Effect of Cell-to-matrix Ratio in Polyvinyl Alcohol Immobilized Pure and Mixed Cultures on Atrazine Degradation

Atrazine biodegradation by immobilized pure and mixed cultures was examined. A pure atrazine-degrading culture, Agrobacterium radiobacter J14a (J14a), and a mixed culture (MC), isolated from an atrazine-contaminated crop field, were immobilized using phosphorylated-polyvinyl alcohol (PPVA). An existing cell immobilization procedure was modified to enhance PPVA matrix stability. The results showed that the matrices remained mechanically and chemically stable after shaking with glass beads over 15 days under various salt solutions and pH values. The immobilization process had a slight effect on cell viability. With the aid of scanning electron microscopy, a suitable microstructure of PPVA matrices for cell entrapment was observed. There were two porous layers of spherical gel matrices, the outside having an encapsulation property and the inside containing numerous pores for bacteria to occupy. J14a and MC were immobilized at three cell-to-matrix ratios of 3.5, 6.7, and 20 mg dry cells/mL matrix. The atrazine biodegradation tests were conducted in an aerobic batch system, which was inoculated with cells at 2,000 mg/L. The tests were also conducted using free (non-immobilized) J14a and MC for comparative purpose. The cell-to-matrix ratio of 3.5 mg/mL provided the highest atrazine removal efficiency of 40–50% in 120 h for both J14a and MC. The free cell systems, for both cultures, presented much lower atrazine removal efficiencies compared to the immobilized cell systems at the same level of inoculation.     

Polycyclic aromatic hydrocarbon removal from water by natural fiber sorption.

The use of two natural sorbents, kapok and cattail fibers, were investigated for polycyclic aromatic hydrocarbon (PAH) removal from water. Naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, and fluoranthene were the PAHs studied. For comparative purposes, a commercial polyester fiber sorbent was included in the investigation. The PAH sorption and retention capabilities of the three fibers were determined through batch and continuous-flow experiments under non-competitive and competitive conditions. In the batch experiments, cattail fiber was the most effective sorbent. Kapok fiber provided the lowest PAH retention, while cattail fiber had slightly less PAH retention than polyester fiber. When two PAHs were present in the same system, a competitive effect on the much less hydrophobic PAH was observed. Similar results were obtained in the column experiments, except that polyester fiber performed much poorer on naphthalene. Cattail fiber is a promising sorbent for treating PAH-contaminated water, such as urban runoff.     

Chromium Removal from Soil by Phytoremediation with Weed Plant Species in Thailand

The possibility of using phytoremediation with weed plant species in Thailand to remove chromium (Cr) from soil was investigated. Six plant species, Cynodon dactylon, Pluchea indica, Phyllanthus reticulatus, Echinochloa colonum, Vetiveria nemoralis, and Amaranthus viridis, were chosen for their abilities to accumulate total chromium (TCr) at tanning industry sites. These plant species were studied in pots at a nursery. Cynodon dactylon and Pluchea indica provided highest TCr accumulation capacities of 152.1 and 151.8 mg/kg of plant on a dry weight basis, respectively, at a pulse hexavalent Cr [Cr(VI)] input of 100 mg Cr(VI)/kg soil. Most of the Cr uptake occurred within 30 days after the input. The TCr accumulation by Pluchea indica was observed in roots, stems, and leaves at 27%, 38%, and 35% of the TCr mass uptake, respectively, whereas 51%, 49% and 0% of the TCr mass uptake accumulated in roots, stems, and leaves of Cynodon dactylon, respectively. The results on Cr accumulation and translocation in plant tissues suggest that Cr was removed mainly via phytoaccumulation and Pluchea indica is more suitable than Cynodon dactylon for the phytoremediation of Cr contaminated soil.     

An on-farm survey of spatial and temporal stratifications of 17β-estradiol concentrations

17β-estradiol (E2) is a natural estrogenic hormone found in animal manure and urine, which may cause endocrine disruption in sensitive organisms. 17β-Estradiol has been widely detected in the environment, and animal agriculture may be an important source. The objectives of this study were to investigate the potential sources and/or spatial and temporal characteristics contributing to detections of E2 at the farm-scale. Soil cores, segmented into 0.15 m increments, were taken down to the water table from four locations (three potential E2 sources and one control) at or around a swine (Sus scrofa domesticus) farm on five different dates between 2006 and 2007. Estradiol was quantified in the soil-water extracts using liquid chromatography-with tandem mass spectrometry (LC/MS/MS) analysis. Estradiol detections were widespread and found in 128 out of 345 extractions (37%). Concentrations ranged from 0 to 1910 ng L⁻¹ (porewater equivalents). A location that received field application of manure had significantly lower E2 concentrations compared to other locations. Also, the spring 2007 E2 concentrations were significantly higher than all other sample dates, perhaps related to climatic and hydrological events. Results suggested E2 was not directly related to manure sources, but was widespread in this environment. Where E2 was detected, highest concentrations favored the upper profile, while the greatest frequency of detections was in the lower profile and near the water table. Detections of E2 were associated with high organic mater contents in the upper profile and high sand contents in the lower profile. The study suggests that E2 is widespread in some soil environments, raising questions as to the source and mechanisms that facilitate its transport and mobility.     

