Thermal Energy Recovery from Drinking Water

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Delft University of Technology

Thermal Energy Recovery from Drinking Water

van der Hoek, Jan Peter; Mol, S; Ahmad, Jawairia Imtiaz; Liu, Gang; Medema, Gertjan

DOI

10.18690/978-961 -286-061-5.3

Publication date

2017

Document Version

Final published version

Published in

Proceedings of the 10th International Conference on Sustainable Energy and Environmental Protection

Citation (APA)

van der Hoek, J. P., Mol, S., Ahmad, J. I., Liu, G., & Medema, G. (2017). Thermal Energy Recovery from

Drinking Water. In J. Krope, A. Ghani Olabi, D. Goricanec, & S. Bozicnik (Eds.), Proceedings of the 10th

International Conference on Sustainable Energy and Environmental Protection: JUNE 27 - 30, 2017, Bled

University of Maribor Press. https://doi.org/10.18690/978-961 -286-061-5.3

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10'''" INTERNATIONAL CONFERENCE ON SUSTAINABLE ENERGY A N D ENVIRONMENTAL PROTECTION (JUNE 27™ - 30™, 2017, B L E D ,

SLOVENIA), RENEWABLE ENERGY SOURCES un^^^i^i^ZTress

J. Krope, A.Ghani Olabi, D. Goricanec & S. Bozicnik

Thermal Energy Recovery from Drinking Water

J A N P E T E R V A N D E R H O E K , S T E F A N M O L , J A W A J R I A I M T I A Z A H M A D , G A N G L I U & G E R T J A N M E D E M A

Abstract Waternet, the water utility o f Amsterdam and surroundings, has the ambition to operate clitiiate neutrally in 2020. A l t h o u g h large progress has been made since 1990 to reduce Greenliouse Gas emissions ( G H G ) , i n 2016 the remaining emission was still 37,203 ton C 0 2 - e q . A possibility to further decrease the G H G emission is thermal energy recovery fi'om drinking water. A s Waternet produces drinking water fi-om surface water, the temperature varies between 1 oC and 25 oC w h i c h offers opportunities. The question is whether thermal energy recovery from drinking water really results i n a reduction in G H G emissions, and especially at what costs. I n addition, thermal energy recovery influences the d r i n k i n g water temperature and thus may affect the microbiological drinking water quality. A specific case i n Amsterdam showed that c o l d recovery fi'om drinking water contributes to the reduction o f G H G emissions, and reduces the costs o f coolmg. Preliminary laboratoiy experiments revealed no negative effects on the microbiological drinking water quality.

Keywords: • cold recovery • Greenhouse Gas emissions • d r i n k i n g water • microbiological water quality • thermal energy •

CORRESPONDENCE ADDRESS: Jan Peter van der Hoek, Ph.D., Professor, Delft University o f Technology, Department of Water Management, Stevinweg 1, 2628 CN Delft, The Netherlands, e¬ mail: j.p.vanderhoek@tudelft.nl. Stefan M o l , M.Sc, Researcher, Waternet, Depaitment o f Research & Advice, Korte Ouderkerkerdijk 7, 1096 AC Amsterdam, The Netherlands, e-mail: stefan.mol@waternet.nl. Jawairia Imtiaz Ahmad, M.Sc, Ph.D. Candidate, Delft University o f Technology, Department of Water Management, Stevinweg 1, 2628 CN Delft, The Netherlands, e¬ mail: j.i.ahmad@tudelft.nl. Gang Liu, Ph.D., Associate Professor, Delft University ofTechnology, Depaitment of Water Management, Stevinweg I , 2628 CN Delft, The Netherlands, e-mail: g.Iiu-l@tudelft.nl. Gertjan Medema, Ph.D., Professor, Delft University ofTechnology, Department of Water Manageinent, Stevinweg I , 2628 CN Delft, The Netherlands, e-mail: g.medema@tudelft.nl. https://d0i.0rg/l 0.18690/978-961 -286-061-5.3 I S B N 978-961 -286-061-5

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J. Peter van der Hoek, S. Mol, J. Imtiaz Ahmad, G . Liu & G . Medeina: Thermal Energy Recovery from Drinking Water

1 Introduction

Waternet is the public water u t i l i t y o f Amsterdam and surroundings. "Waternet has the ambition to operate climate neutrally i n 2 0 2 0 . A climate neutral operation is defined as an operation without a net greenhouse gas ( G H G ) emission. F r o m 1 9 9 0 to 2 0 1 6 the G H G emission o f Waternet decreased fi'om 1 1 4 , 1 9 6 ton C02-eq to 3 7 , 2 0 3 ton C02-eq, as shown i n Fiaure 1.

