The Effect of pH on Wastewater Biosolids Electrodewatering...The Effect of pH on Wastewater...
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The Effect of pH on Wastewater Biosolids Electrodewatering Environmental Engineering, Department of Civil Engineering and Applied Mechanics, McGill University Keegan Balcom, Tala Navab-Daneshmand, Dominic Frigon The ED Unit The anode vertically compresses the sludge cake placed on a perforated cathode over a filter media (Fig. 4). Evaluating the sludge pH effect on electrodewatering (ED) efficiency and effectiveness by adding acid and base. Motivation • 10 million dry tons of biosolids (residues produced by wastewater treatment) were produced in 2007 in North America (3). Corresponding to aligning full semi trucks across Canada 3 times. • Transport and disposal cost can account for up to 60% of the overall plant operation costs (1). Fig 2. Electro-osmosis (solids > 10%) (2) Fig 3. Electrolysis & Electro-migration (2) Fig 1. Full-scale Cinetik TM dewater- ing unit (reproduced from Ovivo 2010) Fig 4. Lab-scale dewatering unit • The interaction of electro-osmosis (Fig. 2) electro-migration of ions (Fig. 3) with biosolids and pH (with added acidity or alkalinity) is being investigated. The electrical current and sludge resistivity lead to an increase in temperature defined as Joule heating. This high temperature inactivates bacterial pathogens such that ED biosolids can be land applied as soil fertilizers or conditioners. The ED Technology • The Cinetik TM , developed by OVIVO, is based on electro- osmotic principles (Fig. 1). • An electrical field is applied with a pressure to increase dryness from 15% to 30- 50% (Fig.2). • This technology uses less than 30% of the energy required by a heat dryer to reach the same dryness. Electro-kinetic Phenomena ED with added Acid/Base • Different concentrations of acid and base were added to sludge samples prior to ED. • Biosolids pH and dryness of the samples were measured before and after each ED experiement. pH Titration The change in sludge pH was evaluated with the addition of H + or OH - . • 0.5 M HCl was added in increments of1ml up to 30ml with an adjustment time of 30 minutes before measurement. • 0.5 M NaOH was added in increments of 5ml up to 30ml with an adjustment time of four hours before measurement. y = -0.1864x + 2.3899 R² = 0.9848 y = -0.778x + 5.3277 R² = 0.9309 y = 0.182x - 0.0197 R² = 0.9103 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 2 4 6 8 10 12 14 log [OH-] added (mmol/g-TS) log [H+] added (mmol/g-TS) pH HCl added HCl added NaOH added Fig 5. pH titration results Increase Total Solids The increase in sludge dryness after ED varied significantly with sludge pH. Extreme pH resulted in reduced dewatering efficiency compared to moderate (5-9) pH. 0 2 4 6 8 10 12 14 276 160 69 0 128 360 pH avg pH before avg pH after Eq. H + added (mmol/g - TS) Eq. OH - added (mmol/g - TS) Control Fig 6. pH before and after ED (n=2) 0 5 10 15 20 25 30 35 40 45 276 160 69 0 128 360 Total Solids (%) Eq. H + added (mmol/g - TS) Eq. OH - added (mmol/g - TS) Control Fig 7. Dryness before and after ED (n=2) Extreme pH conditions, less than 5 or greater than 9, reduced biosolids dewatering efficiency in ED in terms of final dryness. pH Change Average pH in sludge samples dropped 1-2 pH units independently of initial sludge pH (except for base1). Contain the sludge during ED using a nylon mesh to ensure volume of ED sludge is constant. 1. Liu, S., Zhu, N. and Li, L.Y. (2011) The one-stage autothermal thermophilic aerobic digestion for sewage sludge treatment. Chem Eng J 174(2-3), 564- 570. 2. Mahmoud, A., Olivier, J., Vaxelaire, J. and Hoadley, A. F. A., Water Research, 2010 3. Singh, A., Mosher, F., Lugowski, A., Ward, O., Walsh, C., 2007. Lystek Biosolids Proces- sing Technology and Beneficial Applications of the Processed Biosolids — Full Scale Results. WEAO Technical Conference, London Ontario. . OBJECTIVE METHODS INTRODUCTION CONCLUSION RESULTS AND DISCUSSION FUTURE WORK Table 1. Settings Intensity 6.5 A Voltage 60 V Pressure 1.4 bar Duration 10 mins REFERENCES pH Titration Results • Addition of H + over pH showed two distinct buffereing curves (Fig. 5). • Addition of OH - over pH followed a single linear curve (Fig. 5).
Transcript of The Effect of pH on Wastewater Biosolids Electrodewatering...The Effect of pH on Wastewater...
