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Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
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3

Water Quality

The wastes discharged into municipal wastewater collection systems include a wide range of biological, inorganic, and organic constituents. Some of these constituents can be harmful to persons and/or ecosystems depending on concentration and duration of exposure (see also Chapter 6 for a discussion of risk in the context of hazards and exposure types). Some are essential nutrients at low concentrations (e.g., certain trace elements), but may become hazardous at higher concentrations. In this chapter the committee briefly describes the key water quality constituents of concern when municipal wastewater is reused or when treated municipal wastewater is discharged to a watercourse that is later used as a source of municipal water supply. Because water reuse involves multiple potential applications (see Chapter 2, Table 2-2), the constituents of concern depend upon the final use of the water. For instance, some constituents in drinking water that may affect human health may not be of concern in certain landscape irrigation or industrial applications where risk to human health from incidental consumption is negligible. Other constituents may have an adverse impact on aquatic species but no adverse impact on human health at the same concentration. It is also important to remember that the occurrence and concentration of these chemicals and microorganisms are likely to vary from one location to another, with the treatment methods applied, and according to post-reclamation storage and conveyance practice. Depending on the reuse application, these constituents may need to be addressed to differing degrees in water reuse system designs (see Chapters 4 and 5), considering that individual contaminants pose different hazards in one context than they do in another and their associated risks depend on the dose and paths of exposure (see Chapter 6). Although the committee provides examples below for a diversity of potential pathogens and chemical contaminants in reclaimed water, it is important to keep in mind that there are often other sources of exposure (e.g., food, distribution system failures, household products) that are not discussed here.

PATHOGENS

Wastewater contains many microorganisms but only a subportion of the organisms are potential human health hazards, notably enteric pathogens. Classes of microbes that can cause infection in humans include helminths (wormlike parasites), parasitic protozoa, bacteria, and viruses. Some microorganisms are obligate pathogens (i.e., they must cause disease to be transferred from host to host), whereas others are opportunistic pathogens, which may or may not cause disease. In the United States, the enteric protozoa Cryptosporidium and Giardia, the enteric bacteria Salmonella, Shigella, and toxigenic Escherichia coli O157:H7, and the enteric viruses enteroviruses and norovirus are the most frequently documented waterborne enteric pathogens (Craun et al., 2006). They cause acute gastrointestinal illness and have the potential to create large-scale epidemics. Table 3-1 lists the microbial agents that have been associated with waterborne disease outbreaks and also includes some agents in wastewater thought to pose significant risk.

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

TABLE 3-1 Microbial Agents of Known Hazard Via Water Exposures

Agent Associated Illnesses
Viruses
   • Noroviruses Gastroenteritis
   • Adenoviruses Conjunctivitis, gastroenteritis, respiratory disease, pharyngoconjunctival fever
   • Coxsackieviruses Meningitis, pharyngitis, conjunctivitis, encephalitis
   • Echoviruses Gastroenteritis, encephalitis, meningitis
   • Hepatitis A virus Hepatitis
   • Astroviruses Gastroenteritis
Bacteria
   • E. coli O157 Hemorrhagic diarrhea
   • Campylobacter jejuni Campylobacteriosis
   • Salmonella Salmonellosis
   • Shigella Shigellosis
   • Vibrio Gastroenteritis, wound infection
   • Legionella Legionellosis
Protozoa
   • Cryptosporidium Cryptosporidiosis
   • Giardia Giardiasis
   • Microsporidia Microsporidiosis

NOTE: These agents are known to be present in treated wastewaters or surface water and therefore are considered to be potentially present in waters used for the production of reclaimed water.
SOURCE: Asano et al. (2007).

The occurrence and concentrations of microbial pathogens in reclaimed water depend on the health of the tributary population and the applied wastewater treatment processes (see Table 3-2). Primary and secondary treatment (see Chapter 4) attenuate microbial pathogens but do not eliminate them. For pathogenic bacteria, viruses, and protozoa that can cause acute diseases with even a single exposure, additional physiochemical treatment processes (discussed in Chapter 4) may be required to achieve acceptable levels of removal or inactivation, depending on the beneficial use.

Helminths

Often known as parasitic worms, helminths pose significant health problems in developing countries where wastewater reuse is practiced in agriculture using raw sewage or primary effluents (Shuval et al., 1986). The World Health Organization (WHO) has pointed to the need to study the transmission of intestinal parasites, particularly nematodes, in children living in areas where untreated wastewater is used for vegetable irrigation (WHO, 1989). Human exposures to helminths are mainly through ingestion of helminth eggs in food or water contaminated with untreated wastewater or sewage-derived sludge, and these exposures can cause acute gastrointestinal illness. There are over 100 different types of helminths that can be present in sewage, although the number of helminth eggs in untreated wastewater is typically much higher in developing countries than in developed countries. The concentration of helminth eggs can range from <1 to >1,000 per 0.3 gallon (1.0 L) of sewage, depending on the source of sewage (Jiménez, 2007; Ben Ayed et al., 2009). Helminth eggs can be largely removed through

TABLE 3-2 Reported Ranges of Reclaimed Water Quality for Key Water Quality Parameters After Different Degrees of Treatment

Constituent Units Untreated Wastewater Range of Effluent Quality After Indicated Treatment
Conventional Activated Sludge (CAS) CAS with Filtration CAS with Biological Nutrient Removal (BNR) CAS with BNR and Filtration Membrane Bioreactor (MBR)
Total suspended solids (TSS) mg/L 120-400 5-25 2-8 5-20 1-4 <2
Total organic carbon (TOC) mg-C/L 80-260 10-40 8-30 8-20 1-5 0.5-5
Total nitrogen mg-N/L 20-70 15-35 15-35 3-8 2-5 <10a
Total phosphorus mg-P/L 4-12 4-10 4-8 1-2 ≤2 <0.3b-5
Turbidity NTU 2-15 0.5-4 2-8 0.3-2 ≤1
Volatile organic compounds (VOCs) μg/L <100->400 10-40 10-40 10-20 10-20 10-20
Trace constituents μg/L 10-50 4-40 5-30 5-30 5-30 0.5-20
Total coliforms No./100 mL 106-109 104-105 103-105 104-105 104-105 <100
Protozoan cysts and oocysts No./100 mL 10-104 10-102 0-10 0-10 0-1 0-1
Viruses PFU/100 mL 10-104 10-103 10-103 101-103 10-103 1-103

NOTE: None of the treatments in the table include disinfection.

aWith anoxic zone.

bWith coagulant.

