Biofilms in swimming pool filters:
Blessing in disguise?
Ger Hulshof
Senior consultant water quality
11-02-2010
www.eurofins.com
Content
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Introduction
Research location: 25m pool Grote Koppel Arnhem
Research: approach and resources
Resume
Possible future research
Questions
ICSPS A'dam: 18th March 2015
Biofilms in swimming pool filters: Blessing in disguise?
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Introduction Eurofins & C-mark
Eurofins present in
more than 30 countries
ICSPS A'dam: 18th March 2015
Biofilms in swimming pool filters: Blessing in disguise?
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Research location: 25m pool Grote Koppel Arnhem (I-II)
ICSPS A'dam: 18th March 2015
Biofilms in swimming pool filters: Blessing in disguise?
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Research location: 25m pool Grote Koppel Arnhem (II-II)
Technical indicators 25m pool
Key figure
Specification
Water content 25m pool
Dimension filter (H x Ø)
750 m3
2 x 2.8 m
Content filterbed 2007-2013 (period 1)
Sand 0.4 - 0.8 mm + Hydroanthracite-N 0.8 - 1.6 mm
Content filterbed 2013- present (period 2 & 3)
0.5 m glass beads 0.50 - 0.75 mm + 0,5 m glass beads 0.40 - 0.60 mm
Backwash frequency filter
48 h
Circulation rate at daytime with 2 pumps
Filter flow rate at daytime with 2 pumps
206 m3/h
33.4 m/h
Flocculant
Locron® L, dilution 1:10, dosing period 24/7
Disinfection
Membrane salt electrolysis
Correction pH
Correction alkalinity
Sulfuric acid 37%
Sodium hydrogen carbonate (NaHCO3)
Number of visitors 2014 (25m pool)
Approximately 100,500
Mean fresh water addition 2014 per bather
Approximately 29 L/bather
ICSPS A'dam: 18th March 2015
Biofilms in swimming pool filters: Blessing in disguise?
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Research parameters
Parameters used for testing pool water quality 25m pool
Parameters mandatory by legislation
Additional parameters
pH value
Free available chlorine (FAC)
Total available chlorine (TAC)
Combined available chlorine (CAC)
Temperature (°C)
Permanganate value (KMnO4-value)
Urea
Heterotrophic plate count 37°C (HPC 37°C)
Conductivity (EC)
Calcium (Ca)
Bicarbonate (HCO3)
Chloride (Cl)
Nitrate (NO3)
Dissolved Organic Carbon (DOC)
Potassium (K)
Aluminum (Al)
Adsorbable organic halogens (AOX)
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Research periods
Three periods:
Double layer filtration with sand and Hydroanthracite-N
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Period 1: September 2012 - August 2013 (reference period)
Filtration with glassbeads
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Period 2: September 2013 – April 2014
Period 3: May 2014 – December 2014
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Biofilms in swimming pool filters: Blessing in disguise?
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Results period 1
Pool water quality 25m pool with sand and Hydroanthracite-N filtration
Parameter
Unit
Range
Mean ± SD
No of samples
EC 20°C
mS/m
190 - 98
157 ± 29
12
Bicarbonate
mg/L
59 - 20
40 ± 12
12
pH
7.40 - 7.10
7.3 ± 0.1
12
AOX
µg/L
580 - 220
470 ± 99
12
Potassium
mg/L
7.4 - 3.3
5.7 ± 1.4
12
Nitrate
mg/L
23.4 - 7.7
14.6 ± 5.1
12
Chloride
mg/L
330 - 150
264 ± 60
12
DOC
mg/L
3.2 - 2.0
2.8 ± 0.4
12
KMnO4-demand
mg/L
5.1 - 2.6
3.8 ± 0.7
12
FAC
mg/L
1.1 - 0.5
0.8 ± 0.2
12
CAC
mg/L
0.7 - 0.3
0.5 ± 0.1
12
Urea
mg/L
1.1-0.6
0.9 ± 0.2
12
pH value
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Biofilms in swimming pool filters: Blessing in disguise?
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Results history
Centrilab & RIVM 1990: Microbiological quality of filtermedia for the treatment of swimming pool water in circulation pools
Location Filtermedia
2
3
8
4
9
Sand
Sand
Hydroanthracite N
Hydroanthracite H
Activated carbon
ICSPS A'dam: 18th March 2015
Heterotrophic plate
count 37°C
Urea splitting
Organisms
Microscopic
counts
Myco bacteria
(/gram)
(/gram)
(/gram)
(/gram)
4.4x104
4.2.x104
4x105
3x103
1.1x104
3.9x104
5x107
2x104
3.5x104
1.1x105
5x106
6x102
3
4
6
3.2x10
2.3x10
6x10
4x103
1.5x106
4.4x106
2x108
>2x104
5
6
7
4.4x10
1.4x10
7x10
3x103
7.9x105
4.6x107
4x108
>2x104
5
6
9
3.5x10
3.2x10
1x10
1x104
3.0x106
4.4x107
2x109
>2x104
3.4x106
3.3x107
>6x1010
2x103
Biofilms in swimming pool filters: Blessing in disguise?
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Results period 1-2-3
History urea 25m pool
3,0
Urea (mg/L)
2,5
2,0
1,5
1,0
0,5
period 1
period 2
period 3
0,0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Months
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Biofilms in swimming pool filters: Blessing in disguise?
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Results period 2+3
3,50
3,00
C/C avg
2,50
2,00
Nitrate
DOC
1,50
KMnO4
Urea
1,00
0,50
0,00
1
2
3
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5 6 7 8 9 10 11 12 13 14 15 16
Months with glass beads filtration
Biofilms in swimming pool filters: Blessing in disguise?
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Results period 2+3
1,80
1,60
1,40
1,20
C/C avg
EC 20°C
1,00
Potassium
0,80
Chloride
AOX
0,60
KMnO4
Lineair (KMnO4)
0,40
0,20
0,00
1
2
3
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6
7
8
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Months with glass beads filtration
13
14
15
16
Biofilms in swimming pool filters: Blessing in disguise?
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Short additional research
Intensive backwash to remove accumalated “dirt”:
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Resume
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Active swimming pool filters contain biofilm
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Newly filled swimming pool filters do not contain biofilm
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No direct relation between organic matter and AOX was found
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“Dynamic deep bed filtration” with glass beads as filter material requires
different demands of operation
In a biofilm all conditions are present for microbiological conversion of urea
and nitrification
Foam formation during backwashing could be an indication of microbiological
processes
Findings seem to indicate that the increase of organic matter is a result of
non-optimal filter backwashing
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Biofilms in swimming pool filters: Blessing in disguise?
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Future research
In a biofilm biodegradation is expected.
When using chlorine, disinfection byproducts (DBP) are unavoidable.
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Can biodegradation contribute to minimize DBP formation?
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The 25 m pool of the Grote Koppel is a good test facility for research under
field conditions
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Certain facilities of the filter are not yet used and offer interesting
opportunities to examine processes in the filter
and/or
Will biodegradation lead to additional DBP formation?
ICSPS A'dam: 18th March 2015
Biofilms in swimming pool filters: Blessing in disguise?
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Questions
Thanks for your
attention:
ICSPS A'dam: 18th March 2015
Biofilms in swimming pool filters: Blessing in disguise?
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