Pond Liners Research Articles

Analysis of Farmers’ Perceptions on Sealing Techniques for Runoff Harvesting Ponds: A Case Study from Burkina Faso

Water conservation in arid and semi-arid regions faces significant challenges due to low and irregular rainfall, worsened by climate change, which negatively affects rain-fed crop productivity. Various techniques, including supplemental irrigation using runoff harvesting ponds, aim to address these issues but often suffer from water loss due to infiltration, influenced by the pond liner type. This study uses a factorial analysis to assess the farmers’ perceptions of four pond sealing techniques. Using the Waso-2 method, a survey conducted in 2022 among 41 rainwater harvesting pond owners across three regions of Burkina Faso revealed that farmers prioritized impermeability and ease of maintenance over cost and availability. Concrete, scoring 16/20, was the most preferred, chosen by over 75% of farmers for its durability and resistance to weathering, despite its high cost. Geomembrane, with a score of 12/20, was valued for its waterproofing properties but had durability concerns. Clay, although cheap and available, scored 8/20 due to poor waterproofing on unstable ground. Bitumen, the least favored with a score of 6/20, was hindered by scarcity and lack of familiarity. To enhance supplemental irrigation in Burkina Faso and similar regions, waterproof concrete or durable geomembrane liners are recommended. Further research into improving bitumen and clay liners is also suggested. These findings provide key insights into farmers’ preferences, offering guidance for developing effective water conservation strategies to boost agricultural productivity and address food security challenges in the context of climate change.

In vitro and in vivo evaluation of the efficacies of commercial probiotics and disinfectant against acute hepatopancreatic necrosis disease and luminescent vibriosis in Litopenaeus vannamei

The bioactivities of two commercially available probiotics and one chemical disinfectant were tested against strains of Vibrio parahaemolyticus (VPAHPND) and V. harveyi. This study aimed to determine shrimp pathogenic Vibrios' in vitro and in vivo sensitivities to commercial probiotics and a chemical disinfectant. The probiotics and disinfectant were tested first in vitro, followed by the in vivo trials. Results showed that upon administration of probiotics either through diet or adding into the tank water, the survivability of shrimp was increased during challenge with VPAHPND and V. harveyi. Also, the disinfectant was tested against the same pathogens and showed positive bactericidal effects at 2500 ppm and 5000 ppm. The present findings suggest that adding probiotics to the rearing water or the shrimp feeds effectively prevents infection by lowering the load of pathogenic bacteria. In comparison, the effectiveness of the disinfectant (PUR) depends on its appropriate concentration and timing of application. It is not only limited to rearing water but is also applicable for decontaminating pond liners, tanks, and other paraphernalia.

Analysis of Income from Mujair Fish (Oreochromis Massambicus) Cultivation in Tarpon Ponds (Biofloc) (A Case Study of Biofloc Business in Matungkas Village, Minut Regency)

This research investigates the economic viability of tilapia fish farming utilizing the pond liner method (biofloc) in Matungkas Village, Dimembe Subdistrict, North Minahasa Regency, Indonesia. With the agricultural, animal husbandry, and fisheries sectors playing pivotal roles in supporting Indonesia's economy, the study focuses on the freshwater fisheries potential, particularly tilapia, in North Minahasa. The research delves into the innovative use of biofloc technology, analyzing its benefits such as minimal water and land requirements, efficient feed utilization, and waste conversion into fish feed. Mr. Ronny Lensun's tilapia fish farming business, employing the pond liner method, is examined. Despite the region's rich natural resources, the income calculation method used by the owner is identified as simplistic. The study employs quantitative methods to perform a comprehensive income analysis, considering revenue, production costs, and financial metrics. Results demonstrate the profitability of Mr. Ronny Lensun's business, with a break-even point at a selling price of IDR 1,167,807.9 and a production volume of 33.36 kg. The Revenue Cost Ratio (R/C) is calculated at 1.85, indicating the business's sustainability and profitability. The literature review encompasses the biofloc technology and business analysis, emphasizing its advantages in water quality maintenance, organic matter decomposition, and feed efficiency. The study contributes to understanding the economic feasibility of tilapia fish farming with the biofloc method, suggesting potential for wider adoption and development in the region.

