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Jang, J.; Jang, J.; Barbato, M.; Gutierrez-Wing, M.T.; Rusch, K.A., and Jung, J., 2021. Effects of fluorogypsum and quicklime on unconfined compressive strength of Kaolinite. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 126–130. Coconut Creek (Florida), ISSN 0749-0208. Coastal areas have environmentally and economically important roles but tend have weak soft ground, which is often vulnerable by waves and unsuitable for coastal construction, such as ports and waterfront areas. Hence, this soft ground, which usually contains large amounts of clays, needs to be ameliorated by using appropriate soil improvement techniques. A common approach to improve soft ground is soil–binder injection techniques to enhance its strength. When avaialbe, binders from industrial wastes can be used instead of commercial products, such as cement and lime, to reduce construction costs and minimize environmental disturbance. Reusing industrial wastes mitigates environmental pollution and reduces the costs of waste management. Construction materials, such as sand and cement, can be partially replaced with industrial wastes if the wastes are granular and induce cementation effects. Fluorogypsum (FG), a by-product obtained during the production of hydrofluoric acid, satisfies these conditions, as it is capable of binding granular materials. Approximately 894,000 metric tons are annually produced in the U.S. However, data on the mechanical strength of clay–FG mixtures are unavailable. In this study, we conducted unconfined compressive strength tests to investigate the mechanical behavior of kaolinite, which represented clay in soft ground, at different FG and quicklime contents. The effects of FG on the compressive strength of kaolinite–FG–quicklime mixtures depend on the curing time and weight ratios of the constituent materials. The composition of the mixture with the highest compressive strength was 30% FG, 5% lime, and 65% kaolinite. We infer that the stoichiometric ratios of mixtures control the chemical reactions for the maximum compressive strength at different quicklime contents based on a series of compressive tests.

This paper investigates the mechanical properties under laboratory and field conditions of a concretelike blend made of fluorogypsum (FG), fly ash, and portland cement for artificial-reef construction, which is referred to as a FG-based blend. The 28-day compressive strength and relative volumetric expansion of the FG-based blend were statistically characterized. After 1 year of immersion in brackish water under field conditions, the compressive strength of the FG-based blend experienced a moderate reduction when compared with material under laboratory conditions but did not degrade below its 28-day value. Visual examination of the immersed specimens indicated that aquatic organisms are attracted to the proposed material. Field investigation of a small artificial-reef structure made of a FG-based blend indicated that sea floor settlement due to the weight of the structure was small. A preliminary cost analysis comparing the cost of artificial reefs constructed with different materials suggests that the proposed FG-based blend is a promising environment-friendly economic material for artificial-reef construction.

This paper develops a new low-cost construction material made of pH-adjusted fluorogypsum, class C fly ash, and type II Portland cement. The proposed fluorogypsum-based blend is durable in water and has a lower weight and lower cost than ordinary concrete. A preliminary investigation of strength and durability properties of this new construction material is also presented. A series of compressive strength tests and volumetric expansion measurements were conducted on specimens after 28 days of curing. The experimental results were used to develop response surface models. These models can be used to predict accurately compressive strength and volumetric expansion as functions of the relative content, in dry weight, of different components. The response surface models were employed to determine ranges of dry components of the system with sufficient strength and limited volumetric expansion. A composition with 62% pH-adjusted fluorogypsum, 35% fly ash, and 3% Portland cement was selected based on strength and volumetric expansion properties to conduct additional experimental studies to quantify its modulus of elasticity, Poisson’s ratio, setting times, density, void contents, and curing time effects on strength and volumetric expansion. The investigation results suggest that the proposed fluorogypsum-based blend is a promising low-cost concrete-like material for use in outdoor and underwater construction applications.

This paper reports a portable fluorescent sensor platform containing multiple excitation light illumination for quantification and differentiation of multiple analytes. The fluorescent sensor platform utilizes: (i) three different wavelengths of light emitting diodes (LEDs) for selectively stimulating target analytes; (ii) a sensitive photodetector for corresponding fluorescence measurements; (iii) a custom-built electronic system for data measurement and storage; and (iv) a compact three-dimensional printed housing for the developed sensor platform. Based on the fluorescent emission pattern obtained from each target analyte, multivariate analytical methods were applied to differentiate one analyte from the other in a mixture of multiple analytes. The fluorescent sensor platform was tested to selectively detect two target phytoplankton species: Chlorella vulgaris and Spirulina. Fluorescent emission of phytoplankton is caused by stimulation of photosynthetic pigments and is widely utilized to quantify and classify phytoplankton groups. Biomass estimation was therefore conducted by measuring chlorophyll a fluorescence emission for green algae (Chlorella vulgaris) using blue LED excitation and phycocyanin fluorescence emission for cyanobacteria (Spirulina) using amber LED excitation. The results demonstrated the viability of the developed device as a portable generic fluorescence sensor platform for simultaneously detecting various biochemical analytes.

Light effect on cultures of microalgae has been studied mainly on single species cultures. Cyanobacteria have photosynthetic pigments that can capture photons of wavelengths not available to chlorophylls. A native Louisiana microalgae (Chlorella vulgaris) and cyanobacteria (Leptolyngbya sp.) co‐culture was used to study the effects of light quality (blue–467 nm, green–522 nm, red–640 nm and white–narrow peak at 450 nm and a broad range with a peak at 550 nm) at two irradiance levels (80 and 400 μmol m(−2) s(−1)) on the growth, species composition, biomass productivity, lipid content and chlorophyll‐a production. The co‐culture shifted from a microalgae dominant culture to a cyanobacteria culture at 80 μmol m(−2) s(−1). The highest growth for the cyanobacteria was observed at 80 μmol μmol m(−2) s(−1) and for the microalgae at 400 μmol m(−2) s(−1). Red light at 400 μmol m(−2) s(−1) had the highest growth rate (0.41 d(−1)), biomass (913 mg L(−1)) and biomass productivity (95 mg L(−1) d(−1)). Lipid content was similar between all light colors. Green light had the highest chlorophyll‐a content (1649 μg/L). These results can be used to control the species composition of mixed cultures while maintaining their productivity.

