Comparing two empirical models used to predict process parameter dynamics during ozonation of synthetic dye wastewater.

Ozonation of a synthetic wastewater contaminated with acid yellow 17 dye and glucose was evaluated in a semi-batch bubble column. Data collected during this study suggests that the ozonation process removed color (represented as A400) more efficiently than chemical oxygen demand (COD) regardless of initial experimental conditions. With a 40-minute run time, the maximum A400 and COD removal efficiencies were 99.9 and 52.9%, respectively. Results indicated that the addition of COD to the system in the form of glucose had no effect on color removal efficiencies. The removal efficiencies of both color (A400) and COD in relation to the ozone utilized by the system were modeled using two previously derived empirical methods. Linear regression analysis was used to evaluate the effectiveness of both models to predict removal efficiencies of process parameters such as color and COD and to estimate ozone utilization. Results indicate both models predict color (A400) and COD removal as well as ozone utilization, but care should be taken when using the models to describe removal efficiencies when the wastewater inlet characteristics are variable.

Bench-scale ozonation study of waste activated sludge.

A bench-scale ozonation study was conducted on waste activated sludge (WAS) in a 10-L, clear PVC, semi-batch, bubble column reactor. Two separate runs were performed on 5-L samples of WAS obtained from the Rocky Creek Wastewater Treatment Plant (WWTP) in Macon, Georgia. The Rocky Creek facility uses the extended aeration activated sludge process to treat domestic wastewater. Ozone was sparged through a porous diffuser at an application rate of 0.0525 mg O(3) min(- 1) at contact times of 9 days and 12 days, respectively, during Runs #1 and #2. Parameters that were monitored during the study included: alkalinity, ammonia, conductivity, nitrite, nitrate, pH, phosphate, solids degradation rate coefficient (K(D)), soluble chemical oxygen demand (SCOD), total chemical oxygen demand (TCOD), total dissolved solids (TDS), total solids (TS), total volatile solids (TVS), turbidity, and unstirred sludge volume index (SVI(u)). Ozone was very effective at removing TCOD and TS. TCOD removals were 43% and 99% respectively for Runs #1 and #2. Total solids removal during Runs #1 and #2 was 50% and 95%, respectively. The degradation rate coefficient (K(D)) based on VSS was 0.17 days(- 1) and 0.54 days(- 1) for Runs #1 and #2. Both the nitrate and phosphate concentrations increased as ozone contact time increased during each run. The unstirred SVI decreased with an increase in ozone contact time, however, extended ozonation caused the SVI to increase. Actual ozone dosages for Runs #1 and #2 were 0.0036 and 0.011 mg O(3) per mg TS removed.

Performance assessment of major wastewater treatment plants (WWTPs) in the state of Georgia.

A survey was conducted to report on the types and efficiencies of various treatment technologies being used at major wastewater treatment plants (WWTPs) in the state of Georgia. Twenty-four, full-scale wastewater treatment facilities with a design capacity of 37,850 m(3) d(-1) (10 Mg d(-1)) or greater were evaluated. One year of operating data for the 2003 calendar year was obtained from discharge monitoring reports (DMRs) provided by the Georgia Environmental Protection Division (EPD) in Atlanta. Additional information was gathered about facility operations and the types of chemicals used through review of EPD files and interviews with plant personnel. Data evaluated were: influent and effluent five-day Biochemical Oxygen Demand (BOD(5)), influent and effluent total suspended solids (TSS), effluent ammonia nitrogen (NH(3)-N), and effluent Total Phosphorus (TP). Effluent requirements for BOD(5) or five-day carbonaceous biochemical oxygen demand (CBOD(5)), TSS, ammonia nitrogen (NH(3)-N), TP, and dissolved oxygen (DO) vary by facility. Time series plots showing average effluent parameter concentrations versus month indicate the effectiveness of wastewater treatment as a function of type of treatment technology and temperature. Probability plots highlight the relationship between various effluent parameters and associated treatment technology. Fourteen facilities met all permit requirements, whereas ten of the facilities reported violations with regard to flow and/or effluent parameters. Chemicals utilized, design capacity, and monthly effluent concentrations are presented in this study.

Ozonation of acid yellow 17 dye in a semi-batch bubble column.

A semi-batch bubble column was used to evaluate the effect of ozonation on the removal of acid yellow 17 dye from water. Results indicate that ozonation is very effective at removing acid yellow 17 dye from synthetic textile wastewater. The ozone consumed to apparent dye removal ratio ranged from 2 to 15,000 mg ozone per mg of dye decolorized and was dependent on both ozonation time and apparent dye concentration. The biodegradability of the dye wastewater was evaluated by monitoring changes in 5-day biochemical oxygen demand (BOD5) with respect to chemical oxygen demand (COD). Results indicate that the wastewater biodegradability increased with an increase in ozonation time. Film theory was used to kinetically model the gas-liquid reactions occurring in the reactor. Modeling results indicated that during the first 10-15 min of ozonation, the system could be characterized by a fast, pseudo-first-order regime. With continued ozonation, system kinetics transitioned through a moderate then to a slow regime. Successful modeling of this period required use of a kinetic equation corresponding to a more inclusive condition. Model results are presented.

Biofiltration of trichloroethylene-contaminated air: a pilot study.

This project demonstrated the biofiltration of a trichloroethylene (TCE)-contaminated airstream generated by air stripping groundwater obtained from several wells located at the Anniston Army Depot, Anniston, AL. The effects of several critical process variables were investigated to evaluate technical and economic feasibility, define operating limits and preferred operating conditions, and develop design information for a full-scale biofilter system. Long-term operation of the demonstration biofilter system was conducted to evaluate the performance and reliability of the system under variable weather conditions. Propane was used as the primary substrate necessary to induce the production of a nonspecific oxygenase. Results indicated that the process scheme used to introduce propane into the biofiltration system had a significant impact on the observed TCE removal efficiency. TCE degradation rates were dependent on the inlet contaminant concentration as well as on the loading rate. No microbial inhibition was observed at inlet TCE concentrations as high as 87 parts per million on a volume basis.

Terminal gas velocity during laparoscopy.

STUDY OBJECTIVE: To assess the effect of port size in relation to laparoscopic gas flow and to determine the terminal velocity of gas flow during insufflation. DESIGN: Analysis and mathematical modeling of gas flow characteristics. SETTING: University biomedical engineering department. INTERVENTION: Analytic calculations including Bernoulli's equation to describe gas volumetric flow and velocity as it exits laparoscopic intraabdominal entrance sites. MEASUREMENTS AND MAIN RESULTS: Mathematical modeling showed that terminal velocity of gas entering the abdomen through needles or trocars reaches a practical limit depending on size and configuration of the gas exit site, amount of turbulence, length of delivery port, and gas flow. Flow rate was evaluated for circles of 2, 5, and 10 mm and annular slots of 0.1- to 0.01-mm thickness. CONCLUSION: Resistance to gas flow increases and gas exiting terminal velocity increases as the effective area of the gas exit site decreases. Depending on the configuration of variable parameters, gas flow can reach 30 m/second.