Mark C. Meckes

Phylogenetic diversity of drinking water bacteria in a distribution system simulator.

Aims:  To characterize the composition of microbial populations in a distribution system simulator (DSS) by direct sequence analysis of 16S rDNA clone libraries.

Performance of PCR-Based Assays Targeting Bacteroidales Genetic Markers of Human Fecal Pollution in Sewage and Fecal Samples

There are numerous PCR-based assays available to characterize human fecal pollution in ambient waters. Each assay employs distinct oligonucleotides and many target different genes and microorganisms leading to potential variations in assay performance. Performance comparisons utilizing feces and raw sewage samples are needed to determine which assays are best suited for expensive and time-consuming field validation, fate, transport, and epidemiology studies. We report the assessment of five end-point PCR and 10 real-time quantitative PCR (qPCR) assays that target genes from presumptive Bacteroidales microorganisms reported to be associated with human feces. Each assay was tested against a reference collection of 54 primary influent sewage samples collected from different geographical locations across the United States and 174 fecal DNA extracts from 23 different animal sources. Experiments indicate that human-associated genetic markers are distributed across a broad range of human populations but show substantial differences in specificity for human feces suggesting that particular assays may be more suitable than others depending on the abundance of genetic marker required for detection and the animal sources impacting a particular watershed or beach of interest.

Population diversity in model potable water biofilms receiving chlorine or chloramine residual

Abstract Most water utilities use chlorine or chloramine to produce potable water. These disinfecting agents react with water to produce residual oxidants within a water distribution system (WDS) to control bacterial growth. While monochloramine is considered more stable than chlorine, little is known about the effect it has on WDS biofilms. Community structure of 10-week old WDS biofilms exposed to disinfectants was assessed after developing model biofilms from unamended distribution water. Four biofilm types were developed on polycarbonate slides within annular reactors while receiving chlorine, chloramine, or inactivated disinfectant residual. Eubacteria were identified through 16S rDNA sequence analysis. The model WDS biofilm exposed to chloramine mainly contained Mycobacterium and Dechloromonas sequences, while a variety of alpha- and additional beta-proteobacteria dominated the 16S rDNA clone libraries in the other three biofilms. Additionally, bacterial clones distantly related to Legionella were found in one of the biofilms receiving water with inactivated chlorine residual. The biofilm reactor receiving chloraminated water required increasing amounts of disinfectant after 2 weeks to maintain chlorine residual. In contrast, free chlorine residual remained steady in the reactor that received chlorinated water. The differences in bacterial populations of potable water biofilms suggest that disinfecting agents can influence biofilm development. These results also suggest that biofilm communities in distribution systems are capable of changing in response to disinfection practices.

Combining land use information and small stream sampling with PCR-based methods for better characterization of diffuse sources of human fecal pollution.

Diffuse sources of human fecal pollution allow for the direct discharge of waste into receiving waters with minimal or no treatment. Traditional culture-based methods are commonly used to characterize fecal pollution in ambient waters, however these methods do not discern between human and other animal sources of fecal pollution making it difficult to identify diffuse pollution sources. Human-associated quantitative real-time PCR (qPCR) methods in combination with low-order headwatershed sampling, precipitation information, and high-resolution geographic information system land use data can be useful for identifying diffuse source of human fecal pollution in receiving waters. To test this assertion, this study monitored nine headwatersheds over a two-year period potentially impacted by faulty septic systems and leaky sanitary sewer lines. Human fecal pollution was measured using three different human-associated qPCR methods and a positive significant correlation was seen between abundance of human-associated genetic markers and septic systems following wet weather events. In contrast, a negative correlation was observed with sanitary sewer line densities suggesting septic systems are the predominant diffuse source of human fecal pollution in the study area. These results demonstrate the advantages of combining water sampling, climate information, land-use computer-based modeling, and molecular biology disciplines to better characterize diffuse sources of human fecal pollution in environmental waters.

Quantitative microbial risk assessment of a drinking water – wastewater cross-connection simulation

Quantitative microbial risk assessment is a useful way to predict the incidence of infection and illness within a community following exposure to pathogens. We used this risk assessment technique t...

Solvent Extraction Processes: A Survey of Systems in the SITE Program

Solvent extraction of contaminated soils, sludges and sediments has been successfully completed at a number of Superfund sites. Each commercialized process uses a unique operating system to extract organic contaminants from solids. These operating systems may be classified by the properties of the solvents each utilizes: (1) standard solvents, (2) near-critical fluids/liquified gases, and (3) critical solution temperature solvents. Pretreatment and post-treatment requirements vary depending upon the operating systems of the solvent extraction system. Future demonstrations of these technologies by the U.S. EPA’s Superfund Innovative Technology Evaluation Program will provide additional information regarding the efficacy of these processes.

