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Soil aquifer treatment (SAT), as a gravity-based wastewater reuse process, is limited by oxygen availability to the microbial community in the soil. Using oxygen from enzymatic degradation of H2O2 to generate hyper-oxygen conditions can exceed solubility limitations associated with aeration, but little is known about the effect of hyper-oxygen conditions on the microbial community and the dominant bio-reactions. This study examined the impact of H2O2 addition on the community structure and process performance, along with SAT depth. Overall, two soil columns were incrementally fed synthetic secondary effluents to simulate infiltration through SAT. The experimental column received 14 mg/L hydrogen peroxide to double the level of natural oxygen available. The microbial kinetics of nitrifiers and heterotrophs were evaluated. We found that all of the H2O2 was degraded within the top 10 cm of the column, accompanied by a higher removal of COD (23 ± 0.25%) and ammonia (31 ± 3%) in comparison to the reference column. Higher nitrogen removal (23 ± 0.04%) was obtained for the whole process using H2O2. Analysis of nitrifiers indicated that ammonia-oxidizing bacteria were most influenced, obtaining higher concentration and abundance when exposed to H2O2. DNA sequencing analysis of samples exposed to H2O2 revealed significant community structure and diversity differences among heterotrophs. This study shows that not only aerobic, but also anoxic, microbial activity and process performance in a SAT system could be accelerated in existing infrastructure with H2O2, which could significantly decrease the associated environmental footprint. [ABSTRACT FROM AUTHOR]

To increase the opportunities and reduce the cost of indirect potable reuse, soil aquifer treatment (SAT) was evaluated at the City of Los Angeles' Donald C. Tillman Water Reclamation Plant (DCTWRP) in a 2.5‐year pilot study. Six soil columns were operated between February 2016 and November 2018 treating DCTWRP effluent. The goal was to reduce the dissolved organic carbon (DOC) in the effluent to lower concentrations in order to increase the allowable volumes for reclamation. An integrated part of the study was to evaluate the biodegradability of organics in different waters using biodegradable (BDOC) analyses. BDOC has been used in similar research in the past, and in this research, BDOC was an accurate predictor of column performance in removing organic carbon. The total organic carbon in tertiary DCTWRP effluent was reduced from 7 to 10 mg/L to 0.9 to 2.5 mg/L through a process train beginning with ozonation of the tertiary effluent, followed by biological activated carbon, and finally to the soil column effluents. Additional short‐term treatments including reverse osmosis, additional ozonation, and low‐pressure UV were also evaluated. The soil columns removed N‐nitrosodimethylamine to detection limits. Finally, results from SAT and BDOC were used to develop a kinetic model to predict biodegradation of organic matter of wastewater origin through a soil aquifer system. Practitioner points: Soil aquifer treatment is often used in indirect potable reuse projects to protect aquifers.Soil aquifer treatment was simulated in six pilot columns for 2.5 years.Columns were fed tertiary effluent from a nutrient‐removal type‐activated sludge plant.Effluent TOC was reduced from 10 mg/L to 0.9 to 2.5 mg/L, and nitrosodimethylamine (NDMA) was also removed.Biodegradable organic carbon analyses accurately predicted soil column performance in removing organic carbon. [ABSTRACT FROM AUTHOR]

• Time-dependent pathogen rate reduction in 3-D fracture network fractures. • 3-D E. coli transport simulation in networks of thousands of fractures. • Extended colloid filtration theory predicts pathogen BTC & 3-D plume in groundwater. • Model simulations were supported by field sampling and laboratory filtration tests. • Potential pathogen release to the bathing water is possible during floods. Microbial transport in fractured carbonate rock using enhanced solutions is a significant and neglected research topic in the literature. We propose an extended colloid filtration theory (CFT) combined with a particle-tracking following streamlines (PTFS) model for the rapid prediction of breakthrough curves (BTCs) and plumes of pathogens in three-dimensional (3-D) discrete fracture networks (DFNs). We adapted CFT in porous media to pathogen transport in fractures containing Terra Rossa (soil) deposits. As an example of the model capability, a simulation was used to predict the 3-D motion field and Escherichia coli count in groundwater originating from the Forcatella managed aquifer recharge (MAR) Facility (Brindisi, Italy) using a DFN composed of 3,900 fractures. In arid regions, MAR facilities are significant for sustaining basic human needs, such as freshwater supply for drinking and crop production. The Markov chain Monte Carlo (MCMC) technique was applied to E. coli counts in the collected water samples to increase data representativeness. The pathogen transport coefficients were further supported by batch filtration tests carried out in the CNR/IRSA Laboratory (Bari, Italy). The mean E. coli attachment rate coefficient of 0.15 × 10−8 m2 d–1 (sticking efficiency = 1.1 × 10−8 m) resulted in a 2.1 log 10 removal in 600 m of reclaimed water filtration. The simulation output visualized the E. coli 3-D pathways in groundwater and the positions of contaminated groundwater spring outflows on Forcatella Beach. The simulation results agreed with the mean MCMC output of E. coli concentrations in bathing water under unperturbed geochemical and environmental flow and transport conditions. However, results indicate that concentrations of pathogenic strains, parasites, and enteric viruses may enter the marine environment of MAR sites during flood periods. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Subsurface microorganisms must deal with quite extreme environmental conditions. The lack of light, oxygen, and potentially nutrients are the main environmental stresses faced by subsurface microbial communities. Likewise, environmental disruptions providing an unbalanced positive input of nutrients force microorganisms to adapt to varying conditions, visible in the changes in microbial community diversity. In order to test microbial community adaptation to environmental changes, we performed a study in a surface Managed Aquifer Recharge facility, consisting of a settlement basin (two-day residence time) and an infiltration pond. Data on groundwater hydrochemistry, soil texture, and microbial characterization was compiled from surface water, groundwater, and soil samples at two distinct recharge operation conditions. Multivariate statistics by means of Principal Component Analysis (PCA) was the technique used to map the relevant dimensionality reduced combinations of input variables that properly describe the system behavior. The methodology selected allows including variables of different nature and displaying very different range values. Strong differences in the microbial assemblage under recharge conditions were found, coupled to hydrochemistry and grain-size distribution variables. Also, some microbial groups displayed correlations with either carbon or nitrogen cycles, especially showing abundant populations of denitrifying bacteria in groundwater. A significant correlation was found between Methylotenera mobilis and the concentrations of NO 3 and SO 4 , and also between Vogesella indigofera and the presence of DOC in the infiltrating water. Also, microbial communities present at the bottom of the pond correlated with representative descriptors of soil grain size distribution. Graphical abstract Image 1 Highlights • Environmental variables affect microbial phylotypes presence in recharge systems. • PCA allows identifying most relevant environmental variables. • Microbial signature in porewater changes with infiltration operations. • Grain-size distribution drives microbial population behavior in soils. • Infiltration ponds have an impact on biomediated carbon and nitrogen cycles. [ABSTRACT FROM AUTHOR]

Abstract Soil columns simulating soil aquifer treatment (SAT), fed with synthetic secondary effluent by intermittent infiltration of flooding/drying cycles, were characterized for nitrogen and organic carbon removal, and microbial ecology and biokinetics. The columns differed in the concentration ratio of chemical oxygen demand (COD) to the summed NH 4 +, NO 2 − and organic nitrogen—2 (C/N2) or 5 (C/N5). Chemical profiles along the column demonstrated a preference for COD oxidation over nitrification and coupled denitrification, with higher nitrogen loss (57% vs. 16%) in the C/N5 column. Unexpectedly, significant dominance of the genus Nitrospira over the genus Nitrobacter and ammonia-oxidizing bacteria (AOB) was strongly correlated at column depths where NH 4 + removal occurred. Moreover, the Nitrospira profile had the strongest correlation to the profile of NH 4 + (positive) and NO 3 − (negative), strongly indicating complete ammonia oxidation. 16S sequencing analysis of the topsoil in C/N2 vs. C/N5 columns revealed double the abundance of microbial aerobic potential (64% vs. 32%) vs. one-third the denitrification potential (13% vs. 31%). The concentrations and degradability levels of organic carbon were the most influential parameters shaping community structure. Niche differentiation within the biofilm attached to the soil is suggested to have an important role in the process's anoxic activity and nitrogen removal. Graphical abstract Image 1 Highlights • Higher C/N ratio in the feed resulted in significantly higher N loss. • The genus Nitrospira showed preponderance over the genus Nitrobacter and AOB. • Nitrospira correlated to ammonia removal show complete ammonia oxidation activity. • At top high C/N column microbial community reflected potential for denitrification. • Niche differentiation within the biofilm is significant in anoxic activity at SAT. [ABSTRACT FROM AUTHOR]

