Published in J. Environ. Qual. 32:1650-1657 (2003).
© 2003 ASA, CSSA, SSSA
677 S. Segoe Rd., Madison, WI 53711 USA
TECHNICAL REPORTS
Bioremediation and Biodegradation
Removal of Selenate in Simulated Agricultural Drainage Water by a Rice Straw Bioreactor Channel System
Yiqiang Zhang and
William T. Frankenberger, Jr.*
Department of Environmental Sciences, University of California, Riverside, CA 92521-0424
* Corresponding author (williamf{at}orange.ucr.edu).
Received for publication September 30, 2002.
 |
ABSTRACT
|
|---|
Removal of selenium (Se) from agricultural drainage water is important in protecting wetland wildlife. Three flow-through bioreactor channel systems (BCSs), each with three channels filled with rice (Oryza sativa L.) straw, were set in the laboratory to determine removal of selenate [Se(VI)] (1020 µg L-1) from drainage water with a salinity of 10.4 dS m-1, a pH of 8.1, and a nitrate 
range of 0 to 100 mg L-1. Results showed that the rice straw effectively reduced Se(VI) during 122 to 165 d of the experiments. Calculation of Se mass in the three BCSs showed that 89.5 to 91.9% of the input Se(VI) was reduced to red elemental Se [Se(0)], where 96.6 to 98.2% was trapped in the BCSs. Losses of each gram of rice straw were almost equal to the removal of 1.66 mg of Se from the drainage water as a form of red Se(0), indicating that rice straw is a very effective organic source for removing Se(VI) from drainage water.
Abbreviations: BCS, bioreactor channel system • SS, sampling site
|
INTRODUCTION
|
|---|
INTRODUCTION INTO NEARBY wetlands of high-selenium (Se) drainage water from the western San Joaquin Valley of California has created serious hazards to wetland waterfowl (Presser and Ohlendorf, 1987; Ohlendorf, 1989). Removing Se from drainage water before it reaches wetlands would protect wetland wildlife. In aquatic systems, Se can exist in four oxidation states (-II, 0, IV, and VI). Because of the insolubility character of elemental Se [Se(0)], reduction of selenate [Se(VI)] to Se(0) is considered a useful technique for bioremediation. Many studies have showed that bacteria are capable of reducing Se(VI) to Se(0) (Francisco et al., 1992; Lortie et al., 1992; Cantafio et al., 1996; Losi and Frankenberger, 1997; Oremland et al., 1999). In these studies, bacteria use Se(VI) as a terminal electron acceptor for anaerobic respiration and use carbon sources (i.e., acetate, lactate, and glucose) as electron donors. However, the high cost makes it less practical to use these chemicals as electron donors and carbon sources for bacteria to reduce Se(VI) to Se(0) in field conditions (Cantafio et al., 1996). Therefore, it is important to search for alternative economical organic sources as electron donors and carbon sources for bacteria to reduce Se(VI) to Se(0).
Organic amendments to Se-contaminated soil and sediment have enhanced the immobilization of Se. For example, Camps Arbestain (1998) used straw as an organic source to increase immobilization of soluble Se in a soil–plant system and Tokunaga et al. (1996) added cuttings of soft chess (Bromus hordeaceus L.) leaves and stem into sediment to enhance the reduction of soluble Se(VI) to Se(0). In bioremediation of Se-contaminated agricultural drainage water, Bledsoe et al. (1999) used whey, a food-industry waste product, to produce acetate, an essential electron donor for the bacterium Thauera selenatis to efficiently reduce Se(VI) to Se(0). Gerhardt et al. (1991) used the algal biomass as an electron donor and carbon source for bacteria to reduce NO-3 to N2 and Se(VI) to Se(0). In these drainage water treatment systems, more attention has been paid to the reduction of Se(VI) to Se(0) than to removal of Se(0) from drainage water through flocculation and/or precipitation. In a pilot-scale Se bioremediation system study conducted by Cantafio et al. (1996) in the San Joaquin Valley, CA, they found that microbial Se(VI) reduction to Se(0) proceeded rapidly in a series of four columns filled with Jaeger (Houston, TX) Tri-Packs and/or silica sand. About 98% of Se(VI) and Se(IV) in agricultural drainage water were reduced. However, flocculation and precipitation of Se(0) formed in the column proceeded very slowly. Most of the Se(0) flowed out of the columns. At Days 184 and 186, Se(0) accounted for 91 to 96% of total Se in the outflow water. If Se(0) flows out of a treatment system to wetland areas, it could be directly available to biota living in the water, and indirectly available to biota by its oxidation to inorganic Se(IV) and Se(VI) (Luoma et al., 1992; Dowdle and Oremland, 1998; Schlekat et al., 2000). Therefore, a flocculation and/or precipitation reactor is needed in Cantafio's treatment system to remove Se(0) in drainage water after it flows out of Se(VI) reduction columns.
