Sequential Reuse Research Articles

Oxygen atmosphere enhances ball milling remediation of petroleum-contaminated soil and reuse as adsorptive/catalytic materials for wastewater treatment

Ball milling is an environmentally friendly technology for the remediation of petroleum-contaminated soil (PCS), but the cleanup of organic pollutants requires a long time, and the post-remediation soil needs an economically viable disposal/reuse strategy due to its vast volume. The present paper develops a ball milling process under oxygen atmosphere to enhance PCS remediation and reuse the obtained carbonized soil (BCS-O) as wastewater treatment materials. The total petroleum hydrocarbon removal rates by ball milling under vacuum, air, and oxygen atmospheres are 39.83%, 55.21%, and 93.84%, respectively. The Langmuir and pseudo second-order models satisfactorily describe the adsorption capacity and behavior of BCS-O for transition metals. The Cu2+, Ni2+, and Mn2+ adsorbed onto BCS-O were mainly bound to metal carbonates and metal oxides. Furthermore, BCS-O can effectively activate persulfate (PDS) oxidation to degrade aniline, while BCS-O loaded with transition metal (BCS-O-Me) shows better activation efficiency and reusability. BCS-O and BCS-O-Me activated PDS oxidation systems are dominated by 1O2 oxidation and electron transfer. The main active sites are oxygen-containing functional groups, vacancy defects, and graphitized carbon. The oxygen-containing functional groups and vacancy defects primarily activate PDS to generate 1O2 and attack aniline. Graphitized carbon promotes aniline degradation by accelerating electron transfer. The paper develops an innovative strategy to simultaneously realize efficient remediation of PCS and sequential reuse of the post-remediation soil.

Sequential reuse of remediated soil from petroleum-contaminated site to recover transition heavy metals and activate peroxysulphate oxidation

Pyrolysis can rapidly remediate petroleum-contaminated soil (PCS) and recover some liquid oil, but less attention has been paid to the reuse potential and strategy of the remediated carbonized soil (RCS). In this study, RCS was used as adsorbent to recover Mn2+, Ni2+, and Cu2+ from wastewater. The solid residue (RCS-Me) was reused to activate peroxysulphate oxidation. The total petroleum hydrocarbons and dissolved organic matter can be completely removed by pyrolysis at 500 °C for 3 h. The maximum adsorption capacities of RCS for Cu2+, Ni2+, and Mn2+ are 65.96, 50.75, and 57.95 mg/g, respectively. Sequential extraction analysis shows that transition heavy metals are mainly bound to carbonate and Fe/Mn oxides. RCS and RCS-Me can effectively activate peroxysulphate to degrade aniline, and the activation performance and reusability of RCS-Me are remarkably better than RCS. The nonradical path dominates in the oxidation process, and the main species are hole and 1O2. Electron paramagnetic resonance and linear sweep voltammetry analysis show that hole improves the activation efficiency mainly by accelerating direct electron transfer, while the oxygen-containing groups and oxygen vacancies may activate peroxysulphate to generate 1O2.The strategy can simultaneously realize efficient remediation of PCS and sequential resource utilization of the remediated soil.

Design and economic evaluation of a novel amine-based CO2 capture process for SMR-based hydrogen production plants

Chemical absorption using amine solvents is the most commercially recognized technology to capture CO2 from the SMR-based hydrogen production plant. Most studies focused on the use of PSA inlet or tail gas streams to remove CO2 using MDEA solvent which is limited to about 60% of total plant CO2 emitted. Whilst the capture of a flue gas stream has been reported via the MEA solvent to remove 90% CO2 yet at relatively higher costs. A systematic investigation is required to identify the cost-effective use of the absorption processes when multiple positions are available for CO2 capture. In this study, multiple cases of the CO2 absorption process have been evaluated using MEA or MDEA solvents. Especially, a novel design for the simultaneous removal of CO2 from the flue gas of a reformer and the PSA inlet gas stream is proposed and its techno-economic benefits are examined. For this purpose, the rate-based model has been implemented in the MATLAB environment to simulate the absorption process, whereas the solvent regeneration energy and the capital and operating costs of the main equipment have been estimated using the correlations taken from the literature. The new system based on the sequential reuse of MEA solvent for two streams is found to be the most economic process to remove 99% of total plant CO2. The annualized cost of the proposed system is found 17.9% less in comparison to the best relevant conventional studied system of simultaneously removing CO2 from the PSA inlet and reformer flue gas streams using MEA and MDEA solvents.

