Soluble polyacrylate (PA), a polydisperse mixture of polyacrylate polymers, is strongly adsorbed and biodegradable. Biotic fate studies were carried out with once-through columns containing sand colonized with anaerobic biomass previously grown in a methanogenic fluidized bed. A fraction of soluble PA having a weight-average molecular weight of 16,700 and a range of molecular weight from 10(3) to 10(5) was biologically removed and mineralized to CO2. Due to its polydisperse nature, the breakthrough curve had a gradual increase to an apparent steady-state removal of approximately 60% near one day when the liquid detention time was 21 minutes. Modeling successfully explained the observed breakthrough result when the fraction was divided into components having a wide range of retardation factors (R): about 25% was strongly adsorbed (R = 200 and 500), 45% was moderately adsorbed (R = 50 and 100), and 30% was weakly adsorbed (R = 1-10). In this study, in which active biomass already was present from utilization of a primary substrate (glucose here), equilibrium adsorption increased the time to breakthrough, which also reduced the exiting concentration by increasing the substrate contact time.
Sampling indoor air for potential vapor-intrusion impacts
In November 2007, indoor air at four residences was sampled to measure trichloroethene (TCE) concentrations over short-and long-duration intervals. A carefully designed investigation was conducted consisting of triplicate samplers for three different investigatory methods: dedicated 6-liter Summa canisters (US EPA Method TO-15), pump/sorbent tubes (US EPA Method TO-17), and passive diffusion samplers (MDHS 80). The first two methods collected samples simultaneously for a 24-hour period, and the third method collected samples for two weeks.Data collected using Methods and
is a registered civil engineer with approximately 17 years of experience in tbe fields of environmental engineering and water resources. He i s tbe founder a d president of Tri-S Environmenta6 Sensibti? Strategies and Solutions for tbe EnvironmenS Newport M i B E ingmundwaterhas been shown to travel over 1,000 feetdowngradient from its source in several comprehensive field studies conducted across North America. The biodegradability of M713E is examined by summarizing all the significant literature on the subject and by detailing thefindings of recent field investigations of MTltBE transport. I n Orange County, California, the persistence of MTBE is analyzed and statistical representations of source variability arepresented. Regionaland farfield transport of MTBE in groundwater sourced from undetground gasoline storage tanks are summarized in comprehensive tables of frequency and plume length. Btimates of source mass and duration allow for comparison of associated plume size. The conclusion reached after reviewing all the available literature on MTBE is that its biodegradability seems slight and the size of theplumes aresurprisingly lave. Intrinsic or natural attenuation remedies for M2BE merit close scrutiny.The issue of MTBE persistence in groundwater has been one of the most important topics of discussion in the remediation industry during the past year, MTBE biodegradability in groundwater is unclear and misunderstood due to the lack of applied research on the fundamental mechanisms of biodegradation. There are reports of an MTBE plume of over three miles in length (MacDonald, 1998) and due to its reported lack of any significant biodegradability, a significant regulatory problem indeed. The municipalities charged with public water supply sourced by groundwater are very concerned and the proposed action level for MTBE in groundwater is 35 pg/L (a possible carcinogen). Reported concentrations from groundwater monitoring wells of MTBE range from 10,000 to 50,000 pg/L on the high end (pure phase solubility approximately 51 million pg/L) are not uncommon. The petroleum industry is exploring alternatives and funding additional research.
REGIONAL MTBE GROUNDWATER OBSERVATIONSAs a general indication of the "scope" of the MTBE problem in groundwater, the results of a compilation of data from National Water Quality Assessment (NAWQA) are presented (data obtained from Squillace
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