Assessment of geomembrane strain from pond liner bubbles

Bubbles (a.k.a. whales) that develop from gas entrapped beneath a geomembrane in pond liner applications lead to localized increases in geomembrane strain that warrant evaluation. Results from three-dimensional, geometrically-nonlinear, finite-element analysis are presented to show how geomembrane stiffness, fluid depth, volume of entrapped gas, and interface friction affect the deformed shape of, and maximum strain in the geomembrane. It is shown that the deformed geomembrane follows a bell-shaped curve and that geomembrane strain increases as the fluid depth increases until the bubble is submerged. The extent to which the maximum strain increases with decreasing geomembrane stiffness and increasing volume of entrapped gas are quantified. Design and operation charts are presented to provide a practical means of assessing strain in existing geomembrane bubbles or identify maximum fluid depths to limit geomembrane strain to a target value.

Enhanced CO2 bio-utilization with a liquid–liquid membrane contactor in a bench-scale microalgae raceway pond

Microalgae are able to absorb CO2 generated from sources such as flue gas to produce biomass with high lipid content. In this research, an immersed liquid–liquid membrane contactor was investigated to deliver CO2 captured by a chemical solvent to the microalgae culture via semipermeable membranes. Experiments showed that the CO2 mass transfer could be facilitated by using a thinner membrane support layer, or avoiding a support altogether, as the support was liquid filled which reduced the mass transfer coefficient. In order to better condition the culture media, the solvent flow was controlled by pH feedback. This scenario showed comparable biomass productivity (0.10 g L−1 d−1) to the conventional direct bubbling method, but with a lower energy cost and higher CO2 utilization efficiency. Further, a pond liner was formed from flat sheet membranes as a more effective alternative to a hollow fiber arrangement. The optimized system achieved a CO2 utilization efficiency of up to 90% compared to 47% with the uncontrolled hollow fiber membrane system and 11% for air sparging, thereby reducing the CO2 released to the atmosphere.

Formulation of Modified Dense Graded Bituminous Macadam with Low Density and High Density Polythene with Zykotherm Admixture

This study presents the use of waste polythene derived as carry bags from kitchen waste and pond liner polyethelene as LDPE and bottle caps as HDPE as an additive in flexible pavements. In this study we will also add a fix percentage of zykotherm. Purposes of using above materials are to utilize environmentally unacceptable waste material and to develop a better material mix to resist increased traffic load and temperature effect resulting cracks in the pavement surface. In the proposed study the plastic waste will be cleaned and cut into a size such that it passes through 2-3mm sieve using shredding machine. In this study Dense Bituminous Macadam (DBM) mix will be proposed to prepare by using plain bitumen as a control specimen and bitumen mixed with LDPE 2% and 4% & HDPE 2%, 3%, 4%, 5%) as by weight, with fixed percentage of Zykotherm as 1.5% by weight.Bitumen content is 4.5% by weight for all specimen. The Marshall Stability test, Penetration Test, and softening point test, were conducted on control and modified DBM mixes.

Soil sealing by algae: An alternative to plastic pond liners for outdoor algal cultivation

Commercial production of algal biofuels is currently limited by high capital costs, particularly costs of synthetic pond liners that minimize seepage of cultivation fluids, salts, and nutrients into the subsurface beneath outdoor algae cultivation facilities. Even some profitable nutraceutical companies bear the high costs of pond liners. However, studies of animal waste holding ponds and aquaculture facilities have shown that underlying soils can effectively “self-seal”, potentially eliminating the need for plastic liners. Here, we explored the potential for self-sealing with algae to provide an alternative to synthetic pond liners in unlined algae cultivation ponds. Laboratory-scale soil column experiments were used to investigate soil clogging by algae, a topic rarely discussed in the literature. Columns composed of fine sand, loamy sand, and loam soil displayed reductions in saturated hydraulic conductivity of the entire soil column of up to two orders of magnitude in response to infiltration by the alga Scenedesmus dimorphus suspended in algal culture nutrient solution at a density of 5 × 108 cells L−1. Scanning electron microscope imaging showed a dense algal layer on the surface of each soil column, thickly coating mineral grains with algal material and filling pore spaces. The algal coating was absent in samples at >3 cm depth in the soil columns, and measurements of chlorophyll content also confirmed that algal cells were mostly confined to the soil surface. In this study, the application of an algal suspension contributed significantly to soil sealing. This new application of biological sealing technology should be studied further to determine its utility and durability as an alternative to plastic liners, perhaps in conjunction with soil compaction to achieve hydraulic conductivities beneath algal production ponds that are protective of groundwater quality.