SOURCE: Asano et al. (2007).

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

secondary treatment supplemented by finishing ponds or filtration and disinfection (Blumenthal et al., 2000).

Protozoa

Protozoa are single-celled eukaryotes that are heterotrophic and generally larger in size than bacteria. Some protozoa are mobile using flagella, cilia, or pseudopods, whereas others are essentially immobile. Malaria, probably the best-known disease caused by protozoa, is caused by the genus Plasmodium. In U.S. water systems, Giardia lamblia, Cryptosporidium parvum, and C. hominis have been associated with gastrointestinal disease outbreaks through contaminated water. In 1993, an outbreak of cryptosporidiosis caused an estimated 400,000 illnesses and more than 50 deaths through contaminated drinking water in Milwaukee, Wisconsin (Mac Kenzie et al., 1994; Hoxie et al., 1997). Part of the protozoan life cycle often involves spores, cysts, or oocysts, which can be highly resistant to chlorine. Cryptosporidium oocysts and Giardia cysts of human origin are frequently detected in secondary wastewater effluent (Bitton, 2005), and these may still persist in disinfected effluent after granular media or membrane filtration (e.g., Rose et al., 1996). Thus, in potable reuse applications, additional treatment processes (see Chapter 4) are needed to reduce the risk of infection from Cryptosporidium and Giardia.

Bacteria

Bacteria are single celled prokaryotes and are ubiquitous in the environment. However, domestic wastewaters contain many pathogenic bacteria that are shed by the human population in the sewershed. Particularly important are pathogenic bacteria that cause gastroenteritis and are transmitted by fecal-oral route (enteric bacterial pathogens). From 1970 to 1990, enteric bacteria were estimated to account for 14 percent of all waterborne disease outbreaks in the United States between 1971 and 1990 (Craun, 1991) and 32 percent between 1991 to 2002 (Craun et al., 2006). Based on hospitalization records, the most severe bacterial infections result from E. coli (14 percent), Shigella (5.4 percent), and Salmonella (4.1 percent) (Gerba et al., 1994).

Because of the public health significance of bacterial pathogens, monitoring systems and water quality standards have been established based on fecal coliforms (a classification that includes E. coli) and enterococcus in the United States and in many nations around the world (NRC, 2004). It is important to note that most E. coli and enterococcus are not pathogenic. Rather they are part of the normal microflora in the human digestive tract and are necessary for proper digestion and nutrient uptake. E. coli and enterococcus are employed as indicators of the presence of human waste (also called fecal indicator bacteria) in water quality monitoring and protection because they are present in high concentrations in human feces and sewage and they are more persistent than most bacterial pathogens. They are, therefore, used to indicate inadequate treatment of sewage to remove bacterial pathogens (NRC, 2004). Fecal indicator bacteria in undisinfected secondary effluent range from 102 to 105/100 mL depending on the quality of the influent water (Bitton, 2005). However, the concentration of fecal indicator bacteria (i.e., total coliform, fecal coliform, enterococcus, and E. coli) in filtered, disinfected secondary effluent can be brought below the nominal detection limit of 2.2 organisms/100 mL and with advanced treatment, they can be brought even lower.

Viruses

Viruses are extremely small infectious agents that require a host cell to replicate. They are of special interest in potable reuse applications because of their small size, resistance to disinfection, and their low infectious dose. There are many different viruses, and they infect nearly all types of organisms, including animals, plants, and, even bacteria. Aquatic viruses can occur at concentrations of 108 to 109 per 100 mL of water in the ocean (Suttle, 2007) and 109 to 1010 per 100 mL in sewage (Wu and Liu, 2009); however, most of these are bacteriophages—viruses that infect bacteria. The viruses of concern in water reuse or in the discharge of treated wastewater to drinking water sources are human enteroviruses (e.g., poliovirus, hepatitis A), noroviruses (i.e., Norwalk virus), rotaviruses, and adenoviruses. Human viruses are usually present in undisinfected secondary effluent and may still persist in effluents after some advanced treatment (e.g., Blatchley et al., 2007; Simmons and Xagoraraki, 2011). Fecal indicator bacteria that are currently used for water quality monitoring are not an adequate indication of the presence or absence of viruses because bacteria are more efficiently

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

removed or inactivated by some wastewater treatment processes than are enteric viruses (Berg, 1973; Harwood et al., 2005). Thus, viruses need to be carefully addressed whenever treated municipal wastewater is discharged or reused in a context where there may be human contact, particularly when it makes up all or part of a drinking water supply.

Prions

A prion is an infectious agent that is primarily a protein. The prion causes a morphological change to native proteins, which can, in turn, lead to disease symptoms. The best-known example of prion-based disease is bovine spongiform encephalopathy (“mad cow disease”). In animals, prions can cause a variety of diseases including scrapie and chronic wasting disease (CWD); however, the spectrum of cross transmission of different prion agents is not clear. It has been demonstrated that CWD can be transmitted to animals by direct oral ingestion of prion-containing animal tissue (Mathiason et al., 2009). It has not been demonstrated that prions can be transmitted by the ingestion of drinking water, and their occurrence in water is poorly understood.

