Dilution of olive mill wastewater (OMW) eliminates its phytotoxicity and enhances plant growth and soil fertility

Abstract

Olive Mill Wastewater (OMW) is phytotoxic and all attempts to treat it are expensive and therefore alternative less expensive treatment techniques should be developed. The objective of this study is to determine whether the dilution of OMW with water improves its suitability for soil application and enhances plant growth without polluting the environment. The following treatments were investigated in a randomized complete block design with four replications in a greenhouse pot experiment: (1) potable water (W); (2) undiluted OMW (100% OMW); (3) diluted OMW at a ratio of 1_water:3_OMW (75% OMW); (4) diluted OMW at a ratio of 1_water:1_OMW (50% OMW); and (5) diluted OMW at a ratio of 3_water:1_OMW (25% OMW). Pots filled with 5 kg air-dry soil and seeded with maize were watered according to the treatments. At the end of the growing period, plant and soil samples were collected for analysis. The results indicated that undiluted OMW reduced plant growth and increased soil salinity. Diluted OMW reduced its phytotoxicity, increased soil organic matter, N, P, and K. However, even diluted OMW increased soil salinity so this should be taken into consideration with continuous OMW application. It was concluded that diluted OMW (25% OMW) eliminated OMW phytotoxicity and enhanced plant growth. Such approach is a practical alternative to the expensive non-affordable by the owners of mills treatments techniques.

Keywords:

• Olive mill wastewater
• Dilution
• Maize
• Soil properties

Acknowledgments

This work was prepared in the framework of the project “Mediterranean Cooperation in the Treatment and Valorisation of Olive Mill Wastewater (MEDOLICO)” which is funded by the European Union under the ENPI Cross-Border Cooperation Mediterranean Sea Basin Programme. MEDOLICO total budget is 1.9 million Euro and it is co-financed through the European Neighborhood and Partnership Instrument (90%) and national funds of the countries participating in the project (10%). The authors acknowledge also all the partners participating in MEDOLICO project for providing us with the comments and advices.

Notes

Presented at the International Conference on Industrial Waste and Wastewater Treatment and Valorization (IWWTV 2015) May 21–23, 2015, Athens, Greece