prepared by J. Anotai*,**, C.M. Chen***, L. Bellotindos**** and M.C. Lu*** Department of Environmental Engineering, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, Bangkok 10140, Thailand (E-mail: jin.ano@kmutt.ac.th) ** National Center of Excellence for Environmental and Hazardous Waste Management (NCE-EHWM), Chulalongkorn University, Bangkok, Thailand *** Department of Environmental Resources Management, Chia-Nan Univer for Urban Environments in Asia, 25-28 May 2011, Manila, Philippines. organized by International Water Association (IWA).

1. Degradation of Ethanolamine by Fluidized-bed Fenton
Process
J. Anotai*,**, C.M. Chen***, L. Bellotindos**** and M.C. Lu***
*
Department of Environmental Engineering, Faculty of Engineering, King Mongkut’s University of
Technology Thonburi, Bangkok 10140, Thailand (E-mail: jin.ano@kmutt.ac.th)
**
National Center of Excellence for Environmental and Hazardous Waste Management
(NCE-EHWM), Chulalongkorn University, Bangkok, Thailand
***
Department of Environmental Resources Management, Chia-Nan University of Pharmacy and
Sciences, Tainan 717, Taiwan (E-mail: mmclu@mail.chna.edu.tw)
****
Office of Research and Extension, Universidad de Zamboanga, Zamboanga City, Philippines
(E-mail: bingb@uz.edu.ph)
Abstract
The mass production value of thin film transistor liquid crystal display (TFT-LCD) in Taiwan,
which is second in the world next to Korea, will reach one trillion NT dollars yearly in the near
future. However, the resulting wastewater will also increase to approximately 200,000 m3/day. The
main component of this wastewater is ethanolamine (MEA). Advanced oxidation processes (AOPs)
are efficient methods for degrading toxic chemicals. One of these processes, the Fluidized-bed
Fenton process, was used for the treatment of the TFT-LCD wastewater to remove the
monoethanolamine. In the design of experiment, the Box-Behnken design was used to optimize the
operating conditions. As a result of the degradation of this wastewater by Fluidized-bed Fenton
process, the treated wastewater contained a large amount of ammonia which can be removed using
magnesium chloride and sodium hydrogen phosphate as the precipitating agents. A removal
efficiency of 98.9% for 5mM MEA was achieved after 2 hours under optimal conditions of pH = 3,
[Fe+2] = 5mM and [H2O2] = 60mM. A removal efficiency of 99.8% for ammonia nitrogen was
achieved under optimal conditions of pH = 3 and molar ratio of Mg+2 :NH4+ :PO4-3 at 1.4:1:1.1. The
objective of this study is to determine the optimal conditions for the degradation of ethanolamine by
Fluidized-bed Fenton process and removal of ammonia from TFT-LCD wastewater. For this study,
the use of Fluidized-bed Fenton process proves to be effective for the treatment of TFT-LCD
wastewater from an industry with increasing demand. Since the process can result in reduced sludge
production, it can be used for wastewater reuse applications.
Keywords: TFT-LCD; Monoethanolamine; Fluidized-bed Fenton process
INTRODUCTION
Thin film transistor liquid crystal display (TFT-LCD) is one of the most popular displays used all
over the world. It can be applied in computers, televisions, and even on cellular phones. Taiwan,
being one of the largest TFT-LCD producing countries in the world, is experiencing problems
regarding the treatment of wastewater generated from these industries. The total amount of
wastewater from TFT-LCD manufacturing plants alone is expected to exceed 200,000 m3/day in the
near future. The amount of pollutants produced during manufacturing processes of TFT-LCD
substantially increases due to an increasing production of the opto-electronic industry. Therefore,
finding an effective and economical way to treat this wastewater is an essential work for Taiwanese
TFT-LCD industry.
Most of the wastewater produced from these processes contain an organic stream, which is mostly
composed of dimethylsulfoxide (DMSO, (CH3)2SO), monoethanolamine (MEA, H2NC2H4OH),
tetramethylammonium hydroxide (TMAH, (CH3)4NOH) and isopropanol (IPA, C3H7OH). These
are high strength nitrogen and sulfur containing wastewater. This kind of organic wastewater is
1

