Chapter 16. Water Reuse for Drinking Water Augmentation

16.2



CHAPTER sixteen



INTRODUCTION TO POTABLE REUSE

With increasing demands on existing water supplies and limited access to new conventional

water resources, some municipalities have begun to intentionally reuse treated municipal

wastewater effluents to augment drinking water supplies. The practice of the purposeful addition of highly treated wastewater (i.e., reclaimed or recycled water) via an environmental buffer that is subsequently used to augment a drinking water supply is referred to as planned or

intentional indirect potable reuse (IPR). Indirect potable reuse can occur through recharge of

unconfined or confined aquifers, via surface spreading or direct injection, or by surface water

augmentation into a stream or reservoir that serves as a source for drinking. In 2010, approximately 1,350 ML/d (355 mgd) of reclaimed water was used for IPR in the United States, which

represents less than 1 percent of all municipal wastewater effluents generated in the country

(Table 16-1). However, for municipalities practicing IPR, the contribution of reclaimed water

to their drinking water supply can be as high as 30 percent, with some consumers receiving

drinking water that originates by more than 50 percent from reclaimed water.

The immediate addition of reclaimed water to a drinking water distribution system

is referred to as direct potable reuse (DPR). Since 1968, DPR has seen only one significant application worldwide with the commissioning of the direct potable reuse plant in

Windhoek, Namibia (21 ML/d). In this case, advanced treated wastewater is fed directly

into the distribution system providing up to 35 percent of the city’s drinking water supply

(du Pisani, 2006). Such direct use of reclaimed water for human consumption is currently

not approved for any water system in the United States without the added protection

provided by storage in an environment buffer (National Research Council, 1998). While

planned IPR receives increasing interest among municipalities worldwide, questions

remain regarding how much treatment and monitoring is needed to protect public health

when reclaimed water is used for potable purposes. Water quality issues in IPR are associated with pathogens, organic chemicals, residual nutrients, and dissolved solids.

While the traditional maxim for selecting drinking water supplies has been to use the

highest-quality source available (Pontius, 2003), in some regions once pristine surface water

sources have evolved over time into unintentional indirect potable reuse systems, as wastewater

from upstream dischargers has increased to substantial portions of the stream flow (Swayne et

al., 1980; WEF/AWWA, 2008). Although planned and incidental or unplanned IPR systems

may share similar water quality issues, this chapter provides guidance for systems that are intentionally designed and operated to augment drinking water supplies with reclaimed water.

Usually, a planned IPR scheme consists of the following six key components:

1. A sewage collection system, which incorporates discharge permits for industries, their

monitoring and enforcement as required by USEPA regulations, and additional pollution prevention policies administered by the wastewater agency

2. A conventional wastewater treatment train, designed to minimize the presence of organic

matter and pathogens, achieving a water quality that is suitable to be discharged to the

environment meeting regulatory requirements as defined by the Clean Water Act (CWA)

3. Advanced water treatment processes which provide additional barriers to constituents of

concern, such as residual organic chemicals, nutrients, dissolved solids, and pathogens

4. An environmental buffer or natural system integrated either via surface water or groundwater storage, to provide an opportunity to physically and chemically cut the connection

to the source as well as offering time to respond to unforeseen process upsets

5. A drinking water treatment plant treating the augmented source water prior to delivery

to consumers

6. An overarching monitoring program, that assures proper performance of conventional

and advanced water treatment unit processes supplying a drinking water quality that is

suitable for human consumption at all times



Table 16-1  Evolution of Indirect Potable Reuse Schemes and Employed Treatment Technologies



Project location



Type of indirect

reuse



16.3



Montebello Forebay, Groundwater

recharge via

County Sanitation

soil-aquifer

Districts of Los

Angeles County, CA treatment

Surface water

Upper Occoquan

augmentation

Service Authority,

VA

Water Factory 21,

Groundwater

Orange County, CA recharge via

seawater barrier

Groundwater

Hueco Bolson

recharge via

Recharge Project,

direct injection

El Paso Water

Utilities, Tx

Clayton County

Surface water

Water Authority, GA augmentation

West Basin Water

Groundwater

Recycling Plant, CA recharge via

direct injection

Gwinnett County, GA Surface water

augmentation

Scottsdale Water

Groundwater

Campus, AZ

recharge via

direct injection

Toreele Reuse Plant, Groundwater

Wulpen, BEL

recharge via

infiltration ponds

NEWater, Bedok,

Surface water

Singapore

augmentation

NEWater, Seletar,

Surface water

Singapore

augmentation



First

Project

size ML/d instalation

year

(mgd)



