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Industrial wastewater generated by a drug manufacturing plant located in Spain was degraded by Fenton oxidation processes, which employ waste-metallic iron shavings as heterogeneous zero-valent iron (ZVI) catalyst and hydrogen peroxide. The effluent comprises a complex mixture of organic substances which are very refractory to common conventional treatments and it is characterized by a low BOD/COD ratio. The stirring speed or the particle size has been found to be the determining factors, greatly influencing the degradation of the organic pollutants present in the wastewater. The influence of the initial hydrogen peroxide concentration has also been evaluated. The optimal conditions for degradation led to total organic carbon (TOC) reductions of up to 60%. The remarkable results of TOC mineralization could also be attributed to the physico-chemical modification of the ZVI during the oxidizing process. This study shows that the ZVI/H2O2 system can be considered as an easy, economic and effective alternative solution as a pre-treatment step before biological treatments.
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Pharmaceutical wastewater
degradation: effective and economical
treatment using waste-metallic iron
shavings
Yolanda Seguraa, Fernando Martíneza & Juan Antonio Meleroa
a Department of Chemical and Environmental Technology, Rey
Juan Carlos University, Madrid 28933, Spain
Published online: 29 Apr 2014.
To cite this article: Yolanda Segura, Fernando Martínez & Juan Antonio Melero (2014)
Pharmaceutical wastewater degradation: effective and economical treatment using waste-
metallic iron shavings, International Journal of Environmental Studies, 71:2, 200-208, DOI:
10.1080/00207233.2014.903128
To link to this article: http://dx.doi.org/10.1080/00207233.2014.903128
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Pharmaceutical wastewater degradation: effective
and economical treatment using waste-metallic
iron shavings
YOLANDA SEGURA*, FERNANDO MARTÍNEZ AND JUAN ANTONIO MELERO
Department of Chemical and Environmental Technology, Rey Juan Carlos University,
Madrid 28933, Spain
Industrial wastewater generated by a drug manufacturing plant located in Spain was degraded by
Fenton oxidation processes, which employ waste-metallic iron shavings as heterogeneous zero-
valent iron (ZVI) catalyst and hydrogen peroxide. The efuent comprises a complex mixture of
organic substances which are very refractory to common conventional treatments and it is charac-
terized by a low BOD/COD ratio. The stirring speed or the particle size has been found to be the
determining factors, greatly inuencing the degradation of the organic pollutants present in the
wastewater. The inuence of the initial hydrogen peroxide concentration has also been evaluated.
The optimal conditions for degradation led to total organic carbon (TOC) reductions of up to 60%.
The remarkable results of TOC mineralization could also be attributed to the physico-chemical
modication of the ZVI during the oxidizing process. This study shows that the ZVI/H
2
O
2
system
can be considered as an easy, economic and effective alternative solution as a pre-treatment step
before biological treatments.
Keywords: Wastewater; Fenton process; ZVI; Iron shavings
Introduction
During the last century, a huge amount of industrial wastewater was discharged into rivers,
lakes and coastal areas. This has caused serious pollution problems in the water environ-
ment with negative consequences for ecosystems and human life. Because each industrial
sector produces its own particular combination of pollutants, their treatment must be
designed specically. Pharmaceutical waste is one of the most complex and toxic industrial
wastes [1]. The pharmaceutical industry generates a number of waste streams with differ-
ent characteristics and volumes. The active substances and their metabolites reach the sew-
age treatment plants and sometimes directly enter the environment. Accordingly, an
evaluation of the pharmaceutical concentration and the risk assessment is useful to evaluate
the level of risk to the aquatic environment in the area [2].
Biological processes are commonly used for the domestic and industrial wastewater
treatment. It is relatively simple and efcient to mineralize organic constituents in indus-
trial discharges. But, the treatment of some industrial wastewaters by conventional biologi-
cal process is difcult due to the presence of refractory and toxic organic substances.
Various pre-treatment technologies for enhancing biodegradability or refractory compounds
*Corresponding author. Email: yolanda.segura@urjc.es
© 2014 Taylor & Francis
International Journal of Environmental Studies, 2014
Vol. 71, No. 2, 200208, http://dx.doi.org/10.1080/00207233.2014.903128
Downloaded by [University Rey Juan Carlosi], [Yolanda Segura Urraca] at 02:34 21 May 2014
have been reported, including advanced oxidation processes (AOPs) such as photocatalytic
pre-treatment, ozonation and Fenton oxidation [3,4]. AOPs have been found to be success-
ful for the abatement of refractory and/or toxic organic pollutants in water and wastewater,
being mostly used in combination with conventional biological and chemical methods [5].
