Geology topics

J.S. Thullen

Publications and source records attributed to J.S. Thullen.

6 recordsLinked to original sources

USGS2008

Aquatic macroinvertebrates associated with Schoenoplectus litter in a constructed wetland in California (USA)

Culm processing characteristics were associated with differences in invertebrate density in a study of invertebrates and senesced culm packs in a constructed treatment wetland. Invertebrate abundance differed by location within the wetland and there were differences between the two study years that appeared to be related to water quality and condition of culm material. Open areas in the wetland appeared to be critical in providing dissolved oxygen (DO) and food (plankton) to the important invertebrate culm processor, Glyptotendipes. As culm packs aged, invertebrate assemblages became less diverse and eventually supported mostly tubificid worms and leeches. It appears from this study that wetland design is vital to processing of plant material and that designs that encourage production and maintenance of high DO's will encourage microbial and invertebrate processing of material.

Ecological Engineering↗

USGS2005

Managing vegetation in surface-flow wastewater-treatment wetlands for optimal treatment performance

Constructed wetlands that mimic natural marshes have been used as low-cost alternatives to conventional secondary or tertiary wastewater treatment in the U.S. for at least 30 years. However, the general level of understanding of internal treatment processes and their relation to vegetation and habitat quality has not grown in proportion to the popularity of these systems. We have studied internal processes in surface-flow constructed wastewater-treatment wetlands throughout the southwestern U.S. since 1990. At any given time, the water quality, hydraulics, water temperature, soil chemistry, available oxygen, microbial communities, macroinvertebrates, and vegetation each greatly affect the treatment capabilities of the wetland. Inside the wetland, each of these components plays a functional role and the treatment outcome depends upon how the various components interact. Vegetation plays a uniquely important role in water treatment due to the large number of functions it supports, particularly with regard to nitrogen transformations. However, it has been our experience that vegetation management is critical for achieving and sustaining optimal treatment function. Effective water treatment function and good wildlife quality within a surface-flow constructed wetland depend upon the health and sustainability of the vegetation. We suggest that an effective tool to manage and sustain healthy vegetation is the use of hummocks, which are shallow emergent plant beds within the wetland, positioned perpendicular to the water flow path and surrounded by water sufficiently deep to limit further emergent vegetation expansion. In this paper, we describe the use of a hummock configuration, in conjunction with seasonal water level fluctuations, to manage the vegetation and maintain the treatment function of wastewater-treatment wetlands on a sustainable basis.

Ecological Engineering↗

USGS2003

The effects of bird use on nutrient removal in a constructed wastewater-treatment wetland

A 9.9-ha constructed wetland designed to reduce nitrogen in municipal wastewater following conventional secondary treatment began operating in southern California's San Jacinto Valley in September 1994. The wetland incorporated zones of bulrush ( Schoenoplectus acutus and S. californicus ) for effluent treatment, plus areas of 1.8-m deep open water and other features to benefit wintering waterfowl. A one-year long program to monitor bird use and evaluate their contribution to loadings of nitrogen and phosphorus was initiated seven months later and a second, four-month long period of monitoring was initiated after a 20-month hiatus. Daily bird use peaked at nearly 12,000 individuals during the second period. Estimates of maximum daily nitrogen and phosphorus input by birds were 139 g N ha −1 day −1 and 56 g P ha −1 day −1 . Following a reconfiguration of the wetland that increased the area of open water, a third year-long period of monitoring was initiated in September 2000. Estimated maximum daily loading attributable to birds during this period reached 312 g N ha −1 day −1 and 124 g P ha −1 day −1 . These levels represent only 2.6% and 7.0%, respectively, of the mean daily loads of N and P in inflow water from the wastewater-treatment plant. Wintering waterfowl contributed the most to nutrient loading, but the numerically dominant species was the colonial Red-winged Blackbird ( Agelaius phoeniceus ). The wetland's nutrient-removal efficiency was negatively correlated to bird loading. However, the greatest bird loading occurred during November to March, when winter conditions would reduce microbial nutrient-removal processes and plant uptake in the wetland. Multiple regression analysis indicated that variation in nutrient removal efficiency over a one-year period was best explained by wetland water temperature (R 2 = 0.21) and that little additional insight was gained by adding bird loading and inflow nutrient load data (R 2 = 0.22). This case study supports the concept that a constructed wetland can be designed both to reduce nutrients in municipal wastewater and to provide habitat for wetland birds.