Site demonstration of Terra-Kleen response group's mobile solvent extraction process

The U.S. EPAs Superfund Innovative Technology Evaluation (SITE) Program evaluated a pilot-scale solvent extraction process developed by the Terra-Kleen Response Group (TKRG). This process uses a proprietary solvent, or mixture of solvents, to extract organic contaminants from solids. A pilot-scale evaluation was conducted at Naval Air Station North Island (NASNI), near San Diego, CA, on soils which were contaminated with polychlorinated biphenyls (PCBs) and other organic substances. Five tons of soil with an average PCB concentration of 144 mg/kg were excavated, homogenized, and equally distributed to five extraction vessels. Eleven extraction cycles were used to produce a treated soil with an average PCB concentration of 1.71 mg/kg on a dry weight basis (98.8% removed). Oil and Grease (O&G) removal efficiencies were found to be 65.9%. This low O&G removal efficiency was attributed to solvent/solute relationships. Initial concentrations of hexachlorodibenzofuran (HxCDF) in soils averaged 0.697 jig/kg. Following solvent extraction, no HxCDFs were detected (<0.117 fxg/kg) in soil samples. A fullscale solvent extraction system was operated at a site in Stockton, California. Pesticides were extracted from 500 tons of contaminated soil using 19 extractors, each 20 cubic yards in volume. Three extraction cycles produced solids with <0.093 mg/kg residual pesticide (>99% removed). These results demonstrate that the TKRGs solvent extraction process is effective in removing organic contaminants from soils.

SITE demonstration of the basic extractive sludge treatment process

The Superfund Innovative Technology Evaluation (SITE) Program, in cooperation with EPA Region 5, the Great Lakes National Program Office (GLNPO), and the U.S. Army Corps of Engineers (COE) planned and executed a pilot-scale evaluation of the Basic Extractive Sludge Treatment (B.E.S.T.®) process on sediment samples obtained from the Grand Calumet River in Gary, Indiana. Two separate sampling locations were selected based upon previous data. One location had sediments with total polychlorinated biphenyl (PCB) concentrations averaging 10 mg/kg, and total polynuclear aromatic hydrocarbon (PAH) concentrations averaging 520 mg/kg. The other location had sediments with average total PCB and PAH concentrations of 427 mg/kg and 72,000 mg/kg, respectively. The sediment samples were segregated by location, then screened, homogenized, and stored prior to treatment. A total of ten batches of sediments were treated (five for each sample location). Results showed that of the samples which had low original contaminants c...

Solvent extraction of polynuclear aromatic hydrocarbons and polychlorinated biphenyl from river sediments

River sediments contaminated with polynuclear aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were treated using Resources Conservation Companys Basic Extractive Sludge Treatment (B.E.S.T.) process. Results showed that, regardless of the initial contaminant concentration, >95 percent of the PAHs and >99 percent of the PCBs in the sediment could be extracted. Additionally, the effectiveness of triethylamine (TEA) as an extracting agent for specific PAHs and PCB congener classes was compared. Results show that TEA selectively extracted PAHs with high log octanol/water partition coefficients (>4.54), low water solubilities ( 178.2). PCB extraction efficiencies remained high regardless of congener class. These results indicate that specific physical characteristics of PAHs are good predictors of extraction efficiencies.

Emergency Response for Public Water Supplies after Hurricane Katrina

Hurricane Katrina resulted in damage and destruction to local water supplies in Mississippi and Louisiana affecting millions of people. Immediately following the devastation, a multidisciplinary team of 30 EPA emergency response, research, and water program personnel joined forces with local health and environmental officials to help residents with access to safe drinking water supplies from hurricane-ravaged parishes surrounding New Orleans, LA. The EPA team met at the EPA Region VI Emergency Response Center in Dallas, Texas to prepare for assessment of over 400 public water supplies. EPA employees loaded SUVs, vans, and trucks with emergency response supplies and drove 9 hours to Livingston, LA. The EPA team began working 12- to 14-hour days for 10 straight days to restore safe drinking water to Louisiana communities. Each EPA person was paired with an inspector from a State Rural Water Association (LA, TX, GA, IN, IA, and IL were represented), or with someone from LA Department of Health and Hospitals (LDHH). Major problems included; loss of power/loss of pressure, no backup generators (as many as 60 generators were requested), and damage/destruction to treatment plants and water distribution systems. Water systems were categorized on the basis of type of water company (community, non-community, or transient), severity of damage, need, whether they had been visited already by LDHH, and accessibility considering flooding and loss of infrastructure (electrical power and roads). After the landfall of Hurricane Rita, a second team of EPA Office of Research and Development microbiologists assisted EPA Region VI with analysis of bacteria samples from public water systems at a mobile laboratory near Lake Charles, Louisiana.