David K. Stevens

A sensor network for high frequency estimation of water quality constituent fluxes using surrogates

Characterizing spatial and temporal variability in the fluxes and stores of water and water borne constituents is important in understanding the mechanisms and flow paths that carry constituents to a stream and through a watershed. High frequency data collected at multiple sites can be used to more effectively quantify spatial and temporal variability in water quality constituent fluxes than through the use of low frequency water quality grab sampling. However, for many constituents (e.g., sediment and phosphorus) in-situ sensor technology does not currently exist for making high frequency measurements of constituent concentrations. In this paper we describe how water quality measures such as turbidity or specific conductance, which can be measured in-situ with high frequency, can be used as surrogates for other water quality constituents that cannot economically be measured with high frequency to provide continuous time series of water quality constituent concentrations and fluxes. We describe the observing infrastructure required to make high frequency estimates of water quality constituent fluxes based on surrogate data at multiple sites within a sensor network supporting an environmental observatory. This includes the supporting sensor, communication, data management, and data storage and processing infrastructure. We then provide a case study implementation in the Little Bear River watershed of northern Utah, USA, where a wireless sensor network has been developed for estimating total phosphorus and total suspended solids fluxes using turbidity as a surrogate.

Pentachlorophenol and crystal violet degradation in water and soils using heme and hydrogen peroxide

An abiotic method for oxidative PCP degradation in soil under unsaturated conditions and neutral pH was developed. Reagents used were heme (a catalyst) and peroxide (an oxidant). The aqueous phase degradation of crystal violet and PCP, and the mineralization of PCP in soil were determined. Five factors were investigated to assess their impact on PCP degradation in a soil contaminated with wood preserving chemicals. The results showed that heme and peroxide could efficiently degrade PCP and crystal violet in a short period of time in either liquid or unsaturated soil systems. In soil, three control runs showed little degradation of PCP, but treatments with heme and peroxide showed a maximum of 13% mineralization of PCP. Heme and peroxide concentration were the two most important factors in improving degradation of PCP in soil.

A modeling approach for assessing the effect of multiple alpine lakes in sequence on nutrient transport

The effects of a single lake on downstream water chemistry may be compounded by the presence of additional lakes within the watershed, augmenting or negating the effects of the first lake. Multiple, linked lakes are a common feature of many watersheds and these resemble reactors in series often studied in engineering. The effects of multiple lakes in series on nutrient transport are largely unexplored. We populated and calibrated a simple lake model to investigate the role of a sub-alpine lake (Bull Trout Lake (BTL), Rocky Mountains, USA) on the transport of the macronutrients during the summer of 2008. Further, we developed a sequential model in which four identical lakes (copies of the BTL model) were connected in series. All lakes in the sequence retarded the flux of nutrients, thus slowing their transport downstream. The first lake in the sequence dramatically altered stream water chemistry and served as a sink for C and P and a source of N, while additional lakes downstream became sources of C, N and P. Although additional downstream lakes resulted in important changes to water chemistry and nutrient transport, the nature of the changes were similar from Lakes 2 to 4 and the magnitude of the changes diminished with distance downstream. Our lake model served as an effective tool for assessing the nutrient budget of the lake and the hypothetical effect of multiple lakes in sequence in a landscape limnology framework.

A pioneer project of wastewater reuse in China

Abstract A wastewater reclamation project involving a pilot-plant study and further design and construction of a full scale advanced wastewater treatment plant is presented in this paper. A wastewater with a flow of 8000–10,000 m 3 /d comprising 40% industrial wastewater from a machinery factory and 60% domestic wastewater from residential area with a population of about 50,000 people is treated, and 50% of the treated effluent is directly reused for washing, boiler supply, air pollution control, cooling, washroom flushing, landscape irrigation, and construction. The severe shortage of water in this area and the pollution caused to the river leading to the Zhangze Reservoir necessitated this project. The pilot-plant study was conducted to provide sound technical information for the final construction of a full-scale advanced wastewater treatment plant. The wastewater treatment plant [with a capital cost of 3.92 million yuans (1 yuan = 0.27 U.S.

Quantification of pentachlorophenol transformation product distribution in the presence of Phanerochaete chrysosporium

)] which employs a two-stage attached growth biological treatment process followed by sand filtration and disinfection has been put into operation successfully. The planned removal efficiencies of COD, turbidity, and total coliforms are achieved by this plant. Economic efficiency analysis conducted shows that the net gain of the project is 248,000 yuans annually.

