No description available.

Arsenic (As) is a common occurring environmental pollutant. The USEPA has a stricter regulation for arsenic in drinking water (10 ug/L). Small drinking water suppliers from regions with high arsenic backgrounds levels, will need to remove arsenic from drinking water in order to meet the new standard. The proposed treatment by the USEPA is the oxidation of arsenite (AsIII) to arsenate (AsV) followed by the adsorption onto metal oxides (e.g. granular ferrihydrite (GFH)). Large amounts of arsenic-bearing solid waste will be generated and disposed in municipal landfills based on EPA's recommendation. The alkaline and anaerobic conditions prevailing in mature landfills combined with the high content of organic matter and the microbial activity prevailing in landfill could play an important role in the biotransformation and mobilization of sorbed arsenic in landfills. The extensive use of organo arsenical compounds such as pesticides in agriculture has become an emerging source of arsenic contamination in the environment. Roxarsone (4-hydroxy-3-nitrophenylarsonic acid) is a compound supplemented in the poultry feed to enhance growth by controlling coccidian parasites. Chickens excrete the roxarsone without changes in its chemical structure. Land application of chicken manure in agricultural fields is a common practice. Approximately 900 metric tons of roxarsone is estimated to be released into environment in the U.S. annually. The environmental impact is significant when considering that these quantities of arsenic are spread onto relative small land areas in the direct vicinity of poultry houses. The aim of this study is to evaluate the role of anaerobic bioconversion on the fate and mobility of inorganic and organic arsenic compounds. The results taken as a whole suggest that arsenic in drinking water residuals is susceptible to enhanced mobilization due to anaerobic microbial activity, and therefore As mobilization should be expected in mature landfills. Roxarsone was readily biotransformed by a methanogenic consortium to its corresponding amino compound, 4-hydroxy-3-aminophenylarsonic acid (HAPA). A fraction of the HAPA went on to be converted to AsIII after long term incubations. Therefore, land application of roxarsone-containing wastes could potentially lead to the formation of more toxic and mobile forms of arsenic which will have negative impact on the environment.

No description available.

No description available.

No description available.

Human consumption of water contaminated with faecal polIutants is the source of most sanitation related diseases. Excreta related diseases can be controlIed by improvements in excreta disposal. The primary consideration is to remove contact between the people and the faecal matter. The conventional waterborne sewage system is not an achievable minimum standard in dense peri-urban areas in the short term, due to its high cost. A need for a cost effective system that is easily maintained and does not require electricity or highly skilled labour for developing communities in South Africa was identified. The objective of this investigation was to assess the suitability of the Anaerobic Baffled reactor (ABR) as a primary onsite treatment system for low-income communities. The ABR is a high-rate compartmentalised anaerobic bioreactor, the design of which promotes the spatial separation of microorganisms. The trials were conducted on a 3200 L pilot-scale reactor placed at Kingsburgh wastewater treatment works, which receives only domestic wastewater. The ABR proved to be stable and consistent in its performance. Operating at a hydraulic retention time of 22.5 h, the reactor effiuent was ca. 200 mgCODIL. The 0,45flm filtered (soluble) COD was 100 mgIL, indicating there was approximately 100 mgIL of COD in the effluent that was in particulate form. The ABR achieved 60%VSS and 50%TSS removal with effiuent TSS content of about 225 mgIL. The system was hydraulicalIy overloaded and organicalIy under loaded. The Biochemical Methane Potential tests showed that 60% of the COD in the effiuent was biodegradable, and the effluent COD could be reduced to less than 100 mgCODIL if the HRT is increased giving a possible removal of 80%. The analytical campaign revealed that we were sampling at peak flow, when COD was high. The average COD fed to the reactor was much lower than that showed by routine analysis and the ABR had a "true" COD removal of 42%. The reactor was able to handle the daily variation ofthe wastewater. Settling tests were done to measure how much of the suspended solids in the ABR are retained at the operating upflow velocity. The method selected was shown to have an error that ranged from 5 to 42%, and the ABR was retaining between 60 and 90% ofsolids in the reactor at an upflow velocity of O.5m/h. The preliminary work with the fabric membrane showed great potential benefits that can be gained if it had to be included. It showed good ability to remove indicator organism and solids that contributed a lot to the effiuent COD. The membrane had 5 log removal of indicator organism and 80% reduction of COD. The membrane was operated for a short time before clogging; its operational lifespan needs to be greatly extended before it can be used with the reactor in a community. Since there is no nutrient removal in the AER, the effiuent can be used for food production provided sufficient pathogens removal is achieved. Provided that the first compartment can be modified and the concentration of pathogens in the effluent is sufficiently reduced, the ABR can be considered for use in a community. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.

