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The irradiance and light spectral distribution affect the growth and productivity of microalgal cultures. In extensive open pond cultures, the light control has limited options, mainly the culture depth. In photobioreactors, besides the culture depth, the light source, configuration of the reactor, light pathway, and flow rate can be used to control the characteristics of the light available to the cultures. The change of light conditions can also be used to modify the composition of the microalgal biomass produced to optimize the production of bioproducts of interest. Additionally, in mixed cultures, the species composition can be influenced by the light quantity and quality. Determining the effect of the light quantity and quality in photosynthetic cultures will help to develop strategies to optimize the production of biomass, lipids, pigments, proteins, and other compounds of interest in photosynthetic microorganisms. Information obtained from bench scale cultures can rarely be applied directly to large-scale bioreactors. Nonetheless, determining the kinetic parameters of microalgal cultures at bench scale will reduce the time needed to optimize the cultures in photobioreactors. In this work, a review of the main factors is presented, along with specific examples of the effect of light quality and quantity in cultures with single and multiple species. Additionally, some models to predict the effect of light on microalgal productivity are discussed. [ABSTRACT FROM AUTHOR]

Abstract: 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 2.9g of PHB:1g 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 5mgL−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 60m3 m−2 d−1 the denitrification rate decreases at a constant rate in the first 30cm of the PHB bed. Below this depth, the denitrification rate decreases very slowly and stays above 1kg-NO3-Nm−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 2.5kg-NO3-Nm−3 mediad−1 should be broadly obtained in fresh and marine water systems. In the range of up to 250mg NO3-NL−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. [Copyright &y& Elsevier]

Abstract: Factors such as limitations in water quality and quantity, cost of land, limitations on water discharges, environmental impacts and diseases, are driving the aquaculture industry toward more intensive practices. This will force producers to adopt environmentally friendlier technologies. Recirculating systems, with a biofilter as the most prominent characteristic, treat internally the water contaminated with dissolved organics and ammonia and reduce the amount of water use and discharge from aquaculture operations. This paper reviews the implications of the changing use of recirculating aquaculture systems (RAS) on biofiltration research for freshwater and marine operations. Demand for cost effective biofilters will increase with the expansion of recirculating systems, both as a complement and replacement of traditional ponds. For freshwater aquaculture, emphasis should be placed in cost competitiveness, low head operations, intensification of ponds with RAS biofiltration and the evaluation of suspended growth systems. In the marine systems, an increase in demand of oligotrophic and ultraoligotrophic systems is expected, particularly in the nursery systems. Sizing and cost efficiency of biofilters for nursery operations should be addressed. Problems in marine biofilter acclimation appear to justify the development of new acclimation procedures. Biosecurity concerns, land cost and storm threats will drive nursery systems inland, where saltwater supply and disposal will force an increased water reuse. Denitrification strategies will need to be redefined and optimized for the marine nursery environment. [Copyright &y& Elsevier]

This study evaluated the properties of sugarcane bagasse ash (SCBA) obtained from different production processes for use as partial replacement of cement: (1) minimally post-processed (MP) SCBA, obtained by sieving and grinding SCBA from Louisiana's sugarcane field production; (2) fully post-processed (FP) SCBA, obtained by sieving, further burning under controlled conditions at temperature T, and grinding field-produced SCBA, denoted as FP-T; and (3) laboratory-produced (LP) SCBA, obtained by controlled burning at temperature T of bagasse fibers and grinding of the obtained ashes, denoted as LP-T. The temperatures of burning, T, for FP-T and LP-T SCBA were varied between 450 and 650 °C at 50 °C intervals. The significance of this study is the valorization of agricultural waste for the production of low-carbon concrete for transportation applications in Louisiana, and other locations where SCBA are produced from a low-efficiency boiler in a sugar mill. A comprehensive characterization of the different SCBA materials was conducted, including scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), laser diffraction particle size analysis, Chapelle's test, strength activity index (SAI), loss on ignition (LOI), and moisture content. Experimental results showed that all LP-T and FP-T SCBAs met ASTM C618 chemical requirements and SAI requirements for Class N pozzolans. By contrast, MP SCBA did not meet these requirements, thus resulting in unsuitable SCM application. LP calcinated at 650 °C and FP calcinated at 450 °C exhibited the greatest SAI and SiO2 + Al2O3 + Fe2O3 among LP-T and FP-T SCBAs, respectively. Based on a combination of properties and production practicality considerations, FP calcinated at 450 °C was identified as the most promising SCM-grade SCBA for large-scale production in Louisiana, and was used to further evaluate the fresh and hardened properties of concrete incorporating SCBA at 10%, 20%, 30%, and 40% cement replacement by mass. A decrease in workability as well as 28- and 90-day compressive strength with the increase in SCBA content was observed. However, the relative strength gain from 28 to 90 days and the 90-day surface resistivity increased with increments in SCBA dosage. Characterization of cement-SCBA paste through XRD and SEM revealed portlandite consumption and densification of the cementitious matrix from 28 to 90 days, thus suggesting the pozzolanic activity of SCBA. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study investigates the mechanical and durability properties of blends made of fluorogypsum (FG) with the pH adjusted by using controlled amounts of circulating fluidized bed combustion ash (CFBCA) and denoted as C-FG, class C fly ash (FA), and type II Portland cement (PC). A series of pH tests was conducted on samples of C-FG to develop an analytical relationship between acidity and CFBCA content, which can be used to determine the optimal amount of CFBCA needed to obtain a specified pH value. Two compositions of C-FG-based blends were investigated in detail to identify the effects of CFBCA content on compressive strength, modulus of elasticity, Poisson’s ratio, relative volumetric expansion, unit weight, and setting times. The obtained properties were compared with those of FG-based blends having the same composition and made using FG with the pH adjusted by using uncontrolled amounts of CFBCA (U-FG). Results suggest that the amount of CFBCA can have significant effects on the properties of C-FG-based blends, depending on the composition. In addition, C-FG-based blends generally achieve a higher compressive strength and initial stiffness than the corresponding U-FG-based blends. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Tin(iv) sulfide (SnS2), as a mid-band-gap semiconductor shows good potential as an excellent photocatalyst due to its low cost, wide light spectrum response and environment-friendly nature. However, to meet the demands of large-scale water treatment, a SnS2 photocatalyst with a red-shifted band gap, increased surface area and accelerated molecule and ion diffusion is required. Doping is a facile method to manipulate the optical and chemical properties of semiconductor materials simultaneously. In this work, SnS2 photocatalysts with varied Ag doping content are synthesized through a facile one-step hydrothermal method. The product is characterized by XRD, SEM, TEM and UV-Vis spectrometry. The photocatalytic activity of the as-prepared Sn1−xAgxS2 is studied by the degradation of methylene blue (MB) dye under solar light irradiation. It is found that increasing the Ag dopant concentration can effectively increase the solar light adsorption efficiency of the photocatalyst and accelerate heterogeneous photocatalysis. The optimal concentration of Ag dopant is found to be 5% with the highest rate constant being 1.8251 hour−1. This study demonstrates that an optimal amount of Ag doping can effectively increase the photocatalytic performance of SnS2 and will promote the commercialization of such photocatalysts in the photocatalytic degradation of organic compounds. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]