In a recent study, Zhang and Frankenberger (2003a) used air-dried rice straw as an economical organic source and a carrier of Se(VI)-reducing bacteria to remove Se(VI) from drainage water. We characterized the removal process of Se(VI) from drainage water by bacterial reduction of Se(VI) to Se(0), followed by flocculation and/or precipitation of Se(0) to the bottom of the treatment system and the surface of rice straw.
The purpose of this study was to design an effective flow-through bioreactor channel system (BCS) using rice straw to remove Se(VI) from drainage water via reduction to Se(0), and trapping the Se(0) in the BCS. The efficiency of Se(VI) removal was estimated by calculating Se mass in each BCS.
|
MATERIALS AND METHODS
|
|---|
Rice straw is an important source of carbon and nutrients. In a study on the decomposition of rice straw, Villegas-Pangga et al. (2000) reported that rice straw contains an average of 33% carbon with a carbon to nitrogen ratio of 44 in 20 rice varieties. Air-dried rice straw from the Broadview Water District, CA, was used in this study without post-treatment. The rice straw contained 0.412 mg kg-1 of total Se and 0.346 mg kg-1 of soluble Se. To keep the same salt concentrations in the three BCSs during the experiments, artificial drainage water with a salinity (electrical conductivity [EC]) of 10.4 dS m-1 and a pH of 8.1 was used. This artificial drainage water contained the major elements present in agricultural drainage water: SO2-4 (5000 mg L-1), Cl- (1500 mg L-1), HCO-3 (300 mg L-1), Ca2+ (550 mg L-1), Mg2+ (300 mg L-1), and Na+ (2285 mg L-1). Trace elements normally found in drainage water were not included, except for Se. Before mixing the chemical solutions, each chemical (NaCl, Na2SO4, NaHCO3, CaCl2, and MgSO4) was dissolved separately in deionized water and autoclaved (0.124 MPa [18 lb in-2] at 121°C) for 20 min. Selenium standard solutions [Se(VI), 10000 mg L-1 and NO-3, 10000 mg L-1] were passed through a sterile 0.2-µm membrane filter before they were added to the drainage water. The Se(VI) concentration in the artificial drainage water was 1020 µg L-1 and NO-3 was varied from 0 to 100 mg L-1 as detailed below.
Bioreactor Channel System
The flow-through BCS used in this study consisted of three units (Fig. 1)
. A large flask containing the artificial drainage water was connected by plastic tubing to a multichannel peristaltic pump (Thermo Orion, Beverly, MA). The drainage water was pumped through the bioreactor system consisting of three channels. The channels were made by placing 10, 10, and 50 g of rice straw into three 500-mL semitransparent plastic bottles. At each channel outlet, a 60-mL plastic bottle used as a sampling site (SS) was connected with transparent tubing. The water volume was 485 mL in Channels 1 and 2, 300 mL in Channel 3, and about 50 mL in each SS.
