Batch Biodegradation Experiments Research Articles

Kinetic characterization of a new phenol degrading Acinetobacter towneri strain isolated from landfill leachate treating bioreactor

The objective of this study was to establish and to mathematically describe the phenol degrading properties of a new Acinetobacter towneri CFII-87 strain, isolated from a bioreactor treating landfill leachate. For this purpose, the biokinetic parameters of phenol biodegradation at various initial phenol concentrations of the A. towneri CFII-87 strain have been experimentally measured, and four different mathematical inhibition models (Haldane, Yano, Aiba and Edwards models) have been used to simulate the substrate-inhibited phenol degradation process. The results of the batch biodegradation experiments show that the new A. towneri CFII-87 strain grows on and metabolizes phenol up to 1000 mg/L concentration, manifests significant substrate inhibition and lag time only at concentrations above 800 mg/L phenol, and has a maximum growth rate at 300 mg/L initial phenol concentration. The comparison of the model predictions with the experimental phenol and biomass data revealed that the Haldane, Aiba and Edwards models can be used with success to describe the phenol biodegradation process by A. towneri CFII-87, while the Yano model, especially at higher initial phenol concentrations, fails to describe the process. The best performing inhibition model was the Edwards model, presenting correlation coefficients of R2 > 0.98 and modelling efficiency of ME > 0.94 for the prediction of biomass and phenol concentrations on the validation datasets. The calculated biokinetic model parameters place this new strain among the bacteria with the highest tolerance towards phenol. The results suggest that the A. towneri CFII-87 strain can potentially be used in the treatment of phenolic wastewaters.

Biotransformation study of antidepressant sertraline and its removal during biological wastewater treatment

Sertraline is one of the most commonly prescribed antidepressants in the last few years. Therefore, it is not surprising that it is regularly detected in wastewaters, surface waters, sediments, biosolids and biota. Effluents from wastewater treatment plants are the main contributors to its presence in the environment. The presented study aims to elucidate the processes involved in its removal, concentrating mainly on sorption and biodegradation during wastewater treatment.We performed our laboratory scale experiments in two sets of experiments: 1) batch biodegradation and sorption experiments and 2) flow-through laboratory scale pilot wastewater treatment bioreactors. The batch experiments revealed that sorption to activated sludge was the leading removal process, eliminating up to 90% of sertraline present in the batches. Biodegradation was however the secondary removal process, influenced by the presence of alternative easily biodegradable carbon sources. We postulated chemical structures of ten detected biotransformation products. Among these, we propose the previously recognized metabolite norsertraline, sertraline ketone and hydroxy-sertraline. All the remaining biotransformation products are herein reported for the first time.The removal efficiency of approximately 94% was determined after the treatment in the flow-through bioreactors. To support our findings, we sampled influents and effluents from two wastewater treatment plants and untreated wastewater from a psychiatric hospital. Removal efficiencies of 81% and 77% were determined, and along with the parent compound sertraline, the presence of eight transformation products was confirmed in the actual wastewaters.

Biotransformation of acyclovir by an enriched nitrifying culture

This work evaluates the biodegradation of the antiviral drug acyclovir by an enriched nitrifying culture during ammonia oxidation and without the addition of ammonium. The study on kinetics was accompanied with the structural elucidation of biotransformation products through batch biodegradation experiments at two different initial levels of acyclovir (15 mg L−1 and 15 μg L−1). The pseudo first order kinetic studies of acyclovir in the presence of ammonium indicated the higher degradation rates under higher ammonia oxidation rates than those constant degradation rates in the absence of ammonium. The positive correlation was found between acyclovir degradation rate and ammonia oxidation rate, confirming the cometabolism of acyclovir by the enriched nitrifying culture in the presence of ammonium. Formation of the product carboxy-acyclovir (P239) indicated the main biotransformation pathway was aerobic oxidation of the terminal hydroxyl group, which was independent on the metabolic type (i.e. cometabolism or metabolism). This enzyme-linked reaction might be catalyzed by monooxygenase from ammonia oxidizing bacteria or heterotrophs. The formation of carboxy-acyclovir was demonstrated to be irrelevant to the acyclovir concentrations applied, indicating the revealed biotransformation pathway might be the dominant removal pathway of acyclovir in wastewater treatment.

