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Effects of pH, molar ratios and pre-treatment on phosphorus recovery through struvite crystallization from effluent of anaerobically digested swine wastewater

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Effects of pH, molar ratios and pre-treatment on phosphorus recovery through struvite crystallization from effluent of anaerobically digested swine wastewater

Abstract and Figures

Struvite precipitation has been proven to be an effective method in removing and recovering ammonia nitrogen (N) and phosphate phosphorus (P) from wastewater. In this study, effects of pH, molar ratios and pre-treatment of effluent of anaerobically digested swine wastewater were investigated to improve struvite crystallization. The magnesium : ammonium : phosphate ratio of 1.2 : 1.0 : 1.0 was found to be optimal, yet the molar ratio in the wastewater was 1 : 74.9 : 1.8. From the analysis, the optimum pH was between 8.0 and 9.0 for maximal phosphate P release and from 8.0 to 10.0 for maximal ammonia N and phosphate P removal from real wastewater. Analysis from Visual MINTEQ predicted the pH range of 7-11 for ammonia N and phosphate P removal and recovery as struvite. For pre-treatment, microwave pre-treatment was ineffective for phosphate P release but ultrasound pre-treatment showed up to 77.4% phosphate P release at 1,000 kJ/L of energy dose. Precipitates analysis showed that phosphorus and magnesium in the collected precipitate had almost same values as theoretical values, but the ammonia content was less than the theoretical value.
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1. Introduction
Recently livestock wastewater treatment and recycling in South
Korea have become a big issue as animal wastewater generation
has reached to about 46,000 Mm3/y. Also, the wastewater from
the pig farming industry poses serious social and economic prob-
lems due to the negative effect on the environment with respect
to treatment and recycling of swine wastewater [1-2]. The treatment
and recovery of nutrient from the waste stream is important, since
swine wastewater contains high concentrations of nitrogen and
phosphorus that cause eutrophication in water bodies. Recently,
the depletion of phosphorus resources has been a big issue, which
has been discussed on a global basis [3], although it is estimated
that 7,000 billion kg of phosphate rock still exists [2].
Phosphorus as well as nitrogen in swine wastewater after anaero-
bic digestion has been widely used as a liquid fertilizer in Korea.
However, the quick-release fertilizer application is a principal
source of nitrogen and phosphorus pollution in the farming field,
causing water pollution. Alternative methods, however, such as
crystallization and adsorption processes have been developed to
recover nutrients to high quality [4-6]. Among these techniques,
the crystallization process of the magnesium ammonium phosphate
(MAP, also known as struvite) is considered to be one of the better
techniques, as struvite crystallization is cost-effective and yields
high-quality nutrients, used as valuable slow-release fertilizers [7-9].
Struvite (MgNH4PO46H2O) is a crystalline substance consisting
of magnesium, ammonium, and phosphate ions in equal molar
concentrations. Struvite crystal is commonly formed as scale after
anaerobic digestion on pipe walls and reactor vessels. The chemical
equation for struvite crystal formation is as follows [10]:




(1)
Environ. Eng. Res. 2017; 22(1): 12-18
pISSN 1226-1025
https://doi.org/10.4491/eer.2016.037
eISSN 2005-968X
Effects of pH, molar ratios and pre-treatment on phosphorus
recovery through struvite crystallization from effluent of
anaerobically digested swine wastewater
Daegi Kim1, Kyung Jin Min2,3, Kwanyong Lee4, Min Sung Yu2, Ki Young Park2
1Institute for Advanced Engineering, Gyeonggi-do 17180, Republic of Korea
2Department of Civil and Environmental System Engineering, Konkuk University, Seoul 05029, Republic of Korea
3AinChemTech Co., Ltd and EPS Solution Co., Ltd, Gyunggi-do 05029, Republic of Korea
4Korea Institute of Civil Engineering and Building Technology, Gyeonggi-do 10223, Republic of Korea
ABSTRACT
Struvite precipitation has been proven to be an effective method in removing and recovering ammonia nitrogen (N) and phosphate phosphorus
(P) from wastewater. In this study, effects of pH, molar ratios and pre-treatment of effluent of anaerobically digested swine wastewater were
investigated to improve struvite crystallization. The magnesium : ammonium : phosphate ratio of 1.2 : 1.0 : 1.0 was found to be optimal, yet
the molar ratio in the wastewater was 1 : 74.9 : 1.8. From the analysis, the optimum pH was between 8.0 and 9.0 for maximal phosphate
P release and from 8.0 to 10.0 for maximal ammonia N and phosphate P removal from real wastewater. Analysis from Visual MINTEQ predicted
the pH range of 7-11 for ammonia N and phosphate P removal and recovery as struvite. For pre-treatment, microwave pre-treatment was
ineffective for phosphate P release but ultrasound pre-treatment showed up to 77.4% phosphate P release at 1,000 kJ/L of energy dose. Precipitates
analysis showed that phosphorus and magnesium in the collected precipitate had almost same values as theoretical values, but the ammonia
content was less than the theoretical value.
Keywords: Ammonia and phosphate recovery, Magnesium ammonium phosphate, Pre-treatment, Struvite, Ultrasonic treatment
This is an Open Access article distributed under the terms
of the Creative Commons Attribution Non-Commercial License
(http://creativecommons.org/licenses/by-nc/3.0/) which per-
mits unrestricted non-commercial use, distribution, and reproduction in any
medium, provided the original work is properly cited.
Copyright © 2017 Korean Society of Environmental Engineers
Received February 29, 2016 Accept ed September 6, 2016
Corresponding author
Email: kypark@konkuk.ac.kr
Tel: +82-2-450-3736 Fax: +82-2-450-3726
Environmental Engineering Research 22(1) 12-18
13
Struvite precipitation from wastewater is influenced by a large
number of parameters such as pH of the reaction, molar ratio,
interfering ions in the feed, reaction time, types of chemicals added,
types of the reactor used and temperature. From these, the reaction
pH and molar ratios of reactants, namely magnesium : ammonium
: phosphate molar ratios, are the main factors for struvite
precipitation.
The pH of the reaction plays a significant role during struvite
precipitation process, and not only affects the amount of struvite
precipitation, but also its purity. Increasing the pH and the reactant
concentration can reach solution saturation but increasing the
pH of the solution is more feasible and allows for more varied
applications [11]. Struvite can be precipitated at a wide pH range
(from 7.0 to 11.5), but the suitable pH range is from 8.0 to 9.5.
