Eakalak Khan

Entrapment of iron nanoparticles in calcium alginate beads for groundwater remediation applications

Zero-valent iron nanoparticles (nZVI) have been successfully entrapped in biopolymer, calcium (Ca)-alginate beads. The study has demonstrated the potential use of this technique in environmental remediation using nitrate as a model contaminant. Ca-alginate beads show promise as an entrapment medium for nZVI for possible use in groundwater remediation. Based on scanning electron microscopy images it can be inferred that the alginate gel cluster acts as a bridge that binds the nZVI particles together. Kinetic experiments with 100, 60, and 20mg NO(3)(-)-NL(-1) indicate that 50-73% nitrate-N removal was achieved with entrapped nZVI as compared to 55-73% with bare nZVI over a 2-h period. The controls ran simultaneously show little NO(3)(-)-N removal. Statistical analysis indicates that there was no significant difference between the reaction rates of bare and entrapped nZVI. The authors have shown for the first time that nZVI can be effectively entrapped in Ca-alginate beads and no significant decrease in the reactivity of nZVI toward the model contaminant (nitrate here) was observed after the entrapment.

Mineralization and biodegradability enhancement of natural organic matter by ozone–VUV in comparison with ozone, VUV, ozone–UV, and UV: Effects of pH and ozone dose

The increase in mineralization and biodegradability of natural organic matter (NOM) by ozone-vacuum ultraviolet (VUV) in comparison with ozone, VUV, ozone-ultraviolet (UV), and UV were investigated. The effects of operating parameters including pH and ozone dose were evaluated. Results showed that the mineralization rate of dissolved organic carbon (DOC) provided by the processes tested was in the following order: ozone-VUV > VUV > ozone-UV > ozone > UV. Among three pH studied (7, 9, and 11), pH 7 provided the highest DOC mineralization rate and biodegradability increase. A synergistic effect was observed when combining ozone with UV or VUV at pH 7 and 9 but not at pH 11. The oxidized NOM samples were separated into six fractions based on polarity (hydrophobic/hydrophilic) and charge (acid/neutral/base) to reveal NOM characteristic changes. Ozone-VUV was effective in mineralizing hydrophobic neutral and acid fractions. The hydrophilic neutral fraction was a major NOM fraction after oxidation (39-87%) and was contributed to by the biodegradable DOC produced during oxidation. High performance size exclusion chromatography results revealed that the combination of UV or VUV with ozone was more effective in the decomposition of high molecular weight compounds than ozone alone.

A review on risk assessment techniques for hydraulic fracturing water and produced water management implemented in onshore unconventional oil and gas production.

The objective of this paper is to review different risk assessment techniques applicable to onshore unconventional oil and gas production to determine the risks to water quantity and quality associated with hydraulic fracturing and produced water management. Water resources could be at risk without proper management of water, chemicals, and produced water. Previous risk assessments in the oil and gas industry were performed from an engineering perspective leaving aside important social factors. Different risk assessment methods and techniques are reviewed and summarized to select the most appropriate one to perform a holistic and integrated analysis of risks at every stage of the water life cycle. Constraints to performing risk assessment are identified including gaps in databases, which require more advanced techniques such as modeling. Discussions on each risk associated with water and produced water management, mitigation strategies, and future research direction are presented. Further research on risks in onshore unconventional oil and gas will benefit not only the U.S. but also other countries with shale oil and gas resources.

Atrazine degradation by stable mixed cultures enriched from agricultural soil and their characterization.

Aims:  The aim of this work was to enrich stable mixed cultures from atrazine‐contaminated soil. The cultures were examined for their atrazine biodegradation efficiencies in comparison with J14a, a known atrazine‐degrading strain of Agrobacterium radiobacter. The cultures were also characterized to identify community structure and bacterial species present.

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.

Evidence that Cryptosporidium parvum Populations Are Panmictic and Unstructured in the Upper Midwest of the United States

ABSTRACT Cryptosporidium parvum is a zoonotic protozoan parasite that causes cryptosporidiosis, an infectious diarrheal disease primarily affecting humans and neonatal ruminants. Understanding the transmission dynamics of C. parvum, particularly the specific contributions of zoonotic and anthroponotic transmission, is critical to the control of this pathogen. This study used a population genetics approach to better understand the transmission of C. parvum in the Upper Midwest United States. A total of 254 C. parvum isolates from cases of human cryptosporidiosis in Minnesota and Wisconsin and diarrheic calves in Minnesota, Wisconsin, and North Dakota were genotyped at eight polymorphic loci. Isolates with a complete profile from all eight loci (n = 212) were used to derive a multilocus genotype (MLT), which was used in population genetic analyses. Among the 94 MLTs identified, 60 were represented by a single isolate. Approximately 20% of isolates belonged to MLT 2, a group that included both human and cattle isolates. Population analyses revealed a predominantly panmictic population with no apparent geographic or host substructuring.