Most AOPs are cost-intensive operations and the time of treatment is a limiting factor in
the overall cost. Fenton oxidation processes are considered as a viable alternative for the
removal of a great variety of organic pollutants [6]. Nevertheless, this process operates at
the optimum pH 3. The use of excess quantities of ferrous ions is the major disadvantage
with the conventional Fenton process. Therefore, lately alternatives such as the heteroge-
neous zero-valent iron (ZVI) particles have been successfully applied [7,8].
ZVI has been used for the degradation of different model pollutants [9] through the acti-
vation of dioxygen for the generation of hydrogen peroxide (equation 1), which will be
decomposed to hydroxyl radicals by the ferrous ions dissolved.
Fe0þO2þ2Hþ!Fe2þþH2O2(1)
This Fenton-like ZVI process has also been successfully applied on the treatment of sev-
eral wastewaters such as olive mill efuents [10], pharmaceutical wastewaters (PWWs)
[11] and landll leachates [12].
This works investigates the efciency of the ZVI/H
2
O
2
system for the removal of
mixed-complex organic compounds contained in the wastewater produced by a pharmaceu-
tical business located in Madrid, before discharge to the receiving environment or sewer
system. The aim of this work was to obtain a cost-effective technique by using moderate
loadings of hydrogen peroxide and ZVI, employing inexpensive metallic iron shavings as
a heterogeneous catalyst which can be easily removed from the treated efuent by mag-
netic separation. In order to study diffusion problems from use of the iron shavings, we
studied the effect of various reaction parameters such as the mixing velocity or the particle
size.
Materials and methods
Iron metal powder (Sigma-Aldrich, 97% pure) and hydrogen peroxide (Scharlab, 30% pure)
were used as purchased. The iron shavings were wastes collected from a metallurgical
processing plant.
In a typical experimental setup, a cylindrical glass vessel was lled with 0.5 L of the
PWW. The PWW was previously diluted 1/50 until initial total organic carbon (TOC) of
ca. 100 mg L
1
. Thereafter, appropriate amounts of hydrogen peroxide and ZVI (commer-
cial powder or iron shavings) were added in the presence of aeration with a ow rate of 5
L min
1
. The temperature was controlled at 22 ± 2 °C during the reaction. The iron metal
was suspended in the aqueous solution and gently mixed using a magnetic stirrer while
adjusting the pH to ca. 3 with H
2
SO
4
. Iron shavings were separated by using shape-selec-
tive sieves with mesh ranging from 2 mm to 300 μm. The amount of initial hydrogen per-
oxide is equivalent to the stoichiometric amount, half or twice (coded as 100, 50 or 200%,
respectively) for the complete mineralization of the organic compounds contained in the
PWW to CO
2
and H
2
O (equation 2)
CþH2O2!CO2þH2O (2)
Pharmaceutical wastewater degradation 201
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Samples were taken throughout reaction time (0, 10, 20, 40, 60 and 120 min) and ltered
through 0.22 μm nylon membranes prior to analysis. TOC content of the samples was
determined using a combustion/non-dispersive infrared gas analyser model TOC-V
(Shimadzu). Hydrogen peroxide concentration was measured by iodometric titration and
the iron content in the ltered solution after reaction was measured by ICP-AES analysis
using a Varian Vista AX spectrometer. The pH of the solution was measured using a
Metrohm pH meter.
Characterization of the pharmaceuticals wastewater and blank reactions
The drug manufacturing plant located in Madrid (Spain) is dedicated to producing different
active drugs for hypertension, heart diseases, osteoporosis and anti-depressive compounds.
The major operations in these plants generally include chemical reactions in vessels, sol-
vent extraction, crystallization, ltration and drying. The wastewaters generated in the syn-
thesis of those organic compounds (active ingredients or intermediate products) contain a
wide array of various chemical components prevailing at relatively high concentration. The
wastewater produced inhibits biological systems.
Various types of waste streams are generated by this plant depending upon the manufac-
turing process. All mixed streams were rstly treated to remove volatile solvents. The
resultant efuent was collected for study. Table 1shows the physico-chemical characteris-
tics of the wastewater. As above mentioned, the efuent contains a high organic load, con-
sidered non-biodegradable as the BOD
5
/COD ratio is 0.18.
