Marylynn V. Yates

Modeling microbial fate in the subsurface environment

As groundwater is relied upon more and more as a source of drinking water, the practice of recharging groundwater with treated wastewater has become a more attractive means of replenishing depleted groundwater reserves. However, even extensively treated wastewater may contain pathogenic microorganisms, particularly enteric viruses. Once in the soil, these microorganisms, especially the viruses, are capable of migrating considerable distances to reach groundwater, where they pose a potential health hazard to persons consuming the water. Over one half of the waterborne disease outbreaks in the U.S. are due to the use of contaminated groundwater, and microorganisms are the cause of illness in the majority of these outbreaks. Several models have been developed to predict the behavior of microorganisms in the subsurface environment. These models range from conventional, theoretical models of contaminant transport to empirically based models using laboratory and field data. The ultimate goal of the models is to...

Metabolism of chlorinated methanes, ethanes, and ethylenes by a mixed bacterial culture growing on methane

SummarySoil was taken from the top 10 cm of a soil column that removed halogenated aliphatic hydrocarbons in the presence of natural gas. This soil was used as an enrichment inoculum to determine that the removals seen in the soil column were in fact of a microbiological nature. Methane served as the source of carbon and energy and was consumed immediately by the enrichments. After several transfers of the enrichments, a stable consortium of at least three bacterial types was obtained. The predominant bacterium was a non-motile, gram-negative coccus. This stable consortium was able to remove chlorinated methanes, ethanes, and ethylenes when grown with methane and oxygen in the headspace. Methane was required for the removals to be observed. Acetylene inhibited the removals, which further suggests the involvement of methanotrophs. Benzene and toluene were removed by the mixed culture with or without methane in the headspace. Fatty acid analysis of the mixed culture resulted in a profile that indicated that the predominant organism was a type II methanotroph. This study provides further evidence that methanotrophic bacteria are capable of cometabolizing a wide range of chlorinated methanes, ethanes, and ethylenes.

Occurrence of rotaviruses and enteroviruses in recreational waters of Oak Creek, Arizona

Abstract Recent epidemiological studies have shown a relationship between swimming in recreational waters meeting bacteriological standards and gastroenteritis with a suggested viral etiology. No previous studies have been conducted in the United States on the occurrence of human pathogenic enteric viruses in freshwater recreational areas. The presence of enteroviruses and rotaviruses was investigated in Oak Creek, Arizona, a heavily used recreational area. Water samples were filtered through positively charged filters (168–1555 I.), eluted with beef extract, and assayed for human enteroviruses and rotaviruses. Eighteen of the 41 recreational water samples were positive for enterovirus or rotavirus. Of these, nine samples exceeded the Arizona State recommended limit of 1 PFU 40 l −1 for full body contact in effluent dominated recreational waters. Several virus positive samples met the recommended fecal coliform standards (200 CFU 100 ml −1 ) for recreational waters indicating the inadequacy of bacterial standards for monitoring viral water quality. The isolation of the pathogenic enteric viruses (i.e., poliovirus 1, echovirus 1, coxsackievirus B1 and B6 and rotavirus) from this popular recreational water demonstrates the potential for transmission of viral disease.

A comparison of geostatistical methods for estimating virus inactivation rates in ground water

Abstract Enteric viruses are responsible for a large number of ground-waterborne disease outbreaks every year. Septic tanks are the most frequently cited causes of ground-water contamination in disease outbreaks, and are probably the major contributors of viruses to the subsurface environment. Controlling the placement of septic tanks such that all viruses would be non-infective by the time the effluent reached drinking water wells would likely reduce the number of waterborne viral disease outbreaks. This study describes the use of and provides a comparison of different geostatistical techniques (kriging, cokriging, and combined kriging and regression) to estimate virus inactivation rates in ground water. These estimates were used with the regional ground-water flow characteristics to estimate septic tank setback distances over a city-wide area. It was found that combined kriging and regression, which eliminates the need for laboratory values of virus inactivation rates by using the linear regression relationship between temperature and inactivation rates, produced comparable results to the other two methods, yet reduced the cost of the analysis considerably.

A modified purge-and-trap/gas chromatography method for analysis of volatile halocarbons in microbiological degradation studies

Abstract A modification of a purge-and-trap unit is described for use in microbiological studies concerning degradation of aliphatic halogenated hydrocarbons (halocarbons). Sealed serum tubes containing bacteria, aqueous medium, headspace, and volatile halocarbons are used as purge vessels to monitor the disappearance of the halocarbons. Data are presented to show the loss of volatile halocarbons that occurred when these systems were analyzed by standard purge-and-trap. An application of this method is shown with methane-utilizing bacteria. The modified purge-and-trap method resulted in a total measurement of halocarbons in the sample without making a transfer to a separate purge vessel.