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Conjunctive use of urban wastewater with other water source for vegetable
production
S. Raychaudhuri, Mausumi Raychaudhuri, S. K. Rautaray and Ashwani Kumar
Directorate of Water Management(Indian Council of Agricultural Research)
Bhubaneswar, India
Session Wastewater Management – Recycling and Reuse
Fresh water scarcity
Increased demand
Urban wastewater
Pollution
High treatment cost
Climate change
Calls for strong water resource management
Increased volume
Unsafe wastewater irrigation
Appropriate guidelines & management options for safe use
By 2030 India will have 68 cities with > 1 million, 13 cities > 4 million and 6 megacities > 10 million people (A report by McKinsey Global Institute)
38000 mld (million litre daily) of urban wastewater from Class I cities and class II towns out of which only 11787 mld (31%) is treated with a capacity gap of 26467 mld which needs urgent attention.
Class I cities
Urban wastewater - scope
Restriction on WW irrigation through legislation is an unrealistic proposition in view of the socio-economic status of farmers using it (72000 ha)
Instead, wastewater management protocols and techniques should be developed based on sound scientific knowledge to support farmers.
Joypurpatna (20.20 N, 85.83E)
Industrial & domestic discharge (88 industries and 2 clusters (34 pollution potential industries)
overflow of the septic tanks and oxidation ponds.
Open drains join to form Gangua nala
A large area (> 5000 ha) is irrigated with Gangua
Gangua irrigated soils were higher in Mn (40%), Fe (3%), Zn (85%) , Cd (20%) and Pd (0%).
Heavy metal concentrations in none of the samples exceeded the critical limits of Zn, Pb and Cd. The critical limits of Zn, Cd and Pb are 460, 3 and 300 ppm respectively
Higher respiration
Higher respiration and MBC in waste water irrigated soils indicated better soil health ! Higher significant correlation between OC x MBC (0.982), OC x Resp C (0.869) in comparison to those in OS irrigated soils the increased OM in GI soils due to organic pollutants were conducive for better microbial activities
Higher respiration
Higher MBC
Metal enrichment within limts (except Cd)
Higher nutrients
Long term impact
Concentrations in plants Fe > Mn < > Zn > Cd > Cr > Cu
Higher productivity of paddy and vegetables
Transfer factors of metals in vegetables
Experimental•Field experiment infarmers’ field in 2010 and 2011 at village
Joypurpatna with four vegetables viz. okra, bitter gourd, cucumber and ridge gourd.
•Plot size 100 m2 and 7 adjacent farmer’s fields as replicates in RBD. •Treatments T1: River, T2: WW and T3: River + wastewater (1:1).
Irrigatn pH EC SAR TN P K Fe Mn Zn Cr Cd Pb
Gangua6.70a**(+ 0.21)
0.48a*(+ 0.14)
4.3a**
(+ 1.6)
26a**(+ 4.6)
2.8a*(+ 0.72)
10.3a** ( + 4.1)
1.24a* (+ 0.421)
0.32a** (+ 0.061)
0.11a**(+ 0.032)
0.086a* (+
0.042)
0.014a*(+ 0.008)
1.13a** (+ 0.16)
River8.44b*
(+ 0.42)0.24b**(+ 0.11)
2.9b** (+ 0.34)
14b** (+ 3.2)
0.52b* (+ 0.29)
2.7b**(+ 1.3)
0.546b** (+ 0.123)
0.044b** (+ 0.022)
0.062(+ 0.041)
0.063b* (+ .034)
0.010b*( + 0.006)
1.02a** (+ 0.19)
Ref 6.5 – 8.5 SM SM SM 5.0 0.2 2.0 0.1 0.01 5.0
Soil chemical properties under different treatments. Soil Parameters Initial Daya Gangua D + GpH (1:2.5) 5.75 + 0.16 5.95 + 0.13 5.82 + 0.19 5.83 + 0.21EC (µS cm-1) 80 + 13 85 + 15 96 + 19 88 + 21OC (g kg-1) 5.61 + 0.35 5.60 + 0.43 5.64 + 0.41 5.62 + 0.34TN (%) 0.21 + 0.02 0.21 + 0.03 0.22 + 0.02 0.21 + 0.02Av N (kg ha-1) 281 + 28 302 + 34 316 + 35 310 + 42P2O5 (kg ha-1) 48 + 13 49 + 16 42 + 18 43 + 21K2O (kg ha-1) 182 + 18 188 + 21 193 + 25 191 + 19Na (mg kg-1) 30 + 9 33 + 11 38 + 16 35 + 14
Yield advantage was there
Increasing trend for the yield and yield attributes
The yield advantage ranged from 9% (13.1 t/ha) for bitter gourd to 15% (9.2 t/ha) with cucumber.
When the crops were irrigated with 1:1, yield advantage ranged from 3% with okra to 11% with ridge gourd
Trace metals in soils
Accumulations are less in fruits and more in leaf
Cd - concern ?
Conclusion
At least 50% fresh water can be saved
For safe use appropriate crop selection is required
Leafy vegetables are risky for ww irrigation
Cd is a concern which may be addressed through addition of ameliorative agents
Urban wastewater is resource for increase vegetable productivity
Reclamation within agricultural system
Conclusion