America’s Authority in Membrane Treatment

Membranes Technologies Address Emerging Contaminants Overview

Research is documenting with

increasing frequency that many

inorganic, organic and microbial

constituents that have not historically

been considered as contaminants are

present in the environment at low

quantities on a global scale. These

“emerging contaminants” are

commonly derived from municipal,

agricultural, and industrial wastewater

sources and pathways. These newly

recognized contaminants represent a

shift in traditional thinking as many are

produced industrially yet are dispersed

to the environment from domestic,

commercial, and industrial uses.

Emerging contaminants will affect

current and future treatment

technologies utilized by the drinking

water community. Membrane processes

will be carefully examined, possibly as

a tool in the tool box, in order to deal

with these contaminant removal

challenges.

What are emerging contaminants

and where did they come from?

Advanced analytical capabilities have

allowed scientists to identify chemicals

in the environment at extremely low

concentrations. Emerging contaminants

(ECs) are those chemicals that recently

have been shown to occur widely in

water resources and identified as being

a potential environmental or public

health risks. ECs are used every day in

our homes, on our gardens, by

agricultural and other businesses and

industry. ECs include detergents,

fragrances, personal care products,

prescription and non- prescription

drugs, disinfectants and disinfection

by-products, pesticides, herbicides and

Nano-materials. The occurrence of

emerging contaminants correlates with

ecological effects and sexual

abnormalities in fish, although a

cause-and-effect relation has not been

confirmed nor links between ECs and

the environment been specifically

established. For example, we

acknowledge that the feminization of

fish and amphibians has been linked to

exposure to compounds that mimic

estrogen activity; however, it has also

been determined that thousands of

compounds have the potential to

interact with components of the

endocrine system altering the natural

action of the hormone. Table 1 presents

a partial listing of emerging

contaminants found in wastewater

effluent and the aquatic environment.

The recent EPA Contaminant

Candidate List (CCL) selected 116

candidates, many of which also fit in

this category.

A study conducted by the U.S.

Geological Survey as part of its’ Toxic

Substances Hydrology Program did,

however, detect 82 chemicals in 80

percent of 139 streams and waterways

tested between 1999 and 2000. The

most common chemicals were steroids

(anti-inflammatory drugs), antibiotics,

nonprescription drugs, caffeine and

insect repellent. Potential water quality

contaminants originated from

wastewater discharges, run-off from

agricultural and industrial land uses and

discharge from individual septic

systems. Emerging chemical

contaminants, such as industrial solvent

stabilizers (1,4-dioxane), fuel

oxygenates (MTBE and TBA),

disinfection byproducts (NDMA),

pharmaceuticals (antibiotics/ drugs),

personal care products (polycyclic

musks), pesticides and herbicides

(1,2,3- trichloropropane), algal toxins,

emerging pathogens, and other

persistent compounds such as flame

retardants (PBDEs) and phthalates,

illustrate many technical and

institutional challenges.

Membrane processes offer promise

for resolving many emerging

contaminant concerns

Conventional wastewater treatment

varies greatly in its ability to eliminate

drug or personal care product residues.

Additional treatment may be required

in the future either at the effluent

discharge location or prior to the

point-of-entry to the drinking water

distribution system. Membranes are

effective for the treatment of organic

precursor matter and show promise for

meeting removal targets for emerging

contaminants.

Although there are several mechanisms

affecting contaminate removal by

membranes, size exclusion is very

significant and can be used to describe

membrane capability. If the

contaminant is too large to pass through

the membrane pore, then it is removed

from permeate or filtrate streams.

Contaminants can be categorized

simply as microbiological (i.e.

pathogens), organic solutes, and

inorganic solutes. Pathogens can be

subdivided into cysts, bacteria and

viruses. Organics can be subdivided

into DBPs and their total organic

carbon (TOC) natural precursors,

synthetic organic compounds (SOCs)

and volatile organic chemicals (VOCs).

Inorganic parameters refer to such

contaminants as total dissolved solids,

total hardness, heavy metals and other

inorganic contaminants.

Reverse osmosis (RO) and

nanofiltration (NF) are pressure driven

membrane processes that can remove

contaminants to 0.0001 µm and 0.001

µm respectively. RO and NF are both

diffusion and size exclusion controlled

processes. However, no process is

capable of absolute removal.

RO and NF processes have the broadest

span of treatment capability but require

the greatest degree of pretreatment.

Ultrafiltration (UF) membranes can

achieve greater than six-log removal of

all pathogens from drinking water

whereas microfiltration (MF) can

achieve greater than six-log removal of

cysts. Consequently, membrane

processes are ideal for removing

|turbidity and microbiological

contaminants, and they are well suited

for treating the majority of drinking

water sources in the United States.

Membrane processes do not remove

dissolved gases such as methane,

carbon dioxide and hydrogen sulfide.

Log rejection will increase as flux

increases and decrease as recovery

increases in diffusion controlled

membrane processes (primarily NF and

RO). No change will occur in size

exclusion controlled processes

(primarily MF and UF). Pathogen

removal by NF or RO is controlled by a

size exclusion mechanism, whereas ion

removal is diffusion controlled.

