Waste ferric sludge wetland

substrates for tertiary treatment

of recalcitrant substances in

wastewater

Devin Sapsford and Akintunde Babatunde,

Cardiff School of Engineering, Cardiff University

Constructed Wetalnds Established use of constructed wetalnds for removal of N

species, P – species and BOD etc

Do they have a role in treating ‘emerging contaminants’ and

other recalcitrant contaminants?

Why ‘emerging’ contaminants?

‘Emerging’ determined by whether the contaminant is persistent or has potentially harmful human or ecological effects

Perfluorooctanoic acid (PFOA), perfluorooctanesulfonate (PFOS), and other

perfluorinated compounds

Pharmaceuticals, Hormones, and Endocrine Disrupting Compounds (EDC)

Drinking Water Disinfection Byproducts

Sunscreens/UV Filters

Brominated Flame Retardants

Benzotriazoles

Dioxane

Naphthenic Acids

Pesticide Degradation Products and New Pesticides

Perchlorate

Gasoline Additives: MTBE and EDB

Algal

Naphthenic acids

PharmaceuticalsPharmaceuticals, hormones, and EDCs are present in water due to incomplete removal during wastewater treatment.

Possible estrogenic and other effects, both to wildlife and humans.

Bacterial resistance from overuse and release of antibiotics into the environment.

Pharmaceuticals are introduced via use by

humans and in vetenary care and farming

(Source: Richardson, 2007, Anal. Chem. 79, 4295-4324)

Removal mechanisms for

wastewater treatment Sorption (e.g. GAC),

Biodegradation, dilution, and volatilization

Reductive or oxidative attack

Direct photolysis

Advanced Oxidation Processes

Heterogeneous photocatalysis employing semiconductor

catalysts (TiO2, ZnO, Fe2O3, CdS, GaP and ZnS) or Fenton’s or Photofenton’s processes

Previous work on use of

constructed wetlands for treatment

of pharmaceuticals

Caffiene, salicyclic

acid > Ibuprofen,

naproxen

Identified mechanisms for removal

of pharmaceuticals in wetlands

Complex systems – difficult to identify mechanisms

Sorption and hydrophobically driven interactions with organic

matter, some biodegredation

Reactive Media in Constructed

Wetlands (for enhanced P removal)

Alum sludges

Zhao, Y. Q., X. H. Zhao, and A. O. Babatunde. "Use of dewatered alum sludge as main substrate in treatment reed bed receiving agricultural wastewater: Long-term trial." Bioresource technology 100.2 (2009): 644-648.

Iron sludges

Heal, K. V., et al. "Enhancing phosphorus removal in constructed wetlands with ochre from mine drainage treatment." Water Science and Technology 51.9 (2005): 275-282.

Hydrous Ferric Oxide Sludges

From water treatment works (from groundwater or from added

coagulants), or from coal mine drainage. Generally XRD-

amorphous/ferrihydrite. Iron not toxic in this form.

Thickened sludge

Air-dried sludge

Liquid sludge

Samples of water treatment sludges

Elemental compositionChemicalComposition

Unit Pontsticill(Alum)

StrataFlorida(Alum)

Court Farm

(Ferric)

BontGoch

(Ferric)Aluminium as Al203

mg/g 236 225 93.0 13.7

Iron as Fe203 mg/g 11.0 19.5 244 381

Calcium as Ca0 mg/g 4.0 0.8 16.9 8.6Magnesium as Mg0

mg/g 2.1 0.3 15.6 0.7

Humic Acid as TOC

mg/g 230.6 nd 80.2 nd

Cl- mg/l 39.3 2.0 4.9 1.3S04

2 mg/l 59.9 2.0 65.2 4.34H2 O at 105oC % 84.8 86.0 79.7 81.6

Sludge Compositions

Ad

so

rptio

n c

ap

acity (

mg

-P/g

)

P capacities (v pH)

HFO also is an excellent sorbent for heavy metals such as Zn, Cu,Pb at

circumneutral pH

Why use HFO as a reactive media

in constructed wetlands?

Re-use of a common waste sludge but also possess several

useful properties...

