Gordon Lewandowski

Reactor design for hazardous waste treatment using a white rot fungus.

Abstract Various nutrient media and reactor configurations were explored in order to grow the white rot fungus Phanerochaete chrysosporium, induce its active enzyme system, develop kinetic data for the degradation of 2-chlorophenol and use chemical engineering analysis to design an effective reactor. Preliminary experiments indicated that the biodegradation rate was improved by a factor of 40 when the fungus was immobilized. As a result, the project focused on a packed-bed reactor employing a silica-based porous support for the fungus, and a well-mixed reactor employing alginate beads as the immobilizing medium. Both were very effective in degrading 2-chlorophenol at inlet concentrations up to 520 ppm. Apparent Michaelis-Menten kinetic rate constants were developed for both reactors, which to our knowledge are the first reactor design parameters to be published for this fungus for treating a hazardous waste.

Kinetics of phenol biodegradation in the presence of glucose.

The kinetics of utilization of glucose, phenol, and their mixtures by Pseudomonas putida (ATCC 17514) were studied with a continuously aerated, jacketed batch reactor operating at 28°C and pH 7.2. It was found that when glucose is the sole carbon and energy source, the culture utilizes it following Monod kinetics. When phenol is the sole carbon and energy source, the culture biodegrades it following Andrews (inhibitory) kinetics. When both glucose and phenol are present in the medium, the culture uses them simultaneously but with lower specific rates. Reduction of the specific substrate utilization rates indicates that the two substances are involved in a cross‐inhibitory pattern which can be classified as uncompetitive. The values of the kinetic interaction constants suggest that glucose inhibits the specific rate of phenol removal much more than phenol inhibits the specific rate of glucose utilization. The results suggest that substitutable substrates which are dissimilar in origin and molecular structure may be involved in an uncompetitive cross‐inhibitory interaction when they are simultaneously removed. It is also concluded that the use of easily degradable substrates may not enhance the per‐unit amount of biomass removal of compounds which are classified as toxic. A general classification of kinetic interactions between substitutable resources is proposed.

Effect of pH on the anaerobic dechlorination of chlorophenols in a defined medium

Anaerobic dehalogenation of aromatic compounds is a well-documented phenomenon. However, the effects of operating parameters such as pH have received little attention despite their potential impact on treatment processes using dehalogenating organisms. In this work the effect of pH on the dehalogenation of 2,4,6-trichlorophenol (2,4,6-TCP) was studied using defined media containing one of several non-fermentable buffering agents (MOPS, TRICINE, BICINE, CHES), and no chloride ions. The dechlorination process was followed by monitoring the disappearance of 2,4,6-TCP, as well as the appearance of its dehalogenation products, i.e., 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP), and chloride ions. The results indicate that dechlorination occurs only if the pH is within the range 8.0–8.8. The newly formed 2,4-DCP was also dehalogenated in the process. However, even within this pH range dechlorination ceased when all 2,4,6-TCP and 2,4-DCP was converted to 4-CP. Stoichiometric amounts of all dehalogenation products (including chloride) could be recovered at any stage during the process. In addition, the biomass concentration was measured. After an initial lag phase, it appeared that the rate of dechlorination per unit biomass (proportional to the Cl− concentration divided by the biomass concentration) went through a rapid increase and then remained constant throughout the process. This indicates that the dechlorinating organism(s) either make up the entire population or constitute a stable fraction of it.

Dehalogenation and mineralization of 2,4,6-trichlorophenol by the sequential activity of anaerobic and aerobic microbial populations

SummaryA sequential anaerobic-aerobic treatment process that can mineralize 2,4,6-trichlorophenol has been developed. The process uses diluted anaerobic digester fluid as a culture medium, and a single microbial population enriched from the digester fluid for both the anaerobic and aerobic steps.

Biodegradation of benzene and a BTX mixture using immobilized activated sludge

Abstract Aerobic biodegradation was studied using activated sludge immobiized in calcium alginate gel. Hydrogen peroxide provided the dissolved oxygen source in a recirculation reactor that was operated batchwise and continuously. Responses to changes in benzene concentrations, flow rates, and biomass loadings were measured. Sixty percent of the benzene was biologically degraded in batch tests after 24 h using an initial concentration of 100 mg/L. A residence time of 17.14 h was required to biologically reduce benzene concentrations from 600 ppm to below the detection limit (1 ppm) during continuous operation. The system was modeled using Monod kinetics for substrate utilization. The apparent km values changed with biomass loadings, but were independent of the initial benzene concentrations. The aromatic species in BTX mixtures (i.e., benzene, toluene and o‐, m‐ and p‐xylene) can all be degraded at the same time.

Biodegradation of Mixed Wastes, in Continuously Operated Cyclic Reactors

The problem of simultaneous biodegradation of two dissimilar substrates in a continuously operated cyclic reactor was studied both at the theoretical and experimental levels using a simple model system. The system involved media containing mixtures of glucose and phenol as carbon sources. A pure culture ofPseudomonas putida (ATCC 17514) was employed. Independent kinetic experiments have revealed that glucose and phenol are involved in a crossinhibitory uncompetitive kinetic interaction. The dynamics of a cyclically operated reactor were analyzed using the principles of bifurcation theory for forced systems. Experimental results have confirmed the theoretical predictions. Implications of the results for the design of waste-treating facilities are discussed.

Biodenitrification Studies with a Bioreactor Operating in a Periodic Mode

Biodenitrification of nitrite and nitrate/nitrite mixtures was studied with a pure culture of Pseudomonas denitrificans (ATCC 13867), which is a strict anaerobe. The study involved theoretical analysis, and experimental verification of the biodenitrification process when a reactor operating in a periodic mode is employed. This reactor operates continuously in a cyclic mode, and each one of its cycles is made-up of three phases. During the first phase, the stream to be processed is fed to the reactor; reaction is initiated while the volume of the liquid hold-up of the reactor increases. During the second phase, reaction proceeds in the batch mode. During the third phase, part of the reactor contents are drawn-down till the volume of the reactor liquid hold-up returns to the value it had in the beginning of the cycle. At that point, the cycle starts repeating itself. A complete mathematical analysis of nitrite bioreduction is presented along with results from experiments performed with a 2 l reactor. Experimental results involve denitrification of water media containing either nitrite only, or mixtures of nitrate and nitrite. Theoretical predictions and experimental data are in excellent agreement.

Predictive Model for Jet Engine Test Cell Opacity

A mathematical model was developed to predict the plume opacity of jet engine test cells (it assumes that the cause of the plume visibility, i.e. opacity, is carbon particles). The data input required for the model includes: the particle density, concentration, and size distribution in the exhaust gas, and the effective stack diameter. Previous data obtained for J‐57 engines were used to test the model, and the difference between the theoretical and measured transmittance was generally within one percent. The model also predicts the theoretical effect of using a venturi scrubber to treat the exhaust emissions. These predictions indicate that even at the limits of operability, a scrubber would only achieve a minimal effect on the observed visibility.