Transcript Slide 1

PNWS AWWA 2008 Annual Conference
Vancouver, Washington
Contaminants of Emerging Concern
in Water and Wastewater Treatment
John Bratby
Brown and Caldwell
Contaminants of Emerging Concern in
Water and Wastewater Treatment
 Nature
of CECs
 Removal mechanisms of CECs
 Removal efficiencies of CECs during
treatment
 Do membrane bioreactors provide
enhanced removal of CECs?
 Other advanced treatment for higher
levels of CEC removal
Recent AP article
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“Mary Buzby -- director of environmental technology for drug
maker Merck & Co. Inc.: "There's no doubt about it, pharmaceuticals
are being detected in the environment and there is genuine concern that
these compounds….could be causing impacts to human health or to
aquatic organisms.“
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Recent laboratory research has found that small amounts of
medication have affected human embryonic kidney cells,
human blood cells and human breast cancer cells. The
cancer cells proliferated too quickly; the kidney cells grew too
slowly; and the blood cells showed biological activity
associated with inflammation.
Some scientists stress … that the documented health
problems in wildlife are disconcerting.
Removal Pathways of Groups of CECs
in Wastewater Treatment
 Steroid
compounds
 Phytoestrogens
 Surfactants
 Pesticides, herbicides, fungicides
 Polyaromatic compounds
 Organic oxygen compounds (Bisphenol A,
Phthalates, Dioxins, Organotins)
Potency of Steroid Compounds
EDC
Lowest observed effective
concentration (LOEC) Rainbow trout
WWTP effluent
concentrations
Estradiol
1 ng/l
<0.2 - 3 ng/l
Ethinyl estradiol
0.1 ng/l
<0.2 - 3 ng/l
Nonylphenol
14,000 ng/l
<80 - 923 ng/l
Bisphenol A
25,000 ng/l
8 - 33 ng/l
(German study - Berlin-Ruhleben WWTP - Hansen et al, 1998)
Surfactants
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Main surfactants of interest for ED are the alkylphenols (APs) and
their ethoxylates (APEOs) – particularly the nonylphenol (NP)
compounds
Alkyl Phenol Ethoxylates (APEO) widely used in industries as well
as commercial and household functions
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Detergents, lubrication, defoamers, emulsifiers, paints, pesticides
Cleaners for machinery, metal working, textiles, and personal products
Nonylphenol ethoxylate is the most common
APEOs tend to be degraded to more potent endocrine disrupting
compounds during wastewater treatment
 The ethoxylates can be degraded to produce NP which is more
persistent and toxic than the ethoxylates
Highest freshwater concentrations of NP observed near WWTPs,
pulp mills, and regions of heavy industry
Pesticides
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Largest group of EDCs
 DDT, dieldrin, 2,4-D, tributyltin, atrazine, metolachlor,
cyanazine, alachlor
 All herbicides, fungicides, pesticides
 Atrazine one of the most difficult to remove
Understand Properties to
Predict Physical Processes
Property
Potential
Units
Low
High
Water Solubility
Dissolving
mg/l
<1
1000
Henry's Law Constant
Evaporation/
Volatilization
atm m3/mole
>10-2
<10-7
Degradation
log Koc
<3
>3
Sorption
log Kow
<2.5
>4
Organic/Carbon
Partition Coefficient
Log octanol/water
partition
Kow values are an indicator of hydrophobicity, and have been
used as a surrogate for removal during water treatment
CEC removal in Biological Treatment
– Dependent on parameters such as:
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Temperature
Sludge age, SRT
HRT
Influent concentrations
Co-metabolite transformations
Treatment type (AS, TF, MBRs)
 Probably lower EDC concentrations from MBR
systems due to retention of both particulate and
colloidal material. Membrane systems appear to
form colloid complexes to a greater extent than
conventional systems
WWTP Removals for Select EDCs
EDC
PCB
NP
NP1EO
NP2EO
NP6EO
NP2EO
Steroid estrogen - E1
Treatment Process
Removal Efficiency
Trickling filter (TF)
90%
Activated sludge (AS)
96%
TF-AS
99%
AS - High load non-nitrifying
37%
As - Low load nitrifying
77%
AS - High load non-nitrifying
-3%
AS - Low load nitrifying
31%
AS - High load non-nitrifying
-5%
AS - Low load nitrifying
91%
AS - High load non-nitrifying
78%
AS - Low load nitrifying
98%
AS - High load non-nitrifying
-5%
AS - Low load nitrifying
91%
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AS - SRT 6 to 11 days, 20 C
75 to 98%
AS - SRT 6 to 11 days, 20oC
17 estradiol/17 ethinylestradiol Sand filtration - Microfiltration
(removals from influent)
Reverse osmosis
75 to 94%
Steroid estrogen - E2
Organotins
Triazines
70%
95%
Primary treatment
-5%
Secondary treatment
91%
Tertiary treatment
98%
Conventional two stage
<40%
Removals of E1 and E2
reduced to 64 to 94% at
15oC (SRT 6 to 11 d)
Removal Rates of Steroid Estrogens at
Varying Retention Times
13 - 15 ºC
E1 Loss
E2 Loss
18 - 19 ºC
E1 Loss
E2 Loss
18-hour HRT
6-day SRT
64%
92%
75%
-
18-hour HRT
11-day SRT
94%
98%
>98%
-
26-hour HRT
20-day SRT
66%
>75%
98%
>94%
From: Johnson A.C., Belfroid
A., Di Corcia A. (2000)
Influent and Effluent Concentrations of
Alkylphenolic Compounds in WWTPs
WWTP
Location
Switzerland
Number
of
WWTPs
Type of
Plants
Influent
Concentration
(µg/l)
Effluent
Concentration
(µg/l)
<10 - 35 NP
24 - 133 NP1EO
<10 - 70 NP2EO
3
14 NP
18 NP1EO
18 NP2EO
8 NP
49 NP1EO
44 NP2EO
Switzerland
1
Mechanical biological
Switzerland
5
Mechanical 844 - 2250 NPEO + NP 40 - 369 NPEO + NP
biological
Switzerland
11
U.K.
