Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Water purification wikipedia , lookup
Portable water purification wikipedia , lookup
Environmental remediation wikipedia , lookup
Ultraviolet germicidal irradiation wikipedia , lookup
Water pollution wikipedia , lookup
Biochemical oxygen demand wikipedia , lookup
Constructed wetland wikipedia , lookup
Sewage treatment wikipedia , lookup
Ozone and Aquifer Recharge and Recovery Hybrid for Attenuation of Bulk and Trace Organic Contaminants Min K. Yoon* and Gary L. Amy King Abdullah University of Science and Technology (KAUST), 4700 KAUST. Thuwal, 23955, Saudi Arabia (E-mail: [email protected]; [email protected]) *Corresponding author Abstract The attenuation of bulk organics and trace organic contaminants (TOrCs) during an aquifer recharge recovery (ARR) coupled ozone (O3) treatment hybrid was evaluated in soil-batch and bench-scale ozonation simulations for wastewater reclamation and reuse. In this work, the role of biodegradation in the removal of bulk organics and TOrCs was investigated during soil passage alone (i.e., ARR), after ozonation (i.e., ARR-O3) and prior to ozonation (i.e., O3-ARR). ARR simulations alone and ARR coupled ozonation hybrids were compared using percent removal of bulk organic characters and a representative subset of TOrCs (i.e. contaminants of emerging concern). In oxic ARR simulations alone, higher molecular weight polysaccharides and proteins (i.e., biopolymers) were easily removed while lower molecular weight humic substances and aromatic organic matter were not easily removed over a short-term ARR operation. In ARR coupled ozonation hybrids, removal of bulk organics and TOrCs was effective and rapid compared to ARR alone. A higher reduction of effluent-derived organic matter, including aromatic organic matter and humic substances, was observed in the ARR-O3 hybrid followed by the O3-ARR hybrid. An enhanced attenuation of recalcitrant TOrCs was determined by a slight increase of ozone dose (O3: DOC = 1) and/or a post-ozone treatment (i.e. ARR-O3). In addition, the carcinogenic wastewater by-product, N-Nitrosodimethylamine (NDMA), was eliminated below the method reporting limit (< 5ng/L) in both ARR alone and ARR hybrids. Keywords Wastewater treatment, Aquifer recharge and recovery, Ozonation, Trace organic contaminant INTRODUCTION Elimination processes during soil passage, via both oxic and anoxic biodegradation as well as sorption, provide an effective barrier for attenuation of effluent-derived organic carbon. However, some trace organic contaminants (TOrCs) are not easily removed or require a long residence time or a unique redox condition. Previous findings on TOrC removal in ARR are summarized as follows: 1) removal of degradable TOrCs (with the exception of diclofenac and propyphenazone) under aerobic porous infiltration condition is equal or better compared to anoxic porous infiltration conditions, 2) biodegradable dissolved organic carbon (BDOC) can serve as a co-substrate in the co-metabolic transformation of TOrCs, 3) concentration and character of bulk organic carbon present in effluent affects the degradation efficiency for TOrCs during the recharge operations, 4) redox conditions and degradation potential as a function of temperature are key factors in influencing performance (Hoppe-Jones et al. 2010; Maeng et al. 2010). In the work reported herein, an oxidation (ozonation) process was tested prior to, and after, soil passage for the removal of dissolved organic carbon (DOC) and recalcitrant TOrCs and for effective drinking water treatment. Ozonation can convert refractory DOC such as humics/fulvics into more biodegradable components. Studies have shown that oxidation improves the biodegradability of poorly degradable organic compounds in ARR systems because of co-metabolism. In the case of using ozone as a pre-treatment, it can 1) reduce TOrCs loading in a subsequent ARR by eliminating the precursors and 2) make the matrix more amenable to biotransformation (i.e. creation of BDOC), thereby achieving further TOrC reductions. In a post-ozonation strategy, ARR will remove a significant amount of effluent organic matter (EfOM) and reduce the concentrations of contaminants and specific TOrCs. This will reduce the oxidant scavenging potential of the matrix and increase the overall efficiency of the downstream ozone