Phosphorus speciation in drinking water treatment residuals

Journal of Environment and Earth Science www.iiste.org
ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online)
Vol 1, No.1, 2011

Phosphorus Speciation in Drinking Water Treatment
Residuals (WTRs) and Biosolids-Amended Soils Using
XANES Spectroscopy
Mahdy Ahmed
Department of Soil and Water, College of Agriculture, Alexandria University, Alexandria
Elshatby,21545, Alexandria University, Alexandria, Egypt
Tel: 003-02-5904684 E-mail: amahdy73@yahoo.com

Elkhatib Elsayed
Department of Soil and Water, College of Agriculture, Alexandria University, Alexandria
Elshatby,21545, Alexandria University, Alexandria, Egypt
Tel: 003-02-5904684 E-mail: selkhatib1@yahoo.com

Fathi Nieven
Salinity and Alkalinity Soils Research Laboratory
Ministry of Agriculture, Cairo, Egypt
Tel: 003-02-5046479 E-mail: nieven74@yahoo.com

Lin Zhi-Qing
Environmental Sciences Program & Department of Biological Sciences
Southern Illinois University, Edwardsville, Illinois 62026, USA
E-mail: zhlin@siue.edu

Abstract
X-ray absorption near-edge structure (XANES) spectroscopy (a non-destructive chemical-speciation
technique) is a useful technique available for determining the speciation of P in various environmental
samplesTwo incubation studies were conducted to assess the P species formed in an originally neutral
and alkaline soil in response to high biosolids and/or WTRs applications using P K-edge X-ray
absorption near edge structure (XANES) spectroscopy. The results indicated that combination of P
standards yielding the best linear combination fits for biosolids were phytic acid (26.03%) and
Cu3(PO4)2 (73.09%) and a little of P-sorbed to Al hydroxide (0.89%). However, The combination of P
standards yielding the best linear combination fits for WTRs were P-sorbed to Fe hydroxide (64.19%),
phytic acid (30.72%) and P-sorbed to Al hydroxide (5.07%). The P speciation in 10 g kg-1-treated clay
soils were phytic acid (19.08%), Mn3 (PO4)2 (0.79%), Phytic acid(K,Mg salt)(11.22%), Cu3(PO4)2
(7.26%), and hydroxyapatite (57.98%). Addition of WTRs modified the P speciation in biosolids-
amended soils, and the changes varied depending on biosolids and WTRs application rates. The P
speciation in soils depends on the soil type and application rates of biosolids and WTRs.
Keywords: Biosolids, P, XANES, WTRs, Soils
1. Introduction
Land application of biosolids on agricultural fields generally serves two main purposes: first, it
provides essential nutrients to crops; and second, it serves as a means of waste disposal for wastewater
treatments plants. Biosolids supplies phosphorus (P) to the soil (Kingery et al. 1993; Evers 1998), and
contributes to increased yields of forage and field crops where P was previously limiting production
(Brink et al 2002; Cooperband et al. 2002; Balkcom et al. 2003). However, when land application is
aimed primarily at supplying nitrogen (N) to crops and/or reducing the waste volume, P applied with
biosolids can far exceed the amount of P required by most crops (Eghball et al. 1999). For example, a
typical N:P uptake ratio for corn is 7.5:1 (U.S. EPA 1981), while the N:P ratio for biosolids reported in

