Gary C. Schafran

Removal of copper and cadmium from aqueous solution using switchgrass biochar produced via hydrothermal carbonization process

Biochar produced from switchgrass via hydrothermal carbonization (HTC) was used as a sorbent for the removal of copper and cadmium from aqueous solution. The cold activation process using KOH at room temperature was developed to enhance the porous structure and sorption properties of the HTC biochar. The sorption efficiency of HTC biochar and alkali activated HTC biochar (HTCB) for removing copper and cadmium from aqueous solution were compared with commercially available powdered activated carbon (PAC). The present batch adsorption study describes the effects of solution pH, biochar dose, and contact time on copper and cadmium removal efficiency from single metal ion aqueous solutions. The activated HTCB exhibited a higher adsorption potential for copper and cadmium than HTC biochar and PAC. Experiments conducted with an initial metal concentration of 40 mg/L at pH 5.0 and contact time of 24 h resulted in close to 100% copper and cadmium removal by activated HTCB at 2 g/L, far greater than what was observed for HTC biochar (16% and 5.6%) and PAC (4% and 7.7%). The adsorption capacities of activated HTCB for cadmium removal were 34 mg/g (0.313 mmol/g) and copper removal was 31 mg/g (0.503 mmol/g).

Nitrogen removal assessment through nitrification rates and media biofilm accumulation in an IFAS process demonstration study.

An IFAS demonstration study was conducted at the 76,000 m(3)/day (20MGD) James River Wastewater Treatment Plant (JRTP) located in Newport News, Virginia by converting one fully-aerobic conventional aeration basin with dedicated secondary clarification to a 7041 m(3)/day (8404 m(3)/day max month) IFAS train in a modified Ludzack-Ettinger (MLE) configuration. During the study, biomass concentrations on the biofilm carriers were monitored (weekly) as well as nitrogen species concentrations in the IFAS reactor to quantify the nitrogen transformations occurring within the demonstration tank. In a related effort, nitrification kinetics for ammonia and nitrite oxidizing bacteria were monitored on a weekly basis for IFAS media alone, IFAS process mixed liquor without media, and IFAS mixed liquor and media together in an effort to identify the location of nitrification activity (i.e. on the media or in the suspended culture) in the IFAS process. Biomass quantity on the media was generally observed to be inversely related to temperature except during a period when an auxiliary carbon source contaminated with fungi was introduced. Both ammonia oxidizing and nitrite oxidizing bacterial activity were elevated on the carriers compared to the suspended culture (AOB(media): 4.97 mgNOx/gMLSS/hr; AOB(suspended): 1.72 mgNOx/gMLSS/hr; NOB(media): 7.55 mgNOx/gMLSS/hr; NOB(suspended): 0.82 mgNOx/gMLSS/hr) during all periods of the study. In-basin nitrification rates calculated based on nitrogen profiling efforts averaged 0.90 mgNOx/m(2)/day which was in good agreement with the average of 0.89 mgNOx/m(2)/day for IFAS mixed liquor and media from batch testing.

Flow path-composition relationships for groundwater entering an acidic lake

The relationship of groundwater flow paths to the acid/base status and composition of groundwater was examined by directly monitoring groundwater inputs to an acidic Adirondack, New York, lake (Darts Lake). Groundwater inputs near the shoreline of the lake were acidic throughout the year ( pH 40 [mu]eq L[sup [minus]1]). Elevated concentrations of basic cations and alkalinity as well as lower concentrations of organic anions and sulfate were characteristic of deep ground water entering the lake at the study site. Spatial variability of groundwater chemistry was found to be substantial over a relatively short distance (<6 m) from the lake shoreline and indicates that input, to the lake of components dissolved in groundwater are highly flow path dependent.