Managed aquifer recharge (MAR) systems can be operated intermittently through wetting-drying cycles to simultaneously improve the water supply and quality. Although MAR can naturally attenuate considerable amounts of nitrogen, the dynamic processes and control mechanisms of nitrogen removal by intermittent MAR remain unclear. This study was conducted in laboratory sandy columns and lasted for 23 d, including four wetting periods and three drying periods. The hydraulic conductivity, oxidation reduction potential (ORP), and leaching concentrations of ammonia nitrogen and nitrate nitrogen of MAR systems were intensively measured to test the hypothesis that hydrological and biogeochemical controls play an essential role in regulating nitrogen dynamics at different stages of wetting-drying cycles. Intermittent MAR functioned as a sink for nitrogen while providing a carbon source to support nitrogen transformations; however, it occasionally became a source of nitrogen under intense flushes of preferential flow. Nitrogen dynamics were primarily controlled by hydrological processes in the initial wetting phase and were further regulated by biogeochemical processes during the subsequent wetting period, supporting our hypothesis. We also observed that a saturated zone could mediate nitrogen dynamics by creating anaerobic conditions for denitrification and buffering the flush effect of preferential flow. The drying duration can also affect the occurrence of preferential flow and nitrogen transformations, which should be balanced when determining the optimal drying duration for intermittent MAR systems. • Intermittent managed aquifer recharge overall functioned as a sink for nitrogen. • Nitrogen dynamics and their controls vary with different stages of recharging. • Saturated zone can create an anerobic condition for denitrification. • Drying duration can mediate control mechanisms and thus nitrogen dynamics. [ABSTRACT FROM AUTHOR]

Abstract Two column pairs filled with 3.05-m of a sandy soil from the Upper San Gabriel Valley were operated for a period of four and ½ years on municipal effluent from the San Jose Creek Water Reclamation Plant operated by the Sanitation Districts of Los Angeles County (LACSD). One column pair was fed filtered, chlorinated effluent (tertiary effluent) for the entire period. The other pair was fed ozonated secondary effluent for 8-mo, ozonated secondary effluent filtered through biological activated carbon (O 3 /BAC) for 7-mo and tertiary effluent for 38-mo. Each column pair was operated in series, where the first column was operated for a shorter residence time and the second column for a longer residence time. Residence times tested were 5-d, 28-d, 30-d, 58-d, 60-d, 150-d and 180-d. For the last 38-mo, both pairs of columns had a residence time of 30-d in the first column and the total residence time of the two pairs was 150 and 180-d, respectively. Testing showed both of these pairs had the same long-term performance. The column pairs with a 150 to 180-d residence time, which were both fed tertiary effluent, reached an effluent total organic carbon (TOC) of 1.8 mg/L. Column pairs with a 28 to 30-d residence time, which were fed tertiary, ozonated, and O 3 /BAC effluent, reached effluent TOCs of 2.3, 2.1 and 1.8 mg/L respectively. In the latter, some TOC removal was shifted from the soil columns to the BAC. During the last 38 months of testing, using tertiary effluent as the source water, a series of sampling events was performed throughout the soil column system for N -nitrosodimethylamine (NDMA) and chemicals of emerging concern (CECs). NDMA was substantially reduced in all the columns, with a median value of 3 ng/L after 30-d and <2 ng/L after both 150 and 180-d. Twenty-one CECs were found in the majority of tertiary effluent samples, twelve of which were attenuated by the soil columns and the remaining were not. Chemicals found to be recalcitrant were 4-nonylphenol, acesulfame-k, carbamazepine, lidocaine, primidone, simazine, sucralose, sulfamethoxazole, and TCEP. Using excitation-emission matrix (EEM) techniques, soluble microbial products (SMP) peak characteristic of effluent organic matter (EfOM) is nearly eliminated after a 30-d hydraulic retention time (HRT) and completely eliminated in the 150/180-d samples. The intensity of the other peaks is significantly reduced as well, resulting in an EEM much like that of natural groundwater. Graphical abstract Image 1 Highlights • Soil columns fed tertiary effluent reduced the TOC 67% with a 150-day HRT. • NDMA was attenuated through soil columns by more than 99%. • Soil column treatment attenuated 12 of the 21 CECs found in tertiary effluent. • Soil columns were operated over four and ½ year period with tertiary effluent. [ABSTRACT FROM AUTHOR]

The long term behavior of total nitrogen and its components was investigated in a soil aquifer treatment system of the Dan Region Reclamation Project (Shafdan), Tel-Aviv, Israel. Use is made of the previous 40 years' secondary data for the main nitrogen components (ammonium, nitrate and organic nitrogen) in recharged effluent and observation wells located inside an infiltration basin. The wells were drilled to 106 and 67 m, both in a similar position within the basin. The transport characteristics of each nitrogen component were evaluated based on chloride travel-time, calculated by a cross-correlation between its concentration in the recharge effluent and the observation wells. Changes in the source of recharge effluent, wastewater treatment technology and recharge regime were found to be the main factors affecting turnover in total nitrogen and its components. During aerobic operation of the infiltration basins, most organic nitrogen and ammonium will be converted to nitrate. Total nitrogen removal in the upper part of the aquifer was found to be 47–63% by denitrification and absorption, and overall removal, including the lower part of the aquifer, was 49–83%. To maintain the aerobic operation of the infiltration fields, the total nitrogen load should remain below 10 mg/L. Above this limit, ammonium and organic nitrogen will be displaced into the aquifer. [ABSTRACT FROM AUTHOR]

Soil aquifer treatment (SAT) is an effective natural and economically feasible tertiary treatment for wastewater reuse. An innovative hybrid process based on biofiltration, ozonation and short SAT (sSAT, with ~22 days retention time) was demonstrated in a 6 m3/hr pilot system to remove emerging trace organic compounds (TrOCs), organic matter and control Mn2+dissolution in reclaimed water. The biofiltration stage was proposed for nitrification of ammonia as well as removal of dissolved and particulate organic matter (DOM and POM), to enable efficient ozonation of secondary effluents. The pilot system was operated in two modes, where samples were periodically taken from all pilot stages to observe changes in product water quality. At first (Mode 1), biofiltered effluents were infiltrated through sSAT (i.e., no ozonation prior infiltration). During this operation, ammonia, nitrite and phosphate were completely removed, and pathogens were highly reduced. In addition, all measured TrOCs were effectively removed after sSAT, besides the persistent TrOCs Carbamazepine (CBZ) and Iodine-organic contrast media Iopamidol (IPDL). In Mode 2, biofiltered and ozonated (1.0–1.2 mg ozone/mg DOC) effluents were infiltrated through sSAT. In the final reclaimed product, values of DOC, UVA and Mn2+were reduced to 0.8 mg/L, 2.2 L/m, and 29–35 µg/L, respectively. Furthermore, ammonia and nitrite were not detected in the product, and good bacterial quality was obtained. Following 56–75 days of operation at Mode 2, all TrOCs were reduced down to <100 ng/L. The delay in the effect of the pretreatment stages on TrOCs removal by sSAT (>56 days instead of ~22 days) could be explained by their displacement retardation in the upper soil layers of the pilot SAT (0–25 cm). In-depth sampling in the observation well after 111 days at Mode 2 showed homogeneity along the overall perforated section of the well (from −14 to −26 m) with 0.7–0.9 mg/L DOC, 2.1–2.2 1/m UVA and <10 ng/L CBZ. This result proved that the ozonated water completely covered the area around the observation well and positively affected the quality of the reclaimed water. [ABSTRACT FROM PUBLISHER]