Water and Nutrient Balance in an Ornamental Cascade Cropping System

Seedlings of Chrysalidocarpus lutescens, Dracaena deremensis and Dracaena marginata were grown in plastic containers filled with sphagnum peat-moss to assess the effects of three different water systems on plant growth, water saving and nutrient removal during the experimental period. The experiment lasted for 8 weeks and consisted of three water systems. These consisted of an open draining system fertigated with a standard nutrient solution (system T0) and two closed systems: sequential reuse of the leachate (system T1) and sequential reuse of the leachate with the addition of H2O2 (system T2). Over the course of the experiment, samples of water and supplies generated in each water treatment were collected weekly, and from these data water volume and nutrient loads were calculated. The addition of H2O2 to the leachate resulted in an enhancement in plant dry weight in Dracaena deremensis and Dracaena marginata. Regarding anion loads (Cl−, NO3−, H2PO4−, SO42−) in these water systems, there was a removal rate of 42%, 28%, 27% and 28%, respectively, in the closed systems compared to the open system. For the cation loads (Na+, K+, Ca2+ and Mg2+) in these water systems, there was a removal rate from 28% to 29%, respectively, in the closed systems compared to the open system.

Characterisation and Environmental Value Proposition of Reuse Models for Fast-Moving Consumer Goods: Reusable Packaging and Products

Problem: Fast-Moving Consumer Goods (FMCGs) are products that are purchased and consumed frequently to satisfy continuous consumer demand. In a linear economy, FMCGs are typically offered as single-use and disposable products. Limitations in product design, insufficient collection systems, and inefficient recovery processes prevent high recycling rates. As a result, FMCGs often end up in landfill or the environment, contributing to waste accumulation, and pollution. Whilst recycling is the most common waste prevention strategy practiced by the industry, the process is limited to addressing only the final stage of the product life cycle, omitting the overproduction and consumption of materials typical of FMCGs. Instead, reuse is a strategy that is capable of extending the value of resources by slowing material flows. Novel reuse models that require the consumer to interact with durable primary packaging and products are emerging in the FMCG industry. However, the constituent elements and operation principles of such reuse models are not fully understood. The aim of this research is to develop a comprehensive characterisation of reuse models and to evaluate their potential to deliver environmental value. Method: Ninety-two reuse offerings were selected and analysed to identify their reuse system elements. The analysis led to the identification of a framework including five reuse models, which were also evaluated to establish their capability to deliver environmental value when compared to conventional single-use and disposable FMCGs. Results: Currently in the FMCG sector, reusable products are mostly durable packaging, such as bottles and containers for beverages, foods, personal and home care goods, and are infrequently durable products, such as personal and baby care goods, including razors and nappies. Three reuse models involve exclusive reuse, a behaviour by which a reusable product is used and kept by a single user throughout the product lifetime. In exclusive reuse models, users are provided with either a reusable product (model 1), a reusable product with preparation for reuse infrastructure (model 2), or access to preparation for reuse infrastructure (model 3). Two reuse models involve sequential reuse, a behaviour by which a reusable product is used by multiple users throughout the product lifetime and returned after each use to a provider. In sequential reuse models, users are provided with either a reusable product with preparation for reuse infrastructure and provider-operated recovery services (model 4), or a reusable product and provider-operated services for recovery and preparation for reuse (model 5). Whilst the five reuse models can operate standalone, some offerings were found to embed a multi-model approach. Both exclusive and sequential reuse models are capable of delivering environmental value by reducing the use of natural resources and retaining their value in the economy. In particular, sequential reuse models were found to have a greater capability to increase the share of recyclable resources by offering access to infrastructure for the closure of material loops. Conclusions: Consumers can currently access five reuse models and choose between exclusive and sequential reuse behaviours. When adopted in conjunction with recycling, reuse models can enable a more efficient consumption of FMCGs. Providing the infrastructure necessary to enable reuse and recycling is key to the successful and sustainable deployment of the reuse models.