Struvite precipitation is a physico-chemical process that can occur
over a range of pH values bounded by the speciation of struvite
components so that the concentrations of magnesium, ammonium
and phosphate ions can be affected by the pH of the solution
[12]. A variety of magnesium and phosphate complex ions patterns
in the reactor solution, including MgOH+, Mg(OH)3-, MgH2PO4+,
MgHPO4, H3PO4, H2PO4-, HPO4-2, MgPO4- can be formed when
the pH of solution is varied [13].
The pH of the solution in the struvite precipitation reactor
influences struvite solubility. With increasing the pH, the struvite
solubility decreases, but the solubility begins to increase when
the pH rises above pH 9; this is because the ammonium ion concen-
tration decreases and the phosphate ion concentration increases
[12, 14]. As various factors such as reaction pH, ionic strength
and temperature affect struvite solubility, which in turn determines
the supersaturation ratio [15]. It is the excess supersaturation in
the liquid that is the major parameter in predicting struvite precip-
itation potential [16]; therefore, it is important to use chemical
equilibrium-based models to calculate and predict the practical
conditions for struvite formation. There is a geochemical equili-
brium speciation model MINTEQ that could be used to model
struvite formation [17]. For calculating metal speciation, solubility
equilibria, sorption, etc., for natural waters, visual MINTEQ is
available as a freeware chemical equilibrium model.
For the anaerobically digested effluent of swine wastewater
from livestock, there is generally less magnesium and phosphate
ions compared with ammonium ion. It is then necessary to add
a source of magnesium and phosphate ions to enhance the struvite
crystallization process. The concentration of phosphate ion is ex-
pected to increase through solubilization of total phosphorus. The
first step, thus, is to enable phosphate P release from solid phases
to increase the recovery of phosphorus by the struvite crystal-
lization process. The general methods to facilitate phosphate P
release are physical and chemical techniques [18-20]. Among these
techniques, alkaline-ultrasonic pre-treatment is preferred as it also
disintegrates the solid from swine wastewater and enhances the
anaerobic digestion process [21-22].
The objectives of this study were to investigate the effect of
pH and molar ratios for magnesium, ammonium, and phosphate
ions on ammonia N and phosphate P removal and recovery. Also
alkaline-ultrasonic pre-treatment was applied to the struvite crys-
tallization process to enhance nutrient recovery.
2. Materials and Methods
2.1. Materials
The anaerobically digested effluent of swine wastewater used
in the study was from the P-city swine wastewater treatment
plant in Korea. The effluent of swine wastewater was concentrated
at 4°C for 24 h and its main characteristics are shown in Table
1. Based on the initial composition of the effluent solution, magne-
sium and phosphate ions concentrations were very low, and
they needed to be increased to reach the desired molar ratios
for magnesium, ammonium, and phosphate ions. For both syn-
thetic and real wastewater, the concentrations of magnesium,
ammonium and phosphate ions were adjusted to the required
molar concentration using MgCl26H2O, NH4Cl and KH2PO4 sol-
utions, respectively. All reagents were of analytical grade. To
investigate the effect of reaction pH, 2 N HCl and 2 N NaOH
were used to adjust the pH, and the pH was monitored with
a pH meter. In addition, the pH influenced the phosphorus frac-
tions [22-23].
Table 1. Characteristics of the Effluent from the Anaerobically Digested
Swine Wastewater
Concentration
pH 8.17
T-N (mg/L) 2,350
NH3-N (mg/L) 1,775
T-P (mg/L) 612
PO4-P (mg/L) 221
2.2. Crystallizations Experiments
A lab-scale airlift reactor with a working volume of 5 L was used
for struvite crystallization. The schematic diagram of the ex-
perimental apparatus for struvite crystallization is shown in Fig.
1. The reactor operated with a 10 min hydraulic retention time
for the mixing zone and 3 h for the whole reactor. The obtained
struvite cake from the process was dried at room temperature
to form a powder.
Fig. 1. Experimental equipment for struvite crystallization.
D. Kim et al.
14
2.3. Pre-treatment for Phosphate P Release
Ultrasonic pre-treatment was performed for phosphate P release
with STH-750S ultrasound (Sonitopia, Korea) with operating fre-
quency of 20 kH and maximal power of 750 watt. Microwave
pre-treatment device had a microwave frequency of 2,450 MHz
with maximal power of 600 watt. During pre-treatment, the sup-
plied energy density ranged from 100 to 20,000 kJ/L. The energy
density of pre-treatment device can be defined with following
Eq. (2) (the energy density conditions of pre-treatment are shown
in Table 2):
  


 ×
(2)
where Power is in watt, t (time) in s, and V (sample volume)
in L.
Table 2. Energy Density Used in Pre-treatment
Energy density (kJ/L) Electricity (watt) Contact time (s)
100 33 300
200 67 300
500 167 300
1,000 333 300
2,000 667 300
5,000 750 667
10,000 750 1,334
20,000 750 2,667
2.4. Analysis and MINTEQ Model
The concentrations for total nitrogen (T-N), ammonia N, pre-treat-
ment for organic phosphate measurement were determined by
the following standard methods [24]. To study the release of phos-
phate ions concentration at different ultrasonic doses with ultra-
sonic disintegration, total phosphorus (T-P) and ortho-phosphate
P (PO43--P) levels in the effluent of the swine wastewater were
established by the Persulfate Digestion Method in HACH methods
10072. The phosphorous concentrations were determined by the
ascorbic acid method, using a UV-V is spectrophotometer at 800
nm (Smart Plus SP-1900PC, Woongki Science, Seoul, Korea). The
pH meter (Orionstar, Thermo Scientific, Waltham, MA, USA) was
calibrated after each experiment. The potential for struvite for-
mation as a function of pH was predicted by using chemical equili-
brium freeware Visual MINTEQ 3.0 developed by the U.S.
Environmental Protection Agency. Using the composition of the
anaerobically digested effluent of swine wastewater from P-city
as input, the model’s.
3. Results and Discussion
3.1. Effect of MAP Molar Ratios on Struvite Formation
In this research, the effects of Mg2+ : NH4+ : PO43- molar ratios
on struvite crystallization using synthetic swine anaerobic digester
wastewater were analyzed based on indications from previous
work [25-27]. At the start of the experiment, using a 0.1 NaOH
solution, the initial pH of the digester effluent sample was adjusted
to 9.0. Table 2 shows the effect of molar ratios on ammonia and
phosphate ions removal. Molar ratio of Mg2+ : NH4+ : PO43- for
the effective removal seemed to be 1.2 : 1.0 : 1.1.