Wastewater reclamation is becoming an important alternative for sustainable water resources management and building climate change resiliency in many regions around the world. This research investigated the polishing of secondary effluents and combined sewer overflows (CSOs) by a laboratory-scale soil aquifer treatment considering local soils and wastewater characteristics of southwestern Ontario. Results show that high permeability soils of southwestern Ontario, have the ability to polish secondary effluents in terms of dissolved organic carbon, Escherichia coli, and total coliforms. Regarding the simulated CSOs, low to moderate improvements of wastewater quality were observed. Denitrification of secondary effluents improved significantly by the addition of readily available organic matter, which supports the importance of protecting recharge wetlands for groundwater quality protection. Soil aquifer treatment in southwestern Ontario is a feasible alternative for the recharge of non-potable and potable aquifers with secondary effluents. However, for potable aquifers further treatment of wastewater effluents may be required. [ABSTRACT FROM AUTHOR]

Soil aquifer treatment (SAT) is a managed aquifer recharge system in which the quality of the feed water (stormwater or wastewater treatment plant effluent) is further improved during soil passage. This paper provides an overview of SAT systems for wastewater treatment and reuse, and summarises design, removal efficiencies and pre-and post-treatment options as well as cost aspects of SAT using infiltration basins. SAT is an environment-friendly and robust multi-contaminant removal system which is effective in removing pathogens, nitrogen, bulk organic matter and the majority of organic micropollutants. The contaminant removal efficiency of SAT system, however, depends on several factors including source water quality, local hydrogeological conditions and process conditions applied. The performance of SAT system can be further improved by proper site selection and appropriate design of its components including pre- and post-treatment. SAT serves as an environmental and psychological barrier for water reuse applications. It is equally attractive for developed as well as developing countries and flexible enough to allow adaptation to local requirements by combining it with conventional (above the ground) natural or engineered water and wastewater treatment technologies. [ABSTRACT FROM AUTHOR]

Erythromycin (ERY), a widely used antibiotic, has recently been detected in municipal secondary effluents and poses serious threats to human health during wastewater reusing. In this study, the removal, fate, and degradation pathway of ERY in secondary effluent during soil aquifer treatment was evaluated via laboratory-scale SAT tests. Up to a 92.9% reduction of ERY in synthetic secondary effluent was observed in 1.0 m depth column system, which decreased to 64.7% when recharged with wastewater treatment plant secondary effluent. XRD-fractionation results demonstrated that the transphilic acid and hydrophobic acid fractions in secondary effluent compete for the adsorption sites of the packed soil and lead to a declined ERY removal. Moreover, aerobic biodegradation was the predominant role for ERY removal, contributing more than 60% reduction of ERY when recharged with synthetic secondary effluent. Destruction of 14-member macrocyclic lactone ring and breakdown of two cyclic sugars ( l -cladinose and d -desosamine) were main removal pathways for ERY degradation, and produced six new intermediates. [ABSTRACT FROM AUTHOR]

Soil aquifer treatment (SAT) systems rely on extensive physical and biogeochemical processes in the vadose zone and aquifer for water quality improvement. In this study, the distribution, quantitative changes, as well as the speciation characteristics of heavy metals in different depth of soils of a two-year operated lab-scale SAT was explored. A majority of the heavy metals in the recharged secondary effluent were efficiently trapped by the steady-state operated SAT (removal efficiency ranged from 74.7% to 98.2%). Thus, significant accumulations of 31.7% for Cd, 15.9% for Cu, 15.3% for Zn and 8.6% for Cr were observed for the top soil after 730 d operation, leading to the concentration (in μg g −1 ) of those four heavy metals of the packed soil increased from 0.51, 46.7, 61.0 and 35.7 to 0.66, 54.2, 70.4 and 38.8, respectively. By contrast, the accumulation of Mn and Pb were quite low. The residual species were the predominant fraction of the six heavy metals (ranged for 59.8–82.4%), followed by oxidisable species. Although the Zn, Cr, Cd, Cu and Mn were efficiently bounded onto the oxide components within the soil, the percentage of the labile metal fractions (water-, acid-exchangeable and reducible metal fractions) exhibited a slight increasing after 2 Y operation. Significantly heavy metals accumulation and slightly decreasing of the proportion of the stable fractions indicated a potentially higher environmental hazard for those six heavy metals after long-term SAT operation (especially for Cu, Zn and Cd). Finally, a linear relationship between the accumulation rate of metal species and the variation of soil organic carbon concentration and water extractable organic carbon was demonstrated. [ABSTRACT FROM AUTHOR]

The secondary effluent fromwastewater treatment plants was reused for industrial cooling water after pre-treatment with a laboratory-scale soil aquifer treatment (SAT) system. Up to a 95.3% removal efficiency for suspended solids (SS), 51.4% for chemical oxygen demand (COD), 32.1% for Cl- and 30.0% SO4 2-were observed for the recharged secondary effluent after the SAT operation, which is essential for controlling scaling and corrosion during the cooling process. As compared to the secondary effluent, the reuse of the 1.5 m depth SAT effluent decreased the corrosion by 75.0%, in addition to a 55.1% decline of the scales/biofouling formation (with a compacted structure). The experimental results can satisfy the Chinese criterion of Design Criterion of the Industrial Circulating Cooling Water Treatment (GB 50050-95), and was more efficient than tertiary effluent which coagulated with ferric chloride. In addition, chemical structure of the scales/biofouling obtained from the cooling system was analyzed. [ABSTRACT FROM AUTHOR]

Soil Aquifer Treatment (SAT) is used to increase groundwater resources and enhance the water quality of wastewater treatment plant (WWTP) effluents. The resulting water quality needs to be assessed. In this study, we investigate attenuation pathways of nitrogen (N) compounds (predominantly NH 4 +) from a secondary treatment effluent in pilot SAT systems: both a conventional one (SAT-Control system) and one operating with a permeable reactive barrier (PRB) to provide extra dissolved organic carbon to the recharged water. The goal is to evaluate the effectiveness of the two systems regarding N compounds by means of chemical and isotopic tools. Water chemistry (NO 3 −, NH 4 +, Non-Purgeable Dissolved Organic Carbon (NPDOC), and O 2) and isotopic composition of NO 3 − (ẟ 15N–NO 3 - and ẟ 18O–NO 3 -) and NH 4 + (ẟ 15N–NH 4 +) were monitored in the inflow and at three different sections and depths along the aquifer flow path. Chemical and isotopic results suggest that coupled nitrification-denitrification were the principal mechanisms responsible for the migration and distribution of inorganic N in the systems and that nitrification rate decreased with depth. At the end of the study period, 66% of the total N in the solution was removed in the SAT-PRB system and 69% in the SAT-Control system, measured at the outlet of the systems. The residual N in solution in the SAT-PRB system had an approximately equal proportion of N–NH 4 + and N–NO 3 - while in the SAT-Control system, the residual N in solution was primarily N–NO 3 -. Isotopic data also confirmed complete NO 3 − degradation in the systems from July to September with the possibility of mixing newly generated NO 3 − with the residual NO 3 − in the substrate pool. • We applied isotopic tools in pilot soil aquifer treatment systems to evaluate the N cycle. • Simultaneous nitrification-denitrification was the principal N attenuation pathway. • Nitrification occurred at the top of the system due to vertical diffusion of O 2. • Denitrification was enhanced by the increase of dissolved organic carbon and temperatures. • Limitations in using isotopic tools to quantify multiple reactions were observed. [ABSTRACT FROM AUTHOR]

