George A. O’Connor

Toxicity and bioaccumulation of biosolids-borne triclocarban (TCC) in terrestrial organisms

Triclocarban (TCC) toxicity and bioaccumulation data are primarily limited to direct human and animal dermal exposures, animal ingestion exposures to neat and feed-spiked TCC, and/or aquatic organism exposures. Three non-human, terrestrial organism groups anticipated to be the most highly exposed to land-applied, biosolids-borne TCC are soil microbes, earthworms, and plants. The three ecological receptors are expected to be at particular risk due to unique modes of exposure (e.g. constant, direct contact with soil; uptake of amended soil and pore water), inherently greater sensitivity to environmental contaminants (e.g. increased body burdens, permeable membranes), and susceptibility to minute changes in the soil environment. The toxicities of biosolids-borne TCC to Eisenia fetida earthworms and soil microbial communities were characterized using adaptations of the USEPA Office of Prevention, Pesticides, and Toxic Substances (OPPTS) Guidelines 850.6200 (Earthworm Subchronic Toxicity Test) and 850.5100 (Soil Microbial Community Toxicity Test), respectively. The resultant calculated TCC LC50 value for E. fetida was 40 mg TCC kg amended fine sand(-1). Biosolids-borne TCC in an amended fine sand had no significant effect on soil microbial community respiration, ammonification, or nitrification. Bioaccumulation of biosolids-borne TCC by E. fetida and Paspulum notatum was measured to characterize potential biosolids-borne TCC movement through the food chain. Dry-weight TCC bioaccumulation factor (BAF) values in E. fetida and P. notatum ranged from 5.2-18 and 0.00041-0.007 (gsoil gtissue(-1)), respectively.

Aluminum water treatment residuals as permeable reactive barrier sorbents to reduce phosphorus losses

Two aluminum water treatment residuals (Al-WTRs) from water treatment plants in Manatee County, FL and Punta Gorda, FL were evaluated as potential permeable reactive barrier (PRB) media to reduce groundwater phosphorus (P) losses. Short-term (<24h) P sorption kinetics and long-term P sorption capacity were determined using batch equilibration studies. Phosphorus desorption was characterized following P loadings of 10, 20, 30, 40 and >70 g kg(-1). Sorption and desorption studies were conducted on the <2.0mm material and three size fractions within the <2.0mm material. The effect of dissolved organic carbon (DOC) on P retention was determined by reacting Al-WTRs with P-spiked groundwater samples of varying initial DOC concentrations. Phosphorus sorption kinetics were rapid for all size fractions of both Al-WTRs (>98% P sorption effectiveness at shaking times ≥2 h). The effect of DOC was minimal at <150 mg DOCL(-1), but modest reductions (<22%) in P sorption effectiveness occurred at 587 mg DOC L(-1). The P sorption capacities of the Manatee and Punta Gorda Al-WTRs (<2.0mm) are ∼44 g kg(-1) and >75 g kg(-1), respectively, and the lifespan of an Al-WTR PRB is likely many decades. Desorption was minimal (<2% of the P sorbed) for cumulative P loadings <40 g kg(-l), but increased (<9% of the P sorbed) at cumulative P loads >70 g kg(-1). The <2.0mm Manatee and Punta Gorda Al-WTRs are regarded as ideal PRB media for P remediation.

SUSTAINABLE NUTRIENT MANAGEMENT PACKAGE FOR COST-EFFECTIVE BIOENERGY BIOMASS PRODUCTION

Commercial fertilizer (particularly nitrogen) costs account for a substantial portion of the total production costs of cellulosic biomass and can be a major obstacle to biofuel production. In a series of greenhouse studies, we evaluated the feasibility of co-applying Gibberellins (GA) and reduced nitrogen (N) rates to produce a bioenergy crop less expensively. In a preliminary study, we determined the minimum combined application rates of GA and N required for efficient biomass (sweet sorghum, Sorghum bicolor) production. Co-application of 75 kg ha−1 (one-half of the recommended N rate for sorghum) and a modest GA rate of 3 g ha−1 optimized dry matter yield (DMY) and N and phosphorus (P) uptake efficiencies, resulting in a reduction of N and P leaching. Organic nutrient sources such as manures and biosolids can be substituted for commercial N fertilizers (and incidentally supply P) to further reduce the cost of nutrient supply for biomass production. Based on the results of the preliminary study, we conducted a second greenhouse study using sweet sorghum as a test bioenergy crop. We co-applied organic sources of N (manure and biosolids) at 75 and 150 kg PAN ha−1 (representing 50 and 100% N rate respectively) with 3 g GA ha−1. In each batch of experiment, the crop was grown for 8 wk on Immokalee fine sand of minimal native fertility. After harvest, sufficient water was applied to soil in each pot to yield ∼1.5 L (∼0.75 pore volume) of leachate, and analyzed for total N and soluble reactive P (SRP). The reduced (50%) N application rate, together with GA, optimized biomass production. Application of GA at 3 g ha−1, and the organic sources of N at 50% of the recommended N rate, decreased nutrient cost of producing the bioenergy biomass by ∼

Fate and Potential of Xenobiotics

375 ha−1 (>90% of total nutrient cost), and could reduce offsite N and P losses from vulnerable soils.

Screening Perennial Warm-Season Bioenergy Crops as an Alternative for Phytoremediation of Excess Soil P

The potentially toxic organics (TOs) that can be present in agricultural, municipal, and industrial wastes number in the thousands. Extensive data bases show that TO concentration in biosolids are low; much less data is available for other wastes, but the consensus is that TO concentrations are similar. TO reactions in wastes/soils also are expected to be similar to soil/biosolid — TO reactions. Thus, the sizable data, research, and risk assessment base for biosolids seems applicable to many other wastes. If TO variety and concentrations in a waste are similar to those in biosolids, risk to humans, animals, and the environment is minimal. Various fate processes of TO in soil/waste mixtures, as well as risk assessment for TOs in biosolids, are reviewed to support the conclusion. Research needs are identified to confirm the conclusion.