IMPACT OF RECYCLED WATER USE COMPARED TO TOWN WATER IN URBAN IRRIGATION: A LONG-

TERM COLUMN STUDY

Muhammad Muhitur RahmanDharma Hagare

Basant Maheshwari

by

Peri-Urban 2014

July 8, 2014

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Outline

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The Problem: Salt accumulation in open spaces

Photo credit: Donald Suarez, US Salinity laboratory

1. Increased level of salinity

in the root zone may

Affect plant response in

terms of leaf xylem water

potential, tissue moisture

content and color of grass

in open space

Reduces the root water

uptake by plants, which

reduces plant growth and

hence, reduces crop yield.

2. Impact on ground water

table

Why Recycled water is an issue in this Research?

4

Parameter Unit

Recycled water Characteristics

(General)

Recycled water Characteristics (Australian)

Drinking water

standard(Australian)

EC dS/m 0.51-2.7Avg. 1.53

0.2-2.9Avg. 1.3

0.1

TDS mg/l 358-1800Avg. 1054

145-1224Avg. 675

<500

pH 7.06-9.6Avg. 8.12

6.2-9.8Avg. 7.9

6.5-8.5

Na+ mg/l 84.9-350Avg. 173.64

62-312Avg. 181

180

Cl- mg/l 43.9-564.4Avg. 284.70

9.3-340Avg. 135

250

Source: Bakopoulou et al., 2011, Smith et al., 1996, Kang et al., 2007, Adrover et al., 2010, Tarchouna et al., 2010, Aiello et al., 2007, Gonçalves et al., 2007, NWQMS, 2011

Impact of long term Irrigation with Recycled water

5

Years of Irrigation

Impact on SoilReference

3 yrs Soil salinity increased from 105.1 μS/cm to 235 μS/cm (123% increase)

Dikinya and Areola (2010)

5 yrs Soil salinity increased from 2.3 μS/cm to 4.5 μS/cm (95% increase)

Jahantigh (2008)

14 yrs Soil salinity increased from 0.16 μS/cm to 1.12 μS/cm (600% increase)

Klay et al. (2010)

20 yrs Soil salinity increased from 51.6 μS/cm to 122.7 μS/cm (138% increase)

Xu et al. (2010)

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Recycled water irrigation in the Hawkesbury Water Reuse Scheme, Australia (HWRS)

66

Years of Irrigation

60 years

Location University of Western Sydney (Hawkesbury campus), Australia

Source of recycled water

Sydney Water’s Richmond sewage treatment plant

Studies conducted on

Health-risk assessment and risk communication toolkit

Regrowth of faecal indicator in the on-site storage dam

Statistical analysis of water demand for irrigation Changes in soil properties due to recycled water

irrigation

This study Behaviour of salt accumulation in two paddocks, i.e. D21 paddock and C5 paddock.

Objective of this study

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To study the salt accumulation in columns packed with silty loam (D33

paddock) and loamy sand (Yarramundi paddock) soil

Conventional salt mass balance for entire soil profile

Sensor measured salinity (ECbulk) at 0.2m depth

Spatial variation of salt accumulation for both types of soil columns

Recycled and town water as irrigation water

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Parameter D33 Yarramundi

% sand 45.6 86.6

% silt 29.5 9

% Clay 24.9 4.4

Texture Silty loamLoamy sand

Packing Bulk Density (kg/m3)

1,500 1,500

EC 1:5 (uS/cm) 63 27

EC (sat. Extract), ECe (uS/cm)

824 281

Schematic of column setup

Laboratory soil column setup

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The experiment was conducted for a period of 330 days.

Recycled water (EC=0.83 dS/m) was collected from a storage dam in the

HWRS

Town water (EC=0.21) was collected at the laboratory

Irrigation (recycled and town) water was applied at the same frequency as in

practice

Leached water volume was measured and it was analysed for electrical

conductivity by an EC meter (HACH Inc.)

Sensor measured Ecbulk at 0.2m depth at minute interval

At the end of the study, soil profile was analysed for each 5 cm interval to

establish spatial variation of salt accumulation.

Experimental procedure

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Irrigation scheduling and Meteorological condition

Irrigation water added:

3 times/week

15.9 to 26.5 mm per week

Parameter Range

Tmax (0C) 19.6-24.9Tmin (0C) 18-23.0RH (%) 33-77

Wind (km/d) 0-20.2

No rainfall was

considered

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Salt mass balance as an indicator of salt accumulation in the D33 soil columns

Leached salt load

For town water irrigation

varied with a standard

deviation of 0.08 to 4.8 g/m2

For recycled water the

standard deviation was 0.97

to 9.4 g/m2 From day 2 causing negative

cumulative stored salt mass

till 134 days.

From day 135, a positive salt

accumulation occurred and

continued throughout the

study period.

On average, 5.4 times more salt

accumulated due to recycled water

irrigation compared to town water

irrigation

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Salt mass balance as an indicator of salt accumulation in the Yarramundi soil column

Leached salt load

For town water irrigation

varied with a standard

deviation of 0.13 to 5.9 g/m2

For recycled water the

standard deviation was 0.79

to 4.1 g/m2 From day 2 causing negative

cumulative stored salt mass

till 75 days.

From day 76, a positive salt

accumulation occurred and

continued throughout the

study period.

On average, 3.8 times more salt

accumulated due to recycled water

irrigation compared to town water

irrigation

Sensor measured Bulk electrical conductivity at 0.2m depth

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Top view of sensor position

160 mm

GS3 Sensor

Data Logger

Sensor measured Bulk electrical conductivity at 0.2m depth

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ECbulk on the day of 330

For both types of soil

recycled water

irrigation showed

more salt

accumulation than the

tap water irrigation.

On average, recycled

water irrigation

caused 2.2 and 1.6

times more salinity

for D33 and

Yarramundi soil.

Spatial variation of salt accumulation (in terms of EC1:5) in D33 soil columns

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Recycled water application

caused increased

accumulation of salt by

about 2.5 times in the soil of

upper portion of the column

(0-0.2m) compared to town

water application.

Soil samples collected from

lower portion of soil column

(0.20-0.30 m) showed

relative salt accumulation by

about 2.1 times.

Spatial variation of salt accumulation (in terms of EC1:5) in Yarramundi soil columns

1616

Recycled water application

caused increased

accumulation of salt by

about 1.9 times in the soil of

upper portion of the column

(0-0.2m) compared to town

water application.

Soil samples collected from

lower portion of soil column

(0.20-0.30 m) showed

relative salt accumulation by

about 2.3 times.

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Results of a column study using recycled water compared to town water is shown for

silty loam and loamy sand soil;

For both types of soil, recycled water irrigation caused more salt accumulation than

town water irrigation

Salt mass balance shows

For silty loam, recycled water irrigation caused 5.4 times more accumulation

than the town water irrigation.

For loamy sand soil, 3.8 times more salt stored due to recycled water irrigation

compared to town water irrigation

Conclusions

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Salinity in terms of EC1:5 shows

For silty loam soil, 2.5 times more salt accumulation due to recycled water

irrigation between the depth of zero and 0.2m

For loamy sand soil, 1.9 times more salt accumulated in the upper part of the

soil profile

On the whole, salinisation is more likely to occur in D33 paddock compared to

Yarramundi paddock under a continuous recycled water irrigation scheme.

Conclusions

Thank You

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