Transactions of the Institute of British Geographers

Fouling in membrane bioreactors used in wastewater treatment

Of the 117 stream and lake systems sampled nationwide, fish from Manoa Stream on Oahu, Hawaii, have consistently shown the highest Pb concentrations. Therefore a detailed study was conducted to examine total metal contents in bed sediments from a 5.8-km stretch of Manoa Stream. A total of 123 samples (<63 μm) were examined for 18 elements and 14 samples for 21 elements. Selected samples were also examined using different leach solutions to examine metal phase associations. All trace metal data, computations of enrichment ratios and the modified index of geoaccumulation point to mineralogical control for Cr and Ni; minor anthropogenic contamination for Ba, Cd, Cu, Hg and Zn; and a very strong contamination signal for Pb. Maximum Pb contents (up to 1080 mg kg−1) were associated with anthropogenic material dumping in minor tributaries, storm sewer sediments and sediments in the “lower” section of the basin. Proportionally Pb had the highest non-residual component of elements examined; dominantly in the reducible phase associated with Mn and amorphous Fe oxyhydroxides. The contamination signal was typically lowest in the “undisturbed” headwater reach of the basin (above 5.1 km) with significant increases throughout the “residential” and “commercial-institutional” zones of the mid-basin. The spatial pattern of bed sediment contamination and evidence from storm sewer-outlet sediments strongly indicates that Pb, and to a lesser degree some other metals, is still being transported to the stream and the primary agent is soil erosion and transport of metals sorbed to sediments. The primary source of sediment-associated metals is considered to be the automobile, though other minor sources can not be ruled out.

Bed sediment-associated trace metals in an urban stream, Oahu, Hawaii

/pdf/remote-sensing-of-the-environment-4yfxjaaswe.pdf

Remote sensing of the environment

C4.5: Programs for Machine Learning (書評)

Factors affecting the performance of stormwater treatment wetlands

The estrogen receptor agonist fate of hexane extracts from various locations and phases (liquid and solid) within one pilot-scale and two full-scale wastewater treatment facilities were examined by use of the receptor-binding yeast estrogen screen (YES assay). Estrogenic activity was found in samples that contained a high concentration of biological solids and was particularly high in the suspended solid fraction from biosolids treatment facilities. Mass balances revealed that the estrogenic activity associated with the processed biosolids constituted between 5 and 10% of the influent estrogenic activity, while the treated liquid effluent prior to disinfection contained between 26 and 43%. Overall, this suggests that between 51 and 67% of the estrogenic activity contained in the influent wastewater was either biodegraded during the wastewater or biosolids treatment processes or was unavailable to the extraction/detection procedure. In both aerobic and anaerobic digestion, mass balances revealed an increas...

Estrogen receptor agonist fate during wastewater and biosolids treatment processes: a mass balance analysis.

During 1975 and 1976 a distinct seasonal variation was observed in the concentrations of trihalomethanes (THMs) in the community water supply for approximately 640 000 residents of northern Virginia. Data were subsequently collected during a two-year monitoring program supported by the US Environmental Protection Agency,1 which involved the water system owned and operated by the Fairfax County Water Authority (FCWA) in Annandale, Va. The FCWA's raw water source is the Occoquan reser-, voir. At full pool the Occoquan holds 37 GL (9.8 bil gal) and drains approximately 1400 km(540 sq mi). From June through November 1975 the finished water THM concentrations corresponded nicely to the concentrations of chlorophyll-a measured in the reservoir (Fig. 1). Laboratory studies, designed to determine whether this presumptive link between algal growth and THMs could be verified experimentally, were completed in 1978.! The results of these studies are reported here. This paper presents laboratory data that illustrate the importance of both algal biomass and algal extracellular product (ECP) as THM precursors and discusses the significance of these data to community water supplies.

Algae as sources of trihalomethane precursors

Characterizing natural organic material from the Occoquan Watershed (Northern Virginia, US) using fluorescence spectroscopy and PARAFAC

An investigation was conducted on the pollutant removal performance of a constructed wetlands treating stormwater runoff from a residential townhome complex in northern Virginia. Constituent event mean concentrations for 33 runoff events between April 1996 and May 1997 were measured based on flow-weighted composite samples collected at the facility's inlet and outlet. With the results from a limited number of grab samples representing ungauged overland drainage from an adjacent wooded area, estimated removals were positive for most constituents and typically exceeded those obtained at a nearby companion wetland study site, consistent with expectations based on the relative ratios of wetland area to drainage area at the two sites. Median load removals of all constituents were greater for a subset of 22 storms that had inflow volumes less than the maximum volume of the marsh. Orthophosphate phosphorus and ammonia removals were significantly better during spring of 1996 than spring of 1997. Lysimeter data suggest a possible explanation for this, which is development of anaerobic conditions in the shallow sediments in 1997. Outlet concentrations of oxidized nitrogen were consistently lower in base flow than in storm samples, suggesting that removal of this constituent occurred primarily between, rather than during, storm events. Water Environ. Res., 72, 295 (2000).

Thomas J. Grizzard

Papers

Factors affecting the performance of stormwater treatment wetlands

Estrogen receptor agonist fate during wastewater and biosolids treatment processes: a mass balance analysis.

Algae as sources of trihalomethane precursors

Characterizing natural organic material from the Occoquan Watershed (Northern Virginia, US) using fluorescence spectroscopy and PARAFAC

Performance of a Constructed Wetlands in Treating Urban Stormwater Runoff