ABSTRACT An 8-year bioremediation field study was conducted in a trichloroethene (TCE)-contaminated, highly indurated (i.e., hard), recharge-limited (i.e., contains little water) conglomerate where common remediation strategies, such as groundwater recirculation and direct push installation of a large well network, could not be used. A tracer test using isotopically distinct water from the Hetch Hetchy Reservoir indicated that remediation fluids mainly flowed through fractures and sand lenses in the conglomerate. This was confirmed during in situ bioremediation of the site, in which Dehalococcoides (from a bioaugmentation culture) and volatile fatty acids (from injection of lactate) were the most accurate indicators of transport between wells. Some contaminants were also displaced out of the area due to injection of tracer water. Despite these difficulties, dissolved contaminant mass decreased by an estimated 80% by the end of the test, reaching the lowest values ever recorded at this site. Furthermore, the persistence of ethene 4 years after bioaugmentation suggests that the dechlorinating capacity of the remaining microbial community is comparable to the matrix diffusion of TCE into the dissolved phase.

ABSTRACTA laboratory-scale study was conducted in a 20.0-L sequencing batch reactor (SBR) to explore the feasibility of simultaneous removal of organic carbon and nitrogen from abattoir wastewater. The reactor was operated under three different combinations of aerobic-anoxic sequence, viz., (4+4), (5+3), and (5+4) h of total react period, with influent soluble chemical oxygen demand (SCOD) and ammonia nitrogen (NH4+-N) level of 2200 ± 50 and 125 ± 5 mg L−1, respectively. In (5+4) h cycle, a maximum 90.27% of ammonia reduction corresponding to initial NH4+-N value of 122.25 mg L−1 and 91.36% of organic carbon removal corresponding to initial SCOD value of 2215.25 mg L−1 have been achieved, respectively. The biokinetic parameters such as yield coefficient (Y), endogenous decay constant (kd), and half-velocity constant (Ks) were also determined to improve the design and operation of package effluent treatment plants comprising SBR units. The specific denitrification rate (qDN) during anoxic condition was estimated as 6.135 mg N/g mixed liquor volatile suspended solid (MLVSS)·h on 4-h average contact period. The value of Y, kd and Ks for carbon oxidation and nitrification were found to be in the range of 0.6225–0.6952 mg VSS/mg SCOD, 0.0481–0.0588 day−1, and 306.56–320.51 mg L−1, and 0.2461–0.2541 mg VSS/mg NH4+-N, 0.0324–0.0565 day−1, and 38.28–50.08 mg L−1, respectively, for different combinations of react periods.

ABSTRACTAn aerobic mixed culture collected in the form of activated sludge was enriched for Cr(VI) reduction. An indigenous microorganism was isolated from the enriched aerobic mixed culture and identified as Pseudomonas taiwanensis. Bioremediation studies were carried out for treating Cr(VI)-contaminated wastewater using the indigenous microorganism. The kinetic studies were carried out for initial Cr(VI) concentrations ranging from 20 to 200 mg L−1. The maximum consumption of Cr(VI) obtained was 108.3 mg L−1 for an initial Cr(VI) concentration of 150 mg L−1 at a solution pH of 7.0. The effect of nutrient dosage and pH were studied to get their optimum values. The same isolated bacterial strain was also used to treat Cr(VI)-contaminated industrial wastewater collected from a local plating industry. Various growth kinetic models, such as Monod, Powell, Haldane, Luong, and Edward models, were fitted with the obtained experimental data. The obtained results for different growth kinetic models indicate that the growth kinetics of Pseudomonas taiwanensis for bioremediation of Cr(VI) can be better understood by the Luong model (R2 = .913). The rate kinetic analysis was performed using zero-order and three-half-order kinetic models. The three-half-order kinetic model was found to be suitable for the present bioremediation study.

