adaption of pellet reactor softening method into …caog na concentration[mg/l] ph naohdose[m]...

Dit vand – vores viden

ADAPTION OF PELLET REACTOR

SOFTENING METHOD INTO DANISH

WATERWORKS

CURRENT STATUS AND PERSPECTIVES

Krzysztof (Chris) KowalskiDanwatec

[email protected]: +45 61 43 73 51

Danwatec – potable water services

� New plants

� Renovation

� Aeration and stripping systems

� Camera inspection of potable storage tanks

� Open & closed filters

� SRO & electrical engineering

� Consultancy (nitrification, microiron, air stripping)


Danwatec – other expertise

• Advanced water treatment (Stengården Løsseplads, Kirke Hvalsø for Region Sjælland)

• Containerised water treatment (MålovKunstgræsbane)


Presentation overviewPart 1 – Introduction of softening

into Danish waterworks

• Where and why should we soften the drinking water?

• Pellet reactor– Why pellet reactor?– Our expertise – how it started– Method fundamentals– By-product: calcite pellets

• Economy, challenges and facts

• Current status

Part 2 – Corrosion and scaling

• Danish guidelines (Arbejdsrapport fra Miljøstyrelsen Nr 12 2005)

• Langelier Saturation Index

• German standard DIN 38404-10


Softening – where is a problem?

• Areas with hard water, >12 dH° , mainly Sjælland and Lolland

• 60% of Danish potable water


Softening – why bother? Benefits:

• Protection of household appliances

• Fewer repairs and maintenance needs

• Lower consumption of soap and

washing detergents

• Soft water good for skin and clothing

• Less scaling of filters and pipe network

• Less energy consumption / CO2 emission

• Less energy and resource to treat wastewater

(phosphorous removal)


Waterworks

Society

Customer

Why pellet reactor?Pros:

• “Easy” to run and control

• Minimum pollution risk

• Do not remove other minerals (Mg)

• Produced byproduct, pellets, easily to dispose (agriculture)

• Price, plant purchase

• Price, sales price of water

Challenges:

• Authorities approval for softening (advanced water treatment)

• Fitting into current Danish waterworks (footprint and building height)

• Steady water production

• Operation/control/economy

Generally it is the most promising technology for central

softening of drinking water

(Minimum energy consumption and water waste)


Our expertise in pellet method softening

• 2014: visit in Holland and started collaboration with Royal Haskoning DHV – developer of the pellet reactor (known as the Crystalactor®) since mid 1980’s and applied to Dutch waterworks for more than 20 years

• 2015: implementation of a pellet reactor pilot plant at Store Heddinge Waterworks, Stevns

• 2016: Exploring the Danish market:

– Dissemination of our expertise – counter fight the myths;

– Adopting the Crystalactor® technology into Danish waterworks

– Solution for handling chemicals and byproduct – pellets


Pellet reactor – principles (Crystalactor®)


Pellet reactor – pilot plant


Chemistry behind the process

Dosing of natrium hydroxide into the

reactor – CaCO3 precipitation

7

7,2

7,4

7,6

7,8

8

8,2

8,4

0

20

40

60

80

100

120

140

0 1 2 3 4

pH

Ca

og

Na

con

cen

trat

ion

[mg/

L]

NaOH dose [M]

Calcium Natrium pH

Addition of CO2 after reactor –finishing of the precipitation process by

neutrilizing remaining NaOH

7

7,2

7,4

7,6

7,8

8

8,2

8,4

0

50

100

150

200

250

300

0 0,4 0,8 1,2

pH

Bic

arb

on

ate

[mg/

L]CO2 dose [M]

Bikarbonat pH


Figure. Effect of Ca and Na concentrations vs NaOH dose


Optimal reactor sizeMeasured vs calculated rector

efficiencyTheoretical reaction pattern vs

reactor height

0,00

1,00

2,00

3,00

4,00

7,00

7,50

8,00

8,50

9,00

9,50

10,00

0 20 40

Cal

ciu

m [

mm

ol/

L];

SI C

alci

te(-

)

pH

Reactor height [m]

pH SI Calcite Ca

0,0

2,0

4,0

6,0

8,0

10,0

12,0

14,0

1,00 1,50 2,00 2,50 3,00

Har

dn

ess

rem

ove

d

NaOH dose

Measured CalculatedLineær (Calculated)

Pellets – softening process byproduct

Chemical quality of the pelletsUnit Pellets from raw

water

Pellets from

clean water

Magnesium % 0,3 0,3

Calcium % 29,9 35,1

Jern % 0,3 0,0

Strontium % 2,7 3,0

Barium % 0,125 0,125

Kopper % 0,010 0,025

Zink % 0,035 0,035


Image analysis

0

5

10

15

20

25

30

0 0,5 1 1,5

% o

f A

ll

Diameter [mm]

Pellets

SandPellets approved by SEGES, agricultural

consultant in Århus, to be used for conventional agricultural purposes (egg production)

Application of the pellet reactor –other challenges

Customers point-of-view:

• Price

• Price

• Price

• Healthy issues

• Taste

Point 2: Waterworks proffesionals can learn about the technology, but the hardest thing is to convince the customers.