2. considered to be slow or non-biodegradable due to its low BOD/COD ratio(Park et al. 2001).
Moreover, the organic stream comprises more than 33% of the total wastewater making
conventional treatment processes ineffective.
Advanced oxidation processes (AOPs) show potential as one of the technologies for treating
refractory compounds in waters and wastewater (Chou et al. 1999). The combination of hydrogen
peroxide and ferrous salt is referred to as “ Fenton’s reagent ”. The primary oxidant in Fenton’s
reagent is the hydroxyl radical (·OH) generated by the reaction of hydrogen peroxide with ferrous
ion (Fe2+) as shown in equation 1.
H2O2 + Fe2+ → OH ‧ + OH- + Fe3+ (1)
Fenton’s reagent is an effective and simple oxidant for various types of organic contaminants.
The drawback of Fenton's reaction is the production of substantial amount of Fe(OH)3 precipitate.
To solve this problem, the application of iron oxides as catalysts in oxidizing organic contaminants
has been studied extensively (Chou. 1990; LinR. 1997; Valentine. 1998; Al-Hayek. in press). Major
disadvantage of Fenton reaction is the production of a substantial amount of ferric precipitation. To
overcome this problem, the fluidized-bed reactor (FBR) is one of the possible alternatives. In FBR,
several important processes occur simultaneously including: homogeneous chemical (H2O2/Fe2+),
heterogeneous chemical oxidation (H2O2/iron oxide), fluidized-bed crystallization, and reductive
dissolution of iron oxides. The ferric hydrolysis product of Fenton reaction can crystallize and grow
on the surface of the carriers; hence, decreasing the precipitation in puffy ferric hydroxide from
( Khunikakorn).
In this study, it was found out that after the degradation of MEA, large amount of ammonia nitrogen
could be produced, therefore, the ammonia nitrogen removal was also investigated. The presence of
ammonium nitrogen in excess on bodies of water can lead to water eutrophication. Conventional
biological and physicochemical treatment methods are the widely used treatment processes for
ammonium nitrogen removal. The biological process is economical for wastewater treatment, but is
often not effective for high concentration of ammonium nitrogen due to shortage of carbon sources
for denitrification. Various methods of physico-chemical processes can be applied to treat high
concentrations of ammonium nitrogen, such as air stripping, ion exchange, membrane separation,
and chemical precipitation. Chemical precipitation of ammonium nitrogen removal by adding
magnesium salt and phosphate to form magnesium ammonium phosphate hexahydrate (MAP) is a
useful method. MAP is a white crystal substance consisting of equal molar concentrations of
magnesium, ammonium and phosphorus. The chemical reaction is expressed in Eq. (2):
Mg2+ + NH4+ + PO43- + 6H2O → MgNH4PO4·6H2O (2)
The method of chemical precipitation has been studied widely for the treatment of high strength
ammonium nitrogen wastewater. In the present research, the chemical precipitation technology for
ammonium nitrogen removal from wastewater (Zhang et al. 2009) was examined.
In this study, MEA degradation by fluidized-bed Fenton and Fenton process was investigated. The
effects of varying pH values, the initial concentration of Fe2+ concentration and H2O2 dosage on
MEA removal efficiency, by fluidized-bed Fenton and Fenton process were explored in greater
detail. The removal of ammonia nitrogen by chemical precipitation was determined and the
performance of Fenton process and fluidized-bed Fenton were compared.
MATERIALS AND METHODS
2

