Urban Water Reuse Handbook

6 Pharmaceuticals and Personal Care Products in Wastewater: Implications for Urban Water Reuse 6.1 Introduction................................................................................................................................55 6.2 Snapshot of PPCPs in Wastewater...........................................................................................56 6.3 Removal of PPCPs in WWTPs and Water Reclamation Plants..........................................58

Amanda Van Epps Berlin, Germany

Lee Blaney University of Maryland Baltimore County

6.4

Adsorption of PPCPs to Solids in Primary Treatment • Removal of PPCPs in Biological Processes • Transformation during Disinfection Processes • Removal in Advanced Treatment Processes • Removal during Infiltration and Riverbank Filtration

Concerns about PPCP Presence in Reclaimed Water........................................................... 71 Ecological and Human Health Concerns • Application-Specific Concerns

6.5 Summary and Conclusions.......................................................................................................73 References................................................................................................................................................73

Preface The presence of pharmaceuticals and personal care products (PPCPs) in water and wastewater sources has been well documented over the last 15 years. These compounds represent an ecological and public health concern in the context of water reuse, due to the potential accumulation of PPCPs in municipal water sources. Furthermore, planned indirect water reuse may introduce PPCPs to water supplies that were previously uncontaminated by xenobiotics. In this chapter, a short introduction to the importance of PPCPs in the context of water reuse is provided, and the classes of PPCP compounds that comprise the most significant concerns are discussed. The bulk of this chapter focuses on the state-of-the-knowledge regarding PPCP removal in conventional and advanced wastewater treatment and water reclamation processes. Finally, the ecological and public health concerns associated with these compounds are highlighted to demonstrate the importance of achieving higher removal efficiencies of PPCPs within treatment plants.

6.1 Introduction Over the past 30 years, the presence of pharmaceuticals and personal care products (PPCPs) has been documented in wastewater supplies and the environment [74,85,135,171,190]. Unlike many traditional contaminants for which the toxicological activity is separate from the intended use, pharmaceuticals have been specially designed to elicit a biochemical response in organisms. For this reason, pharmaceuticals represent a unique threat to

ecological and public health, even at trace concentrations. Given this threat, increased understanding of the removal of PPCPs in wastewater treatment processes is required to ensure ecological well-being and sustained protection of public water supplies. Unplanned potable water reuse has long been a reality in many locations, as wastewater effluent from upstream cities comprises some fraction of the drinking water supply for downstream cities. However, as per capita freshwater supplies continue to decrease due to increasing global population and 55

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climate change, planned water reuse is becoming a deliberate strategy to cope with pressures on water supplies in many parts of the world. Windhoek, Namibia has been practicing direct potable water reuse since the 1980s [194]. Many other municipalities already use wastewater effluent as a source of irrigation water for highway medians and golf courses or makeup water in cooling towers, but more are now actively pursuing indirect potable water reuse by injecting wastewater effluent into groundwater aquifers or pumping wastewater effluent into upstream reservoirs [106]. These utilities include Los Angeles (CA), San Diego (CA), Franklin (TN), Mexico City (Mexico), Gwinnett County (GA), Fairfax County (VA), Scottsdale (AZ), Miami-Dade (FL), Sulaibiya (Kuwait), Willunga (Australia), El Paso (TX), and Adelaide (Australia), among others [46]. The U.S. Environmental Protection Agency (EPA) has developed a comprehensive document entitled Guidelines for Water Reuse, which provides an overview of issues, examples, and treatment guidelines for water reuse operations [46]. The presence of trace concentrations of PPCPs in reclaimed water prompts not only ecological concerns for receiving waters, but also potential public health consequences in direct and indirect potable water reuse scenarios. Some of these concerns include reproductive abnormalities [77,114], antibiotic resistance [117,136], and developmental impacts [49,51]. Water reuse scenarios involve engineering and science facets, many of which have been described in detail in earlier chapters of this book. In this chapter, the fate of PPCPs is explored in wastewater treatment, and a context for the ecological and public health concerns is provided. The objective of this chapter is to provide a snapshot of the removal mechanisms for PPCPs in wastewater treatment processes to build greater understanding of this emerging area of interest. As there are over 7700 pharmaceuticals approved for human use in the world [63], PPCPs demonstrate a wide range of physicochemical properties and biodegradability. For that reason, this chapter provides an insight into the behavior of select PPCPs through conventional and advanced wastewater treatment processes. With mounting public pressure and ecological evidence, regulations for select PPCPs in wastewater effluent are expected in the future. Ultimately, this chapter aims to provide a context for considering treatment of such waters.