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the literature tends to be approximately 2.5:1 (Edwards & Daniel 1992). Initially soils will retain most
of the P applied in excess of crop uptake through various transformation processes including
immobilization, adsorption, and precipitation. Apart from plant uptake, P can be lost by surface erosion
(Pionke et al. 2000; Smith et al. 2001) and/or subsequently by leaching (McDowell et al. 2004). Such
losses have resulted in eutrophication of rivers and lakes in the past decades (Daniel et al. 1998;
Sharpley et al. 2001). Adsorptions to surfaces of iron (Fe) and aluminum (Al) oxides and clay minerals
and precipitation as secondary Fe and Al P minerals are predominant reactions for solution P in acidic
soils and as Ca P minerals in alkaline soils. Alum [Al2(SO4)3⋅18H2O] is commonly used at municipal
drinking water treatment plants for water purification. It is added at the head of the water treatment
process to remove fine particulates and, therefore, reduce water turbidity. Alum serves as a coagulant
and forms particulate complexes that are then settled out and removed along with lime sludge, termed
as water treatment residues (WTRs). These WTRs commonly contain high levels of aluminum (Al),
calcium (Ca), iron (Fe) and other major cations that have potential for reacting with P to form water-
insoluble phosphate compounds and reduce the bioavailability of P in agricultural soils (Basta et al.
2000). For example, O’Connor & Elliott (2002) indicated that the addition of WTRs had dramatically
reduced soluble P in soil leachates. Staats et al. (2004) further reported that the use of alum as a poultry
litter amendment effectively reduced soluble P in the poultry litter. As a result, one may suggest that the
co-application of WTRs and biosolids promote agricultural land use of biosolids (Elliot et al. 2002).
There is, however, a limited amount of information on potential chemical interaction between P in
biosolids and major cations in WTRs, particularly regarding P speciation and temporal dynamics in the
mixture of biosolids and WTRs. Furthermore, chemical processes for the co-precipitation and
chemical-physical processes for adsorption of P with amorphous Al- and Fe-hydrous oxides or other
minerals, which are major components in biosolids and/or WTRS, needs to be elucidated. P speciation
in soils amended with biosolids and drinking water treatment residuals(WTRs) is essential in providing
information to formulate best management practices(BMPs) to mitigate surface water degradation
through eutrophication ( Beauchemin et al. 2003; Shober et al. 2006; Ajiboye & Akinremi 2007).
Different P species have very different physiochemical properties, which can determine their relative
tendency to precipitate, adsorb, or dissolve in soil solution. Shober et a. (2006) conducted P speciation
analysis on biosolids that had been treated with Al2(SO4)3 or FeCl3 compounds that are commonly used
in drinking water treatment. Their study showed a reduced solubility of P in biosolids that were treated
with the chemicals. Other P-speciation studies using biosolids and animal manures have elucidated
consistent results regarding chemical forms of P (Beauchemin et al. 2003; Ajiboye et al. 2007). These
previous studies determined that the dominant P species were calcium phosphate species such as
hydroxyapatite (calcium phosphate or HAP) and amorphous Al- and Fe- P species (Beauchemin et al.
2003; Shober et al. 2006; Ajiboye et al. 2007). All of the P species are precipitated minerals (or not
surface adsorbed) and thus are not subject to a Pmax adsorption value. It was observed by Beauchemin
et al. (2003) that HAP was the most dominant species at all pH levels observed, but especially
dominant at lower pH values. Because of the thermodynamic stability of HAP, it can be a major sink
for P in a non labile state. When compared to manures, HAP is more dominant in biosolids and the
water soluble P concentration was higher in extractions of manures than biosolids (Ajiboye et al. 2007).
It has been suggested that the lower P lability and higher HAP dominance in biosolids result from the
lime stabilization often used for treatment before land application (Ajiboye et al. 2007).
X-ray absorption near-edge structure (XANES) spectroscopy (a non-destructive chemical-speciation
technique) is a useful technique available for determining the speciation of P in various environmental
samples (Khare et al. 2005; Sato et al. 2005; Pickering et al. 1995). Because of the non-destructive
nature of this technique, XANES analysis directly identifies the chemical species present without
significant chemical modification. Each chemical species has a characteristic emission spectrum.
Known standards are analyzed and then a curve fitting technique is applied to determine P species
present in unknown samples. The objective of this study was: to assess the P species formed in an
originally neutral and alkaline soil in response to high biosolids and/or WTRs applications using P K-
edge x-ray absorption near edge structure (XANES) spectroscopy.
2. Materials and Methods

2.1 Sample Collection and Preparation
Three Egyptian soil types were selected for this study: Kafr El-Dawar soil (Typic torrifluvent, from

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Elbohera Governorate, Egypt), El-Bostan soil (Typic torripsamment, from Elbohera Governorate,
Egypt), and Borg Al-Arab soil (Typic calciorthids, from Alexandria Governorate, Egypt). Soils were
collected from a depth of 0-15 cm at each sampling location. Air-dried soil samples were ground and
subsequently sieved (< 2 mm). The experimental dried biosolids were obtained from the General
Organization Sanitory (GOS) in Alexandria City (Station No 9), Egypt. The WTRs were collected from
the drinking water treatment plant in Kafr El-Dawar, Elbohera Governorate, Egypt. Both biosolids and
WTRs were air-dried and sieved (< 2 mm) prior to use (Makris & Harris 2005).The general physio-
chemical properties of the soils, biosolids, and WTRs are compiled in Table (1). Soil pH and electrical
conductivity (EC) were determined using the paste extract method (Richards 1954); WTR and biosolid
pH and EC were analyzed using 1:2.5 suspension (Richards 1954); Calcium carbonate content was
determined by calcimeter (Nelson 1982); Particle size distribution was measured according to the
hydrometer method (Day 1965); The organic matter content (OM) of the samples was determined by
dichromate oxidation method (Nelson & Sommers 1982); Cation exchange capacity (CEC) was
determined using 1 M NaOAC (Rhoades 1982). In addition, KCl-extractable Al was determined
colorimetrically using 8-hydroxy quinoline butyl acetate method (Bloom et al. 1978). The available
phosphorus was determined according to Olsen & Sommers (1982). The DTPA extractable heavy
metals was determined according to Lindsay & Norvell,(1978). Concentrations of total metals were
determined using ICP-MS according to Ure (1995). Field capacity (FC) was determined by the
pressure-plate method (Tan 1996).
The American soil was collected from an agricultural field in Liberty, Illinois located at 685872E,
44201764N zone 15s. The soil had not been amended with biosolids or animal manures for at least 25
years. Soils were analyzed for general properties according to Page et al. (1982) (Table 2).
Biosolids were collected from the Troy Municipal Wastewater Treatment Plant in Troy, Illinois in
February, 2005. The plant treats domestic sewage sludge for a community of approximately 10,000
residents with no input from major industry. The water content of the biosolids was 75%. The pH of the
biosolids was 11.9±0.2. Biosolids were stored indoors in plastic buckets.
Drinking water treatment residuals (WTRs) were collected from the Hartford Drinking Water
Treatment Facility in Hartford, Illinois in September, 2005. The facility has been in operation since
1971 serving a community of approximately 1,500 residents. The WTRs were turbulently released from
the water treatment process as liquid containing suspended solid particulates at a concentration of a few
percent. The WTRs were taken directly from holding tanks, where coagulated particulates and alum
and lime treatment are allowed to precipitate from water. Once WTRs were in buckets and tubs they
rapidly precipitated so the water could be decanted off. Water was removed at collection and for the
weeks following collection until the WTRs reached a moisture content of 100%. The pH of the WTRs
was 9.0±0. WTRs were stored indoors in plastic buckets. Moisture content for all experiments was
determined by weighing moist samples then oven drying and weighing dry samples.
Soils, biosolids, and WTRs were chemically characterized using inductively coupled plasma mass
spectroscopy (ICP-MS) to determine concentrations of different elements (Table 2). Samples were
oven-dried at 45ºC for 3 days and ground to a fine powder in an agate mortar and pestle. Ground
samples were digested using EPA method 3050B for sludges and soils.

