Filamentous Bulking Control and Process Dynamic Control in Enhanced Biological Phosphorus Removal System

• Main Authors: Chang, Wei-Chin, 張維欽
• Other Authors: C.F.Ouyang, W.L.Chiang
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/28445729987229830225

博士 === 國立中央大學 === 環境工程學系 === 85 === ABSTRACTIncorporating phosphate into the biomass is the only feasible means of removing phosphate from wastewater in an enhanced biological phosphorus removal (EBPR) system, accounting for why biomass-liquid seperation primarily influences the overall system''s performance. This study investigates the behavior of biomass-liquid separation in the EBPR process under steady-state and dynamic influent wastewater loading.In the steady-state experiments, a specific parameter, i.e. specific residual substrate utilization rate , is developed to evaluate the filamentous bulking potential in the design of an enhanced biological phosphorus removal (EBPR) process. Continuous- flowpilot-plant experiments employing synthetic wastewater are performed at different SRTs (5, 10, 15 days) and anaerobic: aerobic volume ratios, Van:Va (1:9, 1:4, 1:2.3). Experimental results reveal that surpass anaerobic phosphate release concentration to be an indicator of metabolic selection for bulking control, owing to its strong correlation with SVI. Whereas, the effect of on SVI can not be consistently explained under different SRTs. This comparison implies that the specific utilization of residual substrate left for filaments in aerobic zone is the primary factor influencing SVI. Furthermore, eliminating the access of filaments in the aerobic zone to substrate exerts a more influence on SVI than favoring poly-p microorganisms: the main floc-formers in the EBPR process. These findings infer that, in the design stage of the EBPR process, carbon sequestration by poly-p microorganisms in the anaerobic zone should be maximized so as to yield a lower in the aerobic zone. Also, the simultaneous process requirements of phosphorus removal and bulking controlare demonstrated in the design procedure of EBPR process by combining with the kinetic modeling of phosphorus removal. More, this study presents a specific process control strategy, i.e. sludge pre-recycle control, for a dynamic EBPR system by intergratedly considering two factors: (1) appropriately controlling F/M ratio in the anaerobic zone and (2) eliminating hydraulic shock in the secondary clarifier. Fuzzy logic inference is also introduced while constructing an on-line controller owing to the ill- defined characteristics of the dynamic EBPR system. For comparison, continuous-flow pilot plant experiments with automatic monitoring and real-time control facilities are performed using two control strategies: sludge pre-recycle control and conventional (F/M)an control. Experimental results indicate that similar effluent ranges of dissolved COD and dissolved phosphate can be obtained from the two strategies owing to their similar (F/M)an ratios. However, reliability analysis reveals that sludge pre-recycle control significantly improves the effluent total SS concentration than conventional (F/M)an control because of the reduction of hydraulic loading in the clarifier. Therefore, sludge pre-recycle control is highly desired owing to the ability to reduce the hydraulic loading in the secondary clarifier at peak loading period while, at the same time, maintain a similar (F/M)an ratio in the biological reactor as conventional (F/M)an control. Moreover, statistical correlation of effluent qualities indicates that suspended COD and suspended phosphorus contents are proportional to total SS. Based on these findings, we can infer that when in the operation stage, the effluent total SS control is a critical consideration of system performance. Such an inference again verifies the effectiveness of sludge pre-recycle control: introducing the hydraulic loading factor into the control strategy.