Pathogen removal and Pathogen removal and effluent reuseeffluent reuse

Universidade Federal de Universidade Federal de ViçosaViçosa

Departamento de Departamento de Engenharia CivilEngenharia Civil

Rafael K.X. BastosRafael K.X. Bastos

8th IWA SPECIALIST GROUP CONFERENCE ON WASTE STABILIZATION PONDS2nd Latin-American Conference on Waste Stabilization Ponds

Belo Horizonte, Brazil, 26-30 April 2009

• current state of the art current state of the art • knowledge gapsknowledge gaps• future researchfuture research

Pathogens is wastewaterPathogens is wastewater

Organism Concentration

Escherichia coli 106-108 /100 mL

Salmonellae spp. 102-103 /100 mL

Giardia cysts 102-104 / L

Cryptosporidium oocysts 101-102 / L

Helminth eggs 101-103 / L

Viruses 102-105 / L

RotavirusRotavirus

Protozoa (oo)cysts (4 – 20 Protozoa (oo)cysts (4 – 20 μm)μm)

Viruses (nViruses (nm)m)

Helminth eggs ( > 50 Helminth eggs ( > 50 μm )μm )

BacteriaBacteria( ≈ 1 ( ≈ 1 μm )μm )

Pathogens characteristics Pathogens characteristics

Salmonella

GiardiaGiardia

CryptosporidiumCryptosporidium

Ascaris

Pathogens removal in WSP Pathogens removal in WSP

Long HRT Long HRT

Inactivation Inactivation

SedimentationSedimentation

http://www.personal.leeds.ac.uk/~cen6ddm/http://www.personal.leeds.ac.uk/~cen6ddm/

WSP design for pathogens (bacteria) removalWSP design for pathogens (bacteria) removal

.t-Ko

beN=N

.tK+1

N=N

b

o

nb

o

)n

t.K+(1

N=N

.t.d4K1a

ea)(1ea)(1

4ae.NN

b

a/2d2a/2d2

1/2d

o

Dispersed flow

Complete-mix (cells in series )

Complete-mix Complete-mix (one cell)(one cell)

Plug flow

Equation Schematic Hydraulic Regime

Source : von Sperling (2007)

Marais (1974)Marais (1974)First order kinetics First order kinetics

complete-mix reactorscomplete-mix reactorsKKFCFC: temperature dependent: temperature dependent

die-off rate: the same in anaerobic, facultative and maturation pondsdie-off rate: the same in anaerobic, facultative and maturation ponds

Von Sperling (1999), Polprasert & Bhattarai (1985),

Agunwamba et al. (1992) First order kinetics First order kinetics

Dispersed flow rectorsDispersed flow rectors

Dispersion numbers (d)Dispersion numbers (d)

AdvancesAdvances on WSP design for bacteria (faecal coliforms) removal on WSP design for bacteria (faecal coliforms) removal

Curtis & Mara (1994)Environmental factorsEnvironmental factors

Mara (2002)Anaerobic ponds Anaerobic ponds

von Sperling (1999)Pond depth Pond depth

AdvancesAdvances on WSP design for bacteria (faecal coliforms) removal on WSP design for bacteria (faecal coliforms) removal

Influent faecal coliform Influent faecal coliform

TemperatureTemperature

Design flow Design flow

Hydraulic retention time Hydraulic retention time

Die-off rate constant (…)Die-off rate constant (…)

uncertainty of the input design parameters uncertainty of the input design parameters vsvs

deterministic average single valuesdeterministic average single values

random values selected from a range random values selected from a range (uniform probability distribution)(uniform probability distribution)

Monte Carlo Simulation Monte Carlo Simulation random value design procedure repeated for any required number of random value design procedure repeated for any required number of

times.times. design outputs: frequency histogram and cumulative frequency design outputs: frequency histogram and cumulative frequency

curves (decision-making) (e.g.: 95%ile of FC < 1,000 / 100 mL)curves (decision-making) (e.g.: 95%ile of FC < 1,000 / 100 mL)

AdvancesAdvances on WSP design for bacteria (faecal coliforms) removal on WSP design for bacteria (faecal coliforms) removal