2.2 Soils Incubation Experiments
In the Egyptian experiment, different application rates of WTRs (0, 1, 2, 3, and 4%, w/w, DW) and
biosolids (0, 1, 2 and 3%, w/w) were added to each soil by fixing one rate of biosolids and varying the
rate of WTRs. The experimental soil was thoroughly mixed with the biosolids and WTRs and then the
treated soil was transferred to a large plastic bin. The soils that were not treated with the biosolids and
WTRs were used as the control. Distilled water was added to obtain the desired soil field capacity (FC).
The treated soils were then transferred to polypropylene jars, and brought to the field capacity. The soil
moisture content in the treated soil was kept constantly at the field capacity level during the incubation
period by periodically weighing the jars and adding distilled water to compensate for the water loss
through evaporation. The jars were covered with perforated plastic film and incubated at 25 °C for 60
days. The experimental design was a split-split plot design, with four replicates of each treatment (240
jars). After the incubation period, soil samples were air-dried, crushed to pass a 2-mm sieve, and stored
till chemical analysis.

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In the American experiment, all samples of soil, biosolid and WTR were ground to a fine powder using
a ceramic mortar and pestle. After grinding, each of the three components (biosolids, WTRs, and soil)
was weighed appropriately to provide each of the following treatments: WTR rates (0, 20, 40, 80, and
160 g WTRs kg-1 soil). Each WTR treatment level was crossed with biosolid loading rates of (0, 25,
and 50g biosolid kg-1 soil). The experimental design used was a completely randomized design
repeated for each level of biosolids application. This design was chosen because the purpose of the
objective of the experiment was to determine the effects of WTRs. The mixtures were scaled to provide
a total of 50g of soil, biosolid, and WTRs combined. Sample mixtures were placed into plastic cups
and saturated with distilled water. The samples were placed randomly on a bench at room temperature
for a period of 30 days. After ten days of incubation all samples were re-saturated then re-saturated
again at 20 days. At 30 days the samples were removed from the plastic cups and laid on drying paper
to air dry for 3 days. After air drying was complete, all samples were ground in a ceramic mortar and
pestle then placed into plastic bags.

2.3 X-ray absorption near-edge structure (XANES) analysis
The XANES analysis was carried out at the Synchrotron Radiation Centre (SRC) at Stoughton,
Wisconsin. The biosolids and sample mixtures of biosolids and WTRs were attached in a thin layer
over double-sided conducting carbon tape, and the sample target was positioned at a 45-degree angle to
the X-ray beam. X-ray absorption spectra (near edge structure) were collected by monitoring the P K-
edge fluorescence using the double crystal monochromator (DCM) beam-line of the Canadian
Synchrotron Radiation Facility, having a 13-element Ge detector and cryostat for spectrum collection in
a series of replicate scans. The source electron energy ranged from 800 to 1000 MeV, with a current
ranging from approximately 120 to 250 mA. Additional information regarding the P calibration has
been reported in details previously by Lombi et al. (2006) and Ajiboye et al. (2007). The analysis of the
XANES spectra was performed using an edge-fitting method using SIXPack software as described by
Webb (2005). The normalized edge spectrum of a sample containing unknown P species was fitted to a
liner combination of the spectra of standard P compounds by using a least-squares minimization
procedure.