3. Chemicals
‧
Monoethanolamine, ammonia solution, ferrous sulfate heptahydrate(FeSO4 7H2O), 35% hydrogen
‧
peroxide(H2O2), magnesium chloride (MgCl2 6H2O) and disodium hydrogen phosphate
‧
(Na2HPO4 12H2O) were purchased from Merck Company. The rest of the reagents used were at
least of reagent grade. Silica dioxide (SiO2) having an average particle diameter of 0.42-0.50 mm
was used as the main carrier in the fluidized-bed Fenton process. A 1.45 L reactor was used in all
the experiments. The fluidized-bed reactor was a cylindrical glass vessel consisting of outlet, inlet
and re-circulating sections, as shown in the Figure. 1.
Figure. 1. The schematic diagram of fluidized-bed reactor (FBR).
Analytical Method
Samples were taken at selected time intervals and were immediately injected into the tubes
containing NaOH solution to stop further reaction by increasing the pH to 11. The samples were
then filtered with 0.45 µm syringe micro-filters to separate precipitated iron from the solutions.
Samples were analyzed for residual H2O2, Fe2+, and MEA. The residual MEA and ammonia
nitrogen were analyzed using the DX-120 (Dionex, USA) ion chromatography having the
CG-12A (guard) and CS-12A (analytical) column. The suppressor type was CSRS Ultra 4-mm
(Cation Self Regenerated Suppressor) and auto-regenerated with 50mA current. Eluent used was
10mM methanesulfonic acid (CH3SO3H) at 1.00 ml/min. The volume of the sample loop was 25µl.
The Fe2+ was determined by light absorbance measurement at 510 nm after complexing with
1,10-phenanthroline using a UV-Vis spectrophotometer. Residual H2O2 was analyzed by titanium
oxalate method.
Fluidized-bed Fenton process
Synthetic MEA wastewater was prepared using de-ionized water. The initial pH was adjusted with
the addition of 1.0 M H2SO4. Calculated amount of ferrous sulfate was added in the volumetric
flask containing the synthetic wastewater. The solution was then added into the reactor followed by
the carriers. The re-circulation pump was turned on to suspend the carriers and to mix the solution.
Hydrogen peroxide was finally added to the solution and the reaction was started. Samples were
taken at selected time intervals. The Fenton's reaction was stopped instantly by adding NaOH to the
reaction mixture after sampling. The samples were then filtrated on cellulose acetate membranes
with 0.45 um pore size to remove the precipitates. For the conventional Fenton process, the same
3

4. procedure was used but without using carriers in the reactor.
Chemical Precipitation Experiments
‧
Magnesium chloride (MgCl2 6H2O) and disodium hydrogen phosphate (Na2HPO4 12H2O) were ‧
added to the ammonium wastewater (1 L) at NH4+:Mg2+:PO43- molar ratios of 1 : 1.4 : 1.1. The
reaction solution was agitated by magnetic stirrers for 15 min at pH 10.1. Then it was allowed to
settle in the reaction solution for 15 min. The reaction solution was filtered through a 0.45 mm
membrane filter for analysis.
Design of Experiments
Most of studies have only focused on the basic single-factor-at-a-time approach, studying the effect
of each experimental parameter on the process performance while keeping all other conditions
constant. However, this strategy does not consider cross-effects from the factors which can result in
poor optimization. To overcome this problem, the use of statistical design experiments has proven
to be advantageous, allowing the use of the minimum number of experiments while simultaneously
changing several variables. Moreover, statistical design experiments can be used for optimization
process in multivariable system.
The Design-Expert software version 7.0(Stat-Ease, Inc., Minneapolis, USA) was used to determine
the number of experiments to be performed, calculate the experimental data and evaluate the
experimental results. In order to investigate the effects of significant factors and to obtain the
optimum condition, in this study, the Box-Behnken statistical design was used.
The optimization procedure involves studying the response of statistically designed combination,
estimating the coefficients by fitting experimental data to the response functions and predicting the
response of fit model.
RESULT AND DISCUSSION
Three important factors affecting the fluidized-bed Fenton process consisting of the initial pH,
initial Fe2+ and H2O2 concentrations were selected as factors in the Box-Behnken statistical design.
MEA, chemical oxygen demand (COD) and total iron removal efficiencies were used as the
response functions. Table 1 shows the range of values of the factors used on the Box-Behnken
statistical design.
Table 2. The levels of variables in Box-Behnken statistical design.
Variable level
Variables Symbol
Low ( -1 ) Center ( 0 ) High ( +1 )
-1 0 +1
pH A 2 3 4
2+
Fe (mM) B 0.5 1.75 3
H2O2 (mM) C 5 27.5 50
The low, center and high levels for each variable are designated as -1, 0, and +1, respectively. A
total of 17 experimental runs with three variables and three levels in Box-Behnken design,
including five replications at the center point (0,0,0,0,0) were done. The result are shown in Table 2.
Results from the experiment revealed that the maximum removal of MEA was > 98.9% while the
minimum removal was 21%. The removal of COD and total iron were between 3.4 and 64.7% and
7.4 - 67.4%, respectively.
4

