Browsing by Author "Van der Merwe, Izak Schalk Willem"

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    An evaluation of the eutrophication prevention potential of high rate Algae Ponds through the development of a deterministic design model
    (Stellenbosch : Stellenbosch University, 2016-12) Van der Merwe, Izak Schalk Willem; Brink, I. C.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: Wastewater treatment is a major problem in South Africa. South Africa generally has the wastewater treatment infrastructure in place but often lacks the labour skills to operate these plants efficiently. The increasing eutrophication in South African water bodies is an indication that this problem needs to be rectified. The characteristics of a High Rate Algal Pond (HRAP) make it an attractive option for effluent polishing in South Africa. It has the potential of simultaneous nutrient removal and nutrient recovery from the partially or poorly treated effluent of wastewater treatment works. Its simple operation would ensure that it is less susceptible to the poor operation practices in South Africa. It is also relatively inexpensive to construct and operate, but the large footprint of these ponds makes its feasibility largely dependent on the availability and cost of land. A scale model HRAP was operated under laboratory conditions to investigate the nutrient removal potential of these ponds. The nutrient removal measured during the laboratory experiments was believed to be modest, due to a lack of the high-intensity sunlight that the algae require for photosynthesis. However, these were promising indications that the HRAP might be effective in the warm and sunny climate of South Africa despite the modest nutrient removals measured in the laboratory experiments. A deterministic design model for an HRAP was developed. The deterministic design was programmed into Microsoft Excel with the use of Microsoft Visual Basics for Applications (VBA). The deterministic equations were solved numerically in the computational model. The results obtained from the laboratory experiments were used to calibrate the computational HRAP model. The calibrated computational model accurately predicted the ammonia and nitrate/nitrite concentrations. It was unsatisfactory in predicting the soluble reactive phosphorus (SRP) concentration since it did not account for phosphate precipitation. The model only gave an estimation of the SRP assimilated by algae. The calibrated HRAP model was used to investigate the nutrient removal potential of an HRAP in South Africa. It was established that shallow ponds with long retention times, and consequently large surface areas, are required to achieve satisfactory nutrient removal. The area requirement of an HRAP was estimated at approximately 60 square meters per cubic meter of daily flow to achieve roughly 100% Total Inorganic Nitrogen removal. The estimated area requirement for roughly 100% ammonia removal was approximately 20 m2/m3/day. It was also established that HRAPs has the prospect of notable SRP removal. The theoretical calculations of the deterministic HRAP model indicated that an HRAP could potentially achieve sufficient nutrient removal for effective eutrophication prevention. However, the large surface area requirements might not make the HRAP practically feasible for effluent polishing in most cases.