2.4 Phosphorus standards for XANES spectroscopy
Based on the principle components analysis (PCA) identification (Seiter et al. 2008), the following 14 P
standards were selected to fit potential P species present in the biosolids and WTRs samples: AlPO4
crystal, wet, amorphous AlPO4, P-sorbed on amorphous Al2(OH)3 , Ca3(PO4)3, Na3PO4.12H2O,
(NH4)MgPO4·xH2O, Phytic acid (corn) (H12IP6), CaH10P6 , Ca6IP6 , Na12IP6 , Phytic acid dodecasodium
(C6H17NaO24P6) , K4Mg2H4IP6 , K2H10IP6 , and Hydroxyapatite. SixPACK software (Webb 2005) was
used to average replicate spectra from each sample and fit the averaged spectra to those of standards.
The software calculated the percentage of each P standard in the sample using a least squares fit. The
PCA analysis eliminated insignificant P species leaving only those contributing a major component in
the sample.

3. Results and Discussion

3.1 Phosphorus Forms inBbiosolids and WTRs
The heterogeneity of the biosolids and WTRs samples provided a challenge for the interpretation of the
P-XANES spectra. However, several distinctive features could be identified on the spectra (Figure 1).
The combination of P standards yielding the best linear combination fits for biosolids were Ba6 with
phytic acid (26.03%) and Cu3 (PO4)2(73.09%) and a little of P-sorbed to Al hydroxide
(0.89%).However, The combination of P standards yielding the best linear combination fits for WTRs
were P-sorbed to Fe hydroxide (64.19%), phytic acid (30.72%) and P-sorbed to Al hydroxide (5.07%).
This is largely in consistent with the results reported by Shober et al (2006) and Daniel (2010).

3.2 Phosphorus Forms in Biosolids-Treated Soils

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The relative proportion of phosphate that best fit biosolids, WTRs, and selected WTRs-Biosolids-
treated soils XANES spectra in linear combination fitting are shown in Table (3).
The combination of P standards yielding the best linear combination fits for 10 g kg-1-treated Kafr El-
Dawar soils were phytic acid (Na salt)(19.08%), Mn3 (PO4)2(0.79%), KMgH9IP6(11.22%),
Cu3(PO4)2(7.26%),phytic acid(3.67%), and Hydroxyapatite(57.98%)(Table 3). Also, the best linear
combination fits for 10 g kg-1-treated El-Bostan soils were amorphous Fe-phosphate (47.02%),
KH2PO4(10.93%), Hydroxyapatite(17.21%), P-sorbed to Al hydroxide(16.13%), and Al Fe
PO4(8.70%).However, the P-XANES spectra of 10 g kg-1-treated Borg Al-Arab soils were
31.16%±0.02 Zn3 (PO4)2, 12.63%±0.01Al PO4, 3.10% ± 0.02 Cu3(PO4)2, 13.16%±0.02 Hydroxyapatite,
11.37%±0.02 Fe hydroxide with P-sorbed, 15.58% ± 0.03 CaH10P6, and 12.90%±0.03 H12 IP6(phytic
acid). In contrast, the increasing of biosolids application rates to 30 g kg-1 changed the percentage of
compounds presented in biosolids-treated soils (Table 3). The P-XANES spectra of 30 g kg-1-treated
Kafr El-Dawar soils were 15.34% ± 0.02 amorphous Al-phosphate, 29.53% ± 0.01 Al PO4, 39.67% ±
0.02 CaH10P6, and15.46%±0.02 H12 IP6 .While, in El-Bostan soils treated with 30 g kg-1 biosolids
application rate, the best linear combination fits were 14.84%±0.005 Al PO4, 19.51%±0.03 CaH10P6,
and65.64% ± 0.02 H12 IP6(phytic acid). Also, the forms in Borg Al-Arab soils were 32.27%±0.02
amorphous Al-phosphate, 21.39% ± 0.01 Al PO4, 17.61% ± 0.01 Hydroxyapatite, 21.01%±0.02
Ammonium magnesium phosphate, 1.62% ± 0.01 K4Mg2H4IP6 , and 6.07% ± 0.01 Al Fe PO4. Similarly,
the P-speciation of USA biosolids used in this study was similar. The combination of P standards
yielding the best linear combination fits for USA 50 g kg-1biosolids-treated soil were 13.50% ± 0.06 K
Mg Hg IP6, 47.50% ± 0.02 Fe hydroxide with P-sorbed, and 38.80% ± 0.04 H12IP6(Table 3). Spectrum
of the other treatments was discarded from the result because of its strong spectral noise and
unreliability. These results coincide with the results of Shober et al (2006) and Daniel (2010),but
different results were found in the study of Sato et al.(2005). This may suggest that certain forms of P
were present in the biosolids-treated soil that was not adequately represented by the standards used for
fitting. A greater variety of P standards may need to be considered in future work.