120000

1990 2007 2016 2020 year

Figure 1. Greenhouse gas emissions o f Waternet

Hence, additional measures have to be taken to realize the target in 2020. The policy o f Waternet, and also a condition f o r the measures, is to select measures w h i c h can be incorporated in the operations o f Waternet, and an inventory has been made recently [ 1 ] . A n additional condition is that measures have to be cost neutral. One o f the options concerns thermal energy recovery f r o m drinking Water. A s Waternet produces d r i n k i n g water fi-om surface water, w h i c h varies i n temperature between 1 "C and 25 "C [ 2 ] , cold recovei-y f o r cooling and heat recovery f o r heating, fi-om drinl^ing water ti-ansport pipes, looks attractive. I n case o f cold recovery, the d r m k i n g water temperature after c o l d recovery increases, w h i c h may affect the microbiological drinking water quality [ 3 ] .

The objective o f this study was to analyse the potential o f cold recoveiy fi-om d r i n k i n g water on thi-ee decisive criteria: the effect on the reduction o f G H G emission o f Waternet, the financial effects and the effects on microbiological drinking water quality.

2 Materials and Methods

G H G emissions were calculated based on the intemational Greenhouse Gas Protocol [ 4 ] . T o determine the effect o f G H G emissions on the climate footprint, the Intergovernmental Panel on Climate Change Global W a r m i n g Potential (IPCC G W P ) 100a method [5] was used. W i t h i n this method, only the environmental problem o f climate change is evaluated and the results are expressed i n CO2 equivalents.

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J, Peter van der Hoek, S. Mol, J. Imtiaz Ahmad, G. Liu & G. Medema: Thermal Energy Recovery from Drinking Water Costs o f cold recovery fi'om drinking water were based on the Total Costs o f Ownership ( T C O ) concept, i n w h i c h total costs o f acquisition and operating costs as w e l l as costs related to replacement at the end o f the life cycle are included. The evaluation period covered a period o f 30 years.

For the G H G analysis and the cost analysis a specific case was selected: the "Sanquin-W a t e r n e f case. Sanquin produces plasma products f r o m blood and needs cooling capacity to store products. Just along Sanquin a 700 m m drinking water m a i n o f Waternet passes. From this main a supply pipe and return pipe are connected w i t h a heat exchanger, as shown i n Fieure 2.

Figure 2. Delivery o f coolmg capacity, through a Waternet drinking water main, v i a a heat exchanger ( H E ) , to Sanquin

Through this connection Waternet can supply Sanquin coolmg capacity: during winter cooling capacity is delivered directly, and an aquifer thermal energy storage ( A T E S ) is charged. I n suminer the A T E S supplies the cooling capacity. Figure 3 shows the process set-up i n winter and summer.

W I N T E R

Ö

SUMMER

Figure 3. Process set-up o f cooling w i t h drinking water under winter and summer conditions

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J. Peter van der Hoek, S. Mol, J. Imtiaz Ahmad, G . Liu & G . Medema: Thermal Energy Recovery from Drinking Water

Effects on microbiological drinlting water quality and b i o f i l m f o r m a t i o n were studied in three laboratoiy scale drinking water distribution systems ( D W D S ) [ 6 ] . Figure 4 shows the systems: system 1 is the study system w i t h operational heat exchanger f o r cold recoveiy, system 2 is the control system w i t h installed but not in operation heat exchanger to study the effect o f additional surface area m the distribution system, while system 3 is the reference system without heat exchanger.

COM In

Hit ; : T « m | , « > l u r a r e f u l a l o r

, Syitem 1. ThMmal en«jv lecovery

_ System 2-No(..Dp«fitloiMl Vt T " ^ Heit ExchariBflr Cold In

F k w TempwiluiB BloWm ö m p l i r i ^ SeniM s.niiw coupon. T . p t o f w i W r j a m p l l n i

Figure 4 . Laboratoiy scale d r i n k i n g water distribution systems

Table 1 summarizes the operational conditions o f the three laboratory scale systems. The systems were operated f o r a period o f 6 months. As these preliminary laboratory experiments were carried out i n the suminer, the inlet d r u i k i n g water temperature was relatively high ( 1 8 - 1 9 °C) compared to the inlet drinking water temperature at w h i c h the fiill-scale installation at Sanquin w i l l be operated (temperatures below 1 5 °C).

