Journal of Geoscience and Environment Protection, 2014, 2, 42-47
Published Online April 2014 in SciRes.
How to cite this paper: He, F. et al. (2014). Simultaneous Removal of Perchlorate and Nitrate Using Biodegradable Poly-
mers Bioreactor Concept. Journal of Geoscience and Environment Protection, 2, 42-47.
Simultaneous Removal of Perchlorate and
Nitrate Using Biodegradable Polymers
Bioreactor Concept
Fang He1,2*, Haihong Zhou1, Xiuju Wang1, Liguo Wang1
1School of Resources and Environment, University of Jinan, Jinan, China
2Shandong Provincial Engineering Technology Research Center for Ecological Carbon Sink and Capture
Utilization, Jina n, China
Email: *
Received Dec emb er 2013
Simultaneous perchlorate and nitrate removal from contaminated groundwater in one reactor has
been realized with different methods in the past. The usage of biodegradable polymers as biofilm
carriers and carbon source is new. Polymer in this paper was designed out of the copolymer of
starch and polyvinyl alcohol. Under polluted water with 2 mg/L of perchlorate and 20 mg/L of
NO3-N, it was possible to produce completely denitrification only for 5 h and below the detection
limit to perchlorate within 9 h. Results indicating a significant impact of liquor pH on the biode-
gradation of
but slight effect on nitrate reduction. Packed-bed reactor filled with polymer
granules could remove 2 mg/L perchlorate and 25 mg/L NO3-N completely with influent flow rate
of 1.17 mL/min. Morphological observation indicated the developed biofilm coverage on the outer
surfaces of the carriers was dense and primarily composed of bacillus and coccus. The microbes in
biofilm decomposed polymer, the chink and filament structure on the carrier surface developed,
through metabolism and provided carbon source for them by releasing small organic molecules.
Perchlorate; Nitrate; Biodegradation; Biodegradable Polymers; Biofilm
1. Introduction
Perchlorate (
) in surface and groundwater has become an ever-increasing water quality concern (Sriniva-
san et al., 2009; Baidasa et al., 2011). Nitrate is a well-known water pollutant harmful to human health (Bau-
chard et al., 1992). Specially, nitrate is often a co-contaminant with
due to fertilizer application or explo-
sives. As methods for effective remediation of perchlorate and nitrate are sought, the most promising techniques
appear to involve use of bacteria that respire and degrade perchlorate and nitrate (Coates et al., 2004; Coates et
al., 2000; Wallace et al., 1998; Herman et al., 1999). It has been found that many perchlorate respiring bacteria
*Corresponding author.
F. He et al.
are also capable of reducing nitrate, but it has not been yet clarified whether the reduction of perchlorate and ni-
trate is catalyzed by a single reductase (Xu et al., 2003, 2004; Choi et al., 2008).
It is known that organic carbon is needed as the electron donor in the process of reduction of perchlorate and
nitrate (Shrout et al., 2006; Ghosh et al., 2011; Zhou et al., 2009). However, electron donors are extremely in-
sufficient in perchlorate- and nitrate-contaminated groundwater. Therefore, an exogenous electron donor must
often be added in significant quantities (at significant cost). The challenge of in situ perchlorate and nitrate re-
mediation is to provide an effective electron donor source for bacteria that respires perchlorate and nitrate.
This work was to evaluate the feasibility of starch/ polyvinyl alcohol (PVA) polymer as the carbon source and
the only physical support for microorganisms for synchronous removing nitrate and perchlorate. In addition, the
changes of biofilm morphology and microbiology community on the carrier were also investigated before and
after removing nitrate and perchlorate cultivation. The results may give us the insight into the synergistic inte-
raction, dynamics in degradation activity of the microbial community on the biodegradable polymer.
2. Materials and Methods
2.1. Materials
The synthetic groundwater composition was consisted of deionized water supplemented with 10 mg/L KH2PO4
(as P), 50 mg/L NH4Cl (as N), 20 mg/L NaNO3 (as N), 2 mg/L NaClO4 (as
), 10 mL trace metal solution.
All chemicals used were of ACS grade. Working standards were prepared daily from the stock solution. The
biodegradable particles were produced by an extrusion process and were a copolymer of starch and PVA mate-
rials. The product was insoluble in water and would not lose its strength in the water for a long time. The main
characteristics of the carriers are given in Table 1.
2.2. Instruments
To each reactor, 30 g polymer carrier with perchlorate and nitrate biofilm and 100 ml of synthetic groundwater
were added and then incubated. Batch experiments were performed using glass reactors placed on water-bath
shakers with adjustable water temperatures. Flasks were sealed by rubber plugs to maintain anoxic condition.
The packed bed reactor used in this study was an upflow column. A schematic representation of the experimen-
tal setup was shown in Figure 1.
Polymer granules were used as support media for biofilm growth and packed the column up to a height of 30
cm. Synthetic groundwater mixed with mature activated sludge was pumped at a flow rate of 1.80 mL/min and
flew into the bottom of column, which was recirculated for about 7 days until microbial films on the granules
formed and became gradually thicker. And then starch/PVA granules packed bed reactor began the operation.
2.3. Analytical Methods
The concentration of
was determined using an ion chromatograph (Dionex, ICs2000) equipped with a
suppressed conductivity detector, an AS20 column, an AG20 guard column. The analysis of
was made
using a mobile phase of 35 mM of NaOH (flow rate 1 mL/min). For the determination of
, the mobile
phase (flow rate 1 mL/min) was a 5 mM solution of NaOH.