Treatment technologies

Current

status



Suspended solids



Organic

compounds



Soil-aquifer

treatment



Residual

salts



165

(44)



1962



Ongoing



Media filtration



204

(54)



1978



Ongoing



60

(16)



1976



Terminated

2004



GAC filtration

Ion exchange

None

Lime

(optional)

clarification;

media filtration

Lime clarification Reverse osmosis; Air stripping;

Reverse

UV/AOP

reverse osmosis osmosis



38

(10)



1985



Ongoing



Lime

clarification;

media filtration



66

(17.5)



1985



Ongoing



20

(5.3)



1995



Ongoing



Land application Land application Land application None

system;

system

system;

wetlands

wetlands

Microfiltration

Reverse osmosis; Reverse osmosis Reverse

UV/AOP

osmosis



1999



Ongoing



Ultrafiltration



1999



Ongoing



Media filtration

Microfiltration



6.9

(1.8)



2002



Ongoing



32

(8.5)

24

(6.4)



2003

2003



227

(60)

53

(14)



Soil-aquifer

treatment



Residual

nutrients



None



Ozonation; GAC PAC augmented None

filtration

activated sludge

system



Pathogens

Chlorination

Soil-aquifer

treatment

Chlorination

Chlorination

Ozonation

Chlorination

Chlorination UV



Preozonation;

Chem. P-removal None

GAC filtration

Reverse osmosis Reverse osmosis Reverse

osmosis



Microfiltration

Chloramination

UV

Ultrafiltration

Ozone

Microfiltration

Chlorination



Ultrafiltration



Reverse osmosis Reverse osmosis Reverse

osmosis



Ultrafiltration

UV



Ongoing



Ultrafiltration



Ongoing



Ultrafiltration



Reverse osmosis Reverse osmosis Reverse

osmosis

Reverse osmosis Reverse osmosis Reverse

osmosis



Ultrafiltration

UV

Ultrafiltration

UV



Table 16-1  Evolution of Indirect Potable Reuse Schemes and Employed Treatment Technologies (Continued)



Project location



Type of indirect

reuse



16.4



Water Replenishment Groundwater

District of Southern recharge via direct

injection

California, CA

Inland Empire Utility Groundwater

Agency, Chico, CA recharge via soilaquifer treatment

NeWater, Ulu

Surface water

Pandan, Singapore

augmentation

Groundwater

Groundwater

recharge via direct

Replenishment

injection and

System, Orange

spreading basins

County, CA

Surface water

Western Corridor

augmentation into

Project, Southeast

drinking water

Queensland, Au

reservoir

Surface water

Loudoun County

augmentation

Sanitation

Authority, VA

Arapahoe County/

Groundwater

Cottonwood, CO

recharge via

spreading operation

Cloudcroft, NM

Spring water

augmentation

Prairie Waters

Groundwater

Project, Aurora, CO recharge via

riverbank filtration



Project

size ML/d

(mgd)

18.9

(5)



First

instalation

year



Treatment technologies

Current

status



Suspended

solids



Organic

compounds

Reverse Osmosis

  UV



Residual

nutrients



Residual

salts



Pathogens



2005



Ongoing



Microfiltration



Reverse osmosis Reverse

osmosis



Microfiltration

  UV



69

(18)



2007



Ongoing



Media filtration Soil-aquifer

treatment



Soil-aquifer

treatment



Chlorination



120

(32)

265

(70)



2007



Ongoing



Ultrafiltration



2008



Ongoing



Ultrafiltration



232

(62)



2008



Ongoing



Ultrafiltration



42

(11)