Preparation of photo-crosslinkable cinnamate modified hyaluronic acid for immobilization of horseradish peroxidase

Abstract In this work, a photo-responsive hydrogel membrane based on cinnamate-modified hyaluronic acid (HA-CM) was developed and safely cross-linked under UV light curing. The obtained material was effectively utilized for immobilization of horseradish peroxidase (HRP) enzyme via encapsulation and entrapment strategy with efficiency above 95%. The prepared HA-CM biopolymer was investigated before the UV curing using instrumental and spectral techniques including Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR). During the UV irradiation, the progress of the cross-linking reaction was monitored by the UV–vis light spectroscopy. In addition, when the photo-induced cross-linking had accomplished, the morphological appearance of the hydrogel membrane was recorded using a scanning electron microscope (SEM). The HRP immobilized in HA-CM membranes displayed remarkable stability against the environmental pH changes especially under alkaline media and shift the optimum pH to 8 compared to the free HRP, which exhibited the highest activity at pH 7. Also, the entrapped enzyme was able to preserve above 85% of its catalytic activity at higher temperature values where the free enzyme had deactivated by approximately 50%. Moreover, HA-CM-HRP maintained 87% of its activity after 10 sequential reuse cycles, which indicate the economic value of the employed immobilization strategy.

Iron mining wastes collected from Mariana disaster: Reuse and application as catalyst in a heterogeneous electro-Fenton process

A simple and environmental friendly strategy for recycling iron mining wastes from the Mariana disaster, one of the biggest environmental disasters in Brazil, involved the synthesis of a magnetic hybrid (HbLM) material at ambient temperature. XRD analysis revealed formation of the cobalt ferrite phase, while FTIR and TGA confirmed the presence of NOM in the structures. The HbLM showed high surface area of about 167.9 m2 g−1. Heterogeneous electro-Fenton (EF)-HbLM process achieved the total decolorization of a model pollutant, the Acid blue 29 diazo dye, after 20 min of electrolysis; while the electrochemical oxidation with hydrogen peroxide generation (EO-H2O2) only led to 62% of color removal. The limit current density was 33.3 mA cm−2, above this value the parasitic reactions overlapped, consequently the efficiency of the process decreased. At pH 3.0, complete color removal was achieved after 20 min of treatment while 60 min were necessary at pH 7.0 (natural pH). This means that, at neutral pH, the process is feasible and the acidification of the medium is not necessary to promote the main reactions. This work provides an example of a system to remove toxic contaminants from wastewater following the principles of green chemistry and industrial symbiosis, with sequential reuse of wastes and the generation of new raw materials with added commercial and technological values.

Papain Immobilization on NiFe2O4 Magnetic Nanoparticles Functionalized with Gallic Acid and Microwave Assisted Digestion of Bovine Serum Albumin

NiFe2O4 magnetic nanoparticles were solvothermally prepared. NiFe2O4 magnetic nanoparticles were functionalized with gallic acid and then papain immobilized on NiFe2O4 functionalized with gallic acid. The obtained samples were characterized and the activities of free and immobilized papain were studied. Immobilized papain showed higher and more effective activity than free papain. This immobilized papain retained about 75.5% of its initial activity after 8 weeks of storage at 4 °C in sodium phosphate buffer (0.1 M, pH 6.5), while the free trypsin protected 30.5% of its initial activity during the same condition. Furthermore, the immobilized papain protected approximately 51% of its initial activity following the times of ten sequential reuse. Finally, the microwave assisted digestion of bovine serum albumin was carried out for 15 s with matrix-assisted laser desorption/ionization mass spectrometry by using free and immobilized papain.

