New manuscript out from Dr. Xiao Ma
Free chlorine and monochloramine inactivation kinetics of Aspergillus and Penicillium in drinking water
Fungi are near-ubiquitous in potable water distribution systems, but the disinfection kinetics of commonly identified fungi are poorly studied. In the present study, laboratory scale experiments were conducted to evaluate the inactivation kinetics of Aspergillus fumigatus, Aspergillus versicolor, and Penicillium purpurogenum by free chlorine and monochloramine. The observed inactivation data were then fit to a delayed Chick-Watson model. Based on the model parameter estimation, the Ct values (integrated product of disinfectant concentration C and contact time t over defined time intervals) for 99.9% inactivation of the tested fungal strains ranged from 48.99 mg min/L to 194.7 mg min/L for free chlorine and from 90.33 mg min/L to 531.3 mg min/L for monochloramine. Fungal isolates from a drinking water system (Aspergillus versicolor and Penicillium purpurogenum) were more disinfection resistant than Aspergillus fumigatus type and clinical isolates. The required 99.9% inactivation Ct values for the tested fungal strains are higher than E. coli, a commonly monitored indicator bacteria, and within a similar range for bacteria commonly identified within water distribution systems, such as Mycobacterium spp. and Legionella spp.
Wednesday, March 15, 2017
Our work highlighted on the local NPR station 'Tech Minute':
New commentary up at ES&T with Nathalia and Dr. Krista Wigginton from the University of Michigan.
In response to the 2014/15 Ebola virus disease (EVD) epidemic, both the World Health Organization and the United States Centers for Disease Control advised direct disposal of Ebola-contaminated liquid waste into sewage systems (wastewater collection and treatment systems) and latrines without disinfection.(1) This recommendation was made due to the presumed short survival of the enveloped Ebola virus in the environment, expected inactivation and dilution in wastewater systems, and the perceived hazards of additional waste handling and toxic byproduct formation due to chlorine addition. Subsequently, concern was raised regarding appropriate handling of Ebola virus contaminated liquid waste and the potential for secondary (environmental) transmission of the disease. Key unknowns that fueled this uncertainty included the environmental persistence of Ebola virus, efficacy of disinfection approaches against Ebola virus, and potential for exposure to Ebola virus within wastewater infrastructure. Ultimately, studies found that Ebola virus persisted longer than expected in the wastewater environment with an approximate T90 (time for 90% inactivation) of 2.1 days in sterilized wastewater.(2) While the most recent Ebola virus outbreak has ended, this experience has exposed a critical shortcoming in knowledge and regulation about appropriate handling of wastewater contaminated with highly infectious pathogens, such as Ebola virus, in both resource-rich and resource-poor outbreak settings.
Monday, March 6, 2017
New paper out -
Predominance and Metabolic Potential of Halanaerobium in Produced Water from Hydraulically Fractured Marcellus Shale Wells
Microbial activity in the produced water from hydraulically fractured oil and gas wells may potentially interfere with hydrocarbon production and cause damage to the well and surface infrastructure via corrosion, sulfide release, and fouling. In this study, we surveyed the microbial abundance and community structure of produced water sampled from 42 Marcellus Shale wells in southwestern Pennsylvania (well age ranged from 150 to 1846 days) to better understand the microbial diversity of produced water. We sequenced the V4 region of the 16S rRNA gene to assess taxonomy and utilized qPCR to evaluate the microbial abundance across all 42 produced water samples. Bacteria of the order Halanaerobiales were found to be the most abundant organisms in the majority of the produced water samples, emphasizing their previously suggested role in hydraulic fracturing related microbial activity. Statistical analyses identified correlations between well age and biocide formulation and the microbial community, in particular the relative abundance of Halanaerobiales. We further investigated the role of the order Halanaerobiales in produced water by reconstructing and annotating a Halanaerobium draft genome (named MDAL1), using shotgun metagenomic sequencing and metagenomic binning. The recovered draft genome was found to be closely related to the species H. congolense, an oil-field isolate, and Halanaerobium sp. T82-1, also recovered from hydraulic fracturing produced water. Reconstruction of metabolic pathways revealed Halanaerobium sp. MDAL1 to have the potential for acid production, thiosulfate reduction, and biofilm formation, suggesting it have the capability to contribute to corrosion, souring, and biofouling events in the hydraulic fracturing infrastructure.