25 years of treating raw sewage with reed bed filters in ... · wetpol 2013 – nantes, october...
TRANSCRIPT
WETPOL 2013 – Nantes, October 14th, 2013
25 Years of Treating Raw Sewage
with Reed Bed Filters in France
A Personal History of Lessons Learned
Dirk ESSER
WETPOL 2013 – Nantes, October 14th, 2013
Short Biography
Studied HFCW (“root zone method”) with Prof. Kickuth in the 80’s
Came to France in 1988 for postgraduate studies
Worked with A. Liénard and C. Boutin at Cemagref (now IRSTEA)
on VFCW (“MPIP” or “Seidel System”)
Created SINT in 1991 to develop a modified MPIP-System under
license from Cemagref > “Phragmifilter®” (excl. license until 2003),
also known as “French System”, treating raw, unsettled sewage
WETPOL 2013 – Nantes, October 14th, 2013
In summer 2007, I sold the activity of SINT :
The « design and build » activity to
The « consulting engineers” activity to
becomes a one-man show
WETPOL 2013 – Nantes, October 14th, 2013
Development of RBF in France
• Today around 2300 RBF treating raw sewage
0
20
40
60
80
100
120
140
198
5
198
6
198
7
198
8
198
9
199
0
199
1
199
2
199
3
199
4
199
5
199
6
199
7
199
8
199
9
200
0
200
1
200
2
200
3
Nu
mb
er
of p
lan
t bu
ilt p
er
yea
r
0
50
100
150
200
250
300
350
400
Tota
l nu
mb
er
of p
lan
ts
Plant built per year Total number of plants
(500 designed by SINT between 1992 and 2007)
from Molle et al. (2005)
Founding of
SINT
WETPOL 2013 – Nantes, October 14th, 2013
WWTP along
the ages
5 Since 2000 : RBF
1970 - 1980: activated
sludge
1980 - 1990: waste
stabilsation ponds
1990 - 2000: rapid
infiltration (sand filters)
Fro
m : L
esa
vre
, 2
01
2
WETPOL 2013 – Nantes, October 14th, 2013
Exemple : WWTP financed by the Seine-Normandy water
authority between 2004 and 2006
1. Reed bed filters (CW)
2. Ponds (WSP)
3. RBC’s 4 . Activated sludge
(extended aeration)
Activated sludge RBC’s CW ponds
WETPOL 2013 – Nantes, October 14th, 2013 7
Reed bed
filters 12 %
Activated
sludge –
extended
aeration 35 %
Trickling
filters 9%
Facultative
ponds 24 %
Aerated
ponds 2 %
Other activated
sludge systems :
7%
RBC 2 %
Municipal WWTP in France (19300 plants)
according to water agency data base Lesavre, 2012
Sand
filters 1 %
WETPOL 2013 – Nantes, October 14th, 2013
Commercial development also stimulates and
finances research !
Approach in the nineties : « Trial and error » on full scale sytems,
monitoring of performance of full scale systems as « black box »
First 2 PhD thesis in 2003 : P. Molle – Cemagref (P-removal and
hydraulic limits) and F. Chazarenc - University of Savoy (System
optimization)
Since then 5 PhD thesis at Cemagref/IRSTEA : S. Troesch 2009
(sludge drying), J. Vincent 2012 (sludge drying), A. Morvannou
2013 (modeling of N-removal), J. Fournel 2013 (RBF for CSO), L.
Arias Lopez 2013 (RBF for combined sewers),
And 2 PhD thesis at EM Nantes : S. Prigent 2012 (N- and P-
removal), C. Barca 2013 (P-removal)
WETPOL 2013 – Nantes, October 14th, 2013
The general principle of a “French System”
Arrival of raw wastewater
1st siphon
-Stage 1 - 3 beds in parallel-
Treatment by reed bed filters
Retention of up to 90% of suspended solids
2nd siphon
Discharge Collection hole
-Stage 2-
Treatment by reed bed filters – 2 beds in parallel
WETPOL 2013 – Nantes, October 14th, 2013
Lay-out of a typical “French System”
1st stage: 3 * 0.4 m²
1.2 m2/p.e. (100 g COD .m-2.d-1 on the total filter
surface, max 0,7 m. d-1 on the filter in operation )
•Three parallel filters
•feeding/resting :3-4d/7d
2nd stage: 2 * 0.4 m²
0,8 m2/p.e.