Cascade Cropping System with Horticultural and Ornamental Plants under Greenhouse Conditions

The blending of drainage with water of low electrical conductivity and the sequential reuse of the drainage water are innovative technologies to manage salts in agricultural drainage. Plants of Cucumis melo were grown in coir grow bags, and Rosmarinus officinalis and Cacti spp. were grown in pots with a mixture of sphagnum peat-moss and perlite. In order to assess the effect and evolution over time of these water treatments on plant growth and water management and removal of nutrients, three water treatments were applied over a period of eight weeks. These were: (1) standard nutrient solution; (2) blended water treatment (drainage water blended with water of low electrical conductivity (EC)) and (3) sequential reuse of drainage water treatment. During the experimental growing period, samples of water supplies and drainages generated in each water treatment were collected weekly and from these data water volume and nutrient loads were calculated. At the end of the experiment, leaf fresh weight of rosemary plants decreased under the fertigation with the blended and sequential reuse water treatments. Nevertheless, the application of blended and sequentially reused water allowed for the saving of significant amounts of water and nutrients in comparison to the standard nutrient solution treatment. Considering these advantages, we strongly recommend the setting-up of these water treatments in areas with water scarcity such as in the Mediterranean Basin.

Crop and Irrigation Management Systems under Greenhouse Conditions

Plants of Ruscus aculeatus, known as “butcher’s broom”, Maytenus senegalensis, known as “confetti tree”, and Juncus acutus, known as “spiny rush” were grown in pots with a mixture of sphagnum peat-moss and Perlite in order to determine the effect and evolution over time of three water use systems on plant growth, water saving and nutrient uptake. These were an open system (irrigated with standard nutrient solution) and two closed systems (blended-water (drainage water blended with water of low electrical conductivity (EC)) and sequential reuse of drainage (sequential-reuse) water), over a period of 8 weeks. Irrigation with blended- and sequential-reuse-water increased the biomass of all three species at the end of the experiment, compared to the open system. Overall, sequential-reuse-water treatment maximised biomass production. The application of blended- and sequential-reuse-water allowed savings of 17% of water in comparison to the open system. Regarding Cl, NO3− and H2PO4− loads, there was a removal of 5%, 32% and 32%; respectively in the blended-water treatment and 15%, 17% and 17% in the sequential-reuse water treatment compared to the open system. For the cation loads (Na+, K+, Ca2+ and Mg2+) in these water treatments there was a removal of 10%, 32%, 7% and 18% respectively in the blended-water treatment, and 17%, 22%, 17% and 18% respectively in the sequential-reuse treatment, compared to the open system.

Nutritional responses of Cordyline fruticosa var. ‘Red Edge’ to fertigation with leachates vs. conventional fertigation: Sodium, potassium, calcium and magnesium

The sequential reuse of drainage water in greenhouse horticulture production to grow successively more salt tolerant crops is proposed as a sustainable alternative to recirculation systems when the irrigation water quality is low. This practice is known as Serial Biological Concentration or Integrated Farm Drainage Management. The objective of this assay was to assess the nutritional responses of Cordyline fruticosa var. ‘Red Edge’ (a semi-tolerant crop) fertigated with leachates from Citrullus lanatus (horticultural crop) cultivated on rockwool, compared to a conventional fertigation. Four treatments were tested: T1 (nutritionally balanced control or standard nutrient solution, with an electrical conductivity (EC) of 2.5dSm−1); T2 (saline control; T2 diluted to an EC of 1.5dSm−1, afterwards, NaCl was added to achieve 2.5dSm−1);T3 (pure leachate from the hydroponic culture of C. lanatus), and T4 (diluted leachates, T3 diluted with irrigation water to 2.5dSm−1). At the end of the trial, biometric parameters were determined and Na+, K+, Ca2+ and Mg2+ concentrations and the accumulation in photosynthetic organs (leaves), conductive organs (stems and petioles) and absorption organs (roots) were measured. The treatments tested had no effect on the number of leaves, leaf area per plant, leaf size, plant fresh and dry weight and shoot:root dry weight ratio. Nevertheless, the plants fertigated with pure leachates were significantly smaller. Regarding the plants’ fresh:dry weight ratio, this was significantly lower when plants were fertigated with pure leachates than with diluted leachates. The use of pure leachates does not cause an increment in total Na+ accumulation with respect to the nutritionally balanced control because Na+ concentration increases only in stems and petioles. Total K+ accumulation decreased when plants were irrigated with solutions with high concentrations of NaCl. The high Ca2+ concentration in the non-diluted leachate led to a high total Ca2+ accumulation. Total Mg2+ accumulation was affected negatively by Ca2+ uptake. It can be concluded that diluted leachates from C. lanatus can be used for the fertigation of C. fruticosa.

