Monday, May 1, 2017

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 fumigatusAspergillus 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.

Research Needs for Wastewater Handling in Virus Outbreak Response

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.

Monday, January 16, 2017

New manuscript out in AEM led by collaborators at Penn State: 

Efficient low-pH iron removal by a microbial iron oxide mound ecosystem at Scalp Level Run

Acid mine drainage (AMD) is a major environmental problem affecting tens of thousands of km of waterways worldwide. Passive bioremediation of AMD relies on microbial communities to oxidize and remove iron from the system; however, iron-oxidation rates in AMD environments are highly variable across sites. At Scalp Level Run (Cambria County PA), first-order iron-oxidation rates are ten times faster than at other coal associated iron mounds in the Appalachians. We examined the bacterial community at Scalp Level Run to determine whether a unique community is responsible for the rapid iron oxidation rate. Despite strong geochemical gradients including an over 10-fold change in the concentration of ferrous iron from 57.3 mg/L at the emergence to 2.5 mg/L at the base of the coal tailings pile, the bacterial community composition was nearly constant with distance from the spring outflow. Scalp Level Run contains many of the same taxa present in other AMD sites, but the community is dominated by two strains of Ferrovum myxofaciens, a species that is associated with high rates of Fe(II) oxidation in laboratory studies.
Importance Acid mine drainage pollutes more than 19,300 km of rivers and streams and 72,000 ha of lakes worldwide (1). Remediation is frequently ineffective and costly, upwards of US$100 billion globally (2, 3, 4) and nearly US$5 billion in Pennsylvania alone (5). Microbial Fe(II) oxidation is more efficient than abiotic Fe(II) oxidation at low pH (6). Therefore, AMD bioremediation could harness microbial Fe(II) oxidation to fuel more cost-effective treatments. Advances will require a deeper understanding of the ecology of Fe(II)-oxidizing microbial communities and the factors that control their distribution and rates of Fe(II) oxidation. We investigated bacterial communities that inhabit an AMD site with rapid Fe(II) oxidation and found that they were dominated by two OTUs of Ferrovum myxofaciens, a taxon associated with high laboratory rates of iron-oxidation. This research represents a step forward in identifying taxa that can be used to enhance cost-effective AMD bioremediation.