Improving soil aquifer treatment efficiency using air injection into the subsurface

Agricultural Water Management, 2021

Water is a limiting factor for economic and social development in most arid and semi-arid regions on Earth. The deliberate recharge of depleted aquifer storage and later recovery, known as managed aquifer recharge (MAR), is an important tool for water management and sustainability. Increasing stresses on groundwater and subsequent overdrafts have sparked the development of several advanced MAR technologies, including soil aquifer treatment (SAT). SAT is a method that recharges wastewater effluent through intermittent percolation in infiltration basins. Another emerging MAR approach currently explored is the off-season flooding of agricultural lands, known as agricultural MAR, or Ag-MAR. Utilizing agricultural fields as temporary infiltration basins during periods of dormancy increases the availability of land resources for groundwater recharge, rather than designating land explicitly for MAR. As land resources for SAT become limited and the amount of available treated wastewater (TWW) increases, we propose the idea of agricultural SAT, or Ag-SAT, as a combination of SAT and Ag-MAR. This review paper aims to provide an in-depth look into the approach and application of Ag-MAR and the possibilities of integrating Ag-MAR with SAT. Ag-SAT comprises the off-season flooding of agricultural land using TWW for groundwater recharge and subsequent reuse. Ag-SAT could provide alternative infiltration sites for SAT where available surface area dedicated to infiltration is becoming a limiting factor. Additionally, the treated wastewater could potentially provide nutrients to agricultural fields during the flooding cycles. Potential advantages, disadvantages, and knowledge gaps related to Ag-SAT are presented and discussed.

2021

2016

Using a high efficiency venturi to inject air into water delivered through subsurface drip irrigation, commonly referred to as AirJection Irrigation, has been shown to result in increased yields for a variety of crops. Studies have also indicated that the technology can positively affect photosynthetic activity, soil respiration rates, and stomatal conductance. In the current study, we compared the relative quantity of a series of genes known to be involved in the nitrogen cycle for soils subjected to AirJection Irrigation for at least five years, with those that were not aerated. DNA was extracted using a PowerSoilTM kit and gene quantification was obtained via polymerase chain reaction. Distribution of the tested genes within the microbial populations was very distinct among the aerated and non-aerated soils. AirJection Irrigation had a clear selective impact on the distribution of the tested genes among the soil microbial population. While AirJection did not impact N fixation or ...

2021

This work aims to numerically study the desaturation process in a coarse-grained sandy deposit by means of air injection. It is well-known that the soil cyclic strength to liquefaction of a saturated, sandy deposit is positively affected by the presence of gas in the void space in either a dissolved or a free form. A numerical study is performed to investigate some of the factors affecting the desaturation advance and controlling the soil desaturation process by air injection. Among these factors are: a) soil-water characteristic curve and intrinsic permeability (hydraulic parameters), b) injection time, and c) standard approach to two injection wells placement. Only the standard mechanisms of biphasic flow are investigated (i.e., incompressible and isothermal biphasic flow in an isotropic homogeneous porous media with capillary effects).

2004

The concept of aerating the irrigation water increases the potential for the air to travel with water movement within the root zone. Physical, chemical, and biological soil characteristics that influence crop growth and yield depend on the relative proportions of the liquid and gas phases within the root zone. The findings of a pilot study conducted in 2000 at the Center for Irrigation Technology in which air was injected into the root zone of bell peppers via the subsurface drip irrigation (SDI) system justified follow-up fieldwork on larger plots approaching commercial scale. We present a review of current research aimed at evaluating the technical and economic feasibility of air injection into a SDI as a best management practice for fresh-market tomato, melon and bell pepper production. Generally, the incorporation of high efficiency venturi injectors in SDI systems increased root zone aeration and can add value to grower investments in SDI.

Subsurface drip irrigation (SDI) can substantially reduce the amount of irrigation water needed for corn production. However, corn yields need to be improved to offset the initial cost of drip installation. Air-injection is at least potentially applicable to the (SDI) system. However, the vertical stream of emitted air moving above the emitter outlet directly toward the surface creates a chimney effect, which should be avoided, and to ensure that there are adequate oxygen for root respiration. A field study was conducted in 2010 and 2011, to evaluate the effect of air-injection into the irrigation stream in SDI on the performance of corn. Experimental treatments were drip irrigation (DI), SDI, and SDI with air injection. The leaf area per plant with air injected was 1.477 and 1.0045 times greater in the aerated treatment than in DI and SDI, respectively. Grain filling was faster, and terminated earlier under air-injected drip system, than in DI. Root distribution, stem diameter, plant height and number of grains per plant were noticed to be higher under air injection than DI and SDI. Air injection had the highest water use efficiency (WUE) and irrigation water use efficiency (IWUE) in both growing seasons; with values of 1.442 and 1.096 in 2010 and 1.463 and 1.112 in 2011 for WUE and IWUE respectively. In comparison with DI and SDI, the air injection treatment achieved a significantly higher productivity through the two seasons. Yield increases due to air injection were 37.78% and 12.27% greater in 2010 and 38.46% and 12.5% in 2011 compared to the DI and SDI treatments, respectively. Data from this study indicate that corn yield can be improved under SDI if the drip water is aerated.

