An evaluation of the eutrophication prevention potential of high rate Algae Ponds through the development of a deterministic design model
| dc.contributor.advisor | Brink, I. C. | en_ZA |
| dc.contributor.author | Van der Merwe, Izak Schalk Willem | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. | en_ZA |
| dc.date.accessioned | 2016-12-22T13:24:47Z | |
| dc.date.available | 2016-12-22T13:24:47Z | |
| dc.date.issued | 2016-12 | |
| dc.description | Thesis (MEng)--Stellenbosch University, 2016. | en_ZA |
| dc.description.abstract | 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. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Die suiwering van rioolwater is 'n groot probleem in Suid-Afrika. Suid-Afrika het oor die algemeen die nodige infrastruktuur vir rioolwater suiwering, maar het dikwels nie die vaardighede om hierdie rioolsuiweringsaanlegte doeltreffend te bestuur nie. Die toenemende eutrofikasie in die Suid-Afrikaanse varswaterbronne is 'n aanduiding dat hierdie probleem aangespreek moet word. Die eienskappe van 'n Hoë Konsentrasie Alg Dam (HKAD) maak dit 'n gewenste opsie vir die polering van die afvloeiwater van oneffektiewe rioolsuiweringsaanlegte in Suid-Afrika. Dit het die potensiaal om voedingstowwe (hoofsaaklik stikstof en fosfor) te verwyder asook te herwin uit die gedeeltelike of swak behandelde afvloeiwater van hierdie rioolsuiweringsaanlegte. Die eenvoudige bestuur van die HKAD sal verseker dat dit minder vatbaar is vir die slegte bestuurspraktyke in Suid-Afrika. Dit is ook relatief goedkoop om ʼn HKAD te bou en te bedryf, maar die groot voetspoor van hierdie poele maak sy lewensvatbaarheid grootliks afhanklik van die beskikbaarheid en koste van grond. Die voedingstofverwyderingspotensiaal van ʼn skaalmodel HKAD is onder laboratorium toestande ondersoek. Die gemete voedingstofverwyderingspotensiaal was matig weens 'n gebrek aan die hoë intensiteit sonlig wat die alge benodig vir fotosintese. Daar was wel aanduidings dat ʼn HKAD moontlik effektief in die warm en sonnige klimaat van Suid-Afrika kan wees. ʼn Deterministiese model is ontwikkel om ʼn HKAD voor te stel. Die deterministiese model is geprogrammeer in Microsoft Excel met die gebruik van Microsoft Visual Basics for Applications (VBA). Die deterministiese vergelykings is numeries opgelos in die rekenaar model. Die resultate van die eksperimente in die laboratorium is gebruik om die rekenaar HKAD model te kalibreer. Die gekalibreerde rekenaar model het die ammoniak en nitraat/nitriet konsentrasies akkuraat voorspel. Die model was onbevredigend in die voorspelling van die oplosbare reaktiewe fosfor (ORF) konsentrasie, aangesien dit nie die presipitasie van fosfor in berekening gebring het nie. Die model het slegs 'n beraming van die ORF gegee, wat deur die alge geassimileer is. Die gekalibreerde HKAD model is gebruik om die voedingstofverwyderingspotensiaal van 'n HKAD in Suid-Afrika te ondersoek. Daar is vasgestel dat ʼn HKAD vlak, ʼn lang retensietyd en gevolglik met ‘n groot oppervlakte moet hê om bevredigende voedingstofverwydering te bereik. Dit is beraam dat om ongeveer 100% Totaal Anorganiese Stikstof verwydering te bereik, die oppervlak van die HKAD in die omgewing van 60 vierkante meter per kubieke meter van die daaglikse vloei moet wees. Ammoniak verwydering vereis 'n kleiner area van ongeveer 20 m2/m3/dag vir 100% ammoniak verwydering. Dit is ook vasgestel dat HRAPs het die vooruitsig van noemenswaardige ORF verwydering. Die teoretiese berekeninge van die deterministiese HKAD model het aangedui dat 'n HKAD potensieel voldoende voedingstofverwydering vir effektiewe eutrofikasie voorkoming kan bereik. Die groot oppervlakte vereistes vir hierdie voedingstofverwydering maak die HKAD moontlik nie prakties uitvoerbaar vir die polering van afvloeiwater nie. | af_ZA |
| dc.format.extent | xvi, 142 pages : illustrations, maps | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/100186 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Algae -- Ponds, Storm water retention | en_ZA |
| dc.subject | Wastewater treatment plants | en_ZA |
| dc.subject | Water -- Purification | en_ZA |
| dc.subject | Wastewater -- Treatment model | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | An evaluation of the eutrophication prevention potential of high rate Algae Ponds through the development of a deterministic design model | en_ZA |
| dc.type | Thesis | en_ZA |