The BCS was designed to remove Se(VI) from drainage water through reduction to Se(0) and to trap Se(0) with rice straw when soluble Se(VI) passed though the channels. The Se(VI)-reducing bacteria in the rice straw used Se(VI) as a terminal electron acceptor for anaerobic respiration and used the organic materials of rice straw as an electron donor (Zhang and Frankenberger, 2003a). Channels 1 and 2 were the Se(VI) reduction and Se(0) precipitation sites. Channel 3 was designed as a reduction and filtration zone in which soluble Se(VI) from Channel 2 could be further reduced to Se(0) and unprecipitated Se(0) from Channels 1 and 2 could be trapped.
Flow-Through Experiments
A slow-moving flow (30 mL d-1, 16.2 d of residence time in Channels 1 and 2 and 10 d in Channel 3) of drainage water was set in two BCSs (1 and 2) at the beginning of the experiments. The idea behind this setting was the thought that Se(VI)-reducing bacteria might grow well in slow-moving water. In BCS 1, drainage water without added NO-3 was passed through the channels at a rate of 30 mL d-1. The flow rate was adjusted to 250 mL d-1 at Day 28 for the rest of the experiment. In our previous batch study on the removal of Se(VI) from drainage water using rice straw (Zhang and Frankenberger, 2003a), more than 90% of Se(VI) was reduced to Se(0) during the first 5 d of the experiments. A flow rate of 250 mL d-1 (1.94 d of residence time in Channels 1 and 2 and 1.2 d in Channel 3) in a BCS would result in the reduction of input Se(VI) to Se(0). In BCS 2, drainage water with 60 mg L-1 of added NO-3 was passed through the channels at a rate of 30 mL d-1. The flow rate was adjusted to 250 mL d-1 at Day 77 for the rest of the experiment. In BCS 3, the flow rate of drainage water without NO-3 was 250 mL d-1 at the beginning of the experiment. At Day 95, drainage water containing 100 mg L-1 of NO-3 was used to pass through the channels until the last day of the experiment. All of the BCSs were run at room temperature (21 ± 1°C). Water samples at each SS were collected at 2-d intervals for total Se [total soluble Se plus unprecipitated Se(0)] and total soluble Se analysis. Selenium speciation samples were randomly collected several times at Days 38, 71, 93, 121, and 145 in BCS 1, at Days 83, 105, 133, and 157 in BCS 2, and at Days 28, 50, 64, 92, and 116 in BCS 3. Redox potential and pH in the SSs were measured three times during the experiments at Days 38, 121, and 145 in BCS 1, Days 83, 133, and 157 in BCS 2, and Days 64, 92, and 116 in BCS 3. Nitrate concentration was measured one time at Day 105 in BCS 2.
Analysis
Selenium species in drainage water were determined by a method developed by Zhang and Frankenberger (2003a). Selenium species included total Se, total soluble Se, Se(VI), Se(IV), unprecipitated Se(0) [Se(0) that remains in the water before precipitation to the bottom], and organic Se(-II). In brief, soluble Se speciation, after removing unprecipitated Se(0) from solution by centrifugation for 10 min at 12000 rpm, was performed as follows. First, Se(IV) in the water samples was determined in a pH 7 buffer solution. The sum of Se(IV) and organic Se(-II) was determined when the organic Se in the water samples was oxidized to Se(IV) by K2S2O8, which was indicated by precipitation of Mn oxides formed from the oxidation of added Mn2+. The organic Se(-II) concentration was calculated as the difference between Se in this water sample and Se(IV) concentration determined in another subsample. Total soluble Se in the water samples was determined by oxidizing all Se to Se(VI) by K2S2O8, followed by reduction to Se(IV) in 6 M HCl. The Se(VI) concentration was calculated as the difference between total soluble Se concentration and sum of Se(IV) and organic Se(-II) concentration determined in another subsample. Total Se [sum of total soluble Se and unprecipitated Se(0)] in the water samples was determined using the same procedure as total soluble Se. Unprecipitated Se(0) concentration was calculated as the difference between total Se and total soluble Se. Selenium concentrations in prepared solutions were analyzed by hydride generation atomic absorption spectrometry (HGAAS) (Zhang et al., 1999a,b). The equations for calculating mass of Se in the BCSs are presented in Table 1. Nitrate in the water samples was determined using a steam distillation method (Keeney and Nelson, 1982).
