The effects of various amendments on the biostimulation of perchlorate reduction in laboratory microcosm and flowthrough soil columns

Chemical Engineering Journal 232 (2013) 388–396

Contents lists available at ScienceDirect

Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej

The effects of various amendments on the biostimulation of perchlorate reduction in laboratory microcosm and flowthrough soil columns Yue Wang a, Liyan Jin a, Marc A. Deshusses b,⇑, Mark R. Matsumoto a,⇑ a b

Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521, USA Department of Civil and Environmental Engineering, Duke University, Box 90287, Durham, NC 27708, USA

h i g h l i g h t s  Three amendments to biostimulate perchlorate reduction were investigated.  Experiments were conducted in microcosms and flowthrough biobarrier columns.  Water and soil used were from an actual contaminated site.  Two commercial amendments proved effective, a compost/mulch mixture showed mixed results.  Overall, the results should support better site remediation decisions.

a r t i c l e

i n f o

Article history: Received 30 May 2013 Received in revised form 14 July 2013 Accepted 18 July 2013 Available online 27 July 2013 Keywords: Perchlorate Bioremediation Biobarrier Biostimulation Nitrate Amendments

a b s t r a c t 

Perchlorate (ClO4 ) is a contaminant of concern in groundwater and drinking water. In the presence of a suitable electron donor, perchlorate can be reduced to non-toxic chloride via either biotic or abiotic mechanisms. The objective of this study was to evaluate a variety of amendments (Emulsified Oil Substrate (EOSÒ598), EHCÒ and a compost/mulch mixture) and supplemental nutrients to stimulate in situ perchlorate bioremediation. Both laboratory microcosm and column experiments were conducted with groundwater from a contaminated site that had an initial perchlorate concentration of about 500 lg/L. Complete perchlorate removal was observed within 5–12 days in all the microcosms. The addition of 1 g/L (NH4)2HPO4 as nutrient increased the reduction rate of perchlorate in EOS and compost/mulch microcosms, but had no effect in the EHC amended microcosms. Two different flowthrough experiments were conducted. Phase 1 used two parallel columns packed with EOS-amended compost/mulch/gravel media and EHC-amended compost/mulch/gravel media, while in Phase 2, a series of varying length columns ranging from 0.15 m to 0.60 m were packed with EOS-amended soil and EHC-amended soil. No perchlorate was detected in the effluent of both EOS- and EHC-amended compost/mulch/gravel columns after 20 days. In Phase 2, no significant treatment difference was observed between the EOS- and EHCamended soil columns. Complete perchlorate removal was observed after 6 to 11 days in all different length columns when they were operated at a hydraulic loading rate of 0.15 m3/m2-d. Perchlorate removal was completely lost in all the columns when the hydraulic loading rate was increased to 0.60 m3/m2-d. Nitrate competed with perchlorate for electrons, and was a preferred acceptor over perchlorate. Overall, based on the results of this study, the two commercial amendments can be considered as effective means for perchlorate bioremediation, although EHC had a shorter period of effectiveness. Ó 2013 Elsevier B.V. All rights reserved.

1. Introduction 

Perchlorate (ClO4 ) has become a commonly detected environmental contaminant in groundwater because of its widespread use in solid oxidants for rockets, fertilizers, and fireworks, etc. [1,2]. Perchlorate is a human health concern due to its interference ⇑ Corresponding authors. Tel.: +1 919 660 5480; fax: +1 919 660 5219 (M.A. Deshusses), tel.: +1 951 827 3197; fax: +1 951 927 3188 (M.R. Matsumoto). E-mail addresses: [email protected] (M.A. Deshusses), mark.matsumoto @ucr.edu (M.R. Matsumoto). 1385-8947/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2013.07.060

with thyroid gland function. In infants and unborn children, inadequate thyroid hormone production can cause mental retardation and thyroid tumors [3]. Although mass production of perchlorate began as early as the 1940s and was first detected in groundwater wells in eastern Sacramento County, California in 1955, it was not categorized as an environmental contaminant until after 2000 [4–6]. Perchlorate contamination has been found throughout the United States, especially in the Southwestern states of Nevada, Utah, and California. Christen [7] reported that the worst contamination was in the

389

Y. Wang et al. / Chemical Engineering Journal 232 (2013) 388–396

Las Vegas, Nevada area, where perchlorate has been manufactured for more than 50 years. Groundwater contamination was discovered at concentrations ranging from 630,000 to 3,700,000 lg/L. Logan reported that perchlorate has been found in 30% of the wells sampled in California, and that concentrations were above the state’s action level of 6 lg/L in 9% of those wells [8]. Many water wells with perchlorate concentrations exceeding the action level have been closed. Alternatively water can be treated via ion exchange, or diluted with perchlorate-free water before distribution. Perchlorate has also been found in milk and lettuce and is subject to biomagnification [9,10]. There are currently no regulatory criteria for perchlorate concentration in drinking water issued by the U.S. Environmental Protection Agency (USEPA). However, an interim health advisory level of 15 lg/L was established in 2009 [11]. Some states have much higher standards; California set a maximum contaminant level (MCL) for perchlorate of 6 lg/L in drinking water in 2002 [12], while Massachusetts MCL is 2 lg/L [13]. In January 2011, the California Office of Environmental Health Hazard Assessment (OEHHA) proposed a 1 lg/L public health goal for perchlorate, with a target implementation date of February 2013. Technologies applicable for treating perchlorate contamination in drinking water and groundwater include ion exchange, membrane technologies (electrodialysis and reverse osmosis), activated carbon adsorption, and bioremediation [14–19]. Among these technologies, ion exchange and membrane technologies are mature technologies for perchlorate treatment. However, these systems generate concentrated perchlorate brines which need further treatment before disposal [19,20]. Bioremediation uses microorganisms capable of reducing perchlorate under anaerobic conditions in the presence of a suitable electron donor. The pathway for perchlorate biological reduction is via the following sequence: 





