Assessing the impact of dairy waste lagoons on groundwater quality using a spatial analysis of vadose zone and groundwater information in a coastal phreatic aquifer.

Dairy waste lagoons are considered to be point sources of groundwater contamination by chloride (Cl(-)), different nitrogen-species and pathogens/microorganisms. The objective of this work is to introduce a methodology to assess the past and future impacts of such lagoons on regional groundwater quality. The method is based on a spatial statistical analysis of Cl(-) and total nitrogen (TN) concentration distributions in the saturated and the vadose (unsaturated) zones. The method provides quantitative data on the relation between the locations of dairy lagoons and the spatial variability in Cl(-) and TN concentrations in groundwater. The method was applied to the Beer-Tuvia region, Israel, where intensive dairy farming has been practiced for over 50 years above the local phreatic aquifer. Mass balance calculations accounted for the various groundwater recharge and abstraction sources and sinks in the entire region. The mass balances showed that despite the small surface area covered by the dairy lagoons in this region (0.8%), leachates from lagoons have contributed 6.0% and 12.6% of the total mass of Cl(-) and TN (mainly as NO3(-)-N) added to the aquifer. The chemical composition of the aquifer and vadose zone water suggested that irrigated agricultural activity in the region is the main contributor of Cl(-) and TN to the groundwater. A low spatial correlation between the Cl(-) and NO3(-)-N concentrations in the groundwater and the on-land location of the dairy farms strengthened this assumption, despite the dairy waste lagoon being a point source for groundwater contamination by Cl(-) and NO3(-)-N. Mass balance calculations, for the vadose zone of the entire region, indicated that drying of the lagoons would decrease the regional groundwater salinization process (11% of the total Cl(-) load is stored under lagoons). A more considerable reduction in the groundwater contamination by NO3(-)-N is expected (25% of the NO3(-)-N load is stored under lagoons). Results demonstrate that analyzing vadose zone and groundwater data by spatial statistical analysis methods can significantly contribute to the understanding of the relations between groundwater contaminating sources, and to assessing appropriate remediation steps.

Infiltration mechanism controls nitrification and denitrification processes under dairy waste lagoon.

Earthen waste lagoons are commonly used to store liquid wastes from concentrated animal feeding operations. The fate of ammonium (NH) and nitrate (NO) was studied in the vadose zone below earthen-clay dairy farm waste lagoons using three independent vadose zone monitoring systems. The vadose zone was monitored from 0.5 to 30 m below land surface through direct sampling of the sediment porewater and continuous measurement of the sediment profile's water content variations. Four years of monitoring revealed that wastewater infiltration from the lagoon is controlled by two mechanisms: slow (mm d), constant infiltration from the lagoon bed; and rapid (m h) infiltration of wastewater and rainwater via preferential flow in desiccation cracks formed in the unsaturated clay sediment surrounding the lagoon banks. The preferential flow mechanism is active mainly during wastewater-level fluctuations and intensive rain events. The vadose zone below the waste sources remained unsaturated throughout the monitoring period, and all infiltrating NH was oxidized in the upper 0.5 m. The NH oxidation (nitrification) was coupled with NO reduction (denitrification) and depended on the sediment water content, which was controlled by the infiltration mechanism. Coupled nitrification-denitrification (CND) resulted in 90 to 100% reduction in the total nitrogen mass in the vadose zone, with higher removal under high water content (∼0.55 m m). Mass balance of nitrogen and isotopic composition of NO indicated that CND, rather than cation exchange capacity, is the key factor regulating nitrogen's fate in the vadose zone underlying earthen waste lagoons.

Characterization of an enrichment culture debrominating tetrabromobisphenol A and optimization of its activity under anaerobic conditions.

