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Session Wastewater Management – Recycling and Reuse

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


Fresh water scarcity

Calls for strong water resource management

Increased demand Climate change

Urban wastewater

Pollution

High treatment cost

Increased volume

Unsafe wastewater irrigation Appropriate guidelines & management options for safe use

Class I cities

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.


Restriction on WW irrigation

through legislation is an socio-economic status of farmers using it (72000 ha)

unrealistic proposition

in view of the

Instead, wastewater management protocols and techniques should be developed based on sound scientific knowledge to support farmers.

Urban wastewater - scope


Industrial & domestic discharge (88 industries and 2 clusters (34 pollution potential industries)

overflow of the septic tanks and oxidation ponds. 3 8 . 5 , 8 Open drains join to form Gangua nala N 0 E)

y Jo

pu

a rp

tn

20 a(

.2

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


Long term impact Higher respiration Metal enrichment within limts (except Cd)

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 nutrients

Higher MBC


Transfer factors of metals in vegetables

Concentrations in plants Fe > Mn < > Zn > Cd > Cr > Cu

Higher productivity of paddy and 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

0.014 * 1.13a** (+ 0.008) (+ 0.16) a

Soil chemical properties under different treatments. Soil Parameters Initial Daya Gangua D+G pH (1:2.5) 5.75 + 0.16 5.95 + 0.13 5.82 + 0.19 5.83 + 0.21 EC (µS cm-1) 80 + 13 85 + 15 96 + 19 88 + 21 OC (g kg-1) 5.61 + 0.35 5.60 + 0.43 5.64 + 0.41 5.62 + 0.34 TN (%) 0.21 + 0.02 0.21 + 0.03 0.22 + 0.02 0.21 + 0.02 -1 Av N (kg ha ) 281 + 28 302 + 34 316 + 35 310 + 42 -1 P2O5 (kg ha ) 48 + 13 42 + 18 43 + 21 a 49 + 16

Increasing trend for the yield and yield attributes

K2O (kg ha-1)

When the crops were irrigated with 1:1, yield advantage ranged from 3% with okra to 11% with ridge gourd

Na (mg kg-1)

4.3 **

182 + 18 30 + 9

188 + 21 33 + 11

193 + 25 38 + 16

Yield advantage was there

191 + 19 35 + 14

The yield advantage ranged from 9% (13.1 t/ha) for bitter gourd to 15% (9.2 t/ha) with cucumber.


Trace metals in soils Cd - concern ?

Accumulations are less in fruits and more in leaf


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 Conclusion

Urban wastewater is resource for increase vegetable productivity

Reclamation within agricultural system

Conjunctive use of urban wastewater with other water source for vegetable production  

Seminar Session 13

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