ClO4 ðperchlorateÞ ! ClO3 ðchlorateÞ ! ClO2 ðchloriteÞ 

! Cl ðchlorideÞ þ O2 The first step is generally the rate limiting step, and thus the final product has been shown to be chloride with little or no residual intermediates [21,22]. For in situ remediation, biological treatment zones can be formed by injecting organic substrates either into the source area or into permeable reactive barriers (PRBs). These organic substrates serve as both carbon and electron donor for microorganism growth and perchlorate reduction during the anaerobic process. Compared to conventional physical or chemical processes, biological remediation has the advantages of low operating and maintenance costs. Also, perchlorate reducing microorganisms have been found to be ubiquitous in the environment; many denitrifying microorganisms are capable to reduce perchlorate [21]. The common electron donors used in the in situ or ex situ bioremediation are vegetable oil, acetate, acetic acid, hydrogen, etc. [23–25]. The objective of this study was to determine the suitability of various organic compounds as electron donors for perchlorate reduction and to determine which compound was most desirable for in situ application. To achieve the objective, Emulsified Oil Substrate (EOSÒ598), EHCÒ and compost/mulch were selected as potential electron donors. EHC is a patented combination of controlled-release, integrated carbon and zero valent iron (ZVI). Utilizing EHC for chlorinated organic such as TCE removal has been proven to be an effective approach [26]. However, the data evaluating the efficiency of EHC for perchlorate removal is very limited. A column study conducted by the manufacturer showed that perchlorate can be reduced from 120,000 lg/L to 9400 lg/L after about 120 days, and then reduced to non-detectable after 400 days [27]. Compared with other commercially available products, EHC can generate a much lower redox potential (Eh) between 500

and 650 mV [28]. The combination of carbon, nutrients and buffer may minimize the addition of other chemicals during the abiotic or biotic treatment process. EOSÒ598 is a food-grade oil/water emulsion enriched with nutrient and that is specially designed to biostimulate anaerobic remediation of chlorinated solvents, perchlorate and nitrate. Finally, compost/mulch is a low-cost material that can serves as electron donor, carbon, and/or nutrient source and often contains a broad variety of pollutant-degrading microorganisms. In this study, microcosm tests were first conducted to evaluate the feasibility and efficiency of these selected organic substrates. These investigations were followed by a series of column tests that simulated treatment in an in situ permeable barrier. 2. Materials and methods 2.1. Materials EOSÒ598 (now renamed EOS PRO) was supplied by EOS Remediation, Inc. It contained 59.8% (by weight) soybean oil. EHC (Adventus Americas) is a substrate that combines a plant-based carbon/energy source to stimulate microbial activity with a zerovalent iron component to rapidly generate and sustain reducing conditions. Nature Scapes Advanced Sierra Red Mulch is 100% wood mulch which was obtained from local Lowe’s store (Riverside, CA). Compost was obtained from the same place. The water and soil used throughout the studies were obtained from an actual perchlorate-contaminated site in southern California. Both the soil and the groundwater were collected near the site boundary; while soil was collected from a depth of 4.5 m. No extraneous bacteria were added to the experiments to better simulate in situ conditions and since it has been shown that soil from contaminated sites can be a source of perchlorate degrading microorganisms. A preliminary test (data not shown) confirmed that perchlorate reducing bacteria were indeed present in the site aquifer materials. The soil composition is summarized in Table 1. The initial perchlorate concentration was 505 lg/L and 26 lg/kg in the groundwater and in the soil, respectively. Compared with the perchlorate concentration in groundwater, the concentration in soil was quite low, consistent with soil’s low adsorption capacity for perchlorate. Groundwater pH was 7.7, which is favorable for biological perchlorate treatment [29,30]. The total organic carbon (TOC) concentrations were 1.01 mg/L in groundwater sample and <10.7 mg/kg in the soil. These levels are low and not favorable for biological

Table 1 Composition of the perchlorate contaminated water and soil.

Perchlorate pH (unitless) Total Organic Carbon Hardness (as CaCO3) Total dissolved solids Total Kjeldahl Nitrogen Nitrate (as N) Total phosphorus Total sulfur Chloride Sulfate Calcium Magnesium Potassium Sodium Arsenic Iron Manganese –: Not analyzed.

Water sample (mg/L)

Soil sample (mg/kg)

0.505 7.71 1.01 242 990 0.35 8.2 0.0245 58.5 186 176 81.0 9.64 0.733 240 <0.0400 <0.0400 <0.0300

0.026 9.00 <10.7 – – 48.6 – 0.278 – – 40.6 – – – – <4.29 13,900 231

390

Y. Wang et al. / Chemical Engineering Journal 232 (2013) 388–396

activity, and thus additional organics needed to be added. Dissolved oxygen (at the time of the experiments, but not representative of field conditions) was on average 6 mg/L. The presence of nitrate (8.2 mg/L as N) in the groundwater was expected to compete with perchlorate for the electron donor and organic carbon. Low levels of Total Kjeldahl Nitrogen (TKN) and phosphorus in the water sample were considered to be possibly inadequate to support bacterial growth. For this reason, the effect of nutrient amendment was investigated in the microcosm experiments.