ABSTRACT Petroleum tar produced during the processing of crude oil is one of the earth's major pollutants. The potential of certain soil bacteria in the biodegradation of petroleum tar was assessed to develop an active indigenous bacterial consortium for bioremediation of petroleum tar–polluted sites of Assam, India. In vitro enrichment cultures of five Pseudomonas spp. were found to metabolize petroleum tar. The Fourier transform infrared (FTIR) analyses of the enrichment cultures revealed the presence of the functional groups, viz., –OH, –CHO, C˭O, and –COOH, which provided evidence for the biodegradation of petroleum tar. Further, gas chromatography–flame ionization detection (GC-FID) analyses revealed complete degradation of low-molecular-weight hydrocarbons, and the subsequent appearance of some additional peaks reflected the formation of intermediate metabolites during the degradation of petroleum tar. A mixed culture with 0.1% Tween 80 as a surfactant exhibited almost complete degradation in contrast to the degradation by the mixed culture without Tween 80. This confirmed the effect of a surfactant for acceleration of the biodegradation process of petroleum tar.

ABSTRACT A field-scale three-dimensional numerical flow and transport model was applied to simulate the fate and transport of benzene, toluene, ethylbenzene, and xylenes (BTEX) from six source zones of light non-aqueous-phase liquids (LNAPLs). A number of scenarios were defined to evaluate the effect of natural attenuation and enhanced remediation methods on the fate of BTEX. Two strategies were defined for cleaning up the site: (1) reduction of BTEX over the entire site down to the maximum concentration limit (MCL), and (2) remediation of the site to a level that reduces BTEX below MCLs only at the nearest discharge wells. The results show that under natural attenuation alone, the remediation time for benzene (time needed to decrease concentrations to a specified level) is more than 60 years, whereas that of TEX is longer, but only benzene will reach the receptors. LNAPL removal and enhanced bioremediation techniques could decrease this time to about 30 years for benzene. A cost-effective two-stage enhanced remediation operation should be applied. In the first stage, the entire dissolved BTEX plume should be treated, whereas in the second stage, after the remediation of benzene, the operation area should be limited to the remaining TEX plume areas. In the second strategy, air injection will be sufficient to prevent the BTEX plume from reaching the receptors. Addition of oxygen and hydrogen peroxide is likely too expensive.

ABSTRACT This study revealed heavy metal–induced physiological and biochemical alterations in crop seedlings by supplementing chelating agents in the nutrient solution. Hexavalent chromium (Cr+6) induces several toxic effects in hydroponically grown rice, wheat, and green gram seedlings. A noticeable decrease was observed in root length, shoot length, biomass content, and chlorophyll biosynthesis of the seedlings grown in the nutrient solutions supplemented with Cr+6 at 100 μM. The seedling growth was stimulated with supplement of chelating agents such as EDTA, DTPA, and EDDHA. An increase in proline content was noticed with the application of Cr+6 (100 μM) in nutrient solutions. Stimulated activities of antioxidant enzymes such as catalase and peroxidase were noticed with increasing concentrations of chromium. Cr bioaccumulation was significantly high in roots of seedlings treated with Cr+6 at 100 μM in nutrient solution. Shoot translocation of Cr as depicted by transportation index (Ti) values for different crops were enhanced with the application of chelating agents. The total accumulation rate (TAR) for Cr was enhanced with the supplementation of DTPA in rice and wheat, whereas the application of EDDHA was found effective for increasing the accumulation rate of Cr in green gram seedlings. This study demonstates the role of chelating agents in lessening the toxic effects of Cr+6. The chelating agents supplemented with Cr+6 in the culture medium enhanced the Cr bioavailability in plants.