•Two parallel filters
•feeding/resting: 7d/7d
Fine gravel Sand and fine gravel
WETPOL 2013 – Nantes, October 14th, 2013
Panorama
WETPOL 2013 – Nantes, October 14th, 2013 12
Montromant (200 p.e.) in summer 2013, after
19 years of operation, one desludging
WETPOL 2013 – Nantes, October 14th, 2013
®
Mean Median SD
10
percentile
20
percentile
30
percentile
40
percentile Nb
COD % 91,57 94,32 7,40 83,77 88,81 92,15 93,69 74
BOD5 % 97,37 98,29 3,09 95,28 96,61 97,22 97,75 74
SS % 96,65 97,72 3,24 93,05 95,59 96,28 97,29 74
TKN % 89,61 92,71 11,86 81,98 88,65 89,09 90,69 19
TP % 32,26 36,69 24,85 -2,10 21,04 25,94 31,05 19
Mean Median SD
80
percent
ile
90
percent
ile
95
percent
ile Nb
COD mg/L 50,27 41,00 28,89 62,60 73,00 91,40 74
BOD5 mg/L 7,91 5,00 9,09 10,40 15,70 19,70 74
SS mg/L 8,37 7,00 6,45 11,00 15,96 17,70 74
TKN mg/L 6,86 3,00 11,52 6,86 11,27 21,51 20
TP mg/L 5,70 5,70 3,05 6,94 10,25 10,82 20
Mean Median SD
10
percentile
20
percentile
30
percentile
40
percentile Nb
COD % 78,77 81,31 13,48 64,48 72,00 73,66 77,29 62
BOD5 % 86,33 89,95 13,49 70,50 80,75 84,84 86,92 61
SS % 84,63 86,09 9,99 71,76 78,18 79,61 81,40 61
TKN % 59,28 51,69 21,34 40,83 43,37 44,95 47,63 10
TP % 23,82 25,36 13,24 18,75 20,00 21,59 24,41 11
Mean SD
80
percentile
90
percentile
95
percentile Nb
COD mg/L 126,53 76,89 167 224,8 312,95 62
SS mg/L 31,61 20,15 50 62 64 62
TKN mg/L 19,69 14,55 25,2 38,6 46,3 11
Efficiency and outflow concentrations for the two stages
(from Epur Nature database)
Phragmifilter®
Efficiency and outflow concentrations for the first stage
WETPOL 2013 – Nantes, October 14th, 2013
The sludge retained on the first bed
looks like a compost
Sludge quality
Dry matter
Organic matter
WETPOL 2013 – Nantes, October 14th, 2013 15
WETPOL 2013 – Nantes, October 14th, 2013
Where we started from
16
St. Bohaire MPIP in
1982
WETPOL 2013 – Nantes, October 14th, 2013 17
1st vertical
2nd vertical
Horizontal
stages
WETPOL 2013 – Nantes, October 14th, 2013
Pont Remy Pilot plant 1985
– design Cemagref
18
WETPOL 2013 – Nantes, October 14th, 2013
The first pilot plant still in operation
since 1987 – design Cemagref (now IRSTEA)
• Gensac la Pallue (16), 1st stage : 8 RBF in parallel, 2nd stage : 3
ponds in series
Size 1700 pe,
102 kg BOD5/day,
255 m3/jour
Fictitious separate network:
hydraulic overloads >200% in
winter!
8 filters 240 m2 each, 1.1 m2/pe
3 ponds: total 9045 m2 , 5.3 m2/pe
WETPOL 2013 – Nantes, October 14th, 2013
So what did we know in 1991 ?
Gravel build VFRBF will not clog
when fed with raw sewage if there
are feeding and resting periods !
shadow
hygrometry
Organic deposits will go into active aerobic
mineralization during rest period (a bit less
in winter) -> important reduction of sludge
which becomes active media
The coarser particle size of fine gravel retains
less water by capillarity than sand -> if
aerated from below, they will remain aerobic
even with long periods of surface ponding
But do not give full treatment !
And if
planted !
WETPOL 2013 – Nantes, October 14th, 2013
But a lot of questions remained to be
solved…. • How do we polish the outflow (2nd stage) ?
• Optimal feeding and resting period ?
• How many beds in parallel ?
– Aim : reduce number of beds to reduce frequency of
changing the bed in operation
• How should we feed them ? (better than the gutter)
• How deep should the filters be ?
21
WETPOL 2013 – Nantes, October 14th, 2013
How do we polish the outflow
(2nd stage) ?
• A second stage vertical flow reed bed !
• Design inspired by experience with rapid
infiltration systems
… and international research findings
22
WETPOL 2013 – Nantes, October 14th, 2013
Optimal feeding and resting period ?
How many beds in parallel ? • One week of resting (experience from Gensac)
• Later confirmed by different studies that beds
recover (reoxygenate) in 4 to 5 days
• Observation that ponding increases after 3 or 4
days on the first stage, especially with high
hydraulic loads (combined sewers), in the start-up
phase and in winter !
• NH4+ adsorption decreasing with length of feeding
period (learned from work on sand filters)
23
WETPOL 2013 – Nantes, October 14th, 2013
How should we feed them ?
