A high rate biofilm contact reactor for winery wastewater treatment

[摘要] ENGLISH ABSTRACT: Winemaking produces variable volumes wastewater rich in biodegradable organicmaterial, with fluctuating chemical composition and pH values according to theseasonal activities of the cellar. Releasing untreated winery wastewater into theenvironment can cause eutrophication and toxicity in surface water and hasdetrimental effects on soil condition and ground water quality. Rising costs of effluentdisposal, limited availability of freshwater resources and increasingly stringent wateruse regulations imposed on wineries are enthusing interest in low cost, sustainable,and robust wastewater treatment solutions for wineries. The objective of this studywas to design, construct and implement an easily pre-assembled, energy efficient pilotscale biofilm reactor with a small footprint for winery wastewater treatment. Acommercial 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 removalefficiency of the system. The double-unit pilot system was tested in six trials overthree years. The system showed effective, robust treatment of winery wastewater ofvarying strengths with minimal solid waste production, consistently reducingchemical oxygen demand (COD) (average 93% reduction), total nitrogen, sulfate,phosphate and suspended solids (average 90% reduction) to meet prescribedregulations for irrigation. The system performed at its peak when treating highlyconcentrated wastewater during harvest season. The pH of treated wastewater wasconsistently buffered from highly acidic and basic values to close to neutral. Tounderstand how the biofilm worked to remove contaminants within the system, andhow the additional cooling tower unit expanded the treatment scope of the system, athree-tiered investigation of the microbial community structure, distribution ofmicroorganisms and collective metabolic capabilities of biofilm samples from eachcooling tower subunit was investigated. Next generation sequencing revealed that thebiofilm populations of the two reactor subunits were phylogenetically distinct, withonly 12% of operational taxonomic units (OTUs) overlapping between the twobiofilms. Taxonomic data indicated that carbohydrate reducing bacteria dominated thepopulation of the first cooling tower, while nitrifying and denitrifying bacteriadominated the second. Fluorescent in situ hybridization coupled with confocal laser scanning microscopy (FISH-CLSM) revealed the stratified distribution of aerobicGammaproteobacteria across the depth of the biofilm from the first cooling towerunit, and showed distinct distribution patterns of Nitrosomonas and Nitrospirae inbiofilm samples from the first and second cooling tower units. Substrate utilizationanalyses using the Biolog system revealed that the majority of the carbon substratesthat were tested were utilized in the biofilm samples from both cooling towers, butthat important metabolic utilization capabilities fell exclusively either within theconsortium of the biofilm from tower 1 or tower 2. Collectively, the data from each ofthe three analytical approaches indicated that by adding a second subunit to thebioreactor, the treatment capacity of the system was not merely expanded, but that thesecond reactor subunit added to the microbial and metabolic diversity of the system.

[发布机构] Stellenbosch University