Abstract. Sustainable irrigation with treated wastewater (TWW) is a promising solution for water scarcity in arid and semi-arid 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 biogeochemical 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 min for all experiments while drying periods (DPs) were 2.5 and 4 times the duration of the flooding periods. Our results show that the longer DPs 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. DO concentrations in the deeper parts of the column stabilized at ∼3–4 mg L−1 for the longer DPs compared to ∼1–2 mg L−1 for the shorter DPs. This advantage was also evident in outflow composition that showed significantly lower concentrations of NH4+-N, dissolved organic carbon (DOC) and total Kjeldahl nitrogen (TKN) for the longer DPs (∼0.03, ∼1.65 and ∼0.62 mg L−1 respectively) compared to the shorter DPs (∼0.5, ∼4.4 and ∼3.8 mg L−1, respectively). Comparing experimental ORP values in response to different DPs to field measurements obtained in one of the SAT ponds of the SHAFDAN, Israel, we found that despite the large-scale differences between the experimental 1-D system and the field 3-D 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 at 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.
Physical models such as surface infiltration experiments in the lab and field are an approach to understand processes in the unsaturated soil zone. In the case of mapping processes influencing the operation of real-world managed aquifer recharge schemes they are helpful tools to determine interactions between processes in the unsaturated soil zone, and site-specific as well as operational parameters. However, the multitude of assumptions and scale-related limitations of downscale investigations often lead to over- or underestimations, rendering their results useless when translated to field-like conditions. Various real-world managed aquifer recharge operational scenarios were simulated in three physical models, a 1D-lab column, a rectangular shaped stainless steel 3D-lab infiltration tank and a rectangular shaped 3D-field unit, to understand the impact of the experimental set-up on the assessment of processes and to identify the experimental set-up which is most-suitable to describe these processes. Results indicate that water flow velocity, water saturation and oxygen consumption are often overestimated in 1D-column experiments due to sidewall effects and no existing lateral flow. For precise analysis of infiltration processes in general as well as during operation of managed aquifer recharge, 3D experiments are recommended due to their more realistic representation of flow processes.
Abstract. Sustainable irrigation with treated wastewater (TWW) is a promising solution for water scarcity in arid and semi-arid 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.
As an alternative to the use of tracers, easy-to-measure soil moisture dynamic parameters (e.g., water content) provide in situ estimates of the infiltration rate reduction state of a soil medium. For instance, managed aquifer recharge operations control the hydraulic state of their infiltration basins by measuring the infiltrated volume under constant head conditions. Instantaneous profile measurement systems can be used to manage the basins by determining the reduction of the infiltration rate over time. This study combines the empirical methods of Libardi, the self-developed water content and root mean square difference-based procedures and the trigger time method, to get a similar reproduction of tracer results from river water spreading basins. The methods based on water content showed a good fitting in comparison to the results obtained with the tracer experiment and represent a promising source for detecting changes in the flow impedance during infiltration events.
Water reclamation through the use of soil aquifer treatment (SAT) is a sustainable water management technique with high potential for application in many regions worldwide. However, the fate of contaminants of emerging concern (CECs) during the infiltration of treated wastewater during SAT is still a matter of research. This study investigates the removal capacity of 27 CECs during SAT by means of infiltration experiments into a 6 m soil column. Additionally, the influence of the hydraulic operation of SAT systems on the removal of CECs is investigated by changing the wetting and drying cycle lengths. Sixteen out of 27 CECs are efficiently removed during SAT under various operational modes, e.g., bezafibrate, diclofenac and valsartan. For six substances (4-methylbenzotriazole, amidotrizoic acid, benzotriazole, candesartan, hydrochlorothiazide and sulfamethoxazole), removal increased with longer drying times. Removal of amidotrizoic acid and benzotriazole increased by 85% when the drying cycle was changed from 100 to 444 min. For candesartan and hydrochlorothiazide, removal improved by 35%, and for 4-methylbenzotriazole and sulfamethoxazole, by 57% and 39%, respectively. Thus, enhanced aeration of the vadose soil zone through prolonged drying times can be a suitable technique to increase the removal of CECs during SAT.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.