A 720A pH/ISE meter (Thermo Orion) was used to measure pH and redox potential (Eh) in the experimental flasks. The pH was measured using an Accumet pH combination electrode (Fisher Scientific, Pittsburgh, PA). The redox potential was measured with an Accumet combination platinum electrode (Ag/AgCl). The measured potential (Ehmeasured) was converted to potential in the rice straw solution (Ehactual) relative to a standard H electrode as follows (Jayaweera and Biggar, 1996): Ehactual = Ehmeasured + 224.4 mV.
|
RESULTS
|
|---|
Selenate Removal in Bioreactor Channel System 1
The removal of Se from drainage water without added NO-3 in BCS 1 is illustrated in Fig. 2
. At SS 1, total soluble Se in the drainage water ranged from 167 to 221 µg L-1 during the first 28 d at a low flow rate of 30 mL d-1. When the flow rate of drainage water was adjusted to 250 mL d-1 at Day 28, total soluble Se increased with time to 737 µg L-1 at Day 34, followed by a decrease to less than 100 µg L-1 at Day 40. Total soluble Se fluctuated around 150 µg L-1 during the next 50 d and then gradually increased to a range of 400 to 800 µg L-1. Unprecipitated Se(0) was relatively low during the experiment, ranging from 1 to 275 µg L-1 with an average of 68.6 µg L-1.
View larger version (27K):
[in this window]
[in a new window]
|
Fig. 2. Total soluble Se and unprecipitated Se(0) in drainage water at different sampling sites (SSs) in Bioreactor Channel System (BCS) 1. Inserted small figures show accumulated Se(0) in each channel. Unit of Eh is mV.
|
|
At SS 2, total soluble Se in the drainage water was relatively high, ranging from 307 to 606 µg L-1 during Days 32 to 38. It was less than 100 µg L-1 most of the time over the next 53 d and gradually increased to a range of 200 to 500 µg L-1. Unprecipitated Se(0) ranged from 0.2 to 163 µg L-1 with an average of 47.9 µg L-1 during the experiment.
At SS 3, total soluble Se in the drainage water was relatively high, ranging from 288 to 522 µg L-1 during Days 34 to 38. It was less than 50 µg L-1 during the rest of the experiment. Unprecipitated Se(0) ranged from 0.4 to 73.5 µg L-1 with an average of 17.7 µg L-1 during the experiment.
During the 151 d of the experiment, the pH of the drainage water ranged from 6.5 to 7. Redox potential was -33 to -62 mV in SS 1, -71 to -103 mV in SS 2, and -90 to -124 mV in SS 3. Selenate and organic Se(-II) were the major forms of soluble Se in the drainage water, ranging from 0.4 to 442 and 6 to 96.5 µg L-1, respectively. The Se(IV) was 0 to 19.4 µg L-1 (Fig. 3) .
View larger version (37K):
[in this window]
[in a new window]
|
Fig. 3. Soluble Se species in drainage water at different sampling sites (SSs) in three bioreactor channel systems (BCSs).
|
|
Selenate Removal in Bioreactor Channel System 2
The removal of Se from the drainage water containing 60 mg L-1 of NO-3 in BCS 2 is shown in Fig. 4
. At SS 1, total soluble Se in the drainage water ranged from 84.9 to 259 µg L-1 during the first 77 d, at a low flow rate of 30 mL d-1. When the flow rate of drainage water was adjusted to 250 mL d-1 at Day 78, total soluble Se increased to 951 µg L-1 by Day 87, with a decrease to 243 µg L-1 at Day 129. In the rest of the experiment, total soluble Se ranged from 304 to 788 µg L-1. Unprecipitated Se(0) was less than 100 µg L-1 most of the time, with an average of 52.7 µg L-1.