Nelson et al. reported that adding magnesium ions did not
play an important role in phosphorus removal [11]. Therefore,
external addition of magnesium and phosphate should be con-
trolled to ensure the feasibility of struvite precipitation from
wastewater. Rahman et al. had a wide range of PO43- and Mg2+
ratios tested for struvite precipitation, but in most cases, the effec-
tive ratio was 1 : 1 or 1 : 1.2 [28]. Most research to date has
reported that the optimum molar ratio of Mg2+ : NH4+ : PO43-
for struvite precipitation is between 1.0 : 1.0 : 1.0 and 1.6 : 1.0 :
1.0 [28], although phosphate removal is not affected when Mg2+
: NH4+ : PO43- molar ratio is more than 1.3 : 1.0 : 1.0 at pH 9.0
in a full-scale plant [26].
There was a significant difference between ion removals in
real and synthetic effluents of swine wastewater anaerobic digester.
Ammonia N removal efficiency from synthetic wastewater was
over 90%, while real wastewater had lower than 50% ammonia
N removal. Addition of magnesium ion facilitated ammonia N
removal up to ratio of 1.2 and then it negatively influenced it.
However, more ammonia N was removed than would be predicted
based on the magnesium removal and the chemical formula for
struvite as shown in Fig. 2.
Table 3. Molar Ratios of Mg2+ : NH4+
: PO43- for Ammonia and Phosphate
Removal
NH4+Mg2+ PO43- NH4+ removal (%) PO43- Removal (%)
1.0
1
186.9 97.1
1.1 88.7 88.2
1.2 88.4 83.4
1.3 90.4 76.4
1.5 91.2 70.3
283.8 61.1
1.1
188.8 99.2
1.1 92.7 96.9
1.2 93.6 89.4
1.2
187.5 99.8
1.1 94.5 98.9
1.2 95.8 95.9
1.3
187.4 99.4
1.3 98.6 98.2
1.5 97.6 41.8
295.4 78.3
1.5
192.3 99.9
1.3 98.4 99.3
1.5 98.3 95.3
297.7 93.9
2
189.9 99.5
1.3 98.1 99.4
1.5 98.7 99.4
299.0 95.0
Environmental Engineering Research 22(1) 12-18
15
Fig. 2. Nitrogen and phosphorus removal according to PO43- : Mg2+
ratio for the effluent of swine wastewater anaerobic digester at pH 9.
Initial levels of magnesium, ammonium and phosphate ions
in the effluent of swine wastewater anaerobic digester were 32,
1,775, and 221 mg/L (molar ratio 1 : 74.9 : 1.8), respectively. The
ammonium ion concentration was much higher than magnesium
and phosphate ions concentrations. Therefore, magnesium and
phosphate ions sources had to be adjusted to completely remove
the ammonium ion. The experimental design allowed observing
the effects of magnesium and phosphate ions source dosage on
ammonia N and phosphate P removal as struvite. Experiments
were carried out with 10 min in the mixing zone and 3 h for
the whole reactor retention time and a pH of 9.0 according to
previous results.
The addition of magnesium and phosphate ions was required
to maximize ammonia recovery from the effluent of swine waste-
water anaerobic digester. The removal efficiency reached over
95%, and it was almost the same for the synthetic effluent.
Moreover, increasing added magnesium likely attributed to both
improvement of struvite precipitation and reduction of phosphate
P dose. Over dosing of magnesium could also contribute to de-
creased residual phosphorous concentration in the effluent and
phosphate recovery. However, if the concentration of magnesium
was increased up to a certain value, phosphorus removal would
not change [29].
Fig. 3. Addition of PO43- and Mg2+ to real wastewater for enhanced
recovery.
3.2. Effect of pH on Ammonia N and Phosphate P Removal
The ideal pH range for struvite precipitation could occur at a
wide pH range of 7.0 to 11.5. However, the suitable pH range
for struvite formation is 8 to 9.5 [30]; this is consistent with many
other reports [17, 29]. Interfering ions in solution also affect the
pH range for struvite precipitation and nutrient removal. To inves-
tigate the effect of pH on ammonia N and phosphate P removal
and recovery from the effluent of swine wastewater anaerobic
digester, the residual concentrations of ammonia N and phosphate
P were examined after each experiment. Removal of ammonia
N and phosphate P was calculated based on the change between
the initial concentration and the residual concentration.
Experiments were carried out under the same reactor conditions
at the pH range of 6.0 to 12.0 and an equal ratio (Mg2+ : NH4+ :
PO43- = 1.0 : 1.0 : 1.0).
Based on the batch experiment, the optimum pH for struvite
precipitation was investigated. Fig. 4 and Fig. 5 display the removal
efficiencies, depending on the pH, for ammonia N and phosphate
P in synthetic and real wastewaters, respectively. For synthetic
wastewater, as shown in Fig. 4, both ammonia N and phosphate
P removal efficiencies depended on the reaction pH, and the max-
imum ammonia N and phosphate P removal occurred at pH 9.0
and 11.0, respectively. For real wastewater, from Fig. 5, the optimal
Fig. 4. Ammonia N and P phosphate removal according to pH for
synthetic wastewater.
Fig. 5. Ammonia N and phosphate P removal according to pH for
real wastewater.
D. Kim et al.
16
range of phosphate P was reduced to between pH 8 and pH 10.
The maximum removal efficiency of phosphate P achieved were
over 95% in both wastewater types, while the maximum ammonia
N removal efficiency was very low in real wastewater due to the
high initial concentration of ammonia N. Thus, the pH of 8.0-10.0
can be considered as the optimum pH range for both ammonia
N and phosphate P removal from the effluent of swine wastewater
anaerobic digester.
Fig. 6 shows the optical microscope images of the struvite crystals
at various reaction pH values. This indicates larger struvite crystals
seen in higher pH values. Moreover, the increased size affected
struvite formation, and led to more precipitates forming at high
pH values. This could be explained in terms of more ammonia-based
precipitates forming compared to phosphate-based precipitates
at these conditions.
3.3. Pre-treatments Affecting Phosphate P Release
Acid-alkaline pre-treatments were applied for phosphate P release
from the effluent of swine wastewater anaerobic digester of P-city.
