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Sludge 2008 Angers, October 23, 2008
SLUDGE 2008SOUND SLUDGE PROJECT
(LIFE05 ENV/F/000067)
Project outline and outcomes
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Sludge 2008 Angers, October 23, 2008
Outline of the presentation• Sound Sludge project
• Waste Water Treatment Plant (WWTP) of Saint Sylvain d’Anjou and US unit
• Sampling scheme
• Effects of the US treatment on– sludge properties
– sludge production
– other environmental parameters
• Generalisation of the results
• Economical evaluation
• Conclusion – global evaluation
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Sludge 2008 Angers, October 23, 2008
Sound Sludge UPGRADING OF WASTEWATER TREATMENT PLANTS WITH ULTRASOUND
TREATMENT FOR REDUCING THE PRODUCTION OF SLUDGE
Strong increase in sludge production (5.5 Mt (1992) → 9 Mt (2005))Why ?
How ? Treating a part of the return sludge by ultrasound
Objectives / Evaluation criteria
Sludge reduction
No transfer of environmental pressure
Economical feasible
Technical feasible
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Sludge 2008 Angers, October 23, 2008
Demonstration site :WWTP of Saint Sylvain d’Anjou (6300 p.e.)
nutrient removal activated sludge process
final sedimentation
outletreturn-sludgeintermittent flow 18.6 m3/h
Aerobic partAnoxic part
inflow
surplus sludge
nitrogen removal dephosphation (injection FeCl3)
dehydration (mixing with a polyelectrolyte + thickening table)
Agricultural land
return sludge part stream constant flow 2 m3/h
disintegratedpartial flow
ultrasoundplant (6kW)
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Sludge 2008 Angers, October 23, 2008
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Sludge 2008 Angers, October 23, 2008
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Sludge 2008 Angers, October 23, 2008
Monitoring
- Water treatment performance - Implementation process- Maintenance
Technical feasible
- Energy consumption- Consumption chemicals - Maintenance costs
Economical feasible
- Sludge quality- Quality outlet WWTP- Emission greenhouse gases
No transfer of environmental pressure
- Sludge productionSludge reduction
MonitoringObjective / Evaluation criteria
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Sludge 2008 Angers, October 23, 2008
Measuring sludge production
thickening table
sludge pit
US
Overestimation (when table not working, extracted sludge returns to the WWTP)
Flow rate measurements + mean sample
Flow rate measurement + mean sample
Questionable representativity of mean sample
Flow rate measurement + mean sample
Buffer tank 1m3
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Sludge 2008 Angers, October 23, 2008
Effect of US on sludge production –calculation basics (I)
Measured & recorded data in trial period
Consistency monitoring(Stable Conditions?)
„Measured sludge production“
Mass balance incl. plausibility control
„Theoretical sludge production“1.CIRSEE-Model (France)2.ATV A131-Model (Germany)
INPUT
Match? => o.k.
Indicator for: measurements probably o.k.
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Sludge 2008 Angers, October 23, 2008
Effect of US on sludge production–calculation basics (II)INPUT for Models process parameters
:
x
Standard calculation equation : Plausibility control:Sludge productionweek x = SMafter extraction week X + extracted sludge week X – SM after extraction week X-1
Mass flow TSAS
SSbefore extraction Sludge mass SM before extraction
Sludge mass SM after extraction=
INLETm³/d, COD, SS
FeCl3
anox
RAS
Vaeration
Aeration (stirred) clarifier
SSafter extraction
Thickened sludge (kg) ≈ SMbefore extraction week X - – SM after extraction week X
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Sludge 2008 Angers, October 23, 2008
Sludge production – model input (inlet parameters)
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Sludge 2008 Angers, October 23, 2008
Sludge production – results
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Sludge 2008 Angers, October 23, 2008
Sludge production – results
Effective sludge reduction => 28 %
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Sludge 2008 Angers, October 23, 2008
Sludge production – an attempt to generalize (I)
• Target:– to estimate sludge reduction at WWTP Saint Sylvain at other flow rates of US device
• Approach:– if disintegration effects on sludge are 0, reduction effect must be also 0,– if treated sludge mass relative to total sludge mass falls below under a critical limit,
reduction effect must be near 0,– flow rate of US device and disintegration performance are converse proportional