3.3 Phosphorus Forms in WTRs-Biosolids-Treated Soils
Addition of WTRs modified the P speciation in biosolids-amended soils, and the changes varied
depending on the specific P speciation and biosolids and WTRs application rates (Figs.2 and 3,Table 3).
In 10 g.kg-1 biosolids-amended Kafr El-Dawar soil, addition of 10 g.kg-1 WTRs significantly changed
the P speciation and the best linear combination fits were 83.82% ± 0.01 Al hydroxide with P-sorbed
and 16.19% ± 0.01 Al Fe PO4 ,so proportion of phosphate sorbed to Al hydroxide increased after WTRs
application. However, for El-Bostan soil, the P speciation were 45.36%±0.02 Al PO4, 51.17%±0.01 H12
IP6, and 3.45%±0.02 Al Fe PO4.While, the P speciation in Borg Al-Arab soil were 5.39%±0.01 Al Fe
PO4, 45.36%±0.02 Al PO4, 51.17%±0.01 H12 IP6, and 3.45%±0.02 Al Fe PO4. While one may assume
that portion of total P in biosolids that was fitted as Al-hydroxide-bound P can actually be the sum of
weakly sorbed P and soluble hydrated salts (e.g., K or Na phosphate), as differences in the XANES
spectral features of aqueous P standards and PO4 sorbed to Al hydroxides were subtle (Peak et al.,
2002), it is also possible that PO4 sorbed to Al hydroxide becomes more and more in-reversible with
the progress of P absorption that occurs by penetrating from outer layer to the inner layer of the subject
granular. Thus, potentials for loss of P to water resource can be reduced. Increasing application rate of
WTRs to 40 g.kg-1 did not change P speciation in Kafr El-Dawar and El-Bostan soils(Table 3), but the
proportion of forms was changed. On the contrary, P speciation in Borg Al-Arab soil were changed and
the best linear combination fits were 23.62%±0.05 Al PO4, 46.37%±0.02 Hydroxyapatite, 26.81%±0.0
H12 IP6, and 3.18%±0.04 Fe hydroxide with P-sorbed.The Hydroxyapatite form was predominant in
Borg Al-Arab soil because it has a high content of calcium carbonate. Mechanisms of appearance of
CaP compounds in the soil upon manure application include (i) formation of secondary CaP minerals;
(ii) phosphate adsorption to the surface of CaCO3 (Peak et al., 2002); and/or (iii) surface precipitates of
phosphate with adsorbed calcium on Fe-oxide surface. In soils amended with high rate of biosolids(30
g.kg-1), application of 10 g.kg-1 WTRs significantly changed the P speciation and proportion of forms
found.For example, the P speciation in Kafr El-Dawar soil were 14.27%±0.02 Ca3 (PO4)2,
71.49%±0.02 Hydroxyapatite, and 14.23%±0.004 Al Fe PO4.while, the best linear combination fits
were 18.86%±0.05 Ca3 (PO4)2, 47.23%±0.04 Hydroxyapatite, 5.35%±0.03 CaH10P6, and 28.55%±0.02
H12 IP6 in El-Bostan soils(Table 3). However, the forms in Borg Al-Arab soil were 24.95%±0.01 Al

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PO4, and75.04%±0.01H12 IP6. Additionally, increasing WTRs application rate up to 40 g.kg-1
significantly increased the proportion of Al hydroxide with P-sorbed(61.13%±0.02) in Kafr El-Dawar
soil and the other forms of P were 38.91%±0.02 Cd6IP6.However, the proportion of Al hydroxide with
P-sorbed (14.68%±0.02) was lower in El-Bostan soil than that of Kafr El-Dawar soil. Also, the other P
forms were 3.40%±0.02 Cu3(PO4)2, 49.16%±0.02 Hydroxyapatite, and 32.74%±0.02 Al Fe PO4.While,
the P speciation in Borg Al-Arab soil were completely different at the high rate of WTRs, the best
linear combination fits were 38.96%±0.02 Ba6IP6, 46.26%±0.01 Cu3(PO4)2, and 14.79%±0.03
Cd6IP6(Fig.2 and Table 3).In comparison, in the 50 gkg-1biosolids-treated Troy soil, application of 40
gkg-1 DWTRs have changed the P speciation in soil in comparison with control soil(Fig.3 and Table 3).
The best linear combination fits were 76.67%±0.05 Ba6IP6, and 23.33%±0.01 Cu3(PO4)2 .Other studies
have different results on P speciation, for examples the study of Beachemin et al.,(2003) revealed that
the XANES results indicated that phosphate adsorbed on Fe- or Al-oxide minerals was present in all
soils, with a higher proportion in acidic than in slightly alkaline samples. Calcium phosphate also
occurred in all soils, regardless of pH. In agreement with chemical fractionation results, XANES data
showed that Ca-phosphate was the dominant P forms in one acidic (pH 5.5) and in the two slightly
alkaline (pH 7.4-7.6) soil samples. X-ray absorption near edge structure spectroscopy directly
identified certain forms of soil P, while chemical fractionation provided indirect supporting data and
gave insight on additional forms of P such as organic pools that were not accounted for by the XANES
analysis. Gungr et al.. (2007) studied the P speciation in raw and anaerobically digested dairy manure
with an emphasis on the Ca and Mg phosphate phases. Qualitative analysis of P by XANES spectra
indicated that the Ca orthophosphate phases, except dicalcium phosphate anhydrous (DCPA) or
monetite(CaHPO4), were not abundant in dairy manure. Linear combination fitting (LCF) of the P
standard compounds showed that 57 and 43 % of P was associated with DCPA and struvite,
respectively, in the raw manure. In anaerobically digested sample, 78.2% of P was present as struvite
and 21.8% of P was associated with Hydroxyapatite (Hap).the P speciation shifted toward Mg
orthophosphates and least soluble Ca orthophosphates following anaerobic digestion. Similarity
between the aqueous orthophosphate, newberyite (MgHPO4.3H2O), and struvite spectra can cause
inaccurate P speciation determination when dairy manure is analyzed solely using P XANES
spectroscopy; however, XANES can be used in conjunction with XRD to quantify the distribution of
inorganic P species in animal manure. Sato et al.,(2005) reported that P XANES spectra of poultry
manure showed no evidences of crystalline P minerals but dominance of soluble CaP species and free
and weakly bound phosphates(aquoues phosphate and phosphate adsorbed on soil minerals).Phosphate
in unamended neighboring forest soil(pH 4.3) was mainly associated with iron compounds such as
strengite and Fe-oxides. Soils with a short-term manure history contained both Fe-associated
phosphates and soluble CaP species such as dibasic calcium phosphate (DCP) and amorphous calcium
phosphate (ACP). Long term manure application resulted in a dominance of CaP forms, however, none
of the manure-amended soils showed the presence of crystalline CaP. Seiter et al.(2008) studied the P
speciation in alum-amended poultry litter, and the results indicated that traditional sequential
fractionation procedures may not account for variability in P speciation in heterogeneous animal
manures. XANES analysis showed that P is present in inorganic (P sorbed on Al oxides, calcium
phosphates) and organic forms (phytic acid, polyphosphates, and monoesters) in alum- and non-alum-
amended poultry litter.