Point 1: Does people know their current price of water?


Pellet method – economy• Aim: 1,50 – 2,0 kr. / m³

• Including:

– Investment

– Depreciation

– Chemicals

– Operation and maintenance

• Disposal of pellets = neutral (local farming)

0

10

20

30

40

50

60

12 11 10 9 8Pil

ler

pro

du

kti

on

[to

n/å

r]

Produced water hardness[dH]

Pellets production

12 11 10 9 8

Op

era

tio

na

l

ex

pe

nse

s[k

r./m

3]

NaOH kost CO2 kost El.energi


Softening with help of pellet reactor – healthy issue?

Calcium requirement in Danish diet

Mælkeprodukter Ost Drikkevarer

Brød og korn Grønsager Frugt

Kartofler Kød Fisk

Æg Juice Sukker og slik

Consequences of pellet reactorapplication for potable water treatment

Today Softened

water

Calcium concentration[mg/L] 120 40

Reccomended daily water consumption with respect to calcium intake (16% of 800mg/day) and concentration in potable water

1 L 3 L

In total 800 mg/day for an adult

http://altomkost.dk/fakta/mad-og-drikke/foedevarer/maelk-og-ost/kilder-til-calcium-i-kosten/


Pellet method – calcium REDUCTION not REMOVAL

A person in average consumes 7 L per day

in meals and beverages

Taste issue: softened and bottled water


Parameter

KildevandVand Grand Prix

2014

Blødgøring med pille

metoden

Egekilde Aqua D’OR ARWOS,

Aabenra

Før Efter

Kalcium

[mg/l] 57 36 70-77 100-120 40-50

Magnesium

[mg/l] - 3 5-7 18-25 16-23

Bikarbonat

[mg/l] 310 120 180-200 330-350 250-300

Hardhed

[dH°] 8 6 10-11 20-22 10

Pris

[kr./m3] 7.000 1.100 16 16,25 18

Store Heddinge Vandværk case


Period Event

Summer 2015 –Summer 2016

Implementation and run of the pellet reactor pilot plant:- Theory vs practice based on treatment of 2.400 m³ of water- Documentation of water and pellets qualityCampaigning locally for full-scale softening

Winter 2016 -Summer 2016

• Handling and approval for full-scale softening plant at the waterworks

• Preparing complete solutions for the full-scale treatment (handling of chemicals and pellets)

15th September 2016

2nd extraordinary general assembly for Store HeddingeWaterworks to decide about implementation of full-scale treatment (Vote: 99 in favor and 73 against)

Spring 2017 Full-scale softening plant in service

Direct savings with implementation of the softening :

Example of Store Heddinge Vandværk case


kr./m3 Naturstyrelsen analyse 2011

(hårdhed reduceres fra 22 dH til 8 dH°)

Deloitte report 2016

(Hårdhed reduceres fra 18,4 til 10 dH°)

Drift, anlæg og renter – ekstra omkostninger på vand -1,75Husholdninger

Levetid, husholdningsapparater + installationer

Energiforbrug, husholdningsapparater

Forbrug af vaskepulver til vaskemaskine

Vedligehold af husholdningsapparater

Forbrugertid på vedligehold af husholdningsapparater

Rengøring af baderum mm.

Forbrug af sæbe til personlig hygiejne

I alt

3,2

0,4

1,0

0,5

1,1

0,3

0,5

6,9

2,2

0,04

1,4

2,1 (Forbrugertid og vedligehold)

1,0 (Midler til vedligehold)

0,2

5,94

Eksternaliteter

- Hjerte-karsygdomme

- Huller i tænderne

- Vandforsyning, emissionsfaktorer

- Husholdninger, emisionsfaktorer

I alt

0,0

-1,9

-0,01

0,01

-1,9

0

-1,7

-1,7

Skatteforvridning 0,0 0,06

Direkte afgiftsændring -1,4 ?

Afgiftskorrektion 0,9 ?

BESPARELSE I ALT 2,85 3,55

Application of the pellet reactor

Part 2 – Corrosion and scalingparameters


Corrosion, metals dissolution and scaling factors based on Vejledning om metalliske materialer til vandinstallationer

(Arbejdsrapport fra Miljøstyrelsen Nr 12 2005) and LSI


Materiale Krav til vandkemi Produced water

today (pilot feed)

Softened water

(after pilot plant)

Mix 50:50 Soft + Hard

(Pilot produced + feed)Galvanized

steel

(Varmforzinke

t stål)

100 mg/L < [HCO3-] < 300 mg/L

365 High 290high

(lower than

today)

330high

(lower than

today)

([Cl]+2[SO4])/[HCO3-] < 1

0,62 ok 0,77 ok 0,68 ok

[Ca2+] > 20mg/L 125 ok 50 ok 88 ok

pH > 7 7,1 ok 7,5 ok 7,3 ok

Copper

(Kobber)100 mg/L < [HCO3-] <

240 mg/L365 High 290

high

(lower than

today)