2008



Ongoing



Microfiltration

Chlorination



34

(9)



2009



Ongoing



GAC

None

None

Membrane

bioreactor

(MF)

Media filtration Reverse osmosis; Reverse osmosis Reverse

UV/AOP

osmosis



0.38

(0.1)

190

(50)



2009



Ongoing



Chlorination



2010



Ongoing



Microfiltration; Reverse osmosis; Reverse osmosis Reverse

ultrafiltration

UV-AOP

osmosis

Precipitive

Riverbank

Riverbank

Riverbank

softening

filtration;

Filtration

filtration

Artificial

UV/AOP

recharge and

BAC

recovery

GAC



None



Reverse osmosis



Reverse osmosis Reverse

osmosis

Reverse osmosis; Reverse osmosis Reverse

UV/AOP

osmosis



Ultrafiltration

  UV

Ultrafiltration

  UV



Reverse osmosis; Reverse osmosis Reverse

UV/AOP

osmosis



Ultrafiltration

  UV

Chlorination



Chlorination



Riverbank

filtration

UV

  Chlorination







Water Reuse for Drinking Water Augmentation



16.5



In the United States, IPR has been practiced for almost 50 years via surface water augmentation, soil treatment leading to groundwater augmentation, or direct injection into a

potable aquifer. During this time especially during the last 15 years, IPR reuse schemes in

the United States as well as worldwide evolved substantially regarding their capacity and

the type and sequence of treatment processes employed (Table 16-1).

For projects favoring direct injection into a potable aquifer, use of integrated membrane systems (IMS) incorporating microfiltration (MF) or ultrafiltration (UF) followed

by reverse osmosis (RO) have emerged as the industry standard. IPR schemes employing

IMS are mostly located in coastal areas where concentrated waste streams (i.e., RO concentrates) may be conveniently discharged to the ocean. In the United States, Singapore,

and Australia, utilities have favored IMS, in some cases coupled with subsequent advanced

oxidation processes (AOP). For inland surface and groundwater augmentation projects,

however, IMS are favored less due to the lack of waste stream disposal options. Instead,

for these IPR applications various combinations of low-pressure membranes, granular activated carbon (GAC) adsorption/filtration, chemical oxidation (i.e., ozone, UV/AOP), and

natural treatment processes have evolved. These practices underscore that multiple options

exist for the design of IPR schemes that consider regional conditions but are unified in the

goal to lower or eliminate the risk from constituents of concern. Given the nature of the

source, public health concerns regarding IPR are foremost related to the presence of pathogens and trace organic chemicals in reclaimed water. Thus, IPR projects must integrate

appropriate water treatment processes that are capable of providing effective, reliable, and

redundant barriers to pathogens and trace organic chemicals. Fundamental to the design of

IPR schemes is the concept of multiple barriers and an environmental buffer to ensure a

drinking water quality that is fit for human consumption.

Although these technical components are important for any proposed IPR project,

addressing the psychological dimension of IPR (i.e., “toilet to tap,” “yuck factor”) is essential for a successful project. In several cases over the last 15 years, this aspect of IPR

evolved as the determining factor for success or failure of a project and outweighed the

technical merit of some proposed projects resulting in their termination prior to completion

(e.g., San Diego’s Water Recharge Project in 1998; Los Angeles Department of Water and

Power’s East Valley Groundwater Recharge Projectn 1998; Toowoomba’s Water Recycling

Project, Australia, in 2006). From the early phase of a proposed project, communication

with stakeholders and the general public is the key to success, building confidence that IPR

is the best alternative to secure future water supplies and positioning the proposing utility

as the trusted source of water quality (Ruetten et al., 2004).

In planning a successful IPR project, the following activities should be carefully considered: (1) source water characterization, (2) appropriate water treatment process selection,

(3) quantitative relative risk assessment and development of a risk management strategy,

(4) review of institutional and regulatory requirements, (5) communication with stakeholders and the public, and (6) assessment of capital and operational costs.