Currently, sparse data exist on the occurrence of prions outside of animal flesh or on the fate of prions in water or wastewater treatment. Prions are thought to substantially partition into the sludge during biological wastewater treatment, although according to a pilot study reported by Hinckley et al. (2008), some remain in effluent. Nichols et al. (2009) developed an analytical technique for measuring prions in water and environmental samples. Using this assay they reported detection of prions in one of two surface water samples in an area known to be endemic for CWD. They also reported detection of prions from water drawn from the flocculation stage of a water treatment plant using this source, but none in the water in subsequent stages of treatment.

INORGANIC CHEMICALS

Wastewater contains a variety of inorganic constituents including metals, oxyhalides, nutrients, and salts. Generally, aggregate measures of inorganic constituents in water are total dissolved solids (TDS) and conductivity, although both TDS and conductivity measurements may include contributions from some organic constituents. Because human and industrial activities consistently increase the TDS in water, the reuse of water will increase the TDS in the water supply.

Metals and Metalloids

Metals and metalloids, such as lead, mercury, chromium, arsenic, and boron, can result in adverse effects to human health when consumed in excessive amounts. However, regulatory statutes and industrial pretreatment regulations promulgated through the Clean Water Act specifically target toxic metals and, as a result, most municipal effluents have concentrations of toxic metals below public health guidelines and standards. Therefore, toxic metals in contemporary treated domestic wastewaters in the United States do not generally exceed human health exposure.

Boron (a metalloid) occurs in domestic wastewater, most likely resulting from its use in household products such as detergents (WHO, 2009). However, boron typically is not an issue for water reuse systems because concentrations are generally less than 0.5 mg/L (Asano et al., 2007), although in certain unique geologies or coastal communities boron can be elevated. Boron is of particular interest because no removal occurs during conventional biological treatment, and even advanced water treatment processes (i.e., reverse osmosis) are not highly effective at ambient pH. Although boron is not regulated in drinking water in the United States, the U.S. Environmental Protection Agency (EPA) published a health advisory level of 7 mg/L for adults and a level of 3 mg/L for 10-kg children (EPA, 2009b). Similarly, WHO has established a human health guideline for boron of 2.4 mg/L (WHO, 2009). Thus, typical boron levels in domestic wastewaters are well below drinking water guidelines.

There are many ornamental plants, however, that are more sensitive to boron (Tanji et al., 2008). Although boron is essential for plant growth and development, it can be toxic to plants at concentrations above 0.5 to 1 mg/L (Brown et al., 2002). In some settings, boron may place limits on the types of plants that can be successfully irrigated with reclaimed water.

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

Salts

The reuse of water generally increases the concentration of dissolved salts because of significant contributions of various salts through municipal and industrial water uses. In general, the levels of salts as measured as TDS do not exceed thresholds of concern to human health; however, excess salt concentrations can result in aesthetic concerns (i.e., unpalatable water) as well as agricultural and infrastructure damage. Certain salts in elevated concentrations can lead to scaling and corrosion issues. Calcium and magnesium concentrations are primarily responsible for hardness, and excess levels can cause damage to household appliances and industrial equipment (Hudson and Gilcreas, 1976). In service areas with elevated hardness, households commonly employ ion exchange–based water softeners as a local remedy for “hard water,” but these units significantly increase the total salinity of the wastewater, particularly chloride. High levels of chloride are of concern because these ions exacerbate the corrosion of metals and reinforced concrete (Crittenden et al., 2005; Basista and Weglewski, 2009). The U.S. Bureau of Reclamation estimated in 2004 that excess salinity in the Colorado River caused more than $300 million per year in economic damages in the United States (U.S. Bureau of Reclamation, 2005).

Excess salinity can also be detrimental to plant growth (Tanji et al., 2008; Goodman et al., 2010). High sodium and chloride concentrations in reclaimed water used for irrigation can cause leaf burn, and high sodium concentrations can also reduce the permeability of clay-bearing soils and adversely affect the soil structure. The suitability of a water source for irrigation can be assessed by the electrical conductivity and the sodium adsorption ratio (SAR), a calculated ratio of sodium to calcium and magnesium ions;1 the higher the electrical conductivity and the SAR, the less suitable the water is for use in irrigation. Therefore, careful control of salts and salt compositions is critical to water reuse, with specific limits dictated by end-use applications (i.e., irrigation vs. potable).

Salinity control is quite challenging because treatment options are limited and costly and because significant residuals are produced. Virtually all processes employed for salinity reduction result in a concentrated liquid waste (brine), which must subsequently be disposed (see also Chapter 4).

Oxyhalides

Oxyhalides are anionic salts consisting of a halogen covalently bonded to one or more oxygen atoms. In water reuse, the primary oxyhalides of concern are bromate, chlorite, chlorate, and perchlorate. Bromate is of primary concern when water containing bromide is ozonated, because its maximum contaminant level (MCL) is 10 µg/L and EPA has been made it clear it will seek even lower levels when feasible (EPA, 2006b). Sodium hypochlorite, commonly known as bleach, can contain elevated levels of bromate, chlorate, and perchlorate, depending upon the manufacturing and storage conditions (Asami et al., 2009).

Neither chlorate nor perchlorate is currently regulated under EPA’s primary drinking water standards, although both are included on EPA’s Contaminant Candidate List 3. Additionally, the state of California has established a notification level of 800 µg/L for chlorate and an enforceable MCL of 6 µg/L for perchlorate. Excess exposure to chlorate and perchlorate can result in inhibition of iodide uptake, resulting in decreased production of thyroid hormones (Snyder et al., 2006b). Chlorate is generally associated with the decomposition of bleach, where bleach age and handling procedures greatly influence the degree of chlorate formation (Gordon et al., 1997).