In this experiment, the initial pH was 7.2 and the pH was changed
with HCl and NaOH for the test pH range of 2.0-12.0. Acid-alkaline
pre-treatments were carried out under the same conditions so
that the ammonia N and phosphate P removals could be tested
in terms of the pH conditions of the wastewater. As shown in
Fig. 7, both T-P and phosphate P concentrations increased with
Fig. 7. Change of phosphorus concentration according to pH.
the increasing reaction pH, while poly-P concentration was slightly
decreased with the increasing pH. Fig. 8 shows the change of
phosphorus fraction according to pH. Maximum phosphate P re-
lease was observed at pH between 8.0-9.0.
In this work, the effect of ultrasonic and microwave pre-treat-
ment was also studied for changes in phosphate P release from
the effluent of swine wastewater anaerobic digester. The range
of the supplied energy density was from 100 kW/L to 20,000 kW/L.
From this analysis, phosphate P levels increased by increasing
ultrasonic energy density (up until 1,000 kJ/L); however, microwave
Fig. 8. Change of phosphorus fraction according to pH.
Fig. 9. Phosphate P release from swine wastewater according to energy
density.
a b c
Fig. 6. Struvite crystals (1000X); a) pH 8, b) pH 8.5, c) pH 9.
Environmental Engineering Research 22(1) 12-18
17
pre-treatment did not lead to any increases. At 1,000 kJ/L of energy
dose by using ultrasound, the highest phosphate P release (at
77.4%) was observed (Fig. 9).
3.4. Composition of Recovered Struvite
Precipitates from the anaerobically digested effluent of swine waste-
water collected from the experimental reactor were analyzed for
the composition of struvite. The contents of phosphorus and magne-
sium were similar to theoretical values but the ammonia content
was less than the theoretical value. This observed low ammonia
content could likely be attributed to precipitation of other minerals,
such as potassium struvite (KMgPO46H2O) instead of magnesium
ammonium phosphate due to introduction of potassium (KH2PO4)
for phosphate P supply.
For samples from the effluent of swine wastewater anaerobic
digester of P-city, Visual MINTEQ 3.0 was applied to concentrations
of Mg2+, NH4+ and PO43- at the pH range of 6.0 to 13.0 at 25˚C
to investigate the effect of pH on the amount and purity of struvite
formation from ammonia N and phosphate P removal in the
wastewater. Fig. 10 shows the levels and types of supersaturated
solids modeled by Visual MINTEQ. From the analysis, struvite
would be precipitated in the pH range 6.5 to 12.5, and as the
ion activity product (IAP) exceeded the minimum equilibrium
constant of solubility [31], struvite crystals would be formed in
the pH 7.5 to 10.5.
Table 4. Composition of Recovered Struvite
 Theoretical Sewage (Ueno and Fujii, 2001) This study
Mg2+ 9.9 9.7 9.9
NH4+7.3 7.3 4.1
PO43- 38.7 39.5 39.6
Fig. 10. Solids formation predicted at the pH range 6.0 to 13.0.
4. Conclusions
In this study, a wide range of molar ratios and pH values were
tested to determine optimum struvite recovery in terms of
efficiency. Microwave and ultrasonic pre-treatments were also in-
vestigated for phosphate P release from solid phases for increased
recovery of phosphorus from wastewater. From this analysis, the
optimum molar ratio of Mg2+ : NH4+ : PO43- for the effective removal
was 1.2 : 1.0 : 1.1. For real wastewater, the optimal pH range
of phosphate P was found to be between 8 and 10. The pH range
of 8 to 9 was found to lead to maximum phosphate P release
and could be the optimum condition for phosphorus recovery.
Ultrasound pre-treatment had the highest phosphate P release
of 77.4% at 1,000 kJ/L of energy dose but the microwave pre-treat-
ment had no effect under the tested conditions. Contents of phos-
phorus and magnesium in the collected precipitate were similar
to theoretical values but the ammonia content was less than the
predicted value. The modeling by Visual MINTEQ pointed to
struvite as the dominant solid phase in the pH range 7 to 11.
Acknowledgements
This study was supported by the Korea Ministry of the Environment
(MOE) as an “Eco-Innovation Project” (Project No. 2014-000015-
0017) and the Waste to Energy and Recycling Human Resource
Development Project funded by the Korea Ministry of the
Environment.
References
1. Seyhan D. Country-scale phosphorus balancing as a base for
resources conservation. Resour. Conserv. Recy. 2009;53:698-709.
2. Xu H, He P, Gu W, Wang G, Shao L. Recovery of phosphorus
as struvite from sewage sludge ash. J. Environ. Sci. 2012;24:
1533-1538.
3. United States Geological Survey (USGS). Phosphate rock, min-
eral commodity summaries. US Department of the Interior,
US Geological Survey, US Government Printing Office.
Washington D.C.: USA; 1997. p. 124-125.
4. Choi JW, Lee SY, Lee SH, et al. Comparison of surface-modified
adsorbents for phosphate removal in water. Water Air Soil Poll.
2012;223:2881-2890.
5. Jutidamrongphan W, Park KY, Dockko S, Choi JW, Lee SH.
High removal of phosphate from wastewater using silica sulfate.
Environ. Chem. Lett. 2012;10:21-28.
6. Choi JW, Lee KB, Park KY, Lee SY, Kim DJ, Lee SH. Comparison
between Ti- and Si-based mesostructures for the removal of
phosphorous from aqueous solution. Environ. Prog. Sustain.
Energy 2012;31:100-106.
7. Hu HQ, Li XY, Liu JF, Xu FL, Liu J, Liu F. The effect of direct
application of phosphate rock on increasing crop yield and
improving properties of red soil. Nutr. Cycl. Agroecosys.
1996:46:235-239.
8. Shu L, Schneider P, Jegatheesan V, Johnson J. An economic
evaluation of phosphorus recovery as struvite from digester
supernatant. Bioresour. Technol. 2006;97:2211-2216.
9. Wang X, Qiu Z, Lu S, Ying W. Characteristics of organic, nitro-
gen and phosphorus species released from ultrasonic treatment
of waste activated sludge. J. Hazard. Mater. 2010;176:35-40.
10. Huang H, Xu C, Zhang W. Removal of nutrients from piggery
wastewater using struvite precipitation and pyrogenation
technology. Bioresour. Technol. 2011;102:2523-2528.
11. Nelson NO, Mikkelsen RL, Hesterberg DL. Struvite precipitation
D. Kim et al.
18
in anaerobic swine lagoon liquid: effect of pH and Mg: P ratio
and determination of rate constant. Bioresour. Technol.