ABSTRACT The efficiency of ready-to-use, source-separated, composted municipal organic wastes of Nigerian origin on degradation of soil total petroleum hydrocarbons (TPHs) in soils polluted with petroleum products (crude oil, diesel, and spent engine oil) was assessed in screen house experiments. The effect of compost:soil ratios and combined effect of compost-phytoremediation technique were also studied. TPH was determined spectrophotometrically, after extraction with 1:1 acetone-dichloromethane mixture at 425 nm. Soil pH, electrical conductivity, and phytotoxicity to seed germination and growth of maize (Zea mays L.) served as risk assessments on soil quality and evidence of recovery for the oil-impacted soil. Results showed that the treatments increased soil pH and electrical conductivity but reduced TPH. Reductions in TPH by compost technology ranged from 40% to 75.87%. Toxicity to seed germination reduced from 100% to 16.12%. Positive correlations were obtained for plant agronomical parameters and growth period, for all treatments, with coefficients in the range of .905 to .996, p < .05. This study revealed that ready-to-use composted waste has the potential for bioremediation of soils polluted with petroleum and petroleum products. This study is a contribution to the data bank of relatively simple bioremediation methods, suitable for workers in the developing countries, where there is no easy access to high-technology facilities. However, further development of this technique to achieve zero residual TPH is recommended.

ABSTRACT The influence of Aspergillus tubingensis to vegetation establishment on bauxite residue and its effects on the native arbuscular mycorrhizal fungal (AMF) colonization were studied. An alkali tolerant bermudagrass (Cynodon dactylon) adapted to local conditions was grown in bauxite residue with different amendments with and without A. tubingensis. Amendments of bauxite residue positively affected the growth of bermudagrass, especially when amended with gypsum and sludge. Gypsum- and sludge-amended treatments inoculated with A. tubingensis had maximum above-ground biomass, nutrient uptake, and reduced accumulation of metals. The native AMF colonization also increased because of A. tubingensis inoculation. The results of the present study suggest that A. tubingensis has the potential to improve the establishment of vegetation and neutralization of bauxite residue, especially when amended with gypsum and sludge.

ABSTRACT Arsenic is a toxic element and may be found in natural as well as in industrial water; therefore, before using water for drinking purpose, its proper treatment is required. Thus, the aim of this work was to evaluate the potential of chitosan nanoparticles, in a continuous-flow method, for the removal of arsenic (III) and (V) from aqueous solutions. All experiments were conducted in fixed-bed columns. Experiments were carried out as a function of varying liquid flow rate (0.3–1.0 ml/min), initial metal concentration (0.5–1.5 mg/L), and bed height (3–9 cm) of adsorbent. The total adsorbed quantity, equilibrium uptake, and total percentage removal of arsenic ions were determined by evaluating the breakthrough curves obtained at different flow rates, initial concentrations, and bed heights. The results showed that the column performed well at the lowest flow rate. Also, column bed capacity and exhaustion time were found to increase with increasing bed height. When initial metal ion concentration was increased from 0.5 to 1.5 mg/L, the corresponding adsorption bed capacity decreased from 0.076 to 0.028 mg/g. The bed depth service time model (BDST) model was used to analyze the experimental data and the model parameters were evaluated. The calculated values of N o and K a were found to be 19.28 × 10−2 mg/L and 0.662 L/mg·min, respectively. Good agreement was found between the experimental breakthrough curves and the model predictions.

ABSTRACT The present study concerns the biotreatment of oily sludge of petroleum refineries. Experiments were performed to assess the degradation potential of the microbial species present in the oily sludge through augmentation, and using the augmented microbial inoculums to treat oily sludge in a slurry form containing mineral medium and water. The optimum pH of the slurry was found to be 8 for the biodegradation of oily sludge. The effect of oily sludge concentration, stirring rate, and treatment time on degradation of total petroleum hydrocarbons (TPH) was studied. It was found that the degradation process consists of two consecutive stages and that each stage follows a first-order kinetics. The first stage lasted 4 days followed by a second stage up to 7 days. The faster first stage had a rate constant of 0.1 day−1, whereas the slower second stage had a rate constant of 0.056 day−1. The kinetics was found to be time-dependent. The study showed that the mineral medium provided essential nutrients to the microbial species and that the degradation efficiency of the whole microbial species present in the oily sludge was quite high (∼90%).