Perchlorate as a water contaminant is generally associated with anthropogenic activities, including solid propellants for missiles and spacecraft, flares, and fireworks (Urbansky, 2000). More recent data have demonstrated that perchlorate also is found in bleach, with the concentration dependent primarily upon bleach storage conditions and age (Snyder et al., 2009). Although, there is no federal regulation for perchlorate in drinking water, several states have promulgated enforceable regulations, with Massachusetts having the most stringent standard at 2 µg/L (Pisarenko et al., 2010). Perchlorate has been demonstrated to accumulate in certain plants (Sanchez et al., 2005);

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1 SAR = [Na+]/{([Ca2+] + [Mg2+])/2}1/2, where the concentrations are provided in milliequivalents per liter.

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

therefore, irrigation of food crops with reclaimed water containing elevated levels of perchlorate could result in elevated levels of perchlorate in certain food products. However, perchlorate also is naturally occurring as the result of formation in the atmosphere and subsequent deposition with rainfall (Dasgupta et al., 2005), thus complicating investigations of perchlorate bioaccumulation from natural versus artificial irrigation. Water reuse practitioners employing ozonation should be aware of the potential for bromate formation, and those using bleach should be cautious purchasing and storing bleach, to avoid excess chlorate and perchlorate formation. As in drinking water treatment, with the exception of perchlorate, the oxyhalide problem is not so much a problem of source water quality but one that requires proper design and operation of treatment facilities to minimize their formation during treatment. Among the processes that are employed in conventional drinking water treatment and in advanced wastewater treatment, oxidation and disinfection processes are those that have the greatest potential for creating oxyhalides. Disinfection is especially important in potable reuse projects; therefore, the formation of oxyhalides will be a key consideration in process train selection and design.

Nutrients

Human waste products are rich in nitrogen and phosphorus, and the human body metabolizes and excretes both phosphorus and nitrogen in various forms. The primary forms of nitrogen in wastewater effluent are ammonia, nitrate, nitrite, and organic nitrogen. Phosphorus also occurs in wastewater mainly in inorganic forms. These nutrients can pose environmental concerns but also carry potential benefits to nonpotable water reuse applications that involve irrigation. Elevated nitrate in drinking water can also present public health issues, especially in infants. To protect human health, EPA established an MCL in drinking water of 10 mg (as N)/L for nitrate and 1 mg (as N)/L for nitrite.2

Therefore, the need for removal of nutrients during treatment of wastewater for subsequent reuse depends largely on the intended use of the produced water. In water reuse for irrigation, the presence of nitrogen and phosphorus are generally beneficial and promote growth of plants or crops. However, ammonia, particularly in its un-ionized form (i.e., as NH3), is highly toxic to fish; therefore, wastewater discharges to surface waters generally are regulated to prevent excess ammonia release. Ammonia can reach levels of 30 mg/L in secondary treated effluents; however, ammonia can be oxidized to nitrite and further to nitrate by aerobic autotrophic bacteria during wastewater treatment. Although the nitrification process leads primarily to nitrate, water reuse facilities often also denitrify to reduce nitrate levels, converting nitrate to nitrite and ultimately to nitrogen gas. When nitrogen is not removed, it is usually present at levels that are above the EPA MCL for nitrate (as N). This can be a concern because in the natural environment, all forms of nitrogen in effluent are generally transformed to nitrate.

Although reclaimed water is frequently desirable for irrigation, excess irrigation can lead to nutrient contamination of underlying aquifers and of surface waters through runoff. An additional concern for nutrients in reclaimed water stored or reused in ponds, lakes, or streams arises from eutrophication wherein excess nitrogen and phosphorus stimulate the rapid growth of algae, which can cause problems including a depletion of oxygen concentrations in water, alteration of the trophic state of the system, impairment of the operation of drinking water treatment plants, and production of compounds that affect taste and cause odors in drinking water. The processes for management of nitrogen in wastewater treatment are now well-understood (Tchobanoglous, 2003). As a consequence the challenge is matching the appropriate treatment with the intended use and assessing the affordability of the project.

Engineered Nanomaterials

Nanomaterials are generally considered to be materials with at least one dimension from 1 to 100 nm (Jiménez et al., 2011). Nanomaterials exhibit this geometry in one dimension (i.e., nanofilms), two dimensions (i.e., nanotubes, nanowires), or three dimensions (i.e., nanoparticles). Nanoscale particles are not new to the water and wastewater field. Many natural subcolloidal particles in this range, including viruses

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2 See http://water.epa.gov/drink/contaminants/index.cfm. Additionally, WHO (2011) set a guideline value of 11 mg/L nitrate as N (or 50 mg/L as nitrate) and 1 mg/L nitrate as N (or 3 mg/L as nitrite).

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

and natural organic matter (Baalousha and Lead, 2007; Song et al., 2010), have been dealt with for decades in water and wastewater treatment. More recent examples of natural nanoscale particles include oxidation products of manganese, iron, and perhaps lead (Lytle and Snoeyink, 2004; Lytle and Schock, 2005). However, the purposeful manufacturing of nanoscale materials (called engineered nanomaterials) for consumer products is rapidly increasing.3 Because nanoscale particles have an extraordinary surface-to-volume ratio, they are of interest in many applications where surface chemistry or catalysis is important (Weisner and Bottero, 2007). Potential applications of nanotechnology in the environmental industry itself are also evolving (Savage and Diallo, 2005; Chong et al., 2010; Pendergast and Hoek, 2011). As a result, many new questions have emerged about the fate of engineered nanomaterials when released to the environment.

Engineered nanomaterials can be organic, inorganic, or a combination of organic and inorganic components. Because of the complexity and diversity of engineered nanomaterial structure and composition, the behavior and toxicity of particles released to the environment will vary greatly. A recent review discusses the potential implications of engineered nanomaterials in the environment (Scown et al., 2010). However, specific information is limited regarding the occurrence and fate of engineered nanomaterials in municipal wastewater, their response to treatment, and their public health and environmental significance.

