Comparative study of the hydraulic, energy and agronomic performances of conventional and low pressure drip irrigation on citrus

In countries facing water scarcity, drip irrigation can raise crop productivity and save water compared to flood irrigation. In spite of its benefits, the adoption of drip irrigation is still low mainly due to the high cost of investment and the energy cost of operation. For this latter constraint, new types of drippers operating at low pressure are being tested. The present study aims to compare the performances of two types of drippers, represented by conventional drippers (CD) operating at nominal pressure of one bar and the new drippers (LP) operating at a pressure of 0.15 bars. The study was carried out in a citrus grove in Tadla, Morocco. Results showed that low pressure emitters reduced hydraulic energy per unit volume of water supplied by around 43% compared to conventional emitters, without significant reduction in water distribution uniformity. Low pressure drippers had uniformities of 80 to 92%, compared to 88 to 97% for conventional drippers. Citrus growth parameters, fruit yield and the fruit quality of the Maroc late variety were identical under the two types of drippers. Thus, low pressure emitters can be used as a substitute for conventional drippers which require higher energy. Key words: Drip irrigation, performance indicators, low pressure, citrus, Morocc

Field demonstration of a cost-optimized solar powered electrodialysis reversal desalination system in rural India

This study provides experimental validation of a previously published optimal design theory for photovoltaic (PV)-powered electrodialysis reversal (EDR) desalination systems. The prior work describes the co-optimization of PV and EDR subsystems, and flexible operation to accommodate daily and annual solar irradiance variability, significantly reducing water cost. This study presents the fabrication of a PV-EDR pilot system designed using the co-optimization theory and field testing results from the rural village of Chelluru, India. Testing in the field enabled observation and evaluation of real-world factors on system performance, resulting in updates to the previous theory to include unaccounted factors that affect costs, including: filling and draining of water tanks, salt and water accumulation in tanks from prior batches, unexpected energy losses due to locally purchased converters, and scaling in the ED stack. Therefore, water cost in the PV-EDR pilot system was updated from previous estimates based on field performance. The estimated capital cost and lifetime cost of the Chelluru system are 34% and 45% lower, respectively, than the corresponding costs if the PV-EDR system was designed using conventional design practice. The theory and experimental insights presented in this paper will enable desalination engineers to better design and optimize PV-EDR systems

Voltage- and flow-controlled electrodialysis batch operation : flexible and optimized brackish water desalination

Electrodialysis (ED) desalination has been demonstrated to be more energy-efficient, provide higher-recovery, and be lower-cost for producing drinking water from saline groundwater compared to reverse osmosis. These benefits of ED could translate into cost-effective, renewable-powered desalination solutions. However, the challenge of using a variable power source (e.g. solar) with traditional steady-state ED operation requires batteries to reshape the power source to match the desalination load; these batteries often contribute to a large fraction of the produced water cost. In this study, we propose a time-variant voltage- and flow-controlled ED operation that can enable highly flexible desalination from variable power sources, including renewables, with negligible batteries, potentially leading to reduced water costs compared to what existing technology can provide. A model-based controller is presented which varies applied ED stack voltage and pumping flow rate to match power consumption to a variable source while maximizing desalination rate throughout an ED batch. The utility of the controller was demonstrated with a pilot-scale system tested with brackish groundwater, which operated as expected under varying fixed power levels and a real solar irradiance profile. The pilot system achieved a production rate up to 45% higher than that of an equivalently sized traditional steady-state ED system

Locally affordable and scalable arsenic remediation for South Asia using ECAR

An estimated 60 million low income people in South Asia are affected by chronic exposure to naturally occurring arsenic in drinking water sources. Few household and community level technologies have proven to be sustainable and scalable. Electro-chemical Arsenic Remediation (ECAR) is a low cost, robust, highly effective and easily scalable technology that has been designed to fit within a scalable and sustainable business model. In this paper, we describe ECAR treatment results from arsenic-contaminated synthetic and real groundwater and field trials of 100L and 600L scale prototype systems operated at rural schools in West Bengal, India. We demonstrate robust and reliable arsenic removal, the low production of waste sludge and the potential for successful sludge stabilization in concrete. We estimate the operating costs and benefits of ECAR based on field results

