Journal of Applied Sciences1812-56541812-5662Asian Network for Scientific Information10.3923/jas.2009.901.908Al-OthmanAhmed A.5200995The study was carried out to determine the effect of
treated domestic wastewater (TDW) on physical, chemical and microbial
properties of three soils. There was no significant change in the sand,
silt and clay fractions after 458 days of TDW irrigation. The parameters
included soil pH, which remained within moderately alkaline region after
458 days of TDW irrigation. The SAR of A and B soils changed from 3.27-2.95
and 3.67-2.15, respectively after 200 days of irrigation. But, the decrease
in SAR was less in the same soil when irrigated with TDW continuously
for 458 days compared to 200 days due to salt leaching to lower soil depths.
The concentration of cations (Na^{+}, K^{+}, Ca^{2+},
Mg^{2+}) showed significant (p<0.001, p<0.032) increase
after 200 days followed by a significant (p<0.001, p<0.008) decrease
after 458 days of TDW irrigation. The concentrations of Na^{+}
in A and B soils decreased with the soil depth except soil C which showed
the highest concentration of K as 13.9 meq L^{-1} than the control
sample as 3.2 meq L^{-1} after 200 days of irrigation and at 150
cm soil depth. The K^{+} concentration increased from 0.2 to 0.5
meq L^{-1} and 0.2-0.8 meq L^{-1} in A and B soils, respectively.
However, at 458 days of irrigation, the K^{+} concentration dropped
below, 0.2 meq L^{-1} in both samples. The electrical conductivity
(EC), sodium absorption ratios (SAR), cations (Na+, K^{+}, Ca^{2+},
Mg^{2+}) and anions (CO_{3}^{2}¯, HCO_{3}¯,
Cl¯, SO_{4}^{2}¯) showed similar patterns. But
the values of these cations/anions increased after 200 days of irrigation
which again dropped below the initial values of soils. The average number
of bacteria in soil A, B and C after 200 days and 458 days of TDW irrigation
were 99 and 393 cells, 149 and 333 cells and 56 and 559 cells, respectively.
In addition to the above, the microbial analysis indicated that E.
coli was absent in all the soils irrigated with TDW. The research
findings suggest that although the TDW irrigation did not mainly affect
the physical and chemical properties of soil under investigation, but
is likely to contaminate the groundwater on long term basis in Riyadh
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