Engineered and Environmental Controls of Microbial Denitrification in Established Bioretention Cells.

Bioretention cells (BRCs) are effective tools for treating urban stormwater, but nitrogen removal by these systems is highly variable. Improvements in nitrogen removal are hampered by a lack of data directly quantifying the abundance or activity of denitrifying microorganisms in BRCs and how they are controlled by original BRC design characteristics. We analyzed denitrifiers in twenty-three BRCs of different designs across three mid-Atlantic states (MD, VA, and NC) by quantifying two bacterial denitrification genes ( nirK and nosZ) and potential enzymatic denitrification rates within the soil medium.

Chemistry and transport of metals from entrenched biosolids at a reclaimed mineral sands mining site.

Deep row incorporation of biosolids is an alternative land treatment method whose typically high rates may result in elevated pollutant transport. The objectives of this research were to compare the effects of entrenched biosolids stabilization type and rate on heavy metal chemistry and mobility. Two rates each of Alexandria (Virginia) Sanitation Authority anaerobically digested (213 and 426 dry Mg ha(-1)) and Blue Plains (Washington, DC) lime-stabilized (329 and 657 dry Mg ha(-1)) biosolids were placed in trenches at a mineral sands mine reclamation site in Dinwiddie County, Virginia, in summer 2006.

Repeated compost application effects on phosphorus runoff in the Virginia Piedmont.

Increasing amounts of animal and municipal wastes are being composted before land application to improve handling and spreading characteristics, and to reduce odor and disease incidence. Repeated applications of composted biosolids and manure to cropland may increase the risk for P enrichment of agricultural runoff. We conducted field research in 2003 and 2004 on a Fauquier silty clay loam (Ultic Hapludalfs) to compare the effects of annual (since 1999) applications of composted and uncomposted organic residuals on P runoff characteristics.

Decomposition and plant-available nitrogen in biosolids: laboratory studies, field studies, and computer simulation.

This research combines laboratory and field studies with computer simulation to characterize the amount of plant-available nitrogen (PAN) released when municipal biosolids are land-applied to agronomic crops. In the laboratory studies, biosolids were incubated in or on soil from the land application sites. Mean biosolids total C, organic N, and C to N ratio were 292 g kg(-1), 41.