AdvancesAdvances on WSP design for bacteria (faecal coliforms) removal on WSP design for bacteria (faecal coliforms) removal

Sensitivity analysis Sensitivity analysis which input design parameters significantly influence the design output which input design parameters significantly influence the design output

von Sperling (1996, 2002)von Sperling (1996, 2002)

one input design one input design parameter is allowed parameter is allowed to vary within a to vary within a proposed rangeproposed range

the rest: single the rest: single average valuesaverage values

AdvancesAdvances on WSP design for bacteria (faecal coliforms) removal on WSP design for bacteria (faecal coliforms) removal

AdvancesAdvances on WSP design for bacteria (faecal coliforms) removal on WSP design for bacteria (faecal coliforms) removal

Gawasiri (2003) Gawasiri (2003)

AdvancesAdvances on WSP design for bacteria (faecal coliforms) removal on WSP design for bacteria (faecal coliforms) removal

Kb (dispersed flow) = - 0.7118 Ln (H) + 0.8589 (20oC) R2 = 0.4491

Kb (dispersed flow) = 0.542 H - 1.259 (1) Von Sperling

Kb (dispersed flow) = 0.917 (H) - 0.877 . (HRT) - 0.329 (2) Von Sperling

Bacteria Bacteria (faecal coliforms(faecal coliforms) removal in WSP) removal in WSP

knowledge gaps & future research knowledge gaps & future research (local contexts)(local contexts)

1,0E+00

1,0E+02

1,0E+04

1,0E+06

1,0E+08

1,0E+00 1,0E+02 1,0E+04 1,0E+06 1,0E+08

Ne

est

(MP

N /

100m

L)

Ne obs (MPN / 100mL)

1,0E+00

1,0E+02

1,0E+04

1,0E+06

1,0E+08

1,0E+00 1,0E+02 1,0E+04 1,0E+06 1,0E+08

Ne

est

(MP

N /

100m

L)

Ne obs (MPN / 100mL)

Observed and estimated values of effluent Observed and estimated values of effluent E.coliE.coli concentrations using concentrations using von Sperling models, equation 1 (left) and equation 2 (right). von Sperling models, equation 1 (left) and equation 2 (right).

Bastos et al (2009) Bastos et al (2009)

Water (half-depth) x air temperatureWater (half-depth) x air temperature

WSP design for bacteria (faecal coliforms) removalWSP design for bacteria (faecal coliforms) removal

knowledge gaps & future research knowledge gaps & future research (local contexts)(local contexts)

Brito (1997) Brito (1997)

Rios (2008)Rios (2008)

Belo Horizonte, Brazil (UFMG)

Viçosa, Brazil (UFV)

Bastos et al (2006) Bastos et al (2006)

Organism

Kb (20oC) (d-1)

Pond 1 Pond 2Pond 3

Samonella sp. 4.57 2.60 3.00

E.coli 2.73 1.41 2.20

Pathogens (bacteria) removal in WSPPathogens (bacteria) removal in WSP

Well designed and properly operated and maintained WSP systems Well designed and properly operated and maintained WSP systems

can achieve a 3-6 log unit removal of bacterial pathogens, and a 3-4 can achieve a 3-6 log unit removal of bacterial pathogens, and a 3-4

log unit removal of viruses (WHO, 2006)log unit removal of viruses (WHO, 2006)

101033 FC / 100 mL effluent quality FC / 100 mL effluent quality ►► absence of pathogenic bacteria absence of pathogenic bacteria

Salmonellae , Campylobacter, Vibrio cholerae, Shigellae… Salmonellae , Campylobacter, Vibrio cholerae, Shigellae… (!!??)(!!??)

Pathogens (bacteria and viruses ) removal in WSPPathogens (bacteria and viruses ) removal in WSP

knowledge gaps & future researchknowledge gaps & future research

Enteroviruses, Norovirus, Rotavirus, Adenovirus, Astrovirus, Enteroviruses, Norovirus, Rotavirus, Adenovirus, Astrovirus,

Hepatitis A virus, Hepatitis E virus, Polyomavirus… Hepatitis A virus, Hepatitis E virus, Polyomavirus… (???)(???)