Some research has been conducted on the fate of engineered nanoparticles in wastewater treatment. Kaegi et al. (2011) studied the fate of silver nanoparticles added to the inflow of a pilot-scale conventional wastewater treatment plant. Most of the silver nanoparticles became associated with sludge and biosolids and were not detected in the pilot plant effluent. Another study investigated the removal of titanium nanoparticles at wastewater treatment plants. Kiser et al. (2009) found that the majority of titanium in raw sewage was associated with particles >0.7 µm, which were generally well removed through a conventional process train. However, titanium associated with particles <0.7 µm (near the nanoscale) were found in the treated wastewater effluents.

Ongoing research is exploring possible health effects from engineered nanoparticles (and associate mechanisms of effect) via various exposure pathways (NRC, 2009a, 2011b). So far, the trace levels of engineered nanoparticles in wastewater have not been linked to adverse human health impacts (O’Brien and Cummins, 2010). At present, most engineered nanoparticles in municipal wastewater originate from household and personal care products, and for these, direct exposure in the household itself is likely far greater than from potential ingestion of wastewater-influenced drinking water. Because the use of engineered nanoparticles in consumer products is expected to continue to rise, continued exposure and risk assessments will be important for assessing impacts on the environment and public health.

ORGANIC CHEMICALS

Wastewater is generally rich in organic matter, which is measured as TOC, dissolved organic carbon (DOC; that portion of the TOC that passes a 0.45-mm pore-size filter), and particulate organic carbon (POC; that portion of the TOC that is retained on the filter). Of the DOC present in highly treated reclaimed water, the vast majority is generally natural organic matter and soluble microbial products, with small concentrations of a variety of individual organic chemicals (Table 3-3; Namkung and Rittman, 1986; Shon et al., 2006).

Trace organic chemicals originate from industrial and domestic products and activities (e.g., pesticides, personal care products, preservatives, surfactants, flame retardants, perfluorochemicals), are excreted by humans (e.g., pharmaceutical residues, steroidal hormones), or are chemicals formed during wastewater and drinking water treatment processes. The vast majority of these trace organic chemicals occur at microgram per liter and lower levels. This complex mixture of low concentrations of contaminants has long been recognized; Ram (1986) reported that 2,221 organic chemicals had been identified in nanogram per liter to microgram per liter concentrations in water around the world, including 765 in finished drinking water. Modern analytical tools are extremely sensitive and often capable of detecting nanogram per liter or lower concentrations of organic contaminants in water. In this report, these compounds are termed trace organic contaminants,

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3 http://www.nanotechproject.org/inventories/consumer/analy-sis_draft.

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

TABLE 3-3 Categories of Trace Organic Contaminants (Natural and Synthetic) Potentially Detectable in Reclaimed Waters

Category Examples
Industrial Chemicals 1,4-Dioxane, perflurooctanoic acid, methyl tertiary butyl ether, tetrachloroethane
Pesticides Atrazine, lindane, diuron, fipronil
Natural chemicals Hormones (17β-estradiol), phytoestrogens, geosmin, 2-methylisoborneol
Pharmaceuticals and metabolites Antibacterials (sulfamethoxazole), analgesics (acetominophen, ibuprofen), beta-blockers (atenolol), antiepileptics (phenytoin, carbamazepine), antibiotics (azithromycin), oral contraceptives (ethinyl estradiol)
Personal care products Triclosan, sunscreen ingredients, fragrances, pigments
Household chemicals and food additives Sucralose, bisphenol A (BPA), dibutyl phthalate, alkylphenol polyethoxylates, flame retardants (perfluorooctanoic acid, perfluorooctane sulfonate)
Transformation products N-Nitrosodimethylamine (NDMA), bromoform, chloroform, trihalomethanes

but they are also commonly called micropollutants or contaminants of emerging concern (CECs). EPA has defined CECs as “pollutants not currently included in routine monitoring programs” that “may be candidates for future regulation depending on their (eco)toxicity, potential health effects, public perception, and frequency of occurrence in environmental media” (EPA, 2008a). Trace organic contaminants and CECs are not always newly discovered waterborne contaminants. They also include constituents that have been present in the environment for long periods of time, but for which analytical or health data have only recently become available.

With modern analytical technology, nearly any chemical will likely be detectable at some concentration in wastewater, reclaimed water, and drinking water. The challenge is not so much one of detection, but rather determination of human and environmental health relevance. The following section provides information on representative classes of trace organic chemicals present in reclaimed water, although the committee acknowledges that there may be many other classes and substances present.

Industrial Chemicals

Many chemicals originating from industrial activities that have been detected in wastewater need to be considered when that wastewater becomes part of a domestic water supply. These include solvents, detergents, petroleum mixtures, plasticizers, flame retardants, and a host of other products or product ingredients. A few of these chemicals are not completely removed by conventional water and wastewater treatment processes. For example, an industrial chemical that has caused concern in water reuse programs in California is 1,4-dioxane, a common industrial solvent considered a probable carcinogen, which has been shown to break through reverse osmosis membranes.

In 1986, EPA estimated that as much as one-third of all priority pollutants entering U.S. waters from wastewater discharges were the result of industrial discharges into public sewers (EPA, 1986). Additionally, pulsed releases from certain industries have been known to disrupt the biological processes at wastewater treatment plants, resulting in reduced treatment efficiency (Kelly et al., 2004; Kim et al., 2009; You et al., 2009). For these reasons, under the authority of the Clean Water Act, EPA established the industrial pretreatment program, which requires wastewater treatment plants processing 5 million gallons per day (19,000 m3/d) or greater to establish pretreatment programs (see also Box 10-1). The pretreatment program also applies to smaller systems with known industrial input. This program was specifically designed to address priority pollutants, which are defined under the Clean Water Act in section 307(a). Although the pretreatment program has been largely successful at reducing the loading of contaminants into municipal wastewater treatment plants, a much smaller, but perhaps significant, input of these chemicals also enters the sewer system from household use, leaking sewage conveyance pipes, and illegal connections/dumping (mostly from the former).

