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4 Water Quality Considerations
Pages 109-180

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From page 109...
... the range of constituents in MUS waters; (2) hydrogeochemical and microbiological processes involved as source waters interact with the native ground water and rocks or sediments comprising the aquifer, and the impact of these processes on MUS performance; and (3)
From page 110...
... In order to establish a sustainable MUS system, constituents that lead to aquifer clogging or dissolution, or other reactions that improve or degrade water quality during MUS operations must also be evaluated. The constituent concentrations that are important for operations are not embodied in a regulatory list, but emerge from consideration of the reactions that can impact MUS performance and the particular type of MUS system (e.g., type of source water, recharge method, native groundwater characteristics, and aquifer geochemistry)
From page 111...
... and particulate organic carbon (POC) and is composed primarily of natural organic matter (NOM)
From page 112...
... Inorganic Constituents Inorganic chemical constituents of concern in MUS source waters can be grouped as nutrients, nonmetals, and metals and metalloids. Nitrogen and phosphorous species are known as nutrients because they are essential for the growth of microorganisms and plants.
From page 113...
... Native Groundwater and Aquifer Geochemistry Native Groundwater Geochemistry and Associated Aquifer Classification Native groundwater quality in an aquifer is important to consider in planning an MUS system because it provides information about constituents likely to dissolve into stored water as it equilibrates with the aquifer matrix. Knowledge of native groundwater quality is also critical to evaluating the potential for chemical reactions occur as recharged and native waters mix in the transition zone.
From page 114...
... trace element concentrations of barium, chromium, copper, lead, nickel, molybdenum, and selenium have a 1.0 to 1.5 percent likelihood of exceeding federal drinking water standards. The authors report that arsenic is an exception, with a 7 percent likelihood of exceeding the federal drinking water standard.
From page 115...
... Regulatory Classification of a Potable Aquifer In addition to the water chemistry-based classification system for aquifers described above, there exist regulatory aquifer classifications that define an aquifer as "potable" or "non-potable" or describe its relative vulnerability to surface sources of contamination. Although aquifers within either classification can be considered for MUS, the regulatory designation may affect operational requirements, particularly source water quality, for the MUS system.
From page 116...
... . Source Waters Differences between the source water and native groundwater lead to reactions during storage that can impact recovered water and either improve or degrade its quality and/or impact MUS performance.
From page 117...
... The case study in Box 4-2 illustrates a situation in Florida where stormwater is being used for groundwater resource augmentation. In addition, stormwater runoff has been used for groundwater recharge on Long Island, New York, and -- mixed with other water types -- in Orange County, California, for many decades.
From page 118...
... they concluded that chemicals such as pesticides, herbicides, and endocrine disruptors, which were not monitored in real-time, required further research to validate that they were either absent or being removed effectively by the pretreatment system. SUBSURFACE PROCESSES THAT AFFECT WATER QUALITY IN MUS SYSTEMS Biogeochemical reactions, including water-rock interactions, that occur during MUS activities are dynamic in both space and time and are a consequence of mixing recharge water with water quality parameters that differ from the native groundwater in the aquifer.
From page 119...
... . Because of the high importance of redox reactions to water quality and aquifer integrity during underground storage, these are described in greater detail than the other reaction types.
From page 120...
... The greatest energy gain is associated with species toward the top of the figure. Changing availability of the terminal electron acceptors PROSPECTS FOR MANAGED UNDERGROUND STORAGE OF RECOVERABLE WATER can result in dynamic spatial and temporal geochemistry.
From page 121...
... Hence, the redox potential of a system depends on the type and quantity of available degradable organic matter and electron acceptor. For example, if the amount of degradable organic matter exceeds the available dissolved oxygen, which is a common occurrence in groundwater, then the system will become denitrifying if nitrate is available to be used as an electron acceptor.
From page 122...
... For example, oxidation of organic matter creates acid products (partially transformed organic acids or carbonic acid) that chemically weather the aquifer media by dissolving the minerals in the aquifer.
From page 123...
... The impact of different chemical conditions in the aquifer on contaminant fate is illustrated by the contrasting behavior of THMs in two aquifer storage and recovery (ASR) tests conducted with different redox conditions: conditions were dominantly aerobic during recharge and storage in the Yakima, Washington, pilot test, while anaerobic conditions (nitrate reducing to methanogenic)
From page 124...