Nutritional responses of Cordyline fruticosa var. ‘Red Edge’ to fertigation with leachates vs. conventional fertigation: Chloride, nitrogen, phosphorus and sulphate

In closed soilless growing systems, leachates are used for the fertigation of the same culture, which is known as recirculation. This technology has been widely studied. It constitutes an environmentally friendly system because it prevents the leaching of chemicals into the environment, contributing to the sustainability of the horticultural sector. Nevertheless, the use of low quality water makes its application difficult. Moreover, as salinity increases in leachates, specific ions may become toxic or interfere with the uptake of other nutrients. In these situations, the sequential reuse of drainage waters to grow successively more salt tolerant crops, a practice which is known as Serial Biological Concentration or Integrated Farm Drainage Management, may be proposed. The aim of this trial was to assess the nutritional responses of Cordyline fruticosa var. ‘Red Edge’ (a semi-tolerant crop) fertigated with leachates from Citrullus lanatus cultivated on rockwool, compared with to conventional fertigation. There were 4 treatments: T1 (nutritionally balanced control or standard nutrient solution, with an electrical conductivity (EC) of 2.5dSm−1),T2 (saline control; T2 diluted to an EC of 1.5dSm−1; afterwards, NaCl was added to achieve 2.5dSm−1),T3 (pure leachates from the hydroponic culture of C. lanatus) and T4 (diluted leachates, T3 diluted with irrigation water to 2.5dSm−1). Dry weight (DW) and Cl−, N, P and SO42− concentrations as well as the extraction of photosynthetic organs (leaves), conductive organs (stems and petioles) and absorption organs (roots) were measured. The results obtained confirmed that diluted leachates can be employed for the fertigation of C. fruticosa ‘Red Edge’, because there were no effects on the plants DW, and no significant differences in Cl−, N, P or SO42− concentrations in leaves with respect to the nutritionally balanced control.

Interface structural effect of ruthenium-cerium oxide nanocomposite on its catalytic activity for selective oxidation of bioterpenes-derived p-cymene

An efficient catalyzed liquid-phase selective oxidation of p-cymene to tertiary cymene hydroperoxide (TCHP) and its derivative p-methylacetophenone (PMAP) was achieved over a nanostructured ruthenium-cerium oxide (Ru/CeO2) composite catalyst with remarkable activity using a green molecular oxygen oxidant. Both of the composite catalysts were prepared from CeO2 oxide with different particles sizes [i.e., bulk CeO2 (Ru/b-CeO2) and nanosized CeO2 (Ru/n-CeO2)]. The n-Ru/CeO2 exhibited high catalytic activity for the free-radical driven oxyfunctionalization reaction of the inert CH bond in p-cymene to afford up to 55% conversion within 5h at 65% TCHP and 26% PMAP selectivity. The combined ratio of the TCHP/PMAP selectivity was dependent on the reaction time and the amount of p-cymene conversion. An increase in the reaction time resulted in converted large amount of TCHP to PMAP. The better catalytic performance of the Ru/n-CeO2 catalyst compared to Ru/b-CeO2 was partially due to the catalyst redox and oxygen vacancies effect. Both the reduced and oxidized forms of Ru/n-CeO2 were investigated to gain insight into the active form of the catalyst. The reduced Ru/n-CeO2 catalyst exhibited poor performance compared to the high catalytic performance of the oxidized form. This result demonstrated the significant concomitant effect of the balanced Ru4+/Ru3+ and Ce4+/Ce3+ redox combination to facilitate the free-radical driven mechanism via the excitation of O2 to activate the substrate inert CH. The Ru/n-CeO2 catalyst was highly recyclable with consistent activity after its sequential re-use. The catalytic performance of Ru/n-CeO2 was correlated to its structural characteristics based on the results from complimentary techniques, such as powder XRD, Raman spectroscopy, HRTEM, BET SA nitrogen physisorption, FESEM, H2-TPR and EDX. According to the characterization results, the enhanced catalytic performance of the Ru NPs loaded on CeO2 with nanosized particles was due to intrinsic metal-metal oxide interactions, enhanced redox cycles and high oxygen mobility resulting from structural defects of n-CeO2 that form oxygen vacancies compared to dispersed on the bulk CeO2 with large particles. The catalytic activity exhibited by Ru/CeO2 provides encouraging results to add to the class of active and stable catalysts for the activation of typical alkyl aromatic hydrocarbons, such as the p-cymene inert CH bond, for the selective introduction of an oxygen atom.