Table 3 Summary of column operation conditions.

Phase 1a  Site soil (control)  EHCc-amended compost/mulch/ gravel  EOSd-amended compost/mulch/ gravel Phase 2b  Site soil (control)  EHCc-amended soil  EOSd-amended soil

2.2. Microcosm procedures and methods A summary of microcosm testing conditions is shown in Table 2. All experiments were conducted in 250 mL glass serum bottles. Soil and groundwater were added into each bottle at a ratio of 1:4 (w/w) with the exception of the set with compost/mulch as the amendment, where soil was replaced by compost and mulch mixture. EOS and EHC were blended with the soil at dosages of 0.3% (w/w) and 0.1% (w/w), respectively. These dosages are recommended by the manufacturer and do not correspond to the same amount of electrons. Compost and mulch was mixed at a ratio of 2:3 (v/v). As previously mentioned, perchlorate reduction experiments were performed with and without nutrient addition: 1 g/L of diammonium phosphate ((NH4)2HPO4) was added to the groundwater in half the microcosms. Controls were prepared without any amendment addition to quantify the natural perchlorate reduction or abiotic loss. All the bottles were sealed with a septum cap, and the headspace was purged with nitrogen gas before starting the experiment to purge oxygen from the headspace. The microcosms were shaken manually three times a day to promote mixing. All microcosm tests were run in triplicates. 10 mL of sample was taken at selected times for perchlorate and nitrate measurements. A perchlorate reduction rate was calculated by taking the slope of the concentration vs. time within the linear regime.

2.3. Column experiments A summary of column test conditions and dimensions is shown in Table 3. Different sizes of packed bed columns were used to quantify perchlorate reduction at various penetration depth in simulated biozones. The column test was split between a Phase 1 and Phase 2 based on the type of the amendments and column equipment. Phase 1 tests included three parallel columns (0.15 m ID  0.6 m length) which were packed with amendment mixtures. Phase 2 tests consisted of three sets of columns (5.1 cm ID), and each set included four independent columns. The four independent columns had the same amendment, but different lengths (0.15 m, 0.30 m, 0.45 m and 0.6 m). Four columns were used instead of one tall one with sampling at intermediate height for a number two reasons: (1) to provide replicates, (2) avoid disruption of conditions downstream of sampling points when sampling volumes (25 mL) equivalent to about two hours-worth of flow. Similar to the microcosm experiments, no additional bacteria were added to ensure the only source of perchlorate degraders was from the site soil.

Influent perchlorate concentration (lg/L)

Run time (days)

Hydraulic loading rate (m3/m2-d)

500 ± 50

0–127

0.15

500 ± 50

0–122

0.15

500 ± 50

0–127

0.15

500 ± 50 500 ± 50 500 ± 50 500 ± 50

0–45 46e–56 57–71 72–94

0.15 0.30 0.60 0.15

a

Phase 1 column size is 0.15 m (ID)  0.6 m (L). Sizes of each set of four parallel columns in Phase 2 were 5.1 cm (ID) and lengths of 0.15 m, 0.30 m, 0.45 m and 0.60 m. c 0.1% (w/w) EHC was mixed with soil. d 0.3% (w/w) EOS was mixed with soil. e Hydraulic loading rate in EOS-amended soil column was increased to 0.3 m3/ 2 m -d at Day 27. b

In Phase 1 column tests, three parallel columns were packed with the following materials: (1) site soil only (control); (2) EHC (0.1% w/w)-amended compost/mulch/gravel; (3) EOS (0.3% w/w)amended compost/mulch/gravel. Each column reactor consisted of a PVC pipe (0.15 m ID  0.6 m length) with sampling ports every 0.15 m on the side. Before packing the medium into the columns, compost and mulch (2:3 volume ratio) were hand-mixed with the gravel. Next, the appropriate amount of EOS or EHC was weighed based on the total mass of compost/mulch/gravel. To ensure EOS was thoroughly and evenly mixed with the compost/ mulch/gravel, the weighed EOS was first mixed with 100 mL of DI water, and then distributed as evenly as possible onto the surface of the compost/mulch/gravel mixture. Finally the entire EOSamended compost/mulch/gravel medium was hand-mixed to achieve uniformity. Since EHC is a solid compound, it was mixed with compost/mulch/gravel directly without adding DI water, and then handled in the same manner as EOS-amended compost/ mulch/gravel. Reactors were packed with 1.4 kg of gravel at the bottom, followed by the site soil only to the 0.30 m depth measured from the bottom, then the packing material to the top. This packing method was intended to mimic the manner of contaminated groundwater travelling from the aquifer soil to the amended reactive barrier. Sand (50 g) was also added every 0.15 m to create a uniform zone for sampling. The reactor was operated in an upflow mode to allow air in the pore space to vent out, and contaminated groundwater was fed into the reactor at a hydraulic loading rate of 0.15 m3/m2-d. Samples were taken from side ports and effluent periodically for perchlorate and TOC analysis. Nitrate, nitrite, arsenic, manganese and iron analyses were carried out for selected samples. Phase 2 columns were designed to investigate perchlorate reduction as a function for travel length and retention time. To save feed water volume and minimize the flow disturbances during sampling, the Phase 2 columns consisted of three sets of four