process. Thus, ozonation can be an effective treatment strategy for both sequences with ARR. Selected TOrCs were used as representative indicators for oxidation and aquifer recharge recovery (ARR) conditions. Due to the low concentrations of these TOrCs in typical wastewater effluent, trace analysis of the TOrCs was required, and performed using solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS). The attenuations of bulk organics and TOrCs in different hybrids of O3 and ARR (O3-ARR) vs. ARR and O3 (ARR-O3) were examined to understand parameters and conditions controlling their removal as an effort to assess ARR wastewater reuse strategies. Both configurations were considered because the O3-ARR approach could provide a barrier for eliminating transformation products (oxidation by-products) and the latter ARR-O3 approach could result in a lower oxidant demand and lead to lower costs. The amount and character of BDOC were important factors influencing the fate of TOrCs during ARR. BDOC fractions and their rates (slow vs. rapid) were compared between ARR and different ARR hybrids in this work. Water quality parameters were evaluated using DOC and specific ultraviolet absorbance (SUVA) augmented by further characterization with innovative EfOM characterization techniques of liquid chromatography - organic carbon detection and - organic nitrogen detection (LC-OCD-OND) and 3D fluorescence excitation-emission matrix (F-EEM). The objective of this study was to determine the most effective combination of ozone and aquifer recharge recovery as a treatment hybrid. METHODS Experimental Setups In bench-scale tests, Milli-Q water was ozonated in 2 L glass flasks by bubbling ozone from oxygen gas produced by an LAB2B ozone generator (Ozonia, Degremont Technologies). The dissolved ozone in the stock solution was measured periodically at a wavelength of 258 nm (Δ ε = 2950 M-1 cm-1) (Rakness et al. 1996) and was confirmed by the indigo trisulfonate method (Bader and Hoigné 1981). A specific volume of the ozonated water was transferred to batch reactors that contained secondary effluent from the Al-Ruwais Wastewater Treatment Plant (ARWWTP; Jeddah, Saudi Arabia) at room temperature (21°C). Applied (transferred) ozone doses took into account dilution of the stock solution with tested water. The ARWWTP wastewater (after primary treatment) was treated in activated sludge aeration tanks. The typical water quality of the ARWWTP secondary effluent is summarized in Table 1. Ozone to DOC (O3: DOC) ratios of 0.5 and 1 mg/mg were selected because previous studies have demonstrated efficacy in oxidizing a wide range of contaminants over this range (Sundaram 2009; Gerrity et al. 2011). For the soil component, the batch sands were prepared in 1 L glass bottles using 150g (dry weight) of washed silica sand (grain sizes 0.5 - 1 mm; bulk density 1.5 - 1.6 g/cm3; sand porosity 40%). The sands were then bioacclimated for 8 weeks with secondary effluent from the ARWWTP. During this period, DOC and UV254 absorbance were monitored until steady state was achieved. After the acclimation period, the soil batch reactors were fed with secondary effluent or ozonated secondary effluent until a range of retention times had been achieved (3 hrs., 1, 3, 5, 8, 12 days). The reactors were kept on a shaker table to ensure aerobic conditions. Water samples were then collected to assess biodegradability of bulk organics and TOrCs or post-ozonated. This experimental setup allowed for evaluations of bulk organic and TOrC attenuation with oxic ARR alone, O3-ARR and ARR-O3. To differentiate microbial biodegradation and sorption, abiotic batch reactors were also prepared with sodium azide at 20 mM (Maeng 2010) and monitored over 5 days. Sorption isotherms were generated using a linear regression analysis with TOrC concentrations ranging from 0.5 to 10 μg/L. An overview of experimental approach is provided in Figure 1. Table 1. ARWWTP Secondary Effluent Water Quality Water Quality Parameters pH Conductivity (µS/cm) Dissolved Organic Carbon (mg/L) UV254 Absorbance (cm-1) Turbidity (NTU) Fluoride (mg/L) Chloride (mg/L) Nitrite (mg/L) Bromide (mg/L) Nitrate (mg/L) Phosphate (mg/L) Sulfate (mg/L) 7.1 3300 5.9 0.148 0.47 0.21 746.24 < MRL 1.44 28.24 11.28 411.29 Figure 1. Simplified Schematic for Experimental ARR Scenarios Analysis of Bulk Organics DOC was