Autotrophic Microalgae Biomass Production: From Niche Markets to Commodities

Industrial BiotechnologyVol. 14, No. 1 CommentaryAutotrophic Microalgae Biomass Production: From Niche Markets to CommoditiesJohn R. Benemann, Ian Woertz, and Tryg LundquistJohn R. BenemannMicroBio Engineering Inc., San Luis Obispo, CASearch for more papers by this author, Ian WoertzMicroBio Engineering Inc., San Luis Obispo, CASearch for more papers by this author, and Tryg LundquistMicroBio Engineering Inc., San Luis Obispo, CACalifornia Polytechnic State University, San Luis Obispo, CASearch for more papers by this authorPublished Online:1 Feb 2018https://doi.org/10.1089/ind.2018.29118.jrbAboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View articleFiguresReferencesRelatedDetailsCited byA newly isolated alkaliphilic cyanobacterium for biomass production with direct air CO2 captureJournal of CO2 Utilization, Vol. 69Advancements in Microalgal Biorefinery Technologies and Their Economic Analysis and Positioning in Energy Resource Market21 February 2023 | Fermentation, Vol. 9, No. 3Two-stage cultivation of Spirulina sp. LEB 18: a strategy to increase biomass productivity and synthesis of macromolecules20 February 2023 | Brazilian Journal of Chemical Engineering, Vol. 11The marginal abatement cost of co-producing biomethane, food and biofertiliser in a circular economy systemRenewable and Sustainable Energy Reviews, Vol. 169Astaxanthin: A super antioxidant from microalgae and its therapeutic potential24 November 2021 | Journal of Basic Microbiology, Vol. 62, No. 9Minimum nitrogen cell quota for maximal growth rate in cycloturbidostat cultures of Picochlorum oklahomenseAlgal Research, Vol. 67Outdoor demonstration-scale flat plate photobioreactor for resource recovery with purple phototrophic bacteriaWater Research, Vol. 216A comparison between microalgal autotrophic growth and metabolite accumulation with heterotrophic, mixotrophic and photoheterotrophic cultivation modesRenewable and Sustainable Energy Reviews, Vol. 159Malaysian Virgin Soil Extracts as Natural Growth Enhancer for Targeted Green Microalgae Species17 April 2022 | Applied Sciences, Vol. 12, No. 8What Was Old Is New Again: The Pennate Diatom Haslea ostrearia (Gaillon) Simonsen in the Multi-Omic Age29 March 2022 | Marine Drugs, Vol. 20, No. 4Nannochloropsis oceanica harvested using electrocoagulation with alternative electrodes – An innovative approach on potential biomass applicationsBioresource Technology, Vol. 344Remediation of Pesticides by Microalgae as Feasible Approach in Agriculture: Bibliometric Strategies4 January 2022 | Agronomy, Vol. 12, No. 1Comparative life cycle assessment of a mesh ultra-thin layer photobioreactor and a tubular glass photobioreactor for the production of bioactive algae extractsBioresource Technology, Vol. 340Pilot-scale biorefining of Scenedesmus obliquus for the production of lipids and proteinsSeparation and Purification Technology, Vol. 270Microalgae proteins: production, separation, isolation, quantification, and application in food and feed28 May 2020 | Critical Reviews in Food Science and Nutrition, Vol. 61, No. 12Characterization of a novel strain of Tribonema minus demonstrating high biomass productivity in outdoor raceway pondsBioresource Technology, Vol. 331Microbes: Food for the Future28 April 2021 | Foods, Vol. 10, No. 5Cultivation of heterotrophic algae on paper waste material and digestateAlgal Research, Vol. 54Better management practices for environmentally sustainable production of microalgae and algal biofuelsJournal of Cleaner Production, Vol. 289Application of Microalgae Consortia/Cocultures in Wastewater Treatment8 July 2021Optimization of astaxanthin production processes from microalga HaematococcusNannochloropsis Oceanica Harvested Using Electrocoagulation with Alternative Electrodes – An Innovative Approach on Potential Biomass ApplicationsSSRN Electronic Journal, Vol. 41Biotechnological production of astaxanthin from the microalga Haematococcus pluvialisBiotechnology Advances, Vol. 43Exploring the sustainability and sealing mechanisms of unlined ponds for growing algae for fuel and other commodity-scale productsRenewable and Sustainable Energy Reviews, Vol. 121The effect of functional unit and co-product handling methods on life cycle assessment of an algal biorefineryAlgal Research, Vol. 46Bioremediation of water containing pesticides by microalgae: Mechanisms, methods, and prospects for future researchScience of The Total Environment, Vol. 707Nanotechnology and Abiotic Stresses13 May 2020Resource Recovery From Waste Streams Using Microalgae: Opportunities and ThreatsThe Future of Aquatic Protein: Implications for Protein Sources in Aquaculture DietsOne Earth, Vol. 1, No. 3Microalgae mixotrophic cultivation for β-galactosidase production16 January 2019 | Journal of Applied Phycology, Vol. 31, No. 3Soil sealing by algae: An alternative to plastic pond liners for outdoor algal cultivationAlgal Research, Vol. 38Recent Trends in Microalgae Research for Sustainable Energy Production and Biorefinery Applications1 May 2019 Volume 14Issue 1Feb 2018 InformationCopyright 2018, Mary Ann Liebert, Inc.To cite this article:John R. Benemann, Ian Woertz, and Tryg Lundquist.Autotrophic Microalgae Biomass Production: From Niche Markets to Commodities.Industrial Biotechnology.Feb 2018.3-10.http://doi.org/10.1089/ind.2018.29118.jrbPublished in Volume: 14 Issue 1: February 1, 2018PDF download