Vinasse-based biochar magnetic composites: adsorptive removal of tetracycline in aqueous solutions

Environmental Science and Pollution Research - Highly efficient and cost-effective adsorbents for antibiotic removal are the key to mitigate pollution by industrial wastewaters. Pyrolyzing low-cost...     

Atrazine removal in agricultural infiltrate by bioaugmented polyvinyl alcohol immobilized and free Agrobacterium radiobacter J14a: a sand column study

Bench-scale sand column breakthrough experiments were conducted to examine atrazine removal in agricultural infiltrate by Agrobacterium radiobacter J14a (J14a) immobilized in phosphorylated-polyvinyl alcohol compared to free J14a cells. The effects of cell loading and infiltration rate on atrazine degradation and the loss of J14a were investigated. Four sets of experiments, (i) tracers, (ii) immobilized dead cells, (iii) immobilized cells, and (iv) free cells, were performed. The atrazine biodegradation at the cell loadings of 300, 600, and 900 mg dry cells L(-1) and the infiltration rates of 1, 3, and 6 cm d(-1) were tested for 5 column pore volumes (PV). The atrazine breakthrough results indicated that the immobilized dead cells significantly retarded atrazine transport. The atrazine removal efficiencies at the infiltration rates of 1, 3, and 6 cm d(-1) were 100%, 80-97%, and 50-70%, respectively. Atrazine degradation capacity for the immobilized cells was not significantly different from the free cells. Both infiltration rate and cell loading significantly affected atrazine removal for both cell systems. The bacterial loss from the immobilized cell system was 10-100 times less than that from the free cell system. For long-term tests at 50 PV, the immobilized cell system provided consistent atrazine removal efficiency while the atrazine removal by the free cells declined gradually because of the cell loss.     

Immobilized-cell-augmented activated sludge process for treating wastewater containing hazardous compounds.

A novel bioaugmentation scheme called immobilized-cell-augmented activated sludge (ICAAS) was developed. Offline enricher reactors were used to maintain immobilized acclimated cells applied to augment completely mixed activated sludge (CMAS) treating a pentachlorophenol (PCP) pulse loading. Cellulose triacetate (CA) and powder activated carbon (PAC) combined with CA (PAC + CA) were the two media types used for entrapping the PCP-degrading culture. With ICAAS at 5% by volume augmentation, PCP removal of 73.1 and 75.1% via biodegradation, volatilization, and adsorption onto suspended cells, entrapped cells, and media was achieved for the systems with CA and PAC + CA media, respectively, while PCP removal in a control CMAS, which had a comparable level of combined PCP adsorption onto suspended cells and volatilization as the ICAAS, was 48.7%. Results further showed that the immobilized cells retained their PCP-degrading ability when they were fed with the inducer (PCP) once every 20 days.     

Use of biomass sorbents for oil removal from gas station runoff

The use of biomass sorbents, which are less expensive and more biodegradable than synthetic sorbents, for oil removal from gas station runoff was investigated. A bench-scale flume experiment was conducted to evaluate the oil removal and retention capabilities of the biomass sorbents which included kapok fiber, cattail fiber, Salvinia sp., wood chip, rice husk, coconut husk, and bagasse. Polyester fiber, a commercial synthetic sorbent, was also experimented for comparison purpose. Oil sorption and desorption tests were performed at a water flow rate of 20 lmin-1. In the oil sorption tests, a 50 mgl(-1) of used engine oil-water mixture was synthesized to simulate the gas station runoff. The mass of oil sorbed for all sorbents, except coconut husk and bagasse, was greater than 70%. Cattail fiber and polyester fiber were the sorbents that provided the least average effluent oil concentrations. Oil selectivity (hydrophobic properties) and physical characteristics of the sorbents are the two main factors that influence the oil sorption capability. The used sorbents from the sorption tests were employed in the desorption tests. Results indicated that oil leached out of all the sorbents tested. Polyester fiber released the highest amount of oil, approximately 4% (mass basis) of the oil sorbed.     

Immobilized cell augmented activated sludge process for enhanced nitrogen removal from wastewater.

The immobilized cell augmented activated sludge (ICAAS) system combines a cell immobilization technique and an offline enricher-reactor for the bioaugmentation of the activated sludge system to improve treatment performances. In this study, enhanced nitrogen removal using ICAAS was investigated. Laboratory-scale, offline, batch enricher-reactors were used to maintain nitrification and denitrification activities of coimmobilized nitrifiers and denitrifiers used to augment a laboratory-scale completely mixed activated sludge system (CMAS) treating synthetic wastewater. Cellulose triacetate was the media used to entrap nitrifiers and denitrifiers at a 2:1 mass ratio. The ICAAS augmented with the coimmobilized cells between 5 and 20% by volume gained 24 +/- 5% higher nitrogen removal than a control CMAS, which provided nitrogen removal of 28 +/- 7%. The ICAAS scheme is a viable alternative for upgrading existing activated sludge systems to gain better nitrogen removal. .