Endoglucanases play an important function in cellulose hydrolysis and catalyse the initial attack on the polymer by randomly hydrolysing the β-1,4 glucosidic bonds within the amorphous regions of cellulose chains. Cellulolytic bacteria have been isolated and characterised from the sewage sludge and the activation of several hydrolytic enzymes under biosulphidogenic conditions of sewage hydrolysis has been reported. The aims of this study were to: identify, induce production, locate and isolate, characterise (physicochemical and kinetic) and purify endoglucanases from anaerobic biosulphidogenic sludge. The endoglucanase activities were shown to be associated with the pellet particulate matter and exhibited a pH optimum of 6 and temperature optimum of 50 °C. The enzymes were thermally more stable when immobilised to the floc matrix of the sludge than when they were released into the aqueous solution via sonication. For both immobilised and released enzymes, sulphate was slightly inhibitory; activity was reduced to 84 % and 77.5 % of the initial activity at sulphate concentrations between 200 and 1000 mg/l, respectively. Sulphite was stimulatory to the immobilised enzymes between 200 and 1000 mg/l. Sulphide stimulated the activities of the immobilised endoglucanases, but inhibited activities of the soluble enzymes above 200 mg/l. The enzyme fraction did not hydrolyse avicel (a crystalline substrate), indicating the absence of any exocellulase activity. For CMC (carboxymethylcellulose) and HEC (hydroxylethylcellulose) the enzyme had K_m,app_ values of 4 and 5.1 mg/ml respectively and V_max,app_ values of 0.297 and 0.185 μmol/min/ml respectively. Divalent ions (Cu²⁺, Ni²⁺ and Zn²⁺) proved to be inhibitory while Fe²⁺, Mg²⁺ and Ca²⁺ stimulated the enzyme at concentrations between 200 and 1000 mg/l. All the volatile fatty acids studied (acetic acid, butyric acid, propionic acid and valeric acid) inhibited the enzymes, with acetic acid eliciting the highest degree of inhibition. Sonication released ~74.9 % of the total enzyme activities into solution and this was partially purified by PEG 20 000 concentration followed by DEAE-Cellulose ion exchange chromatography, which resulted in an appreciable purity as measured by the purification factor, 25.4 fold.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Microbiology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

Diversity of micro-organism communities in activated sludge have been analyzed by culture -dependent methods, which exclude the majority of endogenous microbes due to the selective nature of the media. Molecular and biochemical techniques have been evaluated, but they are time - consuming, complex and the results are difficult to interpret. Methods such as community level carbon source utilization patterns (i.e. Biolog) are easy to use and detect different patterns, which could be related to diversity and function, in this and other studies. Our aim was not to try and detect each and every metabolic reaction of all the individuals in the community, but the collective pattern for a specific community. Since, 1) a high species diversity should lead to a higher relative number of substrates utilized, because there are more possibilities and 2) upon dilution, some organisms will be lost (causing a decrease in species diversity) from the community, depending on their abundance and the relative contribution (perhaps only one metabolic reaction in the system), reducing the number of possibilities. The extent of the reduction of the possibilities upon dilution, should theoretically reflect something about the community structure. The key, therefore, lies in the interpretation of the results. The Biolog system unlike traditional culture - dependent methods, which are generally selective for the component of the community that has to be cultured, can reflect the activities of a broad range of bacteria. In this study the Biolog system was not considered as a culture - dependent method, but rather as a collection of metabolic tests (database) used for the purpose of generating a recognizable pattern for a specific community. Our hypothesis was that microbial community level carbon source utilization could be used to determine diversity and evenness in activated sludge systems. In our study we used activated sludge systems representative of an environment with a high species diversity and uneven distribution of species, indicated that upon dilution some of the substrates where no longer utilized due to the loss of some of the species. / Dissertation (MSc Agric (Microbiology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

Dissertation submitted in compliance with the requirements for the Master's Degree in Technology: Biotechnology, Durban Institute of Technology, 2004. / M