The efciency of the ZVI/H
2
O
2
system was evaluated by comparing several blank
experiments: (i) aeration/stirring in the presence of ZVI without H
2
O
2
, in order to evaluate
the oxidizing power of the ZVI system; (ii) aeration/stirring in the presence of H
2
O
2
with-
out ZVI, in order to determine the oxidizing potential of the hydrogen peroxide in a non-
catalytic system; and (iii) aeration/stirring with neither ZVI nor hydrogen peroxide, in
order to evaluate the stripping process (gures not shown).
All blanks showed very low TOC removals, obtaining TOC degradations after 2 h of
less than 10% for all the blank reactions. The absence of H
2
O
2
and ZVI revealed an insig-
nicant reduction of the overall TOC content. The pH was kept uncontrolled during all the
experiments. Values of pH did not change throughout time; values obtained ranged
between 2.8 and 3 during the two hours of the blank experiments.
Application of iron shavings
The metallic shavings, generated as wastes from a metallurgical rm, were used and com-
pared to the commercial powder ZVI. The use of those wastes makes the Fenton-like ZVI
Table 1. Physico-chemical characteristics of the PWW generated by a pharmaceutical industry.
pH 6.50 ± 0.5
BOD
5
,mgL
1
2700 ± 150
COD, mg L
1
15,000 ± 100
Conductivity, μScm
2
70 ± 10
TOC, mg L
1
4550 ± 100
Turbidity, NTU 267 ± 1
BOD
5
/COD 0.18
Suspended solids, mg L
1
522 ± 100
202 Y. Segura et al.
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system very attractive from the economic and environmental points of view. Therefore, we
studied the degradation efciency of both types of metallic iron for the treatment of diluted
PWW 0.1 g/L TOC, using 2.4 g/L of ZVI and 200% H
2
O
2
of the stoichiometric amount
for the total mineralization of the organic compounds to CO
2
and H
2
O.
Figure 1shows TOC and H
2
O
2
conversions obtained for the commercial ZVI powder
and for the waste-metallic iron shavings. The iron shavings reached TOC conversions of
9, 15, 20 and 40%, after 20, 40, 60 and 120 min of reaction, respectively. Compared to the
results observed for the commercial ZVI powder, using the same experimental conditions,
(20, 32, 40 and 55% over 20, 40, 60 and 120 min, respectively) lower TOC degradations
was obtained. The particle sizes of the iron shavings are bigger than those of the powder
catalyst. Further, the slightly lower degradation obtained in the case of the iron shavings
was probably due to the diffusion problems of the iron shavings as we used a mix of dif-
ferent particle sizes (ranging from 5 mm to 200 μm).
The pH values were kept acidic throughout the reaction in both cases. A lower H
2
O
2
consumption for the iron shavings with nal H
2
O
2
conversions of 65% was also observed;
unlike the almost total oxidant conversion obtained after 120 min (90%) when using ZVI
powder.
Even if the TOC degradation obtained is slightly higher when using commercial iron
powder (due to the smaller particle size) in order to obtain a more cost-effective technol-
ogy, the optimization of the different parameters of the Fenton-like process can be carried
out using the metallic waste of iron shavings as a heterogeneous catalyst.
Inuence of the stirring velocity
The inuence of the mixing velocity during the Fenton reaction using iron shavings was
evaluated using two identical vessels containing the PWW in the presence of ZVI and
H
2
O
2
, under the same experimental conditions (200% H
2
O
2
and 2.4 g/L). Two types of
agitation velocities (500 and 1000 rpm) were tested using magnetic stirrers. The results
20 40 60 80 1 120
0
20
40
60
80
100
X (%)
Time (min)
commercial ZVI powder
ZVI shavings
100
0
20
40
60
80
100
XH2O2 (%)
TOC
Figure 1. The effect of the ZVI source in terms of TOC (columns) and hydrogen peroxide (lines) conversions.
Initial experimental conditions: TOC
0
0.1 g L
1
, acidic pH (3), ZVI (2.4 g L
1
), H
2
O
2
(200%), stirring velocity
(500 rpm) and 5 L min
1
air ow.
