John A. Roth

A Review of Corrosion Failure Mechanisms during Accelerated Tests Electrolytic Metal Migration

This paper presents an extensive literature review and assessment of corrosion failure mechanisms encountered during accelerated tests of microelectronic devices. The failure mechanism of primary emphasis is electrolytic metal migration. The metallurgies of interest are silver, gold, copper, and aluminum. Electrochemical investigations of dendritic growth are also reviewed. Mechanistic results from the electrochemical investigations are discussed in light of the empirical results of accelerated tests.

Response of dissolved oxygen to changes in influent organic loading to activated sludge systems

Abstract The major objective of this investigation was to examine the response of the activated sludge process to transient organic loadings and to evaluate the applicability of dissolved oxygen (DO) concentration and oxygen uptake rate as process control variables. A modified laboratory-scale activated sludge unit was used to continuously measure the ambient dissolved oxygen level. The change of the dissolved oxygen concentration responded to variations in the influent composition of the wastewater. First, the system was maintained at steady-state and system variables were measured for soluble TOC, MLVSS and oxygen uptake rate. The organic shock loading was induced by increasing or decreasing the baseline feeding of TOC concentration. As soon as a transient loading occurred the DO levels in the system were continuously monitored with the DO analyzer. A simplified material balance equation for dissolved oxygen in the system was developed and the dynamic behavior of oxygen uptake rate was examined. It was demonstrated that under transient conditions the changes in the dissolved oxygen concentration reflected the variations in the exogenous respiration rate of the biomass in the system due to fluctuations in the influent waste characteristics. Based upon the rapid response to the shock loading and the correlation of the change in the DO level to the magnitude of the shock loading, the two variables (DO concentration and oxygen uptake rate) generated from this biological monitor showed potential as a control variable for the activated sludge process.

Development of a continuous respirometer

Abstract A continuous oxygen uptake meter or continuous respirometer was developed which produced a rapid and reliable response to systemic shocks. The respirometer basically is a 101. Plexiglas laboratory activated sludge unit with a variable volume air tight side car. The feed enters the completely mixed aeration basin and is pumped into the side car. The side car is the site of the oxygen uptake measurements as indicated by a continuously monitoring dissolved oxygen probe. The system was most sensitive to changes in influent concentrations when run at an F / M = 0.1. Response time for a change in DO of 0.1 ppm was less than 4 min. The continuous respirometer was tested employing both synthetic and raw industrial wastes.

Removal rate of zinc from coal bottom ash in aqueous solutions

Abstract The leaching of inorganics including heavy metals from coal ashes has recently received extensive attention. This study was undertaken to understand the rate of leaching of metals from coal ash and the significant factors affecting the rate, and to develop an approach to predict leaching rates. The rate of leaching of zinc was characterized quantitatively for one coal bottom ash using a pseudokinetic mechanism. The resulting rate constants were correlated over a pH range of 1.3–9.3.

Modeling the dynamic response of an activated sludge process

Previously collected data describing aerated synthetic waste water, treated in a continuous stirred-tank reactor, are analyzed to understand better the dynamic response to step changes in the dilution rate,D. Comparing a change inD between steady states leads to hysteresis trajectories on both the graph of specific growth rate, μ, vs limiting substrate level (S) and the graph of (S) vs the cell level (X). Qualitative differences between the three different monitored cases will be compared to simulations of simple models at various dilution level changes in order to gain understanding of the dynamics of the process.