Viruses Viruses (????)(????)

Oragui et al. (1987, 1993)Oragui et al. (1987, 1993)

WSP design for parasites removalWSP design for parasites removal

Ayres et al (1992)

http://www.personal.leeds.ac.uk/~cen6ddm/ http://www.personal.leeds.ac.uk/~cen6ddm/

y = 5,0498Ln(x) + 88,746

R2 = 0,6847

94

95

96

97

98

99

100

0 2 4 6 8 10

HRT (days)

Eff

cie

ncy

(%

)

Estimated Observed

Ayres et al (1992)

Bastos et al (2006)

Pathogens (parasites ) removal in WSPPathogens (parasites ) removal in WSP

knowledge gaps & future research knowledge gaps & future research (local contexts)(local contexts)

Well designed and properly operated and maintained WSP systems Well designed and properly operated and maintained WSP systems

can achieve a 1-2 log unit removal of protozoan (oo)cysts, and a 3-4 can achieve a 1-2 log unit removal of protozoan (oo)cysts, and a 3-4

log unit removal of helminth eggs (WHO, 2006)log unit removal of helminth eggs (WHO, 2006)

< 1 (human) nematode egg / L effluent quality < 1 (human) nematode egg / L effluent quality ►► absence of other absence of other

settlable organisms [eggs and (oo)cysts] settlable organisms [eggs and (oo)cysts] (??)(??)

Protozoan (oo)cysts (Giardia and Cryptosporidium)Protozoan (oo)cysts (Giardia and Cryptosporidium) (!!??)(!!??)

Grimason et al (1993)Grimason et al (1993)

Microsporidia (Enterocytozoon bieneusi and Encephalitozoon

Intestinalis), Cyclospora cayetanensis, Toxoplasma (…) (??)

Pathogens (parasites ) removal in WSPPathogens (parasites ) removal in WSP

knowledge gaps & future researchknowledge gaps & future research

30

40

50

60

70

80

90

100

3 4 6 8 11TDH (dias)

Efi

ciên

cia

(%)

Ascaris lumbricoides Ascaris sunn Toxocara canis

60

70

80

90

100

3 4 6 8 11TDH (dias)

Efi

ciê

nc

ia (

%)

Cryptosporidium Giardia

Pathogens (parasites ) removal in WSPPathogens (parasites ) removal in WSP

knowledge gaps & future researchknowledge gaps & future research

Ascaris lumbricoides

Ascaris suun

Toxocara canis

Giardia Giardia

CryptosporidiumCryptosporidium

Bevilacqua et al (2008)

WW reuse WW reuse

http://www.personal.leeds.ac.uk/~cen6ddm/ http://www.personal.leeds.ac.uk/~cen6ddm/

Lins - SP

Approaches to setting microbiological guidelinesApproaches to setting microbiological guidelines

(i)(i) The absence of faecal indicator organisms in the wastewaterThe absence of faecal indicator organisms in the wastewater

(ii)(ii) No measurable excess cases in the exposed populationNo measurable excess cases in the exposed population

(iii)(iii) A model-generated risk which is below a defined acceptable riskA model-generated risk which is below a defined acceptable risk

Blumenthal (2000)Blumenthal (2000)

Type of reuse Treatment Effluent quality

Unrestricted irrigation

‘zero risk’ (?)

Secondary + filtration + disinfection

BOD 10 mg/LTurbidity 2 NTU Chorine residual 1mg/L Faecal coliforms ND Pathogens ND

Restricted irrigation

risk (?)

Secondary + disinfection

BOD 30 mg/LChorine residual 1mg/LFaecal coliforms 200/100 mL

Effluent quality for WW reuse Effluent quality for WW reuse

USEPA (2004)USEPA (2004)

Type of reuse Nematode eggs/L FC / 100 mL

Unrestricted irrigation (*) < 1 < 103

Unrestricted irrigation (**) < 1 -

WHO (1989)WHO (1989)

Effluent quality for WW reuse Effluent quality for WW reuse

‘‘Best available’ epidemiological evidenceBest available’ epidemiological evidence

* * workers’ riskworkers’ risk

** ** workers’ and consumers’ riskworkers’ and consumers’ risk

Ponds !!!Ponds !!!

