The Effects of Olive Mill Wastewater on Soil Microbial Populations

Abstract

Olive mill wastewater (OMW) is a common pollutant in Jordan due to the large number of olive mills and the importance of the olive oil industry in the country. In this study, the effects of OMW and fertilizer on soil microbial populations were examined by counting the number of microbial colonies on each plate after respective treatments with water, OMW, and fertilizer. Colonies were identified based on macroscopic and microscopic examination as well as a range of biochemical tests. After treatment with OMW, a significant increase was exhibited in the Bacillus (p-value of 0.011 in clay) and Yeast (pvalues of 0.001 in clay and 0.037 in sand) populations. In contrast, Staphylococcus, Streptomyces (p-values of 0.034 in clay and 0.016 in sand) and Mold (p-value of 0.013 in sand) exhibited population decreases. Our results showed that OMW significantly affects natural soil microbial populations, which is an important finding as most of the OMW in Jordan is disposed of in a way that exposes it to the soil. This study illustrated that OMW has a potential to be recycled and utilized as an antibacterial agent. Further studies should be conducted using molecular PCR analysis in order to accurately determine the species of each studied microorganism.