SOURCE WATER CHARACTERISTICS

Conventional wastewater treatment provides an effluent quality that, in the United States, is

ultimately aimed at meeting the requirements of the Clean Water Act (CWA) and therefore in

most cases is suitable to be discharged to surface waters. However, conventionally treated

effluents remain composed of a wide range of naturally occurring and synthetic, trace

organic and inorganic chemicals, residual nutrients, dissolved solids, and residual heavy

metals, as well as pathogens. Thus, for potable reuse projects, compliance with established

drinking water standards as promulgated by the Safe Drinking Water Act (SDWA) by



16.6



CHAPTER sixteen



conventionally treated and reclaimed wastewater does not imply that the reclaimed water is

safe for human consumption. In some states and depending on the designated use, surface

discharge requirements under the CWA can be more stringent than compliance with SDWA

drinking water standards. For example, the state of California’s Toxics Rule requires more

stringent THM standards (i.e., 5 µg/L instead of 80 µg/L as set by the SDWA) for a reservoir augmentation project discharging to surface water that is designated as a municipal

drinking water supply. Thus, for an IPR project a thorough assessment of the source water

quality is required that includes a wider range of microbial and chemical constituents than

those required by current drinking water standards. Since general water quality characteristics of reclaimed water deviate from those of conventional drinking water sources, water

treatment processes employed in IPR schemes must be capable of mitigating and eliminating these differences. Water produced in IPR schemes using advanced treatment processes

sometimes requires restabilization to reduce the corrosive nature of the water, which may

subsequently lead to deteriorating water quality. The three key elements to maintaining

water quality for an IPR system are source control, attenuation of contaminants of concern

through tailored treatment, and posttreatment stabilization.

Source Control

Source control is an USEPA regulatory management practice undertaken to minimize the

discharge of some pollutants into the sewer. In many cases, wastewater agencies administer

additional pollution prevention policies. These programs are conducted with the goal of

reducing treatment costs, targeting chemicals of concern that are not primarily removed

during conventional wastewater treatment (i.e., heavy metals, trace organic chemicals), and

improving the reliability of final water quality. The approach is analogous to watershed management that may normally be exercised for conventional drinking water catchments (e.g.,

USEPA’s Long Term 2 Enhanced Surface Water Treatment Rule; see Chap. 1). Accordingly,

effective source control practices require the development and execution of a sewer discharge management plan. Monitoring and compliance assessments of point discharges to the

sewer system are the first line of defense in IPR schemes representing the initial component

of a multiple-barrier approach.



Contaminants of Concern

Contaminants of concern encompass a wide variety of pathogenic microbial organisms

and chemical contaminants, which may be present in conventionally treated municipal

effluents. Their presence is generally considered to be of concern due to their potential

deleterious impacts on human health.

Pathogens.  The control of pathogenic organisms is fundamental to the protection of public health for all potable water supplies as presented in Chap. 2. However, in the case

of IPR, where municipal wastewaters make up a major component of source waters, the

presence of significant initial concentrations of pathogens can generally be assumed.

The diversity and concentrations of pathogens in treated wastewater effluents is highly

variable and dependent on numerous locally specific factors. These factors include the

patterns of infection within the community and the type of secondary and tertiary as well

as disinfection processes employed at the wastewater treatment plant. In terms of their

ability to contaminate drinking water supplies and their infectivity, the most significant

human pathogens in reclaimed water include a range of bacteria, viruses, and protozoa as

summarized in Table 16-2.



Water Reuse for Drinking Water Augmentation







16.7



Table 16-2  Examples of Pathogens Occurring in Reclaimed Water

Pathogen type

Bacteria



Viruses



Protozoa



Helminths



Examples

Salmonella

Campylobacter

Pathogenic Escherichia coli

Shigella

Yersinia

Vibrio cholerae

Atypical Mycobacteria

Legionella spp

Staphylococcus aureus

Pseudomonas aeruginosa

Enterovirus

Adenovirus

Rotavirus

Norovirus

Hepatitis A

Calicivirus

Astrovirus

Coronavirus

Cryptosporidium

Giardia

Entamoeba histolytica

Taenia (T. saginata, T. solium)

