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BABE Bio-Augmentation Batch Enhanced • • • • Principles Benefits Operational aspects Example NITRIFICATION • Nitrification is the limiting step in the design of activated sludge WWTP (SRT is the key design parameter in AS systems) • Certainly at lower temperatures • Augmentation of nitrifiers to the activated sludge plant effectivelyy reduces the minimal SRT needed. SRTm = 1 _________________________ μAmT - bAmT + addition rate 1 NITRIFICATION – BIOAUGMENTATION (1) • Addition of externally cultivated nitrifyers Often not effective because bacteria are not adapted to specific conditions of wastewater treatment plant If suspension of cells is used the bacteria fall prey to protozoa p NITRIFICATION – BIOAUGMENTATION (2) • Cultivate bacteria on the ammonium present in the sludge digestor effluent - Grow in flocs – Prevent predation - Combined effect: Less load to main treatment line and increased activity of nitrifyers in main line 2 BIO-AUGMENTATION (BABE) REACTOR (1) Influent Effluent Return sludge line Reject water from digester (T~>28oC) BABE reactor BIO-AUGMENTATION (BABE) REACTOR (2) • Only small fraction of return sludge used, using temperature advantage • Cultivate already present nitrifying population • 1 or 2 tank system to include denitrification • No need for biomass retention 3 BIO-AUGMENTATION (BABE) REACTOR (3) BABE: Bio-Augmentation Batch Enhanced Complete design and concept developed by mathematical simulation All processes relatively well known Many design variables can be easily tested Trial at lab scale will not easilyy be representative p Trial at pilot scale almost as expensive as full scale HIGH LOADED SYSTEM - EFFLUENT NH4-N With increase fraction of Nitrogen load in BABE reactor better nitrification at lower temperature 60 Efffluent NH4 -N (m g/l) • • • • normal 50 5% 40 10% 30 20% 20 30% 10 0 6 8 10 12 14 16 18 20 22 o Ambient Temperature ( C) 4 UPGRADING THE WALCHEREN WWTP (1) BY APPLYING THE BABE TECHNOLOGY Anoxic tank Aeration tanks 680 m3 5320 m3 Influent Q= 43215 S ttl Settler m3/d Effluent Return sludge line Excess sludge Sludge compartment 1650 m3 UPGRADING THE WALCHEREN WWTP (2) BY APPLYING THE BABE TECHNOLOGY Influent Anoxic tank Aeration tanks 680 m3 5320 m3 Settler Q= 43215 m3/d Effluent Return sludge line Recirculation Excess sludge Sludge compartment 1650 m3 Reject water Aerobic Anoxic 500 m3 350 m3 BABE reactor + COD addition (for pH balance) 5 UPGRADING THE WALCHEREN WWTP (3) Results of applying the BABE technology to the Walcheren wwtp Fractions F ti (mg/l) S O2 Total-N S NH 27 mg/l Without BABE Process Concentration in the main aeration tank 0.8 With BABE Process Reject water: return sludge 1:1 T BABE = 22 oC Concentration in the main aeration tank 0.8 25.4 9 S NO 2.2 7 X aut 80 2.5% 2800 154 4.7% 3100 %(X aut/X total) MLSS Reject water: return sludge 5:1 T BABE = 28 oC Concentration in the main aeration tank 0.8 Total-N 16 mg/l 10 40% improvement 6.6 148 4.2% 3100 COMPARISON: Conventional vs. BABE Upgrading Upgrading the treatment Upgrading the treatment Item plant by conventional plant by applying the method BABE concept Increase (additional volume/old volume) (%) Aeration volume Anoxic volume Side stream reactor Total increase 88 1300 0 225 50% reduction in area requirement 22 370 14 75 6 EFFECT SRT IN BABE REACTOR ON AUGMENTATION AMO OUNT OF NITRIFYERS ADDED D TO AT 15,0 12,5 10,0 7,5 5,0 2,5 0,0 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2 -2,5 25 -5,0 SLUDGE RETENTION IN BABE REACTOR (DAYS) A short SRT of around 0.3 to 0.8 days helps to increase nitrifiers population in more than 10%. COST ANALYSIS at WWTP WALCHEREN • • • • Saving in construction costs of 750.000 Euro; Additional costs for COD addition of 35 35.000 000 Euro/year; Additional sludge handling costs of 30.000 Euro/year; Saving in energy costs of 70.000 Euro/year; • The net yearly saving is about 115.000 Euro (Interest rate 6% , Depreciation 30 years). 7 CONCLUSIONS • SIDE STREAM TREATMENT OFFERS MANY NEW POSSIBILITIES FOR UPGRADING PLANT PERFORMANCE • EVALUATE EFFECT OF SIDE STREAM TREATMENT ON TOTAL PLANT EFFLUENT • PROCESS CHOICE IS HIGHLY PLANT SPECIFIC 8