilitation of waste coal dumps
- Full Text:
- Date Issued: 2016
Integrated Algae Pond Systems for the Treatment of Municipal Wastewater
- Authors: Mambo, Mutsa Prudence
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5960 , http://hdl.handle.net/10962/d1021258
- Description: Integrated algae pond systems are a derivation of the Oswald designed advanced integrated wastewater ponding system, and combine the use of anaerobic and aerobic bioprocesses to effect wastewater treatment. Integrated algae pond system technology was introduced to South Africa in 1996 and a pilot plant was designed and commissioned at the Belmont Valley wastewater treatment works in Grahamstown. Previous studies showed that this system delivered a final effluent superior to most pond systems deployed in South Africa but that it was unable to meet the general standard for nutrient removal and effluent discharge. This study was initiated to re-appraise integrated algae pond systems and to assess the potential of the technology as an effective municipal sewage treatment system. And more...
- Full Text:
- Date Issued: 2016
Bacterial degradation of fossil fuel waste in aqueous and solid media
- Authors: Edeki, Oghenekume Gerald
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54565 , vital:26588
- Description: The generation of environmental pollutants worldwide is mainly due to over reliance on fossil fuels as a source of energy. As a result of the negative impacts of these pollutants on the health of humans, animals, plants and microorganisms, global attention has been directed towards ways of containing this problem. Biodegradation of fossil fuel is one of the most effective methods used to remediate contaminated systems. However with regard to coal waste, much of what is known is based on the ability of fungal species to biosolubilize this material under enrichment conditions in a laboratory setting. For effective biodegradation as a remediation technique, there is an immediate need to source, isolate, enrich and incorporate other microorganisms such as bacteria into bioremediation technologies. The goal of this dissertation was to isolate bacteria from fossil fuel contaminated environments and to demonstrate competence for petroleum hydrocarbon degradation which was achieved using a combination of analytical methods such as spectrophotometry, FT-IR, SEM and GC-MS. Screening for biodegradation of coal and petroleum hydrocarbon waste resulted in the isolation of 75 bacterial strains of which 15 showed good potential for use in developing remedial biotechnologies. Spectrophotometric analysis of bacteria both in coal and petroleum hydrocarbons (all in aqueous media) revealed a high proliferation of bacteria in these media suggesting that these microbes can effectively utilize the various substrates as a source of carbon. The isolated bacteria effectively degraded and converted waste coal to humic and fulvic acids; products required to enrich coal mine dumps to support re-vegetation. Scanning electron microscopy showed the attachment of bacteria to waste coal surfaces and the disintegration of coal structures while FT-IR analysis of extracted humic-like substances from biodegraded waste coal revealed these to have the same functional groups as commercial humic acid. Specific consortia which were established using the isolated bacterial strains, showed greater potential to biodegrade coal than did individual isolates. This was evident in experiments carried out on coal and hydrocarbons where the efficient colonization and utilization of these substrates by each bacterial consortium was observed due to the effect of added nutrients such as algae. The biodegradation of liquid petroleum hydrocarbons (diesel and BTEX) was also achieved using the 15 bacterial isolates. GC-MS analysis of extracted residual PHC from aqueous and solid media revealed rapid breakdown of these contaminants by bacteria. Different bacterial consortia established from the individual isolates were shown to be more efficient than single isolates indicating that formulated consortia are the biocatalysts of choice for fossil fuel biodegradation. This study represents one of the most detailed screenings for bacteria from fossil fuel contaminated sites and the isolation of strains with potential to biodegrade coal and petroleum hydrocarbon wastes. Several consortia have been developed and these show potential for further development as biocatalysts for use in bioremediation technology development. An evaluation of efficiency of each established bacterial consortium for biodegradation in a commercial and/or industrial setting at pilot scale is now needed.