Ascaris

Trichuris

Ancylostoma



Illness

Gastroenteritis, reactive arthritis

Gastroenteritis, Guillain–Barré syndrome

Gastroenteritis, hemolytic uremic syndrome

Dysentery

Gastroenteritis, septicemia

Cholera

Respiratory illness (hypersensitivity

pneumonitis)

Respiratory illness (pneumonia, Pontiac fever)

Skin, eye, ear infections, septicemia

Skin, eye, ear infections

Gastroenteritis, respiratory illness, nervous

disorders, myocarditis

Gastroenteritis, respiratory illness, eye infections

Gastroenteritis

Gastroenteritis

Infectious hepatitis

Gastroenteritis

Gastroenteritis

Gastroenteritis

Gastroenteritis

Gastroenteritis

Amoebic dysentery

Tapeworm (beef measles), neurocysticercosis

Roundworm

Whipworm

Hookworm



Sources: National Resource Management Ministerial Council et al. (2008), Feacham et al. (1983), Geldreich

(1990), National Research Council (1996), and Bitton (1999).



Waterborne bacteria, such as Campylobacter Shigella, and Salmonella, are important

human pathogens as described in Chap. 2. However, these species are relatively susceptible

to chemical disinfection practices (e.g., chlorination and chloramination; see Chap. 17)

and thus can be effectively controlled by wastewater reclamation processes. Accordingly,

bacteria are not a primary concern or driver to the implementation of advanced treatment

processes in IPR schemes.

Viruses are widely recognized as the microorganisms representing the most significant risks to public health from IPR projects. Although they are generally susceptible to

inactivation by chlorine disinfection, their high particle numbers in municipal wastewaters

(Costan-Longares et al., 2008) and high infectivity require careful management to maintain adequate disinfection. Viruses responsible for numerous human illnesses, including

gastroenteritis and hepatitis A, are known to be commonly present in municipal wastewater

effluents. Effective monitoring presents an additional challenge to virus control since few

laboratories possess the necessary expertise for proper analysis.

The enteric protozoan parasites Cryptosporidium and Giardia are notorious agents of

waterborne disease and are commonly associated with reported outbreaks (see Chap. 2).

Cryptosporidium in particular is reported to have been the cause of illnesses (and sometimes deaths) from drinking water supplies with full conventional treatment (coagulation



16.8



CHAPTER sixteen



and flocculation, granular media filtration, and chlorine disinfection), usually under challenging or erroneous circumstances as reviewed by Hrudey and Hrudey (2007). In water,

protozoa may produce cysts or oocysts that aid in their survival. As a result, some of these

organisms, including Cryptosporidium, are highly resistant to chlorine disinfection and

must generally be controlled by other means, such as ozone oxidation, membrane filtration,

soil-aquifer treatment, or riverbank filtration.

Data regarding the reported occurrence of specific pathogens in reclaimed water is limited and more commonly, so-called indicator organisms are analyzed as surrogate measures

for microbial water quality (see the discussion in the next section, System Reliability and

Health Risk Considerations, and Chap. 2). A study undertaken at three water reclamation

plants in Spain reported the occurrence of the pathogens cytopathogenic enteroviruses and

viable Cryptosporidium oocysts along with a range of potential indicator organisms including total coliforms, E. coli, enterococci, spores of sulphite-reducing clostridia, somatic

coliphages, RNA F-specific phages, phages that infect B. fragilis strain RYC2056, and

phages that infect B. tethaiotaomicron strain GA-17 (Costan-Longares et al., 2008). The

detection limit in both secondary and tertiary effluents was 1 CFU/100 mL for all measured

parameters. All three of the tested facilities employed biological nutrient removal for secondary treatment. Tertiary treatment steps including disinfection were variable—Facility 1:

coagulation/flocculation → sand filters → UV light → chlorine (5 ppm, 45 min); Facility

2: settling ponds → oxidation ponds → constructed wetlands; Facility 3A: coagulation/

flocculation → sedimentation → multilayer filtration → UV, chlorine (0.3 ppm, 1 min);

Facility 3B: coagulation/flocculation → sedimentatation → multilayer filtration → chlorine (18 ppm, 90 min). Geometric mean densities of pathogens and indicator organisms,

expressed as log (base 10) units, after secondary (prior to disinfection) and tertiary (after

disinfection) treatment are illustrated in Fig. 16-1. Mean log reductions observed in this

study for pathogens and microbial indicators during tertiary treatment are illustrated in Fig. 16-2.

