Author:
Sparling G. P.,Williamson J. C.,Magesan G. N.,Schipper L. A.,Lloyd-Jones A. Rh.
Abstract
Application of wastewater can decrease the hydraulic conductivity of soils,
and so reduce future loading rates. A possible mechanism for this decrease is
blockage of soil pores by microbial growth and extracellular carbohydrate
production. Our objective was to determine whether wastewater characteristics
that increased microbial biomass and carbohydrate also decreased soil
hydraulic conductivity. In field trials, irrigation of secondary-treated
wastewater for 7 years onto a sandy soil increased carbohydrate, but had no
effect on microbial C or unsaturated hydraulic conductivity, relative to
non-irrigated soil. Irrigation of tertiary-treated wastewater for 5 years onto
an allophanic soil had no significant effect on these soil characteristics.
Effects on soil properties of wastewater with differing carbon : nitrogen (C :
N) ratio were examined in the laboratory on repacked cores of the allophanic
soil over 14 weeks. Unsaturated hydraulic conductivity decreased significantly
in cores irrigated with the high C: N wastewater. These cores also exhibited
an increase in soil carbohydrate content, microbial biomass, and respiration
relative to cores irrigated with water. This study has demonstrated that the
land treatment of industrial wastewaters of high C: N ratio and high
biochemical oxygen demand could be problematic, even on freely draining soils.
Subject
Earth-Surface Processes,Soil Science,Environmental Science (miscellaneous)
Cited by
70 articles.
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