Open thin-layer cascade reactors for saline microalgae production evaluated in a physically simulated Mediterranean summer climate

While microalgae hold the promise for conversion of sunlight and CO2 to a wide variety of products, the economics of algae processes are still debatable. We have designed an open thin-layer cascade photobioreactor for high-cell density cultivation of saline microalgae to advance economic microalgae mass production. Pilot-scale reactors with a surface area of up to 8m2 (cultivation volume 50–140L) were constructed and evaluated using a dynamic climate simulation technology (light, air temperature and humidity) integrating natural sunlight and multi-color LED arrays for a highly realistic reproduction of the sunlight spectrum. Batch processes with Nannochloropsis salina were performed in these reactors in the physically simulated Mediterranean summer climate of Almería, Spain – an ideal location for outdoor microalgae cultivation. Two reactor variants were examined: one with a smooth but expensive rigid channel made of polyethylene sheets, and one with a more uneven but significantly less expensive channel made of pond liner. Maximal intra-day growth rates of 1.9d−1 were observed at a cell density of 1–3gL−1. The maximal cell density of 50gL−1 was obtained within 25days. These high growth rates and cell densities markedly exceed literature data. No difference in growth between the channel variants was observed. This suggests that cost-efficient large-scale thin-layer cascade reactors with inexpensive pond liner channels are feasible. The high cell density allows a reduction of harvesting cost. Optimal process conditions were identified by analyzing the batch and daily economic bioprocess metrics: At a cell density of 17gL−1, an areal biomass productivity of 25gm−2d−1 (volumetric productivity 4gL−1d−1) and a photosynthetic conversion efficiency of 4.6% were observed. The reactor design is discussed in detail to encourage further advancement of thin-layer algal cultivation technology.