Spatial and temporal variations in aluminum chemistry of a dilute, acidic lake

Elevated concentrations of Al have been observed in acidic surface waters. An assessment of the chemistry of aqueous Al is of interest because of its role as a toxicant to aquatic organisms, a pH buffer, and an adsorbent of orthophosphate and organic carbon. In this investigation we evaluated the spatial and temporal fluctuations of Al forms in an acidic drainage lake.High concentrations of NO3− (51.0 ± 11 μmol l−1), H+ (14.9 ± 3.5 μmol l−1), and Al (19.6 ± 3.5 μmol l−1) were introduced to Darts Lake through drainage water during the snowmelt period. During low flow periods microbially mediated depletions of nitrate served to neutralize H+ and aluminum base neutralizing capacity. Thus in Darts Lake, NO3− transformations were extremely important in regulating short-term changes in pH and subsequent changes in the inorganic forms of Al. During stratification periods Al appeared to be non-conservative within the lake system. Although we know very little about the character and transformations of alumino-organic solutes, these substances were correlated with dissolved organic carbon (DOC) concentrations. Alumino-organic substances appear to be introduced to the lake from both drainage water and sediments.

Comparison of terrestrial and hypolimnetic sediment generation of acid neutralizing capacity for an acidic adirondack lake

The importance of in-lake generation of acid neutralizing capacity (ANC) to the neutralization of acidic deposition has been determined for an acidic Adirondack (NY) lake relative to its surrounding watershed. Microbial processes within the sediments of Darts Lake significant altered the aqueous chemistry of the hypolimnion. Reduction of NO/sub 3//sup -/ and SO/sub 4//sup 2 -/ and the production of NH/sub 4//sup +/ contributed 45, 14, and 32%, respectively, to the production of hypolimnetic ANC. The reduction of NO/sub 3//sup -/ was a more significant source of ANC generation than has been reported in other lake districts. On an areal basis, in-lake ANC generation (2990 equiv ha/sup -1/ yr/sup -1/) was greater than terrestrial ANC production (1204 equiv ha/sup -1/ yr/sup -1/). However on a watershed basis, in-lake ANC generation was minor (< 5%) due to the short hydraulic retention time of Darts Lake. Neutralization of acidic precipitation in the Adirondack region predominately occurs in the terrestrial system since the hydraulic retention time of Adirondack lakes is short.

CHEMICAL STRATIFICATION IN THE SENECA/OSWEGO RIVERS (NY)*

AbstractThe occurrence and characteristics of chemically-based density stratification in portions of the Seneca and Oswego Rivers, downstream of ion-polluted Onondaga Lake, are described for seven different days in the summer and fall of 1978 and 1981, which covered a wide range of river flows. The results indicate that chemically-based density stratification occurs routinely in the Seneca River downstream of the lake inflow, in response to a continuous chemically-based density difference between the two systems of 0.0015 to 0.0030 g cm−3. The persistence of the phenomenon, and therefore the longitudinal range over which the river stratification occurred, was dependent on the velocity of river flow and the magnitude of the density gradient that bordered the upper river water and the lower released lake water. During the low flows common to summer the stratification extended approximately 14 km downstream to a dam, and 3 km upstream, of the lake outlet — river junction. Vertical mixing between the stratified layers increased as the flow in the Seneca River increased, and as the vertical density gradient decreased. A dimensionless group,

Partitioning light attenuation in an acidic lake

\frac{D}{{V\left( {\frac{\rho }{{\Delta _\rho /\Delta _z }}} \right)}}

System and method for high-voltage pulse assisted aggregation of algae

where: D = apparent vertical diffusion (m2 hr−1), V = average velocity of the overlying river flow (m hr−1 ), p = density at the interface between the stratified layers (g cm−3), and Ap/Az = density gradient between the stratified layers (g cm−3 m−1), was found to be constant for summer low flow conditions for a 6.5 km length of the Seneca River, thus quantifying the interaction between vertical mixing and the included influences for that portion of the river. The occurrence of chemical stratification in the river had dramatic implications on the corresponding distribution of dissolved oxygen (DO). The isolation of the organically enriched lake water in the lower layer enhanced the depletion of DO there, which resulted in the development of substantial (> 4.0 mg 1−1 ) DO stratification downstream of the discharge from the lake during summer low flow periods.