Table 2 Summary of microcosm test conditions. All conditions were tested with and without supplementation of 1 g/L of (NH4)2HPO4. Non-amendment control

EOS

Compost/mulch

EHC

50 g soil (or compost) + 200 mL of groundwater

EOS solution was mixed with 50 g soil to create 0.3% (w/w) EOS/soil mix; 200 mL groundwater was added

50 mL compost/ mulch + 200 mL of groundwater

EHC was mixed with 50 g soil to create 0.1% (w/w) EHC/soil mix; 200 mL groundwater was added

391

Y. Wang et al. / Chemical Engineering Journal 232 (2013) 388–396

700

1 g/L (NH44)2HPO4 added 600

Perchlorate, µg/L

PVC columns (5.1 cm diameter) with lengths of 0.15 m, 0.30 m, 0.45 m and 0.60 m and packed the following materials: (1) site soil only (control); (2) EOS (0.3% w/w)-amended soil; (3) EHC (0.1% w/ w)-amended soil. EOS or EHC was blended with the site soil to make up the desired concentration before packing into the columns. The inlet concentration of perchlorate was kept at 500 ± 50 lg/L, except for a spike that occurred around Day 38 due to accidental feeding with water from another site that had 70,000 lg/L perchlorate. EHC columns were replaced by fresh ones on Day 22 due to the depletion of electron donor. During the startup period, all the columns were operated at a water hydraulic loading rate of 0.15 m3/m2-d. Flow rate was increased to match a hydraulic loading rate of 0.30 m3/m2-d, and later 0.6 m3/m2-d depending on the treatment performance. Effluent samples were taken periodically for perchlorate analysis. Random effluent samples were selected for nitrate, nitrite, TOC, arsenic, manganese and iron measurements.

500 400 300 200 Control EOS, 0.003g/g soil EHC, 0.001g/g soil Compost/Mulch

100 0 0

2

4

6

8

Incubation time, d Fig. 2. Perchlorate reduction in microcosms with 1 g/L (NH4)2HPO4 added.

2.4. Analysis Perchlorate concentration was analyzed using a Dionex 1000 ion chromatograph (Dionex Corp., Sunnyvale, CA, USA) with an IonPacÒ AS 16 analytical column (4  250 mm) and AG 16 guard column (4  50 mm). Nitrate was determined by IonPacÒ AS 14 analytical column (4  250 mm) and AG 14 guard column (4  50 mm). The detection limits for perchlorate and nitrate were 4 lg/L and 100 lg/L (as N), respectively. All the other analyses for the parameters listed in Table 1 were conducted according to EPA approved methods. 3. Results 3.1. Microcosm tests The results of perchlorate reduction using different electron donors are shown in Figs. 1 and 2. As expected, there was no removal of perchlorate in the biotic controls which had no electron donor. In Fig. 1, for EHC addition, an initial apparent increase in concentration is reported which must be attributed to experimental errors, although standard deviations were small. Removal of perchlorate occurred after a lag phase of 2–3 days due the competition of nitrate as preferred electron accepter as discussed later. The shorter lag phase for the compost/mulch microcosms was attributed to the fact that nitrate which completes with perchlorate was consumed faster in those microcosms (see nitrate impact below) From all the conditions tested, with and without nutrient 700

No nutrients added

Perchlorate, µg/L

600 500 400 300 200

2

3.1.2. Impacts of nitrate presence Compared to perchlorate, nitrate is a preferred electron acceptor for chemoautotrophic bacteria found in soil and thus nitrate presence can interfere with perchlorate bioremediation [31,32]. The removal of nitrate is shown in Figs. 3 and 4. Unlike perchlorate, some nitrate removal occurred in the controls, both in absence and presence of nutrients. Possibility, the naturally existing organic matter in the soil was utilized for nitrate reduction. In all three amended treatments, 100% removal of nitrate was achieved within 4 days or less. The results were similar to the findings of other researchers [30–33], specifically that nitrate competed for the electron donor with perchlorate, and perchlorate removal was not initiated until most of nitrate was degraded [33]. The addition of 1 g/L (NH4)2HPO4 did not strongly impact nitrate reduction, except in EOS amended microcosms for which nitrate removal increased from 20% to 85% on Day 2.

Electron donor

0 0

3.1.1. Impacts of nutrient presence As mentioned earlier, (NH4)2HPO4, was added to determine whether N or P was limiting at the site conditions. As can be seen in Table 4, the addition of nutrients did not enhance the perchlorate removal rate (as determined by the slope of concentration decrease) in the presence of EHC. However, nutrients were beneficial for both EOS and compost/mulch treatment. In the case of EOS treatment, the perchlorate reduction rate was roughly doubled after adding (NH4)2HPO4 indicating some sort of nutrient limitation. An interesting behavior was observed in compost/mulch microcosms. For the first 4 days, the perchlorate reduction was very similar with and without nutrients, thereafter perchlorate reduction seemed to plateau without nutrients. Overall, the perchlorate reduction rate was also roughly doubled in the presence of nutrients.

Table 4 Perchlorate removal rate in the microcosms in presence or absence of nutrients using different electron donors.

Control EOS, 0.003g/g soil EHC, 0.001g/g soil Compost/Mulch

100

addition, the best performance for perchlorate reduction was with EHC (0.001 g/g soil) addition, which achieved 100% perchlorate removal after 5 days, followed by 7 days for EOS (0.003 g/g soil) and 64.8% removal after 8 days with compost/mulch amended soil.