Low-cost hemp biomaterials for nickel ions removal from aqueous solutions

This study investigates an alternative use of hemp-based materials either in hemp fiber (HF) or shive (HS) form as biosorbents for the removal of Ni(II) from aqueous solutions. The hemp materials were used either in raw form or after chemical modification with sodium hydroxide and citric acid in order to remove any impurities and add extra carboxyl groups (which improve the adsorption), respectively. A series of adsorption experiments was carried out to determine the effect of (i) solution pH on Ni(II) adsorption, (ii) contact time (kinetics fitted to linear pseudo-first, -second order equations and Elovich model), and (iii) initial ion concentration (fitting to Langmuir, Freundlich and Langmuir–Freundlich equations). Furthermore, a complete characterization study (FTIR, XRD, SEM/EDAX, crystallinity, and cellulose content) demonstrated the surface morphology of the prepared hemp-materials along with some possible adsorption interactions between them and ions. The regeneration of materials was confirmed running desorption experiments (effect of solution pH on desorption) finding also the optimum desorption contact time (kinetics fitted to non-linear pseudo-first and -second order equations). Ten sequential reuse cycles (at the optimum conditions found after adsorption and desorption experiments) revealed the reuse potential of the low-cost hemp-based materials.

Effect of immobilized cells in calcium alginate beads in alcoholic fermentation

Saccharomyces cerevisiae cells were immobilized in calcium alginate and chitosan-covered calcium alginate beads and studied in the fermentation of glucose and sucrose for ethanol production. The batch fermentations were carried out in an orbital shaker and assessed by monitoring the concentration of substrate and product with HPLC. Cell immobilization in calcium alginate beads and chitosan-covered calcium alginate beads allowed reuse of the beads in eight sequential fermentation cycles of 10 h each. The final concentration of ethanol using free cells was 40 g L-1 and the yields using glucose and sucrose as carbon sources were 78% and 74.3%, respectively. For immobilized cells in calcium alginate beads, the final ethanol concentration from glucose was 32.9 ± 1.7 g L-1 with a 64.5 ± 3.4% yield, while the final ethanol concentration from sucrose was 33.5 ± 4.6 g L-1 with a 64.5 ± 8.6% yield. For immobilized cells in chitosan-covered calcium alginate beads, the ethanol concentration from glucose was 30.7 ± 1.4 g L-1 with a 61.1 ± 2.8% yield, while the final ethanol concentration from sucrose was 31.8 ± 6.9 g L-1 with a 62.1 ± 12.8% yield. The immobilized cells allowed eight 10 h sequential reuse cycles to be carried out with stable final ethanol concentrations. In addition, there was no need to use antibiotics and no contamination was observed. After the eighth cycle, there was a significant rupture of the beads making them inappropriate for reuse.

Economic and agronomic strategies to achieve sustainable irrigation

The achievement of sustainable irrigation in arid regions requires greater attention to waterlogging, salinization, and degradation of ground and surface waters, which are among the problems that continue to threaten productivity and degrade environmental quality. We consider sustainability to be achieved when irrigation and drainage are conducted on-farm, and within irrigation districts, in a manner that does not degrade the quality of land, water, and other natural resources, either on-farm or throughout an irrigated region. Sustainability may also be described as maintaining the productive resources required for irrigation, so that future generations may have the same opportunity to use those resources as we do. Given the increasing importance of irrigated land for food production, the time has come when it is vital to intercept, reuse, and isolate drainage waters within the regions in which they are generated. Adoption of this strategy can be enhanced by policies that require farmers, and irrigation districts, to consider the off-farm impacts of irrigation and drainage. Such policies include linking water rights with salt rights to require the monitoring and management of both irrigation water and the salt loads in drainage waters. We review the knowledge gained since the early 1970s regarding the economic and agronomic aspects of irrigation and drainage, with a focus on drainage water reduction and sequential reuse of drainage water on salt-tolerant crops. Economic incentives that motivate farm-level and district-level improvements in water management are also reviewed. We conclude that adequate knowledge exists for implementing strategies that focus on water use and salt disposal within irrigated regions, and we recommend policies that will motivate improvements in productivity and enhance the likelihood of achieving sustainability.