- Full Text:
- Date Issued: 2015
Bacterial degradation of waste coal
- Authors: Madikiza, Lwazikazi
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54576 , vital:26590
- Description: As an energy source coal has one of the largest agglomerations in the world. Consequently mining of coal creates large volumes of waste in the form of low ranks coals. The complex structure of coal makes it difficult for the microorganisms to degrade and relatively few bacteria and fungi have been shown to break down coal. This study aimed to investigate bacteria not previously known to degrade coal. In this study bacteria were isolated from hydrocarbon contaminated sites and inoculated in coal medium where coal served as the only carbon source. Three strains produced a yellow – brown supernatant after 14 d of incubation at 30 °C. Bacteria generating a yellow – brown coloured supernatant were presumed to possess coal degrading capabilities and the best performing of these bacterial species was identified using 16s rDNA as Bacillus flexus. Scanning electron microscopy showed that there was a close association between the bacterium and substrate coal. The close association of bacteria to substrate suggested that these organisms were able to maximize solubilisation. FT-IR spectroscopic analysis demonstrated the addition of single bonded compounds COOH, OH, CN and CH that were absent prior to bacterial interaction. The increase in oxygen rich regions indicated degradation of the coal substrate. Elemental analysis showed that there was a decrease in carbon content from 47 % to 24 % during the 14 day incubation period. Reduction in coal carbon content was assumed to be due to bacterial utilization for metabolism and growth particularly as untreated coal substrate showed minimal loss of carbon. Analysis of the residual culture medium revealed that there was a linear increase in humic-like substance concentration for 8 d, coincident with increased coal biosolubilisation and colour change. Laccase activity was insignificant, and at 13 d enzyme activity was only 5×10-3 U/L suggesting that B. flexus may use a different mechanism to degrade coal. Residual culture medium remaining after bacterial action on the coal substrate appeared to possess plant growth promoting activity. This soluble biodegradation product with characteristics similar to humic acid-like substances was shown to impact growth of radish cotyledons. Expansion of isolated radish cotyledons was enhanced by 140% when incubated in coal biodegradation product. In conclusion, this study has yielded B. flexus and two other unidentified bacteria, isolated from polyaromatic hydrocarbon contaminated soils, and demonstrated the ability of these microorganisms to degrade waste coal. Further studies to elucidate the mechanism of coal breakdown by B. flexus, synergies with other coal degrading microorganisms, and incorporation of bacterium into Fungcoal bioprocess technology is imminent.
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- Date Issued: 2014
Exploring the fertiliser potential of biosolids from algae integrated wastewater treatment systems
- Authors: Mlambo, Patricia Zanele
- Date: 2014
- Subjects: Sewage disposal plants , Sewage sludge as fertilizer , Algae -- Biotechnology , Sewage -- Purification -- Anaerobic treatment , Plant regulators , Biofertilizers , Microalgae -- Biotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5957 , http://hdl.handle.net/10962/d1013342
- Description: High rate algae oxidation ponds (HRAOP) for domestic wastewater treatment generate biosolids that are predominantly microalgae. Consequently, HRAOP biosolids are enriched with minerals, amino acids, nutrients and possibly contain plant growth regulator (PGR)-like substances, which makes HRAOP biosolids attractive as fertiliser or PGR. This study investigated HRAOP biosolids as a starting material for a natural, cost-effective and readily-available eco-friendly organic fertiliser and/or PGRs. Various HRAOP extract formulations were prepared and their effect on plant growth and development was evaluated using selected bioassays. Initial screening included assessing the effect on change in specific leaf area, radish cotyledon expansion as an indicator of PGR-like activity, and seed germination index (GI). More detailed studies on fertiliser efficacy and PGR-like activity utilised bean (Phaseolus vulgaris) and tomato (Solanum lycopersicum) plants. Combined effects of sonicated (S) and 40% v/v methanol (M) extract (5:1 SM) had impressive plant responses, comparable to Hoagland solution (HS). Other potentially fertiliser formulations included 0.5% M, 1% M, 2.5% S and 5% S formulations. The 5:1 SM and 5% S showed greater PGR-like activity, promoting cotyledon expansion by 459 ± 0.02% and 362 ± 0.01%, respectively. GI data showed that none of the formulations negatively impacted germination. Further investigation showed that the 5% S formulation increased leaf length, width and area by 6.69 ± 0.24, 6.21 ± 0.2 mm and 41.55 ± 0.2 mm². All formulated fertiliser extracts had no adverse effect on chlorophyll content and plant nutrient balance as indicated by C:N (8-10:1) ratio. In addition, plants appeared to actively mobilise nutrients to regions where needed as evidenced by a shift in shoot: root ratio depending on C, N and water availability. Furthermore, 5% S caused a 75% increase in tomato productivity and had no effect on bean productivity. Whereas, 5:1 SM and 1% M formulation improved bean pod production by 33.3% and 11%, respectively but did not affect tomato production. Harvest index (HI) however indicated a 3% reduction in tomato productivity with 5:1 SM and little or no enhancement in bean productivity with both 5:1 SM and 5% S treatments. Bean plants treated with 5:1 SM and 5% S produced larger fruits, which could be an indication of the presence of a PGR effect. Overall, HRAOP biosolids extracts prepared and investigated in this study demonstrated both fertiliser characteristics and PGR-like activity with performances comparable and in some cases exceeding that of commercial products. However additional research is needed to confirm presence of PGR-like activities and fertiliser efficacy.