330high

(lower than

today)

7 < pH < 9 7,1 ok 7,5 ok 7,5 ok

Tinned

copper

(Fortinnet

kobber)

7 < pH < 9 7,1 Ok 7,5 ok 7,5 ok

Stainless steel

(Rustfrit stål)[Cl] < 150 mg/L 42 ok 42 ok 42 ok

Langelier

Saturation

Index

LSI < 0 – scaledissolutionLSI = 0 – carbonates in equilibriumLSI > 0 – scaleprecipitation

-0,07(slightly

corrosive)

-0,05(slightly corrosive)

-0,07(slightly corrosive)

Softened and hard water mixtures (50/50) –different scenarios with regards to pH and LSI

-0,3

-0,2

-0,1

0

0,1

0,2

0,3

7

7,1

7,2

7,3

7,4

7,5

7,6

7 7,2 7,4 7,6 7,8 8 8,2

Lan

ge

lie

r S

atu

rati

on

Ind

ex

(-)

pH

-m

ixtu

re

pH of soft water

pH mix pH mix calc LSI

Water quality indicators

Simplified factors

• Bicarbonates

• pH

• Calcium

• Larson-Skold index:

• LSI – Langelier SaturationIndex:

pHs = (9.3 + A + B) - (C + D)

DIN 38404-10, 2012 Enable to calculate SI and CCPP (calcium

carbonate precipitation potential) with respect

to all specified aqueous species

A = (Log10 [TDS] - 1) / 10

B = -13.12 x Log10 (oK) + 34.55

C = Log10 [Ca2+ as CaCO3] - 0.4

D = Log10 [alkalinity as CaCO3]


Element Phase Dissolved species

CaCa2+, CaCO3

0, CaHCO3+, CaOH+, CaSO4

0, CaH2PO4+,

CaHPO40, CaPO4

-

MgMg2+, MgCO3

0, MgHCO3+, MgOH+, MgSO4

0, MgH2PO4

+, MgHPO40, MgPO4

-

Na Na+

K K+

C* CaCO3(s) H2CO3 (=CO2aq), HCO3-, CO3

2-

Cl Cl-

N NO3-

S* HSO4-, SO4

2-

P* H3PO4, H2PO4-, HPO4

2-, PO43-

H H2O H+, OH-

Still ”too” simple - not included:- other elements: fluor, strontium;- calcium carbonate phases: vaterite and aragonite

Simplified vs

comprehensive approach

Example: Mixtures with different

ratios of hard and soft water

(from pilot investigations)

Remarks:

- LSI and SI-Calcite (according to DIN 2012) – values differs, but are correlated;

- LSI and SI-Calcite – for bothindices mixtures are slightlycorrosive and with the same ”worst” case scenario at mix ratio 0,75

- CCPP – not related to LSI and SI-Calcite, for example the same SI of -0,07 does not give the same CCPP value


7,1

7,2

7,3

7,4

7,5

7,6

-0,08

-0,06

-0,04

-0,02

0

0 0,2 0,4 0,6 0,8 1

pH

SI C

alci

te (

-), C

CP

P (

mm

ol/

L)

Part of soft water [kg/kg total]

SI Calcite DIN

CCPP DIN

pH

7,1

7,2

7,3

7,4

7,5

7,6

-0,4

-0,3

-0,2

-0,1

0

0 0,2 0,4 0,6 0,8 1

pH

LSI

Part of soft water [kg/kg total

LSI pH

Mixing of softened water

(not effectively conditioned)

with hard water

Example: Mixtures with different

ratios of hard and soft water

(from pilot investigation)

CCPP in range 0,08-0,018mmol/L –potential of scaling 8 to 18 mg/L of calcium carbonate


7

7,5

8

8,5

9

00,10,20,30,40,50,60,7

0 0,2 0,4 0,6 0,8 1

pH

LSI,

SI-

Ca

lcit

e(-

)


LSI SI Calcite pH

7

7,5

8

8,5

0

0,05

0,1

0,15

0,2

0 0,2 0,4 0,6 0,8 1

pH

CC

PP

[m

mo

l/L]


CCPP pH

Conclusions and perspectives


• It is possible to introduce softening into Danish waterworks, when all parties accept its benefits and consequences;

• Still a lot have to be done to address myths and make fact based evaluation;

• Scaling and corrosion indexes only INDICATE but factual water mixes behavior shall be evaluated on empirical data;

• If indices used than preferably use CCPP instead of SI – quantify precipitation/dissolution potential with respect to water quality (CCPP and SI are only qualitatively related: ”+” for oversaturated and ”–” for undersaturated)

• Need for complementary standard to project and ensure safety water distribution; include other elements and calcium carbonate phases?

Questions?


Thank you for your attention!

adaption of pellet reactor softening method into …caog na concentration[mg/l] ph naohdose[m]...

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