Although tertiary treatment processes were efficient in inactivating microbial indicators,

these processes did not provide a pathogen-free water. Therefore, additional barriers for

pathogens are needed in IPR applications.

Total Dissolved Solids.  Domestic and commercial uses of public water supplies result

in an increase of the mineral content in municipal wastewater. In some areas, the use of

water softeners may be the major source of an increase in total dissolved solids (TDS). The

increase in TDS in municipal wastewater effluents results in concentrations that are approximately 150 to 350 mg/L higher than the original potable water supplies (Asano et al., 2007).

In a study reported by Drewes and Fox (2001), contributions of major ions in reclaimed

water through human activities resulted in an average increase of 75 mg/L sodium, 45 mg/L

sulfate, and 75 mg/L chloride, with small changes in hardness and minor ions.

In order to mitigate salinity problems associated with local water reuse activities, especially in inland applications, partial desalination of reclaimed water in IPR schemes may

be required. For this reason, groundwater recharge schemes in Orange County, California,

incorporated RO to reduce the concentration of dissolved solids to meet the groundwater

basin objective for dissolved solids, which was equivalent to the USEPA drinking water

secondary standard of 500 mg/L (USEPA, 1991).

Nutrients.  Treated municipal effluents may contain numerous forms of nutrients that,

if uncontrolled, may lead to excessive eutrophication of drinking water reservoirs in surface water augmentation projects. The most significant growth-limiting nutrients are most

commonly nitrogen and phosphorus; however, other important micronutrients include

potassium, calcium, magnesium, and sulfur. The risk of eutrophication can be managed

by reducing the concentration of phosphorus and nitrogenous compounds through various

treatment processes.



16.9



Water Reuse for Drinking Water Augmentation







95% IC Log10 concentrations in

secondary effluents



A



8

7

6

5

4

3

2

1

0

–1

–2

–3



100 100 100 100 100 100 100



50



94



Percentage

of positive

samples



8)

(4

P

RY

C

8)

)

(4 (47

EV PH

7)

A

(4

G



PH



C

RY



BT



BF



AP



LI



O



C



C



M



N



FR



SO



PH



8)



8)



8)



(4



(4



87



H



PH



94



(4



8)



95% IC Log10 concentrations in

tertiary effluents



100



SR



(4



8)

92



FE



(4



8)

47



EC



(4



57



8)

69



TC



(4



C



SR



FE



EC



TC



B



98



8

7

6

5

4

3

2

1

0

–1

–2

–3



97



41



59



32



72



Percentage

of positive

samples



0)

(6

P

RY

C

0)

)

(6 (63

EV PH

3)

A

(6

G

BT PH

C

RY 63)

BF H (

)

P

LI (63

O

C PH )

A

3

N

(6

FR PH

C

M

SO 61)

(

C



2)

(6

2)



(6



1)

(6



Figure 16-1  Microorganism concentrations (mean values and 95 percent confidence levels) in secondary (prior to disinfection) (a) and tertiary effluents (after disinfection) (b). In brackets is the number

of analysis performed for every parameter. Indicator microorganisms’ concentrations are expressed in

PFU/100 mL and pathogens concentrations in PFU/1L. TC: total coliforms, EC: E. coli, FE: fecal enterococci, SRC: sulphite reducing clostridia, SOMCPH: coliphages infecting E. coli WG5, FRNAPH: FD RNA

specific phages, BFRYCPH: phages that infect Bacteroides fragilis strain RYC 2056, BTGA17PH: phages

that infect Bacteroides tethaiotaomicron strain GA-17, EV: cytopathogenic enteroviruses, CRYP: viable

Cryptosporidium oocysts. (Source: adapted with permission from Costan-Longares et al. (2008), copyright

2008, Elsevier.)