Sunlight and sediment improve the environment of a litter biofilm-based shrimp culture system

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 9:73-85 (2017) - DOI: https://doi.org/10.3354/aei00213 FEATURE ARTICLE Sunlight and sediment improve the environment of a litter biofilm-based shrimp culture system Charles Gatune1,*, Ann Vanreusel2, Marleen De Troch2 1School of Natural Resources and Environmental Studies, Karatina University, PO Box 1957─10101, Karatina, Kenya 2Biology Department, Marine Biology, Ghent University, Campus Sterre, Krijgslaan 281-S8, 9000 Ghent, Belgium *Corresponding author: kgatune@yahoo.com ABSTRACT: In silvofishery, where shrimp culture is integrated with mangrove trees, the mangrove leaf litter may modify the environment in these culture systems. This study tested the potential of submerged leaf litter of Rhizophora mucronata and associated biofilm in providing a favorable environment for post-larval shrimp Penaeus monodon. Litter decomposition and assembly of microalgae and epifauna were assessed under exposure to sunlight or shade, and presence or absence of sediment. Litter incubated with sediment and exposed to sunlight was rapidly decomposed and supported the highest biomass and diversity of microalgae and epifauna. The litter also supported the highest abundance of diatoms, polychaetes and nematodes during the 4th week of decomposition. Cyanobacteria of the genus Microcystis dominated litter incubated without sediment, in sunlight, after decomposition for 5 wk. Under shaded conditions, diatoms of the genus Navicula and the Cyanobacteria Anabaena spp. and Oscillatoria spp. continued to grow at high total ammonium nitrogen, low dissolved oxygen, low temperature and low pH. Our study illustrates synergy between sediment and direct sunlight in promoting diversity of microalgae and polychaetes (of dietary benefit to shrimps), inhibiting growth of Cyanobacteria and maintaining water quality at levels favorable to culture of post-larval shrimp. Our findings support 4 practices for a healthy environment in fish ponds: (1) locating ecological shrimp culture in less forested areas, (2) promoting sediment conditions in artificial shrimp culture systems, (3) exposing litter-derived biofilm within ponds to sunlight and incubating with sediment to maintain favorable water quality and control Cyanobacteria blooms, and (4) minimizing the use of pond liners and related sludge removal. KEY WORDS: Shrimp culture · Sunlight · Sediment · Mangrove litter · Microalgae · Epifauna · Biofilm Full text in pdf format Information about this Feature Article PreviousNextCite this article as: Gatune C, Vanreusel A, De Troch M (2017) Sunlight and sediment improve the environment of a litter biofilm-based shrimp culture system. Aquacult Environ Interact 9:73-85. https://doi.org/10.3354/aei00213 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 9. Online publication date: February 08, 2017 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2017 Inter-Research.

The ecology and economics of shorebird conservation in a tropical human‐modified landscape

Summary Rapid and extensive land‐use change in intertidal foraging habitat and coastal roosting habitat is thought to be driving major population declines of shorebirds migrating through the East Asian–Australasian Flyway. Along the Inner Gulf of Thailand, a critical stopover and wintering ground for these birds, artificial wetlands (salt pans and aquaculture ponds) have replaced much of the natural coastal ecosystem. We conducted a two‐part study to (i) assess the importance of salt pans and semi‐traditional aquaculture ponds to shorebirds and (ii) understand the economic forces that drive land‐use change in this region by interviewing salt pan and aquaculture operators. Salt pans provide important roost habitat, particularly for shorter‐legged birds, which are less able to utilize aquaculture ponds due to their greater depth. Moreover, three focal shorebird species foraged extensively in salt pans and semi‐traditional aquaculture ponds, even when intertidal mudflats were exposed, suggesting that artificial wetlands could buffer against the impacts of degraded intertidal foraging areas for some shorebird species. Economic profits from salt production and semi‐traditional aquaculture are similar. Risks to investment and per capita profitability are key factors in determining whether to convert land from one use (e.g. salt pan) to the other (aquaculture). Synthesis and applications. Salt pans provide an important resource to migrating shorebirds. As development pressures increase, operators may need financial incentives if salt pans are to be maintained over large areas. Although semi‐traditional aquaculture is used less by shorebirds, drained ponds provide opportunities to roost and forage. Semi‐traditional aquaculture operators should drain their ponds regularly to provide supplementary habitat for shorebirds. Use of nets and pond liners should be discouraged in both systems. Optimizing aquaculture pond and salt pan management for shorebirds could provide a more pragmatic, cost‐effective and geographically extensive solution to conserving these birds than protected areas alone.

Fate and Transport of 17β-Estradiol beneath Animal Waste Holding Ponds.

