Technical Options of Phosphorus Removal in
Wastewater Treatment plant (WWTP)
M. Barjenbruch, E. Exner
FG Siedlungswasserwirtschaft, TU Berlin
Gustav-Meyer-Allee 25, D - 13355 Berlin
Phone: +49 / (0) 30 / 314 72246; Fax: +49 / (0) 30 / 314 72248
e-mail: [email protected], [email protected]
Importance of phosphorus
12. frequent element of the crust of earth
 Phosphorus is a chemical element. Symbol P
ordinal number 15 and has a specific weight of 31 g/mol
 Greek φως-φορος „lichttragend“, given by the shining of the white
phosphorus in the reaction with oxygen.
 P was discovered in 1669 by Hennig Brand, a German pharmacist
and alchemist.
 Phosphorus is essential important for all organism.
 P-compounds are parts of DNA- and RNA-molecules
 The phosphorus containing compounds ADP/ATP are playing and
important parts in the energy metabolism of all cells.
 A man with 70 kg contains about 700 g phosphorus, from which 600 g
is bound in the bones
 Important nutrient for the growth of plants and essential fertilizer
 Main resources come from: Morocco, South Africa, Russia, China and
USA
Resource remain only according WHO only about 60-80 years
Objectives of the P-elimination
 Prevention of the eutrophication of water bodies. P effects in water bodies
eutrophication already in the lower range of microgram especially in:




 Lakes, dammed or tide influenced water bodies, Northern Sea of Baltic Sea
Factor of minimum for the growth of plants: N : P = 7:1.
Classification of lakes:
 Eutrophic; nutrient rich lakes, in depth about 0-30%,
O2-saturation, only 2 m sight in depth, high production of algae,
tot. P~ 45 - 85 g/l
River according the German Surface water ordinance
g P/l large rivers in the middle mountain; inlets to the Baltic Sea
 50
 50/100 g P/l all other rivers
Surveillance value of WWTP according wastewater ordinance
 10,000 - < 100,000 PE: 2.0 mg P/l

> 100,000 PE: 1.0 mg P/l
 Special regional restrictions!
Examples of Eutrophication
Origin and estimation of the specific P-load in municipal
sewage [in g P / (E·d)]
Origin of phosphorus
1975
2005
Metabolism products1)
1,6
1,6
Washing powder for textiles
2,252)
05)
Household detergents/washing-up liquid
0,752)
0,246)
Other P-sources3)
0,42)
0,054)
Sum, related to PE
5,0
1,9
Industry/trade/settlement aeras (as PE)
1,28)
1,27)
Average Concentration (mg/l)9)
15,7
6,9
Concentration in Germany: 5,6 - 14 mg P/l
Phosphorus in the sewage
 Main part of the total phosphorus (ca. 68%):
 In an inorganic solved status, mainly orthophosphate and
possible condensed phosphates
 Smaller part of the total phosphorus:
 organic solved and none solved mode (phosphonate, hardly
degradable organic P-compounds from textile industry and
from heat-/power-production)
 Condensed and organic parts of phosphorus will mainly
tranfered into ortho phosphates
 Only ortho phosphate can be removed from the water
by precipitation and following separation!
Processes of phosphorus elimination
 Phosphorus can not be transferred like as nitrogen into the
gaseous status and eliminated to the air.
 Phosphorus compounds must be removed from the wastewater in
a stable (solid) aggregated status bounded in separateble particles
via the sludge path.