4

6

8

Incubation time, d Fig. 1. Perchlorate reduction in microcosms with no nutrients added. Error bars are standard deviations.

EOS EHC Compost/Mulch

Reduction rate (lg/L/d) Without nutrients

With nutrients

142 314 40

250 263 90

392

Y. Wang et al. / Chemical Engineering Journal 232 (2013) 388–396

1000

8 Control EOS, 0.003g/g soil EHC, 0.001g/g soil Compost/Mulch

6

Perchlorate, µg/L

Nitrate, mg/L as N

No nutrients added

4

100

Influent EOS amended compost/mulch/gravel EHCamended compost/mulch/gravel

10

2

Detection Limit = 4 µg/L

0

1 0

2

4

6

8

0

20

40

Incubation time, d

100

120

140

Fig. 5. Perchlorate reduction in Phase 1 compost/mulch/gravel columns. Nondetect samples are plotted as half the ND concentration.

1000

1 g/L (NH44)2HPO4 added

Day 98 Day 105 Day 131

6

4

Perchlorate, µg/L

Nitrate, mg/L as N

80

Time, d

Fig. 3. Nitrate reduction in microcosms with no nutrients added.

8

60

Control EOS, 0.003g/g soil EHC, 0.001g/g soil Compost/Mulch

100

10 Detection Limit = 4 µg/L

2

1 0.00

0 0

2

4

6

8

.15

Incubation time, d Fig. 4. Nitrate reduction in microcosms with 1 g/L (NH4)2HPO4 added.

.30

.45

.60

Distance, m Fig. 6. Axial concentration profile of perchlorate at selected sampling times in the EOS-amended compost/mulch/gravel column. Non-detect samples are plotted as half the ND concentration.

3.2. Flowthrough column experiments 1000 Day 93 Day 100 Day 126

Perchlorate, µg/L

3.2.1. Phase 1 column experiments The performance of the EOS-amended compost/mulch/gravel and EHC-amended compost/mulch/gravel columns is shown in Fig. 5. With an inlet perchlorate concentration of 500 ± 50 lg/L and retention time of about 2 days (assuming the porosity was 50%), perchlorate concentration in the effluent in both treatments reached the detection limit of 4 lg/L within 20 days, and remained below this level for the remainder of the experiment. Unfortunately no samples were taken in the first 20 days as perchlorate reduction was not expected this rapidly, based on microcosms experiments. Thus the dynamics during the initial startup remains unknown. Liquid samples were also taken from the side sampling ports on selected days to evaluate perchlorate penetration along the flow direction. The concentration profiles (Fig. 6) showed that 67–90% of perchlorate removal was achieved in the first 15 cm of the EOS-amended column, and that removal to non-detect concentrations was achieved at the 30 cm mark. Perchlorate removal in the EHC-amended column was even faster as perchlorate concentration was close to the detection limit after 15 cm and was nondetected thereafter (Fig. 7). Perchlorate concentration profiles in both EHC and EOS amended columns were not affected by time, indicating that treatment performance was stable over the duration of the experiment.

100

10 Detection Limit = 4 µg/L

1 0.00

.15

.30

.45

.60

Distance, m Fig. 7. Axial concentration profile of perchlorate at selected sampling times in the EHC-amended compost/mulch/gravel column. Non-detect samples are plotted as half the ND concentration.

3.2.2. Phase 2 column experiments The performance of Phase 2 columns is shown in Figs. 8 and 9. Phase 2 experiment lasted 92 days during which the water flow

393

Y. Wang et al. / Chemical Engineering Journal 232 (2013) 388–396

10000

(0.15m)

0.30m/d

0.15m/d

0.60m/d

0.15m/d

Control

Perchlorate, µg/L

EHC

1000

100

10 Detection Limit = 4 µg/L

1 10000

Perchlorate, µg/L

(0.30m)

0.30m/d

0.15m/d

0.60/d

0.15m/d

Control EHC

1000

100

10 Detection Limit = 4 µg/L

1 10000

Perchlorate, µg/L

(0.45m)

0.15m/d

0.30m/d

0.60m/d

0.15m/d

Control EHC

0.30m/d

0.60m/d

0.15m/d

Control EHC

1000

100

10 Detection Limit = 4 µg/L

1 10000

Perchlorate, µg/L

(0.60m)

0.15m/d

1000

100

10 Detection Limit = 4 µg/L

1 0

20

40

60

80

100

Time, d Fig. 8. Perchlorate reduction in biotic control and EHC-amended soil columns. The arrows indicate the day columns were replaced with freshly packed ones. Non-detect samples are plotted as half the ND concentration.

rate was varied three times. Perchlorate was reduced from 500 ± 50 lg/L to levels that depended on the flow rate and the time into the experiment as discussed below. During the first 45 days of operation, the water hydraulic loading rate was maintained at 0.15 m3/m2-d in all the columns. There was some reduction of perchlorate in the control columns even though no organic electron donor was added. The hypothesis that natural organic matters in the soil served as electron donor. After the depletion of the readily available natural soil organic matter, the effluent perchlorate concentration increased and reached the same level as the inlet for the rest of the experiment. In the EHC-amended soil columns, very effective perchlorate removal was observed during the first 2 weeks for the 0.15 m, 0.30 m and 0.45 m columns. However, the effluent perchlorate concentration rapidly increased thereafter. On Day 20, less than 10% removal

was observed in these three columns. A possible reason was that the columns had been prepared (and stored) about one month before the experiment started, and perhaps, much of the EHC had already been consumed. This was not investigated further; instead all EHC columns were replaced by a set of newly prepared columns on Day 22. After several days of fluctuation, complete removal of perchlorate was achieved in all new columns, and the effluent perchlorate concentration was again below the detection limit of 4 lg/ L. Effluent perchlorate concentration remained very low (<4 lg/L), even during the high concentration feeding incident. Given the good treatment performance, the hydraulic loading rate was doubled to 0.30 m3/m2-d on Day 46. Following this, perchlorate breakthrough was observed at all EHC columns at different times in direct relationship to the length of the column. The longer the reactor, the longer the residence time, and thus the later the