Pharmaceutical wastewater degradation 203
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showed (gure 2) a remarkable inuence when the mixing stirring velocity increases. The
effect of increasing the mixing agitation velocity was especially signicant during the rst
period (up to one hour) of the reaction obtaining TOC conversions after 40 and 60 min of
3035% instead of 1820% conversions for the 500 and 1000 rpm, respectively. A moder-
ate difference, however, was observed after 2 h of reaction, obtaining 39 and 43% of TOC
removal for the 500 and 1000 rpm, respectively. This proves that the ow velocity and tur-
bulence signicantly increased the TOC mineralization in the treatment of the PWW.
Inuence of the particle size of the iron shavings
Experiments were carried out using mixed shavings with different particle sizes ranging
from 5 mm to 200 μm. In order to evaluate the inuence of the particle size on the TOC
degradation, the iron shavings were sieved, obtaining different particle lengths (350, 700
and 2000 μm). Figure 3shows the effects of the particle size of the iron shavings on the
hydrogen peroxide conversion and on the removal of the organic compounds present in
the PWW. It is evident that the TOC degradation depends on the iron particle size, with
higher catalytic activity being obtained in terms of TOC as the particle size decreases.
TOC conversions of 35, 46 and 55% after 2 h of reaction were obtained for the particle
sizes of 2000, 700 and 350 μm, respectively.
Shavings with smaller particle sizes (350 μm) were the most active (obtaining 16, 28
and 55% after 40, 60 and 120 min, respectively), whereas the biggest sizes led to lower
degradations (4, 16, 27% compared to 4, 9, 15% respectively, after 20, 40 and 60 h of
reaction).
It is well known that the activity can be improved by using nano-sized F0
eparticles com-
pared to bigger sizes and different physical structures of F0
e. The use of bigger particle
sizes imposes mass transport limitations and clearly inhibits the Fenton degradation. Values
of pH kept acidic throughout the reaction time, as the hydrogen peroxide is still present
after 2 h.
20 40 60 80 100 120
0
20
40
60
80
100
XTOC (%)
Time (min)
500rpm
1000rpm
0
20
40
60
80
100
XH2O2 (%)
Figure 2. The effect of the mixing velocity on the TOC (columns) and hydrogen peroxide (lines) conversions.
Initial experimental conditions: TOC
0
0.1 g L
1
, acidic pH (3), ZVI (2.4 g L
1
), H
2
O
2
(200%) and 5 L min
1
air
ow.
204 Y. Segura et al.
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Inuence of the concentration of the oxidant
The effectiveness of the Fenton-like ZVI treatment depends on the formation of oxidizing
species such as hydroxyl radicals, which are produced by the decomposition of the hydro-
gen peroxide. We studied the inuence of different H
2
O
2
amounts (stoichiometric amount,
half or twice, codied as 100, 50 and 200%, respectively) for the treatment of PWW 0.1
g/L TOC using 2.4 g/L of ZVI and initial pH of 3. Figure 4shows the results of the TOC
and hydrogen peroxide conversions using different oxidant concentrations for the treatment
of PWW. The increase of the hydrogen peroxide concentration evidenced a clear enhance-
ment of performance when using 50 and 100%. But, when an excess of 200% was used
0 20 40 60 80 100 120
0
20
40
60
80
100
X (%)
Time (min)
350 µ m
700 µ m
2 mm
0
20
40
60
80
100
XH2O2
(%)
TOC
Figure 3. The effect of the shavings particle size (350, 700 and 2000 μm) in terms of TOC (columns)
and hydrogen peroxide (lines) conversions. Initial experimental conditions: TOC
0
0.1 g L
1
, acidic pH (3), ZVI
(2.4 g L
1
), (200%) H
2
O
2,
stirring velocity (1000 rpm) and 5 L min
1
air ow.
0 20 40 60 80 100 120
0
20
40
60
80
100
XTOC(%)
Time (min)
200%
100%
50%
0
20
40
60
80
100
XH2O2
(%)
Figure 4. The effect of the hydrogen peroxide concentration (50, 100 and 200% of the stoichiometric amount)
in terms of TOC (columns) and hydrogen peroxide (lines) conversions. Initial experimental conditions: TOC0 0.1
gL
1
, acidic pH (3), ZVI (2.4 g L
1
), stirring velocity (1000 rpm), particle size (350 μm) and 5 L min
1
air ow.
Pharmaceutical wastewater degradation 205
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the degradation decreased. We obtained TOC conversions of 45, 62 and 53 when using
50, 100 and 200% respectively of the stoichiometric amount.