4. Conclusion
Revealing the complex nature of phosphate chemistry within environmental samples is an analytical
challenge requiring new techniques and analytical approaches. Studies using sequential chemical
extractions and nuclear magnetic resonance techniques have provided a wealth of information on bulk
scale biosolids phosphorus composition. Speciation provides valuable information about the fate P may
take in the soil and water environment. Phosphorous compounds found in biosolids were
predominately the PO4 sorbed to Al hydroxide, followed by β-tricalcium phosphate, hydroxyapatite,
and phytic acid. The addition of WTRs increased the proportion of PO4 sorbed to Al hydroxide and
increased the proportion of aluminum phosphate. Addition of WTRs modified the P speciation in
biosolids-amended soils, and the changes varied depending on the specific P speciation and biosolids
and WTRs application rates. The P speciation in 4.

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5.Aknolowdgement
The authors are grateful to the Synchrotron Radiation Center (SRC) for the beamtime award (to Zhang
and Lin) with the Canadian Synchrotron Radiation Facility (CSRF). SRC is financially supported by
the National Science Foundation (DMR-0084402), and CSRF is supported by National Research
Council and NSERC (MFA) of Canada

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Table 1.Some physical and chemical characteristics of studied soils, WTRs and biosolids in Egypt
Characteristics Units Kafr El- El-Bostan Borg Al- WTRs Biosolids
Dawar Arab
pH 8.13 ± 0.05a) 7.69 ± 0.05 8.08 ± 0.06 7.45 ± 0.06 6.69 ± 0.03
-1
EC dSm 2.66 ± 0.11 3.84 ± 0.12 2.92 ± 0.06 1.67 ± 0.04 11.25 ± 0.12
CaCO3 g kg-1 57.90 ± 0.60 2.40 ± 0.30 356.80 ± nd c) nd
2.60
Sand g kg-1 596.4 ± 4.20 868.2 ± 5.10 740.00 ± nd nd
3.70
Silt g kg-1 141.3 ± 1.50 25.10 ± 0.30 101.50 ± nd nd
1.90
Clay g kg-1 262.30 ± 3.70 106.70 ± 158.50 ± nd nd
2.20 3.20
Texture S.C.L L.S S.L nd nd
O.M b) g kg-1 8.50 ± 0.15 1.00 ± 0.04 4.60 ± 0.15 57.00 ± 450.00 ±
2.00 1.67
KCl-Al mg kg-1 1.03 ± 0.04 0.13 ± 0.02 0.08 ± 0.02 28.18 ± 4.22 ± 0.13
1.03
Olsen-P mg kg-1 24.75 ± 0.25 2.89 ± 0.14 18.70 ± 0.80 24.00 ± 48.60 ± 1.62
2.00
CEC Cmol(+)kg- 39.13 ± 0.98 8.70 ± 0.20 26.00 ± 2.02 34.78 ± 73.57 ± 0.51
1
0.34
Total Elements:
N g kg-1 nd nd nd 4.20 ± 0.13 32.00 ± 1.56
P g kg-1 nd nd nd 1.90 ± 0.15 4.60 ± 0.12
K g kg-1 nd nd nd 2.20 ± 0.21 1.90 ± 0.08
Al g kg-1 nd nd nd 38.01 ± 3.10 ± 0.23
0.93
Ni mg kg-1 25.01 ± 0.02 14.00 ± 0.11 17.02 ± 0.03 9.40 ± 0.07 108.00 ±
1.01
Pb mg kg-1 35.08 ± 0.17 14.00 ± 0.11 62.20 ± 0.35 76.00 ± 143.00 ±
0.17 0.64
Cu mg kg-1 30.22 ± 0.79 43.21 ± 0.22 24.06 ± 0.07 49.00 ± 128.00 ±
0.02 0.44
Cd mg kg-1 3.30 ± 0.18 2.10 ± 0.11 4.50 ± 0.03 3.00 ± 0.02 4.00 ± 0.15
DTPA-Extractable
Metals:
Ni mg kg-1 8.92 ± 0.04 5.13 ± 0.05 7.17 ± 0.05 2.49 ± 0.07 12.12 ± 0.24
Pb mg kg-1 6.13 ± 0.02 2.18 ± 0.08 5.69 ± 0.12 1.58 ± 0.04 62.13 ± 0.22
Cu mg kg-1 9.09 ± 0.03 3.13 ± 0.05 4.98 ± 0.03 1.20 ± 0.1 11.83 ± 0.15
Cd mg kg-1 0.33 ± 0.02 0.18 ± 0.02 0.26 ± 0.04 0.09 ± 0.02 0.72 ± 0.04
a)
Means of three samples ± SD.
b)
O.M: organic matter; S.C.L: sandy clay loam, L.S: loamy sand, S.L: sandy loam
c)
nd: not determined

