Geology topics

Claude E. Boyd

Publications and source records attributed to Claude E. Boyd.

5 recordsLinked to original sources

USGS2017

Performance and application of a fluidized bed limestone reactor designed for control of alkalinity, hardness and pH at the Warm Springs Regional Fisheries Center

Springs serving the Warm Springs Regional Fisheries Center, Warm Springs, Georgia, have pH, alkalinity, and hardness levels thatlie under the range required for successful fish propagation while free CO 2 is well above allowable targets. We evaluate a pretreatment process that exploits limestone’s (CaCO 3 ) ability to react away hydrogen ions (H + ) and carbon dioxide (CO 2 ) while increasing alkalinity (HCO 3 − ) and calcium (Ca2+) concentrations, i.e. CaCO 3 + H + ↔ HCO 3 − + Ca 2+ CaCO 3 + CO 2 + H 2 O ↔ Ca 2+ + 2HCO 3 − Limestone sand was tested in both pilot and full scale fluidized bed reactors (CycloBio®). We first established the bed expansion characteristics of three commercial limestone products then evaluated the effect of hydraulic flux and bed height on dissolution rate of a single selected product (Type A16 × 120). Pilot scale testing at 18C showed limestone dissolution rates were relatively insensitive to flux over the range 1.51–3.03 m 3 /min/m 2 but were sensitive (P < 0.001; R 2 = 0.881) to changes in bed height (BH, cm) over the range 83–165 cm following the relation: (Alkalinity, mg/L) = 123.51 − (3788.76 (BH)). Differences between filtered and non-filtered alkalinity were small(P > 0.05) demonstrating that limestone was present in the reactor effluent primarily in the form of dissolved Ca(HCO 3 ) 2 . Effluent alkalinity exceeded our target level of 50 mg/L under most operating conditions evaluated with typical pilot scale values falling within the range of 90–100 mg/L despite influent concentrations of about 4 mg/L. Concurrently, CO 2 fell from an average of 50.6 mg/L to 8.3 mg/L (90%), providing for an increase in pH from 5.27 to a mean of 7.71. The ability of the test reactor to provide changes in water chemistry variables that exceeded required changes allowed for a dilution ratio of 0.6. Here, alkalinity still exceeded 50 mg/L, the CO 2 concentration remained well below our limit of 20 mg/L (15.4 mg/L) and the pH was near neutral (7.17). Applying the dilution ratio of 0.6 in a full scale treatment plant at the site reduced by 40% the volume of spring water that is directed through each of three parallel reactors that combined react away 49,000 kg of limestone/yr.

Aquacultural Engineering↗

USGS1994

Gas supersaturation in surface waters of aquaculture ponds

During the 1988 and 1989 growing seasons, dissolved gas pressures were measured in 0·04 ha to 0·06 ha earthen ponds (n = 17) used to produce channel catfish or bluegill sunfish, both with and without supplemental aeration. Surface waters in early morning hours (0630 to 0830 h) were typically saturated with nitrogen (N 2 ) and argon (Ar), undersaturated with dissolved oxygen (DO), and supersaturated with carbon dioxide. Total gas pressures (ΔP) were low, averaging −40 mmHg (range −127 to 62 mmHg). During afternoon hours (1300 to 1500 h) ΔP increased to a mean of 111 mmHg (range −46 to 334 mmHg); 34% of afternoon ΔP values were above that known to cause mortality in channel catfish during continuous exposure bioassays (115 mmHg), yet no excessive mortality was observed. High afternoon ΔP values resulted from DO supersaturation caused by phytoplankton photosynthesis and, to a lesser extent, N 2 and Ar supersaturation. The N 2 and Ar supersaturation apparently resulted from cooling and saturation of surface waters with air during evening hours, and the subsequent increase in water temperature during daylight hours (daily increase X "> X = 3·4°C; range 1·1 to 7·9°C) without sufficient gas release.

Aquacultural Engineering↗

USGS1990

Gas transfer within a multi-stage packed column oxygen absorber: Model development and application

A packed column oxygen obsorber was developed in which oxygen flow is directed, in serial reuse, through parallel packed column stages receiving equal portions of the liquid being treated. The relative performance of the absorber was established using a computer simulation program employing finite difference-mass transfer calculations. The program was calibrated using packing specific mass transfer coefficients derived from pilot scale test data. A separate series of tests served to verify model assumptions and performance predictions. Simulation data indicated multi-stage operation can substantially reduce the column height required to achieve a selected oxygen absorption efficiency (AE); for example, the column height required to achieve an AE of 76·5% with an inlet volumetric oxygenwater ratio of 0·008 (column packing, 3·81 cm plastic ACTIFIL ® ; water temperature, 20°C; influent dissolved oxygen, 9·08 mg/litre; operating pressure (absolute), 760 mm Hg) was 0·27 m using a 10-stage system versus 1·39 m using a single-stage absorber. Reductions in column height achieved were related to oxygen and water feed rates, number of stages employed, mass transfer characteristics of the column packing used, and concentrations of dissolved gases in the liquid being treated.

Aquacultural Engineering↗

USGS1990

Modeling the effects of serial off-gas reuse on the performance of a hooded surface oxygen obsorption system

A numerical model was used to evaluate the performance of a surface agitation system designed to contact commercial oxygen with water. The modeled system was unique in that oxygen-rich off-gas, normally discharged to the atmosphere, was directed in serial reuse through additional contact stages receiving untreated water. A correlation between the agitator mass-transfer coefficient and power demand, needed to calibrate the model, was established using a single-stage (37 W) contactor of 1·18 m 3 capacity. Additional tests, conducted with both single and three-stage equipment, verified model assumptions and performance predictions. Simulation runs indicated oxygen flow or power input required to meet a given effluent dissolved gas criterion can be substantially reduced by the off-gas reuse step; for example, to achieve an effluent dissolved oxygen of 24·1 mg/litre with a single stage agitator the oxygen feed rate needed was 61·5% greater than that required by a six-stage system receiving the same total power input (standard aeration efficiency, 0·5 kg/kW h; water flow rate, 100 litre/min; influent dissolved oxygen, 9·08 mg/litre at 15°C). The savings achieved increased with (1) greater target effluent dissolved oxygen concentrations, (2) lower oxygen feed rates, (3) higher input power levels, and (4) number of contact stages.

Aquacultural Engineering↗

USGS1989

Gas phase axial dispersion in a packed column oxygen absorber

Gas phase axial dispersion was characterized within an enclosed packed column receiving oxygen and water under counter-current flow conditions. Steady-state gas phase profiles (longitudinal) were measured during a series of 90 column runs in which, at each of three bed depths (0·362, 0·699, and 1·041 m), all combinations of the following independent variables were tested: influent volumetric oxygen-liquid ratio, 0·8, 1·6, 2·6, 4·0, and 8·0%; hydraulic loading, 32·0 and 61·2 kg/m 2 s; and packing type, 2·54 cm Tri-Pack ® , 3·81 cm Nor-Pac ® and 5·08 cm Nor-Pac ® . Over the range of operating conditions tested, gas phase mixing was extensive and for all practical purposes could be considered complete. A homogeneous gas phase within the column, unlike true counter-current flow, results in an exponential decay in dissolved gas deficits as the liquid passes through the packing. Thus, increases in packed bed depth will result in diminishing increases in gas absorption/desorption.

Aquacultural Engineering↗