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EXTENSIVE AND NATURAL SYSTEMS FOR WASTEWATER TREATMENT

Marcos von Sperling

Federal University of Minas GeraisBrazil

10th Specialized Conference on Small Water and Wastewater Treatment Systems

Venice, 18-22 April 2011

EXTENSIVE AND NATURAL SYSTEMS FOR WASTEWATER TREATMENT

• Cover only wastewater treatment

• Reflect more the experience at warm-climate regions, particularly Brazil

• Express some personal opinions

• Photos: not only small systems

PRESENTATION OUTLINE• Stabilization ponds

• Constructed wetlands

• UASB reactors + post-treatment

FEDERAL UNIVERSITY OF MINAS GERAIS - BRAZILCentre for Research and Training in Sanitation

UFMG - COPASA

IWA SPECIALIST GROUPS WITH GREATER INTERFACE WITH EXTENSIVE AND NATURAL SYSTEMS

• Anaerobic digestion

• Resources Oriented Sanitation (EcoSan)

• Sanitation and Water Management in Developing Countries

• Small Water and Wastewater Systems

• Use of Macrophytes in Water Pollution Control

• Waste Stabilisation Ponds

WASTE STABILIZATION PONDS

IWA Specialist Group on Waste Stabilization Ponds

8 international conferences(next one: Adelaide, Australia, 1-4 August 2011)

IWA Specialist Group on Waste Stabilization Ponds

Books published by IWA on stabilization ponds

FacultativeSTABILIZATION PONDS

Brazil

Anaerobic pond – Facultative pondSTABILIZATION PONDS

Brazil

South of France – Aerators on during wine production periods

Aerated lagoonSTABILIZATION PONDS

Northeast Brazil - 1 Anaer. pond + 1 Facult. pond + 3 Matur. ponds (100 ha)

Anaerobic – facultative - maturation pondsSTABILIZATION PONDS

UASB – POLISHING PONDS

Experimental WWTP UFMG/COPASA - 250 inhab

REMOVAL OF ORGANIC MATTER

FACULTATIVE PONDS

FACULTATIVE PONDSDesign criteria

• Surface organic loading rate• Depth • Hydraulic retention time• Geometry (length / breadth ratio)

Mara: Ls = 350 x (1.107 – 0.002.T) (T-25)

(T = mean air temperature in coldest month)

Surface organic loading rate - Ls

FACULTATIVE PONDSDesign criteria

Surface loading rate as a function of temperature

0

100

200

300

400

T (oC)

Ls (k

gBO

D/ha

.d)

Ls 100 124 152 183 217 253 291 331 350 350 350

10 12 14 16 18 20 22 24 26 28 30

FACULTATIVE PONDSEffluent BOD

Total BOD = Soluble BOD + Particulate BOD

FACULTATIVE PONDSHydraulic models

Plug flow Completely mixed

Cells in series Dispersed flow

-K.t0eS=S

K.t+1S

=S 0

n0

)ntK+(1

S=S

4K.t.d1a

ea)(1ea)(1

4ae.SSa/2d2a/2d2

1/2d0

+=

−−+=

−

FACULTATIVE PONDSEffluent soluble BOD concentration

Completely mixed:

• Primary ponds: K = 0.30 to 0.40 d-1

• Secondary ponds: K = 0.25 to 0.32 d-1

FACULTATIVE PONDSHydraulic models

Relationship between reaction coefficients (K)

FACULTATIVE PONDSHydraulic models

CFD modelling

5 10 15 20 25 30 35 40 45 50 55

5

10

15

20

25

(e.g. studies on the influence of baffles)

Tracer studies

(long time for field trials)

1 mgSS/L = 0.3 to 0.4 mgBOD5/L

Pond effluents: 60 to 100 mgSS/L (for design)

1 mgSS/L = 1.0 to 2.0 mgCOD/L

FACULTATIVE PONDSEffluent particulate BOD concentration

No adequate models for predicting effluent BOD and SS

FACULTATIVE PONDSEffluent polishing (algae removal)

Coarse rock filter:Experiments UFMG:Stones: 3 to 8 cmH = 0.40 mHLR: 0.5 to 1.5 m3/m3.d

Floating macrophytes – duckweed (Lemna)

Experimental WWTP UFMG/Copasa

FACULTATIVE PONDSEffluent polishing (algae removal)

PRIMARY FACULTATIVE PONDSSand accumulation

Brazil

Prior grit removal is recommended

Colombia

FACULTATIVE PONDSSludge accumulation

0.03 to 0.08 m3/inhab.year

2 to 3 cm per year

FACULTATIVE PONDSSludge accumulation

Operation for 20 years without need of sludge removal

Complex operation when removal is necessary

REMOVAL OF PATHOGENIC ORGANISMS IN PONDS

REMOVAL OF PATHOGENIC ORGANISMS

Removal of bacteria and viruses

Die-off mechanisms (high UV radiation, high pH, high DO, ...)