measured using a Shimadzu TOC analyzer and BDOC (operationally defined as the change in DOC by biodegradation under the conditions investigated) was measured weekly during the bio-acclimation period (8 weeks). In addition, UV254 and SUVA were monitored as indicators of aromaticity and humic substances using a Shimadzu UV-Vis Spectrophotometer (UV-2550). LC-OCD-OND-UV254nm based on the Gräntzel thin-film UV reactor (DOC-Labor Dr. Huber, Germany) was used to evaluate major molecular-size fractions of natural organic matter such as slowly degrading biopolymers vs. rapidly degrading low molecular weight acids and neutrals during treatment processes. Protein- (i.e., soluble microbial product-like), and humic- and fulvic-like EfOM in water samples were characterized using fluorescence excitation-emission matrix (F-EEM) using a FlouroMax4 (Horiba, USA). The spectrofluorometer included a 150-W xenon lamp. Slit width for both excitation and emission monochromators was set to 5 nm and a 5 nm increment was used. Analyses were performed in a 1-cm quartz cuvette at room temperature (21 °C). Samples were analyzed in signal/reference mode where the fluorescence emission intensity is normalized to the intensity of the lamp at the particular excitation wavelength applied. Analysis of Trace Organic Contaminants (TOrCs) A representative set of TOrCs were selected based on several factors, including structural and chemical properties (e.g. functional groups, polarity, aromaticity, etc.), use classes (e.g. antibiotic, fragrance, pharmaceutical, etc.), high frequency of environmental occurrence (Kolpin et al. 2002; Benotti et al. 2008), resistance to natural treatment processes (e.g. biodegradation, photolysis, etc.) and engineering treatment processes (e.g. adsorption, oxidation, etc.) (Ternes et al. 2002; Huber et al. 2003; Westerhoff et al. 2005), and amenability to existing analytical methods. Each of seventeen target TOrCs and the corresponding classification, CAS numbers, physiochemical properties (i.e., molecular weight, water solubility, pKa and log P), ozone rate constant and method reporting limit are listed in Table 2. Additionally, tris (1-chloro-2-propyl) phosphate (TCPP) was added because it was used instead of tris (2-chloroethyl) phosphate (TCEP) in the abiotic experiment. All samples were collected in amber glass bottles preserved with sodium azide (1 g/L) and ascorbic acid (50 mg/L). The samples were processed with solid phase extraction and analyzed with GCMS/MS (for NDMA analysis) and LC-MS/MS with isotope dilution according to the previously published studies (Vanderford et al. 2003; Trenholm et al. 2006; Vanderford and Snyder 2006). Table 2. Target TOrCs with Their CAS No. and Physicochemical Properties Compound Use Class CAS No. 29122-68-7 1912-24-9 80-05-7 298-46-4 134-62-3 15307-86-5 25812-30-0 15687-27-1 57-53-4 81-14-1 22204-53-1 57-41-0 125-33-7 Molecular Weight (g/mol) 266.3 215.7 228.3 236.3 191.3 296.2 250.3 206.3 218.3 294.2 230.3 252.3 218.3 Water Solubility (mg/L) 1.33 x 104 27 120 18 912 2.37 28 21 3400 5 15.9 71 500 Atenolol Atrazine Bisphenol A Carbamazepine DEET Diclofenac Gemfibrozil Ibuprofen Meprobamate Musk Ketone Naproxen Phenytoin Primidone Beta-Blocker Herbicide Plasticizer Anticonvulsant Pesticide NSAID Lipid Regulator NSAID Anti-Anxiety Fragrance NSAID Anticonvulsant Anticonvulsant Sulfamethoxazole TCEP TCPPb Triclosan Trimethoprim Antibiotic Flame Retardant Flame Retardant Anti-Microbial Antibiotic 723-46-6 115-96-8 13674-84-5 3380-34-5 738-70-5 253.3 285.5 327.6 289.5 290.3 610 7000 1200 10 400 pKa logP (exp)a kO3 (M-1 s1 c* ) kOH (M-1 s-1)d* MRLe (ng/L) 9.2 1.7 9.6, 10.2 13.9 0.7 (est.) 4.15 4.42 4.91 14 (est.) N/A 4.15 8.3 11.1 (est.), 12.2 (est.) 5.5 N/A N/A 7.98 (est.) 7.12 0.16 2.61 3.32 2.63 (est.) 2.18 4.51 3.80 (est.) 3.97 0.7 3.82 (est.) 3.18 2.47 0.91 2 x103 6 7 x105 3 x105 < 10 1x106 2x104 10 <1 <1 2 x105 < 10 < 10 8 x 109 3 x 109 1 x 1010 9 x 109 5 x 109 8 x 109 1 x 1010 7 x 109 4 x 109 1 x 109 1 x 1010 6 x 109 7 x 109 25 10 50 10 25 25 10 25 10 100 25 10 10 0.89 1.44 2.59 4.76 0.91 3 x106 <1 N/A 4 x107 3 x105 6 x 109 7 x 108 N/A 1 x 1010 7 x 109 25 200 200 25 10 Note: All physicochemical properties obtained from Snyder et al., 2009 a log P (exp) : Other than indicated explicitly, all are experimental values obtained from ALOGPS 2.1 (PHYSPROP database) b The