2003;89:229-236.
12. Snoeyink VL, Jenkins D. Water chemistry. New York: John
Wiley and Sons; 1980. p. 306-309.
13. Bouropoulos NC, Koutsoukos PG. Spontaneous precipitation
of struvite from aqueous solutions. J. Cryst. Growth 2000;213:
381-388.
14. Booker NA, Priestly AJ, Fraser IH. Struvite formation in waste-
water treatment plants: Opportunities for nutrient recovery.
Environ. Technol. 1999;20:777-782.
15. Hanhoun M, Montastruc L, Azzaro-Pantel C. Biscans B, Freche
M, Pibouleau L. Temperature impact assessment on struvite
solubility product: A thermodynamic modeling approach.
Chem. Eng. 2010;167:50-58.
16. Miles A, Ellis TG. Struvite precipitation potential for nutrient
recovery from anaerobically treated wastes. Water Sci. Technol.
2001;43:259-266.
17. Buchanan JR, Mote CR, Robinson RB. Thermodynamics of
struvite formation. T. ASAE. 1994;37:617-621.
18. Tao XUE, Xia H. Releasing characteristics of phosphorus and
other substances during thermal treatment of excess sludge.
J. Environ. Sci. 2010;19:1153-1158.
19. Yan Y, Feng L, Zhang C, Wisniewski C, Zhou Q. Ultrasonic
enhancement of waste activated sludge hydrolysis and volatile
fatty acids accumulation at pH 10.0. Water Res. 2010;44:
3329-3336.
20. Wei B, Li Y, Hu Y. Recovery of phosphorus and nitrogen from
alkaline hydrolysis supernatant of excess sludge by magnesium
ammonium phosphate. Bioresour. Technol. 2014;166:1-8.
21. Ahmad AA, Idris A. Release and recovery of phosphorus from
wastewater treatment sludge via struvite precipitation. Desalin.
Water Treat. 2014;52:5696-5703.
22. Kim M, Han DW, Kim DJ. Selective release of phosphorus
and nitrogen from waste activated sludge with combined ther-
mal and alkali treatment. Bioresour. Technol. 2015;190:522-528.
23. Xu Y, Hu H, Liu J, Luo J, Qian G, Wang A. pH dependent
phosphorus release from waste activated sludge: Contributions
of phosphorus speciation. Chem. Eng. J. 2015;267:260-265.
24. APHA, AWWA, WEF. Standard methods for the examination
of water and wastewater. 21st ed. Washington D.C.: American
Public Health Association; 2005.
25. Wang J, Burken JG, Zhang X, Surampalli R. Engineered struvite
precipitation: Impacts of component-ion molar ratios and pH.
J. Environ. Eng. 2005;131:1433-1440.
26.Ueno Y, Fujii M. Three years experience of operating and
selling recovered struvite from full-scale plant. Environ. Technol.
2001;22:1373-1381.
27. Lee JE, Rahman MM, Ra CS. Dose effects of Mg and PO4 sources
on the composting of swine manure. J. Hazard. Mater. 2009;169:
801-807.
28. Rahman MM, Liu YH, Kwag JH, Ra CS. Recovery of struvite
from animal wastewater and its nutrient leaching loss in soil.
J. Hazard. Mater. 2011;186:2026-2030.
29. Jaffer Y, Clark TA, Pearce P, Parsons SA. Potential phosphorus
recovery by struvite formation. Water Res. 2002;36:1834-1842.
30. Battistoni P, Deangalis A, Pavan P, Prisciandaro M, Cecchi
F. Phosphorus removal from a real anaerobic supernatant by
struvite crystallization. Water Res. 2001;35:2167-2178.
31. Celen I, Buchanan JR, Burns RT, Robinson RB, Raman DR.
Using chemical equilibrium model to predict amendments re-
quired to precipitate phosphorus as struvite in liquid swine
manure. Water Res. 2007;41:1689-1696.
... The magnesium/ammonium/phosphate ratios (Mg 2þ /NH 4 þ /PO 4 3À ) reported in fresh urine and anaerobically treated swine wastewaters are 1/79/5 and 1/74.9/1.8, respectively (Udert et al. 2003;Kim et al. 2017). However, Kim et al. (2017) reported that the optimum molar ratio of Mg 2þ /NH 4 þ /PO 4 3À to improve the recovery of phosphate as struvite from artificial swine wastewater is 1.2/1.0/1.0, in a pH range from 8 to 10. ...
... respectively (Udert et al. 2003;Kim et al. 2017). However, Kim et al. (2017) reported that the optimum molar ratio of Mg 2þ /NH 4 þ /PO 4 3À to improve the recovery of phosphate as struvite from artificial swine wastewater is 1.2/1.0/1.0, in a pH range from 8 to 10. It is well known that water quality of natural reservoirs has badly deteriorated because of disposal of raw or treated wastewater, leading to eutrophication processes. ...
... Therefore, this evidence confirms that the fine white powder recovered at the end of each batch was struvite. Also, it has been reported that struvite is the dominant solid phase in the pH range from 7 to 11, and struvite crystals would be formed around pH 7.5 to 10.5 (Kim et al. 2017). In this investigation the final pH was within these values (Table 4). ...
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The treatment of yellow water (human urine) in a downflow fluidised bed reactor (DFFBR) was investigated to evaluate biological ureolysis and nutrient recovery. The reactor was operated at 30±4 °C in batch mode, and reaction time = 1 d. The average immobilised biomass (as volatile solids, IVS) in the reactor was 2.5±0.9 g L−1support, and specific ureolytic activity was 121 g Urea-N g−1 IVS d−1. The kinetic parameters were 0.152 mol L−1 (Km) and 8 mol g−1 IVS d−1 (Vmax). The ureolysis efficiency was 93.4% and chemical oxygen demand removal efficiency was 31.2%, while total ammonium nitrogen (NH4+-N) production rate was 7 g L−1 d−1 and phosphate removal reached 26%. Precipitates recovery during biological treatment was 1.72±0.8 g. These results suggest that the treatment of yellow water in a DFFBR is a viable option for partial recovery of N and P. HIGHLIGHTS A new biological treatment of yellow water is proposed.; Yellow waters were treated effectively in a downflow fluidised bed reactor.; The biological ureolysis of human urine was reached within six hours.; After addition of Mg2+/PO43− (1.6/1), 82.3 g of precipitates were recovered.; Struvite was the major component of the recovered precipitates.;
... These wastewaters are commonly characterized by a low magnesium content compared to that of nutrients. Therefore, it is generally necessary to feed an external magnesium source to allow the nucleation and growth of struvite-type crystals [72,93,94]. ...