6.2 Snapshot of PPCPs in Wastewater Hundreds of PPCPs have been detected in raw wastewater at concentrations ranging from nanograms per liter (ng/L) to hundreds of micrograms per liter (μg/L) [109,110,184]. Wastewater effluent may contain PPCP concentrations as high as tens of µg/L [110,170]; furthermore, these measurements likely underestimate the presence of PPCPs in wastewater due to limited access to advanced analytical instruments/methods and high limits of quantitation. PPCPs are present in wastewater largely because of human consumption. Some fraction of the pharmaceutical mass consumed by humans is excreted unchanged; furthermore, improper disposal of pharmaceuticals down the drain


Urban Water Reuse Handbook

also contributes to detectable concentrations in raw wastewater. Personal care product ingredients typically enter wastewater supplies through rinse water from laundry, hand washing, or showering [173]. Chemicals in both categories can also originate from manufacturing effluent, stormwater runoff, or landfill leachate [88,116,173]. The presence of PPCPs in reclaimed water is influenced by trends in local water use and PPCP consumption. For example, Clara et al. [27] analyzed raw wastewater and wastewater effluent in Austria for diazepam, but the compound was not detected. The authors attributed the absence of diazepam in wastewater to the relatively low consumption of that pharmaceutical in Austria. Similarly, iopromide, an x-ray contrast agent, was not detected in raw wastewater, presumably due to the lack of hospitals connected to the corresponding wastewater collection system. Note that these compounds have both been detected in other studies [79,169,203]; therefore, select PPCPs may be relevant to some systems, but not others. A fundamental challenge associated with measuring PPCPs in wastewater, and designing treatment schemes to remove or degrade these emerging contaminants, is the breadth of compounds that fall into these categories. No central strategy for prioritization of PPCPs has been adopted; however, the corresponding approach should include a number of factors such as mass consumption rates, ecological or human health risk factors, physicochemical properties, biodegradability, pharmacological class, and a sustainability index [21,170]. The following classes of compounds have been found to be among the most frequently detected in environmental matrices, including wastewater and surface waters [110,116,160]: antibiotics, antiinflammatory/analgesic drugs, lipid regulators and beta blockers, hormones, antiepileptics, various personal care product ingredients, and endocrine-disrupting chemicals (EDCs). Given the frequency of detection in environmental media, these compounds are expected to play a significant role in the urban water cycle. Properties of representative compounds for each category are provided in Table 6.1. Antibiotics are prescribed to treat bacterial infections in humans and animals. In addition, antibiotics are extensively used as growth promoters in concentrated animal feeding operations, indicating that these compounds are important components of both urban and rural water cycles. More than 400 such compounds are registered for medical use, and 100,000– 200,000 metric tons of antibiotics are manufactured every year [88,195]. Urban wastewater contains high antibiotic loads because a large fraction of the consumed mass (e.g., up to 98% in the case of amikacin [18]) is excreted unchanged [88]. More than 50 different antibiotics have been detected in raw wastewater, and typical concentrations are tens of ng/L to tens of μg/L [88,100,109,110,184]; the corresponding concentrations in wastewater effluent are as high as μg/L [67,88,100,109,110]. The antibiotic potency of metabolites has not been widely considered from an environmental context; however, these species may also be environmentally relevant because many antibiotics are metabolized into their active form.