View larger version (28K):
[in this window]
[in a new window]
|
Fig. 4. Total soluble Se and unprecipitated Se(0) in drainage water with 60 mg L-1 of NO-3 at different sampling sites (SSs) in Bioreactor Channel System (BCS) 2. Inserted small figures show accumulated Se(0) in each channel. Unit of Eh is mV.
|
|
At SS 2, total soluble Se in the drainage water was less than 140 µg L-1 during the first 77 d of the experiment. It increased to 584 µg L-1 at Day 87, with a decrease to 65.3 µg L-1 at Day 91. Total soluble Se gradually increased from 74.7 at Day 93 to a range of 150 to 407 µg L-1 during the rest of the experiment. Unprecipitated Se(0) was less than 100 µg L-1 most of the time, with an average of 40.9 µg L-1.
At SS 3, total soluble Se in the drainage water was less than 80 µg L-1 during the first 77 d of the experiment. It increased to 433 µg L-1 at Day 87, with a decrease to 41.6 µg L-1 at Day 93. During the rest of the experiment, total soluble Se ranged from 32.5 to 91.7 µg L-1. Unprecipitated Se(0) ranged from 1.01 to 78.4 µg L-1, with an average of 20.3 µg L-1.
During the 165 d of the experiment, the pH of the drainage water ranged from 6.2 to 7.1. Redox potential differed among the SSs, with 30 to -4 mV in SS 1, 3 to -31 mV in SS 2, and -92 to -103 mV in SS 3. At Day 105 of the experiment, NO-3 concentration was 4.01, 3.54, and 1.54 mg L-1, respectively, in SS 1, SS 2, and SS 3. Selenate was the dominant form of soluble Se in the drainage water, ranging from 9.9 to 609 µg L-1 with a low range of Se(IV) (0–41 µg L-1) and organic Se(-II) (3–52.4 µg L-1) (Fig. 3).
Selenate Removal in Bioreactor Channel System 3
The removal of Se from the drainage water in BCS 3 is presented in Fig. 5
. At SS 1, total soluble Se in drainage water was high, ranging from 1007 to 1030 µg L-1 during the first 7 d, at a flow rate of 250 mL d-1. It decreased to 107 at Day 11. During Days 13 to 92, total soluble Se fluctuated in a range of 50.7 to 206 µg L-1. When drainage water containing 100 mg L-1 of NO-3 was used at Day 92, total soluble Se increased to a range of 163 to 493 µg L-1 in the rest of the experiment. Unprecipitated Se(0) ranged from 0 to 374 µg L-1 with an average of 112 µg L-1 during the experiment.
View larger version (27K):
[in this window]
[in a new window]
|
Fig. 5. Total soluble Se and unprecipitated Se(0) in drainage water at different sampling sites (SSs) in Bioreactor Channel System (BCS) 3. Inserted small figures show accumulated Se(0) in each channel. Unit of Eh is mV.
|
|
At SS 2, total soluble Se in the drainage water was high in the first 8 d, ranging from 905 to 1031 µg L-1. It was less than 100 µg L-1 most of the time from Days 13 to 92. Total soluble Se increased to a range of 70 to 226 µg L-1 from Day 92 to the end of the experiment. Unprecipitated Se(0) ranged from 0 to 335 µg L-1, with an average of 70 µg L-1.
At SS 3, total soluble Se in the drainage water decreased from 1010 to 72.2 µg L-1 in the first several days. It ranged from 15.4 to 62.9 µg L-1, with an average of 29.4 µg L-1 during the rest of the experiment. Unprecipitated Se(0) ranged from 0.11 to 118 µg L-1, with an average of 33.9 µg L-1.
During the 122 d of the experiment, the pH of the drainage water ranged from 6.2 to 7. Redox potential ranged from 13 to -83 mV in SS 1, 15 to -85 mV in SS 2, and -1 to -109 mV in SS 3. The Se(VI) was 2.1 to 463 µg L-1 in the drainage water, with a low range of Se(IV) (0–14.2 µg L-1) and organic Se(-II) (8.2–62.6 µg L-1) (Fig. 3).