5. Table 3. Design of experimental runs for the BOX-Behnken statistical design of fluidized-bed
Fenton process with 5 mM MEA.
Monoethanolamine COD T-Fe
Run Fe2+ H2O2
pH Removal Removal Removal
No. (mM) (mM)
% % %
1 4.00 0.50 27.50 21 3.4 67.3
2 3.00 1.75 27.50 56 22 41.3
3 2.00 1.75 5.00 56.7 16.8 46.1
4 3.00 0.50 50.00 30.1 9.3 27.6
5 3.00 1.75 27.50 55.8 21.3 41.6
6 2.00 1.75 50.00 60.4 19.2 16.3
7 4.00 3.00 27.50 48.8 10.5 28.7
8 4.00 1.75 5.00 38.7 16.5 43.6
9 3.00 1.75 27.50 54.9 21.5 40.8
10 3.00 0.50 5.00 39.6 21.56 14.2
11 4.00 1.75 50.00 33.4 22.57 36
12 2.00 3.00 27.50 77.1 28.4 12.7
13 3.00 3.00 50.00 98.9 64.7 43.5
14 3.00 1.75 27.50 55.7 21.7 41.7
15 3.00 3.00 5.00 47.6 11.5 7.4
16 2.00 0.50 27.50 63.1 23.4 11.5
17 3.00 1.75 27.50 55.2 22.4 41.1
Correlation of Each Parameter on Monoethanolamine Removal Efficiency
Figure 2 shows the effect of the parameters to MEA removal efficiency. Using an initial
concentration of 5 mM of H2O2 and 0.5 mM of Fe2+ resulted to a 40% MEA removal efficiency.
However, increasing the H2O2 concentration to 50 mM while maintaining the other two factors
constant resulted only to a 30% removal efficiency.
5

6. Design-Expert?Software
Monoethanolamine removal
98.9
21
Monoethanolamine removal ( % )
X1 = B: Fe2+ 99
X2 = C: H2O2
81.5
Actual Factor
A: pH = 3.00
64
46.5
29
50.00 3.00
38.75 2.38
27.50 1.75
16.25 1.13
C: H2O2 C: H2O2 B: Fe2+2+
(mM) 5.00 0.50
B: Fe (mM)
Figure 2. Three-dimensional representation of the response surface plot of the effect of initial
concentration of Fe2+ and H2O2 on removal efficiency of MEA at pH 3, ([MEA]=5×10-3M;
[Fe2+]=3×10-3M; [H2O2]=50×10-3M; [SiO2]=100g).
On the other hand, increasing Fe2+ concentration from 0.5 to 3 mM at 3 mM of H2O2 resulted to a
98.9% removal efficiency. At low Fe2+ concentration, the amount of catalyst is insufficient to
catalyze H2O2 to produce enough hydroxyl radical which resulted to a decrease in the removal of
MEA. However, too much ferrous iron and H2O2 also compete with MEA for hydroxyl radical
scavenging under certain conditions according to Eqs. 3 and 4.
Fe3+ + H2O2 → Fe-HOO2+ + H+ (3)
Fe-HOO2+ + H+ → Fe2+ + HO2 ‧ (4)
Based from the results, the best set of conditions for this system is an initial pH of 3, with an initial
ferrous iron concentration of 3mM and 50mM of H2O2 operating at 100g carrier by fluidized-bed
Fenton process.
Correlation of Each Parameter on COD removal Efficiency
As shown in Figure. 3, the maximum COD removal of 64.7% was achieved at the best conditions
with an initial concentration of 50 mM H2O2 and 3 mM Fe2+.
6

7. Design-Expert?Software
COD removal
64.7
3.4
X1 = B: Fe2+
X2 = C: H2O2 65
COD removal ( % )
Actual Factor 51
A: pH = 3.00
37
23
9
50.00 3.00
38.75 2.38
27.50 1.75
1.13
B: Fe2+ (mM)
16.25
C: H2O2 (mM)
C: H2O2 B: Fe2+
5.00 0.50
Figure 3. Three-dimensional representation of the response surface plot of the effect of initial
concentration of Fe2+ and H2O2 on removal efficiency of COD at pH 3, ([MEA]=5×10-3M;
[Fe2+]=3×10-3M; [H2O2]=50×10-3M; [SiO2]=100g).
At low ferrous iron concentration, the hydroxyl radical production rate is very slow, therefore,
hindering the COD degradation. Increasing the concentration of H2O2 however, also increases COD
removal efficiency But with excessive dosage of H2O2, scavenging reactions with hydroxyl radical
occurs as shown in Eq. 5 resulting to a decrease in COD removal. When H2O2 concentration
reached a certain level, hydroxyl radical production rate will not increase.
‧ OH + H2O2 → H2O + HO2 ‧ (5)
Correlation of Each Parameter on Total Iron Removal Efficiency
The correlation of total iron removal with pH, ferrous iron, H2O2 concentration and amount of
carriers all yielded a positive effect. The result shows that total iron removal increased when pH and
amount of carriers increased. On the other hand, increasing ferrous iron and H2O2 concentrations
could decrease the total iron removal. As can be seen from Figure 4, increasing pH value enhances
the total iron removal efficiency. The precipitation of iron hydroxide at higher pH resulted in the
decrease of dissolve iron.
7