AIM: To study the effects of incubation conditions on the microbial community structure and activity of a TBBPA-debrominating enrichment culture composed of bacterial and archaeal species. METHODS AND RESULTS: The effects of the methanogen inhibitor 2-bromoethanesulfonate (BES), of the antibiotic ampicillin, of substrate (tetrabromobisphenol A, TBBPA) omission and availability of different electron donors on microbial community structure and activity were examined under anaerobic conditions. Debromination of TBBPA was blocked in the presence of ampicillin, while long-term incubation with BES resulted in delayed debromination activity. The results suggest that the bacterial species responsible for the debromination of TBBPA, while archaeal species involved in electron donor metabolism. The enrichment culture lost its debromination activity after cultivation for 9 months without TBBPA, concomitantly with the disappearance of two DNA bands in a denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments corresponding to Pelobacter carbinolicus and Sphaerochaeta sp. TQ1 that were present in the original culture. When butyrate was used as an electron donor, TBBPA debromination activity was attenuated. When acetate was used as the electron donor, no debromination was observed and in addition, there was a decrease in the abundance of the mcrA gene. CONCLUSIONS: The results indicate that to maintain a high rate of TBBPA debromination activity, it is essential to preserve the microbial community structure (bacterial and archaeal members) of this culture and supply an electron donor that produces high amounts of hydrogen when fermented. SIGNIFICANCE AND IMPACT OF THE STUDY: The study provides important information for the management of cultures to be used in bioremediation of TBBPA contaminated sites.

Terpenoid precursors of hydrocarbons from the gasoline range of petroleum.

2,6-Dimethyloctane and 2-methyl-3-ethylheptane were isolated from petroleum. These hydrocarbons which are present in relatively large amounts appear to be derived from the monoterpenoids.

Effect of flagella expression on adhesion of Achromobacter piechaudii to chalk surfaces.

AIMS: To examine flagella role and cell motility in adhesion of Achromobacter piechaudii to chalk. METHODS AND RESULTS: Transmission electron microscopy revealed that stationary cells have thicker and longer flagella than logarithmic cells. SDS-PAGE analysis showed that flagellin was more abundant in stationary cells than logarithmic ones. Sonication or inhibition of flagellin synthesis caused a 30% reduction in adhesion to chalk. Preincubation of chalk with flagella extracts reduced adhesion, by 50%. Three motility mutants were isolated. Mutants 94 and 153 were nonmotile, expressed normal levels of flagellin, have regular flagella and exhibited reduced adhesion. Mutant 208 expressed low levels of flagellin, no flagella and a spherical cell shape but with normal adhesion capacity. CONCLUSIONS: Multiple cell surface factors affect the adhesion efficiency to chalk. Flagella per se through physical interaction and through cell motility contribute to the adhesion process. The adhesion behaviour of mutant 208 suggests that cell shape can compensate for flagellar removal and motility. SIGNIFICANCE AND IMPACT OF THE STUDY: Physiological status affects bacterial cell surface properties and hence adhesion efficiency to chalk. This interaction is essential to sustain biodegradation activities and thus, remediation of contaminated chalk aquifers.

Recycled vertical flow constructed wetland (RVFCW)--a novel method of recycling greywater for irrigation in small communities and households.

The use of greywater for irrigation is becoming increasingly common. However, raw greywater is often contaminated and can cause environmental harm and pose health risks. Nevertheless, it is often used without any significant pretreatment, a practice mistakenly considered safe. The aim of this study was to develop an economically sound, low-tech and easily maintainable treatment system that would allow safe and sustainable use of greywater for landscape irrigation in small communities and households. The system is based on a combination of vertical flow constructed wetland with water recycling and trickling filter, and is termed recycled vertical flow constructed wetland (RVFCW). The RVFCW's properties, removal efficiency, hydraulic parameters and feasibility were studied, as well as the environmental effects of the treated greywater, as reflected by soil and plant parameters over time. The RVFCW was efficient at removing virtually all of the suspended solids and biological oxygen demand, and about 80% of the chemical oxygen demand after 8h. Fecal coliforms dropped by three to four orders of magnitude from their initial concentration after 8h, but this was not always enough to meet current regulations for unlimited irrigation. The treated greywater had no significant negative impact on plants or soil during the study period. The feasibility analysis indicated a return over investment after approximately three years. We concluded that the RVFCW is a sustainable and promising treatment system for greywater use that can be run and maintained by unskilled operators.