compound, TCPP was used instead of TCEP in abiotic experiment. c* d* Second order rate constant for ozone Second order rate constant for hydroxyl radical Method reporting limit (MDL) : Based on 3-5 times the calculated MDL in DI, n=12 (TCEP based on 5 times average background) * Sources: (Ternes et al. 2002; Huber et al. 2003; Westerhoff et al. 2005; Gerrity et al. 2011) e RESULTS AND DISCUSSION Bulk Organic Characterization A net reduction of DOC was observed in all systems (i.e., O3-ARR, ARR- O3 and ARR alone) and the highest reduction was achieved for O3-ARR (29%) followed by ARR-O3 (24%), both at O3: DOC=1, O3-ARR (23%) at O3: DOC = 0.5, ARR alone (17%), and then ARR-O3 (16%) at O3: DOC = 0.5. The UV254 absorbance and specific UV254 absorbance (SUVA = UV254 absorbance/DOC) data indicated that the O3-ARR and ARR-O3 were superior to ARR alone. For UV254 absorbance, ARR-O3 provided 60% and 72% reduction at low (O3: DOC = 0.5) and high (O3: DOC=1) O3 doses, respectively, and O3-ARR provided 49% and 57% at low and high O3 doses, respectively. However only a 28% reduction in UV254 absorbance was observed for ARR alone. The summary of percent (%) removal of DOC and UV254 is provided in Table 3. Overall, DOC removal was higher with pre-ozonation due to the increase of BDOC during oxidation, and UV254 removal was higher in post-ozonation due to the more efficient destruction of aromatic humic substances under conditions of lower ozone demand. Table 3. Percent (%) DOC and UV254 Removal in ARR Combinations. ARRs O3: DOC % DOC Removal % UV254 Removal ARR alone 0 17 28 O3-ARR 0.5 23 49 O3-ARR 1 29 57 ARR-O3 0.5 16 60 ARR-O3 1 24 72 This result shows that the oxidation (i.e., ozone) transforms the aromaticity of the dissolved organic matter as well as larger humic substances. The SUVA values of various ARR effluents were observed over 12 days of residence time as shown in Figure 2. The pre- (O3-ARR) and post- Ozone (ARR-O3) hybrids showed lower SUVA values than ARR alone while ARR-O3 hybrids yielded the lowest SUVA values. The difference in SUVA was about 1 to 1.5 (Lmg-1m-1) between ARR alone and ARR hybrids. Proportionally, SUVA went down noticeably after eight day of retention time due to a reduction of aromatic humic substance. This may be attributable to refractory DOC of humic/fulvic substance taking longer to degrade than BDOC and/or a potential transformation of humic substances. Figure 2. Specific Ultraviolet Absorbance (SUVA) of Various ARR Effluents LC-OCD-OND-UV254nm was used to characterize the attenuation of bulk organics with respect to their molecular weights ranging from ≈0.1 to ≈20 kDa. Previous work has established categorizing effluent organic matter into major fractions of different sizes and chemical fractions: biopolymers, humic substances, building blocks, low molecular weight organic acids and neutrals, and hydrophobic organic carbon (Huber et al. 2011). With an increased ozone dose, the organic carbon concentration in the biopolymers decreased while the organic carbon concentration in the humics, building blocks, and low-molecular-weight humics and acids fractions increased. Our data agreed with previous studies that large, hydrophobic organic content is transformed into smaller hydrophilic organic content during ozonation (data not shown). In comparison with ARR effluent alone, biopolymers were decreased while humics and building blocks were decreased slightly but a refractory, low-molecular-weight acids component remained fairly constant (Drewes et al. 2006). 3D Fluorescence excitation-emission matrices (F-EEMs) provide an illustrative and sensitive representation of EfOM that could not be captured by other organic parameters such as DOC and UV254nm. F-EEM spectra can be divided into three main regions associated with specific organic fractions indicated in Figure. 