|
DISCUSSION
|
|---|
Many scientists have reported that bacterial reduction of Se(VI) to Se(0) is a useful technique for removing Se from agricultural drainage water (Cantafio et al., 1996; Oremland et al., 1999; Zhang and Frankenberger, 2003a). In a recent batch study on the removal of Se(VI) from drainage water by rice straw, Zhang and Frankenberger (2003a) reported that the removal process of Se(VI) was comprised of bacterial reduction of Se(VI) to Se(0) and flocculation and/or precipitation of Se(0) to the bottom of the treatment systems and to the surface of the rice straw. The present study showed that a large amount of Se(VI) also was removed from the drainage water through Se(VI) reduction to Se(0) and the trapping of Se(0) in the flow-through BCSs, as evident by the red precipitates at the bottom, on the inner wall of the experimental bottles, and on the surface of rice straw.
A reducing environment was effectively created in the BCSs, as shown by a rapid decrease in redox potential from a high reading of 400 to 500 mV in the input drainage water to a low reading of -1 to -124 mV in Channel 3. At low levels of redox potential in drainage water, bacteria reduced NO-3 and Se(VI) effectively. Nitrate is a competitive electron acceptor affecting Se(VI) reduction because of its similar redox potential in aquatic systems (Masscheleyn and Patrick, 1993). In a batch study on the effect of NO-3 on Se(VI) reduction to Se(0) in drainage water by rice straw, Zhang and Frankenberger (2003b) found that a level of 100 mg L-1 of NO-3 in drainage water had little effect on Se(VI) reduction to Se(0). When the NO-3 concentration was 500 mg L-1, Se(VI) reduction was delayed. In the BCSs, there was only about 2% difference in the percentage of Se(0) formed from drainage water in BCS 2 (with NO-3) and in BCS 1 (without NO-3) (Table 2). A one-time measurement of NO-3 in BCS 2 showed that about 97% of the added NO-3 was removed. When 100 mg L-1 NO-3 drainage water was used at Day 94 in BCS 3, the rate of Se(VI) reduction to Se(0) was reduced significantly in Channel 1, with little effect in Channel 2, and no effect in Channel 3. These results reveal that a range of 60 to 100 mg L-1 of NO-3 in drainage water did not significantly affect Se(VI) reduction to Se(0) in the presence of rice straw.
There was a good correlation between total soluble Se and Se(VI) in the drainage water (Fig. 6)
. However, higher levels of Se(VI) appeared, mostly in Channels 1 and 2, where Se(VI) was not completely reduced. In the outlet of the BCSs (SS 3), Se(VI) was only about 15 µg L-1, except in BCS 1 at Day 38 and BCS 2 at Day 83 just before the flow rate of drainage water was adjusted. These results showed that most input Se(VI) was reduced.
View larger version (20K):
[in this window]
[in a new window]
|
Fig. 6. Relationship between total soluble Se and Se(VI) in drainage water at different sampling sites (SSs) in three bioreactor channel systems (BCSs).
|
|
The major reduced form of Se in the BCSs was Se(0). Calculation of Se mass in the three BCSs showed that about 89.5 to 91.9% of input Se(VI) was reduced to red Se(0) (Table 2). The BCS not only reduced Se(VI) to Se(0), but also trapped Se(0) in the channels. Selenium mass data showed that 42.7 to 68.4% of red Se(0) was precipitated in Channel 1, 11.6 to 31.4% in Channel 2, and 6.91 to 16.1% in Channel 3. Only about 1.68 to 3.13% of Se(0) flowed out of the BCSs during the 122 to 165 d of the experiments.
With active removal of Se(VI) from the drainage water, the amount of rice straw in the BCSs decreased. During the 122 to 165 d of the experiments, about 3.9 to 4.4 g of rice straw was lost in Channel 1, 2.7 to 3.55 g in Channel 2, and 4 to 10 g in Channel 3. The loss of each gram of rice straw meant removal of 2.67 to 5.35 mg of Se in Channel 1, 1.14 to 2.8 mg of Se in Channel 2, and 0.21 to 0.7 mg of Se in Channel 3. During the 122 to 165 d of the experiments in all three BCSs, total trapped Se(0) was 76.15 mg and total lost of rice straw was 45.94 g. Each gram loss of rice straw was almost equal to the removal of 1.66 mg of Se from the drainage water as a form of red Se(0), indicating that rice straw is very efficient at removing Se(VI) from drainage water.