• 1st stage :
– point feeding (at least one point for 50 m²)
– siphon working with unsettled sewage when
gravity flow is possible
• 2nd stage
– perforated pipes for even distribution
24
WETPOL 2013 – Nantes, October 14th, 2013
1st stage : point feeding (H-system)
25
WETPOL 2013 – Nantes, October 14th, 2013
1st stage : siphon working with
unsettled sewage
1- Beginning of the cycle: the siphon chamber is
progressively filled with wastewater directly from
domestic sources
2- Simultaneously, the siphon floats and rises as the water
level in the siphon chamber continues to increase.
WETPOL 2013 – Nantes, October 14th, 2013
3- The siphon reaches its maximum vertical
position, where the siphon-stoppers block
further rising. Consequently, the water
overflows in the floater, entering through the
holes on the upper surface.
4- Due to the water flow into the floaters, the siphon
sinks and displaces the air in the pipes. This
creates a depression and aspirates wastewater.
WETPOL 2013 – Nantes, October 14th, 2013
5- The siphon chamber empties rapidly by the
siphon, due to the increased pressure and flow
of water, and ensures the required exit flow.
6- As the siphon chamber drains, the floater is
emptied, allowing the cycle to start again.
WETPOL 2013 – Nantes, October 14th, 2013
7- At the end of the cycle, only a small volume of water,
approximately ten litres, remains in the siphon chamber.
The siphon empties with an instant flush of at least 0,5 m3/h per m² of filter
surface in operation and we apply 2 to 3 cm at each cycle. The volume will be emptied in a few minutes.
WETPOL 2013 – Nantes, October 14th, 2013
2nd stage : perforated pipes for even
distribution
30
les siphons de type "eaux décantées"
Projet pérignieux Surface à alimenter : 140,00 m²
Date 23/08/04 DEBIT REQUIS en m3/h 70,00 m3/h soit 19,44 l/s
SIPHON queige
Cote de fond d'étage 1 576,40 m
hauteur géomètrique de l'axe
des trous sur le filtre 575,15 m
Siphon
E = 5,5
Matériau préconisé PVC PVC PEHD ou inox Nombre de trous suggéré 132
Matériau utilisé PVC PVC PEHD Nombre de trous 132
Diamètre exterieur (mm) 110 160,00 125,00 110,00 Débit par trou 0,152 l/s
Diamètre intérieur(mm) cf
Données0,09 m 150,00 117,40 90,00
Diamètre des trous 11 mm
Longueur (m) 28,00 5,00 11,00 44,00
Nombre (de bras, de
nourrices, de rampes)3 1 2 6 Pression de service
(>0,25)0,43 m
apérités (mm) cf Données 0,10 0,10 0,10 P = (Q/(2,1D²))²
Pertes de charge
singulières cf Données2,70 0,90 1,00
Pertes de charge totales 0,426 0,054 0,0299411 0,51
Débit (m3/h) 72,14 72,14 36,07 12,02
Vitesse (m/s) 1,05 1,13 0,93 0,52
Volume d'eau dans les
rampes0,49 0,05 0,07 0,62
576,09
576,09
--> débit du siphon 72,14 m3/h
0,31 m
Côte radier regard de décompression 575,83 fixer : fond d'étage 1 - 0,57
Hauteur d'eau pour pousser l'eau dans le coude0,18 0,03
Hauteur piézo à équilibrer pour sortie en coude 576,01 Hauteur piézo à équilibrer pour sortie en façade 576,01
575,37
0,50% 1,55%
Choix possible: Calypso, Lotus, Queige, Sirène, Gavrus
Commencer à 80 cm au moins sous le fond d'étage 1
Choisir un siphon (donc un nombre de bras) dans le classeur (ou "données") pour satisfaire le débit requis ; remplir toute les
cellules grisées
Premier pas : mettre la hauteur piezo "hypothèse" pour que le débit du siphon respecte le débit minimum requis…
Deuxième pas : ..et équilibrer la hauteur piézo hypothèse avec la hauteure piézo due à la sortie choisie (coude/façade)
Troisième pas : Vérifier que la hauteur de la charge en aval soit inférieur à la hauteur piézo
Cf. onglet
aide pour
détails
Total
Quatrième pas : vérifier queles résultats sont OK et qu'aucune cellule n'est en rouge
Cinquième pas : consulter l'aide pour jouer sur les différents paramètres
S ITROU
SORTIE EN COUDE
0,08 m
hauteur piézo mise en charge en aval
hauteur piézo hypothèse
entre le siphon
et système de
répartition
dans la nourrice
centrale
dans les
rampes
latérales
détail des rampes latérales
--> denivellé entre point bas marnage siphon et la
charge en aval :
--> fe coude
Perte de charge système
de répartition/pression de
service (<0,21)
0,20 m
résultats rampes
simulation regard de decompression et sortie vers filtre
Total de pertes de
charge dans le système
de répartition
Commencer avec : fond d'étage 1 (point bas de marnage) - 0,2 m puis équilibrer avec la hauteur
piézo de la sortie choisie
--> pente jusqu'aux trous si sortie en coude
SORT IE EN FACADE
Hauteur d'eau pour pousser l'eau dans la sortie en
façade
--> pente jusq'aux trous si sortie en façade
WETPOL 2013 – Nantes, October 14th, 2013
How deep should the filters be ?