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Pharmaceuticals and Personal Care Products in Wastewater TABLE 6.1 Summary of Chemical Properties of a Representative Compound from Each Prominent PPCP Category Category Antibiotics

Compound Ciprofloxacin

Chemical Formula

Molecular Weight (Da)

Chemical Structure

C17H18FN3O3

O F

KH (atm m3/mol)a

a Log kow

pkaa

331.35

5.09 × 10−19

0.28

6.09 8.82

236.28

1.08 × 10−10

2.45

–

206.29

1.50 × 10−7

3.97

4.91

257.34

7.98 × 10−13

3.48

9.42

272.39

3.64 × 10−11

4.01

–

250.34

1.19 × 10−8

4.77

4.50

258.41

1.32 × 10−4

5.90

–

OH

N

N

HN

Antiepileptic agents

Carbamazepine

C15H12N2O N O

Anti-inflammatory drugs/analgesics

Ibuprofen

NH2

C13H18O2

O OH


Beta blockers

Propranolol

C16H19NO2

OH O

Hormones

17β-Estradiol

NH

C18H24O2

OH H H

H

HO

Lipid regulators

Gemfibrozil

C15H22O3

O

O OH

Musk fragrances

Galaxolide

C18H26O O

a

Reference 155.

Anti-inflammatory drugs and analgesics are widely used to treat inflammation and pain. These pharmaceuticals are available as prescription drugs and over-the-counter remedies, such as ibuprofen. At least 20 analgesic drugs have been detected in raw wastewater with typical concentrations ranging from tens of ng/L to hundreds of μg/L; the concentrations in wastewater effluent are approximately one order of magnitude lower [110,184]. Lipid regulators and beta-blockers are prescribed to treat cardiovascular disease. At least six lipid regulators and seven betablockers have been detected in raw wastewater at concentrations of hundreds of ng/L to μg/L [110,184]. Interestingly, more compounds within these classes have been detected in wastewater effluent. In particular, at least 9 lipid regulators and 12 betablockers have been detected in wastewater treatment plant (WWTP) effluent at concentrations similar to those detected in raw wastewater [110,184].


The most commonly studied antiepileptic drug is carbamazepine. In one review, carbamazepine was detected in 100% of the investigated raw wastewater samples and 98% of wastewater effluent samples [110]. Concentrations of carbamazepine in raw wastewater typically range from tens of ng/L to μg/L [110,184]; effluent concentrations remain in the range of tens of ng/L to μg/L [110,116,184]. As indicated in the following, this compound may be a good indicator of PPCP presence in wastewater due to the high frequency of detection and low removal during biological treatment processes. Personal care product ingredients include a wide range of compounds including musk fragrances, ultraviolet (UV) filters, surfactants, preservatives, and plasticizers. In the Miège et al. [110] review, galaxolide, a musk fragrance, was detected at μg/L concentrations in every raw wastewater sample for which it was analyzed. Galaxolide was also detected in 100% of wastewater effluent samples at concentrations of hundreds of ng/L to μg/L


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[110]; therefore, this compound may also serve as a robust indicator compound for personal care products in wastewater. Hormones detected in wastewater can include human hormones that are naturally excreted and natural or synthetic hormones prescribed for medical purposes. To date, at least five different hormones have been detected in raw wastewater at concentrations of ng/L to hundreds of ng/L [100,110,184]. These compounds are potent at concentrations as low as 1–10 ng/L, as demonstrated by Kidd et al. [77]; therefore, measured wastewater effluent concentrations of hundreds of picograms per liter (pg/L) to tens of ng/L are environmentally relevant. Endocrine-disrupting chemicals are often included in studies of PPCPs but are not limited to a particular treatment class or category. Chemicals as broadly distributed as birth control compounds (e.g., ethinyl-estradiol), reproductive hormones (e.g., estrone), replacement hormones (e.g., equilenin), plant steroids (e.g., stigmastanol), alkylphenols (e.g., nonylphenol), and plasticizers (e.g., bisphenol A) exhibit estrogenic activity. Thus, potential endocrine disruption effects in urban water reuse must be considered for a broad range of PPCPs that may demonstrate temporal and geographical consumption patterns. Several review articles have provided exhaustive data on detections of PPCPs in raw and treated wastewater [88,100,109,110,184]. The breadth of compounds detected in urban wastewater, and the associated variability in physicochemical properties, is captured in Table 6.1. For the PPCP classes of interest, a significant fraction of the influent mass load is discharged in wastewater effluent, a phenomenon that is not particularly surprising given that awareness of these compounds and their potentially deleterious effects has only recently developed. Furthermore, existing WWTPs were not designed to consider removal of these emerging contaminants. In Section 6.3, the knowledge base that has developed over the last decade is considered to better understand removal of PPCPs in conventional and advanced wastewater treatment processes.

