INCLUDING THE EFFECTS OF BIOLOGICAL BULKING SLUDGE DURING THE SIMULATION OF WWTP ALTERNATIVES USING A GREY BOX MODEL

Transcription

1 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 Girona, Spain. Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, DK-28 Kgs. Lyngby, Denmark

2 - 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

3 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 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 ) 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

4 gtss m v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day Maximum Vesilind Settling Velocity (v ) 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 v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day

5 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 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, 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 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

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, v = 474 m day -1 v = 381 m day -1 v = 288 m day -1 v = 195 m day -1 v = 12 m day EFFLUENT 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 RASS TSS 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

7 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, INCREASE OF THE TSS IN THE MIDDLE LAYERS gtss m 3 6 gtss m layer time (days) layer time (days)

8 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