Table 2. General properties of the experimental biosolids, WTRs, and soils in Illinois, USA. Values are
means ± standard deviation (n = 3)
Characteristics Units WTRs Biosolids Soil

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pH 9.00±0.05 11.9±0.2 6.27±0.12
-1
EC dSm 1.88±0.05 6.15±0.11 1.05±0.07
Texture nd nd Silty loam
-1
O.M g kg 67.6±0.5 380.2±3.2 20.3±0.6
-1
Available-N mg kg 19.06±1.56 78.09±1.05 23.34±0.59
-1
KCl-Al mg kg 125.07±4.5 34.67±0.58 75.23±1.52
-1
Available-P mg kg 17.12±0.54 53.99±2.51 26.00±4.00
-1
CEC cmol(+)kg 43.12±5.54 76.00±3.5 10.53±0.06
ICP-MS analysis:
-1
Aluminum (Al) g kg 12.6±0.05 71.9±0.7 71.0±0.47
-1
Sodium (Na) g kg 0.5±0.02 1.5±0.02 <0.001
-1
Iron (Fe) g kg 121.0±4.0 82.3±2.9 123.2±4.9
-1
Potassium (K) g kg 0.5±0.01 30.7±0.8 10.6±0.6
-1
Magnesium (Mg) g kg 12.6±0.5 3.6±0.3 1.5±0.02
-1
Silver (Ag) mg kg <0.002 2.00±0.12 <0.002
-1
Arsenic (As) mg kg <0.1 11.51±0.26 3.80±0.19
-1
Boron (B) mg kg 12.30±0.58 109.07±5.06 6.55±1.05
-1
Calcium (Ca) mg kg 266.07±2.28 309.34±11.28 1.61±0.06
-1
Cadmium (Cd) mg kg 0.05±0.00 1.57±0.06 0.37±0.03
-1
Cobalt (Co) mg kg 0.44±0.04 3.00±0.02 7.53±0.37
-1
Chromium (Cr) mg kg 3.83±0.08 23.72±0.69 12.82±0.59
-1
Copper (Cu) mg kg 0.86±0.10 342.07±6.70 11.34±0.60
-1
Manganese (Mn) mg kg 7021.85±279.71 3321.74±63.71 7822.82±444.63
-1
Molybdenum (Mo) mg kg 0.03±0.04 4.60±0.18 0.45±0.07
-1
Nickel (Ni) mg kg 7.75±0.71 30.15±0.59 13.50±0.55
-1
Lead (Pb) mg kg 0.05±0.00 29.16±0.32 20.30±0.54
-1
Zinc (Zn) mg kg 10.95±0.85 190.86±0.83 64.19±2.15

Table 3.Relative proportion of phosphate that best fit biosolids, WTRs, and selected WTRs-Biosolids-
treated soils XANES spectra in linear combination fittinga.

Soil
Treatments WTRs Biosolids
Kafr El-Dawar El-Bostan Borg Al-Arab USA-soil
5.07%±0.05
Al hydroxide
26.03%±0.01
with P-
Ba6IP6
sorbed

64.19%±0.07
Fe hydroxide 73.09%±0.03
with P- Cu3(PO4)2
sorbed
0.89%± 0.02
Al hydroxide
30.72%±0.02
with P-
H12IP6
sorbed

47.02%±0.05
19.08%±0.02 31.16%±0.02 Zn3
amorphous Fe-
Na12 I P6 (PO4)2
phosphate
10 0.79%±0.02 10.93%±0.01 12.63%±0.01
Biosolids(B) Mn3 (PO4)2 KH2PO4 Al PO4
17.21%±0.01
11.22%±0.04 3.10%±0.02
Hydroxyapatite
KMgH9IP6 Cu3(PO4)2

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16.13%±0.01
7.26%±0.01 Al hydroxide 13.16%±0.02
Cu3(PO4)2 with P-sorbed Hydroxyapatite

