Effluent application to the land: Changes in soil properties and treatment potential

Four pilot land treatment systems (LTS) planted with different plant species were investigated as a means of managing wastewater in small communities. The effects of effluent application on soil properties during three years of operation are presented. LTS were planted with Eucalyptus camaldulensis, Acacia cyanophylla. Populus nigra and Arundo donax. Wastewater was pre-treated in a septic tank and applied to LTS at suitable rates to meet crop water requirements. Effluent application was found to increase soil organic matter, P and TKN content, particularly, in the topsoil but plant species had no effect on these parameters. Increases were also observed for salinity and sodium adsorption ratio which were found to depend on hydraulic loading. Winter precipitation leached the majority of the salts accumulated during the application period. Nitrates accumulated in the soil profile throughout the application period and this increase was dependent on plant species. LTS planted with A. donax showed the lowest NO3-N concentration in soil pore water, an effect which cannot be explained by differences in application rates or plant uptake. This may imply stimulated denitrification rates induced by the rhizosphere of reeds. Effluent application also increased total and macro porosity compared to their initial values and bulk density. (C) 2011 Elsevier B.V. All rights reserved.