Organic waste vermicomposting through the addition of rock dust inoculated with domestic sewage wastewater

Abstract

The aims of the present study are to assess the organic waste vermicomposting process (cattle manure mixed with tannery sludge) by using inorganic waste (rock dust) inoculated with treated domestic wastewater sewage, as well as the vermicompost application in Ruellia brittoniana seedling production. Different proportions of organic and inorganic waste moistened (or not) in wastewater were vermicomposted (by Eisenia foetida) for 120 days in the first stage of the experiment. Statistically significant earthworm density increase was observed between the 60th and 90th experimental vermicompositing days in all the assessed groups. There was decreased E. foetida population density after 90 days. The K, P, TOC, C/N ratio and Ca, Na and Mg concentrations significantly decreased at the end of the vermicompositing process in comparison to the initial concentrations identified in most treatments. On the other hand, there was pH and N, Fe, Zn and Mn concentration increase in most of the vermicomposts assessed at the end of the experiment. All plants grown in soil containing vermicomposts presented higher Dickson Quality Index (DQI) than the control group, which was cultivated in soil containing commercial topsoil. Plants grown in soil containing 100% cattle manure and tannery sludge, moistened in treated domestic wastewater sewage, showed the highest DQI. Thus, the vermicomposting waste used in the present study, which was inoculated with treated domestic wastewater sewage, is an interesting vermicompost production technology to be used in ornamental plant production.