394

Y. Wang et al. / Chemical Engineering Journal 232 (2013) 388–396

10000

Perchlorate, µg/L

(0.15m)

0.15m/d

0.30m/d

0.60m/d

0.30m/d

0.60m/d

0.15m/d

0.30m/d

0.60m/d

0.15m/d

0.30m/d

0.60m/d

0.15m/d

0.15m/d

1000

100

10

Detection Limit = 4 µg/L

1 10000

Perchlorate, µg/L

(0.30m)

0.15m/d

1000

100

10 Detection Limit = 4 µg/L

1 10000

Perchlorate, µg/L

(0.45m)

0.15m/d

1000

100

10 Detection Limit = 4 µg/L

1 10000

Perchlorate, µg/L

(0.60m)

0.15m/d

1000

100

10

Detection Limit = 4 µg/L

1

0

20

40

60

80

100

Time, d Fig. 9. Perchlorate reduction in EOS-amended soil columns. Inlet perchlorate concentration was 500 ± 50 lg/L. Non-detect samples are plotted as half the ND concentration.

breakthrough appeared. Different levels of nitrate were also detected in the 0.15 m, 0.30 m and 0.45 m columns (data not shown here). This result has a good agreement with the observations by Dugan et al. [34], which is the preferential reduction of nitrate left insufficient electron donor for perchlorate reduction. After increasing the hydraulic loading rate to 0.60 m3/m2-d, there was no reduction in perchlorate in any of the EHC-amended columns. Therefore, the flow rate was reduced to 0.15 m3/m2-d to determine whether the system would return to the initial performance. No removal was observed in the 0.15 m column, but partial or complete removal was observed in the 0.30 m, 0.45 m and 0.60 m columns in the first few days after the adjustment. Then perchlorate in the effluent of the 0.30 m and 0.45 m columns gradually increased to the influent level, but remained non-detectable in the 0.60 m column until the end of the test. These results are consistent with

increased removal of perchlorate with greater retention time, and depletion of EHC over time. In the EOS-amended columns, complete removal of perchlorate was achieved within 2 weeks of startup. A marked transient breakthrough was observed after the high concentration feeding incident. As expected, it was most visible for the shortest column, and decreased in intensity for the larger ones. After doubling the flow rate on Day 27, perchlorate breakthrough was noticed for the 0.15 m column first, followed by 0.30 m and 0.45 m. Measurable perchlorate was only found much later in the effluent of the 0.60 m column when it had been running at 0.30 m3/m2-d for close to 20 days. After increasing the flow rate to 0.60 m3/m2-d, the effluent perchlorate matched the feed level in all three columns. Unlike in EHC-amended soil columns, no perchlorate was detected in the columns except the shortest one (0.15 m) after returning the

Y. Wang et al. / Chemical Engineering Journal 232 (2013) 388–396

flow to 0.15 m3/m2-d, which indicated the depletion of organic substrates in the 0.15 m EOS-amended column. The significant differences in the performance between EHC and EOS can be explained by the properties of the two substrates. Compared to EHC, EOS adsorbs more strongly to the soil and leaches out at a slower rate than EHC. 3.3. Water quality evaluations Although removal of perchlorate was the primary objective, evaluation of possible water quality changes during this biotreatment is warranted. Because biodegradation of perchlorate can only happen under reducing conditions, metals such as arsenic, iron, and manganese may become more soluble and mobile in the subsurface. In addition, nitrite, which is regulated, may be formed as an intermediate in the reduction of nitrate. The results of effluent water quality analyses are in Table 5. Only the highest concentration of nitrite, arsenic, iron and manganese in the effluent samples of the Phase 1 columns and Phase 2 0.60 m columns during the entire experiment and the final effluent TOC concentration in the 0.60 m columns were reported. No nitrite or arsenic was found in any of the column experiments. However, increased concentrations of iron and manganese were noticed relative to the background levels (see Tables 1 and 5) in all the effluents except the EOS-amended soil column. The elevated iron concentration in the effluent from the EHC-amended columns is consistent with EHC’s composition, which is a mixture of nutrients and zero-valent iron. Oxidation of the zero-valent iron will produce soluble ferrous ion. Another possible source was the compost/ mulch, as seen by the higher levels of iron and manganese in the EOS-amended compost/mulch/gravel column compared to the EOS-amended soil column with the same concentration of EOS. The same trend was also found in the EHC-amended compost/ mulch/gravel column. Although these results indicated a potential for metals to leach from hypothetical biozone similar to the ones tested in the lab, metals can be immobilized by either adsorption to the aquifer matrix or by precipitation with other ions after migrating downstream where the redox potential increases [35]. It is worth noting the TOC of the effluent, which was high initially but decreased during the study. The feed water had a TOC content of 1.01 mg/L (Table 1), while the final TOC in the effluent were 8.65 mg/L and 5.37 mg/L in EOS-amended soil and EHCamended soil columns, respectively. This is an important increase with possible impacts. It should be noted here that in EOSamended compost/mulch/gravel and EHC-amended compost/ mulch/gravel columns, the effluent water had a dark brown color with a high initial TOC concentration (as high a 1 g/L initially), that was attributed to organic matter leaching from the compost and mulch. The leachate became clear over time and had a TOC of 49.3 mg/L in EOS-amended and 54.3 mg/L in EHC-amended columns after 100-day operation. Still, the release of excessive color and dissolved organics can be a concern depending on the proximity drinking water wells and the fate of those organics.