European Journal of Soil Science, 2003

Irrigation by surge flooding does not always wet the soils thoroughly, and we have investigated the reasons for this on an irrigated plot in northern Senegal by monitoring the water budget during a rice cropping season (100 days). The amount of water added during each irrigation event was measured, and evapotranspiration and infiltration were estimated with lysimeters and Muntz infiltration rings, respectively. At the same time, piezometric levels, neutron probe values and water tension data were recorded at two stations in the plot. These measurements showed unusual results: infiltration rate was less than 1 Â 10 À6 mm s À1 (less than 0.1 mm a day), there was a constant water deficit during the entire irrigation period, around 50 cm deep, and tensiometers at 40 cm reacted very slowly to water infiltration. The water fluxes in the vadose zone derived from these data showed clearly a discrepancy between fluxes calculated from hydraulic gradients and fluxes calculated from mass conservation. The hydraulic gradients suggested a zero flux plane at 40 cm below the surface, but the calculated values of the fluxes overestimated by several orders of magnitude the infiltration rates determined on the plot, whereas fluxes determined from mass conservation matched far better. These results show that air was entrapped between the shallow water table and the wetting front, and this inhibited water infiltration. Modelling water flow down the soil profile with a computer program for simulating one-dimensional water movement (Hydrus) confirmed that single-phase models cannot describe imbibition in this situation. Simple infiltration models based on a modified Green-Ampt equation accounting for air compression and air counterflow, however, fit experimental infiltration data much better. We demonstrated that where surge flooding is associated with a shallow water table, as in many large irrigation schemes, one must take into account the presence of air to quantify the flow of water into the soil.

The knowledge of soil and water movement in vadose zone is essential for a wide range of scientific and practical fields. One of the main but less studied media is the soil under the Undrained On-Site Treatment Systems (UOSTS). In situ monitoring is necessary to interpret most physical and hydric properties of soil and to determine the chemical composition of seepage water as a key aspect in sustainable management of soils. In this paper the design and instrumentation of different hydropedologic sensors in a real UOSTS, for the fist time in France, is presented. One of the main objectives is to extract the soil water samples in different stages of depth under the treatment system. Besides by performing the in situ hydraulic conductivity measurements, monitoring the recorded moisture and matrix potential data of the soil and determining soil physical properties in laboratory, we identify the existence of preferential flow in the heterogeneous soil of the site. As a main result, the executed pilot site is operational from March 2012. Soil water sample collecting and data recording are done regularly from this date. Also In situ permeameter tests give values of the conductivity which are averagely 135 times higher than values deduced from pedotransfer functions. This suggests that preferential flows occur within the soil via macropores shortcutting the matrix. Analysis of the recorded data shows the rapid reaction of the water table to the rainfall and the non-uniform reaction of the tensiometers according to their position. These results together suggest the existence of preferential pathway flux through the sand pack and the underlying soil.

Procedia Earth and Planetary Science, 2013

Artificial groundwater recharge of aquifers by percolating water through the unsaturated zone (UZ) is a technique to enhance the water quality for drinking, irrigation, and industrial water supplies. The performance of the UZ to purify the infiltrated water is based on both the chemical and hydrodynamic properties of the porous medium. The chemical and microbially-mediated redox-reactions involving the degradation of organic substances are the key phenomena controlling the efficiency of such a process, and allow developing filtrating and reactive zones beneath an artificial recharge system.

2020

The effluents from agriculture practices usually contain several contaminants creating an environmental concern to downgradient water bodies. The use of SAT systems to improve the effluents water quality, during the transport of infiltrated water through the unsaturated and saturated zones, can bring a solution for water reclamation, water reuse, and overall as a water resources management tool. The research was carried out under MARSOL project were SAT experiments were executed in a physical (sandbox) model. These experiments aimed to contribute solving the problem of removing rice field contaminants from water, using a soil-aquifer prototype basin to treat water prior to its discharge in Melides lagoon, Portugal. The sandbox model was divided into three sections to test the adsorption and biodegradation capacity of three soil profiles, two of them including soil mixtures of sand with vegetal compost with different layouts. In each section, two tracer experiments were performed wit...