3-A. Region 1 represents protein-like fluorescence whereas Region 2 represents fulvic-like fluorescence and Region 3 humic-like fluorescence (Henderson et al. 2009). While ARR alone (Figure 3-B) provided a minimal reduction in both regions of fulvic- and humiclike fluorescence, a substantial decrease of fluorescence in all regions was observed in O3-ARR and ARR- O3 hybrids. Decreases in fluorescence are associated with improvements in water quality; ARR- O3 hybrids shown in Figure 3-E and F, showed even further reduction (close to fluorescence of in Milli-Q) compared to O3-ARR hybrids, shown in Figure 3-C and D. Similar to the reduction in UV254 absorbance and SUVA, ARR-O3 was superior to O3-ARR. Figure 3. Fluorescence Excitation-Emission Matrices (F-EEMs) for: (A) Secondary Effluent Where 1 = Protein-like, 2 = Fulvic-like, 3 = Humic-like Fluorescence, (B) ARR Effluent, (C) O3-ARR Effluent (O3: DOC=0.5), (D) O3-ARR Effluent (O3: DOC=1.0), (E) ARR-O3 Effluent (O3: DOC=0.5), and (F) ARR-O3 Effluent (O3: DOC=1.0) F-EEMs can also quantitatively compare water quality changes in EfOM and associated treatment efficacy. The key peaks and their percent reductions in fluorescence intensity were evaluated as shown in Table 4. While protein-like peaks (e.g., soluble microbial products or biopolymers) were easily degraded, fulvic- and humic-like peaks were not easily degraded in ARR alone. With the benefit of ozone, fulvic- and humic-like peaks were removed in all ARR hybrids. Overall, higher reductions in all three key peaks were observed in ARR-O3 hybrids over O3-ARR hybrids in which (%) reductions were 84% or higher at low ozone dose (O3: DOC=0.5) and 90% or higher at high ozone dose (O3: DOC = 1). Table 4. Key Peaks and Their (%) Reductions in Fluorescence Intensity ARRs O3: DOC (1) Protein-like (2) Fulvic-like (3) Humic-like ARR 0.0 47 % 9% 3% O3-ARR 0.5 75 % 51 % 51 % O3-ARR 1.0 80 % 61 % 60 % ARR-O3 0.5 89 % 84 % 88 % ARR-O3 1.0 93 % 90 % 94 % Trace Organic Contaminant Attenuation The selected TOrCs were categorized as easily biodegradable (i.e., Bisphenol A, Diclofenac, gemfibrozil, ibuprofen, and naproxen), moderately biodegradable (i.e., atenolol, DEET, triclosan, and trimethoprim), and poorly biodegradable (i.e., atrazine, carbamazepine, phenytoin, primidone, meprobamate, sulfamethoxazole, and TCEP), based on their removals under ARR retention times of 3 hrs., 5 days (i.e., 120 hrs.), and 12 days (i.e., 288 hrs.) as shown in Figure 4. This result indicates that the attenuation of TOrCs varies from hours to days, and therefore, specific TOrCs removal can be targeted based upon the residence time of ARR. TOrC oxidation by ozone alone was then monitored for the ARWWTP secondary effluent with both ozone doses, O3 to DOC ratios of 0.5 and 1. Figure 5. illustrates the removal of TOrCs by ozonation alone. The results have shown that TOrCs with their O3 rate constants, kO3 (M-1s-1), higher than 103 were readily removable (> 80%) while TOrCs with their O3 rate constants, kO3 (M-1s-1), equal or lower than 10 were not. As a result, the latter group of TOrCs required a higher ozone dose for a further removal (> 80%). Overall, this result is generally similar with previous bench-scale oxidation data of TOrC for typical secondary effluent. While ozonation provided the fast elimination of TOrCs, biodegradation of poorly degradable TOrCs via ARR requires a long residence time from weeks to months. RT = 3 hrs RT = 120 hrs RT = 288 hrs 1.20 1.00 C/C0 0.80 0.60 0.40 0.20 I. Easily Biodegradable II. Moderately biodegradable Figure 4. TOrC Attenuation by ARR Alone zi rb ne am az ep M in ep e ro ba m at e P tra A Ca TC E yt oi n Pr im Su id lfa on m e et ho xa zo le Ph en T EE D et ho pr im Tr ic lo sa n A te no lo l Tr im Bi sp he no lA D ic lo fe na G c em fib ro zi l Ib up ro fe n N ap ro xe n 0.00 III. Poorly biodegradable 03:DOC=0.5 O3:DOC=1 1.20 kO3 > 103 M-1s-1 kO3 ≤ 10 M-1s-1 1.00 C/Co 0.80 0.60 0.40 0.20 Tr im Ca eth rb opr am im az G epi Su em ne lfa f m ibro et ho zil xa D zol ic lo e fe N nac ap ro x A en t Bi eno sp lol he no Ib l A up ro Ph fen en y Pr toin im id on e M DE ep ro ET ba m a A te tra zi ne TC EP 0.00 Figure 5. TOrC Attenuation by Ozone Alone To investigate the relative contributions of oxidation and biodegradation/sorption to TOrC removal during oxidation-ARR hybrid processes, target TOrC removal by ozonation and/or ARR was compared. Figure 6 shows the percent (%) removal of TOrCs by ARR (RT = 288 hrs.) and ozonation (O3: DOC = 0.5 and1). The additional oxidation provided by an increase in O3: DOC from 0.5 to 1.0 is also illustrated with arrows. This summary figure infers that a majority of the TOrCs can be easily removed by ozone alone or a combination of ozone and ARR. Some of the compounds were resistant to ARR but were susceptible to ozone (carbamazepine, sulfamethoxazole, primidone, and phenytoin), but only DEET proved