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The underlying mechanisms for nitrogen and phosphorus removal in high rate algal ponds used to treat brewery effluent; Harvesting algae using filter-feeding fish.
Expanded Title:Wastewater treatment using high rate algal ponds (HRAPs) is achieved through aerobic degradation of organic matter by bacteria and fungi. This degradation results in the release of substances such as carbon dioxide, phosphate and ammonia . The concentrations of these substances are lowered in the effluent through of bacterial nitrification, algal assimilation, volatilization, continuation of the abiotic N and P cycles, and phosphate precipitation. When the HRAPs are operating well, they effectively remove N and P from the wastewater. The aim of this work was to identify the organisms in the pond under different conditions and to monitor the change in nutrient concentration under these conditions, to develop a better understanding of which mechanisms were at work. Microalgae in the HRAP removed the N and P concentration in the brewery effluent through algal assimilation and probably made the greatest contribution under conditions conducive to micro-algal growth. Similarly, bacterial nitrification played a role and was responsible for the oxidation of ammonia. As much as 50% of the ammonia in the HRAP might have been removed from the system abiotically. Microalgal growth and nutrient removal were influenced by pH and temperature: summer conditions and slower flow rates favoured algal N removal; the removal of P also appeared to be related to algal assimilation. During winter and at increased flow rates, algal productivity and nutrient uptake decreased substantially. However, under these conditions there were shifts in the bacteria community structure that saw the proliferation of faster growing species such as the Proteobacteria, which have a high affinity for nutrients and include some nitrifying bacteria. This suggests that the mechanism of nutrient removal in the HRAP in winter and at increased flow rates (i.e. conditions that do not favour algal productivity) could shift in favour of bacterial nitrification.
Date Published:01/12/2016
Document Type:Research Report
Document Subjects:Wastewater Management - Sludge management, Wastewater Management - Sewers
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:2284/1/16
ISBN No:978-1-4312-0855-5
Authors:Jones CLW; Taylor R; Mogane M; Mayo M; Power S
Project No:K5/2284
Originator:WRC
Organizations:Rhodes University
Document Size:5 535 KB
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