The reuse of treated wastewater for irrigation and groundwater recharge can counteract water scarcity and reduce pollution of surface waters, but assessing its environmental risk should likewise consider effects associated to the soil. The present study therefore aimed at determining the impact of wastewater irrigation on the habitat quality of water after soil passage and of soil after percolation by applying bioassays and chemical analysis. Lab-scale columns of four different soils encompassing standard European soil and three field soils of varying characteristics and pre-contamination were continuously percolated with treated wastewater to simulate long-term irrigation. Wastewater and its percolates were tested for immobilization of Daphnia magna and growth inhibition of green algae ( Pseudokirchneriella subcapitata ) and water lentils ( Lemna minor ). The observed phytotoxicity of the treated wastewater was mostly reduced by soil passage, but in some percolates also increased for green algae. Chemical analysis covering an extensive set of wastewater-born organic pollutants demonstrated that many of them were considerably reduced by soil passage, particularly through peaty soils. Taken together, these results indicated that wastewater-born phytotoxic substances may be removed by soil passage, while existing soil pollutants (e.g. metals) may leach and impair percolate quality. Soils with and without wastewater irrigation were tested for growth of plants ( Avena sativa , Brassica napus ) and soil bacteria ( Arthrobacter globiformis ) and reproduction of collembolans ( Folsomia candida ) and oligochaetes ( Enchytraeus crypticus , Eisenia fetida ). The habitat quality of the standard and two field soils appeared to be deteriorated by wastewater percolation for at least one organism (enchytraeids, plants or bacteria), while for two pre-contaminated field soils it also was improved (for plants and/or enchytraeids). Wastewater percolation did not seem to raise soil concentrations of classical organic pollutants and priority substances, while a significant retention was found for zinc and several organic micropollutants, particularly in the peaty soils, thus matching these soils' observed higher removal efficiency. Overall, our results demonstrate that benefits of wastewater irrigation can come with the cost of deteriorating soil habitat quality and depend on the respective soil and considered test organism. The approach employed here represents a feasible tool to assess these integrated effects at lab-scale while being predictive for scenarios at field-scale. [ABSTRACT FROM AUTHOR]

Soil aquifer treatment is widely applied to improve the quality of treated wastewater in its reuse as alternative source of water. To gain a deeper understanding of the fate of thereby introduced organic micropollutants, the attenuation of 28 compounds was investigated in column experiments using two large scale column systems in duplicate. The influence of increasing proportions of solid organic matter (0.04% vs. 0.17%) and decreasing redox potentials (denitrification vs. iron reduction) was studied by introducing a layer of compost. Secondary effluent from a wastewater treatment plant was used as water matrix for simulating soil aquifer treatment. For neutral and anionic compounds, sorption generally increases with the compound hydrophobicity and the solid organic matter in the column system. Organic cations showed the highest attenuation. Among them, breakthroughs were only registered for the cationic beta-blockers atenolol and metoprolol. An enhanced degradation in the columns with organic infiltration layer was observed for the majority of the compounds, suggesting an improved degradation for higher levels of biodegradable dissolved organic carbon. Solely the degradation of sulfamethoxazole could clearly be attributed to redox effects (when reaching iron reducing conditions). The study provides valuable insights into the attenuation potential for a wide spectrum of organic micropollutants under realistic soil aquifer treatment conditions. Furthermore, the introduction of the compost layer generally showed positive effects on the removal of compounds preferentially degraded under reducing conditions and also increases the residence times in the soil aquifer treatment system via sorption. [ABSTRACT FROM AUTHOR]

A permeable reactive layer was installed at the floor of an infiltration basin. The reactive layer comprised 1) vegetable compost to provide a sorption surface for neutral organic compounds and to release easily degradable organic matter, thus generating a sequence of redox states, and 2) minor amounts of clay and iron oxide to increase sorption of cationic and anionic species, respectively. Field application of this design was successful in generating denitrification, and manganese-, and iron-reducing conditions beneath the basin. This, together with the increase in types of sorption sites, may explain the improved removal of three of the four selected pharmaceuticals compared with their behavior prior to installation of the layer. After installation of the reactive layer, atenolol concentrations were below the detection limits in the vadose zone. Moreover, concentrations of gemfibrozil and cetirizine were reduced to 20% and 40% of their initial concentrations, respectively, after 200 h of residence time. In contrast, prior to installation of the reactive layer, the concentrations of these three pharmaceuticals in both the vadose zone and the aquifer were more than 60% of the initial concentration. Carbamazepine exhibited recalcitrant behavior both prior to and after the reactive barrier installation. [ABSTRACT FROM AUTHOR]

We investigated changes in element content and distribution in soil profiles in a study designed to monitor the geochemical changes accruing in soil due to long-term secondary effluent recharge, and its impact on the sustainability of the Soil Aquifer Treatment (SAT) system. Since the initial elemental contents of the soils at the studied site were not available, we reconstructed them using scandium (Sc) as a conservative tracer. By using this approach, we were able to produce a mass-balance for 18 elements and evaluate the geochemical changes resulting from 19 years of effluent recharge. This approach also provides a better understanding of the role of soils as an adsorption filter for the heavy metals contained in the effluent. The soil mass balance suggests 19 years of effluent recharge cause for a significant enrichment in Cu, Cr, Ni, Zn, Mg, K, Na, S and P contents in the upper 4 m of the soil profile. Combining the elements lode record during the 19 years suggest that Cr, Ni, and P inputs may not reach the groundwater (20 m deep), whereas the other elements may. Conversely, we found that 58, 60, and 30% of the initial content of Mn, Ca and Co respectively leached from the upper 2-m of the soil profile. These high percentages of Mn and Ca depletion from the basin soils may reduce the soil's ability to buffer decreases in redox potential pe and pH, respectively, which could initiate a reduction in the soil's holding capacity for heavy metals. [ABSTRACT FROM AUTHOR]

Abstract: In this study, changes of microbial substrate metabolic patterns by BIOLOG assay were discussed through a sequential wastewater reuse process, which includes activated sludge and treated effluent in wastewater treatment plant and soil aquifer treatment (SAT), especially focussing on the surface sand layer in conjunction with the vadose zone, concerning sand depth. A SAT pilot-scale reactor, in which the height of packed sand was 237 cm (vadose zone: 17 cm and saturated zone 220 cm), was operated and fed continuously by discharged anaerobic–anoxic–oxic (A2O) treated water. Continuous water quality measurements over a period of 10 months indicated that the treatment performance of the reactor, such as 83.2% dissolved organic carbon removal, appeared to be stable. Core sampling was conducted for the surface sand to a 30 cm depth, and the sample was divided into six 5 cm sections. Microbial activities, as evaluated by fluorescein diacetate, sharply decreased with increasing distance from the surface of the 30 cm core sample, which included significant decreases only 5 cm from the top surface. A similar microbial metabolic pattern containing a high degree of carbohydrates was obtained among the activated sludge, A2O treated water (influent to the SAT reactor) and the 0–5 cm layer of sand. Meanwhile, the 10–30 cm sand core layers showed dramatically different metabolic patterns containing a high degree of carboxylic acid and esters, and it is possible that the metabolic pattern exhibited by the 5–10 cm layer is at a midpoint of the changing pattern. This suggests that the removal of different organic compounds by biodegradation would be expected to occur in the activated sludge and in the SAT sand layers immediately below 5 cm from the top surface. It is possible that changes in the composition of the organic matter and/or transit of the limiting factor for microbial activities from carbon to phosphorus might have contributed to the observed dramatic changes in SAT metabolic patterns. [Copyright &y& Elsevier]

The potential of enhancing water uses using soil aquifer treatment (SAT) is an interesting alternative for tropical regions, limited only by lack of knowledge on its performance in local conditions and the feasibility of adapting this technology. A SAT pilot study was conducted to analyze the phenomena associated with the transformation of organic matter (OM) from domestic wastewater. Chemically enhanced primary effluent collected at the Cañaveralejo wastewater treatment plant (Cali, Colombia) was used to feed pilot-scale SAT units at a rate of 1.25 m.d-1. Dissolved organic carbon (DOC) removal in a 5.0 m length and 0.1 m diameter column packed with sand was 64.4%, while a similar column packed with a Mollisol soil from Valle del Cauca region yielded 56.2%. Oxygen availability was an important factor in OM degradation, given that the sand column degraded OM aerobically and the soil column degraded OM under oxic as well as anoxic conditions. SAT acted as a reliable barrier for DOC in tropical conditions. Nevertheless, operational problems such as clogging indicated that probably Mollisol soil may not be the suitable for SAT or that this particular effluent requires further pre-treatment before SAT. [ABSTRACT FROM AUTHOR]

