Reduction of excess sludge production in a conventional activated sludge system by a new electromagnetic treatment Dr.-Ing. Eric Valette Planet Horizons Technologies SA CTO CH-3960 Sierre, Switzerland
Summary � Introduction � First trials in a laboratory scale � Full-scale installation � Full-scale results � Perspectives � Conclusion
Introduction Goal: reduction of excess sludge production Processes: � Physical and chemical treatments � Mechanical treatments � Biochemical treatments � Increase in dissolve oxygen Alternative way: � Electromagnetic treatment
Laboratory scale trials E R Set-up: Ref line R.Q 0 = 4 L/h E (1+R).Q 0 = 6 L/h B Q L = 2 L/h Réfrigérateur V = 6 L Bio V = 22,5 L Décanteur Q 0 = 2 L/h Q 0 = 2 R.Q 0 = 4 L/h L/h (1+R).Q 0 = 6 L/h Q L = 2 L/h Electrodes EM line V = 6 L AC Bio V = 22,5 L Décanteur
Laboratory scale trials Electromagnetic device: Electronic command: •2 frequencies (50 Hz to 20 kHz) •Tension (< 100 V) •Electromagnetic induction: few pico to few nanoTeslas Antenna: •2 specific wires around the tank
Laboratory scale trials Operating conditions: � Different conditions were studied, the following results are obtained while maintaining the extraction flow constant. TS in Flow rate of COD in COD in TS in excess aeration influent: Q 0 influent: effluent: sludge: tank: (l h -1 ) (mgO 2 l –1 ) (mgO 2 l –1 ) (gTS L -1 ) (gTS L -1 ) REF- 162 ± 32 4.97 ± 0.9 7.1 ± 1.4 2 line 548 ± 11 146 ± 29 4.35 ± 0.8 6.7 ± 1.3 EM-line 2 Removal efficiencies of organic substrate: 70% REF-line and 73% EM-line
Laboratory scale trials Excess sludge production : reduction of 34%
Laboratory scale trials Important to underline: � This trial was the better one obtained � All trials conducted in different operating conditions shown an improvement in the reduction of excess sludge production with EM treatment from 0 to 34% It can be explained: � Difficulty to work in a 20L scale pilot (to maintain some parameters constant, development of filamentous bacteria, etc.) � Duration of trials (30 to 60 days) � Modification in EM parameters (frequencies, intensity, nature of signal, kind and shape of antenna, etc.)
Full-scale installation Wastewater treatment plant of Penthaz (near Lausanne), Switzerland
Full-scale installation
Full-scale installation Electromagnetic device: Electronic command: •2 frequencies (50 Hz to 20 kHz) •Tension (< 100 V) •Electromagnetic induction: few pico to few nanoTeslas P < 6,5 kJ.m -3 treated • Antenna: •5 rectangular shape antennas (1m x 2,3 m)
Full-scale installation
Full-scale results Operating conditions: � The total solids in the aeration tanks and the hydraulic and organic loading rates were maintained at identical levels in the two lines by extracting excess sludge. COD in COD in TS in Flow rate of TS in excess influent: effluent: aeration influent: Q 0 sludge: X E tCOD 0 tCOD L tank: X (m 3 d -1 ) (gTS L -1 ) (mgO 2 l –1 ) (mgO 2 l –1 ) (gTS L -1 ) REF- 17.9 ± 3.6 1.6 ± 0.4 3.0 ± 0.7 680 line 370 19.7 ± 4.2 1.3 ± 0.3 2.8 ± 0.7 EM-line 660
Full-scale results Operating conditions: Volumetric Specific Excess Apparent loading rate loading rate sludge sludge (kgCOD m -3 d -1 ) (kgCOD kg -1 TS d -1 ) production retention time (kgTS d -1 ) (d) REF-line 0.66 106 3.5 1.05 EM-line 0.81 48 6.4
Full-scale results Removal efficiencies of organic substrate: about 94-95% 400 100 80 COD effluent (mg/l) 300 COD influent (mg/L) 60 200 REF EM 40 100 20 0 0 0 7 14 21 28 35 42 49 56 Time (day)
Full-scale results Excess sludge production: reduction of 55% Cumulative slude production 1200 REF-line 1000 EM-line (kg TS) 800 600 400 200 0 0 5 10 15 20 25 30 35 Time (day)
Full-scale results Switching off the treatment: August September 8000 Cumulative excess sludge production (kg REF 6000 4000 TS) EM 2000 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 Time (day)
Full-scale results Switching off the treatment: 250 August Dayly excess sludge production (kg TS/d) September 200 150 EM x3 100 50 REF 0 0 5 10 15 20 25 30 35 40 45 50 55 60 Time (day)
Full-scale results � Biological sludge activity : A biomass stress index (BSI) was defined (ratio ATP extra-cellular over total ATP). This index was similar in the two lines and lower than 0.5 not showing any negative effects on biomass due to electromagnetic treatment. � N and P balance Ntotal N-NH 4 + N-NO 2 - N-NO 3 - Ptotal P-PO 4 3- Sample mg · L -1 mg · L -1 mg · L -1 mg · L -1 mg · L -1 mg · L -1 Influent 36 54 0.9 24 3.0 2.6 Effluent REF-line 46 62 0.3 23 1.9 1.4 Effluent EM-line 28 45 0.1 13 1.0 0.6 Excess sludge REF-line 41 53 0.3 12 1.1 0.6 Excess sludge EM-line 33 43 0.2 13 1.0 1.0
Perspectives � PhD study with University of Savoie - LOCIE (FR) and University of Grenoble – G2Elab (FR) - Influence on the proteinic synthesis - Cellular stress and physiological stress - Influence on the transfers of electrons - Measurement and modelling of EMF � New trials in the wastewater treatment plant of Penthaz
Perspectives New trials in the wastewater treatment plant of Penthaz
Conclusion � Very significant reduction in excess sludge production � Fast return on investment with gains in next steps (dehydration, stocking, transportation, incineration) � Operational costs very weak (only few Watts necessary) � No danger (people or installations) � No disadvantages comparing to other processes (chemical, biochemical, mechanical treatments) � It’s still necessary to go ahead with this technology but the potential regarding the influence on biological behaviour is very interesting in a friendly environmental and economical ways
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