[CCoE Notice] Thesis Defense: Charan Tanneru, 4/9/2014 at 10:00 AM

[Williams, Stephanie]

Title:  Virus Control by Electrochemical Coagulation and Microfiltration

Presenter:
Charan Tanneru
Environmental Engineering, PhD
University of Houston


Date: April 9th, 2014
Time: 10:00 AM-12:00 PM
Place: CEE Conference Room, N107


Abstract:

Bench-scale experiments were performed to evaluate microorganism control by electrochemical coagulation and membrane microfiltration. Natural organic matter (NOM) present in natural waters appears to reduce the effectiveness of iron electrocoagulation pretreatment to microfiltration for MS2 virus control by complexing ferrous ions generated at the sacrificial anode during electrolysis. This inhibits (i) Fe2+ oxidation, precipitation, and virus destabilization and (ii) virus inactivation through reactive oxygen species intermediates or by direct interactions with Fe2+ ions. In contrast, higher reductions in MS2 virus concentrations were obtained when aluminum was electrochemically added to surface water. Sweep flocculation was the primary virus destabilization mechanism with secondary contributions from charge neutralization. Direct evidence for virus enmeshment in flocs was provided by two independent methods: quantitative elution using beef extract at elevated pH and quantitating fluorescence from labeled viruses. Monotonically increasing adhesion force between viruses immobilized on AFM tips and floc surfaces with increasing electrocoagulant dosage was measured by atomic force microscopy, which was accompanied by decreasing magnitude of the zeta potential (→ 0) and increasing NOM removal. Hence, virus uptake mechanisms also include charge neutralization and hydrophobic interactions with NOM on floc surfaces. Evidence for virus inactivation was also obtained during iron and aluminum electrocoagulation of synthetic water spiked with viruses. Free chlorine was produced during aluminum electrolysis of saline solutions via oxidation of chloride ions, which inactivated MS2 viruses. Capsid protein modifications probed using Fourier transform infrared spectroscopy (FTIR) revealed significant oxidative modification in amide I and II (1700-1500 cm-1) region. Evidence for genome damage was obtained using quantitative real time polymerase chain reaction (RT-PCR). Hence, alterations of capsid proteins and loss of genome structural integrity both contributed to inactivation.


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