Highlights: [•] Intermittent application of primary effluent in managed aquifer recharge was simulated. [•] Two hydraulic loading rates were used and the length of drying period was varied. [•] Removal of bulk organic matter and suspended solids was independent of drying period. [•] Significant removal of nitrogen and indicator microorganisms was observed with drying length. [ABSTRACT FROM AUTHOR]

Abstract: Ozonation is known as an efficient treatment to reduce the concentration of many trace organic compounds from WWTP effluents, but the formation of unknown and possibly persistent and toxic transformation products has to be considered. In this paper tertiary treatment of wastewater by the combination of ozone and soil aquifer treatment was investigated with respect to the removal of the antiepileptic drug carbamazepine (CBZ, 10 μg/L) and its transformation products. Batch tests and pilot experiments confirmed efficient removal of carbamazepine from secondary effluent by ozone. With typical ozone consumption of 0.7 mg O3/mg DOC0, approx. 50% of the transformed CBZ was detected as its primary product 1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one (BQM). Structure proposals and a formation pathway were elaborated for a total of 13 ozonation products of CBZ. In subsequent biological treatment BQM turned out to be more effectively biodegraded than CBZ. Its aldehyde group was quickly oxidized to a carboxylic acid (BaQM), which was removed in sand column experiments. Most of the minor ozonation products of CBZ persisted in sand column experiments with residence times of 5–6 days. Non-target screening of column effluent revealed no formation of persistent biotransformation products. [Copyright &y& Elsevier]

Removal of municipal effluent-derived dissolved organic matter (DOM) of various apparent molecular weights (AMWs) was compared among ozonation, nanofiltration, ultrafiltration, and magnetic ion exchange (MIEX) resin coagulation. These advanced technologies were applied as pretreatments for soil aquifer treatment (SAT). Soil aquifer treatment alone removed 20 to 30% of dissolved organic carbon (DOC) and UV254. Soil aquifer treatment effectively removed 100% and 76% of DOM with AMWs of 21.3 to 31.6 kDa and 0.4 to 1.0 kDa, respectively. With pretreatments of ozonation, MIEX resin coagulation and nanofiltration, substantially higher removals (40 to 75%) were achieved for DOC and UV254. The removal efficiency of the entire system decreased as nanofiltration-SAT > ozonation-SAT > MIEX-SAT > ultrafiltration-SAT, which is positively related to the removal efficiency for medium AMW (1.8 to 7.7 kDa, mainly humic substances) DOM during pretreatments. Different pretreatments should, therefore, be chosen in accordance with the water quality of feed water and water products and SAT removal efficiency. [ABSTRACT FROM AUTHOR]

To clarify the removal trends of typical pollutants in recharged water samples during soil aquifer treatment (SAT), especially the recharging performances in the funnel areas of arid regions, the Zibo-Weifang funnel area of China was selected as an example where the effects of dry-wet ratio (DWR, the ratio of the dry period to irrigation period), wet period duration (WPD, duration of one irrigation period), irrigation side length (ISL) and irrigation depth (ID) on the 50-year SAT performance were simulated using HYDRUS-2D. Experimental results revealed that the operational parameters of the DWR, WPD, ISL and ID exhibited significant effects on the bulk removal of chemical oxygen demand (COD), nitrate (N O 3 −), ammonium (N H 4 +), total phosphorus (TP) and hexavalent chromium (C r 6 +). Eventually, the optimal conditions with a DWR of 3, WPD of 7 d, ISL of 100 m, and ID of 200 cm were selected for the SAT based on the simulations, and irrigation loads as high as of 84.12 m/yr were obtained. During the 50-year irrigation simulation, as much as 256 Mm3/yr of new water would be recharged into the Shandong Plain, which would be accompanied by the effective removal of COD, N H 4 + , TP and C r 6 + . In contrast, the N O 3 − concentrations within the obtained SAT effluent (50 m depth) were higher than those of the influent, which were closely related to the insufficient carbon sources in the deep soil and poor soil adsorption capacity. Thus, a more stringent threshold value for the nitrate reinjection concentration (e.g., 12 mg/L) was proposed. In addition, the pollutants, N O 3 − , N H 4 + , TP and C r 6 + all exhibited a penetration potential and posed potential pollution threats, especially under higher irrigation loads. Therefore, appropriate pretreatment measures should be strongly considered for the practical operation of SAT systems. [Display omitted] • Simulated the efficiency of SAT in different operating conditions at actual scale. • N O 3 − concentration increased after SAT under different operating conditions. • The concentration of N O 3 − in influent should be limited to less than 12 mg/L. • Significant correlation existed in the removal of N H 4 + with COD and TP (R 2 >0.8). • The penetration risk exhibited the following trend: N O 3 − ≫ C r 6 + N H 4 + >TP. [ABSTRACT FROM AUTHOR]

The effect of hydraulic loading rate (HLR) and media type on the removal of bulk organic matter and nitrogen from primary effluent during soil aquifer treatment was investigated by conducting laboratory-scale soil column studies. Two soil columns packed with silica sand were operated at HLRs of 0.625 and 1.25 m/d, while a third column was packed with dune filtering material and operated at HLR of 1.25 m/d. Bulk organic matter was effectively removed by 47.5±1.2% and 45.1± 1.2% in silica sand columns operated at 0.625 and 1.25 m/d, respectively and 57.3± 7.6% in dune filtering material column operated at 1.25 m/d. Ammonium-nitrogen reduction of 74.5±18.0% was achieved at 0.625 m/d compared to 39.1±4.3% at 1.25 m/d in silica sand columns, whereas 49.2± 5.2% ammonium-nitrogen reduction was attained at 1.25 m/d in the dune filtering material column. Ammonium-nitrogen reduction in the first 3 m was assumed to be dominated by nitrification process evidenced by corresponding increase in nitrate. Part of the ammonium-nitrogen was adsorbed onto the media, which was observed at higher rates between 3 and 5 m in silica sand column operated at HLR of 0.625 m/d and dune filtering material column operated at 1.25 m/d compared to 1.25 m/d silica. [ABSTRACT FROM AUTHOR]

There is growing concern over the health and environmental effects posed by endocrine disrupting chemicals (EDCs) in the aquatic environment. The removal of three potent EDCs including estrone (E1), 17β-estradiol (E2), and 17α -ethinylestradiol (EE2) in a wastewater using soil columns was investigated. E2 was the most easily removed estrogen, while EE2 was the least removed. Removal efficiencies were improved as the thickness of the unsaturated zone increased whereas increased DOC improved the removal in the saturated columns. Enhanced removal efficiencies were also obtained at lower water flow rates and in the presence of silt and clay. [ABSTRACT FROM AUTHOR]

Abstract: A set of bioassays (acute toxicity to Daphnia, genotoxicity, estrogenic and antiestrogenic toxicity) was used to evaluate the safety of reclaimed water reuse in a lab-scale artificial groundwater recharge system. Ozonation of 1mg O3·(mg DOC)−1 was used as the pretreatment and was proved to be effective in removing the four toxicity, with removal ratios ranging from 56% to 99%. In the vadose layer, the responsible compounds for toxicity were less efficiently removed than the bulk organic compounds. However, they were preferentially removed during the saturated aquifer treatment, with all the toxic effects per carbon mass dropping by 20–50%. Therefore, more than one month traveling in the aquifer is suggested before water reuse. Since UV254 was significantly correlated with the toxicity data, it could serve as an indicator of the toxicity. With the bioassay-based safety evaluation, the combination of soil aquifer treatment and ozonation could provide new water sources with no higher toxic than the conventional natural drinking water source. [Copyright &y& Elsevier]