to be resistant to ozone but moderately susceptible to ARR. Several compounds demonstrated resistance to both ozone and ARR (meprobamate, atrazine, and TCEP). In these treatment hybrids, both ozone doses of O3: DOC = 0.5 vs. O3: DOC = 1 and the short residence times of ARR were strategically combined for potential synergies. Figure 7 compares ARR alone and ARR hybrids for the attenuation of recalcitrant TOrCs (kO3 ≤ 10) and illustrates the impacts of varying ozone dose and hybrid process. All recalcitrant TOrCs showed a further attenuation either or both by the increased ozone dose and post-ozone treatment except for TCEP. TCEP, a flame retardant, was difficult to remove by either the relatively low degrees of ozonation (O3: DOC ≤ 1) or the short term ARR operation (RT = 12 days). Although previous literature suggests that pre-ozonation provides greater potential for cometabolism, post-ozonation (i.e., ARR-O3) achieved lower effluent concentrations for the recalcitrant TOrCs, except for TCEP. Therefore, implementing some form of biological filtration prior to ozonation appears to remove the bioamenable compounds that react rapidly with ozone, thereby reducing oxidant scavenging (demand). This increases the efficacy of downstream ozonation despite similar O3: DOC ratios in both hybrids. O3: DOC = 0.5 % Removal by O3 O3: DOC = 1.0 I II II I IV % Removal by ARR Figure 6. TOrC Removal by ARR (RT = 12 days) and Ozone (O3: DOC = 0.5 or 1) Note: I: O3; II: O3 or ARR; III: ARR; IV: neither Figure 7. Attenuation of Recalcitrant TOrCs (kO3 ≤ 10) with Different Treatment Hybrids TOrCs Behavoir during Abiotic Conditions: Sorption Isotherms Solid-water distribution coefficients (Kd) were calculated based on slopes of linear sorption isotherms over a defined concentration range. Low TOrC concentrations (spiked) in the 0.5-10 μg/L ranges were used to simulate the current ARR process as well as raw municipal wastewaters for many TOrCs. The majority of the isotherms followed a linear regression with correlation coefficients of R2 ≥ 0.95 as shown Table 5. For low sorbing compounds, the data did not fit a linear isotherm and a single point Kd was determined. The results shown that all of the negatively charged compounds, such as diclofenac, ibuprofen, naproxen, phenytoin, sulfamethoxazole, and triclosan, had low Kd values (Kd < 1) except for gemfibrozil, (Kd = 2.81; R2 = 0.98). Two positively charged compounds, atenolol and trimethoprim yielded relatively lower Kd values than expected, 1.09 and 1.76, respectively. This may be due to their low log P values (< 1), which indicate they are more hydrophilic than other positively charged compounds. Overall, Kd values measured in this work were generally 2 to 3 order of magnitudes lower than previously reported Kd values for the sorption potential to wastewater primary and activated sludge solids. However, the abiotic behaviour of these TOrCs seems to follow the relative trends of (higher vs. lower) sorption reported in literature for the sludge solids (Stevens-Garmon et al. 2011). This is perhaps related to the silica sand’s (SiO2 ≥ 96.3%) negatively charged surface, which results in a stronger association occurs between its surface and a positively charged compounds, than with a neutral or a negatively charged compound (Schwarzenbach et al. 2005). Interestingly, all of the easily biodegradable TOrCs (i.e. bisphenol A, diclofenac, gemfibrozil, ibuprofen and naproxen) in ARR, determined earlier, were the compounds with low Kd values, except for gemfibrozil. Thus, the dominant mechanism of TOrC attenuation for the ARR appears to be biodegradation with a possible exception of gemfibrozil. This is particularly important considering that sorption sites will eventually be exhausted in ARR applications after continuous exposure to treated effluent. Table 5. Measured Kd Values Based on Sorption Isotherms Compound Atenolol Atrazine Kd (L/kg) R2 1.09 1.00 2.57 0.99 BPA 0.67 N/A Carbamazepine 1.11 1.00 DEET 3.23 0.97 Diclofenac 0.87 N/A Gemfibrozil 2.81 0.98 Ibuprofen 0.66 N/A Musk Ketone 0.99 N/A Naproxen 0.71 N/A Phenytoin 0.67 1.00 Primidone 1.11 1.00 Sulfamethoxazole 0.68 0.99 TCPP 2.41 0.99 Triclosan 0.74 0.95 Trimethoprim 1.76 0.99 * Kd values in italics are based on single point calculations thus R2 values are not applicable. **Meprobamate was excluded because its analytical