Effect of Travel Time on Management of a Sequential Reuse Drainage Operation

Sequential reuse of agricultural drainage water recovered in tile lines has been proposed as a strategy for reducing drainage volume in the western San Joaquin Valley of California. In this system, high-quality water is used to grow a salt-sensitive crop, and the drainage from this operation is collected by tile lines and subsequently used on a more salt-tolerant crop. This process is continued on progressively more salt-tolerant species until the final residual is collected and sent to evaporation ponds. In this paper we develop a transfer function model for simulating the drainage concentrations of each stage of a sequential reuse project. Transient salt concentrations are calculated for typical drain spacings and water management strategies, under the assumption that downward movement of water is eventually restricted by a subsurface barrier. Results of the calculations show that response times of fields managed in this way are extremely long, so that the drain lines primarily capture resident ground water for decades or more after the operation is started, especially if the barrier is assumed to be at a substantial depth below the surface. As a result, the system will never reach steady state in any practical period of time, and system design strategies based on steady state behavior will be flawed.

Managing selenium-contaminated agricultural drainage water by the integrated on-farm drainage management system: role of selenium volatilization

The Integrated on-Farm Drainage Management (IFDM) system was designed to dispose of selenium (Se)-contaminated agricultural irrigation drainage water through the sequential reuse of saline drainage water to grow crops having different salt tolerance. This study quantified the extent of biological volatilization in Se removal from the IFDM system located in the western San Joaquin Valley, California. Selenium volatilization from selected treatment areas, including pickleweed ( Salicornia bigelovii Torr.), saltgrass ( Distichlis spicata L.), bare soil, and the solar evaporator, was monitored biweekly using an open-flow sampling chamber system during the pickleweed growing season from February to September 1997, and monthly from September 1997 to January 1998. Biological volatilization from the pickleweed section removed 62.0±3.6 mg Se m −2 y −1 to the atmosphere, which was 5.5-fold greater than the Se accumulated in pickleweed tissues (i.e., phytoextraction). The total Se removed by volatilization from the bare soil, saltgrass, and the solar evaporator was 16.7±1.1, 4.8±0.3, and 4.3±0.9 mg Se m −2 y −1, respectively. Selenium removal by volatilization accounted for 6.5% of the annual total Se input (957.7 mg Se m −2 y −1) in the pickleweed field, and about 1% of the total Se input (432.7 mg Se m −2 y −1) in the solar evaporator. We concluded that Se volatilization under naturally occurring field conditions represented a relatively minor, but environmentally important pathway of Se removal from the IFDM system.

A combined hardware/software approach for fast kinematic processing

In this paper we present an integrated approach for very fast kinematic computations in multibody systems with complex structure. The approach relies on using optimized algorithms for generation of symbolic equations for kinematics together with application-specific hardware for their computation. The kinematic equations are optimized by incorporating closed-form solutions wherever possible. For optimized hardware, a computer board has been developed, which includes a single CORDIC processor ( COordinate Rotation in DIgital Computer) for the computation of transcendent functions, as well as a DSP processor for implementation of basic arithmetic operations. To compute the kinematic equations a widespread method is to realize equivalent CORDIC processor arrays. Due to the large number of processors required, this method results in very high costs and is less flexible. With the board presented here it is feasible to emulate these CORDIC processor arrays with a single CORDIC processor, resulting in a good compromise between speed and cost and furthermore providing great flexibility for the kinematic computations of different multibody systems. To achieve a high computational speed, the delays resulting from the sequential re-use of the single CORDIC processor, different hardware and software approaches will be described.

SEQUENTIAL WATER REUSE EFFECT ON STREAM SALINITY1

ABSTRACT: Sequential water reuse by various users, i.e., municipal, industrial, agricultural, is common practice in all river systems. In the arid and semiarid western United States where streams are not large and water demands are high relative to the virgin water supply, the practice causes a reduction in stream flow and an increase in stream salinity. This paper outlines a quick and easy application of the materials balance principle to approximate the effects of increasing the level of sequential reuse on residual stream flow and salinity.