Table 1. Main characteristics of the starch/PBS polymer carriers.
Parameter Characteristics and value
Material Starch 60%: PVA 40% composite
Color Light yellow
Diameter 3.0 mm
Height 3.0 mm
Densit y 1 .2 2kg/m3
Draw intensity ≥15 MPa
Specific surface area 1735 m2/m3
F. He et al.
Figure 1. Process scheme of pac ked-bed reactor (1) in-
fluent reservoir (2) pump (3) glass wool (4) column (5)
effluent tank.
3. Results and Discussion
3.1. Simultaneous Removal Performance of
in the Polymer Bioreactor
The microcosm degradation curves of
and NO3 -N spiked into bioreactor are illustrated in Fig ure 2.
The Starc h/PVA biofilm reactor was treated at the initial ClO4- concentration of 2 ppm and NO3-N concentra-
tion of 20 ppm, corresponding to the nitrate concentration at a typical perchlorate-contaminated site. Indicating
rapid decrease at the initial period, NO3-N dropped to 0.11 mg/L after 4 h from the spiked concentration of 20
mg/L and was totally disappeared after running for 5 h. Compared to NO3-N, the degradation of
place in a manner much slower. After running for 5 h, the residual
in the reactor fell only to about 500
μg/L, a much higher l e ve l. Complete disappearance of the spiked
was noticed in association with the
data point after running for 9 h.
3.2. Effect of Influent pH
To examine the effect of the pH of the water sample on the reduction of perchlorate and nitrate in the bioreactor,
a series of experiments were performed by changing the pH of the water samples from 5 to 10.0, as shown in
Figure 3.
The results indicated that the optimal pH of perchlorate and nitrate was pH 6.7. The influent pH had signif i-
cant influence on perchlorate reduction but has sli gh t effect on nitrate reduction, which may be attributed to tha t
denitrification biofilm on polymer surface can tolerate a certain pH shock and perchlorate reduction is affected
by many factors. Owing to the density structure of the biofilm on starch/PVA polymer surface, it protected the
internal degradation bacteria and could not lead to significant removal decrease.
3.3. Performance of the Packed Bed Bioreactor
Afte r the end of start-up period (for 40 days), the flow rate was changed to 1.17 mL/min and the influent per-
chlorate and nitrate was removed completely (Figure 4). During the following period, the perchlorate and nitrate
removal varied in the range of 84% - 100% and 97% - 100%, respectively, while the nitrite concentration re-
mained between 0.004 and 0.015 mgNO2-N/L. Except one sample on the 70th day effluent nitrite was as high as
0.26 mgNO2-N/ L.
After the effluent perchlorate and nitrate changed steadily, the effluent DOC level (ca.10 mg/L) became rela-
tive stable. The above results demonstrated clearly that packed bed reactor filled with starch/PVA polymer gra-
nules could effectively and synchronously remove perchlorate and nitrate from drinking water.
F. He et al.
Figure 2. Concentration profiles of
NO3-N operated by spiking 2 mg/L of
and 20
mg/L of NO3-N.
Figure 3. Effect of pH on nitrate and perchlorate degradation.
(a) (b)
Figure 4. (a) Concentration profiles of DOC and perchlorate in effluent in polymer bi oreact or;
(b) Concentration profiles of nitrite and nitrate in effluent in polymer bi oreacto r.
3.4. Biofilm Development and Changes of PBS St ru c t u re
Figure 5(a) showed biofilm coverage on the outer surfaces of the carriers was dense, which had a good layered
structure and primarily composed of bacillus and coccus.
Due to the subsequent degradation of the carrier material the diameter decreased by inches over the cultivation
05 10
0. 0
0. 5
1. 0
1. 5
2. 0
( mg /L)
0 2 4 6 810
NO3-N(mg/ L )
F. He et al.
(a) (b) (c)
Figure 5. The biofilm morphology on starch/PVA polymer surface (a). The surface morphology of raw (b) and used (c) ma-
terial of starch/PV A polymer after cultivation.
time. Especially during the experimental phase the chink and filament structure on the carrier surface developed,
the surface of the raw material was oppositely smooth and had no chink and filament. The deepness of the pores
reached several hundred micrometers and, thus, provided space for anoxic and anaerobic microbial activity. In-
side the pores of the carrier large amounts of bacteria could be detected.
The results indicated that after biofilm formed, the microorganisms in biofilm decomposed PBS through me-
tabolism and provided carbon source for themselves by releasing small organic molecules, which causing the
changes of PBS surface morphology.
4. Conclusion
The results presented clearly show that the biodegradable polymers process allows for a simultaneous removal
of perchlorate and nitrate from contaminated drinking water to below their recommended limits, without sec-
ondary c o ntami nat ion. The results showed that complete denitrifi cation only for 5 h and below the detection
limit of perchlorate within 9 h occured at a typical perchlorate-contaminated simulate reactor. Morphological
observation indicated the developed biofilm coverage on the outer surfaces of the carriers was dense and primar-
ily composed of bacillus and coccus. The microbes in biofilm decomposed polymer, the chink and filament
structure on the carrier surface developed, through metabolism and provided carbon source for them by releas-
ing small organic molecules.
This work was financially supported by the National Natural Science Foundation of China (No. 21107031), the
Doctor Foundation of Shandong Province, China (No. BS2010HZ003, BS2010HZ004), and the Project of Jinan
Science and Technology Board (No. 201202261).
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