Substantial research in the past years

(source: Nelson, 2009)

REMOVAL OF PATHOGENIC ORGANISMSRemoval of bacteria and viruses

Molecular biology methods (PCR, FISH, Quantitative PCR)

Detection of actual pathogenic organisms, not only indicators

(source: Godinho et al 2009)

b c

RSRS P1RS P1RS

a

PCR products from amplification of DNA from: a) Escherichia coli, b) Salmonella enterica subsp. enterica,c) Enterococcus spp., d) Shigella dysenteriae.Legend: RS (raw sewage), UASB (UASB effluent), P1 (polishing pond 1 effluent)

Coliform removal efficiency (log units)186 ponds around the world

FACULTATIVE AND MATURATION PONDS

LOG UNITS REMOVED IN EACH POND OF THE SERIES

Median 25%-75% 5%-95%

PRIM SEC MAT1 MAT2 MAT345

CATEGORY

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

LOG

UN

ITS

RE

MO

VE

D

MATURATION PONDS

Baffled ponds

Samambaia, Brazil (180,000 inhab)

MATURATION PONDS

Ponds in series

Experimental WWTP UFMG/Copasa (250 inhabitants)

MaxMin75%25%Median

EFFLUENT E. COLI CONCENTRATIONSPHASE 1

E. c

oli (

MPN

/100

ml)

1

10

100

1000

10000

1e5

1e6

1e7

1e8

1e9

1e10

RAW UASB POND1 POND2 POND3 POND4

Depth of ponds: H: 0.4 to 0.8 m (shallow ponds)

Coliform die-off coefficient (Kb) - dispersed flow186 ponds around the world

FACULTATIVE AND MATURATION PONDS

Kb disp (20o C) vs depth H

0,0

1,0

2,0

3,0

4,0

5,0

6,0

0,00 1,00 2,00 3,00H (m)

Kb (1

/d)

Effluent coli estimated x observed

1,E+00

1,E+02

1,E+04

1,E+06

1,E+08

1,E+10

1,E+00 1,E+02 1,E+04 1,E+06 1,E+08 1,E+10

Obs

Estim

FACULTATIVE AND MATURATION PONDS

For the same surface area A:

Increase H increase V increase HRT

But Kb decreases Efficiency does not increase

H

2H

A A

V

V

REMOVAL OF PATHOGENIC ORGANISMS

Removal of protozoan cysts and helminth eggs

Mechanism: sedimentation

Helminth eggs removalAyres et al model (2002)

] 0,14.e [1 . 100E 0,38.t)(−−=Mean removal efficiency:

WHO (irrigation):< 1 egg/L

FACULTATIVE AND MATURATION PONDS

REMOVAL EFFICIENCY OF HELMINTH EGGS

0,0

1,0

2,0

3,0

4,0

5,0

6,0

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Hydraulic detention time(d)

Log

units

rem

oved

Average values95% confidence level

Helminth eggs removalAyres et al model (2002)

FACULTATIVE AND MATURATION PONDS

HELMINTH EGGS - FIRST PONDESTIMATED (AYRES) AND OBSERVED EFFICIENCY

80

85

90

95

100

0 5 10 15 20 25RETENTION TIME (d)

EFFI

CIE

NC

Y (%

OBS

ESTIM

Average values from five different ponds in Brazil

Helminth eggs removal

Baffled maturation pond in Brazil (4 baffles)Helminth eggs in the sludge after two years

FACULTATIVE AND MATURATION PONDS

Avoid population access!

STABILIZATION PONDS

NITROGEN REMOVAL

FACULTATIVE AND MATURATION PONDSNitrogen removal

NITROGEN REMOVAL EFFICIENCY

0

20

40

60

80

0 5 10 15 20 25 30 35 40

HDT (d)

Effic

ienc

y (%

)

pH=7,0

pH=7,5

pH=8,0

pH=8,5pH=9,0

T= 20oC

• Values from one of the equations available in the literature• Assumption that NH3 volatilization is the prevailing mechanism• Considerable debate over the mechanisms• Removal efficiencies are not high

FACULTATIVE AND MATURATION PONDSNitrogen removal

• Capture of ammonia escaped through the surface of a pond, in order to measure volatilization rate• Studies with marked nitrogen isotopes (15N)

Volatilization does not seem to be a major mechanism

Experimental WWTP UFMG, Brazil Experimental WWTP UK (Miller et al, 2009)

MATURATION PONDSNitrogen removal

Experimental WWTP UFMG-Copasa

• N fraction removed: ammonia• Poor nitrification

NITROGEN FRACTIONS

MATURATION PONDS x WETLANDSAmmonia removal

H

1.0m0.5m

Experiments from Univ. São Paulo, Brazil(two ponds in parallel):

For the same surface area A:

Greater H Higher V Higher HRT

Lower ammonia removal efficiency

Pond with H=0.5m (L/B = 16)

PONDS: FUTURE CHALLENGES

PONDS: FUTURE CHALLENGES

• Reduction of required area

• Better understanding of the removal mechanisms(e.g. pathogen decay; nitrogen removal)

• Implementation of rational models design optimization (but not much scope for operationalcontrol)

• Carbon sequestration and energy production(biodiesel, hydrogen production from cyanobacteria...)