16.10



CHAPTER sixteen



95% IC Log10 units reductions



6

5

4

3

2

1

0



7)

(5

P

RY

C

8)

)

(3 (62

EV H

)

AP (61

G

BT PH

C

RY 63)

BF H (

P

3)

LI

(6

O

C PH

A

3)

N

(6

FR PH

C

M

SO 63)

(



2)



2)



(6



(6



1)



(6



C



SR



EF



EC



TC



Figure 16-2  Microbial inactivation (log10 units reductions) obtained in tertiary treatments studied. (Source: adapted with permission from Costan-Longares et al. (2008), copyright 2008, Elsevier.)



In reclaimed water, nitrogen (N) may be present in both ionic and non-ionic forms.

The speciation and concentrations will depend on pH, redox conditions, and the efficiency

of any BNR process deployed at the wastewater treatment plant. Cationic nitrogenous

compounds include ammonium (in equilibrium with ammonia) and amines; anionic forms

include nitrite, nitrate, and amino acids. A well-operated biological nutrient removal (BNR)

process would be expected to produce an effluent with negligible amounts of ammonia,

less than 5 mg/L of nitrate and nitrite and less than 1 mg/L of organic N (Table 16-3).

Table 16-3  Biological Nutrient Removal (BNR) Treatment Processes and Common

Concentration Ranges of Nutrients in Reclaimed Water



BNR

treatment

processes



Range of

dissolved

Range of

organic

3–

PO4 – P

Range of NH4 Range of NO3 nitrogen (DON)

concentration concentration concentration concentration

(mg N/L)

(mg N/L)

(mg N/L)

(mg P/L)



Not nitrifying



15–45



0.1–5



0.3–1.7



1–8



Partially

nitrifying

Nitrifying/

denitrifying

Chemical

P-removal

Biological

P-removal



0.1–10



5–20



0.3–1.3



0.4–8



<0.1–2



0.5–8



0.2–0.7



0.4–8



<0.1–10



5–20



0.3–1.3



<0.3–1.5



<0.1–2



0.5–8



0.2–0.7



<0.1–0.6



References

Sedlak, 1991

Krasner et al., 2008

Sedlak, 1991

Krasner et al., 2008

Sedlak, 1991

Krasner et al., 2008

Sedlak, 1991

Krasner et al., 2008

Sedlak, 1991

Krasner et al., 2008







Water Reuse for Drinking Water Augmentation



16.11



Advanced treatment processes that achieve additional nitrogen reduction are membrane

separation (e.g., RO, nanofiltration (NF), and electrodialysis), ion-exchange processes, and

biologically active filters.

Phosphorus (P) is present in reclaimed water predominantly as organic P and inorganic

orthophosphate. Phosphorus may be partially removed biologically in the anaerobic zone of

a BNR process. Residual orthophosphate may be removed in the treatment plant by precipitation and filtration using ferric or aluminum salts. Typical phosphorus concentrations in a

BNR effluent designed for both nitrogen and phosphorus removal are in the 0.5 to 2.0 mg/L

P range, decreasing to <0.3 mg/L if media filters are used (Table 16-3) (Sedlak, 1991).

Dissolved Organic Chemicals.  The overall load of organic chemicals in water can be

quantified in terms of the total organic carbon (TOC) concentration. Dissolved organic

chemicals are described after 0.45 µm microfiltration as dissolved organic carbon (DOC)

concentration. DOC in municipal wastewater effluents is composed of natural organic

matter (originating from drinking water), soluble microbial products (generated during

the activated sludge process), and small concentrations of a very large number of individual organic chemical contaminants (Namkung and Rittman, 1986; Drewes and Fox,

2000). These contaminants include industrial and domestic chemicals (e.g., pesticides,

personal care products, preservatives, surfactants, flame retardants, perfluorochemicals,

nanoparticles; see Chap. 2 regarding health effects and Chap. 3 regarding their presence in

source waters), and chemicals excreted by humans (e.g., pharmaceutical residues, steroidal

hormones), as well as chemicals formed during wastewater and drinking water treatment

processes (e.g., disinfection by-products; see Chap. 19). Some representative examples of

trace organic chemicals that may be present in treated municipal effluents are summarized

in Table 16-4. Chemical contaminants may be present in reclaimed source waters or may

be formed as by-products or metabolites via chemical or biological transformation during wastewater collection and treatment. Many of these chemicals may have an adverse

effect on human health if present in sufficient quantities and not effectively removed during treatment (see Chap. 2). Potential chronic adverse health effects include carcinogenic,

toxicologic, embryonic, and reproductive development impacts caused by interference with

the endocrine system.