Coastal wetlands and estuaries are impacted by nutrient loads from a variety of sources including infrequently occupied hunting and fishing camps. The marshland upwelling system (MUS) was designed to treat wastewater in the coastal environment where traditional septic systems or centralized wastewater collection and treatment are not viable. A laboratory macrocosm study was designed to simulate field conditions in which domestic wastewater is treated via injection into a marsh subsurface. Treatment of wastewater nitrogen (N) utilizing the MUS was examined under high (∼20 ppt) and low (∼2 ppt) salinity conditions. Two N wastewater solutions were used, one treatment consisted of 100 mg NH

The sulfate release from solidified/stabilized fluorogypsum was measured to develop the effective diffusion coefficients (De) as a parameter to assess the dissolution potential in aquatic a...

This chapter discusses one possible operational mode for the holding system design. The description of the bench scale automated system includes designs for the holding system and algae chemostat, the overall system operation, and the computer control/monitoring. The clam tank and trays were designed in accordance with the federal shellfish depuration guidelines. Proper water quality maintenance was accomplished using a pressurized upflow sand filter to entrap suspended solids and provide high nitrification capabilities at low substrate levels Design criteria for the filter followed those established for soft crawfish recirculating systems. The sump provides water quality buffering capacity, collects the water draining from the holding tank, receives the excess overflow from algae input, and provides a water source for the main system pump. The algae chemostat to support feeding in the Rangia clam recirculating holding system was sized based on algae growth kinetics and Rangia clam consumption studies.

Graphical abstractDisplay Omitted A simple fluorescent sensor was developed using light emitting diodes (LEDs), a photodetector, and optical filters.Microalgae concentration was successfully measured utilizing fluorescence of chlorophyll a in microalgal cells.Consistent and reliable fluorescent detection was demonstrated even with turbid sample solutions. This work reports the development of a portable and low cost fluorescent sensing system with a disposable microfluidic chip for on-site detection of a microalgal sample and its concentration. The sensor system has multiple light emitting diodes (LEDs) for excitation and a photodetector for measuring a fluorescent signal from a microalgal sample. The concentration of a microalgal sample is determined by measuring the fluorescent signal emitted by chlorophyll a. A dichroic filter and a color filter are also added to allow only the fluorescent signal from chlorophyll a to pass through the photodetector. The microfluidic chip consists of a glass slide and a PDMS channel with a vacuum pump, which collects a small volume of the microalgal sample (

This paper presents a new modeling system for nowcasting and forecasting enterococci levels in coastal recreation waters at any time during the day. The modeling system consists of (1) an artificial neural network (ANN) model for predicting the enterococci level at sunrise time, (2) a clear-sky solar radiation and turbidity correction to the ANN model, (3) remote sensing algorithms for turbidity, and (4) nowcasting/forecasting data. The first three components are also unique features of the new modeling system. While the component (1) is useful to beach monitoring programs requiring enterococci levels in early morning, the component (2) in combination with the component (1) makes it possible to predict the bacterial level in beach waters at any time during the day if the data from the components (3) and (4) are available. Therefore, predictions from the component (2) are of primary interest to beachgoers. The modeling system was developed using three years of swimming season data and validated using additional four years of independent data. Testing results showed that (1) the sunrise-time model correctly reproduced 82.63% of the advisories issued in seven years with a false positive rate of 2.65% and a false negative rate of 14.72%, and (2) the new modeling system was capable of predicting the temporal variability in enterococci levels in beach waters, ranging from hourly changes to daily cycles. The results demonstrate the efficacy of the new modeling system in predicting enterococci levels in coastal beach waters. Applications of the modeling system will improve the management of recreational beaches and protection of public health.

This paper presents a portable fluorescent sensing system that utilizes different light emitting diode (LED) excitation lights for multiple target detection. In order to identify different analytes, three different wavelengths (385 nm, 448 nm, and 590 nm) of excitation light emitting diodes were used to selectively stimulate the target analytes. A highly sensitive silicon photomultiplier (SiPM) was used to detect corresponding fluorescent signals from each analyte. Based on the unique fluorescent response of each analyte, it is possible to simultaneously differentiate one analyte from the other in a mixture of target analytes. A portable system was designed and fabricated consisting of a display module, battery, data storage card, and sample loading tray into a compact 3D-printed jig. The portable sensor system was demonstrated for quantification and differentiation of microalgae (Chlorella vulgaris) and cyanobacteria (Spirulina) by measuring fluorescent responses of chlorophyll a in microalgae and phycocyanin in cyanobacteria. Obtained results suggest that the developed portable sensor system could be used as a generic fluorescence sensor platform for on-site detection of multiple analytes of interest.

This study presents and compares two models for predicting fecal coliform levels at Gulf Coast beaches in Louisiana, USA. One was developed using the artificial neural network (ANN) in MATLAB toolbox and the other one was developed based on the multiple linear regression method (MLR). A total of six independent environmental variables, including rainfall, tide, wind, salinity, temperature, and weather type along with eight different combinations of the independent variables are capable of explaining about 76 % of variation in fecal coliform levels for model training data and 44 % for independent data. The findings are obtained from the ANN model and the MLR model using six years of bacteriological and environmental monitoring data. The results show that the ANN model performs consistently better than the MLR model. Applications of the ANN model can significantly reduce potential health risks of fecal pollution to beachgoers. The paper provides new insights into environmental processes responsible for the variation in levels of fecal coliform bacteria in coastal beach waters as well.

A model of the denitrification on a polyhydroxyalkanoate (PHA) based reactor for recirculating aquaculture was developed. PHA is a family of non-water soluble bioplastics produced by bacteria. The PHA formulation used in this work was polyhydroxybutyrate (PHB). The model considered nitrate concentration, dissolved oxygen, organic carbon and biomass concentration as the most significant variables. The developed model represents adequately the nitrate reduction with the medium used, for nitrate under 100 ppm NO 3 − -N. In the conditions tested, an average ratio of 2.92 g PHA to 1 g NO 3 − -N reduced was found. The model results showed a denitrification rate of 2.97 kg m −3 d −1 for ranges from 10 to 50 mg NO 3 − -N L −1 . Using this model as a management tool, the required size of denitrification units and PHA recharging time can be predicted based on the expected nitrate loading and the time between PHA recharges desired. The unit sizing should be done for the maximum load expected. The slow rate and the energy required for PHA hydrolysis, make it unavailable as electron donor after the nitrate is consumed, so it will not promote the formation of sulfides. The model can be modified for other biodegradable non-water soluble medium by changing the hydrolysis constant, which must be determined experimentally.