Table 1 . Operational conditions o f the laboratoiy scale D W D S Laboratory scale D W D S 1 2 3 F l o w rate ( l / m ) 4 . 5 4 . 5 4 . 5 F l o w velocity (m/s) 0 . 1 5 0 . 1 5 0 . 1 5 Inlet temperature (°C) 1 9 1 8 1 9 Outlet temperature (°C) 2 4 1 8 1 9 Pipe material P V C PVC P V C Pipe diameter ( m m ) 2 5 2 5 2 5 Length o f system ( m ) 1 0 1 0 1 0

M i c r o b i o l o g i c a l water quality and b i o f i l m analysis concerned Total Cell Concentrations ( T C C ) , Adenosine T r i Phospate ( A T P ) concentrations, Aeromonas spp. and Legionella spp..

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3 Results and Discussion 3.1 Reduction of G H G emissions

The results w i t h respect to reduction o f G H G emissions in the Sanquin case are shown in Table 2. This table compares two situations: the use o f conventional cooling machines f o r cooling capacity, and the use o f drinking water f o r cooling capacity.

Table 2. Electricity use and G H G emission o f t w o systems f o r cooling in the "Sanquin-W a t e m e f ' case Electricity use (kWh/year) G H G emission (ton COi-eq/year) Traditional cooling machmes 2,000,000 1,220 C o o l m g w i t h drinking water 200,000 120

Table 2 shows that i n the case o f cooling with drinking water, the G H G emission can be reduced w i t h 1,100 ton C02-eq. The potential may be even higher when i t is a l l o w e d to heat up the drinking water after the heat exchange above 15 °C. U n t i l n o w the l u n i t has been set at 15 °C f o r safety reasons. Research i n the laboratoiy scale experiments have to reveal whether higher temperatures (without negative effects on microbiological water quality), and thus a higher G H G emission reduction, is feasible. I n Amsterdam additional locations have to be f o u n d where thermal energy supply and demand matches and additional project can be realized to mcrease the contribution o f thermal energy recovery in the target o f 37,203 ton C02-eq.

3.2 Costs

The results w i t h respect to the costs are summarized i n Table 3. Based on the T C O , the system using cooling w i t h d r i n k i n g water has a lower T C O than the system using traditional cooling machines. Specific aspects, characteristic f o r the "Sanquin-Wateinef' case, contribute to this. B y using cooling w i t h drinltmg water it is not necessary to extend the existing electricity infi-astructure, and noise reducing measures are not required. I n addition, ti-aditional cooling machines requu'e a footprint w h i c h is not available.

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Table 3. Total costs o f ownership o f t w o systems f o r cooling in the " S a n q u m - W a t e r n e f case

Total Costs o f Ownership ( m i l l i o n € ) Traditional cooling machines 8.0 C o o l i n g w i t h drinlcing water 5.4

3.3 Effect on microbiological drinking water quality and biofilm formation

Figure 5 shows the Total Cell Concentrations ( T T C ) and A T P concentrations in the bulk water phase i n the laboratoiy scale D W D S s . The results reveal similar microbiological water quality in both systems w i t h a heat exchanger (operational heat exchanger - system

1, and non-operational heat exchanger - system 2 ) , before and after the heat exchanger, and in the reference system (system 3 ) . This stable microbiological quality in the bulk water phase may be due to the short distance and retention time o f the water (about one minute), w h i c h is too short f o r significant changes to occur.

üATP BTCC 5,E+05

4,E+05 =•

0,E+00 BTER ATER BHE AHE REFI REF2

Figure 5. M i c r o b i o l o g i c a l water quality i n D W D S 1 ( B T E R : before thermal energy recovery; A T E R : after thermal energy recovery), D W D S 2 ( B H E : before heat exchanger; A H E : after heat exchanger) and D W D S 3 ( R E F I : at start o f D W D S ; REF 2:

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29 :i.oo (1) "cL E

I

B T E R A T E R B H E A H E R E F I R E F 2

Figure 6 . Positive Legionella spp. samples in bulk water i n D W D S 1 ( B T E R : before thermal energy recovery; A T E R : after thermal energy recoveiy), DWTDS 2 ( B H E : before heat exchanger; A H E : after heat exchanger) and D W D S 3 ( R E F I : at start o f

D W D S ; REF 2 : at end D W D S ) ( n = l 1)

2.000

BTER A T E R B H E A H E R E F I R E F 2

Figure 7 . Aeromonas spp. in bulk water in D W D S 1 ( B T E R : before thermal energy recoveiy; A T E R : after thermal energy recoveiy), D W D S 2 ( B H E : before heat exchanger; A H E : after heat exchanger) and D W D S 3 ( R E F I : at start o f D'WDS; R E F 2 :

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Regarding the selected micro-organisms, Legionella spp. and Aeromonas spp., the water quality was also stable i n the tlii'ee D W D S s , as shown i n Figures 6 and 7.