... . The authors of this study point out that although DBPs were formed during the first week of aquifer storage, their long-term behavior was controlled by degradation reactions that are reasonably fast compared to typical storage cycles.
From page 125...
... WATER QUALITY CONSIDERATION 125 A B continues next page
From page 126...
... TOC and residual chlorine, and (C) selected and total THMs in the Yakima, Wash., ASR pilot study.
From page 127...
... compared to the observation well, and (b) where nitrate reducing conditions were observed.
From page 128...
... . Dissolution reactions are favored when recharged waters contain relatively low dissolved ion concentrations compared to the native groundwater, which is frequently the case for surface water sources.
From page 129...
... and Herczeg and colleagues (2004) are among the researchers that provide more detail on the effects of these geochemical processes during aquifer storage and recovery (ASR)
From page 130...
... In such tests, the source water and aquifer solids may remain farther from equilibrium than they would be during full-scale operations. Therefore, such tests must be conducted and interpreted such that extrapolation to a longer-duration and larger-scale system appropriately accounts for sorption/desorption dynamics.
From page 131...
... This process can also significantly affect the dissolved concentrations of trace metal cations. Particle and Microorganism Transport The movement and fate of particles and microorganisms that may be in source waters for MUS systems is of interest.
From page 132...
... in contrast may enhance microbial transport through porous media. Solute characteristics including ionic strength, pH, temperature, concentrations of dissolved organic matter, surfactants, and nutrients have also been shown to influence particle and microorganism transport and adhesion to surfaces.
From page 133...
... Influenced by temperature, nutrients, and aerobic conditions, increased activity generally enhances inactivation rates of fecal organisms. Enteric microorganisms of wastewater origin have been the predominant focus of studies on survival in groundwater with temperature the predominant variable studied.
From page 134...
... (log10d−1) Decline Deviation Groundwater Avon 5 0.0088 >200 Park Aquifer 22 −0.0010 >200 30 −0.11 18 Groundwater Lake 5 0.00090 >200 Lytal Aquifer 22 −0.042 48 30 −0.12 17 Surface water Bill Evers 5 −0.0017 >200 Reservoir 22 −0.045 45 30 −0.20 10 Surface water Clear Lake 5 −0.0037 >200 Reservoir 22 −0.0066 30 30 −0.18 11 Groundwater Avon 5 >200 0 Park andLake 22 124 107 Lytal Aquifer 30 17.5 0.71 Surface water Bill Evers 5 >200 0 and Clear 22 37.5 10.6 Lake 30 10.5 0.71 Reservoir SOURCE: Ives et al.
From page 135...
... FIGURE 4-4 Mean inactivation rates of bacteria (a) and viruses (b)
From page 136...
... These alternate electron acceptors are reactants in anaerobic microbial processes. Microbial reactions in MUS systems can contribute to changes in redox conditions within the storage zones.
From page 137...
... BEHAVIOR OF SELECTED CONTAMINANTS IN MUS SYSTEMS Empirical and experimental evidence from established MUS systems demonstrates that water quality objectives can be met consistently by underground storage systems over long periods of time -- decades. In some of these systems, especially those that use recharge basins, subsurface treatment removes a portion of the contaminants in the source water, thus the subsurface recharge and storage system plays an integral role in improving water quality.
From page 138...
... Given sufficient surface area and contact time, the water used for underground storage may approach the quality of native groundwater with respect to DOC concentration. The transformation of organic compounds during recharge may be divided functionally into two regimes defined as short-term transformations, wherein relatively fast reactions occur, and long-term transformations, wherein recalcitrant compounds transform at slower rates over time.
From page 139...
... After several years of travel time, the DOC concentrations were less than 1 mg/L as they approached the background concentrations of the aquifer. At this field site, the organic matter was also characterized in detail to allow comparison between the DOC composition and structure in the final product of a groundwater recharge system and the NOM present in the original drinking water source, Samples representative of reclaimed water before groundwater recharge, after short-term subsurface transformations, and after long-term subsurface transformations were analyzed.
From page 140...
... (b) FIGURE 4-5 Dissolved organic carbon concentrations at the Mesa Northwest Water Reclamation Plant as a function of (a)
From page 141...
... , as well as in the treatment process. Because the DBP formation potential is affected by the concentration and composition of the DOC, DBP formation varies both among aquifer storage systems and with source water quality changes for a particular storage system (Pavelic et al., 2006)
From page 142...