Biodegradation of 2,4-dinitrotoluene (DNT) by Arthrobacter sp. K1 isolated from a crude oil contaminated soil

Laboratory experiments were performed to characterize and identify 2,4-dinitrotoluene (DNT)-degrading bacterial strains isolated from crude oil contaminated soil from a landfill dump site of a petroleum refinery in Mersin, Turkey. Fluorescent in situ hybridization (FISH) with dntAa probes encoding 2,4-DNT dioxygenase was used to detect 2,4-DNT-degrading bacteria. The direct FISH analysis of soil samples collected from a petroleum refinery showed very weak signals. Therefore, a selective enrichment culture technique using 2,4-DNT as the sole carbon source was then used to isolate DNT degrading bacteria. Following the culture enrichment procedure, the hybridization signals improved significantly in the isolated bacterial strains. Based on 16S rRNA sequences, the bacteria isolated from the soil samples were identified as Arthrobacter sp. Results from the batch biodegradation experiments indicate that the biodegradation rates of 2,4-DNT with this strain were highly dependent on environmental conditions such as pH and temperature, with optimum conditions obtained at 30 °C and pH ∼7. A first-order kinetic model was able to accurately describe 2,4-DNT degradation rates under different environmental conditions (e.g., pH). The ability of Arthrobacter sp. for degrading 2,4-DNT was found to be plasmid-mediated through curing experiments. The size of the plasmid involved, referred to as pArK1, was estimated to be about 8.1 kb.

Simultaneous removal of perchlorate and energetic compounds in munitions wastewater by zero-valent iron and perchlorate-respiring bacteria

Ammonium perchlorate is one of the main constituents in Army's insensitive melt-pour explosive, PAX-21 in addition to RDX and 2,4-dinitroanisole (DNAN). The objective of this study is to develop an innovative treatment process to remove both perchlorate and energetic compounds simultaneously from PAX-21 production wastewater. It was hypothesized that the pretreatment of PAX-21 wastewater with zero-valent iron (ZVI) would convert energetic compounds to products that are more amenable for biological oxidation and that these products serve as electron donors for perchlorate-reducing bacteria. Results of batch ZVI reduction experiments showed that DNAN was completely reduced to 2,4-diaminoanisole and RDX was completely reduced to formaldehyde. Anaerobic batch biodegradation experiments showed that perchlorate (30 mg L−1) in ZVI-treated PAX-21 wastewater was decreased to an undetectable level after 5 days. Batch biodegradation experiments also confirmed that formaldehyde in ZVI-treated wastewater was the primary electron donor for perchlorate-respiring bacteria. The integrated iron-anaerobic bioreactor system was effective in completely removing energetic compounds and perchlorate from the PAX-21 wastewater without adding an exogenous electron donor. This study demonstrated that ZVI pretreatment not only removed energetic compounds, but also transformed energetic compounds to products that can serve as the source of electrons for perchlorate-respiring bacteria.

Fate and degradation of nonylphenolic compounds during wastewater treatment process

In order to explore the biodegradation behavior of nonylphenolic compounds during wastewater treatment processing, two full-scale wastewater treatment plants were investigated and batch biodegradation experiments were conducted. The biodegradation pathways under the various operational conditions were identified from batch experiments: shortening of ethoxy-chains dominated under the anaerobic condition, whereas oxidizing of the terminal alcoholic group prevailed over the other routes under the aerobic condition. Results showed that the anoxic condition could accelerate the biodegradation rates of nonylphenolic compounds, but had no influence on the biodegradation pathway. The biodegradation rates of nonylphenol (NP) and short-chain nonylphenol polyethoxylates (NPnEOs, n: number of ethoxy units) increased from the anaerobic condition, then the anoxic, finally to the aerobic condition, while those of long-chain NPnEOs and nonylphenoxy carboxylates (NPECs) seemed similar under the various conditions. Under every operational condition, long-chain NPnEOs showed the highest biodegradation activity, followed by NPECs and short-chain NPnEOs, whereas NP showed relatively recalcitrant characteristics especially under the anaerobic condition. In addition, introducing sulfate and nitrate to the anaerobic condition could enhance the biodegradation of NP and short-chain NPnEOs by supplying more positive redox potentials.

