Estimating Potential E. coli Sources in a Watershed Using Spatially Explicit Modeling Techniques1

Riebschleager, K.J., R. Karthikeyan, R. Srinivasan, and K. McKee, 2012. Estimating Potential E. coli Sources in a Watershed Using Spatially Explicit Modeling Techniques. Journal of the American Water Resources Association (JAWRA) 48(4): 745‐761. DOI: 10.1111/j.1752‐1688.2012.00649.x Abstract: The Spatially Explicit Load Enrichment Calculation Tool (SELECT) was automated to characterize waste and the associated pathogens from various sources within a mixed land use watershed. Potential Escherichia coli loads in Lake Granbury watershed were estimated using spatially variable governing factors, such as land use, soil condition, and distance to streams. A new approach for characterizing E. coli loads resulting from malfunctioning on‐site wastewater treatment systems (OWTSs) was incorporated into SELECT along with the Pollutant Connectivity Factor (PCF) module. The PCF component was applied to identify areas contributing E. coli loads during runoff events by incorporating the influence of potential E. coli loading, runoff potential, and travel distance to waterbodies. Simulation results indicated livestock and wildlife are potential E. coli contributing sources in the watershed. The areas in which these sources are potentially contributing are not currently monitored for E. coli. The bacterial water quality violations seen around Lake Granbury are most likely the result of malfunctioning OWTSs and pet wastes. SELECT results demonstrate the need to evaluate each contributing source separately to effectively allocate site specific best management practices (BMPs) utilizing stakeholder inputs. It also serves as a powerful screening tool for determining areas where detailed investigation is merited.     

Nanoporous activated carbon fluidized bed catalytic oxidations of aqueous o, p and m-cresols: kinetic and thermodynamic studies

Nanoporous activated carbon prepared from rice husk through precarbonisation at 400 °C and phosphoric acid activation at 800 °C was used as fluidized bed in Fenton oxidation of the o, p and m-cresols in aqueous solution. The efficiencies of homogeneous Fenton oxidation, fluidized Fenton oxidation and aerobic biological oxidation systems for the removal of o, p and m-cresols in aqueous solution have been compared. The kinetic constants and the thermodynamic parameters for the homogeneous Fenton, heterogeneous Fenton and aerobic biological oxidations of o, p and m-cresols in synthetic wastewater were determined. The degradation of cresols in synthetic wastewater was confirmed using FT-IR, ¹H-NMR and UV–visible spectroscopy.     

Heterocatalytic Fenton oxidation process for the treatment of tannery effluent: kinetic and thermodynamic studies

Background, aim, scope

Treatment of wastewater has become significant with the declining water resources. The presence of recalcitrant organics is the major issue in meeting the pollution control board norms in India. The theme of the present investigation was on partial or complete removal of pollutants or their transformation into less toxic and more biodegradable products by heterogeneous Fenton oxidation process using mesoporous activated carbon (MAC) as the catalyst.

Materials and methods

Ferrous sulfate (FeSO₄·7H₂O), sulfuric acid (36?N, specific gravity 1.81, 98% purity), hydrogen peroxide (50% v/v) and all other chemicals used in this study were of analytical grade (Merck). Two reactors, each of height 50?cm and diameter 6?cm, were fabricated with PVC while one reactor was packed with MAC of mass 150?g and other without MAC served as control.

Results and discussion

The oxidation process was presented with kinetic and thermodynamic constants for the removal of COD, BOD, and TOC from the wastewater. The activation energy (Ea) for homogeneous and heterogeneous Fenton oxidation processes were 44.79 and 25.89?kJ/mol, respectively. The thermodynamic parameters ??G, ??H, and ??S were calculated for the oxidation processes using Van??t Hoff equation. Furthermore, the degradation of organics was confirmed through FTIR and UV?Cvisible spectroscopy, and cyclic voltammetry.

Conclusions

The heterocatalytic Fenton oxidation process efficiently increased the biodegradability index (BOD/COD) of the tannery effluent. The optimized conditions for the heterocatalytic Fenton oxidation of organics in tannery effluent were pH 3.5, reaction time?C4?h, and H₂O₂/FeSO₄·7H₂O in the molar ratio of 2:1.     

Performance of bioreactor landfill with waste mined from a dumpsite

Emissions from landfills via leachate and gas are influenced by state and stability of the organic matter in the solid waste and the environmental conditions within the landfill. This paper describes a modified, ecologically sound waste treatment technique, where municipal solid waste is anaerobically treated in a lysimeter-scale landfill bioreactor with leachate recirculation to enhance organic degradation. The results demonstrate a substantial decrease in organic matter (BOD 99%, COD 88% and TOC 81%) and a clear decrease in nutrient concentrations especially ammonia (85%) over a period of 1 year with leachate recirculation.     

