Alan J. Sexstone

TREATMENT OF DOMESTIC WASTEWATER BY THREE PLANT SPECIES IN CONSTRUCTED WETLANDS

Three common Appalachian plant species (Juncus effusus L., Scirpus validus L., and Typha latifolia L.) were planted into small-scale constructed wetlands receivingprimary treated wastewater. The experimental design includedtwo wetland gravel depths (45 and 60 cm) and five plantingtreatments (each species in monoculture, an equal mixture of the three species, and controls without vegetation), with two replicates per depth × planting combination. Inflow rates (19 L day-1) and frequency (3 times day-1) were designed to simulate full-scale constructed wetlands as currently used for domestic wastewater treatmentin West Virginia. Influent wastewater and the effluent from each wetland were sampled monthly for ten physical, chemical and biological parameters, and plant demographic measurements were made. After passing through these trough wetlands, the average of all treatments showed a 70% reduction in total suspended solids (TSS) and biochemical oxygen demand (BOD), 50 to 60% reduction in nitrogen (TKN), ammonia and phosphate, anda reduction of fecal coliforms by three orders of magnitude. Depth of gravel (45 or 60 cm) had little effect on wetland treatment ability, but did influence Typha and Scirpus growth patterns. Gravel alone provided significant wastewater treatment, but vegetation further improved many treatment efficiencies. Typha significantly out-performedJuncus and Scirpus both in growth and in effluent quality improvement. There was also some evidence that the species mixture out-performed species monocultures.Typhawas the superior competitor in mixtures, but a decline in Typha growth with distance from the influent pipe suggested that nutrients became limiting or toxicities may have developed.

Fate of physical, chemical, and microbial contaminants in domestic wastewater following treatment by small constructed wetlands.

In order to evaluate the efficacy of constructed wetlands for treatment of domestic wastewater for small communities located in rural areas, small-scale wetland mesocosms (400 L each) containing two treatment designs (a mixture of Typha, Scirpus, and Juncus species; control without vegetation) were planted into two depths (45 or 60 cm) with pea gravel. Each mesocosm received 19 L/day of primary-treated domestic sewage. Mesocosms were monitored (inflow and outflow samples) on a monthly basis over a 2-year period for pH, total suspended solids (TSS), 5-day biochemical oxygen demand (BOD(5)), total Kjeldahl nitrogen (TKN), dissolved oxygen (DO), and conductivity. Microbiological analyses included enumeration of fecal coliforms, enterococci, Salmonella, Shigella, Yersinia, and coliphage. Significant differences between influent and effluent water quality for the vegetated wetlands (p<0.05) were observed in TSS, BOD(5), and TKN. Increased DO and reduction in fecal coliform, enterococcus, Salmonella, Shigella, Yersinia, and coliphage populations also were observed in vegetated wetlands. Greatest microbial reductions were observed in the planted mesocosms compared to those lacking vegetation. Despite marked reduction of several contaminants, wetland-treated effluents did not consistently meet final discharge limits for receiving bodies of water. Removal efficiencies for bacteria and several chemical parameters were more apparent during the initial year compared to the second year of operation, suggesting concern for long-term efficiency and stability of such wetlands.

Production of methane and ethylene in organic horizons of spruce forest soils

Abstract Concomitant production of CH4 and C2H4 was measured during anaerobic laboratory incubations of organic soils collected from Appalachian red spruce forests. Ethylene production generally exceeded methanogenesis, with greater production occurring in L and F compared with H and Al soil horizons. Slerilants significantly reduced production of both gases in all soils. However, treatment with 2-bromo ethane sulfonic acid (BES) or chloramphenicol decreased C2H4 but not CH4 production. Methane production was not further stimulated by the addition of non-limiting concentrations of H2. Arrhenius slopes for CH4 compared with C2H4 production at temperatures from 5 to 45 C were not significantly different among any of the soils tested. Anaerobiosis due to water saturation may produce sufficient C2H4 to adversely affect plant root growth, however, coniferous forest soils appear to be minor potential sources of atmospheric methane. The methane produced in these soils could have resulted from microorganisms other than methanogenic archaebacteria.

Freshwater mussels as monitors of bacteriological water quality

A species of commercially obtained freshwater mussel (Elliptio complanata) was shown to actively filter, concentrate, and retain fecal coliform (FC) bacteria from a variety of freshwater stream environments. Fecal coliform densities in mussel viscera were maximum within 48 hr of in situ exposure. Significant FC reproduction did not occur in mussel viscera at temperatures below 30 °C. Variation in replicate FC determinations from mussels exposed in situ for 48 hr was less than that obtained directly from water samples. Numbers of FC concentrated in mussel viscera were retained for several hours after FC densities declined in the surrounding water, suggesting the utility of mussels to record recent episodes of fecal pollution.

Differential response of size-fractionated soil bacteria in BIOLOG® microtitre plates

The majority of bacterial cells in soil observed by fluorescence microscopy are less than 0.4 μm in diameter, yet these cells rarely are recovered on nutrient agar. Metabolically active bacteria that are not culturable on solid media might respond in BIOLOG® microtitre plates, which contain 95 different carbon substrates. In the present study, BIOLOG® GN and GP microtitre plates were used to compare functional diversity of large (>0.45 μm) and small (<0.45 μm) cells within A and B horizons of cultivated and forested site situated on a single soil taxon (Guernsey silt-loam; fine, mixed mesic, Aquic Hapludalfs). Overall, the cultivated site exhibited greater substrate richness and average well color development compared to the forested site. The small cell fraction was numerically greater at both sites, yet exhibited limited substrate utilization compared with large cells. Greater substrate utilization by small cells was evident in A compared with B horizons at both sites. Principal component analysis separated the bacterial community by size and horizon at each study site. Small cells primarily utilized carbohydrates and carboxylic acids, compared to a broad range of substrate utilization by large cells. These data suggest that small cells are metabolically distinct from large cells. Small cells in the B horizon may be metabolically dormant and/or physiologically distinct from those in A horizon soils.

