25 years of treating raw sewage with reed bed filters in ... · wetpol 2013 – nantes, october...

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

[email protected]

mailto:[email protected]


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


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


Development of RBF in France

• Today around 2300 RBF treating raw sewage

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Tota

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of p

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Plant built per year Total number of plants

(500 designed by SINT between 1992 and 2007)

from Molle et al. (2005)

Founding of

SINT


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


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 %


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)


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


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


Panorama


Montromant (200 p.e.) in summer 2013, after

19 years of operation, one desludging


®

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


The sludge retained on the first bed

looks like a compost

Sludge quality

Dry matter

Organic matter


Where we started from

16

St. Bohaire MPIP in

1982


1st vertical

2nd vertical

Horizontal

stages


Pont Remy Pilot plant 1985

– design Cemagref

18


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


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 !


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


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


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


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


1st stage : point feeding (H-system)

25


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.


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.


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.


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.


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


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



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 :



• 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


By courtesie of Chris Weedon



We are still

searching

… (EPUR NATURE

pilot plant)

35


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


If there are no reeds, the system

will clog

37


August 2006 :

REVERSIBLE Clogging of a

second stage


Clogging of a second stage

Reversible ?


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 %


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


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


More compact systems :

stacked filters

44

Aerobic filter zone

Saturated anoxic zone

BiHo Filter® from EPUR NATURE


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


Adapting RBF to tropical climates

Mayotte

New Caledonia

French Guyana

Poster N° 110


http://www.globalwettech.com


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.

25 years of treating raw sewage with reed bed filters in ... · wetpol 2013 – nantes, october...

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