Current culture methods based on monocultures under phototrophic regimes are prone to contamination, predation, and collapse. Native cultures of multiple species are adapted to the local conditions and are more robust against contamination and predation. Growth, lipid and biomass productivity of a Louisiana native coculture of microalgae (Chlorella vulgaris) and cyanobacteria (Leptolyngbya sp.) in heterotrophic and mixotrophic regimes were investigated. Dextrose and sodium acetate at C:N ratios of 15:1 and 30:1 under heterotrophic (dark) and mixotrophic (400 μmol m−2 s−1) regimes were compared with autotrophic controls. The carbon source and C:N ratio impacted growth and biomass productivity. Mixotrophic cultures with sodium acetate (C:N 15:1) resulted in the highest mean biomass productivity (156 g m−3 d−1) and neutral lipid productivity (24.07 g m−3 d−1). The maximum net specific growth rate (U) was higher (0.97 d−1) in mixotrophic cultures with dextrose (C:N 15:1) but could not be sustained resulting in lower total biomass than in mixotrophic cultures with acetate (C:N 15:1), with a U of 0.67 d−1. The ability of the Louisiana coculture to use organic carbon for biomass and lipid production makes it a viable feedstock for biofuels and bioproducts.

The presence of bulk water and the resistant cell walls significantly limit the efficiency of lipid extraction from microalgal biomass paste. Current methods to rupture the cell walls (i.e. grinding after freeze-drying, osmotic shock, sonication) are energy intensive and time consuming. Due to their high surface energy concentration and high surface to volume ratio, silver nanoparticles can enhanced the cell wall rupture to increase the extraction efficiency of cell components. In this study, silver nanofibers were added as enhancers for the Folch’s extraction method and microwave assisted extraction of lipids from wet biomass paste (water content of 80.9%). Nanofibers concentrations of 0–1000 μg g−1 were tested. Two solvent:biomass ratios were tested in the Folch’s extraction method. Two temperatures (70 and 90 °C) and three treatment times (2, 5 and 10 min) were compared in the microwave assisted extraction. The results showed that the extraction efficiency increased with increased concentration of the nanofibers in the range tested. At concentrations of 1000 μg g−1 silver nanofibers (w/w based on the solvent and biomass solution) the efficiency of lipid extraction increased by ∼30% and 50% for the Folch’s and microwave assisted lipid extraction respectively. Treatment with AgNO3 in the same concentration as the nanofibers did not improve the extraction compared with no silver or nanofibers addition. The extraction method affected the lipid fatty acids profile. The Folch’s extraction with no silver nanofibers resulted in proportionally higher short chain saturated fatty acids, but lower lipid extraction. The microwave assisted lipid extraction provides the best results considering fatty acid profile, treatment time, solvent use and lipid extraction efficiency.

Recent interest in the use of microalgae for the production of biofuels and bioproducts has stimulated an interest in methods to enhance the growth rate of microalgae. This review examines past work involving the stimulation of Chlorella sp. growth and metabolite production by plant growth substances as well as by mixed cultures of Chlorella sp. with bacteria. Plant growth substances known to regulate Chlorella sp. growth and metabolite production include auxins, cytokinins, abscisic acid, polyamines, brassinosteroids, jasmonic acid, salicylic acid, and combinations of two or three of the aforementioned substances. Mixed cultures of bacteria are examined, including both natural bacteria–algae consortia and artificially induced symbioses. For natural consortia, commonly occurring bacterial species, including the genera Brevundimonas and Sphingomonas, are discussed. For artificially induced symbioses, the use of the nitrogen-fixing bacterium Azospirillum is examined in detail. In particular, a variety of studies have involved the coimmobilization of Chlorella sp. with Azospirillum sp. in alginate beads, with the goal of using the mixed culture to treat wastewater. In summary, the use of plant growth substances and mixed cultures provides two methods to increase the growth of Chlorella sp., whether for the production of lipids for biofuels, the production of bioproducts, the treatment of wastewater, or a variety of other reasons.

Enterococci concentrations in seawater samples collected in 2010 at a Gulf Coast beach in the afternoon were significantly lower (12 MPN/100 mL) compared with morning samples (172 MPN/100 mL). The factors affecting temporal differences of enterococci concentration in beach waters were studied through five laboratory experiments analyzing beach sands, solar radiation, salinity, and turbidity. Enterococci were found in beach sands at a geometric mean of 43 MPN per 100 g of sand, demonstrated the ability to persist for extended periods of time, and increased when incubated (geometric mean of 54 MPN per 100 g sand). Solar radiation inactivated large enterococci concentrations (≥24,196 MPN/100 mL) in as little as four hours in salinities ranging from 0 to 25 parts per thousand (ppt). Increased turbidity (70 and 140 NTU) hindered the effect of solar radiation, suggesting that near-shore turbidity may promote higher enterococci concentrations. The results indicate that enterococci replenishment alo...

The effect of salinity, dissolved oxygen and NO3-N concentration on the denitrification of recirculating aquaculture water using polyhydroxybutyrate (PHB) was evaluated. Four PHB media with different molecular weights and configurations were tested. The results show that at higher nitrate concentrations in the influent water, the consumed PHB:NO3-N ratio decreased. An average of 2.9 g of PHB:1 g NO3-N removed at temperatures of 20.8 ± 1.1 °C was measured. Although the molecular weight showed an apparent correlation with the denitrification rates, the correlation was not statistically significant. A moderately biofouled granular media displays a heterogeneity of microenvironments that allow some denitrification to occur in the presence of bulk dissolved oxygen levels approaching 5 mg L−1. As a practical approach, the inhibitory effects of oxygen can be mitigated either by design of the denitrification media bed and/or by control or reduction of the influent dissolved oxygen levels. The high plastic consumption needed for oxygen removal indicates that the second approach is more cost efficient. At a flux of 60 m3 m−2 d−1 the denitrification rate decreases at a constant rate in the first 30 cm of the PHB bed. Below this depth, the denitrification rate decreases very slowly and stays above 1 kg-NO3-N m−3 d−1. In a pragmatic sense, denitrification abilities can be expected to be similar in all salinities. Volumetric nitrate removal rates in the order of 2.5 kg-NO3-N m−3 media d−1 should be broadly obtained in fresh and marine water systems. In the range of up to 250 mg NO3-N L−1, the PHB can be used as a base for a passive denitrification unit that requires little management. The availability of an economic source of PHB such as production waste and the development of the bioplastic industry is determinant for the adoption of this material as a carbon source for denitrification processes.