... Table S1: Results of MPP and MAP precipitation conducted on various wastes and using different reactors. References [14,15,17,23,26,27,[29][30][31][32]44,50,56,59,62,67,71,75,[89][90][91]94,95,[99][100][101] are cited in the supplementary materials. ...
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A.S.) † These authors contributed equally to this work. Abstract: The definition of technologies capable of removing and recovering nutrients from polluting effluents is a key environmental challenge. Through these technologies, it would be possible to protect aquatic systems and prevent the consumption of natural resources for the production of commercial fertilizers. In this regard, the application of the precipitation processes of struvite-type compounds is an attractive approach. Indeed, these processes are potentially able to remove nutrients from many effluents and produce a precipitate reusable as a slow-release fertilizer. The scientific community has largely focused on the precipitation of magnesium ammonium phosphate (MgNH4PO4·6H2O, MAP), while the recovery of the analogous magnesium potassium phosphate (MgKPO4·6H2O, MPP) has received extensive attention in the last decade. Research on this topic is continuously progressing to improve the precipitation process in different aspects (working conditions, reaction units, interference elimination, etc.). Until now, there has been no paper that comprehensively reviewed the applicability of MPP precipitation for the removal and recovery of nutrients from aqueous waste. To fill this gap, the present paper aimed to provide an exhaustive analysis of the literature reports on MPP processes to help researchers understand the theoretical and applicative aspects, the main problems, and the need for further research. In this regard, the applications in the treatment of various aqueous wastes were considered. The theoretical concepts, the main process parameters, and the effects of inhibiting substances and impurities are presented. Moreover, the development of reactor configurations and their working conditions are evaluated. Finally, the potential use of MPP as a fertilizer and some economic evaluations are reported. On the basis of the conducted analysis, it emerged that the recovery of MPP was mainly affected by the pH, dose, and nature of reagents, as well as the presence of competitive ions. The optimal pH values were reported to be between 9 and 11. Reagent overdoses with respect to the theoretical values improved the process and the use of pure reagents guaranteed superior performance. The stirred-tank reactors and fluidized bed reactors were the most used units with high process yields. The applicability of MPP in agronomic practices appears to be a suitable option.
... Struvite, also known as magnesium ammonium phosphate (MAP), is a white crystal compound that commonly accumulates in post anaerobic digestion pipes in wastewater treatment plants (WWTPs) [15,16]. MAP is considered a slow-release fertilizer [2,17,18], hence providing minimum run-off, enhanced settling and better nutrient uptake by crops [6]. ...
... Ryu et al. [41] considered the effluent from treating semiconductor wastewater, collected from Korea, a potential phosphorus and ammonia nitrogen source to recover struvite by adding magnesium chloride hexahydrate and maintaining a pH of 9. Approximately 89% of ammonia nitrogen was recovered through the process. Kim et al. [16] utilized magnesium chloride to recover struvite from swine wastewater treatment effluent using a 5L airlift reactor. The pH was maintained at 9 and several Mg:PO 4 −3 ratios were tested. ...
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Citation: Fattah, K.P.; Sinno, S.; Atabay, S.; Khan, Z.; Al-Dawood, Z.; Yasser, A.K.; Temam, R. Impact of Magnesium Sources for Phosphate Recovery and/or Removal from Waste. Energies 2022, 15, 4585.
... Comparing the MAP and MPP precipitation, both processes are strongly pH-dependent; pH value affects the amount of struvite precipitate, growth rate, sizes of Strategies toward Green Deal Implementation -Water, Raw Materials & Energy 8-10 December 2021 crystals, and their purity (Daegi et al. 2017). Struvite precipitation is usually performed at pH values higher than neutral, and at low pH, minimal crystals are obtained (Bayuseno et al. 2020). ...
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The Monograph “Strategies toward Green Deal Implementation – Water, Raw Materials & Energy” includes the selected papers that have been presented during the 2nd edition of International Conference on Strategies toward Green Deal Implementation – Water, Raw Materials & Energy.
... Domestic wastewater has total phosphorus (TP) in the range of 6.7-19.4 mg/L, fertilizer wastewater has TP concentration in (Gannoun et al., 2009;Ge et al., 2014;Matheyarasu et al., 2016) Textile wastewater ˂10 ˂10 ˂5 94 380.5 (Kumar et al., 2018;Yaseen and Scholz, 2018) Urine 0.5-2.7 680-900 -10-47 820-1250 (Nagy et al., 2019;Wei et al., 2018) Fertilizer industry Wastewater 0.9 19-50 11.3 1.8-3.5 23.9-50 (Gouider et al., 2011;Mbarka et al., 2010;Pham and Bui, 2020;Zhou et al., 2017 the range of 1.8-3.5 mg/L (Kumar et al., 2018;Pham and Bui, 2020), and swine wastewater has a high TP concentration of 612 mg/L (Kim et al., 2017). According to the table, urine wastewater has high total nitrogen (TN) concentration, which is in the range of 820-1250 mg/L (Nagy et al., 2019;Wei et al., 2018), and aquaculture wastewater has a low TN concentration of 5.8 mg/L (Andreotti et al., 2020;Lukwambe et al., 2018Lukwambe et al., , 2019. ...
Article
Phosphorus is an essential nutrient needed for agriculture and the agro-industry. Excess discharges in water bodies are the leading cause of eutrophication, and phosphorus deposits worldwide are rapidly depleting. Numerous studies have been conducted to recover phosphorus from wastewater. However, its assessment is still necessary and urgent. The purpose of this review is to give an in-depth investigation of alternative phosphorus restoration techniques. Hence, the EBPR combined with side-stream phosphorus removal had demonstrated a more significant contribution to phosphorus recovery in different forms. The procedure relies on phosphorus-accumulating organisms (PAO) richness in activated sludge to rack up many poly-phosphate within their cell interior and then recover in the side-stream. In addition, the effect of various operational parameters on side-stream phosphorus recovery efficiency and the performance of the mainstream system were detailed, including volatile fatty acids, hydraulic retention time, the amount of oxygen in aerobic conditions, nitrite, and temperature and pH condition. Ultimately, this review will help future research on phosphorus recovery to solve the severe issues of eutrophication and reduction of P resources.