standard was unavailable. NDMA Formation and Destruction N-Nitrosodimethylamine (NDMA) is a mutagenic and carcinogenic wastewater by-product that has been found in wastewater effluent even after disinfection/oxidation processes. Due to its demonstrated carcinogenicity, the state of California, USA has recently established a notification limit of 10 ng/L and a response limit of 300 ng/L. Reported concentrations are typically in a range of 5 to 25 ng/L in secondary effluent and higher in primary effluent; with a median of 26 ng/L in the U.S. (Pehlivanoglu-Mantas and Sedlak 2006) and a median of 5 ng/L in Switzerland (Krauss et al. 2009). In our wastewater effluent (Jeddah, Saudi Arabia) with an ambient level of 7 ng/L of NDMA, a slight formation of NDMA was observed with an increase of a total NDMA of 12 ng/L after ozonation (O3: DOC = 1). However, the ARR experiments indicated that NDMA was eliminated in all ARR simulations and its hybrids below its method reporting limit (i.e., < 5 ng/L). The MRL was achieved after 12 days of soil treatment even when NDMA was spiked at ~500 ng/L. This result is also consistent with a previous field study (Zhou et al. 2009). Therefore, ARR is an effective treatment barrier against NDMA and may eliminate the need for UV photolysis or UVAOP in indirect portable reuse (IPR) applications. CONCLUSIONS ARR is a robust and multi-objective process capable of achieving substantial removal of many bulk and trace organic contaminants. The more bioamenable compounds are removed rapidly during soil passage, but more recalcitrant compounds may require long residence times or unique redox conditions. Ozone and oxidation process can eliminate many TOrCs, however ozone generally achieves incomplete oxidation (i.e. limited mineralization), is unable to destroy some compounds (e.g., TCEP), and only transforms other compounds into simpler oxidation by-products. Therefore, ARR is an effective secondary barrier to protect human health against these persistent contaminants. The ARR and isotherm experiments in this study indicated that biodegradation was more significant than sorption during ARR, and these collective processes may also be supplemented with dilution (mixing) in applications that limit recycled water contributions. Therefore, there is potential for significant reductions in TOrC concentrations during ARR with a variety of mechanisms. With respect to the California Department of Public Health regulations for spreading applications, the biodegradation and sorption pathways must achieve at least 90% removal of indicator compounds (e.g., selected TOrCs). Published research indicates that biodegradation of target contaminants is often more efficient and complete in natural ecosystems comprised of diverse microbial communities. There are often complex interactions, feedback, and “communication” between the microbial species that promote degradation pathways. Also, it is often unnecessary to supplement the system with oxygen, organic substrates, or specific microbial species, although exceptions do exist. Thus, nonspecific degradation of TOrC mixtures, which is important in IPR applications, can often be achieved with ambient conditions. For wastewater reclamation and reuse strategies, ARR and oxidation hybrids of ozonation prior to or after a short-term ARR operation showed positive outcomes. Both O3-ARR (i.e., pre-ozonation) and ARR-O3 (i.e., post-ozonation) were more effective than ARR alone in addressing a variety of bulk organics and TOrCs. O3-ARR was superior for overall removal of DOC, while ARR-O3 was more effective in reducing UV absorbance, fluorescence, and TOrC concentrations. Finally, ARR proved to be an effective attenuation strategy for ambient NDMA and any NDMA that formed during ozonation. These results also indicate that the reductions in NDMA during aquifer recharge operation may eliminate the need for UV photolysis or UV-AOP in typical groundwater replenishment treatment schemes (i.e., full advanced treatment). Future research should identify which variables are most critical in terms of TOrC attenuation during ARR or whether travel/storage time alone essentially controls the process. Furthermore, future research should identify strategies to develop engineered aquifer recharge operation to replace natural systems and ultimately eliminate the environmental buffer. This