A locally isolated co-culture of two photosynthetic species [Chlorella vulgaris (Chlorophyta) and Leptolyngbya sp. (Cyanobacteria)] displayed enhanced growth when compared to a Chlorella monoculture; however, the biological mechanisms driving such improvement are currently not well understood. To investigate these mechanisms, this study examined the differential gene expression in the Chlorella between the co-culture and the monoculture. Suppression subtractive hybridization was performed between mRNA from Chlorella in the co-culture and in a monoculture, and 105 genes were identified as being putatively differentially expressed. Nine of these genes, corresponding to the key functional categories of energy, metabolism, and protein synthesis, were further examined using quantitative real-time PCR and showed differential regulation of photosystem I and photosystem II and upregulation of stress-response genes and a gene encoding an oil-globule-associated gene in the co-culture Chlorella. This differential gene expression study of a Chlorella/cyanobacteria co-culture will aid in the development of culture strategies capable of taking advantage of these differences for the production of biomass and bioproducts of interest. Knowledge of the underlying genetic causes of the changes in growth and productivity of the species in co-culture provides insights on possible target genes for optimization of the culture.

Aims: To design a primer set enabling the identification through PCR of high-quality DNA for routine and high-throughput genomic screening of a diverse range of cyanobacteria. Methods and Results: A codon-equivalent multiple alignment of the phycocyanin alpha-subunit coding sequence (cpcA) of 22 cyanobacteria was generated and analysed to produce a single degeneracy primer set with virtually uniform product size. Also, an 18S ribosomal RNA detection set is proposed for rejecting false positives. The primer sets were tested against five diverse cyanobacteria, Chlorella vulgaris, Saccharomyces cerevisiae, and Escherichia coli. All five cyanobacteria showed positive amplification of cpcA product with homogeneous fragment length, and no products were observed for any other organism. Additionally, the only product formation observed for the 18S rRNA set was in C. vulgaris and S. cerevisiae. Conclusions: The newly proposed primer set served as effective check primers for cyanobacteria. Cyanobacteria gDNA had a positive, homogenous result, while other bacteria, eukaryotes and alga tested were negative. Significance and Impact of the Study: These novel, broad-spectrum primers will greatly increase the utility of PCR on newly discovered cyanobacterial species.

The marshland upwelling system (MUS) utilizes the natural properties of wetland soils to treat domestic wastewater injected into the marsh subsurface as the wastewater moves upwards and outwards from the injection site. The system is different from coarse media based wetland treatment systems common in Europe, though it relies on the same principles. A laboratory study was designed to simulate field conditions in order to investigate and quantify the removal of nitrogen from the wastewater by pumping wastewater into the bottom of cores and observing the changes as the wastewater moved upward to the surface. Two nitrogen treatments (100 mg NH(4)-N L(-1) and 80 mg NH(4)-N L(-1)/20 mg NO(3)-N L(-1)) and two salinities (2 and 20‰) for each N treatment were studied. Dissolved organic carbon (DOC) demonstrated a removal efficiency of 90%, while NO(3)-N had a removal efficiency of > 99% throughout the 84 days of the study. Higher salinity had a temporary, significant lower removal of DOC, while nitrate removal was high and consistent over time. Microbial biomass C (MBC) and denitrification enzyme activity (DEA) were measured to determine the role of microbial processes within the MUS. Wastewater introduction increased microbial growth at the column surface, which led to increases in denitrification/nitrification coupling and net N loss, as estimated by DEA. Salinity and organic matter were found to have significant negative and positive impacts, respectively, on DEA rates and MBC. An understanding of the impacts of salinity on specific microbially-mediated N transformations is critical for improving the efficiency of the MUS in coastal environments to determine the long-term sustainability.

The US EPA BEACH Act requires beach managers to issue swimming advisories when water quality standards are exceeded. While a number of methods/models have been proposed to meet the BEACH Act requirement, no systematic comparisons of different methods against the same data series are available in terms of relative performance of existing methods. This study presents and compares three models for nowcasting and forecasting enterococci levels at Gulf Coast beaches in Louisiana, USA. One was developed using the artificial neural network (ANN) in MATLAB Toolbox and the other two were based on the US EPA Virtual Beach (VB) Program. A total of 944 sets of environmental and bacteriological data were utilized. The data were collected and analyzed weekly during the swimming season (May-October) at six sites of the Holly Beach by Louisiana Beach Monitoring Program in the six year period of May 2005-October 2010. The ANN model includes 15 readily available environmental variables such as salinity, water temperature, wind speed and direction, tide level and type, weather type, and various combinations of antecedent rainfalls. The ANN model was trained, validated, and tested using 308, 103, and 103 data sets (collected in 2007, 2008, and 2009) with an average linear correlation coefficient (LCC) of 0.857 and a Root Mean Square Error (RMSE) of 0.336. The two VB models, including a linear transformation-based model and a nonlinear transformation-based model, were constructed using the same data sets. The linear VB model with 6 input variables achieved an LCC of 0.230 and an RMSE of 1.302 while the nonlinear VB model with 5 input variables produced an LCC of 0.337 and an RMSE of 1.205. In order to assess the predictive performance of the ANN and VB models, hindcasting was conducted using a total of 430 sets of independent environmental and bacteriological data collected at six Holly Beach sites in 2005, 2006, and 2010. The hindcasting results show that the ANN model is capable of predicting enterococci levels at the Holly Beach sites with an adjusted RMSE of 0.803 and LCC of 0.320 while the adjusted RMSE and LCC values are 1.815 and 0.354 for the linear VB model and 1.961 and 0.521 for the nonlinear VB model. The results indicate that the ANN model with 15 parameters performs better than the VB models with 6 or 5 parameters in terms of RMSE while VB models perform better than the ANN model in terms of LCC. The predictive models (especially the ANN and the nonlinear VB models) developed in this study in combination with readily available real-time environmental and weather forecast data can be utilized to nowcast and forecast beach water quality, greatly reducing the potential risk of contaminated beach waters to human health and improving beach management. While the models were developed specifically for the Holly Beach, Louisiana, the methods used in this paper are generally applicable to other coastal beaches.

