Stimulation of aerobic and anaerobic biological processes by ultrasound

Transcription

1 Stimulation of aerobic and anaerobic biological processes by ultrasound Uwe Neis Prof. Dr.-Ing. (em.) Technical University Hamburg-Harburg Institute of Wastewater Management and Water Protection

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3 Izabela Banduch Dr.-Ing., Technical University Hamburg-Harburg, Institute of Wastewater Management and Water Protection; scholarship DBU 10/2007-5/2011, magister TU Lodz, Poland Klaus Nickel Dr.-Ing., CEO Ultrawaves GmbH, Hamburg, Germany; BMBF research fellow TU Hamburg-Harburg

4 Outline Full scale applications of ultrasound Anaerobic Sludge Digestion Aerobic Activated Sludge Process Ultrasound / acoustic cavitation - principles Ultrasound on aerobic biomass - recent research

5 Anaerobic Digestion Improvement Volatile solids reduction by anaerobic degradation VS redu uction [%] Digestion time [d]

6 Anaerobic Digestion Improvement the rate determining step of anaerobic sludge degradation is sludge hydrolysis scientific/technical approach to overcome limitations: disintegration of sludge prior to fermentation

7 Bamberg WWTP, Germany

8 Bamberg WWTP, Germany Ultrasound installation in 2004: Sonication of 30% (in 2004) - 80% (in 2007) of the TWAS (~ kwh/m³ SONICATION THICKENED WAS DIGESTER 1 DIGESTER 3 PRIMARY SLUDGE DIGESTER 2 8

9 Bamberg WWTP, Germany

10 Bamberg WWTP, Germany zugeführtetrockenmasse e im Rohschlamm (m 3 /a) 9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1,000 zugeführte Trockenmasse im Rohschlamm Gasmenge ges. 2,600,000 2,400,000 2,200,000 2,000,000 1,800,000 1,600,000 1,400,000 1,200,000 1,000, , , , ,000 Gasmen nge ges. (m 3 /a) Zeit

11 Bamberg WWTP, Germany biogas production VS degradation biogas produ uction [1000 m 3 /a] VS degra radation [%] year 0

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13 Meldorf WWTP, Germany Combating foaming digester activated sludge tank secondary clarifier WAS thickener WAS sonication 100 % digester

14 Meldorf WWTP, Germany Compact Generator for Five Sonotrodes Instrumentation Panel * Optional Sound Enclosure Sonolyzer TM 5 kw Reactor Module * Customized for this plant

15 Activated Sludge Process Improvement Status in 2006 Designed for pe Load pe Nitrification/Denitrification Sludge age Θ=22 d Bulking sludge in winter Low dewaterability of sludge Bünde WWTP Results Significant reduction of N in effluent (N < 5mg/l) No foam/bulking sludge on AS tanks Reduction of excess sludge by 25% Dewaterability of digested sludge +2% Test March June 2006 US on partial stream of WAS (30%) Back in anoxic zone Installation of US system Sept 2006

16 Activated Sludge Process Improvement Bünde WWTP enhancing N removal primary sedimentation activated sludge tank secondary clarifier WAS thickener WAS sonication 30% 70%

17 Activated Sludge Process Improvement Seevetal WWTP - Bulking Sludge Control

18 Seevetal WWTP no US control

19 Seevetal WWTP with US control

20 Ultrasound / Acoustic Cavitation - Principles

21 Ultrasound / Acoustic Cavitation - Principles Sound pressure P = P A sin2π f t (kpa) (P A ) 2 = 2 I ρ c I = sound intensity (W/cm 2 ) c = λ f (m/s) λ = wave length (m) f= frequency (s -1 ) + P A Sound waves in µm Radius of bubbles Creation Growth Implosion Hot Spot Time in µs

22 Acoustic Cavitation Ultrasonic horn Ultrasonic pressure field

23 Ultrasonic Impact on Activated Sludge (Biomass) sludge floc liquid bacteria inert particle extra-cellular polymer

24 Ultrasonic Impact on Activated Sludge (Biomass) Impact on soluble phase (< 0.45µm) COD luble COD [mg/l] increase in sol energy input [Wh/l] Waste activated sludge sample, thickened: TS = 6.5%, VS = 74.1%

25 Ultrasonic Impact on Activated Sludge (Biomass) ed (0,45µm) (mg/g VSS) Proteins dissolve Impact on soluble phase proteins Activated sludge WWTP Seevetal y = 0,8956x + 4,6708 R 2 = 0,8335 y = 0,5565x + 0,836 R 2 = 0, Ultrasound dose (Wh/l) Sept./Oct (Bolle) Nov (Gonzalez)

26 Ultrasonic Impact on Activated Sludge (Biomass) 45 Oxygen Uptake Rate c (mgo 2 /g VSS*h) OUR specific Activated sludge WWTP Seevetal 0 0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0 9,0 10,0 Ultrasound dose (Wh/l) Oct.06 (Sun) (Leppien) (Leppien) (Leppien) (Leppien) (Leppien)

27 Ultrasonic Impact on Activated Sludge (Biomass) 2,0 1,9 1,8 Messwerte Median Enzymatic activity US / INT-DHA 0 INT-DHA 1,7 1,6 1,5 1,4 1,3 1,2 1,1 1,0 0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 Energieeintrag [Wh/l]

28 Ultrasound on activated sludge and M.parvicella - Scanning electron microscopy, SEM - Transmission electron microscopy, TEM

29 Activated Sludge - Scanning electron microscopy Activated sludge floc

30 Activated Sludge - Scanning electron microscopy 10 (Wh/L)

31 Activated Scanning Sludge - Scanning electron microscopy electron microscopy Activated sludge floc no US

32 Activated Scanning Sludge - Scanning electron microscopy electron microscopy 9 (Wh/L)

33 Activated Scanning Sludge - Scanning electron microscopy electron microscopy 20 (Wh/L)

34 M. parvicella - SEM 2 (Wh/L) 5 (Wh/L)

35 M. parvicella - TEM 10 (Wh/L)

36 Ultrasound /Acoustic Cavitation - Principles Sound pressure P = P A sin2π f t (P A ) 2 = 2 I ρ c; P A = a I I = Sound intensity (W/cm 2 ) c = λ f (m/s) Example f=20 khz (20,000s -1 ), c=1,500 ms -1 in water, λ=7.5 cm, Ultrawaves sonotrode operates at I = 25 (W/cm 2 ) P A = N m -2 or sound pressure oscillations between +8.5 to 8.5 atm (at 20,000 times per second)

37 Ultrasound impact on biomass Conclusion The impact of high-power ultrasound at low/moderate energy input on microbial biomass is caused by cavitation and sound pressure oscillations: floc deagglomeration better diffusion and mass transfer of substrates and oxygen, release of extracellular EPS (proteins, carbohydrates, ) cell wall opening and damage cytoplasma is attacked and released, release of well degradable soluble DOC, release of proteins. intensifies aerobic as well as anaerobic processes

38 Thank you for your attention Come and visit Ultrawaves Co. in hall A2, stand 529