INCLUDING THE EFFECTS OF BIOLOGICAL BULKING SLUDGE DURING THE SIMULATION OF WWTP ALTERNATIVES USING A GREY BOX MODEL Xavier Flores-Alsina, Joaquim Comas, Ignasi Rodriguez-Roda and Krist V. Gernaey Laboratory of Chemical and Environmental Engineering, University of Girona, Montilivi Campus s/n 1771. Girona, Spain. Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, DK-28 Kgs. Lyngby, Denmark
- MOTIVATION -Biological bulking sludge is the most common problem associated with poor activated sludge separation -Although the recent developments in WWTP modeling, the mechanics of filamentous bacteria growth are not clear -Grey box models are presented as promising tools to handle these type of problems -The objective of this study is to include the effects of biological bulking sludge during the simulation of WWTP alternatives -In this way, it is possible a more realistic plant performance evaluation
F/M_1 SRT BOD 5 /N &/or F/M_2 S BOD 5 /P S Notlow Nothigh ANOX1 ANOX2 AER1 AER2 AER3 F/M_1 (kg COD removed/kg MLVSS d) 1 Bulking occurred safety zone.2 1 5 Aeration Basin DO conc., mg/l High Low or significant oscillations Low SRT Not low EXTERNAL RECIRCULATION due to low DO (Aerobic Bulking) due to nutrient deficiency due to low organic loading v (m day 1 ) 25 2 15 1 v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 5 v sj = v * j rh X e v e r p X * j 2 4 6
gtss m -3 1 8 6 4 2 v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 5 4 3 Maximum Vesilind Settling Velocity (v ) 2 1 4 2 1 8 6 layer v sj = v * j rh X e v WORSE COMPACTION INCREASE OF TSS IN THE MIDDLE LAYERS DECREASE OF THE ACTIVATED SLUDGE CONCENTRATION DECREASE OF THE EFFLUENT QUALITY e r p X * j 5 4 3 2 1 v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 3 4 5 6 14 12 1 8 6 4 2 v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 3 4 5 6 1 8 6 4 2 v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 3 4 5 6
F/M_1 SRT BOD 5 /N &/or F/M_2 S BOD 5 /P S Notlow Nothigh INTERNAL RECIRCULATION 1,,95 v = 474 m day -1 v = 381 m day -1 F/M_1 (kg COD removed/kg MLVSS d) 1 Bulking occurred safety zone.2 1 5 Aeration Basin DO conc., mg/l Low or significant oscillations Low High SRT ANOX1 ANOX2 AER1 AER2 AER3 Not low risk of bulking,9,85,8,75,7,65 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 EXTERNAL RECIRCULATION due to low DO (Aerobic Bulking) due to nutrient deficiency due to low organic loading WASTE,6 3 4 5 6 F/M ratio (kgdbo 5 kgtss -1 day -1 ),34,32,3,28,26,24,22,2,18,16,14 v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 3 4 5 6 SRT (days) 9,5 9, 8,5 8, 7,5 7, 6,5 6, v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 3 4 5 6
INTERNAL RECIRCULATION 1,,95 v = 474 m day -1 v = 381 m day -1,9 v = 288 m day -1 v = 195 m day -1 ANOX1 ANOX2 AER1 AER2 AER3 risk of bulking,85,8,75,7 v = 12 m day -1,65 EXTERNAL RECIRCULATION WASTE,6 3 4 5 6 1 8 6 4 2 v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 3 4 5 6 EFFLUENT TSS 1 9 8 7 6 5 v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1 3 4 5 6 RASS TSS 5 48 46 44 42 4 38 36 34 32 3 4 5 6 AER3 TSS v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day -1
1, v = 474 m day -1,95 v = 381 m day -1,9 v = 288 m day -1 v = 195 m day -1 ANOX1 ANOX2 AER1 AER2 AER3 risk of bulking,85,8,75,7 v = 12 m day -1,65 EXTERNAL RECIRCULATION,6 3 4 5 6 1 2 4 6 8 1 1 2 4 6 8 1 INCREASE OF THE TSS IN THE MIDDLE LAYERS 8 8 6 gtss m 3 6 gtss m 3 4 4 2 8 6 layer 4 2 25 6 55 5 45 4 35 3 time (days) 2 8 6 layer 4 2 25 6 55 5 45 4 35 3 time (days)
So far.with THE PROPOSED APPROACH IS POSSIBLE 1- A more realistic plant performance during the simulation of WWTP alternatives 2- A worse compaction in the lower layers of the secondary settler, a less concentrated in solids Q r and Q w flows, a decrease of the activated sludge concentration in the aeration basin and finally a worse overall pollution removal efficiency In future.what MUST BE DONE? 1 sensitivity of the approach when the operating conditions are changed e.g. Qcarb, Qw, Kla, Qintr. 2 Performance of the approach when several control strategies are implemented. Are they capable to handle a bulking episode? study of synergies and trade-off between the suitable operating condition for N removal (low F/M and high SRT) and risk of bulking