OFFICE INTERNATIONAL DE L'EAU
Développer les compétences pour mieux gérer l'eau
TECHNICO-ECONOMIC FEASIBILITY
OF PHOSPHORUS RECOVERY
FROM THE WASTEWATER TREATED
BY MUNICIPAL TREATMENT PLANTS
Nicolas JEANMAIRE – Office International de l’Eau
Rue E.CHAMBERLAND
87065 LIMOGES CEDEX
France
n.jeanmaire@oieau.fr
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
Introduction
For some years, varied experiments in the field of phosphorus recovery from
wastewater, have begun all over the world. These initiatives have been motivated by different
objectives. The basic research, the search for a durable development of the phosphorus
industry, the possibility of obtaining a material presenting lower heavy metal contents than
mined P-rock, the use of phosphorus recovery techniques to improve the operation of water
treatment plants, …, are some of the many reasons for research in the field.
Faced with this research work, often meeting specific concerns, a first inventory has
been made during the first international conference on phosphorus recovery, which took
place in Warwick (UK) on 6 and 7 May 1998. The second international conference (12-13
March 2001 in Noordwijkerhout –The Netherlands-) proved that the knowledge had
progressed and that new projects were in motion.
This article is a synthesis of the major works made to date, in order to know the real
feasibility of phosphorus recovery in municipal European wastewater treatment plants. An
investigation consisting of two different parts has been conducted by the Office International
de l’Eau on the question: “are the phosphates removed in municipal wastewater treatment
plants technically and economically recyclable”:
A study of the bibliography on a world-wide scale in order to grasp the current and
past researches, the techniques used and the main parties involved in the matter.
Interviews of specialists and operators in order to analyse the returns of experiences
from the field and operators’ opinions.
33 experts involved in the subject have been consulted among which: managers of
research centres, private and public operators, academics, industrialists, representatives of
the water authorities and consultants specialised in fertilisers.
The investigation concerned 9 European countries and Japan. The study covered both
the technical angles of P-recovery and its economic prospects. The conclusions of this
investigation have been compared with the theoretical calculations of the effects on the
sludge production obtained with a model developed by the water industry

The technologies of phosphorus recovery
1. Main technologies
We limited our study to hypotheses of phosphorus recovery as struvites or as
calcium phosphates, via precipitation or crystallisation. Other routes (aluminium phosphates,
ion exchangers, for instance) have not been enough studied yet, so no thorough study can
be carried out, or their large-scale implementation is too hypothetical.
Two major principles emerge from the analysis of these technologies: the
Mainstream P-recovery and the Sidestream P-recovery. In municipal wastewater treatment
plants and especially in the countries where P-detergents are forbidden, the Mainstream
technique is difficult to implement because P-contents in the wastewater are too low. This
technique is more appropriate to an industrial context (for instance: D.DONNERT and al [1]).
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
2
The Sidestream technique, consisting in generating P-rich flows or in using
existing flows is more appropriate to the municipal context.
The literature already describes largely the techniques of phosphorus recovery
and these angles are not repeated in this article :
Subject
Bibliographical references
Conditions of precipitation / Geestmerambacht’s WWTP (the Netherlands)
calcium
phosphate Westerbork’s WWTP 1988–1991 (the Netherlands)
crystallisation
A.GIESEN [2]
 Anglian Water (UK) ; A.CROOK & al [3]
Water Research Institute (Italy) ; D.MARANI & al [4]
University of Karlsruhe (Germany) ; Y.SONG & al [5]
Conditions of precipitation /  Thames Water (UK) ; Slough WWTP
struvite (MAP) crystallisation
Y.JAFFER & al [6]
 Unitika Ltd (Japan) ;Y.UENO [7]
 Department of Environmental Engineering (Turkey)
I.CELEN &t al [8]
 University of Alabama (USA) ; K.OHLINGER & al [9]
 JIWET (Japan) ; K.KUMASHIRO & al [10]
Treviso WWTP (Italy) ; P.BATISTONI & al [11]
Quality of the recovered  R.ANGEL [12]
phosphorus
 S.BRETT & al [13]
K.KUMASHIRO & al [10]
Y.UENO [7]
As regards phosphorus recovery in a WWTP, the technical requirements and the
infrastructure constraints have been fixed. They are listed in chart 1.
2. Calculation of sludge reduction
In order to assess the effect of P-recovery on sludge production, different
calculations have been made, based on the CIRSEE (Centre International de Recherche sur
l’Eau et l’Environnement - Lyonnaise des Eaux) model and on the researches of N.JARDIN
&t al [14] and Y.COMEAU [15].
The CIRSEE model on the simulated scenarii leads to a sludge production
estimated to 1,05 kg SS produced/kg BOD5 removed.
The calculations are based on the principles below :
The Sidestream P-recovery requires an anaerobic release of the phosphorus
overassimilated during the biological P-removal.
The P-release goes together with a joint release of cation type Mg 2+ and K+,
which reduced thus the sludge production. The hypotheses kept to assess the
importance of the reduction are as follows:
-2 to 2,4 g SS/g P released N.JARDIN [16]
-1,6 g SS/g P released Y.COMEAU [17]
The table below summarises the different results for an activated sludge WWTP in
extended aeration treating a mean effluent ([BOD5] = 300mg/l ; [SS] = 250 mg/l ; %SVM =
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
3
70% ; F/M ratio = 0,1 kg SS produced / kg BOD5 removed. The comparisons expressed in
the table below give the differences of sludge production between a WWTP equipped with a
biological P-removal and the same WWTP where a P-recovery technique is used :
% P recovered
WWTP
in
60 %
75%
90%
% of sludge reduction
(mean value - Dried
Solids)
% of sludge reduction
with
anaerobic
digestion (mean value –
Dried Solids)
2,3%
3%
3,5%
3,4%
3,8%
5,2%
On the average of scenarii, the sludge reduction is estimated between 2 and 8% of the
dried solids.
3.Technical consequences on the operation of the WWTP
Through analyses and calculations it has been possible to identify potential
positive repercussions for the water industry. However, there are also direct consequences
on the time necessary to operate the processes of recovery, on the consumption of reagents
and energy:
 Limitation of P-rich flows returning to the head of the WWTP. So the efficiency
of the biological P-removal is improved through the increase of the ratio
DBO 5
P
.
 Reduction of technical problems and of costs incurred by the unexpected
struvite precipitation which generally occur on the sludge treatment processes.
These problems are largely dealt with in the scientific literature (S. Williams
[18], AE. Durrant & al. [19], S. Parsons [20] and Mohajit & al [21]). Among the
harmful consequences on the operation, we may list:




the reduction in the diameters of pipes,
the clogging of valves, press casings …,
the clogging of the belts in filter belt presses,
the phenomena of abrasion of some rotary appliances (pumps,
centrifuges …) etc.
 In the areas where phosphorus is a limiting factor for sludge spreading in
agriculture, the P-recovery logically permits to decrease the P-concentration in
the sludges and so enables to reduce the surfaces required for spreading and
the costs of transportation necessary to reach the fields.
 When sludges are incinerated in the cement works, phosphorus is a limiting
factor. An OFEFP technical document [22] recommends a limit value of 0.5 %
P2O5 / cement (% of the weight). The reduction of phosphorus in the sludges
partly solves the problem.
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
4
 The reduction in sludge production. This reduction may be expressed in two
different ways:


plotted to the total production of dried solids, the simulations of
calculation indicate a potential reduction in the total sludge production
between 2 and 8 % (range comprising a comparison between a bio-P
WWTP and a bio-P WWTP recovering phosphates.
plotted to the total production of ashes after incineration (reduction of DS
by a factor 6), this reduction could reach values comprised between 12
and 48 %. Allowing for the current costs of a controlled landfill, this
reduction has a direct repercussion on the financial aspects of the final
reuse of sludges.
Researches are compulsory to confirm practically the results obtained through
calculation.
 Economic angles of phosphorus recovery
Since the technical repercussions of the phosphorus recovery vary according to
local contexts, it is hard to define globally the economic feasibility of the recovery. In the table
hereafter we only give a list of the expenses and receipts resulting from this recovery.
Expenses
-Investment and depreciation costs
Receipts
-Sale of the recovered phosphates
-Consumption of reagents and of energy
-Savings due to the suppression of problems
of struvite deposits
-Additional operating time
-Specific training of the operating staff
-Possible
reduction
of
transportation
distances for the agricultural reuse.
- Savings due to the optimisation of returns to
head
- Savings on the landfill of incineration
ashes..
Although it is clear that, in the future, specific studies should be developed in
order to analyse all these parameters, we may however put forward some indicators.
a) The expenses:
 The investment and depreciation costs depend a lot on the local context, on
the choice of the P-recovery technology and on the changes on the existing
WWTP.
 The cost of the consumption of reagent: it depends of course on the choice
between struvite recovery and calcium phosphate recovery. Moreover, it
varies twice:
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
5