The influence of spatially variable stream hydraulics on reach scale transient storage modeling

Experiments were carried out to quantify the mineralization and distribution of pentachlorophenol (PCP) by the white rot fungus Phanerochaete chrysosporium, and distribution of its transformation products into water-soluble, solvent-soluble, sorbed, and volatile fractions in liquid cultures. Water-soluble and solvent-soluble products from 14C-PCP transformation were first measured under oxygen limited conditions. Results indicated that after 12 days, 15% of 14C was recovered in methylene chloride, and less than 1% was water soluble. Sorption to the fungal mat reached a maximum of 16% 14C after 9 days incubation and declined to 5% at day 12. However, recovery of 14C within the system was only 30% at day 12. To improve the mass balance of the system, polyurethane foam was placed inside the culture flask to trap volatile products of PCP transformation. Results showed that after 12 days incubation of 14C-PCP with the fungus, 82% of the 14C added was volatilized. GC/MS analysis demonstrated that pentachloroanisole (PCA) was the only volatile product of PCP transformation. Sorption of 14C to the fungal mat was reversible to some extent. Chemical mass balance results in this experiment were near 100%. In the final experiment, the polyurethane volatile trap was placed outside the culture flask to assess the impact of the continuous removal of volatiles from the flask head space on mineralization. Increased 14CO2 production was observed when the polyurethane volatile trap was placed outside the culture flask compared with placement inside the flask.

Development of an Advanced Evaporation System with Fouling-Free Technology Using a Circulating Fluidized Bed Heat Exchanger

Within the context of reach scale transient storage modeling, there is limited understanding of how best to establish reach segment lengths that represent the effects of spatially variable hydraulic and geomorphic channel properties. In this paper, we progress this understanding through the use of channel property distributions derived from high-resolution imagery that are fundamental for hydraulic routing. We vary the resolution of reach segments used in the model representation and investigate the minimum number necessary to capture spatially variable influences on downstream predictions of solute residence time probability density functions while sufficiently representing the observed channel property distributions. We also test if the corresponding statistical moments of the predictions provide comparable results and, therefore, a method for establishing appropriate reach segment lengths. We find that the predictions and the moment estimates begin to represent the majority of the variability at reach segment lengths coinciding with distances where observed channel properties are spatially correlated. With this approach, reach scales where the channel properties no longer significantly change predictions can be established, which provides a foundation for more focused transient storage modeling efforts.

Decision support model for hazardous waste application rates at land treatment systems

The heat transfer rate and fouling characteristics of a circulating fluidized bed heat exchanger (CFBHE), and the treatability of landfill and municipal incinerator disposal pit leachate by advanced evaporation were investigated experimentally. The heat exchanger used glass beads (3.0-mm diameter with a specific gravity of 2.54) to control fouling. Glass beads enhanced heat transfer coefficients independently of water velocity within a superficial velocity range from 0.4–0.8 m/s. Fouling control tests using a 3,000-mg/L ferric oxide slurry revealed that the glass beads effectively removed deposits formed prior to introduction of the beads and enhanced the heat transfer coefficient. The beads also prevented the formation of deposits. Leachate from an industrial landfill in Yeochun, Korea, containing petroleum and chemical waste was treated using the CFBHE system. Treatment efficiency for CODCr, BOD5, and NH4+-N were 91, 91, and 50%, respectively at an influent pH of 7.0. Treatment of leachate from a second...

EPRI’S WATERSHED ANALYSIS RISK MANAGEMENT FRAMEWORK (WARMF) VS. USEPA’S BETTER ASSESSMENT SCIENCE INTEGRATING POINT AND NONPOINT SOURCES (BASINS)

Abstract A mathematical model is described which provides a rational approach for obtaining, organizing and evaluating the specific information needed for the determination of hazardous waste application on land treatment systems. The model is divided into five modules. These modules represent the principal mechanisms which are assumed to govern the fate of an organic hazardous material in the vadose zone. They are the following: loading conditions, degradation, advective transport, dispersive transport and sorption/desorption. The numerical algorithm for advective transport is described in some detail using a soil-water system as an example. The model is demonstrated for selected aro-matics found in a refinery waste sludge. Application of the model provides a methodology for predicting the behavior of hazardous constituents in soil systems and ranking chemicals according to their need to be controlled.

How to Utilize Relevance Vectors to Collect Required Data for Modeling Water Quality Constituents and Fine Sediment in Natural Systems: Case Study on Mud Lake, Idaho

There are numerous water quality modeling packages available from industry and government that assist in watershed decision-making and total maximum daily load (TMDL) development. Uncertainty exists among decision makers concerning the appropriateness of these tools and modeling packages to specific TMDL issues. Tennessee Valley Authority (TVA), in collaboration with Utah State University and the Electric Power Research Institute (EPRI), has undertaken a comparison of Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) and Watershed Analysis Risk Management Framework (WARMF). BASINS, developed by the USEPA, and WARMF, developed by EPRI, are watershed management decision support systems that integrate data, geographic information systems (GIS), and models. Although similar in their description, there are important differences in model setup requirements, technical expertise requirements, overall modeling approaches, and the application of model results to watershed decision making and TMDL development. The portion of this study presented in this paper compares the requirements, strengths, and weaknesses of WARMF with BASINS for general watershed management and TMDL activities. Specifically, guidance is provided on DSS selection by providing information on the capabilities of each system, human resource requirements, and the approximate costs associated with model setup and calibration. Overall, it was found that each system has strengths and weaknesses and that choosing one system over another is dependent on many factors, including in-house modeling expertise, constituents to be modeled, the number of watershed modeling efforts required, and available funds.