It is well known that when one of the Fenton reactants (Fe or H
2
O
2
) is overdosed it can
react with the hydroxyl radicals inhibiting the organic degradation. An excess of oxidant
induces the radical scavenging reaction (equation 3). Such inhibition was observed using
2.4 g/L of ZVI and an excess of the hydrogen peroxide (200%).
H2O2þHO!HO
2þH2O (3)
Regarding the hydrogen peroxide conversions, a reasonable decrease was observed; the
oxidant concentration decreased keeping the ZVI concentration constant (2.4 g/L). Total
oxidant consumptions were achieved after 120 min of treatment when 50 and 100% of
H
2
O
2
were used. When an excess of 200% was used, conversions of 90% were obtained
after 2 h of reaction. The pH values kept acid (2.93.1) throughout the reaction, except in
the case of 50 and 100%. In those cases, the pH went up to 4.5 after 2 h of reaction,
which occurred when the hydrogen peroxide depleted.
In order to use less oxidant making the process as economic as possible, the stoichiome-
tric amount of the hydrogen peroxide is used in the rest of the experiments.
Effectiveness of fresh and reused iron shavings
Accompanying the ZVI corrosion during the process, iron oxides are built up on the metal-
lic surface. Formation of iron corrosion layers starts with dissolved O
2
oxidation of metal-
lic iron. Figure 5shows TOC and hydrogen peroxide conversions of experiments
performed using fresh and reused materials after two or three times, for the treatment of
0.1 g/L PWW using ZVI concentrations of 2.4 g/L and the stoichiometric amount of H
2
O
2
(100%), with the highest mixing velocity (1000 rpm) and smallest particle size (350 μm).
Results revealed a rapid initial degradation of the fresh iron shaving material in terms of
TOC mineralization, compared to degradation obtained when the catalyst was twice or
020406080100120
0
20
40
60
80
100
XTOC(%)
Time (min)
1st use
2nd use
3rd use
0
20
40
60
80
100
XH2O2
(%)
Figure 5. The effect of reusing iron shavings (1, 2 or 3 times) in terms of TOC (columns) and hydrogen perox-
ide (lines) conversions. Initial experimental conditions: TOC
0
0.1 g L
1
, acidic pH (3), ZVI (2.4 gL
1
), H
2
O
2
(100%), stirring velocity (1000 rpm), particle size (350 μm) and 5 L min
1
air ow.
206 Y. Segura et al.
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three times reused. But, the TOC removal after two hours was only slight superior than in
the case of the reused material, with 63% compared to 58 and 59% of TOC mineralization
after 2 h for the 2nd and 3rd use, respectively.
Although chemical composition of the iron shavings obtained after reaction was not
identied in this study, the shavings were likely a mixture of different iron oxides/oxy-
hydroxides. These iron oxides likely play a vital role in improvement of the water quality.
The formation of iron oxides on the metallic ZVI surface has been reported in literature as
another mechanism that could generate hydroxyl radicals due to the formation of galvanic
cells between ZVI and the iron oxides formed on the metallic surface [9]. But, with
increasing thickness of the layer of iron corrosion products, diffusion of dissolved O
2
to
the metallic iron surface becomes more difcult [13]. On fresh surfaces, the adsorption
ability and reactivity of the ZVI might be high.
These promising results suggest that the metallic shavings, despite initial rapid oxidation
of the particle surface and slower initial activity in terms of TOC degradation after use,
have sufcient residual oxidizing power to enable them to be reused a few more times or
to even to be included in a continuous longer treatment process.
Conclusions
This study shows that ZVI/H
2
O
2
can be considered as an effective alternative solution for
the removal of many organic pollutants present in a wastewater generated by a drug manu-
facturing plant located in Madrid. Iron shavings, wastes from a metallurgical business, are
a promising, low-cost material which can be employed as a heterogeneous Fenton-like
catalyst. TOC reductions of up to 60% were obtained after 2 h reaction, being an easy,
economic and effective pre-treatment step.
This degree of organic mineralization was reached by using moderate loadings of ZVI
shavings and hydrogen peroxide. The shavings can be easily removed magnetically after
the treatments. The consumption of hydrogen peroxide was total at the end of the reaction,
when the stoichiometric amount of oxidant was used, which was the optimal amount within
the studied dose range. The researchers have also assessed the effect of the stirring velocity
during the process on the TOC degradation, as well as the particle size of the shavings
employed. These parameters both inuenced remarkably the overall TOC removal. Higher
mixing velocities as well as the use of smaller particle sizes of iron shavings were found to
be more effective. Moreover, the waste-metallic iron shavings were reused three times and
even if a slower kinetic was shown through time of reaction, the TOC conversion was up to
60% in all cases with a total consumption of the oxidant after two hours.