Wetlands↗

USGS2000

Investigation of nitrogen transformations in a southern California constructed wastewater treatment wetland

A 9.9-ha combined habitat and wastewater treatment demonstration wetland was constructed and planted in the summer of 1994, at Eastern Municipal Water District’s (EMWD) Hemet/San Jacinto Regional Water Reclamation Facility (RWRF) in southern California. From January 1996 through September 1997, the marsh–pond–marsh wetland system was operated to polish an average of 3785 m 3 d −1 (1×10 6 gal day −1 ) of secondary-treated effluent from the RWRF. Nitrogen removal was a major objective of this wetland treatment. Weekly inflow/outflow water quality monitoring of the wetland was supplemented with biannual, 45-station synoptic surveys within the system to determine internal distribution patterns of the nitrogen species (total ammonia, nitrite, nitrate, and organic nitrogen), total organic carbon (TOC), and ultraviolet absorbance at 254 nm (UV 254 ). Synoptic surveys were carried out during May 22 and September 17, 1996, and May 6 and September 25, 1997 and the results were mapped using the ARC/INFO processing package and inverse distance weighted mathematical techniques. Distribution patterns of the various nitrogen species, TOC, and UV 254 within the wetland indicate that the nitrogen dynamics of the system are influenced both by variations in treatment plant loading, and, increasingly, by the degree of coverage and maturity of the emergent vegetation.

Ecological Engineering↗

USGS2000

Invertebrate assemblages and trace element bioaccumulation associated with constructed wetlands

Invertebrate assemblages were studied in eight monoculture wetland mesocosms constructed for wastewater treatment. Low concentrations of dissolved oxygen (D.O.) were measured in bulrush mesocosms while higher concentrations of D.O. were measured in open water mesocosms containing submerged pondweeds. Invertebrate taxa richness was positively related to D.O. concentrations that were, in turn, related to vegetation communities. Reference wetland sites contained a variety of plant species along with extensive open water areas. Invertebrate taxa richness was greater at reference sites than in any wastewater mesocosm. Invertebrate samples from the wastewater mesocosms and reference sites were analyzed for five trace elements. While the concentrations of aluminum, arsenic, mercury, and silver were below values harmful to wildlife, the concentrations of selenium reached levels of moderate concern on one occasion. Data from this study suggest that selenium bioaccumulation by invertebrates may be related to the type of vegetation community or detrital habitat type. Wetlands designed for invertebrate production for waterfowl should take into account the potential for low D.O. concentrations and trace element bioaccumulation associated with vegetation community types.

Wetlands↗

USGS2000

Investigation of denitrification rates in an ammonia-dominated constructed wastewater treatment wetland

Denitrification measurements were made under simulated field conditions using sediment cores and water collected from the Hemet/San Jacinto Multipurpose Demonstration Wetland (Riverside County, California, USA). The 9.9 ha constructed wetland is used to both polish ammonia-dominated secondary municipal effluent and provide migratory bird habitat. The wetland was originally constructed as a marsh-pond-marsh system in 1994. Over the period from January through March 1998, measured denitrification rates averaged 20.9 ± 20.9 μmol N m −2 h −1 within the emergent marsh portions of the wetland and 646 ± 353 μmol N m −2 h −1 in open water areas. The mean areal denitrification removal rate for this period was 0.70 kg N ha −1 d −1 , which accounted for about 8% of the total N removed by the wetland. Internal retention was the main N-removal mechanism. Synoptic water quality surveys indicated that denitrification was limited by a lack of nitrification within the wetland. Between April 1998 and January 1999, the wetland was reconfigured as a hemi-marsh system, having equal areas of interspersed emergent marsh and deep open water. In May 1999, measured denitrification rates averaged 1414 ± 298 μmol N m −2 h −1 within the emergent marsh zones and 682 ± 218 μmol N m −2 h −1 in the open water areas. The mean areal denitrification removal rate was 3.58 kg N ha −1 d −1 , which accounted for 40% of the total N removed by the wetland. A synoptic water quality survey indicated that nitrification within the wetland had been enhanced by the reduction of emergent macrophyte biomass and the increase in the area of interspersed deep open water. The modifications to the wetland shifted the nitrogen balance from a large internal storage component and a small denitrification component in 1998 to a more denitrifying system in 1999.

Wetlands↗