Abstract: Soil Aquifer Treatment (SAT) is a process where treated wastewater is purified during transport through unsaturated and saturated zones. Easily biodegradable compounds are rapidly removed in the unsaturated zone and the residual organic carbon is comprised of primarily high molecular weight compounds. This research focuses on flow in the saturated zone where flow conditions are predictable and high molecular weight compounds are degraded. Flow through the saturated zone was investigated with 4 reactors packed with 2 different particle sizes and operated at 4 different flow rates. The objective was to evaluate the kinetics of transformation for high molecular weight organics during SAT. Dextran was used as a model compound to eliminate the complexity associated with studying a mixture of high molecular weight organics. The hydrolysis products of dextran are easily degradable sugars. Batch experiments with media taken from the reactors were used to determine the distribution of microbial activity in the reactors. Zero-order kinetics were observed for the removal of dextran in batch experiments which is consistent with hydrolysis of high molecular weight organics where extracellular enzymes limit the substrate utilization rate. Biomass and microbial activity measurements demonstrated that the biomass was independent of position in the reactors. A Monod based substrate/biomass growth kinetic model predicted the performance of dextran removal in the reactors. The rate limiting step appears to be hydrolysis and the overall rate was not affected by surface area even though greater biomass accumulation occurred as the surface area decreased. [Copyright &y& Elsevier]

Soil aquifer treatment (SAT) using primary effluent (PE) is an attractive option for wastewater treatment and reuse in many developing countries with no or minimal wastewater treatment. One of the main limitations of SAT of PE is rapid clogging of the infiltration basin due to high suspended solid concentrations. Some pre-treatment of PE before infiltration is likely to reduce this limitation, improve performance of SAT and help to implement this technology effectively. The effects of three pre-treatment options namely sedimentation (SED), coagulation (COAG) and horizontal roughing filtration (HRF) on SAT were analyzed by conducting laboratory-scale batch and soil column experiments. The sedimentation and coagulation pre-treatments led to less head loss development and reduction of clogging effect. The head loss development in soil column using PE + COAG and PE + SED was reduced by 85 and 72%, respectively, compared to PE alone without any pretreatment. The overall dissolved organic carbon (DOC) removal of pre-treatments and soil column collectively were 34, 44, 51 and 43.5% for PE without any pre-treatment, PE + SED, PE + COAG and PE + HRF, respectively. Coagulation pre-treatment of PE was found to be the most effective option in terms of suspended solids, DOC and nitrogen removal. Sedimentation pre-treatment of PE could be attractive where land is relatively less expensive for the construction of sedimentation basins. [ABSTRACT FROM AUTHOR]

Abstract: A 2000 mm long saturated laboratory soil column was used to simulate soil aquifer treatment under saturated conditions to assess the removal of chemical and biochemical oxygen demand (COD and BOD), dissolved organic carbon (DOC), nitrogen and phosphate, using high strength artificial wastewater. The removal rates were determined under a combination of constant hydraulic loading rates (HLR) and variable COD concentrations as well as variable HLR under a constant COD. Within the range of COD concentrations considered (42 mg L−1–135 mg L−1) it was found that at fixed hydraulic loading rate, a decrease in the influent concentrations of dissolved organic carbon (DOC), biochemical oxygen demand (BOD), total nitrogen and phosphate improved their removal efficiencies. At the high COD concentrations applied residence times influenced the redox conditions in the soil column. Long residence times were detrimental to the removal process for COD, BOD and DOC as anoxic processes and sulphate reduction played an important role as electron acceptors. It was found that total COD mass loading within the range of 911 mg d−1–1780 mg d−1 applied as low COD wastewater infiltrated coupled with short residence times would provide better effluent quality than the same mass applied as a COD with higher concentration at long residence times. The opposite was true for organic nitrogen where relatively high concentrations coupled with long residence time gave better removal efficiency. [Copyright &y& Elsevier]

Abstract: The attenuation of a diverse suite of contaminants of emerging concern (CECs) and bulk water quality changes was evaluated at a surface-spreading aquifer recharge operation across a detailed subsurface profile (9 locations), representing both short- and long-travel times (10h to 60days). Seventeen CECs were detected in the recharge basin and the concentrations of all were reduced during soil aquifer treatment (SAT), with 11 of the target compounds attenuated by >80% after 60days of travel time. Select CECs (atenolol, gemfibrozil, N,N-diethly-3-methylbenzamide, meprobamate, tris(2-chloroethyl)phosphate, and primidone) and bulk water organic-carbon measurements (total organic carbon, biodegradable organic carbon, size-exclusion chromatography and fluorescence excitation–emission matrices) were identified as monitoring parameters that can be used to assess SAT performance at surface-spreading operations. [ABSTRACT FROM AUTHOR]

Summary: Irrigation with treated wastewater (TWW) has been reported to induce low to moderate hydrophobicity in soils of different texture with or without vegetation cover. Additional potential sites for adverse effects of TWW are infiltration basins, where TWW undergoes tertiary treatment, known as soil aquifer treatment (SAT). The annual organic matter (OM) loads in SAT are a hundred fold higher than those applied in irrigation with TWW. Therefore, we initially presumed that in the sandy soils of SAT infiltration basins, hydrophobicity would be expressed to a higher extent and would further affect the hydraulic properties of these soils. This hypothesis was tested in the Dan Region Wastewater Reclamation Project, Tel-Aviv, Israel. In terms of water drop penetration time (WDPT) test, the results obtained exhibited similar hydrophobicity levels (0⩽WDPT⩽238s) to those obtained in the TWW irrigated fields and in a similar manner, soil hydrophobicity was only exhibited in the surface soil layer. It is suggested that the low to moderate hydrophobicity obtained under TWW irrigation and recharge into the SAT basins, may primarily stem from the drying and wetting cycle regimes employed. Under these conditions, hydrophobic compounds, which may impart hydrophobicity to the soil particles, are likely to detach and dissolve into the soil solution at the subsequent irrigation or recharge event. Furthermore, the frequent displacement of the resident TWW derived OM by repeatedly flooding events, prevents maturation and humification of the resident OM. Further investigations on the hydraulic properties of the basin soils were conducted in conjunction with the solid–liquid contact angle (ω) and the surface tension (γ L) of the soil solution. The results obtained imply that the dependence of the hydraulic properties on ω and/or γ L, can be attributed to the hydrophobic nature of both the solid and dissolved OM originating from the recharged TWW. [Copyright &y& Elsevier]

Results from a direct recharge experiment conducted in the field to investigate DOC and UVA254 attenuation rates during the direct injection of UF treated wastewater into a artificial coastal sandfill are presented in this paper. Approximately 500m3 of ultra-filtered wastewater was injected into the saturated zone, over a period of 9 days. The movement of the plume was tracked over 80 days, during which time samples were obtained from multilevel samplers installed in transects across the drift axis of the plume. An analysis of fluorescein in the samples obtained during the drift of the UF plume showed that DOC and UVA were attenuated beyond rates predicted by conservative mixing, by up to a maximum of 45%. A degradation coefficient of 0.0175 day-1 was found to be applicable for DOC degradation. After a drift period of 80 days, DOC and UVA reduced to approximately 4.5 mg/l and 0.100cm-1, respectively, from initial values of 8.06 mg/l and 0.199cm-1. [ABSTRACT FROM AUTHOR]

There are current concerns about the presence of persistent chemicals in recharge water used in soil aquifer treatment systems. Triclocarban (TCC) has been reported as a persistent, high production volume chemical with the potential to bioaccumulate in the environment. It is also known to have adverse effects such as toxicity and suspected endocrine disruption. This study was carried out to study the fate of TCC in soil aquifer treatment (SAT) through laboratory simulations in a soil column. The system performance was evaluated with regards to TCC influent concentration, sand (column) depth, and residence time. Results obtained confirmed the ability of SAT to reduce TCC concentrations in wastewater. Sorption and biodegradation were responsible for TCC removal, the latter mechanism however being unsustainable. The removal efficiency was found to be dependent on concentration and decreased over time and increased with column depth. Within the duration of the experimental run, TCC negatively impacted on treatment performance through a reduction in COD removals observed in the column. [ABSTRACT FROM AUTHOR]