6.3 Removal of PPCPs in WWTPs and Water Reclamation Plants As discussed in Section 6.2, a large fraction of consumed PPCPs enter the wastewater system through excretion, rinsing, or improper disposal; furthermore, conventional WWTPs are not designed, or optimized, for removal of these emerging contaminants. For this reason, WWTPs comprise the largest point sources for PPCP introduction to the environment and represent an important consideration in the urban water cycle. To address the occurrence of PPCPs in the urban water cycle, baseline removal of PPCPs in conventional wastewater treatment processes must be understood to optimize operation and improve removal efficiencies for emerging contaminants. This information will also prove useful in the design of WWTPs and water reclamation plants, especially as future regulations associated with particular PPCPs are expected.



6.3.1 Adsorption of PPCPs to Solids in Primary Treatment For most municipal WWTPs, the initial treatment process involves settling of large particles present in raw wastewater in primary clarifiers. In this stage, PPCP removal is not expected to be high, especially as PPCPs discharged into the wastewater system will have already been in contact with these solids in the wastewater collection system. Regardless, low fractional removals can be expected as PPCPs may sorb to primary solids. Prediction of PPCP sorption to primary solids based on physicochemical properties is challenging because two underlying mechanisms are involved with this process [158,164,170,172]: • Partitioning of PPCPs into primary solids through interactions between hydrophobic moieties of PPCP molecules with lipid and lipophilic fractions of sludge particles • Sorption of PPCP molecules due to electrostatic interactions between cationic PPCP species (usually due to protonated amine functionalities) and negatively charged particles Therefore, while the octanol–water partition coefficient (Kow) might be expected to describe hydrophobic interactions, the corresponding acid dissociation constants (Ka) are needed to predict electrostatic interactions. One approach is to consider both sorption processes using the pH-dependent octanol–water partition coefficient Dow. Note that Dow is equal to Kow for PPCPs without an acidic or basic moiety. For compounds that demonstrate acid/ base speciation, Dow is defined as shown in Reference 145:

Dow =

K ow 1 + 10 pH − pK a

(6.1)

In spite of its relevance to these scenarios, Dow has not been reported for a wide range of PPCPs to date. More commonly, experimentally derived sorption coefficients (KD) are used to describe sorption of each PPCP to primary sludge. This approach remains challenging because the empirical value of KD is dependent on the conditions for which it was determined, including water quality, the characteristics of sludge, pH, and the initial PPCP concentration; therefore, this parameter may not be universally applicable. Nevertheless, considerable efforts have focused on experimental determination of sorption coefficients for PPCPs, as summarized in Table 6.2. Dargnat et al. [34] demonstrated the relevance of hydrophobicity by monitoring the fate of five phthalates through a wastewater treatment train in France. The overall removal of phthalates ranged from 78% to 99% for the entire WWTP, but the majority of that removal occurred in the primary clarifier for four of the five compounds. Only 5% of the influent dimethyl phthalate was removed in the primary clarifier; note that the Kow value of dimethyl phthalate is at least an order of magnitude lower than that of the other studied compounds. On the other hand, Golet

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Pharmaceuticals and Personal Care Products in Wastewater TABLE 6.2 Summary of Experimentally Determined Sorption Coefficients for PPCPs onto Primary and Secondary Sludge KD (L/kg)