from a technical angle, the needs in reagent (to increase the pH value,
to obtain ratios necessary for phosphorus precipitation or crystallisation)
strongly depend on the initial properties of the wastewater and on the
type of reagent which is used.
From an economic angle, because the price of reagents varies a lot
from one country to another. Nevertheless interesting alternative
solutions can be considered:
-Use of sea water as a source of magnesium [10]
-Use of industrial by-products (concentrated in magnesium or
calcium)
 The additional time of presence required from the operating staff. Today, it is
estimated to between 1 and 2 h/day.
 The training of the staff on the operation of the WWTP and on the safety as
regards the use of reagents. Depending on the prior knowledge of the staff, it
is estimated to between 2 and 10 days.
b) The receipts:
 The sale of the recovered phosphates. It also depends much on the context
of the recovery. Values comprised between 1235 and 2833 €/ton of
recovered P (struvites) have been reported.
However, we remember that the average price of the delivered P-rock for the
north of ’Europe is approximately 320€/t P [23] and that the average price of
P-fertilisers is 1150 €/t P [24].
According to the context, the sale of the recovered phosphates may cover part
or the whole of the costs of the recovery. However, allowing for the expenses
of marketing and distribution, the operators do not consider the sale of the
recovered product as a business purpose but rather as a disposal process.
 The saving resulting from the limitation of struvite problems directly depends
on the importance of the problems. In the case of chronic situations, some
operators reported annual costs of 65000 €/year/WWTP.
 Possible reduction of transportation distances for the agricultural sludge reuse.
This criteria is variable. It depends on the P-limit values determined according
to the needs of the cultivations and the P-contents of the fields. Moreover the
transportation distance also depends on the local context. This argument has
been largely dealt with by T.EVANS [24].
 Savings due to the optimisation of returns to head. They are also linked to the
prior state of the WWTP.
 Savings due to the landfill of incineration ashes. Although further researches
are required, when taking as a basis a reduction factor of 6 for the sludgesash volume and an approximate cost of landfill of 228 €/t ash (average price in
France), the saving could be about 68 € /t ash.
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
6

Regulatory status of recovered P
The P-recovery from the wastewater leads to the production of a new product
that is differently considered by the parties involved in the process: waste from the water
treatment, raw material or fertiliser. There is still an outstanding question: how will this byproduct be treated in the regulations?
As reminded by W.SCHIPPER (37), this notion of regulations is fundamental for
the prospects of large-scale recycling of a waste.
We may consider that the recovered P, coming from wastewater treatment, is a
by-product, which seems to be the case if we follow the regulatory logic of some countries
(France, England, Holland, Italy, Finland and Ireland).
However, the term waste is maybe not appropriate to a type a product that has
some purity. Such a designation could be harmful to the prospects of recycling.
Most of the specialists met point out that a certification or even a standardisation
of the product would be positive to put forward the quality of the product and promote its
reuse.
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
7
Conclusion
Is it technically and economically possible to recover phosphorus from the
wastewater treated by treatment plants?
The investigation conducted in Europe, brings us to think that today:
 It is technically possible to recover P in the municipal wastewater.
Several processes enabling such recovery are already available for municipal
water treatment plants. These processes can be implemented properly provided that
the biological treatment plant is of the activated sludge type and is equipped with a
biological P-removal. In that case the following configurations or fittings are required :


An anaerobic area, where the overassimilated phosphorus is released
(specific unit or anaerobic digestion tank).
A separating structure, permitting the formation of a P-rich, liquid
supernatant on which the recovery is made either by precipitation or
crystallisation.
In the current state of knowledge, this context seems to condemn the use of
mainstream-located processes given the weak phosphorus concentrations in municipal
wastewater.
These conditions determine the conceivable degree of recovery, which is of
75% of WWTP inflow P according to the specialists we met.
The main motivations for phosphorus recovery have been set. They reveal that:

The quality of the recovered product seems to be better than that of
the P-rock, as regards the heavy metal contents.

The driving forces for phosphorus recovery for purposes of recycling
depend a lot on the national context.
About this subject, the recovery is already registered as a national objective in
Sweden, and this notion of recycling is becoming a regulatory requirement. In the
other countries, the P-recovery follows different logics:

The search of a sustainable development via the recycling of the
recovered product in the phosphorus industry. This notion is very
strong in the Dutch context.