HelminthsHelminths

Bacteria, protozoaBacteria, protozoa

Viruses Viruses

Risk ranking (theoretical model)Risk ranking (theoretical model)

Effluent quality for WW reuse (WHO, 2006) Effluent quality for WW reuse (WHO, 2006)

Options for the reduction of viral, bacterial, and protozoan pathogens Options for the reduction of viral, bacterial, and protozoan pathogens

by different combination of health protection measuresby different combination of health protection measures that achieve that achieve

the the health-based target of 10health-based target of 10-6-6 DALYS pppy DALYS pppy (risk-based approach!!)(risk-based approach!!)

Effluent quality for WW reuse (WHO, 2006) Effluent quality for WW reuse (WHO, 2006)

Pathogens reduced by treatment and post-treatment (pre-ingestion) Pathogens reduced by treatment and post-treatment (pre-ingestion)

health-protection control measureshealth-protection control measures

(i) Method of wastewater application; (ii) die-off between last irrigation (i) Method of wastewater application; (ii) die-off between last irrigation

and consumption; (iii) food preparation (washing/peeling) and consumption; (iii) food preparation (washing/peeling)

Effluent quality for WW reuse (WHO, 2006) Effluent quality for WW reuse (WHO, 2006)

QMRAQMRA

Epidemiological evidence Epidemiological evidence

Effluent quality for WW reuse (WHO, 2006) Effluent quality for WW reuse (WHO, 2006)

viral, bacterial, and protozoan infections: guidelines based on tolerable viral, bacterial, and protozoan infections: guidelines based on tolerable

additional disease burden of additional disease burden of ≤≤1010-6-6 DALYS (disability-adjusted life year) DALYS (disability-adjusted life year)

loss per person per year (pppy)loss per person per year (pppy)

Quantitative microbial risk analysis (QMRA)Quantitative microbial risk analysis (QMRA)

QMRA : QMRA : Dose – responseDose – response + exposure scenarios + exposure scenarios

Hass et al (1999)Hass et al (1999)

Microrisk (2006)Microrisk (2006)

Farmer wades through homemade Farmer wades through homemade diversion canal, which carries diversion canal, which carries wastewater to his fields in Pakistan.wastewater to his fields in Pakistan.

Source: IWMI (2003).Source: IWMI (2003).

Harvesting watercress from a Harvesting watercress from a wastewater canal in Vietnam. wastewater canal in Vietnam. Source: IWMI (2003). Source: IWMI (2003).

labour intensive x highly mechanized agriculture labour intensive x highly mechanized agriculture

QMRA : QMRA : Dose – response + Dose – response + exposure scenariosexposure scenarios

QMRA - Effluent quality for WW reuse (WHO, 2006) QMRA - Effluent quality for WW reuse (WHO, 2006)

exposure scenarios

AdvancesAdvances on QMRA - Effluent quality for WW reuse on QMRA - Effluent quality for WW reuse

http://www.personal.leeds.ac.uk/~cen6ddm/ http://www.personal.leeds.ac.uk/~cen6ddm/

AdvancesAdvances on QMRA - Effluent quality for WW reuse on QMRA - Effluent quality for WW reuse

QMRA - Effluent quality for WW reuseQMRA - Effluent quality for WW reuse

knowledge gaps & future research knowledge gaps & future research (exposure scenarios)(exposure scenarios)

QMRA - Effluent quality for WW reuseQMRA - Effluent quality for WW reuse

knowledge gaps & future research knowledge gaps & future research (exposure scenarios)(exposure scenarios)

QMRA - Effluent quality for WW reuseQMRA - Effluent quality for WW reuse

knowledge gaps & future research knowledge gaps & future research (exposure scenarios)(exposure scenarios)

Constant ratio of pathogen numbers to Constant ratio of pathogen numbers to E. coli E. coli numbers numbers (??) (??)

0.1–1 rotavirus and 0.1–1 rotavirus and CampylobacterCampylobacter per 10 per 1055 E. coliE. coli

0.01–0.1 Cryptosporidium oocyst, per 100.01–0.1 Cryptosporidium oocyst, per 1055 E. coliE. coli

Pathogen die-off (reduction) between harvest and Pathogen die-off (reduction) between harvest and consumption consumption (??)(??)