... Limited controlled laboratory studies support the interpretation that biotransformation is the primary mechanism by which HAA concentrations are attenuated during aquifer storage. Studies using either tri- or monochloroacetic acid showed that HAAs can be used as both a carbon and an energy source by cultured microorganisms (McRae et al., 2004; Torz and Beschkov, 2005)
From page 143...
... For example, in an aquifer storage system with degradable DOC and solids containing available iron oxide minerals (such that iron reducing conditions are dominant over methanogenic conditions) , chloroform persistence is expected while more brominated THMs are likely to be transformed.
From page 144...
... The research focused on the use of reclaimed water as source water to recharge basins (United States) and the use of sewage-contaminated surface waters in bank filtration systems (Europe)
From page 145...
... The behavior of selected trace organics during underground storage was studied to identify and quantify processes that affect organic contaminant attenuation during subsurface transport. Initial research activities focused on the fate of the following compounds at micro gram-per-liter concentrations in source water: clofibric acid, surfactants such as alkylphe nolethoxylates, DBPs, nitrilotriacetic acid (NTA)
From page 146...
... . Another field example showing attenuation of PPCPs during infiltration and storage is from the Tucson Underground Storage and Recovery Facility.
From page 147...
... These compounds have been demon strated to accumulate in the upper soil layers of recharge basins; however, the adsorbed compounds are biodegraded and their accumulation levels appear to reach a steady concentration with no risk of breakthrough. 3380 6280 150 diclofenac fenoprofen ibuprofen 120 ketoprofen naproxen 90 80 ng/L 60 45 35 30 20 n.d.
From page 148...
... Because NDMA is light- sensitive, sunlight may reduce its concentrations in recharge basins prior to subsurface transport. Both aerobic and anaerobic microbial mineralization of NDMA has been observed in soils obtained from recharge basins, and these mechanisms may be a substantial component of NDMA attenuation in soils underlying groundwater recharge facilities.
From page 149...
... Arsenic speciation and dissolved concentrations depend on geochemical conditions, including redox conditions, pH, organic matter content, the presence of iron oxides, ions that compete for adsorption sites, solution composition, aquifer mineralogy, and reaction kinetics (Nordstrom, 2002; Smedley and Kinniburgh, 2002; Welch et al., 2000)
From page 150...
... water and in situ native groundwater and interaction with the aquifer matrix. Field testing has elucidated the dynamics of arsenic release from the aquifer, and complementary laboratory work has identified the solid phases containing arsenic (e.g., pyrite; see Box 4-7)
From page 151...
... . Case Studies with Microorganisms Recent studies have been undertaken on the resistant protozoan Cryptosporidium in native surface waters and groundwaters that were being used for aquifer storage and recovery in Florida.
From page 152...
... Molecular tools for environmental microbial assays are still under development but have promising capabilities for the next generation. Although current water quality standards and guidelines are based on indicator microbes along with a few pathogens for drinking water, there is little effort to apply these new techniques for better assessment of surface, ground, and MUS waters.
From page 153...
... WATER QUALITY CONSIDERATION 153 Average results of two experiment 0 0 30 60 90 120 150 180 210 240 270 300 CFU & M PN PCR Log -1 -2 CFU n t/ n o -3 MPN PCR -4 -5 -6 Time in hr at 4 O C Average results of two experiment 0 0 30 60 90 120 150 180 210 240 270 300 CFU & M P N P CR Log -1 -2 CFU n t/n o -3 MPN PCR -4 -5 -6 Time in hr at 15 O C FIGURE 4-10 Use of molecular techniques compared to cultivation for characterization of Helicobacter in groundwaters. Reprinted, with permission, from Nayak and Rose (2007)
From page 154...
... Clogging depends on the interactions among aquifer, source, and receiving water properties and on operational variables, including aquifer matrix properties (e.g., effective porosity, lithology, mineralogy, cation exchange capacity) , source and native groundwater quality (e.g., redox conditions; dissolved metals, carbon, and other nutrients)
From page 155...
... Calcite mineral dissolution can occur as an acid neutralization reaction in response to elevated acid concentrations created by the source water through either degradation of organic matter in the source water that increases the carbonic acid concentration or oxidation of aquifer sulfide minerals by dissolved oxygen in aerobic source water that produces sulfuric acid. In any of these cases, permeability of the aquifer matrix may increase over time.
From page 156...
