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)
5
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
88
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
99
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
1111
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
1212
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
1313
Top view of sensor position
160 mm
GS3 Sensor
Data Logger
Sensor measured Bulk electrical conductivity at 0.2m depth
1414
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
1515
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.
1717
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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