Fate and transport of atorvastatin and simvastatin drugs during conventional wastewater treatment

This research investigates the environmental behavior of two widely prescribed cholesterol-lowering statin drugs that are expected to be present at significant concentrations in wastewater influents, namely: atorvastatin and simvastatin. Batch biodegradation experiments suggest that both statins are well degraded during secondary treatment, and removal rates exhibit a substrate-enhancement model reflecting elements of both first-order behavior and cometabolism. Resulting biodegradation parameters are used in conjunction with literature sorption parameters to construct a mass-balance model of statin concentrations during conventional treatment. Model results exhibit excellent accuracy compared to measurements from a medium-sized WWTP in the Southeastern USA. Influent concentrations of 1.56μgL−1 and 1.23μgL−1 were measured for atorvastatin and simvastatin. Results also suggest that 85–90% of each drug is removed during conventional treatment, with sorption accounting for less than 10% of overall removal. Expected effluent concentrations are orders of magnitude less than previously reported ecotoxicity thresholds for both drugs. Overall, results suggest statin active ingredients do not pose a significant environmental threat. It is recommended that future work characterize the fate of statin metabolites and that the same mass-balance modeling approach be used to assess other highly-prescribed pharmaceutical drugs.

Effect of S0/X0 ratio and acclimation on respirometry of activated sludge in the cometabolic biodegradation of phenolic compounds

Aerobic batch biodegradation experiments and respirometric analysis were performed in order to investigate the effect of S0/X0 (substrate/biomass) ratio and preliminary acclimation on bi-solute biodegradation of phenolic compounds. It was shown that 2-chlorophenol (2-CP) and 2-nitrophenol (2-NP) could be cometabolically biodegraded only with acclimated biomass in the presence of phenol as growth substrate. Acclimation resulted in domination of phenol oxidizing bacteria which could induce the necessary enzymes for cometabolic transformation of 2-CP and 2-NP. Biodegradation of the cometabolic compounds occurred even after depletion of phenol at resting cell conditions. Both compounds could be successfully biodegraded by the acclimated biomass at initial substrate concentrations as high as 300mg/L. Respirometric analysis showed that the optimum S0/X0 ratio ranged between 1.5 and 5.5mg CODeq/mg MLSS for cometabolic substrates 2-CP and 2-NP, whereas it was as high as 8.5mg CODeq/mg MLSS for phenol which corresponds to a phenol concentration of about 1500mg/L.

Photolysis, Biodegradation, and Sorption Behavior of Three Selected Phenolic Compounds on the Surface and Sediment of Rivers

In this study, laboratory experiments were carried out to investigate the environmental behavior of three selected phenolic compounds [2, 4-Dichlorophenol (DCP), 2, 4-Dinitrophenol (DNP) and 2, 4-Dimethylphenol (DMP)] in the aquatic environment. The results of batch sunlight photolysis experiments showed that the three phenolic compounds were photodegraded relatively easily (i.e., half-life <151 h) in June, whereas these compounds were relatively stable against sunlight in September (i.e., half-life <330 h). The results of batch biodegradation experiments using river water suggested relatively slow biodegradation (i.e., half-life <2,310 h in June, half-life <1,155 h in September, and half-life <3,466 h in January) of three phenolic compounds, and the rate constant was dependent on sampling time. Freundlich model and the pseudo second-order model can describe the sorption behaviors of phenolic compounds on sediments very well. The intraparticle diffusion model for adsorption was also investigated and compared with the pseudomodel to identify sorption mechanism.

Investigation about the efficiency of the bioaugmentation technique when applied to diesel oil contaminated soils

This work investigated the efficiency of the bioaugmentation technique when applied to diesel oil contaminated soils collected at three service stations. Batch biodegradation experiments were carried out in Bartha biometer flasks (250 mL) used to measure the microbial CO2 production. Biodegradation efficiency was also measured by quantifying the concentration of hydrocarbons. In addition to the biodegradation experiments, the capability of the studied cultures and the native microorganisms to biodegrade the diesel oil purchased from a local service station, was verified using a technique based on the redox indicator 2,6 -dichlorophenol indophenol (DCPIP). Results obtained with this test showed that the inocula used in the biodegradation experiments were able to degrade the diesel oil and the tests carried out with the native microorganisms indicated that these soils had a microbiota adapted to degrade the hydrocarbons. In general, no gain was obtained with the addition of microorganisms or even negative effects were observed in the biodegradation experiments.