12
Italy
1
U.S.
1
1090 - 2060 NP
240 - 760 NP
<0.2 - 330 NP
Mechanical biological
800 NPEO
8 NPEO
143 - 272 NPEC
Acclimation Times Required for NTA
Removal With Activated Sludge Treatment
4
NTA Influent
Concentration
(mg/l)
7.5
4
15
-
20
9
7.5
3049
12
9
15
-
12
7.5
3536
16
6
SRT
(days)
MLSS
(mg/l)
Acclimation Time
(days)
1514
15
NTA – Nitrilotriacetic acid – considered as a
detergent builder in place of phosphates
From: Rossin A.C., Lester J.N.,
Perry R. (1982)
Comparison between MBR and CAS systems
(from Scruggs C. et al., WE&T, March 2005; Mansell et al., WEFTEC, 2005):
Hormones: Removal comparison between MBR
and CAS systems (from Mansell et al., WEFTEC, 2005):
CEC removal: Advanced treatment
processes following secondary treatment
Granular
activated
carbon
Advanced
oxidation
Reverse
osmosis
Coagulation or Chemical Precipitation
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Most compounds of concern are relatively polar (Kow
values < 3)
Neither alum or iron coagulation or lime softening
effective for atrazine or antibiotic removals
Coagulation ineffective with several pharmaceuticals
and with several pesticides
Some pesticides (PAHs pyrene, fluoranthene and
anthracene) removed ~50% by coagulation
Coagulation only expected to remove hydrophobic
compounds associated with particulate or colloidal
material
EDCs and PPCPs not associated with colloidal or
particulate material very poorly removed (<10%)
Adsorption
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Activated carbon (AC) effective for many different
pesticides, PPCPs and EDCs
Hydrophobic interactions dominant mechanism (weak
ion exchange interactions also contribute to
adsorption)
AC can remove neutral organic compounds with
hydrophobic compounds (logKow>2)
NOM in water competes for adsorption sites and
decreases AC effectiveness for micropollutants
PAC can be effective; GAC probably more efficient
PAC could be good emergency measure at WTPs,
particularly during low streamflow, and with upstream
wastewater discharges
Membrane Filtration
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Most organic EDCs and PPCPs are 150 to 500
daltons
 Most can be removed in RO and tight NF
membranes
 Microfiltration and ultrafiltration will only remove
those EDCs and PPCPs associated with colloidal
and particulate matter
 Polar and charged compounds that interact with
membrane surfaces will be better removed
 Hydrophobicity also affects removals. Removals
by RO and NF membranes correlates with logKow
Effectiveness of
Treatment
Processes with
Some CECs
Treatment
Process
Effluent
Comments
EDCs
GAC
APs, APEOs, PCP,
methoxychlor,
endosulfan, diethyl
phthalate, di-(2ethyl
hexyl) phthalate,
PCBs
EPA BAT for
some
contaminants
Reverse
osmosis
Alkylphenol
polyethoxy
carboxylates
(APnECs), PCP
Most EDC
compounds
removed by RO.
UV+catalyst
APs, bisphenol A,
E2, EE2, lindane,
2,4-D,
Off-gas
Effluent to
be treated
Targeted
Ozone+H2O2
Atrazine
2 min. EBCT.
EU regs may not
be met
Coagulation,
sedimentation
and filtration
2,3,7,8 TCDD
Adsorbed to floc
particles
General removal efficiencies of
treatment processes
EDC
Classification
Coagulation/
Flocculation
Softening/
metal oxides
CL2/
ClO2
UV
Ozone/ Activated
AOPs
Carbon
BAC
NF
RO
Pesticides
<20%
70-90%
70->90%
>90%
20->90%
>90%
>90%
70->90%
>90%
Industrial
chemicals
<20-40%
<20-40%
<20%
>90%
40-90%
>90%
>90%
>90%
>90%
Steroids
<20%
<20-40%
>90%
>90%
>90%
>90%
>90%
70->90%
>90%
Metals
40-90%
40-90%
<20%
<20%
<20%
70-90%
70-90% 70->90%
>90%
Inorganics
<20%
70-90%
<20%
<20%
<20%
<20-40%
40-70% 70->90%
>90%
Organometalics
<20-40%
<20-40%
<20-70% 40-90% 20->90% 70->90% 70->90% 70->90%
>90%