Compound

Category

a Log kow

Primary Sludge

17α-Ethinylestradiol

Hormone

3.67

17β-Estradiol

Hormone

4.01

4-Methylbenzylidene camphor Acetaminophen Atenolol Azithromycin Benzophenone-1 Benzophenone-2 Benzophenone-3 Benzophenone-4 Bisphenol-A Carbamazepine

UV filter

–

Analgesic β-blockers Antibiotic UV filter UV filter UV filter UV filter Plasticizer Antiepileptic

0.46 0.16 4.02 2.96 2.78 3.79 0.37 3.32 2.45

6.7 95 – – – – – – 314

Celestolide Chlorophene Ciprofloxacin

Fragrance Preservative Antibiotic

– 3.60 0.28

5300 – 2512

Clarithromycin Clofibric acid

3.16 2.57

– –

Cyclophosphamide Diazepam Diclofenac

Antibiotic Metabolite of lipid regulator Chemotherapeutic agent Anxiolytic Anti-inflammatory agent

0.63 2.82 4.51

Erythromycin Estrone Galaxolide

Antibiotic Hormone Fragrance

3.06 3.13 5.90

Gemfibrozil Glibenclamide Hydrochlorothiazide Ibuprofen

Lipid regulator Antidiabetic Diuretic Anti-inflammatory agent

4.77 4.79 −0.07 3.97

55 44 194 459 309 – 4920 5050 20,600 23 282 25.8 9.5

Ifosfamide Iopromide Ketoprofen Loratadine Mefenamic acid Norfloxacin Octocrylene Octyl-methoxy-cinnamate Oxytetracycline Phantolide Propranolol

Chemotherapeutic agent Contrast medium Anti-inflammatory agent Antihistamine Anti-inflammatory agent Antibiotic UV filter UV filter Antibiotic Fragrance β-blockers

0.86 −2.05 – 5.20 5.12 −1.03 6.88 5.80 −0.90 – 3.48

22 5 226 2336 294 2512 14,000 1000 – 6500 641

Reference

– 10,400

[22]

1220

[90] [132] [132]

[132]

[90] [56]

4.8 [172] [172] [132] [172] [132] [172] [90] [22] [132] [132] [132] [132]

[172] [172] [132] [132] [132] [56] [90] [90] [90] [132]

Secondary Sludge 316 584 631 35,000 5700 1160 64 376 260 1300 1300 8 1000 1.2 135 8800 2000 417 19,953 262 [172] 2.4 21 16 118 74 402 1810 9600 14,300 19.3 239 20.2 0.0 7.1 251 356 1.4 11 16 3321 434 15,848 – 11,000 3020 7500 366

Reference [28] [7] [28] [22] [90] [132] [132] [55] [193] [193] [193] [193] [28] [172] [132] [90] [193] [158] [55]

[172] [172] [172] [132] [132] [7] [172] [90] [22] [132] [132] [132] [132] [172] [158] [22] [172] [172] [132] [132] [132] [56] [90] [158] [90] [132] (Continued)


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TABLE 6.2 (Continued) Summary of Experimentally Determined Sorption Coefficients for PPCPs onto Primary and Secondary Sludge KD (L/kg) Compound

Log k

Sulfamethoxazole

Antibiotic

0.54

Tetracycline Tonalide

Antibiotic Fragrance

−1.30 5.70

Traseolide Triclocarban Triclosan Trimethoprim

Fragrance Antimicrobial Antimicrobial Antibiotic

a


Category

a ow

Primary Sludge 3.2

− 4.90 4.76 0.91

Reference [132]

8400 5000 5240 5300 5600

[78] [90] [22] [172] [90]

− − 427

[132]

Secondary Sludge 77 256 – 2400 11,500 18,000 17,000 40,000 17,000 208 253

Reference [132] [55] [172] [90] [22] [90] [193] [193] [55] [132]

Reference 155.