The use of techniques of recovery to solve internal problems of
sewage treatment plants, operations. In some cases, the P-recovery
has many advantages, listed in §3.
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
8
 It is impossible to give a final opinion on the economic feasibility of a
large-scale phosphorus recovery.
Before recycling a by-product, it is essential to wonder whether there are
potential markets. Today the ways of reuse consist in recycling the recovered
phosphorus in the industry of detergents or in the industry of fertilisers. Apart from the
case of Thermphos International, the ways of reuse in the P-industry must be clarified
and developed. The reuse of recovered P (struvite) as a fertiliser remains unproven as
a reliable route in Europe. In either case, the selling price of the recovered P will be
limited to that of P-rock or fertilisers and would hardly cover the purchase of the
reagents implied by the processes of recovery. The resale of the recovered P as a
component of fertilisers could permit however to get a better price.
If there is an economic feasibility, it is not based at the moment on the revenues
of the sales of those products. So phosphorus can be economically recovered if other
parties pay for part or the whole of the costs. There are two conceivable prospects:

The water industry pays the costs, because they permit to develop
techniques leading to optimisations of the operation or to sustainable
routes of sludge disposal. The costs will then be covered by savings
made on the balance sheet of operation of the treatment plant. In that
case we may speak of an economic feasibility relating to the specific
local context.