 Processes of chemical P-elimination
Me3+ + PO43-  Me(PO)4  + Me (OH) metals: Fe3+, Al3+
 Pre-, simultaneous- and final pr, Nachfällung, or combination
precipitation
 Influence parameters for the efficiency of the precipitation
– Dosage
– β-relation factor
– pH-value
– Ca2+
– Particle separation
 Processes of biological P-elimination (Bio-P)
 Combination of Bio-P and chemical P-elimination
Processes of the chemical P-elimination
Pre-precipitation
= 2-3
CPe
PA
SF
Simultaneous
precipitation
= 1,2 – 1,5
Combined
precipitation
PA
PS
PA: preciptation agent
PA
AT
SS
PA
PA SS
= 1,2 – 1,5
PA PA
PS
TF/AT
PS
AT
2 mg/l
1-1,5 mg/l
z.T. < 1,0
= 2 – 2,5
PA
PA
SS
CF
< 0,5 mg/l
= 0,3 mg/l
Calculation of the amount of the precipitant
ß-value: relative amount of precipitant with the unit [mol Me/mol XP,Prec]
 prec
X Me / AM Me

X P , Fäll / AM P
with:
XMe
XP,Fäll
[mol Me / mol P ]
β = 1,0 stochiometric dosage
β = 1,5 50 % over stochiometric dosage
necessary amount of precipitant (metal) (mg Me/l sewage),
phosphorus to be precipitated (mg P/l sewage),
X P , prec  C P , In  C P ,out  X P , BM  XP , DN  X P , BioP
AMMe
atomic mass of metal (mg/mmol),
AMP
atomic mass of phosphors (mg/mmol)
and the atomic mass AM: (P) Phosphor: 31; (Fe) iron 56 ; (Al) aluminium 27
According the kind of bounded P in the sludge:
= 1,0 % (nitrification, COD Elimination)
XPBM
XPBDN = 0,5 % (denitrification)
XPBioP = 1,0 % (anaerobic tank)
Concurrent reactions
 Parallel to the precipitation reaction several concurrent
reactions appear:
 Hydroxyd development
Me3+ + 3OH-  Me(OH)3
 Carbonate development
Ca2+ + CO32-  CaCO3
 Komplexierung of organic substance
 Different reaction of adsorption
 Follow up’s of by-reaction
 Higher consumption of precipitation agent
 Increase of the sludge production
Amount of additional sludge
 The phosphate, hydroxides and all other flucculated
compounds formed by the precipitation agents produce
a higher amount of sludge (Dry solids (DS))
 2,5 g DS/g Fe (about 5,0 g DS/g P),
 4
g DS/g Al (about 4,0 g DS/g P).
 If you apply calcium products you have to calculate with
1.35 amount of flocculant as an increase of sludge:
 pH-value at 9,5 about 50 g DS/(PE  d),
 pH-value at 11 about 200 g DS/(PE  d).
 Theses additional amounts of sludge have be regarded
in the planning of the sludge treatment process!
Jar-tests with iron-(III)-chloride
Example
-value
0
1,2
2,0
2,8
3,6
Common precipitants
Product description
aluminium chloride
Iron (III)-chloride
Iron (III)-chloridsulphate
iron(II)-sulphate
Sodium aluminate
Chemical formu
AlCl3
FeCl3
FeClSO4
FeSO4 · 7 H2O
NaAl(OH)4
Calciumhydroxid
White lime hydrate
(extinguihedr lime)
stabilisied lime milkj
(20 %ig)
Ca(OH)2
polyaluminium-(hydroxid)chloride (PAC)
[Al(OH)3-xClx]n
typical
delivery form
density or
bulk density
[t/m3]
storage and
dosage
effective kation
for
P-precipitation
dilution
1,3
reservoir
acid-resitent pump
Al3+
dilution
1,41 – 1,43
reservoir
acid-resitent pump
Fe3+
dilution
1,43 – 1,52
reservoir
acid-resitent pump
Fe3+
residual damp
(green-) salt
1
Einsumpfbunker
acid-resitent pump
Fe2+  Fe3+
dilution
1,3 – 1,5
reservoir
pump
Al3+
powder
0,45
suspension
1,15
Silo
Schnecke
Tank
Exzenterpumpe
Ca2+
dilution
1,2 – 1,37
Al3+
reservoir
acid-resitent pump
According DWA 2011
common
active substances
per kg
delivery form
pH
from
(saturated)
dilution
58 – 60 g/kg
2,2 mol/kg
1
135 – 138 g/kg
2,4 – 2,5 mol/kg
1
123 g/kg
2,2 mol/kg
1
178 – 195 g/kg
3,2 – 3,5 mol/kg
62 – 105 g/kg
2,3 – 3,9 mol/kg
376 g/kg
9,4 mol/kg
75 g/kg
1,9 mol/kg
70 – 90 g/kg
2,6 – 3,3 mol/kg
2
14
12,5
1–3
Requirements on the an die pureness of
the flocculation agent
Parameter
[mg/mol ESMe]
Lead (Pb)
15
Cadmium (Cd)
0,2
Chromium (Cr)
15
Copper (Cu)
15
Nickel (Ni)
20
Mercury (Hg)
0,15
Zinc (Zn)
50
AOX
5
 Guidance values in flocculation agents to protect the
environment against heavy metal discharge