M.Sc. (Chemistry) / In this study the stability as well as the fate and behavior of ZnO engineered nanoparticles (ENPs) in municipal wastewater systems were investigated. The first part of the study examined the influence of pH and ionic strength on the stability of ZnO ENPs in domestic wastewater to elucidate the dynamic changes on the ENPs physicochemical characteristics (e.g. aggregation or dissolution). The ZnO ENPs obtained commercially were characterized using transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), dynamic light scattering (DLS), BET surface area determination, and energy dispersive X-ray spectrometry (EDS). Results derived from inductively coupled plasma optical emission spectrometry (ICP-OES) for zinc analysis indicated a decrease on the released zinc concentration from wastewater as the pH and ionic strength increased. Conversely, an increase on zinc concentration from the sludge was observed. The findings suggest the removal of ZnO ENPs from the influent wastewater as the sludge settled out, and the removal efficiency was directly proportional to ionic strength and pH. In addition, the ZnO ENPs suspension in the wastewater was used to monitor the particle size distribution using the dynamic light scattering analysis (DLS). The formation of agglomerates was observed which the TEM and EDS analysis confirmed to be ZnO aggregates. The distribution of zinc in the sludge was investigated using XRD analysis and the findings indicated partial sedimentation of ZnO ENPs as the sludge settled out. The second part of the study assessed the fate and behavior of ZnO ENPs in wastewater treatment systems. This study was carried out in a simulated activated sludge wastewater treatment plant (AS WWTP), constructed in accordance to the Organization for Economic Co-operation and Development (OECD 303 A) guidelines. Results from the ICP-OES analysis for zinc indicated 50 – 200 μgL-1 and about 3 000 mgkg-1 were released into the effluent and sludge, respectively, after spiking the influent wastewater with 5 mgL-1 ZnO ENPs. Moreover, we noted that increasing the ZnO ENPs concentration up to 20 mgL-1 resulted in a linear increase in the zinc releases into effluent wastewater. However, the increase was insignificant in comparison to the zinc found in the control unit. Therefore, the findings indicated that ZnO ENPs had stronger affinity for the suspended bio-solids during wastewater treatment, and postulated that the ENPs removal from the influent wastewater was due to bio-sorption, and bio-solid settling mechanisms. These were confirmed by results from XRD and diffuse reflectance spectroscopy (DRS) analysis of the sludge as they showed the presence of ZnO in the sludge. The dissolved organic carbon (DOC) and chemical oxygen demand (COD) were concurrently monitored during the ENPs exposure studies to indirectly assess the ZnO ENPs impact to the bacterial degradation of the organic matter. An average of 43 and 91 % for DOC and COD removal efficiencies, respectively, were observed throughout the study. Overall, from results obtained indicated the suitability of the OECD 303 A method to assess the fate and behavior of ZnO ENPs in WWTPs. Secondly, in light of low concentrations of ZnO ENPs found in the treated effluent due to their removal with the waste activated sludge (WAS), suggest low likelihood of ZnO ENPs release and dispersion into the aquatic systems from WWTPs as point sources. Finally, the elevated concentrations of ZnO ENPs in the sludge therefore necessitates additional treatment steps to ensure mitigation of possible dispersion of ENPs from various disposal mechanisms such as landfilling, incineration, and agricultural applications.

An investigation into the removal of phosphorus in the activated sludge process showed that: (1) Luxury uptake of phosphorus may be induced by the presence of an anoxic zone (2) If a primary and secondary anoxic reactor are present in the system, the actual retention time of the primary anoxic reactor will have the dominant effect on the degree of phosphorus removal. (3) In a system where only a primary anoxic reactor is present, there is an optimum actual anoxic retention time for obtaining maximum phosphorus removal. This optimum value appears to coincide with the condition where there is no nett release of phosphorus in the anoxic zone. Decreasing or increasing the actual anoxic retention time either side of the optimum value has a detrimental effect on phosphorus removal. (4) Increasing the influent ammonia-nitrogen and hence the reactor nitrate concentration, enhances phosphorus removal. (5) An increase in aeration reactor pH to between pH 7-8 enhances phosphorus removal. (6) The mechanism of removal does not appear to be precipitation. Although an increase in pH through the anoxic reactor was observed due to denitrification, phosphorus was released into solution. (7) The degree of phosphorus removal is independent of the influent phosphorus concentration. (8) Anoxic stripping of phosphorus is not a pre-requisite for luxury uptake of phosphorus to occur. (9) The concentration of phosphorus removed is a function of the COD utilized. The ratio of phosphorus removed to the COD utilized is constant at a particular sludge age, so that as the concentration of COD utilized increases, the concentration of phosphorus removed increases. (10) The concentration of phosphorus removed is a function of the sludge age. For a fixed biodegradable influent COD, the longer the sludge age, the less phosphorus removed.

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No description available.

Despite the technology advancement, degradation of water quality due to stormwater continues to be a significant threat to the water and ecosystems due to the exponential growth of industries and agricultural enterprises that discharge stormwater. These anthropogenic activities are the sources of high nitrogen and phosphorus quantities in stormwater, which is responsible for eutrophication phenomena and deterioration of public health. Floating Treatment Wetlands (FTWs) are a potential solution to this problem. Both microcosm and mesocosm level studies were conducted for the effective removal of nutrients in stormwater wet detention ponds with different sorption media under varying nutrient concentrations and weather conditions. Water depth, percent area coverage of the FTWs and littoral zone emergent plants were varied in order to determine nutrient removal efficiency before implementing in an actual pond. Focus has also been placed on the observations of macrophyte-epiphyte-phytoplankton interactions in order to understand temporal characteristics of ecological phenomena. Water quality parameters included Total Nitrogen, Total Phosphorus, Orthophosphate, Nitrate-Nitrogen, and Ammonia-Nitrogen in addition to in-situ parameters such as pH, Dissolved Oxygen, Temperature and Chlorophyll-a. Results clearly indicate that an FTW filled with sorption media of 80% expanded clay and 20% tire crumb can significantly promote the biomass growth. Different levels of nutrient concentrations did affect the plants’ growth and cold temperature in late winter was detrimental to growth. To make the system more viable irrespective of the seasonal weather conditions, the adoption of mixed vegetation is highly recommended in the FTWs implementation. It is also recommended that, the positioning of the floating wetlands should not be in the vicinity of the outlet of the pond as assimilated nutrient under the mat might increase the nutrient concentration in the discharged water. Finally, One-way ANOVA test is performed to check whether or not iv these grouped microcosms and mesocosms with differing experimental setup can be deemed statistically significant

M.S.