Table 5 Secondary water chemistry analyses for the effluent of amended columns.

a b

Parameter

MDLa (mg/L)

EHC EOS/compost/ EHC/compost/ EOS mulch/gravel mulch/gravel amended amended soil (mg/L) soil (mg/L) (mg/L) (mg/L)

Nitrite as N Arsenic Iron Manganese

0.090 0.070 0.15 0.070

NDb ND 2.6 0.51

MDL – Method Detection Limit. ND – Non-detectable.

ND ND 130 0.77

ND ND ND 0.14

ND ND 10 1.3

395

4. Conclusions It has been shown that complete nitrate and perchlorate reduction can be achieved in aquifer materials microcosm tests within 5–12 days of adding suitable electron donor. The benefit of adding (NH4)2HPO4 as a nutrient was minimal for EOS- and EHC-amended soil indicating that N and P were not limiting in those microcosms. This was different in the compost/mulch systems for which perchlorate reduction was two times greater after adding (NH4)2HPO4. Although EHC addition resulted in the fastest removal of perchlorate among all the substrates during the microcosm tests, the longevity of EHC was shorter than that of EOS in the column studies. Estimates of the amount of perchlorate removed per mass of  amendment during the column studies was about 3.1 mg ClO4 =g  EOS and 4.7 mg ClO4 =g EHC. Changing the flow hydraulic loading rate in the column tests affected perchlorate breakthrough. At water velocities of 0.15 m3/m2-d and 0.30 m3/m2-d, and an influent perchlorate concentration of 500 ± 50 lg/L, a 0.60 m length barrier made with the tested levels of EOS or EHC should be able to treat perchlorate to low parts per billion levels. Depending on the perchlorate influent concentration and/or the length of the barrier, adding higher dosages of substrates or making multiple injections might need to be considered. Compost/mulch is another good option which can be utilized together with EOS. Compost/mulch can serve both as an electron donor and a nutrient source. However, the amount of compost/mulch should be further investigated due to the elevated TOC content observed in the effluent. Metals leaching (mostly iron and manganese) from the soil or the substrate can be a possible concern although metal levels are expected to return to the background levels because of precipitation with other components in the groundwater and/or after migrating to higher redox conditions.

References [1] T. Giblin, W.T. Frankenberger, Perchlorate and nitrate reductase activity in the perchlorate-respiring bacterium perclace, Microbiological Research 156 (2001) 311–315. [2] B.E. Logan, D. LaPoint, Treatment of perchlorate- and nitrate-contaminated groundwater in an autotrophic, gas phase, packed-bed bioreactor, Water Research 36 (2002) 3647–3653. [3] E.T. Urbansky, M.R. Schock, Issues in managing the risks associated with perchlorate in drinking water, Journal of Environmental Management 56 (1999) 79–95. [4] M.J. Sowinski, E.A. Vavricka, R.D. Morrison, An overview of perchlorate contamination in groundwater: legal, chemical, and remedial considerations, Environmental Claims Journal 15 (2003) 359–374. [5] California Department of Water Resources, Quality of Ground Waters in California, 1955–1956, State of California, Bulletin No. 66, Department of Water Resources, Division of Resources Planning, Sacramento, CA, 1958. [6] California Department of Water Resources, Quality of Ground Waters in California, 1957, State of California, Bulletin No. 66, Department of Water Resources, Division of Resources Planning, Sacramento, CA, 1960. [7] K. Christen, EPA perchlorate decision takes many by surprise, Environmental Science & Technology 37 (2003) 347A–348A. [8] B.E. Logan, A review of chlorate- and perchlorate-respiring microorganisms, Bioremediation 2 (1998) 69–79. [9] A.B. Kirk, P.K. Martinelango, K. Tian, A. Dutta, E.E. Smith, P.K. Dasgupta, Perchlorate and iodide in dairy and breast milk, Environmental Science & Technology 39 (2005) 2011–2017. [10] C.A. Sanchez, R.I. Krieger, N. Khandaker, R.C. Moore, K.C. Holts, L.L. Neidel, Accumulation and perchlorate exposure potential of lettuce produced in the lower Colorado river region, Journal of Agricultural and Food Chemistry 53 (2005) 5479–5486. [11] USEPA, Interim Drinking Water Health Advisory for Perchlorate, EPA 822-R08-025, Office of Water, U.S. Environmental Protection Agency, Washington, DC, 2008. [12] CDPH, Perchlorate in Drinking Water, CDPH R-16-04, California Department of Public Health, Sacramento, CA, 2007. [13] MassDEP, Maximum Contaminant Level for Inorganic Chemicals, Office of Research and Standards, Code of Massachusetts Regulations 310 CMR 22.06, Massachusetts Department of Environmental Protection, Boston, MA, 2006.  [14] Y. Yoon, G. Amy, J. Cho, N. Her, J. Pellegrino, Transport of perchlorate (ClO4 ) through NF and UF membranes, Desalination 147 (2002) 11–17.