Acknowledgements
We gratefully acknowledge nancial support from the Regional Government of Madrid
provided through project REMTAVARES and the European Social Fund.
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... Multiple studies have investigated the particle properties (PP) of wastewater in-fluents and effluents [40,88,[118][119][120][121] as well as in bioreactors [122,123], and the findings of these studies highlight the relationship between PP and several key parameters of treatment processes, each of which are discussed throughout this review. ...
Thesis
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This thesis is concerned with the development of methodologies for automatically assessing fluid properties in wastewater treatment plants, and to monitor plant performance and efficiency. Reliable performance metrics are important for optimising the operation of treatment plants. While sensor technologies are not new to the wastewater treatment field, the application of imaging and image processing systems has seen little development in recent years. Currently, there are a multitude of sensor technologies to monitor a variety of performance parameters. However, research has found that, in practice, the results from these sensors are rarely relied upon due to inconsistent calibration schedules, compounded by a lack of full-time maintenance staff. Instead, these sensors are frequently bypassed in favour of more subjective manual estimates. In this thesis, the problems with current monitoring practices for wastewater treatment plants are considered. Two areas of interest are highlighted; (i) sludge monitoring, using Sludge Volume Index as a performance metric and (ii) effluent monitoring, using turbidity as a quality metric. A review of the guideline sludge monitoring procedures is presented as well as a discussion of alternative on-site monitoring practices. This review highlights the need for an automated system for per- forming sludge monitoring, as per the guideline procedures. Subsequently, an image processing system for settled sludge volume measurement is proposed and tested. Effluent turbidity is primarily affected by a high number of colloidal particles in the particle size distribution. Current effluent turbidity monitoring practices include submerged turbidimeters, that require regular calibration. In practice, it was found that subjective manual estimation of turbidity was often being conducted ”by eye”. A study was devised to characterise the accuracy of the subjective estimation. Firstly, an imaging methodology was designed to capture effluent images illustrating light decay as a function of increasing fluid depth. These images were then presented to persons with no knowledge of wastewater treatment monitor and subjectively rated on turbidity. The results of the subjective test were then compared to established laboratory-based turbidity measurement, and a clear correlation was found between the two. Subsequently, an image processing system was designed to replace the observer and to objectively characterise the light decay as a function of fluid depth. Once again, the results from this image processing system were compared to the established laboratory-based measurements and an improved correlation over the subjective comparison was found. Finally, the implications of the deployment of a combined monitoring system is discussed, along with the benefits to current monitoring practices.
Article
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The effectiveness of photolysis (UV), peroxidation (H(2)O(2)), peroxidation combined with UV light (UV/H(2)O(2)), Fenton reagent (H(2)O(2)/Fe(2+)), and the photo-Fenton process (H(2)O(2)/Fe(2+)/UV) at degrading the textile dye Reactive Blue 19 was evaluated. The efficiency of the photo-Fenton process for degrading raw textiles and biologically pre-treated effluents was also evaluated. H(2)O(2) (100-800 mg L(-1)) and UV light did not degrade dye when used separately. The UV/H(2)O(2) process was effective but slow: 91% of dye degraded within 3 h of reaction at a concentration of 500 mg L(-1) H(2)O(2). Fenton reagent reduced dissolved organic carbon by 36.8% and color was reduced by >98% within a few minutes of reaction. The photo-Fenton process was the most efficient, reducing 94.5% of dissolved organic carbon and 99.4% of color. The combination of a biological system and the photo-Fenton process degraded a high level of textile effluent degradation, reducing dissolved organic carbon by 88%, color by 85%, chemical oxygen demand by 80%, and biochemical oxygen demand by 93%.
Article
The pre-treatment of a pharmaceutical wastewater (PWW) by Fenton oxidation with zero-valent iron (ZVI) and hydrogen peroxide was investigated to improve the degradation of the complex-mixture of organic compounds present in the wastewater. The influence of different crucial parameters such as the initial hydrogen peroxide concentration, the ZVI concentration and the capacity of the ZVI/H2O2 system to treat different organic loading have been evaluated. The optimal conditions for degradation led to TOC reductions of up to 80% in only 1 h of treatment. This degree of organic mineralization was reached by using moderate loadings of ZVI and hydrogen peroxide (ZVI/TOC weight and H2O2/TOC molar ratios of 12 and 3.2, respectively). Moreover, the use of waste-metallic iron shavings in terms of TOC removal compared to commercial ZVI powder may be a promising and cheaper development.