Microalgal biomass produced in indoor photobioreactors can be used as inoculum for large-scale outdoor cultures or directly for the production of high-value bioproducts due to the higher control of these cultures compared with outdoor systems. One of the main costs of indoor microalgal cultures is the illumination. This work can be used as a basis for the optimization of the light source for indoor microalgal biomass production, based on the light source type, irradiance, productivity, growth rate, attenuation coefficients, and contaminant growth on the reactor's side-walls. Four commercially available near 400-W artificial light sources for microalgal cultures (metal halide (MH), high-pressure sodium (HPS), Son Agro®, and fluorescent) were compared. The light elevation and the surface scalar irradiance were shown to have a linear relationship. The attenuation coefficient in air (ka) was highest with Son Agro®. A linear partition of the attenuation coefficient between the water and biomass and an exponential relationship between average scalar irradiance and depth were found. An empirical overall scalar attenuation coefficient for each light source was obtained. The lowest maximum observed growth rate was obtained with fluorescent light (0.98 d−1) and the highest with Son Agro® (2.39 d−1). The highest growth on the reactor's wall was obtained with Son Agro®. Further studies resulted in a higher maximum specific growth rate and optimum irradiance for HPS (2.37 d−1 and 460 μmol s−1 m−2) compared with those observed with MH (1.73 d−1 and 391 μmol s−1 m−2).

Aerobic biodegradation of polyhydroxybutyrate (PHB) was investigated. Mass loss experiments were performed to determine degradation kinetics. Tributyl citrate was blended with some test samples to determine the impact of a natural plasticizer on biodegradation. Effects of biodegradation in the physical, chemical, thermal, and mechanical properties of the materials tested were determined. Plates of different thicknesses (0.24, 1.2, 3.5, and 5.0 mm) were degraded to determine the effect of initial mass:initial surface area ratio on degradation rates. The mass:initial surface area is proportional to the plate thickness. PHB biodegradation rates obtained are dependent on the mass:surface area ratio. Temperature affects the relation of degradation rate to initial mass:initial surface area. PHB in plates up to a thickness of 3.5 mm can degrade completely in compost. Plates with an initial mass:initial surface area ratio of

Anaerobic biodegradation in sewage sludge of polyhydroxybutyrate (PHB) was investigated. Evolved gaseous carbon was measured to assess biodegradability according to ASTM D5210. Mass-loss experiments were performed to determine degradation kinetics. Changes in the polymer properties were investigated. The impact of a natural plasticizer [tributyl citrate (TBC)] on biodegradation was determined. Polylactic acid was also biodegraded for comparison. Melt-pressed plates of PHB (with thicknesses of 0.24, 0.5, 1.2, 3.5, and 5.0 mm) were biodegraded to investigate the relationship between initial mass:initial surface area ratios and decay rates. Scanning electron microscopy micrographs of degraded specimens were recorded for visual illustration of the degradation process. A relationship between initial mass:initial surface area and degradation rates indicates that the thickness and surface area of the material affect its degradation. The degradation rates were impacted by the sewage sludge activity. TBC additive hindered PHB's rate of degradation. Thermal properties, molecular bonding, and molecular weight measured by differential scanning calorimetry, Fourier transform infrared, and size exclusion chromatography, respectively, were only slightly affected by biodegradation, indicating that recycling PHB will not affect its performance.

The marshland upwelling system (MUS) was developed as an onsite wastewater treatment approach for coastal dwellings. The MUS removes fecal bacteria in injected wastewater by utilizing the processes of filtration, straining, adsorption, predation, and die-off through saturated subsurface sediments. The objective of this research was to evaluate the long-term sustainability of the MUS by evaluating removal efficiency of fecal bacteria from raw wastewater and assessing the system background recovery after the MUS stopped operation. Based on 32-month monitoring on an MUS site located in Bayou Segnette Canal Waterway, Louisiana, we found that the MUS compared well with other constructed wetland systems. The MUS showed an enhanced efficacy of fecal bacteria removal after long-time operation due to the deposition of solid particles from primary wastewater and the growth of biofilm in subsurface over time. Moreover, the background recovery study indicates that the subsurface environment has recovered com...

This research investigated the sorption and transport of MS-2 in saturated sand under a wide range of salinities using one-dimensional column experiments. The salinity varied from 0 ppt (fresh water) to 30 ppt. The MS-2 in the fresh water showed very weak adsorption due to having the same negative charge as the sand. Increasing the salinity concentrations dramatically enhanced MS-2 adsorption. The MS-2 breakthrough revealed the existence of reversible and irreversible sorption sites in the sand. Salinity increased MS-2 attachment by compressing the double layers of MS-2 and reversible sorption sites. The salinity also changed some reversible sorption sites into irreversible sorption sites by reversing to positive surface charges of silica powder. An advection-dispersion-sorption model with a two-site reversible-irreversible kinetic sorption was developed to describe MS-2 breakthrough under different salinity conditions. The sorption parameters were estimated and their independence was evaluated by minimizing the total squared error of the MS-2 data. The proposed model showed good agreement with the experimental data for a wide range of salinity levels from fresh water to near seawater. The strong sorption shown in the MS-2 breakthrough at high salinity levels above 8 ppt was able to distinguish the proposed model from other sorption models. This study promotes the understanding of the viral sorption with salinity and provides a useful model for coastal management of viral migration in saline coastal groundwater.

An estimated 28% of the production cost in HISTAR systems that are artificially illuminated is attributed to the lighting cost. This cost estimated is based on an operational configuration comprised of eight CFSTRs, a system dilution rate ( D s ) of 0.640 d −1 , and 400 W metal halide lamps positioned at an elevation of 38.1 cm over the culture. Deterministic model simulations of the volumetric productivity ( P v ), photosynthetic efficiency ( E o ) and lighting cost (LC) under various management strategies, operational parameters and reactor design configurations were performed and compared to the simulation results obtained for the original configuration. The simulations showed that LC may be reduced by 35.5% by switching from a metal halide (MH) to high-pressure sodium (HPS) light source at an optimum system dilution rate D s = 0.641 d −1 . LC may be reduced by an additional 17.8% through decreasing the lamp elevation to 25.4 cm. Increasing the wattage of the light source from 400 to 1000 W in the last six reactors would reduce the LC by 13% from the original cost. Overall, using HPS lamps at 25.4 cm height, with six 1000 W and two 400 W lamps at a D s = 0.641 d −1 will result in a 54% overall LC reduction compared to the original configuration of HISTAR. This represents a 13% reduction in the overall microalgal production cost for HISTAR.

A continuous microwave system to treat ballast water inoculated with Artemia salina cysts as a model invasive spore was tested for its efficacy in inactivating the cysts present. The system was tested at two different flow rates (1 and 2 L x min(-1)) and two different power levels (2.5 and 4.5 kW). Temperature profiles indicate that the system could deliver heating loads in excess of 100 degrees C in a uniform and near-instantaneous manner when using a heat recovery system. Except for a power and flow rate combination of 2.5 kW and 2 L x min(-1), complete inactivation of the cysts was observed at all combinations at holding times below 100 s. The microwave treatment was better or equal to the control treatment in inactivating the cysts. Use of heat exchangers increased the power conversion efficiency and the overall efficiency of the treatment system. Cost economics analysis indicates that in the present form of development microwave treatment costs are higher than the existing ballast water treatment methods. Overall, tests results indicated that microwave treatment of ballast water is a promising method that can be used in conjunction with other methods to form an efficient treatment system that can prevent introduction of potentially invasive spore forming species in non-native waters.