Pesticides

Despite the fact that pesticides are generally used outdoors and would not be expected to be discharged directly to the sewer, some pesticides have been detected in wastewater effluents. The sources are not fully characterized, but some loading could be expected through residues in food products, head lice treatments, veterinary/pet care applications, manufacturing or handling facilities, and infiltration of landscape runoff into sewer conveyance lines. The herbicide atrazine, which

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

is used primarily on corn and soybean crops, recently has been shown to be a contaminant in nearly all U.S. drinking water, appearing in regions far removed from agricultural activities (Benotti et al., 2009). Subsequent research also has demonstrated that atrazine also occurs in most wastewater treatment effluents (Snyder et al., 2010a), yet the levels detected are generally in the nanogram-per-liter range, far lower than the EPA MCL of 3 µg/L. Considering that wastewater effluents are generally low in pesticide residues and that reclaimed water employed in potable reuse projects is regularly surveyed for all pesticides regulated in drinking water, it is unlikely that these compounds will pose a unique risk to water reuse.

Pharmaceuticals and Personal Care Products

Recently, a great deal of attention has been given to the occurrence of pharmaceuticals in wastewater effluents. Although pharmaceuticals were detected in U.S. waters as early as the 1970s (Garrison et al., 1975, Hignite and Azarnoff, 1977), much of the recent interest was evoked when Kolpin et al. (2002) in a nationwide stream sampling study documented the occurrence of 82 trace organic chemicals of wastewater origin. Commonly detected chemicals included triclosan (an antimicrobial compound), 4-nonylphenol (a metabolite of a chemical found in detergents, see Box 3-1), and synthetic estrogen from birth control, which has been implicated as a causative agent in fish feminization (Purdom et al., 1994). Laboratory studies have confirmed that ethinyl estradiol (EE2) is capable of affecting fish physiology at subnanogram-per-liter concentrations, with a predicted no-effect concentration of 0.35 ng/L (Caldwell et al., 2008). It is now quite clear that a wide range of pharmaceuticals can and will be detected in reclaimed water samples (see Table 3-3 for examples).

Personal care products (e.g., shampoo, lotions, perfumes) represent the source of another class of chemicals that have been widely detected in wastewater treatment plant effluents. It is logical that a substance used as an ingredient of a personal care product will enter the sewer system. For instance, several studies have demonstrated that certain synthetic musks used as fragrances in personal care products not only are incompletely removed by conventional wastewater treatment (Heberer, 2002) but also bioaccumulate in fish residing in effluent-dominated streams (Ramirez et al., 2009). There are many other examples of personal care products, which have been detected in treated wastewater. Many of these key ingredients may also be classified as household or industrial chemicals as well.

Household Chemicals and Food Additives

Within the typical household, many chemicals are used for cleaning, disinfecting, painting, preparation of meals, and other applications. Many of these chemicals find their way into the wastewater collection system, and some are detectable in reclaimed water as well. An interesting illustration is the artificial sweetener sucralose (1,4,6-trichlorogalactosucrose), which is widely used in the United States. This chlorinated sucrose molecule is predictably difficult to remove through biological treatment and is largely resistant to oxidation during water treatment as well. Therefore, concentrations in wastewater are generally in the microgram-per-liter range, and sucralose has been detected at similar concentrations in potable water (Buerge et al., 2009; Mawhinney et al., 2011).

Of the household chemicals of interest, those chemicals with the potential to disrupt the function of the endogenous endocrine system have been of particular interest. One particular class of surfactants, aklylphenol polyethoxylates (APEOs), has become of concern because of the estrogenic potency of some of its degradation products (see Box 3-1). Another compound of increasing interest is bisphenol A (BPA), which is used in a variety of consumer products and has been shown to be estrogenic (Durando et al., 2007). BPA has been detected in drinking water, but the concentrations are extremely low (Benotti et al., 2009), in part because of BPA’s rapid oxidation by chlorine and ozone disinfectants commonly used in water treatment (Lenz et al., 2004). In terms of human exposure, the contribution of BPA from drinking water is minute compared with exposure from food packaging and storage materials (Stanford et al., 2010). Household products and pharmaceuticals often contain inert substances at much higher concentrations than the active product. In some cases, these inert substances may also warrant further investigation as to potential impacts to water treatment systems and environmental health.

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

BOX 3-1
Alkylphenol Polyethoxylates

Alkylphenol polyethoxylates (APEOs) are a family of surfactants that were once widely used in domestic and industrial cleaning products. This family of relatively benign chemicals serves as an example of how transformation reactions in engineered and natural systems can produce compounds that pose potential risks to aquatic organisms or human health.