Effects of surfactants originating from reuse of greywater on capillary rise in the soil.

Greywater is all domestic wastewater excluding toilet effluents. Detergents contain surfactants, which account for the highest concentration of organic chemicals in average domestic wastewater. Accumulation of surfactants in greywater-irrigated soils was determined in three household gardens. The effect of surfactants on capillary rise in loess and sand was then tested in the range of concentrations found in the garden soils. The capillary rise of freshwater in sieved oven-dried soil mixed with different concentrations of laundry detergent solution (10% w/w moisture content) was determined. In a second setup, the soil was mixed with freshwater and the rising solution contained different concentrations of detergent solution. The introduction of laundry solution to the soils caused a significant decrease in the capillary rise over the range of concentrations that is found in greywater-irrigated soils. The effect was more noticeable in the sand than in the loess. Interestingly, in the second setup, the capillary rise of the laundry solutions in the sand was almost similar to that of freshwater, whereas in the loess the capillary rise was significantly reduced. It is suggested that accumulation of surfactants in the soil might form water repellent soils that have a significant effect on agricultural productivity and environmental sustainability.

Environmental impact and health risks associated with greywater irrigation: a case study.

There is an increasing trend to use greywater for irrigation in households. This is partly due to the notion that greywater is of better quality than wastewater and therefore does not need extensive treatment beyond addressing public health issues. The aim of the study was to evaluate the environmental impact and health risks associated with the use of greywater for irrigation on a small private farm. Over a three-year period, each of three plots on a farm was irrigated with either freshwater, fertilized water, or greywater. Irrigation water and soil from the plots were analyzed for a wide range of chemical and microbial variables. Results suggest that greywater may be of similar quality to wastewater in several parameters such as BOD and faecal coliforms. For some other variables such as boron and surfactants, greywater may even be of worse quality than wastewater. Long-term irrigation of arid loess soil with greywater may result in accumulation of salts, surfactants and boron in the soil, causing changes in soil properties and toxicity to plants. Faecal coliforms did not survive in the soil. Treating greywater before using it for irrigation is recommended, even in places where this is not a requirement.

Sorption of organic contaminants in a fractured chalk formation.

Sorption capability of bedrock components from a fractured chalk province was evaluated using ametryn, phenanthrene, m-xylene, 2,4,6-tribromophenol, and 1,2-dichloroethane. Sorption isotherms for the four aromatic compounds were nonlinear on gray (unoxidized) chalk. Over the studied solution ranges, the distribution coefficient decreased by factor of 3 for phenanthrene and m-xylene, a factor 4 for ametryn, and by an order of magnitude for 2,4,6-tribromophenol. In contrast, 1,2-dichloroethane displayed a linear isotherm. The importance of polar interactions for ametryn sorption was evaluated by normalizing sorption to an "inert" solvent, n-hexane. n-Hexane-normalized sorption of ametryn was much greater than that of phenanthrene, presumably due to ametryn participation in hydrogen bonding interactions. In sharp contrast to sorption to gray chalk, sorption to white (oxidized) chalk is 100- to 1000-fold lower at any given solution concentration. The much greater sorption on gray chalk cannot be explained by specific surface area, clay content, or organic matter content; thus, the nature of the organic matter is considered to control sorption in the chalk samples. Gray chalk sorption capacity estimates for ametryn and 2,4,6-tribromophenol are similar, which, together with evidence of competition for sorption sites, suggests that the limited capacity sorption domain for both compounds is similar.

Analytical procedure for simultaneous use of seven fluorobenzoates in multitracer tests.

