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