Article
Utilization of the struvite recovered from sheep slaughterhouse wastewater was explored for the first time in sustainable cement production and fire-resistant wooden structure design. Sheep abattoir-originated struvite precipitation process was optimized using a chemical combination of MgCl2.6H2O + NaH2PO4.2H2O, a molar ratio of Mg²⁺:NH4⁺-N:PO4³⁻-P = 1.2:1:1, a reaction pH of 9.0, an initial ammonium concentration of 240 mg NH4⁺-N/L, and a reaction time of 15 min. Based on both American (ASTM C305-14) and Turkish (TS EN 196–1) standard methods, struvite was used in proportions of 10–30% by weight for struvite-substituted cement production. The best compressive strength values were achieved with 85.5% cement clinker (C), 4.5% gypsum (G), and 10% struvite (S) for the struvite-replaced cement (C85.5G4.5S10). According to the US EPA's greenhouse gas protocol, it was estimated that producing 10% struvite-substituted cement would result in 9.97% lower absolute CO2 emissions than producing 100% Portland cement. It was also found that slaughterhouse-derived struvite could compete with commercial water-based fire retardant solution and exhibit acceptable flame resistance behavior for wooden structures. The versatility of sheep abattoir-oriented struvite was confirmed as an environmentally sustainable and clean by-product for different structural uses.
Article
Ameliorative effects of sheep slaughterhouse waste-derived soil amendments (struvite, blood meal, bone meal) were explored and quantified by a series of comparative greenhouse trials. A scoring matrix system was developed for 25 different test plants using 300 agricultural measurements obtained for three basic growth parameters (fresh-dry plant weights and plant heights) and four different fertilizer sources including solid vermicompost. More than 70% of NH4+-N recovery from sheep slaughterhouse wastewater was achieved using a chemical combination of MgCl2.6H2O + NaH2PO4.2H2O, a molar ratio of Mg2+:NH4+-N:PO43-P = 1.2:1:1, a reaction pH of 9.0, an initial NH4+-N concentration of 240 mg/L, and a reaction time of 15 min. According to SEM micrographs, surface morphology of struvite exhibited a highly porous structure composed of irregularly shaped crystals of various sizes (11.34-79.38 μm). FTIR spectroscopy verified the active functional groups on the proximity of all fertilizer sources within the spectral range of 500-3900 cm-1. TGA-DTG-DSC thermograms of struvite revealed that the mass loss occurred in two temperature regions and reached a maximum mass loss rate of 1.63%/min at 317 °C. The average percentages of increase (57.55-100.62%) and performance points (69-79) corroborated that the fertility value of struvite ranked first on average in cultivation of the analyzed plant species. Findings of this agro-valorization study confirmed that sheep slaughterhouse waste-derived fertilizers could be a beneficial way to promote bio-waste management and environmentally friendly agriculture.
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Crystallization of vivianite is a sustainable way to recover phosphate from process water of kitchen waste hydrothermal carbonization (HTC). This study investigated impact of organic and inorganic impurities in HTC process water on vivianite crystallization and approaches to reduce their negative impact. Results showed that acetate, bovine serum albumin and humic acid reduced the phosphate removal and inhibited the vivianite crystallization. Ca and Mg triggered competing precipitations and reduced the vivianite purity while carbonate reduced the phosphate removal and the vivianite purity. In addition, negative effects of furfural and suspended solids on vivianite crystallization could be ignored. Increasing Fe(II)/P ratio rather than increasing pH minimized the negative effects of impurities on vivianite crystallization in real process water. The phosphate removal reached 98.2% when the Fe(II)/P ratio increased to 2 at pH 6. Therefore, it is technical-feasible to recover phosphate from HTC process water through vivianite crystallization.
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Background: The provision of safe sanitation services is essential for human well-being and environmental integrity, but it is often lacking in less developed communities with insufficient financial and technical resources. Hydrothermal carbonization (HTC) has been suggested as an alternative sanitation technology, producing value-added products from faecal waste. We evaluated the HTC technology for raw human waste treatment in terms of resource recovery. In addition, we constructed and tested a low-cost HTC reactor for its technical feasibility. Methods: Raw human faeces were hydrothermally treated in a mild severity range (≤ 200 °C and ≤ 1 hr). The total energy recovery was analysed from the energy input, higher heating value (HHV) of hydrochar and biomethane potential of process water. The nutrient contents were recovered through struvite precipitation employing process water and acid leachate from hydrochar ash. A bench-scale low-cost reactor (BLR) was developed using widely available materials and tested for human faeces treatment. Results: The hydrochar had HHVs (23.2 - 25.2 MJ/kg) comparable to bituminous coal. The calorific value of hydrochar accounted for more than 90% of the total energy recovery. Around 78% of phosphorus in feedstock was retained in hydrochar ash, while 15% was in process water. 72% of the initial phosphorus can be recovered as struvite when deficient Mg and NH 4 are supplemented. The experiments with BLR showed stable operation for faecal waste treatment with an energy efficiency comparable to a commercial reactor system. Conclusions: This research presents a proof of concept for the hydrothermal treatment of faecal waste as an alternative sanitation technology, by providing a quantitative evaluation of the resource recovery of energy and nutrients. The experiments with the BLR demonstrate the technical feasibility of the low-cost reactor and support its further development on a larger scale to reach practical implementation.
Article
Struvite is a phosphate mineral that can form hard-scale deposits in the recycle components of livestock waste management systems that utilize recycled lagoon effluent to transport waste. Previous research of struvite formation in piping systems has been hindered by the presence of erroneous solubility constant values in the literature and the use of a set of less-than-comprehensive equilibrium equations. This article identifies the erroneous solubility product constant commonly found in text books and documents an apparently correct value. Previous work using a set of simplified equilibrium equations indicated that the pH for minimum solubility of struvite is 10.7. For the study described herein, a more comprehensive set of equilibrium model, indicated that the pH of minimum solubility is approximately 9.0. Information derived from this study can aid in the development of management practices which will either prevent struvite formation or remove struvite from the system with controlled precipitation
Article
Selective release characteristics of phosphorus and nitrogen from waste activated sludge (WAS) were investigated during combined thermal and alkali treatment. Alkali (0.001-1.0N NaOH) treatment and combined thermal-alkali treatment were applied to WAS for releasing total P(T-P) and total nitrogen(T-N). Combined thermal-alkali treatment released 94%, 76%, and 49% of T-P, T-N, and COD, respectively. Release rate was positively associated with NaOH concentration, while temperature gave insignificant effect. The ratio of T-N and COD to T-P that released with alkali treatment ranged 0.74-0.80 and 0.39-0.50, respectively, while combined thermal-alkali treatment gave 0.60-0.90 and 0.20-0.60, respectively. Selective release of T-P and T-N was negatively associated with NaOH. High NaOH concentration created cavities on the surface of WAS, and these cavities accelerated the release rate, but reduced selectivity. Selective release of P and N from sludge has a beneficial effect on nutrient recovery with crystallization processes and it can also enhance methane production. Copyright © 2015 Elsevier Ltd. All rights reserved.