8. Design-Expert?Software
Total iron
67.4
7.4
X1 = A: pH 68
Total iron removal ( % )
X2 = B: Fe2+
Actual Factor 53.75
C: H2O2 = 27.50
39.5
25.25
11
3.00 4.00
2.38 3.50
1.75 3.00
1.13 2.50
B: Fe2+ B: Fe2+
(mM) A: pH
A: pH
0.50 2.00
Figure 4. Three-dimensional representation of the response surface plot of the effect of initial
concentration of Fe2+ and H2O2 on removal efficiency of total iron at pH 3, ([MEA]=5×10-3M;
[Fe2+]=3×10-3M; [H2O2]=50×10-3M; [SiO2]=100g).
Fe2+ concentration also played an important role in total iron removal. Increasing Fe2+ concentration
would slightly decrease the total iron removal due to the amount of Fe3+ generated from Fenton
reaction which could crystallize on the surface of carrier.
The application of Box-Behnken design offers an empirical relationship between the response
function and variables. The equation for the removal of MEA by fluidized-bed Fenton process in
terms of coded factors are shown below:
Monoethanolamine removal = 55.52 – 14.42A + 14.82 B + 5.03C +
3.45AB – 2.25AC + 15.20BC – 4.89A2 + 1.87B2 - 3.34C2
Where A, B and C are pH, initial Fe2+ concentration and initial H2O2 concentration, respectively.
Optimization Process
The main objective of the optimization process was to determine the optimum condition for removal
of MEA, COD and total iron in fluidized Fenton process from the experimental data. The
optimization module in Design-Expert searches for combination of factor levels that simultaneously
satisfy the requirements placed on each of the responses (I et al. 2009). The optimum conditions for
the removal of MEA by fluidized-bed Fenton process are pH = 2.01, 100g of carriers, [Fe2+] = 3 mM
and [H2O2] = 50 mM. But the predicted result is only 97.4% MEA removal. Based from the actual
experiments, at the same Fe2+ and H2O2 concentrations with pH = 3, MEA removal is 98.9%.
Therefore, these conditions were chosen as the optimum for the comparison between fluidized-bed
Fenton and Fenton processes since at pH = 3, less amount of acid is needed as compared to pH = 2.
The removal efficiencies of MEA, COD and total iron at the best conditions were predicted to be 89.1,
56.49 and 26.81 %, respectively. The actual removal efficiencies were 98.9 % for MEA, 64.7 % for
COD and 43.5 % for total iron. It can be summarized that the experimental results obtained under
optimized concentration were close to the predicted resulted in terms of MEA, COD removal and
total iron removal, evidencing the reliability of the methodology used within the range of
concentration investigated.
Comparison between the Fluidized-bed Fenton and Fenton process at the optimum condition
8

