Mark R. Matsumoto

The effects of ozonated irrigation water on soil physical and chemical properties

Abstract There are reports that ozone in irrigation water can improve crop vigor, reduce insect and disease, enhance water penetration, and reduce fertilizer needs. It has been noted that ozone treated field soils seem spongier and have less standing water. Here we report on a laboratory column study on the effects of ozonated irrigation water on hydraulic conductivity, soil hardness (aggregate strength), clay dispersion, soil swelling, and changes to the chemical composition of the leachate water. Additional batch studies were conducted to characterize the factors affecting the rate of ozone loss in soil/water suspensions and the results used in a mathematical model to predict ozone movement into a soil. We found that ozone increased the saturated hydraulic conductivity and decreased clay dispersion in a loamy soil, but not if the soil had an exchangeable sodium percentage >15%. In two other soils tested, the ozone effects were mixed or insignificant. In every soil tested, the drainage water from the ozone-treated columns had lower pHs and higher electrolyte concentrations. This is attributed to organic matter oxidation and the weak acid properties of ozone. The rate of ozone degradation in soil water could be modeled using the total organic carbon content of the soil, the pH, and the soil/water ratio. Based on the rate of ozone loss in soil/water suspensions, the calculated depth of ozone penetration during the initial wetting of the soil was <2 mm, indicating that the reaction may be limited to the surface.

Comparison of PCR‐DGGE and Selective Plating Methods for Monitoring the Dynamics of a Mixed Culture Population in Synthetic Brewery Wastewater

Enrichment of an activated sludge inoculum in synthetic brewery wastewater, which included glucose, maltose, and ethanol, was conducted in batch experiments to identify the dominant microbes present, to determine methodologies capable of monitoring the mixed culture population dynamics, and to determine the consortiumapos;s substrate degradation behavior. These results and methodologies were subsequently used in the determination of the population dynamics of suspended and attached microorganisms in a sequencing batch system in the second part of this research work. The three‐membered microbial community comprised two bacterial and one fungal species that were identified as Acinetobacter sp., Enterobacter sp., and Candida sp. PCR‐DGGE and plating on selective media were used to track the population dynamics of the consortium during the degradation of different substrates in synthetic wastewater containing glucose, maltose, and ethanol. Enterobacter sp. could degrade glucose and maltose but not ethanol, whereas Acinetobacter and Candida could degrade all three carbon sources. In buffered batch mixed culture experiments, Enterobacter was the predominant bacterium until the sugar concentrations decreased to levels that enabled Acinetobacter and Candida to degrade ethanol. PCR‐DGGE was effective for detecting the dominant species, but culture‐based methods were more accurate for monitoring the population dynamics of these microorganisms during growth in the wastewater medium.

Application of electrochemical depassivation in PRB systems to recovery Fe 0 reactivity

Permeable reactive barriers (PRBs) show remarkable Cr(VI) removal performance. However, the diminished removal rate because of mineral fouling over time is the bottleneck for application of PRBs. The present study demonstrated that electrochemical depassivation was effective for recovering the Fe0 reactivity, and minerals can be cleaned layer by layer with no secondary ion contamination and no transformation from Cr(III) to Cr(VI). The removal recovery rate increased with increasing electrolysis voltage before reaching the optimal electrolysis voltage, and then decreased as the electrolysis voltage further increased. The recovery effect at electrolysis voltages of 5, 10, and 15 V show the same trend as a function of electrolysis time, where recovery rate first increased and then decreased after reaching the optimal electrolysis time. The Cr(VI) removal rate significantly decreased with increasing electrolysis distance. Furthermore, Fe0 brush meshes electrode, Fe0 fillings, and polyvinyl chloride (PVC) meshes separators were combined to create an Electro-PRB configuration for the caisson excavation construction technique, which lays the foundation for establishment of promising Electro-PRB systems to treat Cr(VI)-contaminated groundwater.Graphical abstract

A Kinetic Model for Suspended and Attached Growth of a Defined Mixed Culture

Kinetic experiments were carried out in a semicontinuous wastewater treatment process called self‐cycling fermentation (SCF) using a defined mixed culture and various concentrations of synthetic brewery wastewater. The same consortium, which had been previously identified as Acinetobacter sp., Enterobacter sp., and Candida sp., were used in these experiments. The overall rate of substrate removal was attributable to both suspended microbes and the biofilm that formed during the treatment process. A rate expression was developed for the SCF system for a range of synthetic wastewaters containing glucose and various initial concentrations of ethanol and maltose. The data indicated that substrate removal by the suspended cells was directly related to the biomass concentration. However, substrate removal by the biofilm was apparently not affected by the biofilm thickness and was a function of substrate concentration only.

Preliminary Study of Biological Activated Carbon Treatment for Removing MTBE from Groundwater

Methyl tert-butyl ether (MTBE) is a common additive for producing a clean burning fuel with a higher Octane number and less emissions. Batch adsorptive capacity, continuous flow breakthrough and biological activated carbon (BAC) treatment experiments were conducted to compare the adsorptive capacities of four activated carbons for MTBE, to obtain the adsorptive capacity indicators useful for predicting the carbons MTBE capacity and its utilization in actual treatment, and to establish an effective start-up procedure to enable an activated carbon adsorber to function as the desired BAC system for long term treatment without needing carbon replacement. Although the coconut carbon YKs adsorptive capacity for MTBE was much larger, its column loading was only 20% higher than the coal carbon Coal because of its slower intraparticle diffusion rate due to the lack of larger micropores; the YK loading increased >60% when the adsorber flowrate was reduced by 50%. Two inoculation methods were utilized to seed the MTBE degrading bacteria present in the spent activated carbon (Spent) obtained from a remediation site; circulation of the supernatant of the Spent-water mixture to seed the adsorber failed, while the three Spent-filled adsorbers (65, 40 and 100%; the balance was YK) became BAC systems after the start-up period of 5-7 weeks during which the MTBE concentration of the feed increased from 0 to 30 mg/L. Each Spent-filled adsorber removed >50% of MTBE present in the feed (up to 40 mg/L); the more the Spent filled, the faster the BAC function was established.