Article
For phosphorus (P) recovery from waste activated sludge (WAS), the most important step is to release P into the solution, which is greatly dependent on the pH of the solution. The contributions of different P speciation to P release amount from WAS as well as P release kinetics were investigated at different pHs, with the Standards Measurements and Testing (SMT) protocol being used for P fractions tests. The results showed that the total P in the solid (TP(s)) release percentages were 36.2% and 12.4% at pH = 2.0 and pH = 11.0, respectively. P speciation and fractions study made clear that the released P comes mainly from dissolving of inorganic P (IP) under acid condition, but from non-apatite inorganic P (NAIP) and organic P (OP) under alkaline condition. Simulation study using Visual MINTEQ indicated that the P release amount came from the experimental results is unanimous.
Article
The release and the recovery of phosphorus (P) from aerobically digested wastewater, sludge during thermal treatment and the solid–liquid separation by struvite precipitation were investigated. The effects of pH, temperature, and heating time on the liberated phosphate from solid phase to liquid phase were determined. After the wastewater treatment, sludge was thermally treated at a temperature over 100°C, no microbial activities were observed over a period of 24 h. The maximum total phosphorus release of 48.9 mg/L (93.6%) was observed at pH 2 ± 3, 170°C in 80 min. The results showed that the optimum pH values that released phosphate ions from the solid phase to the solution were noted at the range of 2–4. The scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX) indicated that struvite precipitation is unshaped and nonuniform crystal formed. The surface composition of the precipitates contains high amount of O, P, Mg, and trace of C, Cl. The Fourier transform infrared spectroscopy and X-ray diffraction analysis further indicated that the struvite is evidently the main composition of the precipitates.
Article
Magnesium ammonium phosphate (MAP) method was used to recover orthophosphate (PO4(3-)-P) and ammonium nitrogen (NH4(+)-N) from the alkaline hydrolysis supernatant of excess sludge. To reduce alkali consumption and decrease the pH of the supernatant, two-stage alkaline hydrolysis process (TSAHP) was designed. The results showed that the release efficiencies of PO4(3-)-P and NH4(+)-N were 41.96% and 7.78%, respectively, and the pH of the supernatant was below 10.5 under the running conditions with initial pH of 13, volume ratio (sludge dosage/water dosage) of 1.75 in second-stage alkaline hydrolysis reactor, 20g/L of sludge concentration in first-stage alkaline hydrolysis reactor. The order of parameters influencing MAP reaction was analyzed and the optimized conditions of MAP reaction were predicted through the response surface methodology. The recovery rates of PO4(3-)-P and NH4(+)-N were 46.88% and 16.54%, respectively under the optimized conditions of Mg/P of 1.8, pH 9.7 and reaction time of 15min.
Article
Three novel composite adsorbents, sulfate-coated zeolite (SCZ), hydrotalcite (SCH), and activated alumina (SCAA), were characterized and employed for the removal of phosphate from aqueous solution using equilibrium and kinetic batch experiments. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectrum were used to study the surface characteristics of the coated layer. Equilibrium tests showed that the adsorption of phosphate followed both Langmuir and Freundlich isotherms. The powder-type SCZ was better for phosphate removal (maximum binding energy, β = 111.49 mg g−1) compared to hydrotalcite and activated alumina. The adsorption of phosphate was considered to take place mainly by ion exchange. The kinetic data followed a pseudo-second-order kinetic model. The initial adsorption of phosphate onto the sulfate-coated adsorbents was fast, indicating that the sulfate-coated materials developed in this study can be used as promising adsorbents for the removal of phosphate from wastewater or sewage.
Article
The aim of this study was to explore the feasibility of utilizing inorganic mesostructures for the removal of phosphorous in laboratory experiments. The emphasis of the experiments was on the comparison of the efficiency of phosphorous adsorption between mesostructures synthesized using two different inorganic materials. Powder X-ray diffraction, Fourier transformed infrared spectroscopy, and Brunauer-Emmett-Teller(BET) methods were used to characterize the inorganic mesostructures. The efficiencies of silica and titanium mesostructures for the removal of phosphorous from aqueous solutions were investigated on a batch scale. Equilibrium data were analyzed using the Langmuir isotherm. The maximum adsorption capacities of the mesostructured adsorbents were found to be 49.3 and 19.5 mg g-1 for the titanium and silica mesostructures, respectively. The adsorption kinetics was best described by a pseudo-third-order kinetic model. The results from this study indicated that the titanium mesostructure, because of low cost and high capability, has the potential to be utilized for the cost-effective removal of phosphorous from sewage or wastewater. (C) 2011 American Institute of Chemical Engineers Environ Prog, 2012
Article
This report shows that silica sulfate is removing phosphate from wastewater very efficiently. Phosphorus removal and recovery from wastewater is a worldwide issue due to pollution of natural waters by phosphate and depletion of phosphate ores. Adsorption is a process that can remove phosphate at low concentrations. Adsorption also allows the recovery of phosphate for possible re-use. Here, we studied the adsorption of phosphate from wastewater using commercial Zr ferrite, Zr-MCM 41 and silica sulfate. We calculated equilibrium isotherms, kinetic models and thermodynamic effects under conditions similar to real wastewaters. We found that the equilibrium data for the adsorption of phosphate were best fitted to the Freundlich model. The results show that the maximum uptake of phosphate was 3.36 mg g−1 for Zr-MCM, 27.73 mg g−1 for Zr ferrite and 46.32 mg g−1 for silica sulfate. The kinetic results of the three adsorbents were satisfactorily predicted using a pseudo-second-order model. We found that silica sulfate provided excellent characteristics in terms of the maximum adsorption and rate constant for the adsorption of phosphate. The thermodynamic data showed that increasing the temperature enhanced the adsorption of phosphate onto silica sulfate. Our findings will help to define efficient methods to remove phosphate from wastewater.