According DWA 2011
Dosage of the precipitation agent
 at locations with by flow increase turbulence
 in short distance of the storage tank
Protection pipe
 hydraulic direct jump
Increase of the cross section,
 absorption chamber of weirs,
Drop construction
junction of part flows
 Installation of mixer with a high frequency
 Installation of screens and static mixers
 Archimedes screw (e.g. filtration)
 Pressure side turbulence of pumps
 Aerated flow section
(Fe2+)
Example of good location for the dosage of
precipitations agents
Precipitation agent
blast pipe
Sewage
Cnannel
Venturi
Flow breaker
Break, bend
Examples of location for dosage
Bad solution
good solution
• bad mixing of the flocculant
• durch Randlage kaum B nearly no
contact to the complete water surface
• Dosage into the change of flow direction
• but better would be over the whole
cross-section
Examples of location for dosage
Good mixing conditions
• special injections form different side of
the pipe
• Against the flow direction
• also good mixing conditions
• but danger of corrosion
Storage of the flocculation agent
 Sealed filling place
 Separated catchment of
losses of the flocculation
agent
Principle of the enhanced biological P-elimination
B
ANAEROBIC
P-Release
A
PO4 -P
AEROBIC
P-Up-take
luxery uptake
C
Time
Biological P-elimination
Advantages:
 No additional agents (flocculants) necessary
 Decrease of salts in the effluent of a WWTP
 Lower additional sludge production
 No additional heavy metals in the sludge
 No disturbances possible for the nitrification process
Disadvantages
 Higher investment cost for the construction
of the anaerobic tank
 A little bit more instable process, so often additional chemical dosage
is required
 In winter time higher tendency of bulking sludge
Dimensioning
Contact time and Detention time
 Detention time
tR =
VAN
QIn
 Contact time
tc =
VAN
(Qrs + Q In)
 Dimensioning (biological P-elimination) DWA A 131
 anaerobic tank: > 0,5 to 0,75 h
 Regarding the maximum dry weather flow and the flow of the
return sludge
Bio-P
Phoredox-process (Detention time: 0,5 to 0,75 h)
aerated zone
anaerobic anoxic zone
zone denitrification COD-elimination
& nitrification
Inlet
= 1,2 – 1,5
PA
CPe
1-1,5
mg/l
2,0 mg/l
z.T. < 1,0
Effluent
Aeration
Internal recirculation
Secondary Settler
Return sludge
Excess Sludge
Example
WWTP Lübeck-Priwall
Modified-UCT-Process
Anaerobic Anoxic zone
aerated zone
zone denitrification COD-elimination &
Nitrification
Inlet
effluent
Aeration
interanl recirculation
Secondary
settler
Return slduge
Excess sludge
ISAH-process
Inlet
Anaerobic Anoxic zone
Aerated zone
zone
denitrification COD-elimination
& nitrification
Return
sludge
Denitrifcation
Effluent
Aeration
Internal recirculation
Secondary
Settler
Return sludge
Excess Sludge
P-elimination in Germany and DWA North-East
Ptot- mean values in WWTP effluent 1992 to 2009
Ptot-Effluent
values
Pges.-Ablaufwert
[mg/L] [mg/l]
4
3,5
3,5
Inlet:
14 – 5.6 mg P/l
3
2,5
2
1,70
1,5
2,4
1
0,5
Effluent:
1.0 – 0.49 mg P/l
1,20
1,00
Pges.Abl-Nord-Ost
2,4
1,70
1,00
Pges.-Abl. D[mg/L]
0,90
1,00
0,90
0,80 0,80 0,80
0,80 0,80
0,80 0,78 0,75
0,75 0,75
0,8
0,8
0,76
0,75
0,7
0,64
0,64 0,66
0,63 0,67 0,63
0
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
DWA, 2010
Year
Jahr
Effects of PA-consumption on Ptot-effluent
 with lower Ptot-Effluent value higher amount of precipitant is needed
60
CP,AN ≤ 0,5 mg/l
55
50
CP,AN ≤ 2,0 mg/l
10
73
45
KP [mol Me/kg P]
CP,AN ≤ 1,0 mg/l
15
107
40
14
44
35
30
25
20
26
38
14
15
10
5
0
Bio-P
Deni
Chem-P
Influence of the dosage location
Inlet to activated tank has the highest
floccucation agent demand  20-25%
60
55
Zulauf Biologie
Rücklaufschlamm
50
108
45
KP [mol Me/kg P]
Ablauf Biologie
Mehrfachdosierung
7
13
27
67
40
12
12
35
30
25
20
23
8
31
11
15
10
5
0
Bio-P
Deni
Chem-P
Thank your
for attention
Bio-P-Becken 1. Biologische Stufe