• 1st stage : only 20 cm in Gensac
• 30 cm to 60 cm usual today (up to 0,80 m, 1m)
31
F. Chazarenc and G. Merlin : Influence of surface layer on hydrology and biology
of gravel bed vertical flow constructed wetlands Water Science & Technology Vol 51 No 9 pp
91–97
WETPOL 2013 – Nantes, October 14th, 2013
How deep should the filters be ?
32
Molle, P., Prost-Boucle, S., Lienard, A. (2008) : Potential for total nitrogen removal by combining
vertical flow and horizontal flow constructed wetlands: A full-scale experiment study. Ecological
Engineering 34, 23–29
Molle et al. did not find any difference in the performance of
a 60 cm and 80 cm deep 1st stage reed bed :
WETPOL 2013 – Nantes, October 14th, 2013
How deep should the filters be ?
• 2nd stage : 30 cm to 40 cm
33
Kayser K. and Kunst,S. (2005) : Processes in vertical-flow reed beds: nitrification,
oxygen transfer and soil clogging
Water Science & Technology Vol 51 No 9 pp 177–184
WETPOL 2013 – Nantes, October 14th, 2013 34
By courtesie of Chris Weedon
WETPOL 2013 – Nantes, October 14th, 2013
How deep should the filters be ?
We are still
searching
… (EPUR NATURE
pilot plant)
35
WETPOL 2013 – Nantes, October 14th, 2013
What can go wrong…
1. Non compliant treatment results
Too coarse filter materials or too shallow filters
Bad hydraulic design
Underloaded plants !
2. Failure of the system (clogging)
Too fine filter material
No adequate feeding and resting cycle
Dissapearence of reeds
For second stage only : overloading, ponding…
36
WETPOL 2013 – Nantes, October 14th, 2013
If there are no reeds, the system
will clog
37
WETPOL 2013 – Nantes, October 14th, 2013 38
WETPOL 2013 – Nantes, October 14th, 2013 39
August 2006 :
REVERSIBLE Clogging of a
second stage
WETPOL 2013 – Nantes, October 14th, 2013 40
Clogging of a second stage
Reversible ?
WETPOL 2013 – Nantes, October 14th, 2013
But globally, an excellent track record (from PACA region database, 140 plants, 81 SINT /
EPURNATURE)
41
Categorie COD (mg/L)
Non compliant > 125
Correct 125 - 90
Good 90 - 60
Very good 60 - 40
Excellent < 40
Excellent 57 %
Very good 25%
Compliant 6 %
Good 12 %
WETPOL 2013 – Nantes, October 14th, 2013
Past and ongoing research :
• More compact systems
• Adapting RBF to variable loads
• N - removal
• P- removal
• Stormwater and urban runoff treatment
• Adapting RBF to tropical climates
42
WETPOL 2013 – Nantes, October 14th, 2013
More compact systems :
recirculation
43
Raw wastewater inlet
Inlet pumping station
Flow splitter for recirculation
Discharge
Prost-Boucle S.. Molle P. (2012). Recirculation on a single stage of vertical flow constructed wetland: treatment limits
and operation modes.. Ecological Engineering 43, 81– 84
WETPOL 2013 – Nantes, October 14th, 2013
More compact systems :
stacked filters
44
Aerobic filter zone
Saturated anoxic zone
BiHo Filter® from EPUR NATURE
WETPOL 2013 – Nantes, October 14th, 2013
Adapting RBF to variable loads
45
Boutin,C. , Prost-Boucle, S. , Boucher, M. : Robustness of vertical Reed Bed Filters facing loads
variations: the particular case of campsites . Proceedings of the 12th IWA conférence on Wetland
Systems. 3rd – 9th of October 2010. Venice. Italy
Organic pollution removal is stable, nitrification is not
WETPOL 2013 – Nantes, October 14th, 2013
Adapting RBF to tropical climates
Mayotte
New Caledonia
French Guyana
Poster N° 110
WETPOL 2013 – Nantes, October 14th, 2013
http://www.globalwettech.com
WETPOL 2013 – Nantes, October 14th, 2013
Thank you for your attention
Two stage of feed bed filter, pond for stormwater overflow and
polishing surface flow wetland , SILLE GUILLAUME, Sarthe, 4000 p.e.