Abstract:
This thesis examines and presents a first stage assessment of the potential improvement of waste-water treatment plant performance by including an equalization process as part of the treatment train of the Gammams Water Care works in Windhoek, Namibia. The treatment plant’s operational objective of achieving compliant final effluent quality on a consistent basis is hampered by influent hydraulic and pollutant load daily diurnal pattern variations oppose to a near uniform condition experienced. These non-uniform hydraulic and pollutant loading conditions impose a negative impact on achieving overall optimal treatment plant performance.
During the study, daily variations in hydraulic and pollutant loading at the Gammams Water Care Works were established and a representative day of a typical week identified for the equalization process attenuation capacity design in order to minimize both flow and pollutant load diurnal pattern variations. Furthermore, a comparative analysis of equalised and unequalised treatment scenarios on overall plant performance was done by applying both numerical and graphical analysis methodologies aided by the STOAT computer software simulation model. This study uniquely made a comparative analysis of the current Gammams Water Care Works treatment train (which currently operates without an equalization step) using the STOAT model, considering both unequalised and equalised process equalization scenarios.
The graphical or Ripple method and a numerical time-step method were employed for equalization process attenuation capacity determination. The numerical time-step method together with STOAT modelling steady state simulations were employed for this 1st approximation step analyses, for initial comparison and impact assessment as well as for identifying the road map for further future detailed extended-time simulation purposes.
The study found that the plant typically experiences diurnal daily influent hydraulic and pollutant load variations similar to other plants receiving mainly domestic wastewater in the early morning hours and between midday and early evenings. For STOAT modelling purposes, current plant influent and subsequent unit process outflows along the treatment train were sampled and selected pollutant concentrations were determined over 4-hour intervals for the representative dry weather weekday mentioned before. The STOAT model calibration was limited to the actual Gammams plant treatment train, unit process sizes and operational criteria employed. Bio-chemical process kinetic algorithms inherent to the STOAT model was not changed due to the software limitations of use and not being allowed. The analysis done of unequalised and equalised scenarios was thereof of a comparative nature.
