Evaluation of factors responsible for high effluent suspended solids events in the Kuwahee wastewater treatment plant

by 1977- Moreno, Patricio Alejandro

The potential factors causing high effluent suspended solids (ESS) in Kuwahee Wastewater Treatment Plant (WWTP) are studied in order to properly identify the reason or reasons that might lead to focus future studies in proper remedial actions in the facility. In this document an analysis protocol is established, and several factors are evaluated for potential associations with high ESS events. From the protocol some of the factors were collected from regular operational procedure and others were collected during a study sampling period. The analysis of those factors included in the protocol showed no biological, or hydraulic, or settling parameters causing the suspended solids content to rise in the plant effluent. However, some flow distribution problems were found when the inflow to each clarifier was sampled and evaluated. This leaded to clarifier differences in performance that were corrected during the study period, after adjusting the flow openings to each clarifier. One of the most important evaluations carried out during the analysis, showed that the average suspended solid concentration taken at the effluent weir of the secondary clarifiers was smaller than the average ESS concentration taken at the overall plant effluent. This suggests the presence of another source of suspended solids contributing to the final ESS at the plant discharge flow. As part of the sampling procedure DSS/FSS testing was carried out on selected clarifiers. The clarifiers sampled during the sampling period were different from each other. The results showed that those clarifiers with flocculation well had a better performance than the one that has a conventional center well. However, the final statement could not be related for sure to the better performance of the flocculator clarifiers due to operational differences. In Kuwahee WWTP a secondary diversion is used when the inflow exceeds the maximum hydraulic capacity of the biological reactor. Since the diversion carries the flow from the primary clarifier effluent to the chlorination basin influent, it was thought ii to be one of the sources of high suspended solids events. In that, a simulation of different flows was run, in order to understand the incidence of the bypass in the final suspended solids concentration. The simulation showed that during bypass mode (secondary diversion is open) the overall plant ESS concentration increases with increasing diverted flow. Further study is suggested, along with possible solutions to high ESS problems. iii