... In recognition of the conditioning process, the South Australia Environment Protection Authority (2004) Code of Practice for Aquifer Storage and Recovery allows for designation of an attenuation zone (see also "Travel Time or Residence Time Criteria" Chapter 5)
From page 157...
... As a result, a combination of laboratory and field-scale assessments,2 coupled with geochemical modeling, yields a more robust and applicable characterization of the overall MUS system in the context of biological, hydrogeological, and hydrochemical processes. Batch and Column Scale Studies Laboratory experiments can identify potential changes in water quality and permeability at the field scale.
From page 158...
... . During ASR, for example, the native aquifer storage zone is often a hydrochemically reducing environment: low dissolved oxygen concentrations and negative oxidation-reduction potential.
From page 159...
... Figure 4-11 summarizes results of the bench-scale leaching study that exposed the aquifer solids to native groundwater (phase 1) , followed by source water (phase 2)
From page 160...
... Depending on subsequent redox conditions, arsenic is favored to be mobilized or demobilized in association with iron (although not in stoichiometric proportions)
From page 161...
... ; (b) electron probe microanalysis element maps and a corresponding backscatter electron image show elevated arsenic associated with framboidal pyrite (iron sulfide)
From page 162...
... Among the factors that can transfer results from lab-scale studies directly to the field are temperature, pressure, sediment compaction, lack of representative samples or conditions, redox conditions, water-rock surface area ratio, variability in source water composition, source water-groundwater mixing,
From page 163...
... Results of these studies may be used as inputs or validation for geochemical models and, most importantly, serve as a tool to screen potential water quality issues associated with MUS. Comprehensive Methods for Examining Water and Aquifer Media as a Precursor to Geochemical Modeling Advances in analytical techniques have made it possible to obtain relatively inexpensive broad-spectrum chemical analyses of inorganic constituents in rock, sediment, and water samples.
From page 164...
... , specifically with regard to ASR include characterization of (1) mixing between native groundwater and recharge water during cycle testing; (2)
From page 165...
... Parameter inputs include major water chemistry constituents, trace metals, radionuclides, organic pollutants, and pathogens. Easy-Leacher calculates water quality changes in MUS systems, including recharge basins and changes reflected in hydrochemical fronts due to aquifer matrix leaching.
From page 166...
... • Numerical model: PHT3D is a three-dimensional advective-dispersive multicom ponent reactive transport model used in this study. The model couples a three dimensional transport simulator (MT3DMS; Zheng and Wang, 1999)
From page 167...
... Temporal variations in source water composition were reflected in the model; and both native groundwater and seasonal recharge waters were charge-balanced through minimal (<5 percent) adjustment of the chloride concentration.
From page 168...
... 168 PROSPECTS FOR MANAGED UNDERGROUND STORAGE OF RECOVERABLE WATER BOX 4-8 Continued FIGURE 4-14 Measured and simulated breakthrough curves of oxygen and nitrate at 8-m (WP3)
From page 169...
... It is important to establish whether the mixing of source water and native groundwater, as well as chemical interaction with aquifer materials, yields compatible and acceptable effects on water quality. Recommendation: A thorough program of aquifer and source water sampling, combined with geochemical modeling, is needed for any MUS system to understand and predict the medium- and long-term chemical behavior and help determine the safety and reliability of the system.
From page 170...
... In addition, this information will help reduce impediments to public acceptance of a wide variety of source waters for MUS. Conclusion: In particular, changes in reduction-oxidation (redox)
From page 171...
... 2007. Aquifer storage and recov ery in Florida: Geochemcial assessment of potential storage zones.
From page 172...
... 1989. Effect of water depth in groundwater recharge basins on infiltration.
From page 173...
... 2005. Water Quality Improvements During Aquifer Storage and Recovery.
From page 174...
... 2001. Effects of clay dispersion on aquifer storage and recovery in coastal aquifers.
From page 175...
... 2006. Geochemical Models of Water-Quality Changes During Aquifer Storage Recovery (ASR)
From page 176...
... 2005b. Fate of disin fection by-products in groundwater during aquifer storage and recovery with reclaimed water.
From page 177...
... 2006. Comparative evaluation of the fate of disinfection byproducts at eight aquifer storage and recovery sites.
From page 178...
... 2000. The fate of haloacetic acids and trihalomethanes in an aquifer storage and recovery program, Las Vegas, Nevada.
From page 179...
... 2005. Geochemical transformation of trichloroacetic acid to chloroform in fresh waters -- The results based upon laboratory experiments.


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