LCA and nutrient removal - EU Project Neptune

0 downloads 0 Views 641KB Size Report
Plant 2: 100.000 PE, online control of length of the aerated phase in place. Influent. Sand trap. Anaerobic tanks. Aeration tank. Aeration tank. Clarifiers. Effluent.

LCA and nutrient removal

Joris Roels, Tom Wambecq, Kris De Gussem, Alessio Fenu, Aquafin, Belgium Xavier Flores-Alsina, Peter Vanrolleghem ModelEAU, Canada

Introduction

• Online control for nutrient removal is standard practice at Aquafin (AQF) (Flanders) • Goal of online control at Aquafin = meeting the effluent consent at the lowest cost • Currently AQF has no stimulus to produce a cleaner effluent than strictly necessary since AQF doesn’t pay a levy for the residual pollution • A new methodology was assessed which sets as goal a reduction of the the footprint of wastewater treatment following a life cycle approach • For this purpose, calibrated, asm2d models were made of 3 full scale WWTP’s on which the two methodologies (costs respecting effluent consent versus lowest footprint) were compared

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

2

Outline of the 3 plants

• Plant 1: 27.000 PE, limited online control already in place

O2

Influent

Sand trap

Intermittent Aeration

Aeration tank

O2

NO3

Clarifiers

Dsand enitrifying filters

NO3

Sludge dewatering

Effluent

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

3

Outline of the 3 plants • Plant 2: 100.000 PE, online control of length of the aerated phase in place

NO3

Influent

Sand trap

Aeration tank

O2

Clarifiers

Anaerobic tanks Aeration tank O2

Effluent

Sludge dewatering Stormwater tanks

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

4

Outline of the 3 plants • Plant 3: 270.000 PE, state of the art of online control at AQF

NO3 NH4

Aeration tank

O2

O2 Aeration tank Influent

Sand trap

Anaerobic tanks

O2 Aeration tank

PO4

O2 Aeration tank

Clarifiers

Effluent

Sludge dewatering Stormwater tanks

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

5

Calibration Concentration of ammonium (mg/L)

Ammonium effluent 5 4 3 2 1 0

0

50

100

150

200

250

300

day

350

Nitrate effluent

Concentration of nitrate (mg/L)

10

8

6

4

2

0

0

50

100

150

200

250

300

350

day

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

6

Calibration Power usage (Reality: 1680118 KwH) (model total: 1659549 KwH) other: 3.9% not modelled: 1.2% nitrate retour: 1.8% mixers: 2.7% heating: 5.4%

recirculation: 6.9% aeration: 39.1%

influent: 6.9%

dynasand: 10.4%

sludge line: 21.7%

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

7

Comparison of optimisation strategies Meeting effluent consent at lowest cost = straigthforward Reducing footprint of WWTP’s • Impact is expressed as mPET: milli people equivalents targeted. 1 PE represents the environmental impact of 1 hypothetical person in a defined country and year. • Impact is composed of a number of impact categories such as global warming, eutrophication, acidification, ozone depletion, ecotoxicity, human toxicity, …. E.g. the EDIP97 methodology normalises the global warming impact of 1 PE to 8700 kg CO2-equivalents per year. • Data from Henrik Fred Larsen: Parameter Nitrogen Phosphorus Electricity consumption Sludge production Infrastructure FeCl3 40% dosing Sodium acetate dosing

Impact 37,23 mPET / kg N 269,2 mPET / kg P 0,12324 mPET / kWh 0,1 mPET / kg 37% DM sludge 0,127 mPET / m³ influent treated 2,611 mPET / kg 0,7781 mPET / kg NaOAc

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

8

Impact reduction of wastewater treatment • Waste water treatment plants are lowering the ecological footprint (as expected..) LCA 8000 Kjeldahl Nitrogen Nitrate Phosphate Energy Sludge Infrastructure Chemical dosing

7000

LCA (in PET)

6000 5000 4000 3000 2000 1000 0

NoBefore WWTP

After WWTP

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

9

Optimisation scenario’s • • • • •

Migration from manual to online control by installing extra online sensors Changing setpoints of existing controllers (NH4, SRT, O2, …) Alternative (rule based) control algorithms Changing position of existing sensors Increasing internal recycle pumping capacity

• For each plant roughly 2000 simulations were run

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

10

Results / Conclusions Plant 1 Plant 2 Plant 3

Cost optimisation

Footprint optimisation

Costs*

-15 %

-10 %

Footprint

-3%

-7%

Costs*

-2%

0%

Footprint

- 13 %

- 22 %

Costs*

-7%

-2%

Footprint

-7%

- 11 %

* Sum of operational cost for electricity consumption, sludge disposal and chemical dosing