9. From the Box-Behnken design experiment, using Fenton process experiments, the best conditions at
5 mM of MEA are pH = 3, [Fe2+] = 5 mM and [H2O2] = 60 mM. However, the MEA removal was
only 96.4% as illustrated in Figure. 5.
Fenton prpcess
Fluidized-bed Fenton process
1.0
0.9
Monoethanolamine remaining ( C/C0 )
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0 20 40 60 80 100 120
time (min)
Figure 5. Comparison of MEA remaining between Fenton and Fluidized-bed Fenton process with
condition of [MEA=5×10-3M]; [Fe2+=5×10-3M (Fenton); 3×10-3M (FB-Fenton)]; [H2O2=60×10-3M
(Fenton); 50×10-3M (FB-Fenton)]; [SiO2=100g].
As found in the fluidized-bed Fenton process, with a lesser amount of Fenton reagent, the MEA
removal efficiency can still reach 98.9%. This indicated that the carriers with iron oxide coating may
have catalytic reaction with H2O2.
It can be seen from Figure 5, the removal efficiency of MEA in fluidized-bed Fenton and Fenton
process shows the same trend.
1.0 Fenton process
Fluidized-bed Fenton process
0.9
0.8
CDO remaining ( C/C0 )
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0 20 40 60 80 100 120
time (min)
Figure 6. Comparison of COD remaining between Fenton and Fluidized-bed Fenton process with
condition of [MEA=5×10-3M]; [Fe2+=5×10-3M (Fenton); 3×10-3M (FB-Fenton)]; [H2O2=60×10-3M
(Fenton); 50×10-3M (FB-Fenton)]; [SiO2=100g].
9

10. The COD removal efficiency from Fenton and fluidized-bed Fenton processes were 57.3 % and 64.7
%, respectively.
2+
Fenton Fe detection dosage
2+
5 FB-Fenton Fe detection dosage
2+
Fenton Fe addition dosage
2+
FB-Fenton Fe addition dosage
4
Total iron remaining ( mM )
3
2
1
0
0 20 40 60 80 100 120
time (min)
Figure 7. Comparison of total iron remaining between Fenton and Fluidized-bed Fenton process with
condition of [MEA=5×10-3M]; [Fe2+=5×10-3M (Fenton); 3×10-3M (FB-Fenton)]; [H2O2=60×10-3M
(Fenton); 50×10-3M (FB-Fenton)]; [SiO2=100g].
Continuous dosing of iron was used in this study. The iron remaining in the solution from
fluidized-bed Fenton and Fenton processes are illustrated in Figure 7. A 25 % removal from Fenton
process and a 43.5 % removal in fluidized-bed Fenton process of total iron were observed. This shows
that 43.5 % of iron was crystallized on the surface of the carrier and were left on the adsorbent of the
fluidized-bed reactor. This amounts to a 43.5% reduction of the amount of sludge in fluidized-bed
Fenton process. A decrease in the amount of sludge was considered as an advantage of fluidized-bed
Fenton process which also reduces the separation and disposal costs as well (Muangthai et al. 2010).
Ammonia nitrogen removal by Chemical Precipitation
In this study, it was found out that after the degradation of MEA, large amount of ammonia nitrogen
could be produced, causing interference in the analysis Furthermore, ammonia nitrogen is an
essential nutrient that can lead to water eutrophication when present in excess. . Because of this, a
study on ammonia removal was also done.
In the chemical precipitation process, 5 mM of ammonia nitrogen was used. The effects of initial pH,
ratio of Mg2+ : NH4+ : PO43- and stirring times to ammonia nitrogen removal solution with initial pH
of 9.0, 10.0 and 11.0 were investigated and the results are presented in Table 4.
10

11. Table 4. Effect of conditions for ammonia nitrogen removal
Effect of initial pH Effect of added ratio Effect of stirring time
2+ 4+
Initial of Removal Mg : NH : Removal Stirring Removal
pH efficiency % PO43- efficiency % time efficiency %
9.0 84.3 1:1:1 73.5 5 88.7
10.0 99.6 1.2 : 1 : 1 81.7 10 92.4
11.0 78.7 1.4 : 1 : 1.1 99.6 15 99.6
The results showed that the best ammonia nitrogen removal efficiency (99.6%) was observed at pH =
10.0, with Mg2+ : NH4+ : PO43- ratio of 1.4 : 1 : 1.1, at 15 min stirring time.
CONCLUSIONS
The fluidized-bed Fenton process was found to be an efficient method for treating synthetic
wastewater containing MEA. Box-Behnken design was used to determine the optimum conditions
in the removal of MEA, including the prediction of the interaction between process variables. The
fluidized-bed Fenton process was proven to be more effective on MEA degradation than the
conventional Fenton process. This process is also superior in terms of total iron removal by
reducing the iron sludge via crystallization process. Chemical precipitation method was found to be
an effective way on removing ammonia nitrogen in water.
ACKNOWLEDGMENTS
This work was financially supported by the National Science Council of Taiwan under Contract No.
NSC 99-2221-E-041-012-MY3.
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