Electrochemical arsenic remediation for rural Bangladesh

Arsenic in drinking water is a major public health problem threatening the lives of over 140 million people worldwide. In Bangladesh alone, up to 57 million people drink arsenic-laden water from shallow wells. ElectroChemical Arsenic Remediation (ECAR) overcomes many of the obstacles that plague current technologies and can be used affordably and on a small-scale, allowing for rapid dissemination into Bangladesh to address this arsenic crisis. In this work, ECAR was shown to effectively reduce 550 - 580 mu g=L arsenic (including both As[III] and As[V] in a 1:1 ratio) to below the WHO recommended maximum limit of 10 mu g=L in synthetic Bangladesh groundwater containing relevant concentrations of competitive ions such as phosphate, silicate, and bicarbonate. Arsenic removal capacity was found to be approximately constant within certain ranges of current density, but was found to change substantially between ranges. In order of decreasing arsenic removal capacity, the pattern was: 0.02 mA=cm2 > 0.07 mA=cm2 > 0.30 - 1.1 mA=cm2 > 5.0 - 100 mA=cm2. Current processing time was found to effect arsenic removal capacity independent of either charge density or current density. Electrode polarization studies showed no passivation of the electrode in the tested range (up to current density 10 mA=cm2) and ruled out oxygen evolution as the cause of decreasing removal capacity with current density. Simple settling and decantation required approximately 3 days to achieve arsenic removal comparable to filtration with a 0.1 mu m membrane. X-ray Absorption Spectroscopy (XAS) showed that (1) there is no significant difference in the arsenic removal mechanism of ECAR during operation at different current densities and (2) the arsenic removal mechanism in ECAR is consistent with arsenate adsorption onto a homogenous Fe(III)oxyhydroxide similar in structure to 2-line ferrihydrite. ECAR effectively reduced high arsenic concentrations (100 - 500 mu g=L) in real Bangladesh tube well water collected from three regions to below the WHO limit of 10 mu g=L. Prototype fabrication and field testing are currently underway

Electrochemical arsenic remediation for rural Bangladesh

Arsenic in drinking water is a major public health problem threatening the lives of over 140 million people worldwide. In Bangladesh alone, up to 57 million people drink arsenic-laden water from shallow wells. ElectroChemical Arsenic Remediation (ECAR) overcomes many of the obstacles that plague current technologies and can be used affordably and on a small-scale, allowing for rapid dissemination into Bangladesh to address this arsenic crisis. In this work, ECAR was shown to effectively reduce 550 - 580 mu g=L arsenic (including both As[III] and As[V] in a 1:1 ratio) to below the WHO recommended maximum limit of 10 mu g=L in synthetic Bangladesh groundwater containing relevant concentrations of competitive ions such as phosphate, silicate, and bicarbonate. Arsenic removal capacity was found to be approximately constant within certain ranges of current density, but was found to change substantially between ranges. In order of decreasing arsenic removal capacity, the pattern was: 0.02 mA=cm2 > 0.07 mA=cm2 > 0.30 - 1.1 mA=cm2 > 5.0 - 100 mA=cm2. Current processing time was found to effect arsenic removal capacity independent of either charge density or current density. Electrode polarization studies showed no passivation of the electrode in the tested range (up to current density 10 mA=cm2) and ruled out oxygen evolution as the cause of decreasing removal capacity with current density. Simple settling and decantation required approximately 3 days to achieve arsenic removal comparable to filtration with a 0.1 mu m membrane. X-ray Absorption Spectroscopy (XAS) showed that (1) there is no significant difference in the arsenic removal mechanism of ECAR during operation at different current densities and (2) the arsenic removal mechanism in ECAR is consistent with arsenate adsorption onto a homogenous Fe(III)oxyhydroxide similar in structure to 2-line ferrihydrite. ECAR effectively reduced high arsenic concentrations (100 - 500 mu g=L) in real Bangladesh tube well water collected from three regions to below the WHO limit of 10 mu g=L. Prototype fabrication and field testing are currently underway