Concentrated animal feeding operations typically store livestock waste in clay-lined ponds. Although these ponds are regulated to include a liner with a small hydraulic conductivity to limit leaching, previous studies have traced surface and groundwater contamination from such regulated animal waste ponds. This research examined the transport of 17β-estradiol (E2) and its primary metabolite, estrone (E1), through soil liners using field- and laboratory-based studies. Additionally, a potential engineering solution to limit hormone transport-applying biochar to new pond liners to act as a retardant-was studied. Soil cores 80 cm in length were collected beneath a mature dairy waste pond and analyzed for moisture content and hormone concentrations. Unsaturated conditions and E2 concentrations of 4 to 250 ng g were detected beneath the waste pond. In the laboratory portion of the study, hand-packed columns of sand or clay were subjected to infiltration by a 2.3-m head of dairy waste. A subset of the hand-packed sand columns was amended with powdered biochar to test its ability to retard E2 and E1. For 3 mo, column leachate was analyzed for hormone concentrations, and at the conclusion of the study E2 and E1 concentrations in the soil were measured. In the 44 d after sealing, the clay, sand, sand with a thin layer of biochar, and sand mixed with a biochar amendment leached a total of 0.54, 1.3, 0.09, and 0.45 μg of E2, respectively. The biochar amendments to the hand-packed columns considerably minimized E2 in the leachate.

Bisphenol-A extraction into water from a flexible PVC pond liner and its potential impact on artificial ponds

Bisphenol-A (BPA), a known ecological endocrine disruptor, is commonly used as an additive in the manufacture of flexible polyvinyl chloride (PVC) membranes. To assess the potential of artificial pond PVC liners as sources of BPA contamination, a laboratory extraction of BPA from a liner into water was conducted. The average blank-corrected BPA released by the liner, on a BPA/liner mass basis, was 28.4 ± 5.8 μg g−1. On the basis of surface area the amount released was 0.84 ± 0.16 μg cm−2. Given this quantity of BPA in a liner, a simple release model indicates that PVC pond liners are a potentially significant source of exposure of artificial pond aquatic organisms to BPA.

Infrastructure associated emissions for renewable diesel production from microalgae

Greenhouse gas (GHG) emissions for microalgae biofuel infrastructure are sometimes neglected during a life-cycle analysis (LCA). Construction materials were found for a baseline facility designed to produce renewable diesel in the United States. Material use was amortized over the material lifetime of thirty years and then, using emission factors available in GREET 2, energy use and GHG emissions were found per MJ of renewable diesel (MJ RD). For the baseline, infrastructure GHG emissions were 8.9gCO2e/MJ RD. Plastic and concrete had the largest emissions, and the growth ponds used the most materials of any unit operation. Fossil fuels comprised 97% of all energy use, which came predominately from natural gas at 0.090MJ/MJ RD. A sensitivity analysis showed that changes to the pond liner thickness and material lifetime had the largest effects with the lifetime increasing the GHG emissions 28% over the baseline. Increasing the productivity (up to 50g/m2/d) or lipid content (up to 50wt.%) decreased the emissions. Infrastructure emissions were compared to those from the fuel-cycle of a reduced emission scenario, showing that infrastructure related emissions ranged from 17% to 57% of the fuel-cycle emissions, with higher values at lower productivities.

Self-sealing evaporation ponds for small inland desalination facilities and containment equivalence concepts in Texas