A continuous microwave system to treat ballast water inoculated with different invasive species was designed and installed atthe Louisiana State University Agricultural Center. The effectiveness of the system to deliver the required heating loads to inactivate the organisms present was studied. The targeted organisms were microalgae (Nannochloropsis oculata), zooplankton at two different growth stages (newly hatched brine shrimp-Artemia nauplii and adult Artemia), and oyster larvae (Crassosstrea virginica). The system was tested at two different flow rates (1 and 2 liters per min) and power levels (2.5 and 4.5 kW). Temperature profiles indicate that, depending on the species present and the growth stage, the maximum temperature increase will vary from 11.8 to 64.9 degrees C. The continuous microwave heating system delivered uniform and near-instantaneous heating at the outlet proving its effectiveness. The power absorbed and power efficiency varied for the species present. More than 80% power utilization efficiency was obtained at all flow rate and microwave power combinations for microalgae, Artemia nauplii and adults. Test results indicated that microwave treatment can be an effective tool for ballast water treatment, and current high treatment costs notwithstanding, this technique can be added as supplemental technology to the palette of existing treatment methods.

The marshland upwelling system (MUS) is an alternative onsite wastewater treatment system developed for coastal communities. The phosphorus treatment efficiency of the MUS operated under high background salinity conditions (∼32 ppt) was examined over the course of a one-year field study. Five individual studies were investigated by intermittently injecting wastewater at a depth of 3.8 m using flow rates/injection frequency regimes of 1.9 L∕min (30 min∕3 h) , 5.5 L∕min (30 min∕3 h) , 2.8 L∕min (30 min∕3 h) , and 2.8 L∕min (15 min∕h) . There were two studies conducted within the 2.8 L∕min (30 min∕3 h) flow regime: (1) with normal influent and (2) with high strength synthetic wastewater. Over the course of the study, no signs of phosphorus saturation were observed. The overall system efficiency for the entire study was estimated to be >98% . Removal rate coefficients ranged from 0.73– 1.25 m−1 and 0.66– 1.08 m−1 for total phosphorus and orthophosphate, respectively. Upon completion of the final 2.8 L∕min (15...

The biological rhythms of microalgal growth within a hydraulically integrated serial turbidostat algal reactor (HISTAR) were examined after comparison of a simple mechanistic productivity model with actual data yielded a standard error of prediction (SEP) of 62%. The data used for this study were taken on cultures of Selenastrum capricornutum grown under continuous 400-watt metal halide lighting. Fourier series analysis (up to five harmonics) was used to model the biorhythms and differentiate them from stochastic processes. Regression analyses revealed that the best Fourier series fit for the data was a three harmonic summation. Regression analyses on additional harmonic summations did not increase r2 by more than 1%. The three harmonics were summed and incorporated into the growth term of the simple model, and the resultant full model was calibrated. The mechanistic HISTAR productivity model was greatly enhanced by the addition of the biological rhythm component, resulting in a SEP of

The marshland upwelling system (MUS) was developed as a treatment alternative for wastewater derived from coastal communities. This research assessed the treatment efficiency of the MUS for removing both total phosphorus and ortho -phosphate from domestic wastewater under low ( −1 were obtained for the 0.9 (15 min/h), 1.9 L/min (15 min/h) and 1.9 L/min (30 min/h) studies, respectively. Treatment efficiency was >99% for all three studies, with predicted travel distances ranging from 4.63 to 6.41 m to reach a target effluent of 0.1 mg-P/L. Predicted, required travel distances increased during the study as phosphorus saturation developed. The MUS system is unique in that it does not have fixed boundaries. Subsequently, wastewater can move past the zones of saturation to sediments that have active adsorption sites, thus providing increased capacity and treatment efficiency.

A deterministic model was developed to predict microalgal productivity within the Hydraulically Integrated Serial Turbidostat Algal Reactor (HISTAR). HISTAR consists of two turbidostats, which concomitantly inoculate the first of a series of CFSTRs. The CFSTRs function as a biomass amplifier of the inoculated culture. The model included an analysis of the internal light dynamics within each CFSTR and the effect of the instantaneous average irradiance ( I a n (PAR)) on the instantaneous growth rate ( μ n ) within CFSTR n . The latter effect was accomplished using Steele's equation. The instantaneous average irradiance was determined by integrating the Lambert–Beer Law over the depth of the culture within the CFSTRs. Fourier series analysis was used to model the biorhythms of the microalgae. The model was calibrated for biomass using four data sets collected at system dilution rates ( D s ) of 0.265 day −1 , 0.385 day −1 , 0.641 day −1 and 1.127 day −1 . The ability of the calibrated model to simulate daily volumetric productivity ( P v ) within HISTAR was determined through calculation of the percent standard error of prediction. The overall mean for the four data sets was 24.8%. The average predicted productivity for the data sets was 24.2 g m −3 day −1 (16.2 g m −2 day −1 ) and the average actual productivity of the data sets were 25.5 g m −3 day −1 (19.9 g m −2 day −1 ), resulting in only a 5.1% error. Simulations produced by the calibrated model were used to estimate the optimum D s (between 0.641 day −1 and 0.884 day −1 ). The model predicted a P v of 70.2 g m −3 day −1 ( P a = 46.8 g m −2 day −1 ) at optimum D s . The maximum P a observed in the model simulations was 39.9 g m −2 day −1 .

Ballast water presents an important vector for introduction of aquatic invasive species in the coastal waters around the world. Currently there are no established technologies proven to completely eliminate this problem due to the particularities of the ballasting and de-ballasting operations (extremely large volumes of water, efficiency at destroying macro and micro organisms, environmental issues associated with chemical treatments). Continuous microwave heating presents a potential solution to this problem, but the design of suitable applicators depends on the dielectric properties of the ballast water to be processed. The study presented in this paper is focused on the dielectric properties (dielectric constant--epsilon'; dielectric loss--epsilon") of synthetic ballast water inoculated with four organisms at seven different temperatures in the frequency range of 300 to 3000 MHz. The dielectric properties of the mixtures were determined using a network analyzer and a dielectric probe kit using the open-ended coaxial probe method. Numerical analysis was performed on data collected across all frequencies involved with an emphasis placed on F.C.C. allotted frequencies of 433, 915 and 2450 MHz. The dielectric constant was relatively independent of frequency and the organism used, but it showed a remarkable decrease with temperature. The dielectric loss showed an extreme decrease with increasing frequency, marked differences between the different organisms and between different growth stages of the same organism, and a large relatively linear increase with increasing temperature.

