ENVR 419Chemical Equilibria of Natural Waters

Fall 201011:00-12:15 Tu/Th

2. Purification of Water

•Drinking Water•Wastewater•Contaminated Groundwater

Sources of Drinking Water

•Fresh Water•Ground Water•Surface Water

-Rivers and streams-Lakes and impoundments

•Brackish Water •Reclaimed Wastewater?•Importance of Watershed Protection

Potential Contaminants in Drinking Water

•Pathogenic microorganisms•Bacteria (salmonella, cholera), viruses (Hepatitis A virus, poliovirus), protozoan cysts (Giardia, Cryptosporidium)

•Suspended particles (turbidity)•Dissolved inorganic contaminants

•e.g. Fe, Mn, As, Cr, Cu, Pb, NO3-, ClO4

-

•Dissolved organic contaminants•e.g. taste and odor-causing organics, pesticides, pharmaceutically active compounds

Objectives of Drinking Water Treatment

•Removal of particulate material•Removal of color (natural organic material, humic

substances arising from vegetative decay)•Removal of taste and odor-causing substances•Removal of harmful contaminants - chemical and microbial•Residual protection of water during distribution - protect against microbial recontamination, corrosion

Chemicals Used in Water Treatment•Coagulants

•Aluminum, ferric salts•Polymers

•Disinfectants•Chlorine, chlorine dioxide, ozone•(UV-Irradiation)

•Acids/Bases for pH adjustment•Lime, caustic•Sulfuric Acid

•Corrosion Control •Phosphates, silicates

•Other•Fluoride

MEMBRANE

Feed Water Filtered Water(Permeate)

Membrane Filtration Thin barrier or film of material that allows certain Thin barrier or film of material that allows certain

substances to pass through while rejecting other substances to pass through while rejecting other substances.substances.

Membrane Removal Functions • Microfiltration (MF)

– particles, bacteria, cysts

• Ultrafiltration (UF)– viruses and colloids

• Nanofiltration (NF)– viruses; natural organic matter; SOCs; hardness

• Reverse Osmosis (RO)– dissolved minerals (desalination)

Membrane Filtration ComparisonFeed WaterFeed Water

RO

NF

UF

MF

Particles, Giardia, Cryptosporidium

Some Viruses

DOC, Hardness

Minerals

Water

Objectives of Wastewater Treatment

•Removal of suspended solids•Removal of oxygen-demanding material

•CBOD (e.g. CH2O), NOD (NH3)

•Removal of nutrients that can promote algal growth, eutrophication

•Nitrogen, phosphorus

•Removal of toxic substances•Disinfection

Dissolved Oxygen Depletion(Oxygen Demand)

Carbonaceous oxygen demand (CBOD)CH2O + O2 = CO2 + H2O

C6H5OH + 7O2 = 6CO2 + 3H2O

Nitrogenous oxygen demand (NOD)NH4

+ + 2O2 = NO3- + H2O + 2H+

Chemical oxygen demand (COD) 3CH2O + 2Cr2O7

2- +16H+ = 3CO2 + 4Cr3+ + 11H2O

d[C]/dt = -kL[CBOD] - kN [NOD] + kH (Cs-C)where C = dissolved oxygen concentrationCBOD = carbonaceous oxygen demandNOD = nitrogenous oxygen demandCs = dissolved oxygen saturation concentration

Dissolved oxygen sag curve

Nutrient Enrichment of Surface Waters and Eutrophication

•PhotosynthesisCO2 + NO3

- + PO43- + H2O Algae biomass + O2

(C106H263O110N16P)

•RespirationAlgal biomass + O2 CO2 + NO3

- + PO43- + H2O

Ace

tam

ino

ph

en

Caf

fein

e

ibu

pro

fen

Tet

racy

clin

e

EE

2

DE

ET

tric

losa

n

Cip

rofl

oxa

cin

Lev

ofl

oxa

cin

dic

lofe

nac

Tri

met

ho

pri

m

Lin

com

ycin

Ery

thro

myc

in

Pri

mid

on

e

Car

bam

azep

ine

Rem

ova

l eff

icie

nc

y

Su

lfam

eth

oxa

zole

100%

80%

60%

40%

20%

0%

-20%

9 9 4 7 4 9 4 9 8 9 4 11 8 6 9 10n=

90th percentile

25th percentile

75th percentile

10th percentile

Median

outlier

Figure 4.23 Percent removal of PPCPs by activated sludge and microfiltration processes. (The value ‘n’ represents the number of samples that were analyzed.)

Lin

com

ycin

Lev

ofl

oxa

cin

dic

lofe

nac

ibu

pro

fen

Tri

met

ho

pri

m

Cip

rofl

oxa

cin

Ery

thro

myc

in

Car

bam

azep

ine

Caf

fein

e

Pri

mid

on

e

DE

ET

Rem

ova

l eff

icie

ncy

100%

80%

60%

40%

20%

0%

-20%

Log Kow

4.51 3.973.06

2.45

2.18

-0.39 0.56 0.91 0.28 -0.07 0.91

n=8 n=9 n=10 n=3 n=7 n=8 n=9 n=11 n=10 n=9 n=10

Figure 4.24 Removal of PPCPs by GAC adsorption. (The values shown on the figure are the logs of the octanol-water partition coefficients (log Kow) for the PPCPs indicated.

The value ‘n’ represents the number of samples that were analyzed and met the quality

N

NH2OH2N

SNH

OOON

N

N N

N

O

O

NH

HN

O

O

Tri

met

ho

pri

m

Car

bam

azep

ine

Ery

thro

myc

in

Cip

rofl

oxa

cin

Caf

fein

e

Pri

mid

on

e

DE

ET

Re

mo

val e

ffic

ien

cy

100%

80%

60%

40%

20%

0%

-20%

Su

lfam

eth

oxa

zole

kO3 (M-1s-1)

2.7x105

3x105

2.5x106

1.9x104

0.82 (pH 8)

1.04

O

N

N N

F

NH

HO

O O

N

NH3CO

H3CO

OCH3

NH2

NH2

Figure 4.27 Comparison of PPCP removal by ozonation with ozonation rate constants and PPCP structures

Metal Binding Agents in Detergents• Dissolved calcium in hard waters precipitates

when the pH is raised during normal laundering operations

• Dissolved calcium and magnesium in hard waters precipitates the cleansing agent in detergents

• Hence, detergents contain chelating agents that bind calcium

• Common chelating agents – polyphosphates, NTA, EDTA, citric acid, succinic acid

Groundwater Contamination

•NAPLs•DNAPLs

Groundwater Remediation

•Pump and treat•Use of surfactants

•In-situ biodegradation/bioremediation•Reductive dehalogenation (zerovalent Feo)•Isolation