Evaporation ponds are a low-maintenance option for disposing of desalination concentrate. Substantial savings can be achieved in Texas if exemptions are granted in the construction of pond liners. Currently approved liners include a ~0.9-m-thick layer of in situ or compacted clay (with hydraulic conductivity <10-7 cm/s) or a geomembrane liner >30 mil (0.075 cm). An alternative liner may also be used if it can be demonstrated to achieve and maintain equivalent containment capabilities with the preapproved liners. We examine (1) the possibility of incorporating a lowpermeability layer into the pond-liner system as a liner component or possibly as the liner itself as the pond water starts precipitating minerals, sealing any liner defect, and (2) the ability of the newlyformed minerals to, at minimum, plug liner defects. Assessment of previous laboratory experiments suggests that precipitation of a specific claylike mineral (sepiolite) could have many advantages. From geochemical calculations for assumed evaporation pond parameters, after 5 years of operation, an average precipitate thickness (mostly calcite and gypsum) is approximately 0.38 cm, containing about 7% sepiolite. Our analysis suggests that the precipitant, even with a conductivity >1× 10-7 cm/s, could efficiently plug defects of the geomembrane, allowing a thinner geomembrane to be used. On the other hand, the modest thickness of precipitant suggests that, to achieve equivalent containment, the precipitated material needs to have a conductivity <1×10-7 cm/s to impart the required properties to a scaled-down liner and to be successfully substituted in part or all of the clay liner. However, even if legal requirements are not fully met, self-sealing deposition could be advantageous in settings where an additional defense-in-depth layer is needed, such as areas with an underlying unconfined aquifer sensitive to contamination. In both cases (plugging defects or developing a blanket-like liner), cost remains an issue.

Use of clays as liners in solar ponds

An alternative to synthetic materials for use in solar pond liners is to select clayey soils as hydraulic barriers. This option reduces the cost of construction and the risk of contamination of subsoil and groundwater by hot brines. This paper deals with the physical, chemical and hydraulic properties of different soils tested mainly as compacted clay liners. The underdeveloped nations have the option to use this type of liner, but before doing so several tests are recommended, including those for soil and water composition, permeability, plasticity and X-ray diffraction analysis. In this investigation the following samples are analyzed: native clayey soils with illite, montmorillonite and halloysite, treated and non-treated bentonites in powder and granulated form, a mixture of zeolite and sodium bentonite, and industrial minerals composed largely of halloysite, kaolinite and attapulgite selected clays. Neutral salt aqueous solutions (NaCl and KCl) at different concentrations and under temperature gradients were used for compatibility testing conducted on these specimens. Experiment setup and particular testing procedures are also discussed.

Test of Multi-spectral Vegetation Index for Floating and Canopy-forming Submerged Vegetation

Remote sensing of terrestrial vegetation has been successful thanks to the unique spectral characteristics of green vegetation, low reflectance in red and high reflectance in Near-InfraRed (NIR). These spectral characteristics were used to develop vegetation indices, including Normalized Difference Vegetation Index (NDVI). However, the NIR absorption by water and light scattering from suspended particles reduces the practical application of such indices in aquatic vegetation studies, especially for the Submerged Aquatic Vegetation (SAV) that grows below water surface. We experimentally tested if NDVI can be used to depict canopies of aquatic plants in shallow waters. A 100-gallonoutdoor tank was lined with black pond liners, a black panel or SAV shoots were mounted on the bottom, and filled with water up to 0.5 m. We used a GER 1500 spectroradiometer to collect spectral data over floating waterhyacinth (Eichhornia crassipes) and also over the tanks that contain SAV and black panel at varying water depths. The measured upwelling radiance was converted to % reflectance; and we integrated the hyperspectral reflectance to match the Red and NIR bands of three satellite sensors: Landsat 7 ETM, SPOT 5 HRG, and ASTER. NDVI values ranged 0.6-0.65 when the SAV canopy was at the water level, then they decreased linearly (slope of 0.013 NDVI/meter) with water depth increases in clear water. When corrected for water attenuation using the data obtained from the black panel, the NDVI values significantly increased at all depths that we tested (0.1 - 0.5 m). Our results suggest the conventional NDVI: (1) can be used to depict SAV canopies at water surface; (2) is not a good indicator for SAV that is adapted to live underwater or other aquatic plants that are submerged during flooding even at shallow waters (0.3 m); and (3) the index values can significantly improve if information on spectral reflectance attenuation caused by water volume increases is collected simultaneously through ground-truthing and integrated.