Soil aquifer treatment (SAT) and bank filtration use natural attenuation processes to purify water for subsequent use. Soil aquifer treatment may constitute both unsaturated and saturated flow conditions, while bank filtration systems are primarily saturated flow. This analysis focuses on the saturated zone, where the majority of residence time occurs, in both SAT and bank filtration systems. Sustainable removal mechanisms during subsurface flow are primarily surface-mediated and therefore depend on surface area. By analyzing saturated subsurface flow hydraulics in granular media, a relationship between surface area and travel time was developed. For saturated subsurface flow, the ratio of surface area-to-travel time varied by approximately a factor of 3, for common aquifer materials subject to identical hydraulic gradients. Because travel time criteria often are used to regulate SAT and bank filtration systems, these criteria also may determine the surface area and associated surface-mediated reactions for water purification. The ratio of surface area-to-travel time increases with increasing hydraulic gradient, implying that surface area is relatively constant for specific travel times, even if the hydraulic gradient changes; however, the increasing hydraulic gradient will increase the distance from the recharge zone to the recovery well. Therefore, travel time assessments based on maximum possible hydraulic gradients increase surface area and could provide a conservative limit for surface-mediated reactions. This analysis demonstrates that travel time criteria for SAT and bank filtration systems indirectly provide a minimum surface area that may support sustainable removal mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: The hydraulic residence time (HRT) is a key parameter affecting the soil aquifer treatment process (SAT) efficiency as tertiary treatment of wastewater through infiltration in vadose zone. In order to maximize the HRT, a pulsed feeding technique of a salt solution (used as conservative tracer) was adopted to allow the increase of HRT and soil aeration between pulses. For this reason, several laboratory column experiments combined with the use of a numerical model was conducted. The optimal number of pulsations that meet with the maximum of the HRT and the temporal variation of the water saturation into the column was determined for different applied hydraulic heads. It varies between 10 and 12. The maximum corresponding water stock in the porous media column was evaluated to about 84%, 79% and 73%, respectively, for an applied hydraulic head of 96, 75 and 50 cm. The applied hydraulic head had an important effect on the HRT. In fact, this parameter varies from almost 6.5 to 10.8 h for an applied hydraulic head of 96 and 50 cm. The change in the permeability of the soil had also a significant effect on the HRT. Hence, HRT is decreased of about 9% when the soil permeability at saturation is multiplied by 2, and increases of about 11% when the permeability is two times lower. [Copyright &y& Elsevier]

A controlled artificial recharge experiment was conducted to investigate the effect of soil aquifer treatment during percolation of secondary and tertiary (ultrafiltered) treated wastewater through the shallow vadoze zone of a newly constructed coastal sandfill. The sandfill is a reclaimed land constructed from marine sand dredged from the seabed. To obtain 1-D flow, a stainless steel column was driven to a depth of 2.5 m, penetrating the phreatic surface. Wastewater was percolated through the column under fully-saturated and unsaturated conditions. Infiltration rates, dissolved organic carbon (DOC) and ultra-violet absorption (UVA) were monitored. The wastewaters were recharged at similar infiltration rates of approximately 5.5 m/day and 3.5 m/day under fully-saturated and unsaturated conditions, respectively. In both cases, clogging occurred 40 days after the start of recharge, under saturated conditions. For secondary treated wastewater, DOC concentration (mg/l) reduced by 28% and 13% under unsaturated and saturated conditions, respectively. The corresponding UVA reduction was 19.4% and 14.1%. Similar reductions in DOC were observed for the tertiary treated wastewater; however, the reduction in UVA was higher; 28% and 22% under unsaturated and saturated conditions, respectively. On an mass removal (mg/m2 DOC) basis, DOC reduction appeared to be more significant under unsaturated conditions. This is attributed to the presence of interstitial oxygen. [ABSTRACT FROM AUTHOR]

A method for the simultaneous determination of seven commonly used artificial sweeteners in water is presented. The analytes were extracted by solid phase extraction using Bakerbond SDB 1 cartridges at pH 3 and analyzed by liquid chromatography electrospray ionization tandem mass spectrometry in negative ionization mode. Ionization was enhanced by post-column addition of the alkaline modifier Tris(hydroxymethyl)amino methane. Except for aspartame and neohesperidin dihydrochalcone, recoveries were higher than 75% in potable water with comparable results for surface water. Matrix effects due to reduced extraction yields in undiluted waste water were negligible for aspartame and neotame but considerable for the other compounds. The widespread distribution of acesulfame, saccharin, cyclamate, and sucralose in the aquatic environment could be proven. Concentrations in two influents of German sewage treatment plants (STPs) were up to 190 μg/L for cyclamate, about 40 μg/L for acesulfame and saccharin, and less than 1 μg/L for sucralose. Removal in the STPs was limited for acesulfame and sucralose and >94% for saccharin and cyclamate. The persistence of some artificial sweeteners during soil aquifer treatment was demonstrated and confirmed their environmental relevance. The use of sucralose and acesulfame as tracers for anthropogenic contamination is conceivable. In German surface waters, acesulfame was the predominant artificial sweetener with concentrations exceeding 2 μg/L. Other sweeteners were detected up to several hundred nanograms per liter in the order saccharin ≈ cyclamate > sucralose. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Soil column experiments were performed to investigate the behavior and characteristics of dissolved organic matter (DOM) during soil aquifer treatment (SAT), and to differentiate among the mechanisms responsible for the changes in the structural and functional properties of DOM during SAT. To determine the biological transformation of DOM, biodegradability tests using a biodegradation-column system were conducted. DOM was fractionated using XAD resins into 5 fractions: hydrophobic acid (HPO-A), hydrophobic neutral (HPO-N), transphilic acid (TPI-A), transphilic neutral (TPI-N) and hydrophilic fraction (HPI). Dissolved organic carbon (DOC) was removed by 70% during SAT, and the sorption and anaerobic biodegradation in SAT led to a DOC reduction of 27.4%. The significant changes in fluorescence properties of DOM were observed during SAT. However, the sorption and anaerobic biodegradation in SAT seemed to have no significant effect on the chemical structure of fluorescing constituents in DOM. The DOM fractions exhibited different changes in Fourier-transform infrared (FT-IR) spectra characteristics during SAT. Biodegradation resulted in the enrichment of aromatic structures and the decreased content of the oxygen-containing functional groups, such as Cx2013;O, in DOM. On the other hand, the production of C–O and amide-2 functional groups occurred as a result of the sorption combined with anaerobic biodegradation in SAT. [Copyright &y& Elsevier]

Removal of organic matter is a critical parameter in soil aquifer treatment (SAT) as it governs and influences the removal of other contaminants by biodegradation namely trace organics, nitrogen species and microbes. A framework for analysis and prediction of the performance of SAT systems with respect to removal of organic matter under different water quality and process conditions was developed based on an extensive literature review and data analysis. Guidelines were developed to make preliminary estimates of the removal of organic matter during SAT using primary, secondary and tertiary effluents from wastewater treatment plants. These guidelines can be used as a quick tool to analyze the performance of existing SAT systems and serve as a decision support tool for feasibility studies and to save time for further detailed experimentation and design of SAT systems. Furthermore, effects of soil type and redox conditions on organic matter removal during SAT were also analyzed. [ABSTRACT FROM AUTHOR]

Abstract: Passing treated wastewater through soil is a natural and economic means to improve the quality of wastewater. The United Agricultural Production Company (UAPCO) farm located in the Sulaibiya area of Kuwait has been irrigated with tertiary treated wastewater since 1976. A field investigation at the farm has been conducted by the Kuwait Institute for Scientific Research (KISR) to assess the applicability of the natural soil treatment method, in the long term, to improve the quality of the treated wastewater under the conditions prevailing in Kuwait. The collected data have been analyzed to assess the degree of improvement in quality of the infiltrated water with respect to the tertiary wastewater used for irrigation. The data analysis indicates that in spite of low clay content of the soil, improvement in the quality of the tertiary treated wastewater through soil aquifer treatment by the removal of ammonia (>90%), iron (>80%), organic carbon (>90%), biological oxygen demand (BOD) (100%) and bacteria (50–100%, depending on its type), can be expected over a long-term period. Soil leaching, however, tends to increase the total dissolved solids of the infiltrated water and the nitrification process increases the nitrate content. [Copyright &y& Elsevier]