Mobility and enhanced biodegradation of a dilute waste oil emulsion during land treatment

SummaryThe mobility and biodegradability in soil of a dilute waste oil emulsion generated by an aluminium rolling industry was investigated. Laboratory simulations and field evaluation of waste disposal suggested that the majority of the oil emulsion was retained in surface soil following application. However, potential leaching of waste to the subsurface was demonstrated, particularly at higher loading rates in soils of sandy texture. Strategies to enhance rates of biodegradation in surface soils were investigated, including fertilization and microbial inoculation. A single strain inoculum was obtained from a group of 81 isolates selected for their ability to partially mineralize the waste oil emulsion, and was tentatively characterized as a hydrocarbonoclasticCorynebacterium sp. Inoculation did not effectively stimulate waste removal in soil compared with fertilization, which significantly increased respiration and biodegradation. The maximum loss of the applied oil emulsion from soil was 30% during a 56-day in vitro incubation. Fertilized, aerated liquid waste emulsion was more rapidly degraded, resulting in loss of 65% of the waste emulsion within 18 days.

Growth of apple trees, nitrate mobility and pest populations following a corn versus fescue crop rotation

We compared conventional and alternative systems for the establishment of apple trees on a replicated, whole-orchard scale. The alternative system consisted of a K-31 fescue sod rotation followed by planting of trees directly into sod that had been kitted with herbicide. The conventional system consisted of a standard corn rotation, accompanied by application of fertilizer and nematicide. Orchard floor management in the three years following tree planting was based on the use of both pre-and post-emergence herbicides in the conventional system and only contact herbicide in the alternative system. The study documented tree growth, pest incidence, and nitrate mobility in the two systems. The alternative system compared favorably with the conventional system for the growth and establishment of four apple cultivars. Many advantages accompanied the killed sod system, including less subsurface leaching ofnitrate-N and lower costs (largely from decreased herbicide use). The alternative system provided an economical alternative to the problem of soil organic matter depletion in conventional orchard soils without requiring increased use of commercial fertilizers. Grower concerns regarding increased potential for vole damage and poor initial tree growth were unsubstantiated.

Biodegradation of a dilute waste oil emulsion applied to soil

SummaryThe use of land treatment for disposal of a dilute waste oil emulsion generated by an aluminum rolling industry was investigated. Major components of the waste, identified by gas chromatography and mass spectrometry, were linear and branched (C12−C25) and fatty acid emulsifiers (primarily, isomers of oleic acid). Hexadecane and pristane were readily biodegraded in vitro when added to soil collected from the waste disposal site. Hydrocarbons and fatty acids extracted from the waste were similarly, biodegraded, however, the rate of decomposition may have depended on the history of waste applications to soil collected from the land treatment site. The apparent half-life of resolvable waste hydrocarbons and fatty acids was 9.5 days in soil which had received waste applications averaging 25.4l m−2 wk−1. In contrast, soil receiving either 50.8l m−2 wk−1 or no waste application during summer 1987 apparent exhibited half-lives of 28.1 and 60.3 days, respectively. Waste components were restricted to the upper 48 cm of the soil cores collected from the disposal site. Core samples also provided evidence for biodegradation of hydrocarbons and fatty acids as well as an accumulation of other compounds not readily resolvable by gas chromatography

Relationships among Contrasting Measurements of Microbial Dynamics in Pasture and Organic Farm Soils

Soil bacteria exhibit short-term variations in community structure, providing an indication of anthropogenic disturbances. In this study, microbial biomass carbon (MBC), potentially mineralizable nitrogen (PMN), community level physiological profiling (CLPP), and culture-dependent DGGE (CD DGGE) fingerprinting of the 16S rRNA gene were used to compare microbial communities in organic farm and pasture soils subjected to differing agronomic treatments. Correlation analyses revealed significant relationships between MBC, PMN, and data derived from microbial community analyses. All measures separated soil types but varied in their ability to distinguish among treatments within a soil type. Overall, MBC, PMN, and CLPP were most responsive to compost and manure amendments, while CD DGGE resolved differences in legume cropping and inorganic fertilization. The results support the hypothesis that culturable soil bacteria are a responsive fraction of the total microbial community, sensitive to agronomic perturbations and amenable to further studies aimed at linking community structure with soil functions.

Detection of a Methylcarbamate Degradation Gene in Agricultural Soils Using PCR Amplification of Bacterial Community DNA

The carbamate insecticide carbofuran (2,3-dihydro-2,2-dimethyl-7-benofurayl-N-methylcarbamate) is biodegraded by a methylcarbamate hydrolase enzyme encoded by a methylcarbamate degradation (mcd) gene cloned from Achromobacter sp. strain WM111. A 0.4-kbp BamHI-KpnI fragment of the mcd gene was used as a DNA probe to monitor soil microbial populations capable of degrading carbofuran in soils from twelve contrasting agricultural sites, representing seven soil series from five U.S. states. Each soil was amended three times with carbofuran (200 μg g−1 dry weight soil) and monitored until 90% of the carbofuran had degraded after each application. Soil bacterial community DNA was extracted and humic acid contaminants removed prior to PCR amplification of mcd. The detection limit for the probe protocol was 102 microorganisms g−1 of soil. Eight soils were mcd positive, and four were negative. Results were independently confirmed using both a Southern blot and slot blot protocol. Of the four negative soils, three exhibited accelerated rates of carbofuran degradation, suggesting that enzymes other than the hydrolase encoded by mcd were active in pesticide removal.