- Full Text:
- Date Issued: 2014
Constituent processes contributing to stress induced β-carotene accumulation in Dunaliella salina
- Authors: Phillips, Lesley Gail
- Date: 1995
- Subjects: Dunaliella Carotenes Plants -- Effect of stress on
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5658 , http://hdl.handle.net/10962/d1005341
- Description: The alga Dunaliella salina possesses the unique ability to accumulate up to 14 % of it's dry weight as β-carotene in response to stress conditions. This hyper-accumulation of β-carotene has led to the commercial exploitation of this alga for the biotechnological production of this important carotenoid. In order to maximise β-carotene production, a dual-stage process which separates the distinctive growth phase from the β-carotene accumulating stress phase has recently been patented. Preliminary laboratory studies showed that although stress factors such as high salinity and nutrient limitation enhance β-carotene accumulation in D. salina (± 10 pg.cell⁻¹), high light intensity was the single most important factor contributing to the induction of β-carotene accumulation in this alga (± 20 pg.cell⁻¹). Moreover, it was demonstrated that β-carotene accumulation can be further stimulated by exposing the alga to a combination of high light intensity, salt and nutrient stresses (± 30-60 pg.cell⁻¹). The response of D. salina to stress was shown to occur in two phases. The first phase occurred within 24 hours and was characterized most importantly by higher rates of β-carotene accumulation for all the stresses investigated. In cells exposed to multiple stress factors in mass culture, the β-carotene accumulation rate was as much as 9.5 pg.cell⁻¹.day⁻¹ in the first phase compared to only 3 pg.cell·day⁻¹ in the second phase. Since the rate of β-carotene accumulation was higher within the first 24 hours after exposure to stress, the first phase was considered crucial for stress-induced β-carotene accumulation. Characterization of this phase revealed that the stress response was multifaceted. Transition of cells from the growth stage to stress conditions was characterized by the following: 1) Change in cell volume. Hypersalinity caused cell shrinkage while cells exposed to nutrient limitation and/or high light intensity caused cells to swell. Restoration of cell volume was shown to occur within 8 hours for all stresses investigated. 2) Altered photosynthesis. Inhibition of both carbon fixation and oxygen evolution was demonstrated in cells immediately after exposure to multiple stress factors. 3) Production of abscisic acid. Intracellular ABA levels increased within 6-8 hours after exposure to all stresses investigated. The rise in intracellular ABA levels coincided with an increase or return to starting cell volume. High intracellular ABA levels were however transient and within 24 hours ABA began to partition into the culture medium. 4) Change in pigment composition. Changes in xanthophyll cycle pigment content was demonstrated soon after exposure to stress conditions. In hypersalinity shocked cells, initial epoxidation of zeaxanthin to violaxanthin and subsequent de-epoxidation to zeaxanthin occurred, whereas exposure to high stress resulted in an immediate and continued decrease in the epoxidation state indicating accumulation of zeaxanthin. A rapid rate of chlorophyll depletion was also demonstrated. In addition to the above responses a rapid decrease in growth rate during this phase was also noted. An interrelationship between cell volume change, ABA production, maintenance of xanthophyll cycle operation and β-carotene accumulation therefore appeared to exist. ABA production was shown to be stoichiometrically related to changes in xanthophyll content with r² = 0.84 and slope of the curve = 0.91 being achieved for high light stressed cells. This study therefore presents strong circumstantial evidence in support of a carotenoid origin for ABA in Dunaliella. In addition, enhanced β-carotene content was achieved by the application of exogenous ABA and related compounds suggesting a role for ABA as a regulator of the overall stress response. Furthermore, zeaxanthin accumulation was shown to be positively correlated ( r²≥ 0.81) to β-carotene accumulation for all the stresses investigated. The second phase was characterized by a return to homoeostasis of the physiological processes mentioned above, indicating acclimation of the cell to prevailing conditions. This stage was characterised by continued β-carotene accumulation and a decreased epoxidation state of the xanthophyll cycle which together appeared to sustain photosynthesis, allowing this organism to tolerate stress conditions.
- Full Text:
- Date Issued: 1995