Anionic surfactants are used in commercial and domestic detergent products.

Applications include dishwashing and clothes-washing detergents as well as hair shampoos. Linear alkylbenzene sulphonates (LAS) are the most common. Anionic surfactants

are often present in high concentrations in raw wastewater (1–20 mg/L). However, conventional wastewater treatment is effective at eliminating these compounds resulting in much

lower concentrations in final effluents. Drewes et al. (2009) studied the fate of LAS in six

full-scale wastewater treatment plants and reported average concentrations in raw sewage

of almost 6 mg/L that were reduced to approximately 4 µg/L in treated effluents.

Depending on the service area and the extent of the source control program to minimize

discharge of chemicals at the source, a wide range of synthetic industrial chemicals are

often measurable in influents to a water reclamation plant. Examples include plasticizers

and heat stabilizers, biocides, epoxy resins, bleaching chemicals and by-products, solvents,

degreasers, dyes, chelating agents, polymers, polyaromatic hydrocarbons, polychlorinated

biphenyls, and phthalates. Many of these chemicals are known to be toxic to a diverse range

of organisms including humans. Biological processes, however, can significantly reduce

these contaminants in reclaimed water to levels usually below drinking water maximum

contaminant levels (Trenholm et al., 2008).

Volatile organic compounds (VOCs) are widely used as industrial solvents. Many are

constituents of petrochemical products, and a number of halogenated compounds may be

formed as by-products of chlorine disinfection. Some VOCs are suspected to be teratogenic or carcinogenic to humans. Because of their high potential to contaminate traditional



Table 16-4  Examples of Trace Organic Chemicals That May be Present in Reclaimed Water

Category



Representative examples



Organic chemicals



16.12



Surfactants

Industrial products and

by-products



Alkane ethoxy sulphonates (AES)

Acrylamide

Alkyl phenols

Alkyltin compounds

Bisphenol A

Chlorinated dioxins

Chlorobenzene



Volatile organics



Benzene

Carbon tetrachloride

Dichloroethanes

Dichloromethane

2,4-D

Aldicarb

Aldrin/dieldrin

Atrazine

Chlordane



Pesticides or their metabolites



Algal toxins

Disinfection by-products



Cylindrospermopsin

Microcystins

Chloral hydrate

Chlorate

Chlorine dioxide

Chlorite

Chlorophenols

Chloropicrin



Linear alkylbenzene sulphonates (LAS)

Dichlorobenzenes

Ethylenediaminetetraacetic acid (EDTA)

Epichlorohydrin

Hexachloro-butadiene

Nitrilotriacetic acid

Perfluorooctanoic acid (PFOA)

Perfluorooctane sulfonate (PFOS)

Ethylbenzene

Tetrachloroethene

Toluene

1,1,1-trichloroethane

Chlorpyrifos

Diazinon

Dichloro-diphenyltrichloroethane (DDT)

Diuron

Endosulfan



Secondary alkanesulphonates

Phthalates

Polyaromatic hydrocarbons

Polychlorinated biphenyls

Styrene

Trichlorobenzenes

Vinyl chloride monomer



Nodularin



Saxitoxins



Cyanogen

Formaldehyde

Haloacetic acids

Haloacetonitriles

Haloaldehydes

Halogenated furanones



Haloketones

Monochloramine

Nitrosamines

- Nitrosodimethylamine (NDMA)

Trihalomethanes



Trichloroethene

Xylenes



Heptachlor and epoxide

Lindane

Organic mercurials

Pyrethroids

Other insecticides, fungicides and herbicides