Impact of cell density on microbially induced stable isotope fractionation

Quantification of microbial contaminant biodegradation based on stable isotope fractionation analysis (SIFA) relies on known, invariable isotope fractionation factors. The microbially induced isotope fractionation is caused by the preferential cleavage of bonds containing light rather than heavy isotopes. However, a number of non-isotopically sensitive steps preceding the isotopically sensitive bond cleavage may affect the reaction kinetics of a degradation process and reduce the observed (i.e., the macroscopically detectable) isotope fractionation. This introduces uncertainty to the use of isotope fractionation for the quantification of microbial degradation processes. Here, we report on the influence of bacterial cell density on observed stable isotope fractionation. Batch biodegradation experiments were performed under non-growth conditions to quantify the toluene hydrogen isotope fractionation by exposing Pseudomonas putida mt-2(pWWO) at varying cell densities to different concentrations of toluene. Observed isotope fractionation depended significantly on the cell density. When the cell density rose from 5 x 10(5) to 5 x 10(8)cells/mL, the observed isotope fractionation declined by 70% and went along with a 55% decrease of the degradation rates of individual cells. Theoretical estimates showed that uptake-driven diffusion to individual cells depended on cell density via the overlap of the cells' diffusion-controlled boundary layers. Our data suggest that biomass effects on SIFA have to be considered even in well-mixed systems such as the cell suspensions used in this study.

Characteristics of benzene, toluene and xylene gas removal by a biofilter using scoria

The biodegradation experiments of Benzene, Toluene and Xylene (BTX) by bacillus culture were carried out. In batch biodegradation experiments of binary mixtures, benzene degradation was inhibited by the presence of either toluene or xylene and toluene degradation was inhibited by the presence of either benzene or xylene. However, xylene degradation was stimulated when xylene was present in a mixture with either benzene or toluene to some extent. In biofilter experiments packed with scoria, benzene and toluene were removed over 90% and xylene was removed over 80% with EBCT between 10 s and 60 s when each concentration was kept constantly at 600 ppmv.

Persistence and partitioning of eight selected pharmaceuticals in the aquatic environment: Laboratory photolysis, biodegradation, and sorption experiments

We selected eight pharmaceuticals with relatively high potential ecological risk and high consumption—namely, acetaminophen, atenolol, carbamazepine, ibuprofen, ifenprodil, indomethacin, mefenamic acid, and propranolol—and conducted laboratory experiments to examine the persistence and partitioning of these compounds in the aquatic environment. In the results of batch sunlight photolysis experiments, three out of eight pharmaceuticals—propranolol, indomethacin, and ifenprodil—were relatively easily photodegraded (i.e., half-life < 24 h), whereas the other five pharmaceuticals were relatively stable against sunlight. The results of batch biodegradation experiments using river water suggested relatively slow biodegradation (i.e., half-life > 24 h) for all eight pharmaceuticals, but the rate constant was dependent on sampling site and time. Batch sorption experiments were also conducted to determine the sorption coefficients to river sediments and a model soil sample. The determined coefficients ( K d values) were much higher for three amines (atenolol, ifenprodil, and propranolol) than for neutral compounds or carboxylic acids; the K d values of the amines were comparable to those of a four-ring polycyclic aromatic hydrocarbon (PAH) pyrene. The coefficients were also higher for sediment/soil with higher organic content, and the organic carbon-based sorption coefficient (log K oc) showed a poor linear correlation with the octanol–water distribution coefficient (log D ow) at neutral pH. These results suggest other sorption mechanisms—such as electrochemical affinity, in addition to hydrophobic interaction—play an important role in sorption to sediment/soil at neutral pH.

SYNCHRONOUS FLUORESCENCE AS A SELECTIVE METHOD FOR MONITORING PYRENE IN BIODEGRADATION STUDIES

A simple and effective method based on synchronous fluorescence spectroscopy for quantifying pyrene and its metabolites in a biodegradation study using Mycobacterium frederiksbergense is reported in this work. An optimum excitation-emission wavelength offset of 39 nm and a corresponding excitation wavelength of 335 nm was found to be suitable for the determination of pyrene. Interference due to naphthalene and anthracene in the analysis were found to be 11 and 4.7%, respectively. Batch biodegradation experiments in a 3L fermentor revealed a high pyrene degradation rate of 10.22 mg L− 1 d− 1 by the mycobacterium in presence of the surfactant tween 20. Tween 20 was, however, found preferentially utilized over pyrene, which resulted in a lag of 120 h in pyrene degradation by the culture. In the absence of the surfactant, pyrene degradation rate was found to be only 6.1 mg L− 1 d− 1, but without any lag in its degradation.