An analytical procedure allowing simultaneous use of seven fluorobenzoate (FBA) isomers was developed and examined through column and field tracer experiments. The analytical method, based on high performance liquid chromatography (HPLC), included a reverse-phase separation method. This method was found to be very efficient for the FBA analysis, allowing accurate determination of seven FBAs in a single HPLC run, while avoiding analytical interference of other natural water constituents or pollutants. Consequently, this separation method allows the simultaneous use of seven isomers in multitracer tests in highly saline or contaminated environments. The mobility properties of the FBAs were examined in percolation experiments through a column filled with a mixture of crushed chalk and common fracture filling and coating material. The FBAs behaved conservatively as compared to bromid. All seven FBA isomers were successfully used in a multitracer test in a field percolation experiment designed to identify flowpath along a fracture plane.

Retardation of organic contaminants in natural fractures in chalk.

Transport of a conservative compound and two sorbing compounds through fractured chalk was studied using flow-through columns consisting of chalk cores with a single subvertical fracture. Two types of chalk matrix were compared, an oxidized white chalk with low organic carbon content (0.2%), and a gray chalk with a higher organic carbon content (1.3%). Initial rapid breakthrough followed by a delayed approach to a relative concentration of unity for the conservative compound (2,6-difluorobenzoic acid [DFBA]) was clear evidence for diffusion into the porous chalk matrix. Matrix diffusion of DFBA was apparently much greater in the gray chalk columns than in the white chalk columns. Breakthrough curves (BTCs) of the sorbing compounds (2,4,6-tribromophenol [TBP] and ametryn [AME]) were retarded in all cases as compared to the conservative compound. Sorption retardation was far greater in the gray chalk as compared with the white chalk, in good agreement with results from batch sorption experiments. BTCs for the conservative compound were relatively nonhysteretic for both white and gray chalk columns. In contrast, BTCs for the sorbing compounds were hysteretic in all cases, demonstrating that sorption was not at equilibrium before desorption began. These experiments suggest that on a field scale, transport of contaminants through fractures in chalk and other fractured porous media will be attenuated by diffusion and sorption into the matrix.

Biodegradation of explosives mixture in soil under different water-content conditions.

Soil redox potential plays a key role in the rates and pathways of explosives degradation, and is highly influenced by water content and microbial activity. Soil redox potential can vary significantly both temporally and spatially in micro-sites. In this study, when soil water content increased, the redox potential decreased, and there was significant enhancement in the biodegradation of a mixture of three explosives. Whereas TNT degradation occurred under both aerobic and anaerobic conditions, RDX and HMX degradation occurred only when water content conditions resulted in a prolonged period of negative redox potential. Moreover, under unsaturated conditions, which are more representative of real environmental conditions, the low redox potential, even when measured for temporary periods, was sufficient to facilitate anaerobic degradation. Our results clearly indicate a negative influence of TNT on the biodegradation of RDX and HMX, but this effect was less pronounced than that found in previous slurry batch experiments: this can be explained by a masking effect of the soil in the canisters. Fully or partially saturated soils can promote the existence of micro-niches that differ considerably in their explosives concentration, microbial community and redox conditions.

Sequential biodegradation of TNT, RDX and HMX in a mixture.

We describe TNT's inhibition of RDX and HMX anaerobic degradation in contaminated soil containing indigenous microbial populations. Biodegradation of RDX or HMX alone was markedly faster than their degradation in a mixture with TNT, implying biodegradation inhibition by the latter. The delay caused by the presence of TNT continued even after its disappearance and was linked to the presence of its intermediate, tetranitroazoxytoluene. PCR-DGGE analysis of cultures derived from the soil indicated a clear reduction in microbial biomass and diversity with increasing TNT concentration. At high-TNT concentrations (30 and 90 mg/L), only a single band, related to Clostridium nitrophenolicum, was observed after 3 days of incubation. We propose that the mechanism of TNT inhibition involves a cytotoxic effect on the RDX- and HMX-degrading microbial population. TNT inhibition in the top active soil can therefore initiate rapid transport of RDX and HMX to the less active subsurface and groundwater.