Removal of organic compounds

exhibits both mechanisms. Diffusion

controlled processes would have the

flexibility of decreasing recovery to

produce a higher water quality if more

feed water could be drawn to meet

demand.

Table 2 presents examples of treatment

effectiveness for NF and RO with

regards to specific endocrine disruptors.

Membranes have distinct treatment

advantages relative to these and other

emerging contaminants. RO or NF

membranes are capable of meeting the

EPA’s DBP maximum contaminant

levels by removing enough total

organic carbon (TOC) or other DBP

precursors such that free chorine can be

used for disinfection without exceeding

regulated levels within the distribution

system. Pressure driven membrane

processes can reject five to six logs of

viruses, bacteria or cysts, exceeding

most if not all treatment capabilities of

any other single process.

RO or NF membranes can reject small

molecular weight pesticides, are used to

meet stringent European standards and

will likely reject the higher molecular

weight pharmaceuticals (PHACs),

endocrine disruptors, algal toxins, and

similar compounds. There are no

significant water quality disadvantages

to membrane utilization.

The significant membrane

disadvantages are well-known cost and

concentrate disposal issues. However,

costs have reduced due to technological

innovation and concentrate disposal is

not a technical but regulatory burden.

Membranes can meet or exceed current

and pending water quality regulations.

The fundamental question that society

will have to answer is “How much are

we willing to pay for actual, or

perceived, water quality treatment

needs.”

Emerging contaminant issues will

continue to evolve

Unregulated and emerging chemical

contaminants present numerous

technical and institutional challenges to

environmental and public health

professionals. Increasingly advanced

analytical techniques have documented

the emergence of newly detected

inorganic, organic and microbial

chemicals in actual or potential sources

of drinking water.

As our ability to detect these agents has

improved, the number of contaminants

that need to be evaluated for potential

health risks has grown dramatically.

Despite these advances, many

contaminants remain unregulated, and

the number of such unregulated

contaminants will continue to increase

in the future. Consequently,

environmental professionals must make

difficult risk management decisions

regarding water resource and water

supply management issues in the face

of considerable regulatory uncertainty.

While some technologies do not

effectively remove many of these

contaminants from water, membrane

technologies have been shown to be

effective in removing many of the ECs

of concern as either stand-alone

processes or when integrated with other

advanced technologies. Risk

management decisions in the future will

require complex assessments of the

vulnerability of a water supply source

to unregulated contaminants and

include an analysis of the appropriate

combination of treatment processes

required to meet both current and future

water quality concerns arising due to

these contaminants. Cost must always

be considered in the final analysis.

Sources utilized in this fact sheet:

Majority of the data for this fact

from a publication by Dr.

Steve Duranceau who is past

President of AMTA, and is one of

the founding members of the SEDA

and SWMOA.

B. Half o rd. “Side Ef fects”

and Engineering News

(C&EN) Vol 86., No. 8,

February 25, 2008 p. 13-17.

EPA/625/R-00/015 Removal of

Endocrine Disruptor Chemicals

Using Drinking Wa ter r tment

ocesses. March 2001. Washington

DC.

George , E and Y. Li “Emerging

Contaminants in Ground & Surface

Waters” NEHA Annual Educational

Conference, Anchorage, Alaska, May

11, 2004

Andaluri, G. et al. “Pharmaceutical

Chemical Contaminants in Surface

Waters and their Aqueous

Destruction Using Ultrasound.”

AWWA Annual Conference,

Toronto, Ontario, Canada;

June 24-28, 2007

J. Oppenheimer and R. Stephenson.

“Emerging Contaminants: Insights to

the most effective EDC and PPCP

Treatment Strategies.” Opflow,

Vol. 34, No. 5, May 2008.

K.A. Reynolds. “Concern of

Pharmaceuticals in Drinking Water.”

Water Conditioning and Purification,

Vol. 50, No. 4, April 2008.

Pontius, F. USEPA EDC Workshop,

Jan. 29-30, 2002; Cincinnati, OH

S. Snyder, P. Westerhoff et al.

Removal of EDCs and

Pharmaceuticals in Drinking and

Reuse Treatment Processes. Denver,

CO: Awwa Research Foundation,

2007.

S. Snyder, B.J. Vanderford et al.

State of Knowledge of Endocrine

Disruptors and Pharmaceuticals in

Drinking Water. Denver, CO: Awwa

Research Foundation, 2008.

Tabe et al. “Occurrence of PPCPs

and EDCs in Detroit River and Their

Removal Using Ozone Processes.”

AWWA Annual Conference,

Toronto, Ontario, Canada;

June 24-28, 2007.

This material has been prepared as an

educational tool by the American Membrane

Technology Association (AMTA). It is

designed for dissemination to the public to

further the understanding of the contribution

that membrane water treatment technologies

can make toward improving the quality of

water supplies in the US and throughout the

world.

For more information, please contact:

American Membrane Technology

Association (AMTA)

2409 SE Dixie Highway

Stuart, Florida 34996

Phone: (772) 463-0820

Fax: (772) 463-0860

Email: admin@amtaorg.com

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(FS-18) Nov. 2011