Development of a procedure and apparatus to quantify pathogen reduction throughout an

intermittent biosand filter

Duchity, Haiti

Duchity, Haiti – Water Quality

Intermittent biosand filter

Adaptation of a traditional slow sand filter

Designed by Dr. David Manz (1991)

Implemented in more than 70 countries

Appropriate technology

Low cost

Materials availability

Operational simplicity

304 mm

158 mm

543 mm

50 mm

940 mm

222 mm

(5)

(1) Reservoir Zone

(2) Standing water Zone

(3) Biological Zone

(4) Non-Biological Zone

(5) Gravel Zone

50 mm

50 mm

(4)

(3)

(2)

(1)

66 mm

108 mm

(1) CAWST Manual 2009

Biosand filter operation

Biosand filter mechanisms

Mechanical trapping Adsorption

Lack of oxygen

and nutrients Biological Activity

(1) CAWST Manual 2009

Technology comparison

Intermittent biosand filter

Traditional slow sand

filter

Objectives

Evaluate the impact and contribution of microbial activity and

dissolved oxygen concentration in pathogen reduction as

functions of medium depth and time.

Understand the filter mechanisms interaction

Improve filter design

Optimize materials use

Experimental Apparatus

Table 1. Bench scale dimensions

Diameter [m] 0.10

Total height [m] 1.0

Outlet tube

Inside diameter [mm]

Outside diameter [mm]

Tube height [mm]

9.53

6.35

695

Effective volume [mL] 2,280

Media layers

Sand [mm]

Porosity

Separation Gravel [mm]

Porosity

Drainage Gravel [mm]

Porosity

543

0.44

50

0.50

50

0.55

Diffuser

Perforation diameter [mm]

Distance between perforations [mm]

3.2

12.7

Table 2. Haiti local sand

Particle size [mm] 0.7 - 0.1

Effective size [mm] 0.13

Uniformity Coefficient 2.5

Minerals

Quartz SiO2

Calcite CaCO3

Sampling Ports

Table 3. Sampling ports dimensions

Ring diameter [mm] 50

Wall distance [mm] 25.4

Tube

Outside diameter [mm]

Inside diameter [mm]

9.53

6.35

Perforations quantity 5

Mesh

Opening size [μm]

105

307 mm

50 mm

543 mm

50 mm

50 mm

1.0 m 148 mm

335 mm

Methodology

Multi-parameter

PCSTestr 35 Oakton

Results: Tracer test

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

No

rma

lize

d t

rac

er

co

nce

ntr

ati

on

Time [min]

2.54 cm

17.3 cm

33.5 cm 38.5 cm

Results: Tracer Test

MDI = 16

MDI = 7

MDI = 4

MDI = 3

Morrill Dispersion Index

Mixture

Plug Flow

Volumetric flow rate and hydraulic head

y = 101.71e-0.052x

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70

Vo

lum

etr

ic f

low

ra

te [

mL

/min

]

Time [min]

Volumetric flow rate as function of time in a biosand filter

y = 33.143e-0.073x

0

5

10

15

20

25

0 10 20 30 40 50 60 70

Hyd

rau

lic h

ead

[c

m]

Time [min]

Hydraulic head as fuction of time in a biosand filter

y = 4.2028x + 2.7766 R² = 0.9968

0

20

40

60

80

100

120

0.00 5.00 10.00 15.00 20.00 25.00

Vo

lum

etr

ic f

low

ra

te [

mL

/min

]

Hydraulic head [cm]

Volumetric flow rate as function of the hydraulic head in a biosand filter

Volumetric flow rate and hydraulic head

Future Work

Develop concentration profiles

as a function of depth and time

Total coliform

Enterococcus spp.

Dissolved oxygen

Evaluate the impact in the

bacteriological quality of the

biosand filter effluent with a

modified zeolite treatment.

Conduct a person-to-person

survey in Duchity, Haiti.

Table 4. Preliminary Results

Sample Treatment

time

E-coli

CFU/100 mL

Total coliform

CFU/100 mL

Source 0 hr 3,100 66,900

Control 1 hr 3,600 56,500

2 hr 3,400 53,700

Non-modified

zeolite

1 hr 400 13,000

2 hr 100 9,700

Modified

zeolite

1 hr 0 0

2 hr 0 0

Acknowledgements

This material is based upon work supported by the National Science Foundation under Grant No.1033028.

http://greatidea.uprm.edu