396

Y. Wang et al. / Chemical Engineering Journal 232 (2013) 388–396

[15] X. Tan, B. Gao, X. Xu, Y. Wang, J. Ling, Q. Yue, Q. Li, Perchlorate uptake by wheat straw based adsorbent from aqueous solution and its subsequent biological regeneration, Chemical Engineering Journal 211–212 (2012) 37–45. [16] B. Gu, G.M. Brown, C.-C. Chiang, Treatment of perchlorate-contaminated groundwater using highly selective, regenerable ion-exchange technologies, Environmental Science & Technology 41 (2007) 6277–6282. [17] Y. Xie, S. Li, G. Liu, J. Wang, K. Wu, Equilibrium, kinetic and thermodynamic studies on perchlorate adsorption by cross-linked quaternary chitosan, Chemical Engineering Journal 192 (2012) 269–275. [18] J. Polk, Cyril Onewokae, William J. Guarini, Cliff Murray, David E. Tolbert, A. Paul Togna, Army success story: ex situ biological treatment of perchloratecontaminated groundwater, Federal Facilities Environmental Journal 13 (2002) 85–94. [19] R. Chitrakar, Y. Makita, T. Hirotsu, A. Sonoda, Montmorillonite modified with hexadecylpyridinium chloride as highly efficient anion exchanger for perchlorate ion, Chemical Engineering Journal 191 (2012) 141–146. [20] B. Gu, G.M. Brown, L. Maya, M.J. Lance, B.A. Moyer, Regeneration of perchlorate   (ClO4 )-loaded anion exchange resins by a novel tetrachloroferrate (FeCl4 ) displacement technique, Environmental Science & Technology 35 (2001) 3363–3368. [21] J.D. Coates, U. Michaelidou, R.A. Bruce, S.M. O’connor, J.N. Crespi, L.A. Achenbach, Ubiquity and diversity of dissimilatory (per)chlorate-reducing bacteria, Applied and Environmental Microbiology 65 (1999) 5234–5241. [22] G.B. Rikken, A.G.M. Kroon, C.G. van Ginkel, Transformation of (per)chlorate into chloride by a newly isolated bacterium: reduction and dismutation, Applied Microbiology and Biotechnology 45 (1996) 420–426. [23] V.F. Medina, A. Weathersby, M. Jones, A. Morrow, Column study simulating in situ bioremediation of perchlorate using acetate as an organic substrate, Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management 10 (2006) 102–107. [24] R.C. Borden, Effective distribution of emulsified edible oil for enhanced anaerobic bioremediation, Journal of Contaminant Hydrology 94 (2007) 1–12. [25] J. Polk, C. Murray, C. Onewokae, D.E. Tolbert, A.P. Togna, W.J. Guarini, S. Frisch, M. Del Vecchio, Case study of ex situ biological treatment of perchlorate-

[26] [27]

[28]

[29] [30]

[31]

[32]

[33]

[34]

[35]

contaminated groundwater, in: 4th Tri-Services Environmental Technology Symposium, June 18–20, 2001. J.G.D. Peale, J. Mueller, J. Molin, Successful iscr-enhanced bioremediation of a TCE DNAPL source utilizing EHCÒ and KB-1Ò, Remediation (2010) 63–81. Influence of EHCÒ ISCR technology on Groundwater Perchlorate Concentrations (accessed July 2013). J. Mueller, S. MacFabe, J. Vogan, M. Duchene, A. Seech, D. Hill and K. BolanosShaw, Reductive dechlorination of solvents in groundwater using controlledrelease carbon with microscale ZVI, in: Battelle’s Fourth International Conference Remediation of Chlorinated and Recalcitrant Organics, Monterey, CA, May 24–27, 2004. C. Wang, L. Lippincott, X. Meng, Kinetics of biological perchlorate reduction and pH effect, Journal of Hazardous Materials 153 (2008) 663–669. D. Wu, P. He, X. Xu, M. Zhou, Z. Zhang, Z. Houda, The effect of various reaction parameters on bioremediation of perchlorate-contaminated water, Journal of Hazardous Materials 150 (2008) 419–423. X. Yu, C. Amrhein, M.A. Deshusses, M.R. Matsumoto, Perchlorate reduction by autotrophic bacteria attached to zerovalent iron in a flow-through reactor, Environmental Science and Technology 41 (2007) 990–997. X. Yu, C. Amrhein, M.A. Deshusses, M.R. Matsumoto, Perchlorate reduction by autotrophic bacteria in the presence of zero-valent iron, Environmental Science and Technology 40 (2006) 1328–1334. M.C. Ziv-El, B.E. Rittmann, Systematic evaluation of nitrate and perchlorate bioreduction kinetics in groundwater using a hydrogen-based membrane biofilm reactor, Water Research 43 (2009) 173–181. N.R. Dugan, Daniel J. Williams, Maria Meyer, Ross R. Schneider, Thomas F. Speth, Deborah H. Metz, The impact of temperature on the performance of anaerobic biological treatment of perchlorate in drinking water, Water Research 43 (2009) 1867–1878. C. Herb Ward, Passive Bioremediation of Perchlorate Using Emulsified Edible Oils, Springer, New York, 2009.