The arguments of sustainable development or of better quality of the
recovered product are estimated sufficient to make of P-recovery a
national objective. In this case, the consumers and/or taxpayers share
the costs, which is the case of the Swedish initiative. Then we may
speak of large-scale, regulation-driven economic feasibility.
In any case, the development of phosphorus recovery strongly depends on the
feasibility and reliability of the routes for reuse of the recovered P. In this context, the
better quality of the recovered P compared with the P-rock (heavy metals) could be a
strong argument encouraging P-recycling as a substitute for mined P-rock. But first of
all the regulations should not be an obstacle to this circuit of recycling (classification
not as a waste).
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
9
BIBLIOGRAPHY
1/DONNERT D. &. SALECKER M (GERMANY). ELIMINATION OF PHOSPHORUS FROM
WASTE WATER BY CRYSTALLIZATION. ENVIRONMENTAL TECHNOLOGY, 1999, 20,
n°7, p : 735-742
2/GIESEN A. CRYSTALLISATION PROCESS ENABLES ENVIRONMENTAL FRIENDLY
PHOSPHATE REMOVAL AT LOW COSTS. ENVIRONMENTAL TECHNOLOGY, 1999, 20,
n°7, p : 769-776.
3/CROOK A, Experimental investigation of effective and economic pathways to recover
phosphorus from return activated sludge, paper presented during the second international
conference about P-recovery - submitted.
4/MARANI D., DI PINTO A.C., RAMADORI R. AND TOMEI M.C. PHOSPHATE REMOVAL
FROM MUNICIPAL WASTEWATER WITH LOW LIME DOSAGE. ENVIRONMENTAL
TECHNOLOGY, 1997, 18, p :225-230.
5/SONG Y, HAHN H, HOFFMANN E, THE EFFECTS OF pH AND Ca/P RATIO ON THE
PRECIPITATION OF CALCIUM PHOSPHATE, paper presented during the second
international conference about P-recovery – submitted.
6/JAFER Y, CLARK T.A, PEARCE P & PARSONS S.A, Assessing the potential of full scale
recovery by struvite formation, Water Research – submitted.
7/UENO Y, FUJII M, 3 years operating experience selling recovered struvite from full-scale
plant, paper presented during the second international conference about P-recovery –
submitted.
8/CELEN I, TURKER M, RECOVERY OF AMMONIA AS STRUVITE FROM ANAEROBIC
DIGESTER EFFLUENTS, paper presented during the second international conference about
P-recovery - submitted.
9/OHLINGER K. N., SCHROEDER E. D., YOUNG T. M. POSTDIGESTION STRUVITE
PRECIPITATION USING A FLUIDIZED BED REACTOR. JOURNAL OF ENVIRONMENTAL
ENGINEERING,2000, 126, n°4, p :361-368.
10/KUMASHIRO K, ISHIWATARI H, NAWAMURA Y, A pilot plant study on using seawater
as a magnesium source for struvite precipitation, paper presented during the second
international conference about P-recovery – submitted.
11/BATTISTONI P., PAVAN P., CECCHI F.AND MATA-ALVAREZ. PHOSPHATE
REMOVAL IN REAL ANAEROBIC SUPERNATANTS : MODELLING AND PERFORMANCE
OF A FLUIDIZED BED REACTOR. WATER SCIENCE AND TECHNOLOGY,1998, 38,
n°1,p :275-283.
12/ANGEL R.(AUSTRALIA). REMOVAL OF PHOSPHATE FROM SEWAGE AS
AMORPHOUS CALCIUM PHOSPHATE. ENVIRONMENTAL TECHNOLOGY, 1999, 20, n°7,
p : 709-720
13/BRETT S., GUY J., MORSE G. K. PHOSPHORUS REMOVAL AND RECOVERY
TECHNOLOGIES. ENVIRONMENTAL AND WATER RESOURCE ENGINEERING
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
10
SECTION, IMPERIAL COLLEGE OF SCIENCE, TECHNOLOGY AND MEDICINE,
LONDON, 1999, 142 P.
14/JARDIN N & POPEL HJ, INFLUENCE OF ENHANCED BIOLOGICAL PHOSPHORUS
REMOVAL ON SLUDGE TREATMENT, Water Science and Technology (1993), 28, p263271
JARDIN N & POPEL HJ, WASTE ACTIVATED SLUDGE PRODUCTION OF THE
ENHANCED BIOLOGICAL PHOSPHORUS REMOVAL PROCESS, Wat Environment
Research, vol 69, n°3, May-June 1997, p375-381.
JARDIN N & POPEL HJ, REFIXATION OF PHOSPHATES RELESED DURIND BIO-P
SLUDGE HANDLING AS STRUVITE OR ALUMINIUM PHOSPHATE, paper presented
during the second international conference about P-recovery – submitted
15/COMEAU Y, LA DEPHOSPHATATION BIOLOGIQUE – METABOLISME MICROBIEN,
Sciences et Techniques de l’Eau (1990), vol 23 n°1, p47-60
16/JARDIN N, personal discussion on 5th of March 2001.
17/COMEAU Y, personal e-mail discussion on 2nd of March 2001
18/WILLIAMS.S. STRUVITE PRECIPITATION IN THE SLUDGE STREAM AT SLOUGH
WASTEWATER TREATMENT PLANT AND OPPORTUNITIES FOR PHOSPHORUS
RECOVERY. ENVIRONMENTAL TECHNOLOGY,1999, 20, p :743-747.
19/ DURRANT A. E., SCRIMSHAW M.D. , STRATFUL I. & LESTER J.N.(UK). REVIEW OF
THE FEASIBILITY OF RECOVERING PHOSPHATE FROM WASTEWATER FOR USE AS
A RAW MATERIAL BY THE PHOSPHATE INDUSTRY. ENVIRONMENTAL TECHNOLOGY,
1999, 20, n°7, p : 749-758
20/PARSONS S, STRUVITE PRECIPITATION, Scope Newsletter n°41, p15-22
21/MOHAJIT, BHATTARAI K.K, TAIGANIDES E.P & YAP B.C, STRUVITE DEPOSITS IN
PIPES AND AERATORS, Biological Wastes 1989, 30, p133-147
22/Office Fédéral de l’Environnement des Forêts et du Paysage (Suisse),
INCINERATION DES BOUES D’EPURATION, cahier de l’environnement n°156, août 1991.
Disponible sur : http://www.buwal.ch/publikat/f/index.htm
23/WOODS N. C., SOCK S. M., & DAIGGER G. T. (USA) - PHOSPHORUS RECOVERY
TECHNOLOGY MODELING AND FEASIBILITY EVALUATION FOR MUNICIPAL
WASTEWATER TREATMENT PLANTS. ENVIRONMENTAL TECHNOLOGY, 1999, 20, n°7,
p : 663-680
24/SITE WEB ADEME, http://www.ademe.fr/
25/EVANS T, IMPLICATION OF WITHIN-WWTP P-RECOVERY FOR BIOSOLIDS
MANAGEMENT : BIOSOLIDS VOLUMES, N/P RATIO & RECYCLING (AGRONOMIC, LCA
AND ECONOMIC IMPLICATIONS) – A EUROPEAN PERSPECTIVE. Paper presented
during the second international conference about P-recovery – submitted.
____________ Office International de l'Eau ___________________________________________
D:\219534309.doc\22/07/16
11