11.37%±0.02
57.98%±0.01 8.70%±0.04 Al
Fe hydroxide with
Hydroxyapatite Fe PO4
P-sorbed
3.67%±0.03 15.58%±0.03
H12 IP6 CaH10P6
12.90%±0.03
H12 IP6
83.82%±0.01
45.36%±0.02 79.74%±0.01
Al hydroxide
Al PO4 Al PO4
with P-sorbed
4.12%±0.01
16.19%±0.01 51.17%±0.01
Al hydroxide with
Al Fe PO4 H12 IP6
10B+10WTRs P-sorbed
10.74%±0.01
3.45%±0.02
Fe hydroxide with
Al Fe PO4
P-sorbed
5.39%±0.01
Al Fe PO4
76.45%±0.01 8.65%±0.02 23.62%±0.05
Al PO4 Al PO4 Al PO4
23.53%±0.01 58.72%±0.01 46.37%±0.02
H12 IP6 H12 IP6 Hydroxyapatite
10B+40WTRs 3.18%±0.04
32.62%±0.02
Fe hydroxide with
Al Fe PO4
P-sorbed
26.81%±0.0
H12 IP6
15.34%±0.02
32.27%±0.02
amorphous Al- 14.84%±0.005
amorphous Al-
phosphate Al PO4
phosphate

29.53%±0.01 19.51%±0.03 21.39%±0.01
Al PO4 CaH10P6 Al PO4
39.67%±0.02 65.64%±0.02 17.61%±0.01
30B CaH10P6 H12 IP6 Hydroxyapatite
21.01%±0.02
15.46%±0.02
Amm.magnesium
H12 IP6
phosphate
1.62%±0.01
K4Mg2H4IP6
6.07%±0.01
Al Fe PO4
14.27%±0.02 18.86%±0.05 24.95%±0.01
Ca3 (PO4)2 Ca3 (PO4)2 Al PO4
71.49%±0.02 47.23%±0.04 75.04%±0.01
Hydroxyapatite Hydroxyapatite H12 IP6
30B+10WTRs
14.23%±0.004 5.35%±0.03
Al Fe PO4 CaH10P6
28.55%±0.02
H12 IP6
30B+40WTRs 61.13%±0.02 3.40%±0.02 38.96%±0.02

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Al hydroxide Cu3(PO4)2 Ba6IP6
with P-sorbed
38.91%±0.02 49.16%±0.02 46.26%±0.01
Cd6 IP6 Hydroxyapatite Cu3(PO4)2
14.68%±0.02
14.79%±0.03
Al hydroxide
Cd6IP6
with P-sorbed
32.74%±0.02
Al Fe PO4
13.50%±0.06
K Mg Hg IP6
47.50%± 0.02
50B Fe hydroxide
with P-sorbed
38.80% ±0.04
H12IP6
76.67% ±0.05
Ba6IP6
50B+40WTRs
23.33% ±0.10
Cu3(PO4)2
a
Percentage after normalization to sum= 100 ± standard errors for the linear coefficients.

Biosolids
6
Al hydroxide with P-sorbed
Cu3(PO4)2
Data
5 Ba6IP6
Fit
Normalized Absorption

4

3

2

1

0

2140 2160 2180 2200 2220

Energy (eV)

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DWTR
5
H12 IP6
Fe hydroxide with P-sorbed
Data
4
Fit

3

2

1

0

2140 2160 2180 2200 2220

Energy (eV)
Figure 1. Phosphorus K-edge XANES spectra for biosolids and WTRs of Egypt.

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30 Biosolids + 40 DWTR-Borg Al-Arab soil
6
Cu3 (PO4)2
Cd6 I P6
5
Data
Ba6 I P6

Fit
4

3

2

1

0

2140 2160 2180 2200 2220

Energy(eV)
30 Biosolids+40 DWTR -Kafr El-Dawar soil
7
Cd6 IP6
6 Data
Fit

5

4

3

2

1

0

2140 2160 2180 2200 2220

Energy(eV)
30 Biosolids+40 DWTR- El-Bostan soil
5
Cu3 (PO4)2
Hydroxylapatite
4 Data
Al/Fe PO4

Fit

3

2

1

0

2140 2160 2180 2200 2220

Energy(eV)

Figure 2. Phosphorus K-edge XANES spectra for 30 g.kg-1 biosolids-treated Egyptian soils amended
with 40 g.kg-1 WTRs.

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50 Biosolids 50 biosolids + 40 DWTRs
4 8

Ca H10 hexaphosphate
H12 Z hexaphosphate Cu3(PO4)2
Fe hydroxide with P sorbed data
data B6 Inositol hexaphosphate
3 fit 6 fit

2 4

1
2

0
0

2140 2160 2180 2200 2220 2140 2160 2180 2200 2220

Energy (eV) Energy (eV)

Figure 3. Phosphorus K-edge XANES spectra for 50 g.kg-1bisolids and 50 g.kg-1bisolids and 40 g.kg-1
WTRs-treated Troy soils.

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Phosphorus speciation in drinking water treatment residuals

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