Providing water and proper sanitation to poor communities by 2015 is one of the United Nations targets for this millennium. In South Africa many communities aspire to waterborne sanitation. However, there is a technology gap for decentralized and sustainable waterborne sanitation systems capable of treating domestic wastewater (Foxon et al., 2006). Although domestic wastewater is more commonly treated using aerobic processes, anaerobic processes may be more appropriate for decentralized applications since they do not require aeration. Research is currently being undertaken to understand the behavior of a combined ABR-MBR unit for treating domestic wastewater. In this study, the anaerobic baffled reactor (ABR) was investigated by analyzing physico-chemical and biochemical data from experiments on a laboratory-scale ABR. This anaerobic reactor was treating complex particulate wastewater made up of sludge from the ventilated improved pit latrine toilets (known as VIP sludge). The main focus of this study was to establish the relationship between the increasing organic loading rates and the effluent characteristics (such as chemical oxygen demand: COD and extrapolymeric substances: EPS). The present work was structured in two parts; in the first part the reactor was operated at constant hydraulic retention time (HRT) without controlling feed characteristics. In the second part, the ABR was operated with step increases in organic loading rates. It was logistically not possible to provide a feed of real domestic wastewater to the laboratory-scale equipment. Consequently, a pit latrine sludge diluted with tap water was used to feed the ABR. This feed was found to have different biodegradability characteristics compared to domestic wastewater. However, the results still give insight into the performance of the ABR and into the treatability of VIP sludge. COD removal ranged from 52 to 80 % depending on the inlet COD. Some COD removal was due to solids retention in compartments, while it was estimated that only 28% of COD removal was due to biological degradation. Soluble extrapolymeric substances (proteins and carbohydrates) which are usually a by -product of anaerobic degradation were higher in the feed than in the effluent despite the increasing organic loading rates. However, more than 50 % of soluble extrapolymeric substances from the influent remained in the effluent and were found (in a parallel project) to influence membrane fouling in the membrane section of the experimental set-up (ABR-MBR unit). Parameters such as pH, conductivity, alkalinity, total and volatile solids were also investigated in this study. The pH decreased slightly from the inlet to the outlet during all runs even though the loading rates were increased. Conductivity increased significantly from influent to effluent with the increasing organic loading rates. Large amounts of total solids were retained in the reactor during the treatment process. Low alkalinity production was recorded during the operation of the reactor. In most cases, the data recorded in this study showed a low biological activity taking place while the reactor was working at room temperatures. Overall, up to 80% of removal efficiencies in terms of total COD and solids were recorded with increasing organic loading rates at constant hydraulic retention time. While these results do not allow the prediction of ABR-MBR performance during the treatment of real wastewater, it was concluded that: Most solids retention occurred in the feed tank. Most COD removal occurred as a result of solids retention and digestion. Loading characteristics did not strongly influence effluent EPS, pH or alkalinity, but did influence COD and conductivity. The relatively low biodegradability of the feedstock indicates that anaerobic digestion is not the most appropriate treatment for VIP sludge. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

Five species of methanogenic bacteria were analyzed for the presence of plasmid DNA. Several procedures for the detection and isolation of covalently closed circular plasmid DNA were modified for use with the methanogens.

This study examined: 1) if estimated performance times (ETcom) at four different distances can be used to accurately define the parameters of the critical velocity (CV) test [CV and anaerobic running capacity (ARC)]; and 2) if those parameters can be used to predict time to completion (PTcom) of distances performed at velocities greater than CV. Twelve subjects provided an ETcom for maximal-effort runs at 400m, 800m, 1600m, and 3200m. The CV and ARC were derived from the total distance (TD) versus ETcom relationship. The equation: PTcom = ARC / (velocity-CV) was used to determine the PTcom for runs at 200m, 600m, and 1000m. The PTcom was validated against the actual time to complete (ATcom) runs at the same three distances. The TD versus ETcom relationship was highly linear and indicated a close relationship between running distance and time. The PTcom overestimated the ATcom at 200m, but was not different from ATcom at 600m and 1000m. The PTcom and ATcom were not related at any of the three distances. The CV model could be applied to estimated performance times to derive the CV and ARC parameters, but the parameters of the test did not accurately estimate performance times above CV.

Eukaryotic organisms are divided into about 30 groups today, yet there still reamain many groups whose classification in the eukaryotic tree we are not sure about. This study focused on jacobids, a evolutionary important protist group from the Excavata taxa. Together with Heterolobosea, Euglenozoa and Tsukubamonadida, jacobids constitue a Discoba subgroup of Excavata taxa. Jacobids are significant mainly for their mitochondrial genome, which structurally resembles the original α-proteobacterial genome of the free-living ancestor of mitochondria. Some jacobids have their mitochondrial genome simplified, making them potential candidates for a model group used to study the mitochondrial evolution. However, too few members of jacobid group have been identified so far and the exact phylogeny of the group must be thoroughly understood for the detailed study of mitochondria evolution. This study focuses on broadening the taxonomic coverage of the jacobid excavate protists Andalucia. Twenty new strains of Andalucia have been established into stable culture, their morphology was assessed and SSU rDNA sequenced. Based on the phylogenetic analysis, Andalucia incarcarata species divides into three morphologically almost indistinguishable lines representing three species. Further, this study characterized a...