Environmental Engineering Reference
In-Depth Information
Table 2
Effect of sewage sludge amendments on selected soil physical, chemical, and biological
properties
Properties
Effect
References
Physical
pH
Decrease
Epstein et al. (
1976
), Nielson et al. (1998),
Moreno et al. (
1997
)
Increase
Tsadilas et al. (
1995
), Nielson et al. (
1975
)
Soil aggregate stability
Increase
Ojeda et al. (
2003
)
Bulk density
Decrease
Ramulu (
2002
), Ojeda et al. (
2003
)
Water-holding capacity
Increase
Epstein (
1975
), Ramulu (
2002
)
Porosity
Increase
Ramulu (
2002
)
Humus content
Increase
Kulling et al. (
2001
)
Chemical
Toxic elements
Increase
Adams and Sanders (
1984
), Kulling et al.
(
2001
), Lopez- Mosaurea et al. (
1975
)
Soil organic carbon
Increase
Kladivko and Nelson (
1975
),
Singh and Agrawal (
2007, 2009
, 2010)
Electrical conductance
Increase
Martinez et al. (
2002
), Ramulu (
2002
), Singh
and Agrawal (
2007, 2009, 2010b, c
)
N and P
Increase
Martinez et al. (
2002
), Sommers (
1977
),
Hậni et al. (
1996
), Walter et al. (2000),
Singh and Agrawal (
2007, 2009, 2010b, c
)
Cation exchange capacity
Increase
Ramulu (
2002
), Soon (
1981
)
Biological
Yeast population
Increase
Kulling et al. (
2001
)
Pathogenic organisms
Increase
Kulling et al. (
2001
), Ramulu (
2002
)
Aerobic bacteria
Increase
Kulling et al. (
2001
), Ramulu (
2002
)
Soil microbial activity, soil
respiration
Increase
Garcia et al. (
1993
), Hậni et al. (
1996
),
Banerjee et al. (
1997
)
Decrease
Fließbach et al. (
1994
),
Viera and de Souza Silva (
2003
)
pH being lowered have also been reported after land application of sewage sludges
(Epstein et al.
1976
; Singh and Agrawal
2010b, c
) (Table
2
). The changes that occur
in soil pH after application of sewage sludges have been correlated with the level of
calcium carbonate existing in the sludge, and with production of acids during sludge
decomposition (Sommers
1977
). Humic acid may be released as a result of biodeg-
radation of sewage sludges rich in organic carbon; such humic acids may contribute
to lower soil pH (Moreno et al.
1997
). Sorption of metals onto soils is strongly
related to soil properties. Generally, heavy metals are more bioavailable for plant
uptake at lower pH levels; therefore, the pH of sewage sludge is an important con-
sideration for metal-toxicity potential to plants (Lepp
1981
). Several researchers
have shown that metal sorption by soils increased with increasing pH (Naidu et al.
1994
), organic matter (Gerritse and Van Driel
1984
; Udom et al.
2004
), cation
exchange capacity (Buchter et al.
1989
), and the contents of iron and manganese
oxides. However, there is a lack of information concerning the adsorption of sludge-
borne heavy metals on different soils (Sigua
2005
).
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