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Ph as a real-time control parameter in swine wastewater treatment

University of British Columbia

The main objective of this research was to evaluate the effectiveness of pH as a real-time control parameter in swine wastewater treatment. This real-time control process was implemented into a Two Stage Sequencing Batch Reactor (TSSBRs) system. The first SBR is known as the Anoxic/Oxic (A/O) reactor. The real time process was applied here as most of the reactions occurred in this reactor. The second reactor is known as the anoxic reactor and was mainly designed for nitrate removal. The reproducibility of the pH patterns was tested under three different organic loadings. The treatment efficiencies for C, N, and P were examined to determine the capability of this newly developed process. The pH pattern was also compared to the more established ORP pattern for the purpose of cross-referencing. The differences between an attached growth system using Ringlace as a medium and a suspended growth system, both using the same real-time control strategy, were also examined in this research. It was determined from the results of this study that pH can be a valuable parameter in a real-time control process. The pH patterns were consistent and uniform, despite the fluctuations in wastewater concentrations. The pH pattern clearly demonstrated its ability to monitor all the respiratory states. Several well defined control points on the pH curve such as the nitrate apex during the anoxic phase, and the Nitrogen Break Point (NBP) and Residual Carbon Manipulation Point (RCMP) during the aerobic phase were identified. The clarity of each feature makes real-time control using pH possible. It should be noted that the time allotted for the anoxic phase was four hours, while the aerobic phase was adjusted by the real time control process with the control point set in between the NBP and RCMP. The success of this real-time control process was marked by the flexible HRT provided for the system. It was found in this research that the application of the real-time process either ensured a complete removal of carbon and ammonia, or reduced the overall cycle time (maximized energy savings). A constant effluent quality was also produced for each run. It was demonstrated in this study that the treatment efficiency for nitrate and phosphorus can be greatly affected by the carbon content in the wastewater. It was found that the optimal treatment efficiency for each nutrient (C, N, and P) was achieved during the high organic loading run. The high nutrient loading rate ensured rapid denitrification and phosphorus release during the anoxic phase, while creating a favourable environment for carbon oxidation, nitrification, and phosphorus uptake during the aerobic stage. It was also found that the anoxic reactor was not needed under conditions of high organic loadings. A high carbon content in the influent created simultaneous nitrification/denitrification in the aerobic phase. This reduced the nitrate loading into the anoxic reactor. From the results of this research, it was found that pH pattern correlated well with the ORP curve. Each distinct feature identified on the pH curve coincided with the ORP pattern. The ORP pattern was affected more by the aeration rate than pH. Nonetheless, it can be concluded that both pH and ORP can be used as a real-time control parameter. The results obtained from this research suggested that the only difference between the attached growth and suspended growth systems was the hydraulic retention time. The higher biomass retained in the attached growth system enabled the bacteria to complete the necessary reactions in a shorter period of time. The effluent quality produced from both systems were virtually the same for each run.

Thesis/Dissertation

application/pdf

2009-05-21

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http://hdl.handle.net/2429/8025

Chemical and Biological Engineering

University of British Columbia

UBCV

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