• Solution:– extension of Model equation (ATV A 131) with „disintegration term“,– Using correlations between flow rate of US device and disintegration performance
Suggestion for „US-Disintegration - term“
CF…conversion factor
aUS-Dis. = a * 1- CF * Vbassin, total
VUS* SRT
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Sludge 2008 Angers, October 23, 2008
Sludge production – an attempt to generalize (II)
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Effects of US on sludge quality
Directive 86/278/EEC Max concentration measured
Cu 1000 – 1750 276
Cd 20 – 40 0.9
Zn 2500 – 4000 383
Cr 21
Hg 16 – 25 9
Ni 300 – 400 16
Pb 750 - 1200 19
• Actual legislation (conc in mg/kg DM)
• Sludge quality OK for agricultural spreading• US : no significant impact on sludge quality
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• Working document on sludge (conc in mg/kg DM)Effects of US on sludge quality
Directive 86/278/EEC Max concentration measured
AOX 500 310LAS 2600 < DL
DEPH 100 < DLNPE 50 < DLPAH 6 0.1PCB 0.8 < DL
PCDD/F 100 (ngTE/kg) 4.1
• Sludge quality OK for agricultural spreading• US : no significant impact on sludge quality
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Effects of US on sludge quality
• Fertilising agents– NTK– Phosphorus
No effects of US on concentration and thus agronomical sludge value
• Hygienisation– Salmonella spp < 3/g– Entérovirus < 2/10 g DM– Helminth eggs absent in 1.5 g
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Sludge 2008 Angers, October 23, 2008
Effect of US on Greenhouse Gas emissions
US treatment :– increase of CO2 from the aeration basin? – no impact on emission of total equivalents CO2 per m3
treated or per g COD removed
AirAnalyserGas-chromatographieCatarometric detectorCO2, N2O, CH4
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Sludge 2008 Angers, October 23, 2008
Effect of US on water treatment performance
• During periods of 1 week, sampling and analyzing water taken at the inlet and the outlet of the water treatment plant
• Parameters analyzed for :- VDS - Nitrogen (total, NO2 and NO3)- COD - AOX
- Hard COD - LAS- BOD5 - DEPH- Suspended solids - NPE- Phosphorus (total and PO4) - PAH
• Only treatment performance of phosphorus was lower during US treatment– 95 % P removed without US, 86 % P removed with US– Maximum concentration discharged 1,15 mg/l Ptot
– No change in FeCl3 injection during US trial
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Sludge 2008 Angers, October 23, 2008
Potential scope for use according to sludge handling costs (I)
• US application is not cost effective in the Saint Sylvain case
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Sludge 2008 Angers, October 23, 2008
Potential scope for use according to sludge handling costs (II)
• Cost comparison in case of higher disposal costs and in case of larger plant
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Sludge 2008 Angers, October 23, 2008
Potential scope for use according to sludge handling costs (III)
• Break-even points disposal costs (€ per ton DM) related to WWTP size
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Sludge 2008 Angers, October 23, 2008
Global evaluation (I) – The Process
• The US treatment of the return activated sludge can reduce sludge production significantly.
• No negative direct impact on the environment (outlet WWTP, direct greenhouse gas emission, sludge quality) observed, except for phosphorus.
• The CO2 balance is positive (higher CO2 emission during US) because of the high energy demand of the US treatment.
• No higher demand for waste water and sludge treatment chemicals (FeCl3, polymers) was found.
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Sludge 2008 Angers, October 23, 2008
Global evaluation (II) – The equipment• Ultrasound device was easy to integrate into
WWTP process line.
• Used ultrasound equipment showed stable 24h/7d operation and performance.
• During 264 days of operation no maintenance was required (only operation control).
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Sludge 2008 Angers, October 23, 2008
Global evaluation (III) – Economics• In the examined case (WWTP 6,300 p.e.) with low
sludge handling costs technology was not economically feasible.
• Rough scale up of results to a plant capacity of 100,000 p.e. (no digestion) showed economic efficiency.
• Break-even-point of sludge disposal costs for the used technology was estimated at about 55 €/ton dry sludge.
• Using ultrasound disintegration prior to digestion is more likely to be cost-efficient, even for small WWTP or at lower sludge disposal costs, respectively.