Effects of iron type in Fenton reaction on mineralization and biodegradability enhancement of hazardous organic compounds

The mineralization and biodegradability increase and their combination of two traditional and two relatively new organic contaminants by Fenton reagents with three different types of iron, Fe(2+), Fe(3+), and Fe(0) were investigated. The traditional contaminants examined were trichloroethene (TCE) and 2,4-dichlorophenol (2,4-DCP) while 1,4-dioxane (1,4-D) and 1,2,3-trichloropropane (TCP) were studied for the relatively new contaminants. The mineralization and biodegradability were represented by dissolved organic carbon (DOC) reduction and the ratio of biodegradable dissolved organic carbon and DOC, respectively. For all four contaminants, Fenton reagent using Fe(2+) was more effective in the DOC reduction than Fenton reagents using Fe(3+) and Fe(0) in most cases. The types of Fe that provided maximum biodegradability increase were not the same for all four compounds, Fe(3+) for TCE, Fe(0) for 2,4-DCP, Fe(2+) for 1,4-D, and Fe(3+) for TCP. When the combination of DOC elimination and biodegradability increase (least refractory fraction) was considered, Fe(2+) was the best choice except for 2,4-DCP which was susceptible to Fe(0) catalyzed Fenton reagent the most. The least refractory fractions remaining after 120 min of reaction were 20-25% for TCE, 2,4-DCP, and TCP and 30-40% for 1,4-D. The iron type in Fenton reaction also affected the type of mineralization kinetics of TCE, 2,4-DCP, and TCP as well as the types of degradation by-products of these contaminants. Some of the by-products found, such as isopropanol and propionic aldehyde, which were produced from Fe(0) catalyzed Fenton degradation of TCP, have not been previously reported.

Occurrence and pathways of manure-borne 17β-estradiol in vadose zone water

The hormone 17beta-estradiol (E2) can cause endocrine disruption in sensitive species at part per trillion concentrations. The persistence and transport pathways of manure-borne E2 in agricultural soils were determined by comparing its occurrence with the transfer of water and the transport of non-sorbing fluorobenzoic acid (FBA) tracers. This comparison was done using capillary wick lysimeters installed 0.61m beneath three corn (Zea mays L.) plots that receive swine (Sus scrofa domesticus) manure from various sources. An additional control plot was included that received no manure. Soil water transfer was modeled to compare actual versus predicted percolation. On average, lysimeters collected 61% of the expected percolation and 8% of the FBA. There were frequent E2 detections, where there were an average of 8 detections for the 11 sample events. The average detection was 21ngL(-1) and its range was 1-245ngL(-1). 17beta-Estradiol was detected before manure was applied and also in the control plot lysimeters. Furthermore, the average mass recovery of E2 in all the lysimeters was >50%, which was greater than the FBA tracer recovery. Results indicated that tracer was transported with precipitated water infiltrating into the soil surface and percolating down through the soil profile. There was substantial evidence for antecedent E2, which was persistent and mobile. The persistence and mobility of the E2 may result from its associations with colloids, such as dissolved organic matter. Furthermore, this antecedent E2 appeared to overwhelm any observable effect of manure management on E2 fate and transport.

Biodegradable dissolved organic carbon for indicating wastewater reclamation plant performance and treated wastewater quality

Various methods for measuring biodegradable dissolved organic carbon (BDOC) in water have been introduced in the last decade. Applications of the methods have been limited to drinking water. The measure of BDOC has been used mainly to indicate the quality of raw and finished waters and evaluate the performance of biological activated carbon (ozone/granular activated carbon) systems in water treatment plants. Recently, a modified BDOC protocol was developed for examining reclaimed and secondary-treated wastewaters. Use of the new BDOC method can be extended to the wastewater treatment and reclamation fields. Samples collected from a wastewater reuse pilot facility were tested for BDOC, The modified BDOC method was able to detect the increase in biodegradability of ozonated tertiary-treated wastewater. Good relationships among BDOC, dissolved organic carbon (DOC), and soluble biochemical oxygen demand were obtained. The modified protocol was later used to measure BDOC in secondary-effluent samples from 13 municipal wastewater treatment plants. The results show that BDOC can also be used as an indicator of secondary-effluent quality. Likewise, strong and significant correlations were found among BDOC, DOC, and soluble chemical oxygen demand in secondary effluents.

Impact of nanoscale zero valent iron on bacteria is growth phase dependent

The toxic effect of nanoscale zero valent iron (nZVI) particles on bacteria from different growth phases was studied. Four bacterial strains namely Escherichia coli strains JM109 and BW25113, and Pseudomonas putida strains KT2440 and F1 were experimented. The growth curves of these strains were determined. Bacterial cells were harvested based on the predetermined time points, and exposed to nZVI. Cell viability was determined by the plate count method. Bacterial cells in lag and stationary phases showed higher resistance to nZVI for all four bacterial strains, whereas cells in exponential and decline phases were less resistant to nZVI and were rapidly inactivated when exposed to nZVI. Bacterial inactivation increased with the concentration of nZVI. Furthermore, less than 14% bacterial inactivation was observed when bacterial cells were exposed to the filtrate of nZVI suspension suggesting that the physical interaction between nZVI and cell is necessary for bacterial inactivation.