Effect of metals on biodegradation kinetics for methyl tert-butyl ether

Many ground waters are polluted with a complex mixture of organic and metal contaminants. Especially, the presence of heavy metals may be of particular concern, since they may be toxic for microorganisms and may interfere with the biodegradation process. A study of methyl tert-butyl ether (MTBE) biodegradation in the presence of heavy metals with the purpose of determining the effects of type and concentration of metals on reaction kinetics was undertaken. The experiments were performed as batch biodegradation experiments, and the kinetic parameters were determined by a nonlinear regression technique. Experimental results showed that the presence of Mn 2+ offers a slight stimulating effect on MTBE degradation; however, Cr 3+ and Zn 2+ resulted in less biodegradation at metal concentrations of 1 mg l −1. The inhibitory effect of adding metals was obvious, with constantly decreasing value of MTBE degradation rate in the following order Cu 2+ > Cr 3+ > Zn 2+ > Mn 2+ at metal concentrations 10 mg l −1 and 50 mg l −1. The kinetic parameters of μ m were found to be virtually unaffected until a threshold concentration (10 mg l −1) of metal was reached. However, a significant inhibitory effect on bacterial growth, as manifested by a decrease in both K i values for Cu 2+ (at 1 and 10 mg l −1), and both Cr 3+ and Zn 2+ (at 10 mg l −1).

Degradation of 4-chlorophenol by enriched mixed cultures utilizing phenol and glucose as added growth substrate

Two mixed cultures, phenol-oxidizing (PO) and glucose-oxidizing (GO), were cultivated in two parallel chemostat reactors. The PO culture was enriched on phenol, and the GO culture was enriched on glucose. Batch biodegradation experiments were conducted to examine the degradation of 4-chlorophenol (4-CP) under various substrate conditions. The results indicate that in the absence of added growth substrate, 4-CP transformation by PO culture was complete at S c /X o (initial 4-CP concentration/initial biomass concentration) $$ \leqq $$ 0.27 and that by GO culture was complete at S c /X o = 0.09. In the presence of 5–500 mg phenol/l, the phenol dosage required to achieve the complete transformation of 4-CP was 60 mg/l at S c /X o = 1, increasing to 120 mg/l at S c /X o = 2, and to 180 mg/l at S c /X o = 5. As glucose was added to the GO culture at a concentration of over 5–500 mg chemical oxygen demand (COD)/l, 4-CP was not completely transformed at S c /X o = 5 [S c = 50 mg/l, X o = 10 mg/l volatile suspended solids (VSS)]. These two cultures in utilizing added growth substrate were easily switched between glucose and phenol. Overall, the capacity of PO culture to degrade 4-CP, expressed as T c (4-CP mass consumed /biomass inactivated, having unit of mg 4-CP/mg VSS), was 0.15–0.80, which compares with T c values of 0.05–0.26 for GO culture. This work shows that adding phenol as a growth substrate is preferable over adding glucose, as it enhances 4-CP transformation, but a final choice should take into account both degradation efficiency and the risk of phenol toxicity.

Occurrence and biodegradability studies of selected pharmaceuticals and personal care products in sewage effluent

It is important to determine the behavior of constituents in treated sewage during soil aquifer treatment for water recycling. A collaborative project with Herman Bouwer published in 1984 documented the fate and occurrence of Priority Pollutants during groundwater recharge using wastewater with application to water reuse and agricultural systems. New compounds are continually being manufactured and released to the environment. The interest today has shifted to the behavior of emerging contaminants. One important class of emerging contaminants is pharmaceuticals and personal care products (PPCPs). The hazards to the environment and human health of trace levels of PPCPs in water supplies are poorly understood. A multi compound method using solid phase extraction and chemical derivatization with pentafluorobenzylbromide, followed by analysis via gas chromatography/mass spectrometry was used to study the occurrence and removals of 18 PPCPs in a local wastewater treatment plant (WWTP). Overall, 16 out of the 18 selected PPCPs, which span a range of therapeutic classes and some commonly used personal care products, were detected in raw sewage samples collected from the Baltimore Back River WWTP. Ten of the 18 selected PPCPs were detected in the treated sewage effluent, signifying incomplete removal for the majority of the PPCPs during the wastewater treatment processes. The majority of the target analytes were detected in both the influent and effluent WWTP samples at μg/L levels, although some PPCPs (e.g., naproxen and ibuprofen) were encountered at μg/L levels. Biodegradation is an important process for wastewater and soil aquifer treatment. Aerobic batch biodegradation (using activated sludge as microbial inocula) experiments were conducted to gain insight into the biodegradation behavior of our target PPCPs at initial concentrations of 50, 10, and 1 μg/L. Sterile control studies showed no loss of our target PPCPs during the entire incubation period, and sorption to the biomass was found to be negligible for all testing conditions. Biodegradation results were not sensitive to the initial concentration and showed that 13 of the 18 PPCPs tested exhibited biotransformations greater than 80% after 50 days of incubation. Phenytoin, 5-fluorouracil, and diclofenac were the only three compounds with removals less than 60%. The occurrence study revealed the presence of PPCPs in sewage effluents, and the biodegradation study suggests that biotransformation is a possible removal mechanism for PPCPs during groundwater recharge or soil aquifer treatment for water recycling.