The Effect of pH on Wastewater Biosolids ElectrodewateringEnvironmental Engineering, Department of Civil Engineering and Applied Mechanics, McGill University
Keegan Balcom, Tala Navab-Daneshmand, Dominic Frigon
The ED UnitThe anode vertically compresses the sludge cake placed on a perforated cathode over a filter media (Fig. 4).
Evaluating the sludge pH effect on electrodewatering (ED) efficiency and effectiveness by adding acid and base.
Motivation• 10 million dry tons of biosolids (residues produced by
wastewater treatment) were produced in 2007 in North America (3). Corresponding to aligning full semi trucks across Canada 3 times.
• Transport and disposal cost can account for up to 60% of the overall plant operation costs (1).
Fig 2. Electro-osmosis (solids > 10%) (2) Fig 3. Electrolysis & Electro-migration (2)
Fig 1. Full-scale CinetikTM dewater-ing unit (reproduced from Ovivo
2010)
Fig 4. Lab-scale dewatering unit
• The interaction of electro-osmosis (Fig. 2) electro-migration of ions (Fig. 3) with biosolids and pH (with added acidity or alkalinity) is being investigated.
The electrical current and sludge resistivity lead to an increase in temperature defined as Joule heating. This high temperature inactivates bacterial pathogens such that ED biosolids can be land applied as soil fertilizers or conditioners.
The ED Technology• The CinetikTM, developed by
OVIVO, is based on electro-osmotic principles (Fig. 1).
• An electrical field is applied with a pressure to increase dryness from 15% to 30-50% (Fig.2).
• This technology uses less than 30% of the energy required by a heat dryer to reach the same dryness.
Electro-kinetic Phenomena
ED with added Acid/Base • Different concentrations of acid
and base were added to sludge samples prior to ED.
• Biosolids pH and dryness of the samples were measured before and after each ED experiement.
pH TitrationThe change in sludge pH was evaluated with the addition of H+ or OH-.• 0.5 M HCl was added in
increments of1ml up to 30ml with an adjustment time of 30 minutes before measurement.
• 0.5 M NaOH was added in increments of 5ml up to 30ml with an adjustment time of four hours before measurement.
y = -0.1864x + 2.3899R² = 0.9848
y = -0.778x + 5.3277R² = 0.9309
y = 0.182x - 0.0197R² = 0.9103
0.0
0.5
1.0
1.5
2.0
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3.0
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log
[OH-
] add
ed(m
mol
/g-T
S)
log
[H+]
add
ed(m
mol
/g-T
S)
pH
HCl addedHCl addedNaOH added
Fig 5. pH titration results
Increase Total SolidsThe increase in sludge dryness after ED varied significantly with sludge pH. Extreme pH resulted in reduced dewatering efficiency compared to moderate (5-9) pH.
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276 160 69 0 128 360
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avg pH before
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Eq. H+ added(mmol/g - TS)
Eq. OH- added (mmol/g - TS)
Control
Fig 6. pH before and after ED (n=2)
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276 160 69 0 128 360
Tota
l Sol
ids
(%)
Eq. H+ added(mmol/g - TS)
Eq. OH- added (mmol/g - TS)
Control
Fig 7. Dryness before and after ED (n=2)
Extreme pH conditions, less than 5 or greater than 9, reduced biosolids dewatering efficiency in ED in terms of final dryness.
pH ChangeAverage pH in sludge samples dropped 1-2 pH units independently of initial sludge pH (except for base1).
Contain the sludge during ED using a nylon mesh to ensure volume of ED sludge is constant.
1. Liu, S., Zhu, N. and Li, L.Y. (2011) The one-stage autothermal thermophilic aerobic digestion for sewage sludge treatment. Chem Eng J 174(2-3), 564-570.
2. Mahmoud, A., Olivier, J., Vaxelaire, J. and Hoadley, A. F. A., Water Research, 2010
3. Singh, A., Mosher, F., Lugowski, A., Ward, O., Walsh, C., 2007. Lystek Biosolids Proces- sing Technology and Beneficial Applications of the Processed Biosolids — Full Scale Results. WEAO Technical Conference, London Ontario. .
OBJECTIVE METHODS
INTRODUCTION
CONCLUSION
RESULTS AND DISCUSSION
FUTURE WORK
Table 1. Settings
Intensity 6.5 A
Voltage 60 V
Pressure 1.4 bar
Duration 10 mins
REFERENCES
pH Titration Results
• Addition of H+ over pH showed two distinct buffereing curves (Fig. 5).
• Addition of OH- over pH followed a single linear curve (Fig. 5).