Figure 6 shows that Legionella was already present i n the incoining water and does not increase after passing the heat exchanger, neither i n the system w i t h the operational heat exchanger (system 1), nor i n the system w i t h the non-operational heat exchanger (system 2). Figure 7 shows comparable numbers f o r Aeromonas spp. i n all tliree systems, irrespective o f higher temperature after cold recovery.

In contrast, higher cell numbers and biological activity were detected i n b i o f i l m formed after cold recovery compared to the b i o f i l m before cold recovery (2.5 times higher T C C and A T P , Figure 8). The different results f o u n d f o r b u l k water and b i o f i l m phases is probably due to the b i g difference i n their exposure time to higher temperature (one minute for b u l k water and six months f o r b i o f i l m ) . The increased g r o w t h o f b i o f i l m after cold recovery may lead to a change in microbial community composition and structure. This preliminary research only lasted f o r a period o f six months. On the longer term a changed microbial community composition may affect the microbial water quality i n the bulk water phase.

ATP TCC

6

Biofitm Biofilm Biofilm Biofilm Biofilm Biofilm BTER ATER BHE AHE REFI REf2

Figure 8. B i o f i l m development in D W D S 1 ( B T E R : before thermal energy recovery; A T E R : after thermal energy recovery), D W D S 2 ( B H E : before heat exchanger; A H E : after heat exchanger), D W D S 3 (REF 1: at start o f D W D S ; R E F 2: at end D W D S ) and

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J. Peter van der Hoek, S. Mol, J. Imtiaz Ahmad, G. L i u & G. Medema: Thermal Energy Recovery from Drinking Water

4 Conclusions

Thermal energy recovery fi'om drinking water is applied at ftill scale and offers an alternative f o r the use o f fossil f u e l and thus contributes to the reduction o f G H G emissions. C o l d recoveiy, as applied in a specific case i n Amsterdam, showed to have a positive business case: compared to a traditional system w i t h cooling machines, T C O decreased fl'om € 8.0 m i n to € 5.4 m i n . Preliminary research at laboratoiy scale showed that the microbial d r i n k i n g water quality, measured by T C C , A T P , Legionella spp. and

Aeromonas spp., was not affected by cold recoveiy. However, b i o f i l m formation

increased after cold recoveiy and requires further research to reveal the potential role o f enlianced b i o f i l m g r o w t h on microbiological water quality.

Acknowledgements

The research was funded by water utility Waternet (Amsterdam, The Netherlands) and by Topsector Water T K I Water Technology Program of the Dutch Ministry of Economic Affairs, grant 20I5TUD003.

References

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Journal of Water and Climate Change, vol. 7(1), pp. 29-38, 2016.

[2] J.P. van der Hoek, "Towards a climate neutral water cycle". Journal of Waler and Climate

Change, vol. 3(3), pp. 163-170, 2012.

[3] D. van der Kooij and P.W. van der Wielen, "Microbial growth in drinking water supplies: problems, causes, control and research needs". Water Intelligence Online, vol. 12, 9781780400419, 2013.

[4j World Resource Institute (WRI) and World Business Council for Sustainable Development (WBCSD), The Greenhouse Gas Protocol: A corporate Accounting and Reporting

Standard, revised edition. Washington DC / Geneva: World Resource Institute / World

Business Council for Sustainable Development, 2004.

[5] S. Solomon, D. Qin, M . Manning, Z. Chen, M . Marquis, K.B. Averyt, M . Tignor and H.L. Miller (eds), Contribution of Working Group J to the Fourth Assessment Report of the

Intergovernmental Panel on Climate Change, Cambridge-UK and New York-USA:

Cambridge University Press, 2007.

[6] J.L Alimad, G. Liu, J.P. van der Hoek and G. Medema, "Assessment of microbiological water quality changes linked to Thermal Energy Recovery from Drinking Water Distribution System", abstract submitted to the Leading Edge Technology Conference on Water and Wastewater Technologies, 29 May 2 0 1 7 - 2 June 2017, Florianópolis, Brazil.

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