• ...

CONSTRUCTED WETLANDS

IWA Specialist Group on Use of Macrophytes in Water Pollution Control

12 international conferences

Next conference: Perth, Australia - 2012

IWA Specialist Group Use of Macrophytes in Water Pollution Control

Books published by IWA on constructed wetlands

Constructed Wetlands for Pollution Control

Processes, Performance, Design and Operation

Author(s): R. Kadlec, R. Knight, J. Vymazal, H.

Brix, P. Cooper, R. Haberl

Publication Date: 2000

New Zealand (pond effluent polishing)

Surface flow constructed wetlands

Experimental WWTP UFMG / COPASA (50 inhab each unit)

Planted(Typha)

Unplanted

Horizontal subsurface-flow constructed wetlands

Surface hydraulic loading: 0.1 m3/m2.d

Hydraulic retention time (V.porosity/Q): 1.2 d

Measured filtered COD concentrations along the length

020406080

100120140

0% 25% 50% 75% 100%

CO

D c

once

ntra

tion

(mg/

L)

Planted wetland

25%

50%

90%

10%

Min

Max

75%

Relative distance

020406080

100120140

0% 25% 50% 75% 100%

CO

D c

once

ntra

tion

(mg/

L)

Unplanted wetland

25%

50%

90%

10%

Min

Max

75%

Relative distance

Horizontal subsurface-flow constructed wetlands

• Water losses (evapotranspiration): increase in effluent concentrations

• Compute removal efficiencies in terms of loads (and not concentrations)

• Actual role of plants? (debate in the literature)

• Capacity for N and P removal?

Clogging surface flow

Horizontal subsurface-flow constructed wetlands

• Modelling of clogging development and hydraulic conductivity reduction• Refurbishment / cleaning of the beds

Source: Knowles et al (2010)

Experimental WWTP UFMG-Copasa

Vertical flow constructed wetlands

Experimental WWTP UFMG / COPASA (100 inhab)

French (CEMAGREF) system

Tifton

Vertical flow constructed wetlands

Experimental WWTP UFMG / COPASA (100 inhab)

Hydraulic behaviour

0,0000

0,0005

0,0010

0,0015

0,0020

0,0025

0,0030

0,0035

0,0040

0,0045

0 200 400 600 800 1000 1200E

(t)

Initial tests (clean filter)

After a 11 months operation (used filter)

Time(min)

Tracer studies - DTD curve

0

20

40

60

80

100

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40

Tempo (horas)

Q (L

itros

/min

uto)

Teste 5 (FV-NP) Teste 11 (FVP-2)

Outflow as a function of time

Vertical flow constructed wetlands

Experimental WWTP UFMG / COPASA (100 inhab)

Potential for nitrification

0

5

10

15

20

25

30

Raw Unplanted Planted

Nitr

ogen

fract

ions

(mg/

L) N nitrate

N ammonia

N organic

UASB REACTORS AND POST-TREATMENT OF ANAEROBIC

EFFLUENTS

SMALL UASB REACTORS

Experimental WWTP UFMG / COPASA (250 inhab)

UASB REACTORFrom small to large installations

Hundreds of inhabitants One million inhabitants

Experimental WWTP UFMG / COPASA Onça WWTP – COPASA (Brazil)

UASB + POST-TREATMENT

Any of the technologies for treating raw sewage can be used as post treatment with advantages (in warm climate regions)

Advantages:

• Certain reduction in construction costs• lower volume/area of the units

• Large reduction in operating costs• less energy consumption• less quantity of sludge to be produced

Polishing ponds

Lagoa depolimento

ReatorUASB

WWTP UFMG – Copasa (250 inhab)

UASB + POST-TREATMENT

UASB

Pond

Overland flow

Overland flowUASB + POST-TREATMENT

Itabira, Brazil(300 inhab)

Loading rate: 0.2 to 0.5 m3/h per meter widthLength: 30 to 45 mSlope: 2 to 8%

Experimental WWTP UFMG / COPASA (50 inhab each unit)

Planted

Unplanted

Horizontal subsurface-flow constructed wetlandsUASB + POST-TREATMENT

Activated sludgeUASB + POST-TREATMENT

Rio Claro, Brazil - 100,000 inhab

Trickling filterUASB + POST-TREATMENT

Itabira, Brazil - 70,000 inhab

Trickling filterUASB + POST-TREATMENT

Experimental WWTP UFMG / COPASA (500 inhab)

Trickling filterUASB + POST-TREATMENT

Experimental WWTP UFMG / COPASA (UASB: 500-700 inhab; TF: 300 inhab)

CONCLUDING REMARKS

There is no overall best treatment process

In each particular case, select the system with the bestperformance from the technical and economical studies

THANK YOU VERY MUCH!

ENJOY THE CONFERENCE!