Effect of pH on Anti-Rotavirus Activity by Comestible Juices and Proanthocyanidins in a Cell-Free Assay System

Cranberry (Vaccinium macrocarpon) and grape (Vitis labrusca) juices, and these species?? secondary plant metabolites [i.e., proanthocyanidins (PACs)] possess antiviral activity. An understanding of the mechanism(s) responsible for these juices and their polyphenolic constituents?? direct effect on enteric virus integrity, however, remains poorly defined. Using the rotavirus (RTV) as a model enteric virus system, the direct effect of manufacturer-supplied and commercially purchased juices [Ocean Spray Pure Cranberry 100?% Unsweetened Juice (CJ), Welch??s 100?% Grape Juice (GJ), 100?% Concord (PG) and 100?% Niagara juices (NG)] and these species?? cranberry (C-PACs) and grape PACs (G-PACs) was investigated. Loss of viral capsid integrity in cell-free suspension by juices and their PACs, and as a factor of pH, was identified by an antigen (RTV) capture enzyme-linked immunosorbent assay. At native and an artificially increased suspension at or near pH 7, loss of viral infectivity occurred after 5?min, in the order CJ?>?NG?=?GJ?>?PG, and PG?>?GJ?=?NG?=?CJ, respectively. Antiviral activity of CJ was inversely related to pH. Grape, but not cranberry PACs, displayed a comparatively greater anti-RTV activity at a suspension pH of 6.7. Anti-RTV activity of C-PACs was regained upon reduction of RTV-cranberry PAC suspensions to pH 4. An alteration or modification of Type A PAC (of V. macrocarpon) structural integrity at or near physiologic pH is suggested to have impacted on this molecule??s antivirus activity. Type B PACs (of V. labrusca) were refractive to alternations of pH. Significantly, findings from pure system RTV?CPAC testing paralleled and in turn, supported those RTV-juice antiviral studies. Electron microscopy showed an enshroudment by PACs of RTV particles, suggesting a blockage of viral antigenic binding determinants. The implications of our work are significant, especially in the interpretation of PAC (and PAC-containing food)?CRTV interactions in the differing [pH] conditions of the gastrointestinal tract.     

Polymeric Substitution of Triazole Moieties in Cellulosic Schiff Base for Heavy Metal Complexation Studies

Journal of Polymers and the Environment - The adsorption of metal ions from wastewater using Schiff base cellulose bearing pendulant heterocyclic chelating groups (MC-Tz) as a sorbent is the...     

Complexation of the antibiotic tetracycline with humic acid

The effect of solution chemistry and sorbate-to-sorbent ratio on the interaction of the antibiotic tetracycline with Elliott soil humic acid (ESHA) was investigated using equilibrium dialysis and FITEQL modeling. Tetracycline speciation strongly influenced its sorption to ESHA. Sorption was strongly pH-dependent with a maximum around pH 4.3, and competition with H+ and electrolyte cation (Na+) was evident. The pH-dependent trend was consistent with complexation between the cationic/zwitterionic tetracycline species and deprotonated sites in ESHA (mainly carboxylic functional groups). Modification of ESHA by Ca2+ addition increased tetracycline sorption suggesting that ternary complex formation (ESHA-metal-tetracycline) may be important at higher concentrations of multivalent metal cations. The macroscopic data (pH-envelope and sorption isotherms) were successfully modeled using a discrete logK function with the FITEQL 4.0 chemical equilibrium program indicating that ESHA-tetracycline interaction could be reasonably represented as complex formation of a monoacid with discrete sites in humic acid. Sorption-desorption hysteresis was observed; both sorption and desorption isotherms were well described by the Freundlich equation.     

Prevalence of certain inorganic constituents in groundwater samples of Erode district, Tamilnadu, India, with special emphasis on fluoride, fluorosis and its remedial measures

A total of 60 drinking water samples collected from Erode district, Tamilnadu, India were analysed for fluoride contamination, besides water quality parameters such as pH, electrical conductivity, total dissolved solids, total alkalinity, total hardness, fluoride, bicarbonates, calcium, magnesium, nitrate, sulphate, phosphate, sodium and potassium. The results obtained were found to exceed the permissible limits. The concentration of fluoride in the water samples ranged between 0.5 and 8.2 mg/l and revealed that 80% of the water samples contain fluoride above the maximum permissible limit. Similarly, the concentrations of nitrate, hardness, calcium and magnesium in some samples were also more than the permissible level. Pearson’s correlation coefficient among the parameters showed a positive correlation of fluoride with total hardness and calcium. It is inferred from the study that these water sources can be used for potable purpose only after prior treatment.     

Sorption of the antibiotic tetracycline to humic-mineral complexes

Humic substances, by altering the surface properties and/or competing for available reaction sites, can either suppress or promote sorption of organic compounds to mineral surfaces. Limited literature evidence points to the reduction in sorption of the antibiotic tetracycline to clay minerals in the presence of humic substances. We investigated the surface interaction of Elliott soil humic acid (ESHA) with hydrous Al oxide (HAO) and the effect of this association on tetracycline sorption. Strong interaction between ESHA and HAO led to ESHA-promoted dissolution of HAO and surface charge reversal. The ESHA-HAO sorption-desorption isotherms were successfully described using a modified Langmuir model that accounted for the heterogeneity of HAO surface and ESHA. Ligand exchange was proposed as the major interaction mechanism, and the edge Al atoms on HAO surface were considered as the sorption sites for ESHA macromolecules. ESHA was coated onto HAO to achieve two different organic content (foc) levels of 0.81 and 1.52%. Sorption results were compared for the binary ESHA-tetracycline and HAO-tetracycline systems, and the ternary ESHA-HAO-tetracycline system. The coating of ESHA on HAO significantly suppressed tetracycline sorption levels, attributable to altered HAO surface charge characteristics and/or direct competition between ESHA and tetracycline for potential sorption sites. Higher foc level, besides increasing the extent of sorption suppression, also resulted in greater ionic strength dependence and increased nonlinearity of sorption behavior. It, therefore, appears that the presence of humic substances, in both dissolved and mineral-bound forms, is likely to increase the environmental mobility of tetracycline compounds.