Article
Although the growth in sales of pharmaceuticals could be taken as a sign of the availability of medical services and medicine, it also indicates an increasing input of drug residues to the environment via treated sewage water. In this paper the medicine consumption in mass units was calculated on the basis of the sale of pharmaceuticals in 2010. Eleven active substances (ASs) were selected for risk assessment according to the Swedish model. The predicted environmental concentration (PEC) for each AS was calculated and divided by the predicted no-effect concentration. Additionally, hazardous properties were taken into consideration. The calculated values of amoxicillin (PEC = 0.24–1.43 μg/l), diclofenac (PEC = 0.2–0.59 μg/l), ciprofloxacin (PEC = 0.052–0.13 μg/l), and ethinyl estradiol (PEC = 0.3 × 10 μg/l) reflect a high level of risk to the aquatic environment in the area.
Article
Nitrobenzene (NB) oxidation through conventional Fenton process produces a considerable amount of highly toxic 1,3-dinitrobenzene (1,3-DNB) as a byproduct. Aiming at significantly decreasing 1,3-DNB production in Fenton process, we developed a novel system integrating a reductive pretreatment via zero-valent iron (ZVI) with Fenton process to degrade NB in aqueous solution and industrial wastewater. The NB reduction efficiency of ZVI pretreatment could be controlled by adjusting the initial ZVI concentration and/or the initial pH of NB solution in a completely stirred ZVI reactor. After partial NB reduction by ZVI pretreatment, the residual NB was oxidized by a subsequent Fenton process. Aniline and ferrous irons were generated in ZVI pretreatment, producing an inhibitory effect on the formation of 1,3-DNB in Fenton process. While conventional Fenton process attained the NB removal efficiency of 95.0% and brought the relative 1,3-DNB yield (the molar concentration of 1,3-DNB in relation to that of converted NB) of 5.0%, the integrated system with the NB reduction efficiency of 48.1% achieved a similarly high NB removal efficiency (93.0%), but its relative 1,3-DNB yield was only 0.4%. Applied to the full-scale treatment of NB-rich industrial wastewater, the ZVI-Fenton integrated system with the NB reduction efficiency of 50.0% and conventional Fenton process produced dinitrobenzene isomers at the total concentrations of 0.005mM and 0.060mM, respectively. Accordingly, the integrated system increased the biodegradability and decreased the acute toxicity of the wastewater significantly more than conventional Fenton process. Therefore, the novel ZVI-Fenton integrated process is effective in the degradation of NB wastewater.
Article
Two anaerobic fixed film reactors were operated at 30°C and 55°C (as mesophilic and thermophilic reactors) with actual pharmaceutical wastewater to observe the effects of organic loading rate (OLR) and height of the reactor. Both the reactors were operated at OLR of 0.53, 0.85, 1.17 and 1.49 kg COD md at HRT of 4.7 days. COD, TVA, SS, VSS, NH4 ‐N, PO4 ‐P and SO4 were also measured. AMFFR showed better performance than ATFFR in terms of COD removal, and the effective height of the reactor was in the range of 30–90 cm.
Article
This paper was presented in part by V. L. Snoeyink as the Simon W. Freese Lecture at the 2002 Canadian Society of Civil Engineers/Environmental and Water Resources Institute of ASCE Environmental Engineering Conference in Niagara Falls, Ontario, Canada, July 22, 2002. The interactions of corroded iron pipe surfaces with water are of importance because they can lead to serious water quality degradation and material deterioration. A conceptual model has been developed in this paper to describe the formation and growth of iron scales, and their reactions that lead to colored water problems. Most corrosion scales have characteristic structural features, such as a loosely held top surface layer, a shell-like layers, and a porous core. According to this model corrosion scales are expected to grow from inside the scale via the corrosion reaction, i.e., the conversion of iron metal to ferrous ion. The average oxidation state of iron increases with distance from the pipe wall. The scale structure and scale reactions permit the ferrous iron to be released to the bulk water, where it undergoes conversion to particulate ferric iron, which is the cause of colored water. Scale structure and composition play important roles in the reactions of iron scales that lead to iron release, and water quality control to decrease the porosity of the scale is an important means of reducing iron release. It is anticipated that the conceptual model presented here will be used as a basis for changing water quality to minimize colored water formation, and as a guide for further research.
