Although recent studies suggest contamination by bacteria and nitrate in private drinking water systems is of increasing concern, data describing contaminants associated with the corrosion of onsite plumbing are scarce. This study reports on the analysis of 2,146 samples submitted by private system homeowners. Almost 20% of first draw samples submitted contained lead concentrations above the United States Environmental Protection Agency action level of 15 μg/L, suggesting that corrosion may be a significant public health problem. Correlations between lead, copper, and zinc suggested brass components as a likely lead source, and dug/bored wells had significantly higher lead concentrations as compared to drilled wells. A random subset of samples selected to quantify particulate lead indicated that, on average, 47% of lead in the first draws was in the particulate form, although the occurrence was highly variable. While flushing the tap reduced lead below 15 μg/L for most systems, some systems experienced an increase, perhaps attributable to particulate lead or lead-bearing components upstream of the faucet (e.g., valves, pumps). Results suggest that without including a focus on private as well as municipal systems it will be very difficult to meet the existing national public health goal to eliminate elevated blood lead levels in children.

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Denitrifying bioreactors (DNBRs) are an emerging technology used to remove nitrate-nitrogen (NO) from enriched waters by supporting denitrifying microorganisms with organic carbon in an anaerobic environment. Field-scale investigations have established successful removal of NO from agricultural drainage, but the potential for DNBRs to remediate excess phosphorus (P) exported from agricultural systems has not been addressed. We hypothesized that biochar addition to traditional woodchip DNBRs would enhance NO and P removal and reduce nitrous oxide (NO) emissions based on previous research demonstrating reduced leaching of NO and P and lower greenhouse gas production associated with biochar amendment of agricultural soils. Nine laboratory-scale DNBRs, a woodchip control, and eight different woodchip-biochar treatments were used to test the effect of biochar on nutrient removal. The biochar treatments constituted a full factorial design of three factors (biochar source material [feedstock], particle size, and application rate), each with two levels. Statistical analysis by repeated measures ANOVA showed a significant effect of biochar, time, and their interaction on NO and dissolved P removal. Average P removal of 65% was observed in the biochar treatments by 18 h, after which the concentrations remained stable, compared with an 8% increase in the control after 72 h. Biochar addition resulted in average NO removal of 86% after 18 h and 97% after 72 h, compared with only 13% at 18 h and 75% at 72 h in the control. Biochar addition also resulted in significantly lower NO production. These results suggest that biochar can reduce the design residence time by enhancing nutrient removal rates.

[1] The automatic calibration software Parameter Estimation (PEST) was used in the hydrologic calibration of Hydrological Simulation Program-Fortran (HSPF), and the results were compared with a manual calibration assisted by the Expert System for the Calibration of HSPF (HSPEXP). In this study, multiobjective functions based on the HSPEXP model performance criteria were developed for use in PEST, which allowed for the comparison of the calibration results of the two methods. The calibrated results of both methods were compared in terms of HSPEXP model performance criteria, goodness-of-fit measures (R 2 , E, and RMSE), and base flow index. The automatic calibration results satisfied most of the HSPEXP model performance criteria and performed better with respect to R 2 , E, RMSE, and base flow index than manual calibration results. The results of the comparison with the manual calibration suggest that the automatic method using PEST may be a suitable alternative to manual method assisted by HSPEXP for calibration of hydrologic parameters for HSPF. However, further research of the weights used in the objective functions is necessary to provide guidance when applying PEST to surface water modeling.

Although extensive literature documents corrosion in municipal water systems, only minimal data is available describing corrosion in private water systems (e.g., wells), which serve as a primary source of drinking water for approximately 47 million Americans. This study developed a profiling technique specifically tailored to evaluate lead release in these systems. When applied in an intensive field study of 15 private systems, three patterns of lead release were documented: no elevated lead or lead elevated in the first draw only (Type I), erratic spikes of particulate lead (Type II), and sustained detectable lead concentrations (Type III). While flushing protocols as short as 15-30 s may be sufficient to reduce lead concentrations below 15 μg/L for Types I and III exposure, flushing may not be an appropriate remediation strategy for Type II exposure. In addition, the sustained detectable lead concentrations observed with Type III exposure likely result from corrosion of components within the well and therefore cannot be reduced with increased flushing. As profiling techniques are labor- and sample-intensive, we discuss recommendations for simpler sampling schemes for initial private system surveys aimed at quantifying lead and protecting public health.