Anaerobic-aerobic process for microbial degradation of tetrabromobisphenol A.

Tetrabromobisphenol A (TBBPA) is a flame retardant that is used as an additive during manufacturing of plastic polymers and electronic circuit boards. Little is known about the fate of this compound in the environment. In the current study we investigated biodegradation of TBBPA, as well as 2,4,6-tribromophenol (TBP), in slurry of anaerobic sediment from a wet ephemeral desert stream bed contaminated with chemical industry waste. Anaerobic incubation of the sediment with TBBPA and peptone-tryptone-glucose-yeast extract medium resulted in a 80% decrease in the TBBPA concentration and accumulation of a single metabolite. This metabolite was identified by gas chromatography-mass spectrometry (GC-MS) as nonbrominated bisphenol A (BPA). On the other hand, TBP was reductively dehalogenated to phenol, which was further metabolized under anaerobic conditions. BPA persisted in the anaerobic slurry but was degraded aerobically. A gram-negative bacterium (strain WH1) was isolated from the contaminated soil, and under aerobic conditions this organism could use BPA as a sole carbon and energy source. During degradation of BPA two metabolites were detected in the culture medium, and these metabolites were identified by GC-MS and high-performance liquid chromatography as 4-hydroxybenzoic acid and 4-hydroxyacetophenone. Both of those compounds were utilized by WH1 as carbon and energy sources. Our findings demonstrate that it may be possible to use a sequential anaerobic-aerobic process to completely degrade TBBPA in contaminated soils.

Degradation of 2,4,6-tribromophenol by bacterial cells attached to chalk collected from a contaminated aquifer.

AIM: To investigate the factors governing the adhesion and activity of the 2,4,6-tribromophenol (TBP) degrading bacterium Achromobacter piechaudii TBPZ-N61 on chalk from a contaminated aquifer. METHODS AND RESULTS: Adhesion kinetics of TBPZ-N61 to grey and white chalk from a polluted fractured chalk aquifer was tested in a batch system. Both grey and white chalk contain ca 80% CaCO3, while grey chalk contains more organic matter (2.4%) than the white chalk (0.3%) and also contains Dolmite and Clinoptilolite. Adhesion of the bacterial cells to the chalk particles (<0.2 mm) occurred rapidly (96% of the cells within 15 min). Langmuir-fitted adhesion isotherms suggest that cells in the stationary phase, which are more hydrophobic, adhere to both grey and white chalk more efficiently than cells in the logarithmic growth phase. Increasing the pH (from 6.7 to 8.1) caused a significant reduction in cell adhesion to the chalk. Activity of attached cells was evaluated in both batch and column experiments. Logarithmic cells adhering to white and grey chalk were more active in TBP degradation than cells in suspension. In column experiments, significant TBP degradation was retained up to 30 days after a single injection of TBPZ cells. Thereafter, activity was fully recovered by amendment of yeast extract. Chalk surfaces that were incubated in situ in contaminated groundwater for 20 days still allowed the adhesion and activity of TBPZ cells. CONCLUSIONS: Taken together, our results show that bacteria adhere efficiently to specific sites on the chalk surfaces, and that sustained bacterial activity of the attached cells can be achieved by adding a carbon source such as yeast extract which also overcome toxic constituents that may occur in some chalk types. SIGNIFICANCE AND IMPACT OF THE STUDY: Bioremediation of TBP-contaminated chalk aquifers is made possible by the injection of bacterial cultures.

Biodegradation of alkylpyridines by bacteria isolated from a polluted subsurface.