• • •

Cost optimisation leads to a cost reduction of 2 – 15 % and an impact reduction of 3 – 13 % Footprint optimisation leads to a cost reduction of 0 – 10 % and an impact reduction of 7 – 22 % Footprint optimisation leads to a cleaner effluent than the legally imposed quality, favours bio-P over chemical P removal and results into less NH4 in the effluent

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

11

Conclusions

• • • • •



A reduction of footprint with 1 % leads to an increase of operational costs with 1 % Standardisation of footprint calculation is necessary (!) Optimisation towards footprint is very compatible with the way operators tend to manually control the plants Online control reduces operational costs and increases treatment efficiency A plant that is already (partly) controlled online can perform even better if the correct controller settings are applied. These correct settings vary from plant to plant even when layouts are similar since every plant has its own characteristic influent composition. Custom made controllers are necessary to achieve the best performance

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

12

Acknowledgment

• This study was part of the EU Neptune project (Contract No 036845, SUSTDEV-2005-3.II.3.2), which was financially supported by grants obtained from the EU Commission within the Energy, Global Change and Ecosystems Program of the Sixth Framework (FP6-2005-Global-4)

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

13

Work package 4 LCA and ICA Lluís Corominas, Xavier Flores-Alsina, Peter Vanrolleghem

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

Case study Neptune Simulation Benchmark • A2O plant sized using the Metcalf & Eddy design guidelines • The influent profile have been generated using phenomenological models including daily, weekly and seasonal variation (low C/N ratio) • The EAWAG ASM3 bio P and the double exponential velocity function of Takács are the main process models

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

Case study Evaluation of control strategies • Different combinations of controllers tested using the Neptune Benchmark • Comparison of strategies with and without chemical addition • Is the implementation of control reducing environmental impact? • Are the controllers based on the addition of chemicals the right solution to reduce environmental impact? (evaluation using LCA) DO controller

NO3- controller (Qintr_recycle)

NO3- controller (Qcarbon)

Chemical addition

PO43- controller (Qmetal)

OUR controller

NH4+ controller

OUR controller

NH4+ controller

OUR controller

NH4+ controller

TSS controller

TSS Vstorage controller controller

TSS controller

TSS controller

TSS controller

TSS controller

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

Results: dynamic profiles 7

5

Nitrate control (carbon addition)

A1 A3

12 10

NO3- (gN·m-3)

DO (g (-COD)·m-3)

6

14

DO control

A1 A2

4 3

8 6

2

4

1

2

0 240

0 240

242

244

246

248

250

252

254

256

258

260

242

244

246

A1 A9

14

Ammonia control (cascade)

A1 A7

250

252

254

256

258

260

258

260

time (days)

time (days)

8

248

12

Phosphate control (metal addition)

PO43- (g·m-3)

NH4+ (gN·m-3)

6

4

10 8 6 4

2

2

0 240

242

244

246

248

250

252

time (days)

254

256

258

260

0 240

242

244

246

248

250

252

254

time (days)

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2 A1: NO CONTROL

256

Results: LCA evaluation DO, NH4+, NO3- (internal recycle) and TSS control

No Control A1 (No controller) 4.00 3.50 3.00

mPET*year/m3

2.50 2.00 1.50 1.00 0.50 0.00 Induced impacts Energy

Infrastructure

Avoided impacts Sludge

Chemicals

Total nutrients

DO + NH4+ + TSS + NO3- and PO43- controlled by adding external carbon source

DO + NH4+ + TSS + PO43- controlled by metal addition

Avoided impact: Influent – effluent nutrient impact Induced impact: Effluent nutrient + Electricity + Sludge + Infr + chemicals

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

18

Conclusions • The implementation of control leads to an increase of the avoided impact and a decrease in the induced impact • The most environmentally friendly strategies are the ones that include metal and carbon addition as they induce a significant reduction of nitrate and phosphorus in the effluent • LCA gives better results for strategies that improve nutrient removal vs those that reduce energy consumption

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

19

Acknowledgements This research is supported by the Canada Research Chair in Water Quality Modeling and a NSERC Special Research Opportunities grant as part of the Canadian contribution to the European Union 6th framework project NEPTUNE. This study was part of the EU Neptune project (Contract No 036845, SUSTDEV-2005-3.II.3.2), which is financially supported by grants obtained from the EU Commission within the Energy, Global Change and Ecosystems Program (FP6-2005-Global-4).

Canada Research Chair in Water Quality Modeling

Neptune project, contract no 036845, FP6-2005-Global-4, SUSTDEV-2005-3.II.3.2

20