Article
The aim of the present study addresses the applicability of the Fenton-like zero valent iron (ZVI) process on the remediation of several landfill leachate samples coming from different points of an existing treatment plant: initial effluent (ERaw), after biological treatment (EPost-Bio) and depurated effluent (ETreat). The effects of pH and Fe0 concentration were determined for ERaw and ETreat. It was observed that the use of low pH values enhances the treatment efficiency. Moreover, the increase on iron load leads to higher COD removals until a certain point after which the catalyst starts to show radical scavenger effect. The low efficiency attained for ERaw (COD removal always below 8%) indicates that this methodology is not suitable for this effluent. However, final ETreat within the legal limits for discharge were attained when pH = 2 was used with 38% of COD removal. The utilization of iron shavings as catalyst in the Fenton-like process showed to be a suitable and economical solution on the remediation of ETreat and EPost-Bio with high COD abatements (up to 60%) leading to streams able to be released to the municipal sewage. Since the real plant often does not comply with regulatory thresholds and according to our results, it seems advisable to implement this technology after the bio-reactor for substituting the already existing physico-chemical treatment.
Article
Nowadays, due to the increasing presence of molecules, refractory to the microorganisms in the wastewater streams, the conventional biological methods cannot be used for complete treatment of the effluent and hence, introduction of newer technologies to degrade these refractory molecules into smaller molecules, which can be further oxidized by biological methods, has become imperative. The present work aims at highlighting five different oxidation processes operating at ambient conditions viz. cavitation, photocatalytic oxidation, Fenton's chemistry (belonging to the class of advanced oxidation processes) and ozonation, use of hydrogen peroxide (belonging to the class of chemical oxidation technologies). The work highlights the basics of these individual processes including the optimum operating parameters and the reactor design aspects with a complete overview of the various applications to wastewater treatment in the recent years. In the next article of this two article series on imperative technologies, hybrid methods (basically combination of the oxidation processes) will be discussed and the current work forms a useful foundation for the work focusing on hybrid technologies.
Article
The mechanism for removal of phenol by zero-valent iron (ZVI) was quantitatively evaluated in the presence of dissolved oxygen by varying the pH from 2 to 8.1 (natural). The measurement of OH radical concentration suggests that the removal of phenol by ZVI was occurred due to the decomposition by the Fenton reaction besides the adsorption/precipitation to the iron surface. From the measurements of dissolved organic carbon (DOC) in the filtrate with the 0.45 μm syringe filter and the solution obtained from acidification of suspended precipitates, the roles of decomposition by the Fenton reaction and adsorption/precipitation were separately evaluated. At solution pH 3, 91% of phenol removal was achieved and 24% of TOC (total organic carbon) decreased. The contribution of the Fenton reaction was found to be 77% of overall TOC reduction. When the pH values were 4 and 5, the overall TOC removal was found to be mainly due to the adsorption/precipitation. At pH 2 and 8.1, the reduction of TOC was very small. The pH and dissolved oxygen significantly affected the dissolution of iron and the production of OH radicals and changed the roles of phenol removal by the Fenton reaction and adsorption/precipitation.
Article
Nowadays there is a continuously increasing worldwide concern for development of alternative water reuse technologies, mainly focused on agriculture and industry. In this context, Advanced Oxidation Processes (AOPs) are considered a highly competitive water treatment technology for the removal of those organic pollutants not treatable by conventional techniques due to their high chemical stability and/or low biodegradability. Although chemical oxidation for complete mineralization is usually expensive, its combination with a biological treatment is widely reported to reduce operating costs. This paper reviews recent research combining AOPs (as a pre-treatment or post-treatment stage) and bioremediation technologies for the decontamination of a wide range of synthetic and real industrial wastewater. Special emphasis is also placed on recent studies and large-scale combination schemes developed in Mediterranean countries for non-biodegradable wastewater treatment and reuse. The main conclusions arrived at from the overall assessment of the literature are that more work needs to be done on degradation kinetics and reactor modeling of the combined process, and also dynamics of the initial attack on primary contaminants and intermediate species generation. Furthermore, better economic models must be developed to estimate how the cost of this combined process varies with specific industrial wastewater characteristics, the overall decontamination efficiency and the relative cost of the AOP versus biological treatment.