Ten bacterial strains were isolated from alkylpyridine polluted sediments 7.6 m below the surface. These strains were able to degrade 11 different alkylpyridine isomers. Degradation rates depended on number and position of the alkyl group. Isomers with an alkyl group at position 3 were more resistant to microbial attack. Of the 10 strains, 6 isolates were selected for detailed study. These isolates mineralized the isomers to CO2, NH4+, and biomass. All strains were gram-negative rods with a strict aerobic metabolism. Characterization of physiological and biochemical properties revealed similarity between strains. Eeach strain however, had a limited substrate range which enabled it to degrade no more than 2 to 3 compounds of the 14 alkylpyridine isomers tested. Examination of the genetic variability among cultures with the randomly amplified polymorphic DNA technique revealed high levels of genomic DNA polymorphism. The highest similarity between 2 strains (0.653) was observed between 2-picoline and 3-picoline degrading cultures. The molecular basis of the differences in substrate specificity is under investigation.

Isolation from agricultural soil and characterization of a Sphingomonas sp. able to mineralize the phenylurea herbicide isoproturon.

A soil bacterium (designated strain SRS2) able to metabolize the phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was isolated from a previously IPU-treated agricultural soil. Based on a partial analysis of the 16S rRNA gene and the cellular fatty acids, the strain was identified as a Sphingomonas sp. within the alpha-subdivision of the proteobacteria. Strain SRS2 was able to mineralize IPU when provided as a source of carbon, nitrogen, and energy. Supplementing the medium with a mixture of amino acids considerably enhanced IPU mineralization. Mineralization of IPU was accompanied by transient accumulation of the metabolites 3-(4-isopropylphenyl)-1-methylurea, 3-(4-isopropylphenyl)-urea, and 4-isopropyl-aniline identified by high-performance liquid chromatography analysis, thus indicating a metabolic pathway initiated by two successive N-demethylations, followed by cleavage of the urea side chain and finally by mineralization of the phenyl structure. Strain SRS2 also transformed the dimethylurea-substituted herbicides diuron and chlorotoluron, giving rise to as-yet-unidentified products. In addition, no degradation of the methoxy-methylurea-substituted herbicide linuron was observed. This report is the first characterization of a pure bacterial culture able to mineralize IPU.

The effect of acarbose on insulin resistance in obese hypertensive subjects with normal glucose tolerance: a randomized controlled study.

AIM: Acarbose, a glucose oxidase inhibitor, delays the absorption of glucose thus reducing post-prandial blood glucose level, haemoglobin A1c (HbA1c) and insulin resistance in patients with diabetes mellitus and in subjects with impaired glucose tolerance. The effect of acarbose in subjects with normal glucose tolerance (NGT) has hitherto not been examined. The aim of the present study was to examine the effect of acarbose in obese hypertensive subjects with NGT. METHODS: A double-blinded, parallel group study was performed on 56 male subjects with hypertension, body mass index (BMI) 27-35 kg/m2, fasting blood glucose < or =6 mmol/l and a normal oral glucose tolerance test. Blood pressure, HbA1c, lipid profile and insulin resistance [homeostasis model assessment (HOMA) index] were determined initially and following 24 weeks of acarbose, 150 mg/day or placebo. The primary end point was the change in insulin resistance. Anti-hypertensive treatment and diet were kept constant during the study. RESULTS: Insulin resistance decreased in acarbose users but not on placebo. HOMA index declined from 5.36 +/- 1.7 to 4.10 +/- 1.6 (p=0.001) on acarbose, the corresponding values on placebo were 5.44 +/- 1.9 and 5.53 +/- 1.7. A decrease in serum triglyceride values (2.16 +/- 0.16 mmol/l to 1.76 +/- 0.15 mmol/l, p=0.02) took place on acarbose with no change on placebo. There was no change in BMI, low-density lipoprotein or high-density lipoprotein values in either group. Blood pressure declined equally in both the groups, probably due to better patient compliance. CONCLUSIONS: Acarbose may reduce insulin resistance and triglycerides also in obese hypertensive subjects with normal glucose tolerance.