STUDIES ON THE INFLUENCE OF SEWAGE IRRIGATION WATER ON THE PROPERTIES OF RICE GROWING SOILS
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Date
2021-12-07
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Acharya N.G. Ranga Agricultural University, Guntur
Abstract
ar of submission : 2020
Investigations were carried out to characterize the sewage water, ground water and
its suitability for irrigation in Pathakadapa area of YSR Kadapa district and effect of sewage
water irrigation (>20Years) on soil physical, chemical and biological properties.
The sewage water and ground water samples collected at periodical intervals from
Pathakadapa area in four radiant directions during summer (April – June) and winter
(October to December) were analyzed for various constituents and its suitability for
irrigation was assessed.
Profile pits four in number were opened in the area receiving the sewage water
continuously for 20 years. Their morphological and pedon characteristics were studied.
Horizon wise soil samples were collected and analyzed for various Physico-chemical and
biological properties. Surface soil samples were also collected in study area and were
analyzed. Rice straw samples were collected at harvest in four radiant directions and
analyzed for chemical constituents.
Adsorption column studies were conducted to evaluate the effectiveness of soil,
biochar and rice husk ash for removal of heavy metals present in the sewage water. The
study was also looked into the effectiveness of column heights and particle size of
adsorbents in pollutants removal and the data was subjected to statistical scrutiny. The
salient findings of the investigation are summarized below.
Sewage water collected in different time periods was dark in colour with appreciable
quantities of suspended and dissolved solids with high values of BOD and COD. The
sewage effluent had alkaline pH and high EC with appreciable quantities of Cl-1
, SO4
2-
,
CO3
2-
, HCO3
-
, Na+
, K+
, Ca2+ and Mg2+ and variable amounts of heavy metals. A marked
seasonal variation in composition of sewage water was observed and further, with
distance from the source the constituents were decreased in all the directions. Sewage
water registered heavy metals Cu, Mn, Cd, Pb and Ag above the permissible limits of
FAO, (1985). The sewage water fell under the category of C4S1 as per the USSL
classification.
The ground water showed alkaline pH and high EC with appreciable quantities
of Cl-1
, SO4
2-
, CO3
2-
, HCO3
-
, Na+
, Ca2+ and Mg2+. Further, it was observed that the
concentration of Na+
, Cl-1
and NO3
- were higher in ground water than in sewage water.
Ground water registered notable amounts of heavy metal and categorized as C4S1.
The sewage water irrigation markedly increased the apparent specific gravity, pH,
EC, available NPK, organic carbon, CEC, exchangeable cations and heavy metals viz., Zn,
Cu, Fe, Mn, Cd, Pb and Ag of the pedon which are receiving sewage effluent for over 20
years. Further, with depth the values were decreased. Increased population of bacteria,
fungi and actinomycetes was observed due to sewage water irrigation. Further,
actinomycetes population increased with depth.
The surface soil samples analyzed data reveals that pH, EC, available NPK, organic
carbon, CEC, exchangeable cations and heavy metals values were high up to 1.0 km radius
from the source point and in general with distance the values were decreased. The soil
quality index developed for the study area recorded as 0.67, which falls under the category
of “moderate”.
Sewage water irrigation increased the concentration of Phosphorous and potassium
in rice straw. Though the heavy metal concentration was recorded below the
permissible limits, bioaccumulation of iron, lead, cadmium and Ag was noticed.
Adsorption column studies demonstrated that biochar is effective in sorption of
heavy metals from sewage water and further the sorption was increased with decrease
in the particle size. With increase in contact time upto 120 minutes the sorption was
increased while for Cu, Cd and Ag the equilibration was attained at 240 minutes.
The perusal of the data on the sewage water shows alkaline pH, high EC, high
exchangeable sodium and heavy metal load which limits its usage as irrigation water.
Further, bioaccumulation and soil quality index are quite alarming to use sewage water
for irrigating rice crop in the study area.
Description
STUDIES ON THE INFLUENCE OF
SEWAGE IRRIGATION WATER ON
THE PROPERTIES OF RICE
GROWING SOILS