The effectiveness of the marshland upwelling system (MUS) installed in a low-background salinity area was investigated for the removal of fecal bacteria from domestic wastewater. It was hypothesized that travel distance required to meet the treatment objectives would be greater under low-salinity conditions. A suite of three injection regime (flow rate/frequency; 18.9 L/min-15 min/h; 0.95 L/min-15 min/h; and 1.9 L/min-15 min/h) studies was performed over a 1.25-year period to investigate the impact of injection flow rate on the removal of fecal coliforms and Escherichia coli from domestic wastewater injected into the MUS system. Each injection regime resulted in removal efficiencies greater than 99.9% for fecal coliforms and E. coli. The 18.9 L/min study (10 times design flow rate) tested the upper hydraulic loading limit of the system and resulted in eventual system channelization. First-order removal rate constants were estimated as 2.5–2.6 and 1.5–1.7 m–1 for the 0.95 and 1.9 L/min studies, respectivel...

Malfunctioning or nonexistent wastewater treatment systems are one of the primary causes of water quality degradation in coastal areas. The marshland upwelling system (MUS) was developed as a low-cost, low-maintenance on-site treatment alternative for coastal dwellings, in which wastewater is injected into the saline subsoil and pushed toward the surface by buoyancy forces. Four injection regimes, characterized by flow rate (L/min), duration (min), and frequency (h), were evaluated for a MUS located in Moss Point, Mississippi, from June 2001 to June 2002 to determine the system's ability to remove nitrogen from wastewaters generated from recreational facilities. Nitrogen data were collected from a cluster of monitoring wells surrounding the injection well. The injection regime of 2.8 L/min (30 min/3 h) resulted in the best removal efficiency. Total kjeldahl nitrogen (TKN) and total ammonia nitrogen (TAN) were reduced from an influent average of 168 and 160 to 2.4 and 1.5 mg-N/L, respectively. Vector distance-based removal coefficients were estimated to be 0.88 and 0.84 m −1 for TKN and TAN, respectively. Subsequently, 3.2 and 3.1 vector meters were required to reduce TKN and TAN to 10 mg-N/L. The probabilities of the system effluent to exceed 10 mg-N/L were estimated to be 3% for TKN and 0% for TAN, respectively. Bench-scale laboratory studies indicated the potential for further treatment in the upper zone of the MUS system due to increases in redox potential caused by the Juncus roemerianus ’ rhizosphere , which provided a nitrification zone.

There is a need for greater understanding of the light dynamics in photoautotrophic microalgal reactors as commercialization efforts move forward. This paper presents results of experiments performed to determine (1) surface irradiance ( I os (PAR)) as a function of lamp elevation; (2) depth ( z ) and biomass ( X ) dependent scalar irradiance ( I z (PAR)) and attenuation k 0 (PAR); (3) average scalar irradiance ( I a (PAR)) in the reactor as a function of biomass; and (4) specific growth rate as a function of I a (PAR) and impacted by photoinhibition for the hydraulically integrated serial turbidostat algal reactor (HISTAR) illuminated by metal halide lamps. Selenastrum capricornutum was used as the test organism. Lamp elevation studies resulted in a light energy dissipation coefficient ( k a ) of 7.46 μmol s −1 m −2 cm −1 . Light attenuation studies yielded a linear partition of the attenuation coefficient between the water and biomass; k 0 (PAR) = 1.97 + 0.0575 X and an exponential relationship between I a (PAR) and X ; I a456 = 277 e −0.0118 X . Finally, net the specific growth rate was found to follow Steele's model for determination, resulting in a μ max = 1.73 d −1 and I opt (PAR) = 391 μmol s −1 m −2 .

The marshland upwelling system (MUS) was installed on private camps in the Grand Bay National Estuarine Research Reserve, Moss Point, Mississippi. The system was evaluated for its effectiveness in removing fecal coliforms from settled, raw wastewater. A suite of studies was performed at flow rates of 1.9, 2.8, and 5.5 L/min and an injection frequency of 30 min every 3 h to investigate fecal coliform removal. An additional study was performed at a flow rate of 2.8 L/min and an injection frequency of 15 min every hour. Overall, the MUS consistently maintained fecal concentrations below effluent regulatory standards for shellfish harvesting waters (14 most probable number of colonies per 100 mL). Mean influent concentrations of 55,269±2,218,016 colony forming units (CFU)/100 mL were reduced to effluent counts of 2.7±14.07 CFU/100 mL (observed in the 1.5 m wells). Three- to four-log reductions in influent counts were observed over the initial 1.4 vector m from the injection well. The overall removal followed a first-order decay relationship with respect to vector distance, resulting in removal rate constants ranging from 5.6 to 6.6/m and predicted surface concentrations approaching 0 CFU/100 mL. The 2.8 L/min for 30 min every 3 h treatment provided the best effluent quality.

Rhodamine water tracer (RWT) was used to characterize the migration of waste water within the saline subsurface of a marshland upwelling system (MUS), which is an alternative on-site waste water treatment system for coastal areas. Field tracer studies were performed to investigate the fresh waste water plume movement within the saline ground water. Pore velocities were calculated using first detection times and ranged from 0.68 to 10.7 x 10(-4) cm/sec for the loamy sandy soil matrix present at the site. Use of RWT in the field also allowed determination of main and preferential flowpaths. One- and two-dimensional laboratory experiments were performed using silica sand to investigate the interactions of the organically rich waste water with RWT within the zone surrounding the point of injection (one-dimensional) and the impact of background salinity on plume movement (two-dimensional). The results from these studies were used to help explain the field data. One-dimensional breakthrough curves revealed retardation factors for the RWT in the waste water mixture of 1.73 to 1.90. These results were similar to other researchers, indicating little interaction between the waste water and RWT. Variations in pore water salinity (5, 15, 25, and 35 ppt) were found to have a significant effect on pore water velocities of the fresh water plume (two-dimensional), indicating the need to incorporate background salinities into the design process for MUS.