活性汚泥処理における，ノニルフェノールエトキシレートからのノニルフェノールの生成

In this paper, we describe the issues regarding nonylpheol formation in the activated sludge process. In this research, a lad-scale experiment simulating a conventional activated sludge process was conducted for 160 days where hydraulic retention time was set at I day, solid retention time varied from 10 to 15 days and the dissolved oxygen (DO) level in the aeration section was controlled below 0.5mg·l-1. Nonylphenol ethoxylates (NPnEOs) (n=3 to 14) solution (200mg·l-1) were fed as a single organic substance. NPnEOs were degraded in the aeration section, but a large amount of NPnEOs (n=1-4) and NP accumulated in the activated sludge. However, nonylphenol formation was not observed in the batch biodegradation experiments under either saturated DO conditions or anaerobic conditions. It indicates that the reduction rate of short-chain NPnEOs and the formation rate of NP were strongly dependent upon the DO condition.

Competitive Substrate Biodegradation during Surfactant-Enhanced Remediation

The impact of synthetic surfactants on the aqueous phase biodegradation of benzene, toluene, and p-xylene (BTpX) was studied using two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), and two nonionic surfactants, POE(20) sorbitan monooleate (T-maz-80) and octylphenolpoly(ethyleneoxy) ethanol (CA-620). Batch biodegradation experiments were performed to evaluate surfactant biodegradability using two different microbial cultures. Of the four surfactants used in this study, SDS and T-maz-80 were readily degraded by a microbial consortium obtained from an activated sludge treatment system, whereas only SDS was degraded by a microbial culture that was acclimated to BTpX. Biodegradation kinetic parameters associated with SDS and T-maz-80 degradation by the activated sludge consortium were estimated using respirometric data in conjunction with a nonlinear parameter estimation technique as μmax = 0.93 h−1, Ks = 96.18 mg/L and μmax = 0.41 h−1, Ks = 31.92 mg/L, respectively. When both BTpX and surfactant were present in the reactor along with BTpX-acclimated microorganisms, two distinct biodegradation patterns were seen. SDS was preferentially utilized inhibiting hydrocarbon biodegradation, whereas the other three surfactants had no impact on BTpX biodegradation. None of the four surfactants were toxic to the microbial cultures used in this study. Readily biodegradable surfactants are not very effective for subsurface remediation applications as they are rapidly consumed, and also because of their potential inhibitory effects on intrinsic hydrocarbon biodegradation. This greatly increases treatment costs as surfactant recovery and reuse are adversely affected.

Laboratory Experiments Evaluating the Transport and Fate of DBCP in Hanford Sandy Loam

AbstractSoil column, batch adsorption, and batch biodegradatian experiments were conducted to determine the fate of DBCP applied in irrigation water at low concentrations (≈ 3 µg L−1) to unsaturated Hanford sandy loam soil (coarse‐loamy, mixed, nonacid, thermic Typic Xerorthents). The objective was to determine the extent that soil might treat DBCP‐contaminated groundwater proposed for irrigation of citrus in the Redlands California area. Water applications were performed cyclically to simulate citrus irrigation practices. Volatilization of DBCP to the atmosphere between irrigations was the dominant mechanism controlling its fate once applied to the soil. Soil adsorption was found to retard the transport of DBCP 3 to 5 times when compared with the wetting front movement. Batch biodegradation experiments suggested that DBCP may also be significantly metabolized by subsurface microorganisms. The half‐life was estimated to be approximately 7 d. Soil water characteristic curve hysteresis was observed with the soil column experiments and water content distributions calculated from soil water pore pressures required that scanning curves be developed to accurately simulate experimental data.