An?lisis temporal y espacial de los proceso relacionados con ox?geno disuelto en lagunas de maduraci?n.
- Authors
- Ar?valo Durazno, Mar?a Bel?n
- Format
- MasterThesis
- Status
- publishedVersion
- Description
Stabilization ponds represent a very convenient way of treating wastewater characterized by low construction cost, low maintenance and relatively very low energy consumption. Maturation ponds are the last step when series of stabilization ponds are used. Their main objective is the removal of pathogenic organisms. Some pathogen-killing mechanisms are directly related to solar radiation, pH and dissolved oxygen concentrations, in this type of lagoons. The significance of the presence of oxygen in maturation ponds lies in the control of disinfection and odors. Moreover, the discharge of treated water characterized by high oxygen concentration has a lower impact on the receiving surface water. Thus, the spatial and temporal changes in dissolved oxygen concentrations can give an insight of pathogen removal status in those ponds. Dissolved oxygen levels depend on several production and consumption processes that involve physical, chemical and biological parameters. In this thesis, statistical analyses, using mixed effects models, were used for testing the influence of different variables through space and time, on dissolved oxygen concentrations in the maturation ponds of the wastewater treatment plant of Cuenca (Ecuador). First, an evaluation of the variability of dissolved oxygen concentrations depending on the location within each pond, on the depth (surface and bottom layers), timing (hour of the day) and between the two lanes of treatment (maturation 1 and maturation 2) was carried out. Furthermore, the influence of meteorological factors (wind speed, air temperature, and solar radiation), chemical parameters (BOD, COD, P, N, and pH) and biological parameters (chlorophyll a, macroinvertebrates) on dissolved oxygen concentrations was tested. Finally, using the most influential parameters, models for predicting dissolved oxygen and biochemical oxygen demand in such ponds were developed. Depth was the most significant factor affecting dissolved oxygen, since most of the variables analyzed presented p values lower than 0.005 when combined with depth. Contrary to what was expected, dissolved oxygen concentrations varied between pond 1 or pond 2, what suggested that the loading and related water quality differs in each pond. Meteorological factors did not show any significant effect on dissolved oxygen. Only air temperature, depending on the pond, did show influence on dissolved oxygen concentration. Phosphorus present in maturation ponds, depending on the hour of the day, presented an effect on dissolved oxygen concentrations (p value = 0.05). Nitrogen and pH, on the other hand, only showed significance in one of the two ponds analyzed. Further, chlorophyll a, as a proxy for algal biomass concentration, had a positive correlation with dissolved oxygen following similar trends with higher concentrations closer to the surface. The Pearson?s coefficients calculated for the predictive models developed showed that six out of eight equations can be a good tool for predictions. Although this study covers a wide set of physical and chemical parameters related to oxygen processes in maturation ponds, it should be recognized that the data set used was limited, therefore it is necessary to further study the oxygen related processes with higher amount of data and extending it to a longer period of time.
El presente estudio analiza los cambios en el tiempo y espacio de los niveles de ox?geno disuelto en las lagunas de maduraci?n de PTAR de Ucubamba, Cuenca-Ecuador. Estos cambios pueden dar una idea del estado de desinfecci?n que se est? dando en estas lagunas. An?lisis estad?sticos, usando modelos de efectos mixtos, fueron usados para probar la influencia de diferentes variables en el espacio y tiempo, sobre las concentraciones de ox?geno disuelto. Luego, usando los par?metros con mayor influencia, se construyeron modelos para la predicci?n de ox?geno disuelto.
- Publication Year
- 2014
- Language
- eng
- Topic
- INGENIER?A AMBIENTAL
TRATAMIENTO DE AGUA RESIDUAL
MODELOS ESTAD?STICOS
LAGUNAS DE MADURACI?N
CLIMA TROPICAL
- Repository
- Repositorio SENESCYT
- Rights
- openAccess
- License