The most common members of this family of compounds contain either eight or nine carbon atoms in their alkyl functional group (Montgomery-Brown et al., 2003; Loyo-Rosales et al., 2009) and are referred to as octylphenol polyethoxylates (OPEO) and nonylphenol polyethoxylates (NPEO), respectively (see figure below). Most OPEOs and NPEOs in commercial products consist of a mixture of compounds with between 1 and 20 ethoxylate groups. The surfactants with more than two carbons in their ethoxylate chain exhibit relatively low toxicity to aquatic organisms in standard toxicity tests (Staples et al., 2004; Loyo-Rosales et al., 2009). However, the compounds undergo biotransformation in wastewater treatment plants that employ anaerobic treatment processes (e.g., nitrate removal by denitrification) and in aquifer recharge systems in which anoxic (anaerobic) conditions occur. Anaerobic biotransformation of OPEO and NPEO occurs through sequential cleavage of the ethoxylate carbons, ultimately leading to formation of octylphenol or nonylphenol (Ahel et al., 1994a,b). Nonylphenol typically occurs in wastewater effluent at concentrations about 10 times higher than those of octylphenol (Loyo-Rosales et al., 2009). Nonylphenol and the transformation products with only one or two carbons in the polyethoxylate chain are substantially more toxic to aquatic life than the corresponding OPEO and NPEO surfactants (Staples et al., 2004). Octylphenol, nonylphenol, and the short polyethoxylate chains have been implicated in the feminization of fish observed in effluent-dominated streams (Johnson et al., 2005), although steroid hormones (e.g., 17β-estradiol) typically account for about 10 times more estrogenic activity than octylphenol or nonylphenol.

In recognition of the risks to aquatic life associated with APEOs and their transformation products, their use was restricted in the European Union in the 1990s. In 2005, EPA set a water quality criterion for freshwater aquatic life of 6.6 μg/L for chronic exposure to nonylphenol (EPA, 2005a) that is approximately equal to or slightly higher than concentrations typically detected in wastewater effluent in the United States (Montgomery-Brown et al., 2003; Loyo-Rosales et al., 2009). As a result, many manufacturers have replaced APEOs in consumer products or have reduced their concentrations. The compounds are still used for certain industrial applications and for specialty cleaning products.

image

General structure of alkylphenol polyethoxylate surfactants. For the alkyl group, x = 7 for octylphenol and 8 for nonylphenol. For the ethoxylate group, y = 0 to 19.

Naturally Occurring Chemicals

Estrogen hormones (e.g., 17β-estradiol) are endogenous4 compounds that are excreted in relatively large concentrations by animals. In studies of wastewater effluent, the measured concentrations of endogenous estrogen hormones in most cases far exceeded those of the synthetic steroid hormones (Snyder et al., 1999; Huang and Sedlak, 2001). Huang and Sedlak (2001) reported that reverse osmosis treatment (see Chapter 4) removed more than 95 percent of estrogen hormones. Additionally, free chlorine or ozone disinfection will effectively attenuate estrogen hormone concentrations in water (Westerhoff et al., 2005).

Naturally occurring compounds that affect taste and odor represent another important class of natural chemicals that may pose challenges in water reuse. Of these, the best characterized are geosmin and 2-methylisoborneol (MIB), which are generally found in lakes and reservoirs (Medsker et al., 1968, 1969). However, geosmin is also naturally occurring in certain vegetables, such as red beets (Lu et al., 2003). Although geosmin and MIB are not considered toxic at the concentrations found in water, the olfactory displeasure can create great public resistance to water. Compounds that affect taste and odor can be present through naturally occurring compounds or through anthropogenic substances. However, these two odoriferous compounds that cause great public resistance to water can and should be considered in reuse planning for both potable and nonpotable applications in urban environments (Agus et al., 2011).

_____________

4Synthesized within an organism.

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

Transformation Products

Wastewater effluents are generally rich in organic constituents, and during most wastewater treatment processes, the majority of organic chemicals are not completely removed or mineralized. Although some treatment processes separate contaminants for subsequent disposal (i.e., sludge, reverse osmosis concentrate, spent activated carbon), both biological and oxidative processes commonly employed in water and wastewater treatment result in the formation of transformation products. When they result from disinfection processes, these products are generally referred to as disinfection byproducts; however, some oxidative processes (e.g., ozonation, ultraviolet [UV] irradiation–advanced oxidation processes [UV-AOP]) are used specifically for contaminant attenuation and not disinfection. Therefore, the term transformation product is more applicable to the range of water reclamation processes.

Through most oxidation processes, the total concentration of DOC remains relatively unchanged (Wert et al., 2007), although the attenuation of many specific trace organic chemicals is observed (Snyder et al., 2006c). This empirical observation dictates that the vast majority of chemicals attenuated during oxidative processes are not truly removed, but rather transformed into oxidation products. Most biological and oxidative transformation products have not been characterized. For instance, in drinking water it has been estimated that the majority of total organic halides (TOX) formed during disinfection with chlorine have not been identified (Krasner et al., 2006; Hua and Reckhow, 2008).

One example is triclosan, an antimicrobial compound used frequently in soap and other personal care products and thus commonly detected in wastewater (Singer et al., 2002). Triclosan is known to react with chlorine to form various disinfection byproducts, including chloroform (Rule et al., 2005; Greyshock and Vikesland, 2006). Studies have also demonstrated that when triclosan is exposed to UV irradiation, it can form dioxin-like compounds that may be toxicologically significant (European Commission, 2009) but are easily biodegraded.

It is also well known that certain compounds, which may be innocuous in their original form, can transform into toxic substances through water or wastewater treatment processes. The disinfection byproducts of chlorine first identified in the 1970s are a good example (Trussell and Umphres, 1978). N-Nitrosodimethylamine (NDMA; see Box 3-2) is a more contemporary example. NDMA can be an especially challenging contaminant for water reuse applications because chloramination, a common method of wastewater disinfection, has been linked to NDMA formation and because NDMA is not well rejected by reverse osmosis membranes (Mitch et al., 2003) and must be removed by subsequent photolysis. There is some evidence that polymers used in the management of biological wastewater treatment may serve as important NDMA precursors (Kohut and Andrews, 2003; Neisess et al., 2003). Continued research examining how NDMA is formed, how it can be removed, what its precursors are, and how they can be better managed in processes upstream of disinfection is needed.

