Sludge 2008 Angers, October 23, 2008
SLUDGE 2008SOUND SLUDGE PROJECT
(LIFE05 ENV/F/000067)
Project outline and outcomes
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
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
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)
Sludge 2008 Angers, October 23, 2008
Sludge 2008 Angers, October 23, 2008
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
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
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.
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
Sludge 2008 Angers, October 23, 2008
Sludge production – model input (inlet parameters)
Sludge 2008 Angers, October 23, 2008
Sludge production – results
Sludge 2008 Angers, October 23, 2008
Sludge production – results
Effective sludge reduction => 28 %
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
Sludge 2008 Angers, October 23, 2008
Sludge production – an attempt to generalize (II)
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
• 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
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
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
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
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
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
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
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.
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).
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.