Removal Mechanisms for

recalcitrant pollutants:

1. ‘Trapping’ with HFO

R1

R2

R3

1

2 3 45

6

Image taken from google Earth

20m

PAH Compound Sample L1-1 (mg/kg) Sample L1-2 (mg/kg) Sample L1-3 (mg/kg)

Naphthalene 953.5 10.72 0.866

Acenaphthylene 355.9 31.10 n.d.

Acenaphthene 199.8 26.18 n.d.

Fluorene 871.8 146.6 0.720

Phenanthrene 1460 354.6 7.738

Anthracene 403.6 n.d. 3.366

Fluoranthene 518.1 122.1 23.40

Pyrene 280.6 66.21 14.06

Benz(a)anthracene 156.8 37.02 8.833

Chrysene 146.3 29.95 7.425

Benzo(k)flouranthene 30.72 5.972 0.926

Benzo(a)pyrene 97.15 18.42 4.667

Indeno (1,2,3-cd) pyrene 32.15 4.880 0.006

Benzo(g,h,i)perylene 27.35 5.280 n.d.

TOTAL 5534 859.0 72.00

TPH Compound Sample L1-1

(mg/kg)

Sample L1-2

(mg/kg)

Sample L1-3

(mg/kg)

Sample L1-4

(mg/kg)

Dodecane 23.76 n.d. n.d. n.d.

Tetradecane 13.19 1.757 n.d. n.d.

Octadecane 1486 345.0 7.989 2.201

Docosane 5.278 n.d. n.d. n.d.

Tetracosane 20.15 n.d. n.d. n.d.

Hexacosane 3.541 n.d. n.d. n.d.

TOTAL 1552 346.8 7.989 2.201

Removal Mechanisms for

recalcitrant pollutants:

2. Photocatalytic Oxidation It is a well known fact that many metallic oxides exhibit photo

catalytic properties due to their semiconductor properties

Mechanism of a photocatalyst

(Bahnemann. D. W. 2004)

Fe2O3 + hv hVB+ + eCB

-

hVB+ + H2O OH*

eCB- + O2 O2*

- + H2O OH*

Pharamaceutical process effluent,

phenol (0.1% w/w) and Mn tested

Component

Component percentage

(%)

Piperazine 8.7

N-methyl-2-pyrrolidone 4.3

Quetiapine chloroimine 1.7

Toluene 0.8

Aryl piperazine 0.2

Samples in the environmental chamber

underwent extreme irradiation from a full

spectrum of light with an equivalent intensity

approximately to that of midday sun around

the equator, this equates to approximately

900W/m2.

Absorption spectrum for iron oxides is below

600nm, so there is potential for a large

amount of photo activity in the presence of

iron.

-1.00E+00

0.00E+00

1.00E+00

2.00E+00

3.00E+00

4.00E+00

5.00E+00

6.00E+00

280 320 360 400 440 480 520 560 600 640 680 720 760 800

Irra

dia

nce (

W/m

²)

Wavelength (nm)

Pre Test

% Decrease in measured COD (or

concentration for Mn) with 24 hrs

RTContaminant 5g/L HFO 10 g/L HFO 5g/L HFO

+ daylight

10 g/L HFO

+ daylight

25% v/v

solution of

pharmaceutic

al wastwater

0% 3% 53% 68%

0.1% Phenol 16% 19% 69% 44%

100 mg/L Mn 75% 76% 95% 99%

Holder, N. 2011Performed similar to the addition of H2O2 to mix

and some cases better

Removal Mechanisms for

recalcitrant pollutants:

3. (Bio)geochemical reduction by

Fe(II)-HFO

The redox intensive cycling

in wetalnd conducive to

regeneration of surface

bound Fe(II)

Key Questions Are wetlands compatible with iron sludges?

Is the iron non-toxic?

Will dissolved iron be released?

Rates and specificity of breakdown

Summary There seems substantial opportunity to use WASTE hydrous

ferric oxides from water treatment and mine water treatment as reactive media for constructive wetalnds for enhanced removal of conventional contaminants of concern such as P and heavy metals but also for a range of ‘emerging’ recalcitrant pollutants.

Number of mechanisms to utilise including photocatalysed oxidation and biogeochemical reduction with sorbed Fe(II)

Further research in this area is now underway.

Thank you

Dr Devin Sapsford,

Dr Akintunde Babatunde,

Cardiff School of Engineering, Cardiff University

sapsfordDJ@cf.ac.uk