would facilitate the transition from indirect potable reuse to direct potable reuse. REFERENCES Bader, H. and J. Hoigné (1981). "Determination of ozone in water by the indigo method." Water Research 15(4): 449-456. Benotti, M. J., R. A. Trenholm, et al. (2008). "Pharmaceuticals and Endocrine Disrupting Compounds in U.S. Drinking Water." Environmental Science & Technology 43(3): 597-603. Drewes, J. E., D. M. Quanrud, et al. (2006). Character of Organic Matter in Soil-Aquifer Treatment Systems, ASCE. Gerrity, D., S. Gamage, et al. (2011). "Pilot-scale evaluation of ozone and biological activated carbon for trace organic contaminant mitigation and disinfection." Water Research 45(5): 21552165. Henderson, R. K., A. Baker, et al. (2009). "Fluorescence as a potential monitoring tool for recycled water systems: A review." Water Research 43(4): 863-881. Hoppe-Jones, C., G. Oldham, et al. (2010). "Attenuation of total organic carbon and unregulated trace organic chemicals in U.S. riverbank filtration systems." Water Research 44(15): 4643-4659. Huber, M. M., S. Canonica, et al. (2003). "Oxidation of Pharmaceuticals during Ozonation and Advanced Oxidation Processes." Environmental Science & Technology 37(5): 1016-1024. Huber, S. A., A. Balz, et al. (2011). "Characterisation of aquatic humic and non-humic matter with size-exclusion chromatography - organic carbon detection - organic nitrogen detection (LC-OCDOND)." Water Research 45(2): 879-885. Kolpin, D. W., E. T. Furlong, et al. (2002). "Pharmaceuticals, Hormones, and Other Organic Wastewater Contaminants in U.S. Streams, 1999−2000: A National Reconnaissance." Environmental Science & Technology 36(6): 1202-1211. Krauss, M., P. Longrée, et al. (2009). "Occurrence and removal of N-nitrosamines in wastewater treatment plants." Water Research 43(17): 4381-4391. Maeng, S. K. (2010). Mutiple Objective Treatment Aspects of Bank Filtration. Delft, Delft University of technology and of the Academic Board of the UNESCO-IHE Institute for Water Education. DOCTOR: 210. Maeng, S. K., E. Ameda, et al. (2010). "Organic micropollutant removal from wastewater effluentimpacted drinking water sources during bank filtration and artificial recharge." Water Research 44(14): 4003-4014. Pehlivanoglu-Mantas, E. and D. L. Sedlak (2006). "The fate of wastewater-derived NDMA precursors in the aquatic environment." Water Research 40(6): 1287-1293. Rakness, K., G. Gordon, et al. (1996). "Guideline for measurement of ozone concentration in the process gas from an ozone generator." Ozone-Science & Engineering 18(3): 209-229. Schwarzenbach, R. P., P. M. Gschwend, et al. (2005). Sorption III: Sorption Processes Involving Inorganic Surfaces. Environmental Organic Chemistry, John Wiley & Sons, Inc.: 387-458. Stevens-Garmon, J., J. r. E. Drewes, et al. (2011). "Sorption of emerging trace organic compounds onto wastewater sludge solids." Water Research 45(11): 3417-3426. Sundaram, V., Emerick, R.W., Shumaker, S.E. (2009). Field evaluation of MF-Ozone-BAC process train for the removal of microconstituents from wastewater effluent. 24th Annual WateReuse Symposium. Ternes, T. A., M. Meisenheimer, et al. (2002). "Removal of Pharmaceuticals during Drinking Water Treatment." Environmental Science & Technology 36(17): 3855-3863. Trenholm, R. A., B. J. Vanderford, et al. (2006). "Broad range analysis of endocrine disruptors and pharmaceuticals using gas chromatography and liquid chromatography tandem mass spectrometry." Chemosphere 65(11): 1990-1998. Vanderford, B. J., R. A. Pearson, et al. (2003). "Analysis of Endocrine Disruptors, Pharmaceuticals, and Personal Care Products in Water Using Liquid Chromatography/Tandem Mass Spectrometry." Analytical Chemistry 75(22): 6265-6274. Vanderford, B. J. and S. A. Snyder (2006). "Analysis of Pharmaceuticals in Water by Isotope Dilution Liquid Chromatography/Tandem Mass Spectrometry†." Environmental Science & Technology 40(23): 7312-7320. Westerhoff, P., Y. Yoon, et al. (2005). "Fate of Endocrine-Disruptor, Pharmaceutical, and Personal Care Product Chemicals during Simulated Drinking Water Treatment Processes." Environmental Science & Technology 39(17): 6649-6663. Zhou, Q., S. McCraven, et al. (2009). "Field evidence of biodegradation of NNitrosodimethylamine (NDMA) in groundwater with incidental and active recycled water recharge." Water Research 43(3): 793-805.