Microbial diversity and community composition in recirculating vertical flow constructed wetlands.

Microorganisms constitute a central component of constructed wetlands (CWs), playing a major role in these systems' capacity for treating wastewater. The aim of this study was to determine the diversity and composition of the microbial community found in a recirculating vertical flow CW (RVFCW) bed fed with primarily settled domestic wastewater and its response to the presence of plants, season and location in the bed. The RVFCW removed 90-95% of TSS and BOD(5) to below 10 mg L(-1). The effluent quality was not significantly affected by seasonal temperature or the existence of plants in the bed. None of these factors had discernible effects on bacterial diversity, e.g. in the planted RVFCW, the richness (S') and Shannon-Weiner diversity (H') indices were 18.3 (±3.5) and 2.49 (±0.15), respectively, which are similar to the values of 19.4 (±3.5) and 2.57 (±0.18) in the unplanted RVFCW. However, there were indications that the structure of the microbial community underwent changes that were uncorrelated with the environmental factors tested and that did not affect the overall performance. The consistency in diversity and composition/structure of the bacterial community in the face of temporal and environmental influences possibly contributes to the robustness and high treatment capacity of the RVFCW system.

Small scale recirculating vertical flow constructed wetland (RVFCW) for the treatment and reuse of wastewater.

The quantity of freshwater available worldwide is declining, revealing a pressing need for its more efficient use. Moreover, in many developing countries and lightly populated areas, raw wastewater is discarded into the environment posing serious ecological and health problems. Unfortunately, this situation will persist unless low-cost, effective and simple technologies are brought in. The aim of this study is to present such a treatment method, a novel setup which is termed recirculating vertical flow constructed wetland (RVFCW). The RVFCW is composed of two components: (i) a three-layer bed consisting of planted organic soil over an upper layer of filtering media (i.e. tuff or beads) and a lower layer of limestone pebbles, and (ii) a reservoir located beneath the bed. Wastewater flows directly into the plant root zone and trickles down through the three-layer bed into the reservoir, allowing passive aeration. From the reservoir the water is recirculated back to the bed, several times, until the desired purification is achieved. The results obtained show that the RVFCW is an effective and convenient strategy to treat (domestic, grey and agro) wastewater for re-use in irrigation. The system performance is expected to be further improved once current optimization experiments and mathematical modeling studies are concluded.

Conformational behavior of dimethyl 5-methyl-1H,3H-pyrrolo[1,2-c][1,3]thiazole-6,7-dicarboxylate 2,2-dioxide isolated in low-temperature matrixes.

The structure of dimethyl 5-methyl-1H,3H-pyrrolo[1,2-c][1,3]thiazole-6,7-dicarboxylate 2,2-dioxide (PTD) was investigated in low-temperature noble gas matrixes (Ar, Kr, Xe), amorphous solid, and the crystalline state by infrared spectroscopy and computational methods. The geometry of PTD conformers is defined by the orientation of two methyl ester groups, which may adopt pseudo-trans or pseudo-cis positions in relation to the pyrrolo-thiazole system. For both methyl ester groups, the latter arrangement was predicted by the calculations to be energetically the most favorable in the isolated molecule. The envelope form of the thiazolidine ring is present in all conformers, with the sulfur atom placed in the apex position, while the pyrrole ring is almost planar. Three types of conformers differing in the orientation of the methyl ester groups relative to the pyrrolo-thiazole system (cis/cis, trans/cis, cis/trans) were identified in the matrixes. The cis/cis forms were found to be the most stable ones in both gaseous state and argon matrixes. On the other hand, the more polar trans/cis forms were found to be stabilized in the more polarizable krypton and xenon matrixes as well as in the neat amorphous and crystalline phases. On the basis of annealing experiments, performed in argon and xenon matrixes up to 35 and 68 K, respectively, conformational changes preceding the aggregation of the compound are suggested.

Denitrification of groundwater with elemental sulfur.

Autotrophic denitrification was studied in laboratory columns packed with granular elemental sulfur only and operated in an upflow mode. Soluble inorganic carbon, sodium bicarbonate, was supplied as source of carbon for microbial growth. Denitrification rates of up to 0.20 kg N removed m(-3) d(-1) were obtained at a hydraulic retention time of I h, and a nitrate loading of 0.24 kg N m(-3) d(-1). The process is extremely simple, stable and easy to maintain.

Isolation and characterization of a novel leaf-inhabiting osmo-, salt-, and alkali-tolerant Yarrowia lipolytica yeast strain.

Salt-excreting leaves of Atriplex halimus plants harvested in the central Negev Highlands of Israel were screened for yeasts inhabiting their surfaces. Several aerobic, moderately salt- and alkali-tolerant yeasts were isolated. One of the isolates (tentatively designated S-8) was identified as Yarrowia lipolytica (Wick.) van der Walt and Arx, on the basis of its morphological, biochemical/physiological characteristics, and of quantitative chemotaxonomic and molecular marker analyses. However, the strain is distinguished from the known members of the type Y. lipolytica strain by its pronounced osmo-, salt-, and pH tolerance. Cells displayed a unique capacity to grow over a wide pH range (from 3.5 to 11.5) with a pH optimum at 4.5 to 7.5. It is proposed that the S-8 strain be assigned to a single Y. lipolytica species as its anamorpha, or as a new variety, Y. lipolytica var. alkalitolerance. The ecophysiological properties and biotechnological potentials of the new strain are discussed.

Hydrogen-dependent denitrification in a two-reactor bio-electrochemical system.

An autotrophic biological process was developed for the treatment of nitrate-contaminated drinking water. The system comprised of two steps: the water to be treated was first enriched with hydrogen (energy source) in the cathodic chamber of an electrochemical cell, and then denitrified in the bioreactor. The bioreactor was a packed bed of granulated activated carbon, and the water flow was directed in an upward continuous mode. The system was operated for one year, at various water velocities and current intensities. Denitrification rates up to 0.25 kg N m-3 d-1 were obtained at the hydraulic residence time of 1 h. The system was stable. When detected in the effluent, the concentration of nitrite was low, even under conditions that resulted in the elution of very high concentrations of nitrate.

News & notes: detection of microorganisms with overall cellulolytic activity.

A modification is described of the plate method for the detection of microorganisms with overall cellulolytic activity, including those like Cytophaga, in which the activity is cell bound. Within a few days of incubation colonies of cellulose-degrading bacteria formed holes in discs of lens paper placed on freshly inoculated agar plates.

Adaptation to salt stress in a salt-tolerant strain of the yeast Yarrowia lipolytica.

We have studied the cellular mechanisms underlying adaptation to salt stress in a newly isolated osmo- and salt-tolerant strain of the yeast Yarrowia lipolytica. When cells are incubated in the presence of 9% NaCl, a rapid change in their size and shape is observed. Salt stress is accompanied by an increase in the intracellular level of glycerol, free amino acids (notably proline and aliphatic amino acids), and Na+, as well as by changes in lipid and fatty acid composition.