City Park Lake is a shallow, subtropical, urban hypereutrophic lake located in Baton Rouge, Louisiana. By the late 1970s, this artificial lake had experienced extreme eutrophication and suffered from frequent algal blooms and fish kills. Restoration of City Park Lake in 1983 consisted of dredging nutrient-laden sediments and rehabilitating sewage pipelines. Nearly one decade following restoration, filamentous algae became a recurring nuisance. A simplified phosphorus management model was developed to aid local officials in decision-making processes pertaining to the management of the lake and its watershed. The calibrated model was used to evaluate several management strategies for the reduction of in-lake phosphorus levels. The management of sediment phosphorus levels combined with reduced watershed phosphorus concentrations is viewed as the most viable option for the long-term health of the lake.

A hydraulically integrated serial turbidostat algal reactor (HISTAR) for the mass production of microalgae was designed, constructed and preliminarily evaluated. The 9266-l experimental system consists of two enclosed turbidostats hydraulically linked to a series of six open continuous-flow, stirred-tank reactors (CFSTRs). The system was monitored and controlled using GENESIS process control software. A production study was preformed using Isochrysis sp. (C-iso) to assess system stability and production potential under commercial-like conditions. The study was performed at the following target system parameters: system dilution rate of 0.49 per day, pH 7.6, nitrogen=10 mg l −1 , phosphorus=2 mg l −1 , and artificial illumination (photosynthetic photon flux density) from 1000 W metal halide lamps=800 μmol s −1 m −2 . At steady state conditions, daily harvested algal paste was 1454 g (wet), mean areal system productivity=47.8±3.04 g m −2 per day (17.1±1.09 g C m −2 per day) and mean CFSTR6 density=105.5±6.71 mg l −1 .

The construction of mixture designs and the methods of response surface analysis of mixture data are discussed and applied for determining the optimum ingredients for stabilized phosphogypsum (PG) composites conducive to marine application. Of particular importance is the ability of the composites to maintain physical integrity when submerged. Therefore, potential indicators for the survivability of the stabilized PG composites were also screened. The triangular coordinate system was used to present the three ingredient components of the PG composites as well as their dependent variables. The augmented simplex centroid design with pseudocomponents was used in determining mixture ingredient composition. A quadratic model with two process variables was used to analyze the experimental results and predict the optimum ingredient composition. The model predicts that a series of PG: class C fly ash:portland type II cement ingredients, such as 62%:35%:3% PG:class C fly ash:portland type II cement and 65%:31%:4% ...

This study examined the effects of storage time on the fatty acid composition of freshwater Selenastrum capricornutum algal paste under 4 C refrigeration, the fatty acid composition of rotifers fed the fresh and stored algal paste, and the toxicological properties of the algal paste. Microalgae were produced in a hydraulically integrated serial turbidostat algal reactor (HIS-TAR), harvested as a paste, refrigerated and analyzed every 2 wk. Fresh Selenastrum capricornutum paste had almost three times greater concentration of unsaturated fatty acids than saturated fatty acids. Over 50% of the unsaturated fatty acids were made up of n-3 and n-6 fatty acids. Total unsaturated, n-3 group and n-6 group fatty acids decreased (P 0.05) during storage, including the nutritionally important fatty acids (C20:4n6, C20:5n3, C22: 6n3). Rotifers fed 2– and 4-wk-old algal paste had a significantly lower (P 0.05) total unsaturated fatty acid percentage and significantly greater (P 0.05) total saturated fatty acids than those fed fresh algae. There were no significant changes in the n-6 group fatty acid level in the 4-wk-old paste feeding study or for the n-3 or n-6 groups in the 2-wk-old paste feeding study as compared to fresh algae. The levels of the three nutritionally important fatty acids (C20:4n6, C20:5n3, C22:6n3) did not differ between rotifers fed fresh and stored algae. Stored algae did not present toxicity to rotifers and Daphnia at the normal feeding concentration. These results indicated that the use of refrigerated freshwater algal paste for production of rotifers results in live feed with adequate nutritional properties for marine larviculture. This could eliminate the costs associated with production of marine algae, which could be replaced with freshwater algae, and may provide an alternative to cryopreservation.

City Park Lake is a shallow urban hypereutrophic lake located in Baton Rouge, Louisiana, with a surface area of 0.23 km2 and a mean depth of 1.2 m. By the late 1970s, the lake had become highly eutrophic and suffered from frequent and severe algal blooms and fish kills. A major restoration effort was undertaken in 1983 that consisted of dredging and the repair of sewage infrastructure. Immediate improvements in water quality were observed following restoration; algal blooms and fish kills were virtually eliminated for nearly a decade. However, large floating mats of filamentous algae periodically occurred during the early 1990s. Results of a water quality sampling program conducted in 2000 and 2001 indicated that phosphorus has once again reached pre-restoration levels, and nitrogen levels have decreased well below those observed during pre-restoration years. Whereas phosphorus-limited conditions predominated in the years preceding the 1983 restoration, results of the 2000–2001 sampling program indicate that the lake has become nitrogen-limited with respect to photosynthetic activity. This trend in nutrient levels has likely influenced the recent predominance of filamentous over unicellular species of algae observed during the last decade. Nearly 4 years of drought-like conditions beginning in 1998 have resulted in an overall increase in the hydraulic retention time of the lake. This condition has resulted in organic staining of the lake waters, or the development of a tea-like color due to the decomposition of organic compounds. This phenomenon has played a major role in inhibiting the sunlight available for filamentous algal growth since 1998 and the absence of filamentous algae during the 2000–2001 sampling program.

The Marshland Upwelling System (MUS), a decentralized wastewater treatment strategy for coastal dwellings, was examined to assess its ability to remove Escherichia coli from raw sewage as a step towards total treatment. Wastewater was intermittently injected down a 4.6-m injection well into the surrounding salt marsh at 0.9, 1.9, and 3.8 lpm over the 13-month evaluation period. Optimal E. coli removal and hydraulic performance was achieved at the 1.9-lpm flow rate with influent concentrations of 260,000±370,000 E. coli/100 mL reduced to a mean effluent count of 0.4±10.6 E. coli/100 mL. Escherichia coli concentrations declined exponentially with only 0.9-m travel distance needed to reduce influent concentrations by 1 order of magnitude. Predicted surface concentrations were less than 1 E. coli/100 mL. The probability of effluent counts exceeding the U.S. Environmental Protection Agency standard of 126 E. coli/100 mL for recreational waters was 5.5×10-12%. Increasing flows to 3.8 lpm initiated localized hyd...