Abstract: GIS and expert knowledge are used as a decision support system to determine adequate potential soil aquifer treatment (SAT) sites for groundwater recharge of Hammamet–Nabeul aquifer located in ‘Cap Bon’ peninsula in North East of Tunisia. These sites are identified using a single-objective multi-criteria analysis. All criteria selected are assumed to be constraints. The acceptable range of each criterion is determined by a critical threshold value, corresponding to standards or normative statements. Based on these acceptable ranges, all criteria are expressed in a Boolean map: excluded areas are coded 0 and those open for consideration are coded 1. Multi-criteria evaluation were performed combining all Boolean maps by means of intersect operator in order to select sites meeting all the criteria. The selection of criteria and acceptable ranges is based on national expert consulting and international published guidelines and technical documents. The resulting map of this GIS-based multi-criteria analysis shows extended potential sites for SAT, exceeding 1000 ha, which indicates a possible use of treated wastewater for groundwater recharge; 8 ha could be supplied by Hammamet Sud plant, 764 ha by SE3 and 347 ha by SE4. 109 ha of these areas could be supplied by both SE3 and SE4. These potential sites are mostly located at rivers banks, around Grand-Nabeul urban area and in some agricultural domains and coastal dunes. [Copyright &y& Elsevier]

Abstract: Field studies were conducted to investigate the advanced treatment of the municipal secondary effluent and a subsequent artificial groundwater recharge at Gaobeidian Wastewater Treatment Plant, Beijing. To improve the secondary effluent quality, the combined process of powdered activated carbon adsorption, flocculation and rapid sand filtration was applied, which could remove about 40% dissolved organic carbon (DOC) and 70% adsorbable organic halogens. The results of liquid size exclusion chromatography indicate that in the adsorption unit the removed organic fraction was mainly low molecular weight compounds. The fractions removed by the flocculation unit were polysaccharides and high molecular weight compounds. The retention of water in summer in the open recharge basins resulted in a growth of algae. Consequently, DOC increased in the polysaccharide and high molecular weight humic substances fraction. The majority of the DOC removal during soil passage took place in the unsaturated area. A limited reduction of DOC was observed in the aquifer zone. [Copyright &y& Elsevier]

Abstract: This study investigates the relationship between soil biomass and organic carbon removal during the infiltration of conventionally treated effluents used for groundwater recharge during soil-aquifer treatment (SAT). Investigations were conducted on samples collected from full-scale SAT sites, revealing a positive correlation between biodegradable organic carbon (BOC) concentrations in the recharged effluents and total viable soil biomass concentrations in the infiltration zone of soil samples collected from respective recharge basins. Findings of this study suggest that BOC limits soil biomass growth and was able to support a steady-state concentration of viable soil biomass that is characteristic to BOC concentrations introduced with the recharged effluents. All investigated sites indicate that BOC is primarily removed within 30cm soil depth leading to a significant increase in soil biomass levels (measured as substrate induced respiration (SIR), total viable biomass, and dehydrogenase activity (DHA)). Controlled biological column studies revealed that the primary components of BOC in domestic effluents are organic colloids. Findings of this study support that hydrophobic acids, commonly believed to be recalcitrant, may also be attenuated by biological processes during soil infiltration. [Copyright &y& Elsevier]

Abstract: Two case studies are described that explain the role, value, limitations and policy requirements for storing reclaimed water in aquifers for indirect reuse. The first case involves aquifer storage and recovery of water, the product of tertiary treated municipal sewage effluent, via a single injection and recovery well at Bolivar, South Australia. The recovered water, like the source water for injection, is used for unrestricted irrigation of horticulture. A limestone aquifer at a depth of 100 to 160 m confined by clay and containing brackish groundwater provides the storage zone. In the second case, located at Alice Springs, trials are proceeding to assist in the design and establishment of a soil–aquifer treatment system which will allow water derived from secondary treatment of municipal sewage effluent to be stored in an unconfined alluvial aquifer for irrigation of horticulture. Intermittent infiltration from basins provides supplementary water treatment. In each case, the motivations, choice of methods, required investigations, public consultation processes, and economics of subsurface storage are presented. The lessons learned that may assist with development of policies to facilitate environmentally sustainable subsurface storage of water in water reuse projects are discussed. [Copyright &y& Elsevier]

Bench-scale soil column experiments were performed to examine the effects of soil type and infiltration conditions on the removal efficiencies of wastewater nitrites and nitrates during the biological ripening phase of soil aquifer treatment (SAT) columns. SAT was simulated in three 1-m-high soil columns packed with 3 different natural agricultural soils having sandy clay loam (SCL), loamy sand (LS) and sandy loam (SL) textures. All columns were equipped with tensiometers and soil-water sampling ports, and received secondary effluent from a wastewater treatment plant with a conventional biological treatment system. Soil columns were ponded with wastewater to a depth of 2.5 cm above the soil surface and operated under 2 different alternating wet and dry cycles, 7 days wet/7 days dry and 3 days wet/4 days dry. The effect of wetting and drying periods on SAT nitrogen removal performance was assessed comparing nitrite and nitrate removal rates of 7 days wetting/7 days drying and 3 days wetting/ 4 days drying cycles. Infiltration rate and the length of wetting period were important parameters affecting nitrogen removal efficiency of SAT columns. Denitrfication performance of the columns decreased significantly when the infiltration schedule was switched from 7 days wetting/7 days drying to 3 days wetting/4 days drying cycles. LS soil operated with 7 days wetting/7 days drying cycles had the highest (95%) nitrogen removal performance. SCL and SL soils can be operated under both 7 days wetting/7 days drying cycles and 3 days wetting/4 days drying cycles to meet the denitrification/nitrification requirements of SAT. [ABSTRACT FROM AUTHOR]

Soil batch and column experiments were performed to characterize the wastewater effluents from seven different wastewater treatment plants in the Jonnam province, South Korea, with the purpose of evaluating the effluents for possible application of a soil aquifer treatment (SAT) in Korea. Batch experiments were conducted to measure the biodegradable dissolved organic carbon (BDOC) while 1 m soil columns, for simulating SAT, were employed to further analyze dissolved organic carbon (DOC) removal. The soils were collected from a river bottom in Jonnam. The BDOC fractions and the residual DOC concentrations for the effluents ranged from 19.3 to 59.9% and from 1.0 to 7.5 mg/L, respectively, depending on the reaction time. Applying the tentative criteria based on the data obtained for the BDOC and residual DOC, three effluents, from Gwangju, Hwasoon, and Jangsung, were found to be the most suitable for SAT applications. It was also concluded that the site characteristics should be also considered with regard to the retention time when evaluating the feasibility of SAT application in a certain region. [ABSTRACT FROM AUTHOR]

Mexico City, with a population of 18 million, has been sending its wastewater for more than 100 years to the Tula Valley where it is used to irrigate 90,000 ha. Due to the large wastewater volume (60 m³/s) sent through unlined channels, combined with the use of very high irrigation rates, artificial recharge of the local aquifer has been occurring. This recharge is estimated in more than 25 m³/s. As a consequence, the water table has raised and several springs have appeared in the last decades with flows between 100 to 600 L/s. These springs and several wells are the water sources in the region. An evaluation of the Tula Valley aquifer quality was performed to analyze the use of such water as source of drinking water for Mexico City. The work is divided into 5 individual projects: (a) drinking water quality in the Tula Valley; (b) water availability in the Tula Valley; (c) wastewater treatment due to its use for irrigation, (d) use of membrane processes to treat groundwater; and (d) biota developed in the new surface water reservoirs. Results show that it is feasible to use this reclaimed water as drinking source. [ABSTRACT FROM AUTHOR]