Department of Biochemistry

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Browsing Department of Biochemistry by browse.metadata.advisor "Botes, Marelize"

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    A high rate biofilm contact reactor for winery wastewater treatment
    (Stellenbosch : Stellenbosch University, 2016-12) De Beer, Danielle Marguerite; Cloete, Thomas Eugene; Swart, Pieter; Botes, Marelize; Stellenbosch University. Faculty of Science. Dept. of Biochemistry.
    ENGLISH ABSTRACT: Winemaking produces variable volumes wastewater rich in biodegradable organic material, with fluctuating chemical composition and pH values according to the seasonal activities of the cellar. Releasing untreated winery wastewater into the environment can cause eutrophication and toxicity in surface water and has detrimental effects on soil condition and ground water quality. Rising costs of effluent disposal, limited availability of freshwater resources and increasingly stringent water use regulations imposed on wineries are enthusing interest in low cost, sustainable, and robust wastewater treatment solutions for wineries. The objective of this study was to design, construct and implement an easily pre-assembled, energy efficient pilot scale biofilm reactor with a small footprint for winery wastewater treatment. A commercial cooling tower as a trickling filter reactor unit was central to the design. The system was tested at a winery in Stellenbosch and after proving to be effective, was up-scaled by adding a second cooling tower to the system as a secondary reactor, treating the effluent from the first subunit, contributing to the overall waste removal efficiency of the system. The double-unit pilot system was tested in six trials over three years. The system showed effective, robust treatment of winery wastewater of varying strengths with minimal solid waste production, consistently reducing chemical oxygen demand (COD) (average 93% reduction), total nitrogen, sulfate, phosphate and suspended solids (average 90% reduction) to meet prescribed regulations for irrigation. The system performed at its peak when treating highly concentrated wastewater during harvest season. The pH of treated wastewater was consistently buffered from highly acidic and basic values to close to neutral. To understand how the biofilm worked to remove contaminants within the system, and how the additional cooling tower unit expanded the treatment scope of the system, a three-tiered investigation of the microbial community structure, distribution of microorganisms and collective metabolic capabilities of biofilm samples from each cooling tower subunit was investigated. Next generation sequencing revealed that the biofilm populations of the two reactor subunits were phylogenetically distinct, with only 12% of operational taxonomic units (OTUs) overlapping between the two biofilms. Taxonomic data indicated that carbohydrate reducing bacteria dominated the population of the first cooling tower, while nitrifying and denitrifying bacteria dominated the second. Fluorescent in situ hybridization coupled with confocal laser scanning microscopy (FISH-CLSM) revealed the stratified distribution of aerobic Gammaproteobacteria across the depth of the biofilm from the first cooling tower unit, and showed distinct distribution patterns of Nitrosomonas and Nitrospirae in biofilm samples from the first and second cooling tower units. Substrate utilization analyses using the Biolog system revealed that the majority of the carbon substrates that were tested were utilized in the biofilm samples from both cooling towers, but that important metabolic utilization capabilities fell exclusively either within the consortium of the biofilm from tower 1 or tower 2. Collectively, the data from each of the three analytical approaches indicated that by adding a second subunit to the bioreactor, the treatment capacity of the system was not merely expanded, but that the second reactor subunit added to the microbial and metabolic diversity of the system.