1010-2-2-10-10-3 -3 rotavirus and rotavirus and CampylobacterCampylobacter

0–0.1 oocyst 0–0.1 oocyst

QMRA - Effluent quality for WW reuseQMRA - Effluent quality for WW reuse

knowledge gaps & future research knowledge gaps & future research (tolerable risk)(tolerable risk)

http://www.personal.leeds.ac.uk/~cen6ddm/

Tolerable risk Tolerable risk (?)(?) ◄►◄► WW effluent quality (treatment level) WW effluent quality (treatment level)

Pathogens removal in WSP - Pathogens removal in WSP - QMRA - Effluent quality for WW reuseQMRA - Effluent quality for WW reuse

knowledge gaps and future researchknowledge gaps and future research (detection methods)(detection methods)

Detection methods for enteric pathogensDetection methods for enteric pathogens

Culture dependent methodsCulture dependent methods Bacteria: viable but nonculturable bacteria (VBNC)Bacteria: viable but nonculturable bacteria (VBNC)

Cell culture monitoring for cytopathogenic effect (CPE), enzyme Cell culture monitoring for cytopathogenic effect (CPE), enzyme

linked immuno assay (ELISA) linked immuno assay (ELISA) ►► some viruses, such as norovirus, some viruses, such as norovirus,

cannot be cultured in vitro.cannot be cultured in vitro.

Detection methods for enteric pathogensDetection methods for enteric pathogens

Microscopy Microscopy

Helminths and Helminths and protozoaprotozoa: concentration,: concentration, immunomagnetic immunomagnetic

separation, fluorescence microscopyseparation, fluorescence microscopy ► ► laborious, expensive and laborious, expensive and

inaccurate.inaccurate.

Fluorescent in situ hybridization Fluorescent in situ hybridization (FISH)(FISH) (bacteria, protozoa) (bacteria, protozoa) ► ►

require expensive equipment and highly trained staff.require expensive equipment and highly trained staff.

S. Enteritidis Oliveira e Bernardo (2002)

Pathogens removal in WSP - Pathogens removal in WSP - QMRA - Effluent quality for WW reuseQMRA - Effluent quality for WW reuse

knowledge gaps and future researchknowledge gaps and future research (detection methods)(detection methods)

Detection methods for enteric pathogensDetection methods for enteric pathogens

Nucleic acid based methodsNucleic acid based methods amplification (Polymerase Chain Reaction) amplification (Polymerase Chain Reaction) (PCR)(PCR) of target DNA or of target DNA or

reverse transcription followed by PCR reverse transcription followed by PCR (RT-PCR)(RT-PCR) for target RNA, for target RNA,

quantitative real time PCR quantitative real time PCR (qPCR),(qPCR), denaturing gradient gel denaturing gradient gel

electrophoresis electrophoresis (DGGE)(DGGE) (viruses, protozoa, bacteria) (viruses, protozoa, bacteria) ► ► require require

expensive equipment, standardization and highly trained staff.expensive equipment, standardization and highly trained staff.

Enteroviruses in pond effluent (Venezuela) Guastadisegni et al (2002)

Pathogens removal in WSP - QMRA - Effluent quality for WW reusePathogens removal in WSP - QMRA - Effluent quality for WW reuse

knowledge gaps and future researchknowledge gaps and future research (detection methods)(detection methods)

Pathogens removal in WSP - Pathogens removal in WSP - QMRA - Effluent quality for WW reuseQMRA - Effluent quality for WW reuse

knowledge gaps and future researchknowledge gaps and future research

Remarkable advances !!Remarkable advances !!

More field data More field data

Thank you !!!Thank you !!!

On-going researchOn-going research

Pathogens removal (mechanisms) in ponds Pathogens removal (mechanisms) in ponds ► ► robust robust

(simple) design models (simple) design models

Pathogens reduction (treatment + post-Pathogens reduction (treatment + post-

treatment) treatment) ► ► QMRA QMRA ◄►◄► epidemiological epidemiological

evidence evidence