|
CONCLUSIONS
|
|---|
Irrigation in the western part of the San Joaquin Valley, CA, has produced high-salt drainage water containing Se (Sylvester, 1990, p. 119–124), creating serious hazards for wetland waterfowl (Presser and Ohlendorf, 1987; Ohlendorf, 1989). Several remediation methods such as adsorption, microbial reduction, and volatilization have been proposed to remove Se from drainage water (Lee, 1989; Cantafio et al., 1996). However, because of high costs, none of these technologies have been used at full scale in the field to treat Se-contaminated drainage water in California. This study shows that rice straw was very effective at removing Se(VI) from drainage water in a flow-through BCS. During the 122 to 165 d of the experiments, about 89.5 to 91.9% of input Se(VI) was reduced to Se(0), where 96.6 to 98.2% was trapped in the BCS. This is the first time rice straw has been used as an economical organic source and a carrier of Se(VI)-reducing bacteria to remove Se(VI) from sterile artificial drainage water in a rice straw bioreactor channel system. Complicated natural drainage water and field conditions may affect the removal of Se(VI). In future studies, we will use rice straw directly to treat natural Se(VI)-contaminated drainage water in a series of replicated experiments. The BCS may also be improved by extending the length and depth of the channels to increase the residence time of the drainage water in the BCS. Because rice straw is directly available at a low cost in the San Joaquin Valley it is an excellent organic source that can be used to effectively treat Se(VI)-contaminated drainage water.
|
ACKNOWLEDGMENTS
|
|---|
We thank Dr. Zahir A. Zahir of the University of California, Riverside, for reviewing this manuscript. The research was funded by the UC Salinity and Drainage Program.
|
REFERENCES
|
|---|
- Bledsoe, T.L., A.W. Cantafio, and J.M. Macy. 1999. Fermented whey—An inexpensive feed source for a laboratory-scale selenium-bioremediation reactor system inoculated with Thauera selenatis. Appl. Microbiol. Biotechnol. 51:682–685.[ISI][Medline]
- Camps Arbestain, M. 1998. Effect of straw amendment and plant growth on selenium transfer in a laboratory soil–plant system. Can. J. Soil Sci. 78:187–195.
- Cantafio, A.W., K.D. Hagen, G.E. Lewis, T.L. Bledsoe, K.M. Nunan, and J.M. Macy. 1996. Pilot-scale selenium bioremediation of San Joaquin drainage water with Thauera selenatis. Appl. Environ. Microbiol. 62:3298–3303.[Abstract]
- Dowdle, P.R., and R.S. Oremland. 1998. Microbial oxidation of elemental selenium in soil slurries and bacterial cultures. Environ. Sci. Technol. 32:3749–3755.
- Francisco, A.T., L.L. Barton, C.L. Lemanski, and T.G. Zocco. 1992. Reduction of selenate and selenite to elemental selenium by Wolinella succinogenes. Can. J. Microbiol. 38:1328–1333.
- Gerhardt, M.B., B.F. Green, R.D. Newman, T.J. Lundquist, B.R. Tresan, and W.J. Oswald. 1991. Removal of selenium using a novel algal-bacterial process. J. Water Pollut. Control Fed. 63:799–805.
- Jayaweera, G.R., and J.W. Biggar. 1996. Role of redox potential in chemical transformations of selenium in soils. Soil Sci. Soc. Am. J. 60:1056–1063.[Abstract/Free Full Text]
- Keeney, D.R., and D.W. Nelson. 1982. Nitrogen—Inorganic forms. p. 649–658. In A.L. Page, R.H. Miller, and D.R. Keeney (ed.) Methods of soil analysis. Part 2. 2nd ed. Agron. Monogr. 9. ASA and SSSA, Madison, WI.