Municipal wastewater is often elevated in nitrogen, iodine, and bromine constituents as compared with ambient waters (Venkatesan et al., 2011), which may lead to increased levels of nitrogenous, iodinated, and brominated disinfection products, respectively, when chlorination is applied (Joo and Mitch, 2007; Krasner et al., 2009), but this has not yet been documented. Iodinated and brominated disinfection products are among the most genotoxic of those disinfection byproducts currently identified in water (Plewa et al., 2004; Richardson et al., 2008). Recently, medium-pressure UV-AOP has been shown to form genotoxic organic transformation products when applied to waters containing nitrate, although subsequent treatment with granulated activated carbon was able to remove the formed genotoxic products to levels below detection (Heringa et al., 2011).

As water conservation efforts grow in many urban regions, concentrations of salt and organics will likely increase in wastewater. Thus, a better understanding of disinfection byproduct precursors, ways to minimize the disinfection byproduct formation, and ways to remove them is important for enhancing the safety of water reuse scenarios, including de facto reuse. Transformation products in reclaimed water will also be widely variable in concentration and structure because of the highly complex mixtures and different source water characteristics. Water reuse projects would therefore benefit from improved methods for understanding the toxicity of complex mixtures (see Chapter 11).

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×

BOX 3-2
N-Nitrosodimethylamine

N-Nitrosodimethylamine (NDMA) has been considered a carcinogen for some time (Magee et al., 1976), and EPA has calculated the one in one million cancer risk from drinking water to occur at approximately 0.7 ng/L. Along with other members of the nitrosamine family, NDMA received attention in the 1970s in connection with processed foods and beverages, but it was not found in drinking water or domestic wastewater until the turn of the century when analytical methods improved to the point where NDMA could be identified at submicrogram-per-liter levels (Taguchi et al., 1994). Subsequently, NDMA was found in groundwater downgradient of rocket engine testing facilities, in water leaving ion exchange facilities, and in wells influenced by reuse projects (Najm and Trussell, 2001). Recently, as part of EPA’s unregulated contaminant monitoring rule (UCMR2), NDMA was detected in 25 percent of the drinking water distribution systems sampled, at levels between 2 and 600 ng/L. For the most part, these drinking water systems reported that their source water was influenced by wastewater and used chloramines for disinfection (Blute et al., 2010).

NDMA often appears both in raw and treated wastewaters in the United States and Europe (Mitch et al., 2005, Krauss et al., 2009). A 2005 survey of 10 wastewater plants found NDMA in the influent up to 140 ng/L; two plants were 20 ng/L or below, but most were between 20 and 70 ng/L. Effluent samples, however, ranged as high as 960 ng/L (Valentine et al., 2005). Others have reported levels as high as 1,820 ng/L (Gan et al., 2006).

Control of NDMA in treated reclaimed water involves three components: (1) control of the sources of NDMA and its precursors in treatment plant influents, (2) management of the conventional wastewater treatment process, and (3) application of advanced treatment to remove what remains. Both Orange County and Los Angeles have had some success in identifying sources of NDMA and its precursors and have improved the quality of the influent (Valentine et al., 2005). However, it is unclear how much of the NDMA may be the result of domestic sources (e.g., pharmaceuticals, personal care products) that are more difficult to control (Sedlak et al., 2005; Krauss et al., 2009; Shen and Andrews, 2011). Wastewater disinfection practice, particularly chloramination (Pehlivanogllu-Mantas et al., 2006) appears to be an important target. Research by wastewater authorities has demonstrated several factors important to NDMA formation during wastewater chlorination and a number of strategies that may be employed to reduce it (Neisess et al., 2003; Huitric et al., 2005, 2007; Tang et al., 2006; Farée et al., 2011). Although these strategies show promise, NDMA remains an issue in wastewaters disinfected with chloramines, where levels above 100 ng/L are common (Najm and Trussell, 2001; Valentine et al., 2005; Huitric et al., 2007). As a result, facilities designed to produce reclaimed water for direct injection into groundwater include treatment processes designed to remove it (e.g., UV-AOP).

CONCLUSIONS

The very nature of wastewater suggests that nearly any substance used or excreted by humans has the potential to be present at some concentration in the treated product. Modern analytical technology allows detection of chemical and biological contaminants at levels that may be far below human and environmental health relevance. Therefore, if wastewater becomes part of a reuse scheme (including de facto reuse), the impacts of wastewater constituents on intended applications should be considered in the design of the treatment systems. Some constituents, such as salinity, sodium, and boron, have the potential to affect agricultural and landscape irrigation practices if they are present at concentrations or ratios that exceed specific thresholds. Some constituents, such as microbial pathogens and trace organic chemicals, have the potential to affect human health, depending on their concentration and the routes and duration of exposure (see Chapter 6). Additionally, not only are the constituents themselves important to consider but also the substances into which they may transformed during treatment. Pathogenic microorganisms are a particular focus of water reuse treatment processes because of their acute human health effects, and viruses necessitate special attention based on their low infectious dose, small size, and resistance to disinfection. Chapter 4 discusses the treatment processes often used to attenuate concentrations of chemical and biological contaminants of suspected health risk to humans.

Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
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Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 56
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 57
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 58
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 59
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 60
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 61
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 62
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 63
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 64
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
Page 65
Suggested Citation:"3 Water Quality." National Research Council. 2012. Water Reuse: Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. Washington, DC: The National Academies Press. doi: 10.17226/13303.
×
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Expanding water reuse--the use of treated wastewater for beneficial purposes including irrigation, industrial uses, and drinking water augmentation--could significantly increase the nation's total available water resources. Water Reuse presents a portfolio of treatment options available to mitigate water quality issues in reclaimed water along with new analysis suggesting that the risk of exposure to certain microbial and chemical contaminants from drinking reclaimed water does not appear to be any higher than the risk experienced in at least some current drinking water treatment systems, and may be orders of magnitude lower. This report recommends adjustments to the federal regulatory framework that could enhance public health protection for both planned and unplanned (or de facto) reuse and increase public confidence in water reuse.

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