Hydrology and Earth System Sciences Discussions

Sustainable irrigation with treated wastewater (TWW) is a promising solution for water scarcity in arid and semiarid regions. Soil aquifer treatment (SAT) provides a solution for both the need for tertiary treatment and seasonal storage of wastewater. Stresses over land use and the need to control the obtained water quality makes the optimization of SAT of great importance. This study looks into the influence of SAT systems' operational dynamics (i.e. flooding and drying periods) as well as some aspects of the inflow biochemical composition on their bio-geo-chemical state and the ultimate outflow quality. A series of four long-column experiments was conducted, aiming to examine the effect of different flooding/drying period ratios on dissolved oxygen (DO) concentrations, oxidation-reduction potential (ORP) and outflow composition. Flooding periods were kept constant at 60 minutes for all experiments while drying periods (DP) were 2.5 and 4 times the duration of the flooding periods. Our results show that the longer DP had a significant advantage over the shorter periods in terms of DO concentrations and ORP in the upper parts of the column as well as in the deeper parts, which indicates that larger volumes of the profile were able to maintain aerobic conditions. This advantage was evident also in outflow composition analyses that showed significantly lower concentrations of DOC, TKN and ammonium in the outflow for the longer DP. Comparing experimental ORP values in response to different DP to field measurements obtained in one of the SAT ponds of the SHAFDAN, Israel, we found that despite the major scale differences between the experimental 1D system and the field 3D conditions, ORP trends in response to changes in DP, qualitatively match. We conclude that longer DP not only ensure oxidizing conditions close to the surface, but also enlarge the active (oxidizing) region of the SAT. While those results still need to be verified in full scale, they suggest that SAT can be treated as a pseudo-reactor that to a great extent could be manipulated hydraulically to achieve the desired water quality while increasing the recharge volumes.

Journal of Hydrologic Engineering, 2008

The goal of this study was to investigate how extreme hydraulic loading influences hydraulic pathways, and thus failure potential, of two soil absorption systems. A grid of tensiometers and piezometers were installed beneath and adjacent to the absorption trenches, and water height was manipulated to simulate different hydraulic loadings. At both sites, measured soil matric potentials along the trench sidewalls increased toward zero as water height increased over time, indicating that water was preferentially flowing laterally above the biomat zones. Saturated hydraulic conductivity ͑K s ͒ of the soil and biomat, and other hydraulic parameters were calibrated using inverse modeling procedures in HYDRUS-2D. We found generally good agreement between measured and predicted matric potentials. The calibrated model was then used to predict fluxes through different infiltrative zones under typical and extreme hydraulic loads. Modeling indicated that the overall infiltration rates through the biomat and subbiomat zones fell within a relatively narrow range of 0.025-0.046 m / day at the two sites. Under extreme hydraulic loading to trenches, fluxes through the upper trench sidewalls ͑i.e., the exfiltration zone͒ were predicted to be substantially greater ͑i.e., 80% of total flux͒ than through the biomat zone. This confirms the conclusions made from field results, that a permeable exfiltration zone provides a critical buffer to surface surcharging during extreme trench loading. Conversely, the presence of a high sidewall biomat can reduce sidewall exfiltration of effluent, and therefore increase the likelihood of surface surcharging.

Revista Facultad de Ingeniería Universidad de Antioquia, 2017

Suelo parcialmente saturado, contenido inicial de agua, infiltración de agua, ensayos de laboratorio, infiltración unidimensional

2010

We tested intermittent aeration of the soil treatment area (STA) of onsite wastewater treatment systems (OWTS) for its ability to restore and maintain STA hydraulic flow and improve the water quality functions of conventional OWTS. Evaluation was conducted on hydraulically-failed conventional OWTS at three state-owned medical group homes in Washington County, RI, USA. Testing was conducted in two phases, with Phase I (before intermittent soil aeration (ISA)) comprising the first 6 months of the study, and Phase II (during ISA) the remaining 7 months. Intermittent soil aeration restored STA hydraulic function in all three systems despite a marked reduction in the STA total infiltrative surface. Soil pore water was collected from 30 and 90 cm below the STA during both phases and analyzed for standard wastewater parameters. Although the STA infiltrative surface was reduced-and the contaminant load per unit of area increasedafter installation of the ISA system, no differences were observed between phases in concentration of total N, NO 3 , total P, or dissolved organic carbon (DOC). Apparent removal rates-which do not account for dilution or differences in infiltrative area-for

Global water scarcity, one of the major threats to humanity, not only in arid or semiarid regions of the world but in overpopulated cities is rising. Population and rapid economic development growth have increase demands for water tremendously. Irrigation activities, mainly in many developing countries, consume most the world useable water as compare to domestic and industrial activities.