- Lee, E.W. 1989. Current options in treatment of agricultural drainage wastewater. p. 33–45. In M.E. Huntley (ed.) Biotreatment of agricultural wastewater. CRC Press, Boca Raton, FL.
- Lortie, L., W.D. Gould, S. Rajan, R.G.L. McCready, and K.J. Cheng. 1992. Reduction of selenate and selenite to elemental selenium by a Pseudomonas stutzeri isolate. Appl. Environ. Microbiol. 58:4042–4044.[Abstract/Free Full Text]
- Losi, M.E., and W.T. Frankenberger, Jr. 1997. Reduction of selenium oxyanions by Enterbacter cloacae strain SLDaa-1: Isolation and growth of the bacterium and its expulsion of selenium particles. Appl. Environ. Microbiol. 63:3079–3084.[Abstract]
- Luoma, S.N., C. Johns, N.S. Fisher, N.A. Steinberg, R.S. Oremland, and J.R. Reinfelder. 1992. Determination of selenium bioavailability to a bivalve from particulate and solute pathways. Environ. Sci. Technol. 26:485–491.
- Masscheleyn, P.H., and W.H.J. Patrick. 1993. Biogeochemical processes affecting selenium cycling in wetlands. Environ. Toxicol. Chem. 12:2235–2243.
- Ohlendorf, H.M. 1989. Bioaccumulation and effects of selenium in wildlife. p. 133–177. In L.W. Jacobs (ed.) Selenium in agriculture and the environment. ASA and SSSA, Madison, WI.
- Oremland, R.S., J.S. Blum, A.B. Bindi, P.R. Dowdle, M. Herbel, and J.F. Stoltz. 1999. Simultaneous reduction of nitrate and selenate by cell suspensions of selenium-respiring bacteria. Appl. Environ. Microbiol. 65:4385–4392.[Abstract/Free Full Text]
- Presser, T.S., and H.M. Ohlendorf. 1987. Biogeochemical cycling of selenium in the San Joaquin Valley, California, USA. Environ. Manage. 11:805–821.
- Schlekat, C.E., P.R. Dowdle, B.G. Lee, S.N. Luoma, and R.S. Oremland. 2000. Bioavailability of particle-associated selenium to the bivalve Potamocorbila amurensis. Environ. Sci. Technol. 34:4504–4510.
- Sylvester, M.A. 1990. Overview of the salt and agricultural drainage problem in the western San Joaquin Valley, California. Circ. 1033c. U.S. Geol. Survey, Reston, VA.
- Tokunaga, T.K., I.J. Pickering, and G.E. Brown, Jr. 1996. Selenium transformation in ponded sediment. Soil Sci. Soc. Am. J. 60:781–790.[Abstract/Free Full Text]
- Villegas-Pangga, G., G. Blair, and R. Lefroy. 2000. Measurement of decomposition and associated nutrient release from straw (Oryze sativa L.) of different rice varieties using a perfusion system. Plant Soil 223:1–11.
- Zhang, Y.Q., and W.T. Frankenberger, Jr. 2003a. Characterization of selenate removal from drainage water using rice straw. J. Environ. Qual. 32:441–446.[Abstract/Free Full Text]
- Zhang, Y.Q., and W.T. Frankenberger, Jr. 2003b. Factors affecting removal of selenate in agricultural drainage water utilizing rice straw. Sci. Total Environ. 305:207–216.[Medline]
- Zhang, Y.Q., W.T. Frankenberger, Jr., and J.N. Moore. 1999a. Measurement of selenite in sediment extracts by using hydride generation atomic absorption spectrometry. Sci. Total Environ. 229:183–193.
- Zhang, Y.Q., J.N. Moore, and W.T. Frankenberger, Jr. 1999b. Speciation of soluble selenium in agricultural drainage waters and aqueous soil-sediment extracts using hydride generation atomic absorption spectrometry. Environ. Sci. Technol. 33:1652–1656.
Related articles in JEQ:
- This Issue in Journal of Environmental Quality
JEQ 2003 32: 1577-1582.
[Full Text]
TOP
ABSTRACT
INTRODUCTION
