sludge 2008 - angers loire métropole · sludge 2008 angers, october 23, 2008. effect of us on...

Sludge 2008 Angers, October 23, 2008

SLUDGE 2008SOUND SLUDGE PROJECT

(LIFE05 ENV/F/000067)

Project outline and outcomes


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


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


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)


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


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


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.


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 production – model input (inlet parameters)


Sludge production – results


Sludge production – results

Effective sludge reduction => 28 %


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 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


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


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


Potential scope for use according to sludge handling costs (I)

• US application is not cost effective in the Saint Sylvain case


Potential scope for use according to sludge handling costs (II)

• Cost comparison in case of higher disposal costs and in case of larger plant


Potential scope for use according to sludge handling costs (III)

• Break-even points disposal costs (€ per ton DM) related to WWTP size


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.


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).


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.

sludge 2008 - angers loire métropole · sludge 2008 angers, october 23, 2008. effect of us on...

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