et al. [56] demonstrated the importance of both hydrophobic and electrostatic interactions in an evaluation of the removal of two fluoroquinolone antibiotics in a WWTP with tertiary treatment in Switzerland. Both compounds (i.e., ciprofloxacin and norfloxacin) have negative log Kow values, indicating the relatively hydrophilic nature of these antibiotics; additionally, these compounds are zwitterionic at near-neutral pH due to the presence of a protonated amine and a deprotonated carboxylate. For these reasons, the sorption of fluoroquinolone antibiotics onto primary sludge is expected to occur via electrostatic interactions and will, therefore, vary with wastewater pH. Consistent with these expectations, Golet et al. [56] found sorption coefficients at pH 7.5–8.4 to be approximately 2500 L/kg, which are larger than expected given the hydrophilicity of these molecules. Table 6.2 contains a summary of experimentally determined sorption coefficients for various PPCPs. Generally, sorption is negligible if KD is lower than 100 L/kg; on the other hand, substances with KD values greater than 10,000 L/kg demonstrate significant removal in primary, as well as secondary, treatment [28]. As shown in Table 6.2, only a small fraction of PPCPs is expected to demonstrate substantial removal via sorption to primary sludge; these PPCPs include hydrophobic compounds such as 17β-estradiol (estrogenic hormone) and galaxolide (musk fragrance), as well as zwitterionic species like tetracycline and norfloxacin.

6.3.2 Removal of PPCPs in Biological Processes The heart of wastewater treatment trains is the biological process, which effectively converts organic matter to carbon dioxide and biomass. Removal of PPCPs has been investigated in a variety of biological reactor configurations and operating conditions. Much like sorption of PPCPs to primary solids, prediction of biodegradation rates by chemical class or structure is challenging [72,120,170]. For this reason, biodegradation rate constants must be individually determined for each compound. Pseudo-first-order reaction kinetics have been used to


describe degradation of micropollutants in biological processes. As shown in Equation 6.2, the biodegradation rate is directly proportional to both the aqueous PPCP concentration and the mixed liquor suspended solids (MLSS), but the MLSS concentration is assumed constant over the course of the experiment [73]:

dC = −kbiol SXss dt

(6.2)

In Equation 6.2, C is the total PPCP concentration (µg/L), k biol is the biodegradation rate constant (L/gss-d), S is the soluble PPCP concentration (µg/L), and Xss is the MLSSs concentration (gss/L). A selection of published biodegradation rate constants is shown in Table 6.3. Ternes et al. [170] and Joss et al. [73] asserted that PPCPs could be classified with respect to biodegradation potential by the magnitude of the corresponding rate constant. Compounds with rate constants less than 0.1 L/gss-d are not significantly degraded in conventional biological processes, while compounds with rate constants greater than 10 L/gss-d generally demonstrate more than 95% removal during wastewater treatment. Using this classification, Joss et al. [73] concluded that only four compounds (i.e., ibuprofen, paracetamol, 17β-estradiol, and estrone) from a study of 35 PPCPs would demonstrate more than 90% removal, while negligible removal was expected for 17 others. These results are generally consistent with the conclusions of Oulton et al. [120], who reviewed published data for removal of 140 PPCPs at pilot- and full-scale wastewater treatment facilities and found that a combination of primary treatment and conventional activated sludge (CAS) tended to result in no more than 1-log (or 90%) removal of PPCPs, regardless of influent concentrations. 6.3.2.1 Effect of Reactor Configuration on PPCP Removal For compounds that demonstrate biodegradation rate constants in the 0.1–10 L/gss-d range, the biological reactor configuration has important consequences for removal efficiencies [73,170].

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Pharmaceuticals and Personal Care Products in Wastewater TABLE 6.3 Summary of Experimentally Determined Rate Constants Describing Suspended Growth Biodegradation of PPCPs Biodegradation Rate Constant


Compound

Category

L/gss-d

Reference

(Anhydro-)erythromycin 5-Amino-2,4,6-triiodo-2,3dihydroxypropyl-amidphthalic acid Azithromycin Bezafibrate

Antibiotic Contrast agent