Hyperfiltration of Nacl Solutions Using a Simulated Clay/Sand Mixture at Low Compaction Pressures

It is widely recognized that clays and shales can demonstrate membrane properties. When a hydraulic head differential exists across a membrane-functioning clay-rich barrier, some of the solute is rejected by the membrane. This process is known as hyperfiltration. Some shallow geologic environments, including aquitards bounding shallow perched aquifers and unconfined aquifers, some river and stream beds, and some lake bottoms contain clay–soil mixes. Many engineering structures such as landfill liners, mixed soil augered barriers, and retention pond liners also consist of soil–clay mixes. No previous testing has been performed to investigate the likelihood that hyperfiltration may occur in such mixed soils. Therefore, we performed five experiments using different mixes of Na-bentonite and glass beads (100, 50, 25, 12 and 0% clay) to determine if any of these mixes exhibited membrane properties and to investigate what effect clay content had upon the membrane properties of the soil. Each mixture was compacted to 345 kPa and the sample mixtures were 0.58–0.97 mm thick. All the experiments used an approximately 35 ppm Cl− solution under an average 103 kPa hydraulic head. Experimental results show that all the simulated clay–sand mixtures do exhibit measurable membrane properties under these conditions. Values of the calculated reflection coefficient ranged from a low of 0.03 for 12% bentonite to 0.19 for 100% bentonite. Solute rejection ranged from 5.2% for 12% clay to a high of over 30% for the 100% clay. The 100% glass bead sample exhibited no membrane properties.

Reverse osmosis properties of bentonite/glass bead mixtures at low compaction pressures

It is well-known that clays and shales can be membrane-functioning. When a hydraulic head difference exists across a membrane-functioning barrier, a portion of the solute is rejected from solution passing through the membrane. Many engineering structures such as landfill liners, mixed soil augered barriers, and retention pond liners consist of soil-clay mixes, which may have clay contents as low as 12%. Some shallow geologic environments may also contain similar clay/soil mixes. No previous testing has been performed to investigate hydraulic-head-induced solute rejection in such mixed soils. Therefore, we performed six experiments using five different mixes of Na-bentonite and glass beads (100%, 50%, 25%, 12%, and 0% clay) to determine if any of these mixes exhibited membrane properties and to determine what effect clay content had upon the membrane properties. All the mixtures were compacted to 690 kPa and the compacted soil samples were 0.56–1.40 mm thick. An approximately 35 ppm Cl− solution and a hydraulic head of approximately 90 kPa were used for all experiments. Experimental data shows that these simulated clay–sand mixtures do exhibit measurable membrane properties with as low as 12% clay by weight under these conditions. Calculated reflection coefficient values ranged from a low of 0.07 for 12% Na-bentonite to a high of 0.26 for 100% clay. Solute rejection ranged from 12.6% for 12% clay to a high of more than 40% for the 50% and 100% clay samples. The glass beads represent fine-grained sand and were shown to have no membrane properties.

Some Practical Observations on the Use of Bentonite

There are two types of bentonite: (1) the sodium, high-swelling type, derived from volcanic ash that was deposited in marine environments; and (2) the calcium, low-swelling type, which evolved from volcanic ash deposited in freshwater environments. Bentonites are used in industry as drilling muds, foundry sand binders, animal feed binders, binders and carriers for pesticides and drugs, binders for iron ore pelletizing (taconite), landfill and pond liners, thickeners for slurry trenches, and flocculents. There is an extensive body of literature available related to the swelling properties of montmorillonite extending back to 1954 (Norrish, 1954; Odom and Low, 1978). Practical observations, however, are seldom included, probably because those who are active in that field do not publish their observations. A high-quality industrial bentonite is very pure, typically consisting of 95 percent montmorillonite, plus 5 percent shale, feldspar, goethite, gypsum, celestite, and/or cristobalite. It has a cation ion exchange capacity of 70–90 meq/100 g. An early article by Alther (1986) showed that the ratio of sodium to calcium and magnesium on the surface of a clay platelet determines the quality of a bentonite as a drilling mud, landfill liner, and other applications that require a large swelling capacity (i.e., maximum dispersion of the clay platelets upon wetting [a high level of purity is assumed]). These bentonites are usually yellow in color and rich in oxidized iron. They occur in seams near the ground surface where percolating groundwater delivers dissolved oxygen, which oxidizes the iron. By contrast, specifications for bentonites for steel foundries (Steel Foundries Society of America, 1965) require a gray colored bentonite with a high methylene blue cation exchange capacity (commonly 100 meq/g or more), a high-swelling capacity (17 mL/g of clay or more), high liquid limits (600 or more), very low filter loss, and relatively low Fann viscosities (an …