Olive mill wastewater treatment using a solar reactor and reuse of the waste as liquid fertilizer

Purpose The main aim of this study was to treat olive mill wastewater (OMW) using a photo-Fenton s solar reactor; to investigate its potential use as liquid fertilizer and to evaluate its impact on pepper crop. Method Olive mill wastewater was collected in a tank 1000 L and supplemented with 2000 gr FeSO4.7H2o. After that, 150 ml H2O2 was added to the tank to start Fenton s reactor. The treated OMWwas collected in a container and NaOH with a concentration of 1 M was added to improve the pH of the treated OMW. Pepper seedlings were cultivated on 16 February, 2020 inside the greenhouse for a period of five months. The treated OMW was used as liquid fertilizer and compared with chemical fertilizer as control. Results The pH and electrical conductivity of treated OMW were 7.5 and 7.6 dS/m, respectively. Furthermore, the control produced the highest yield and fruit number significantly (p 0.05) compared to the other treatments, followed by OMW treated by stabilization bond (SB-OMW100%). Also the treatments fertilized by OMW treated by solar reactor (SR-OMW50%) and stabilization bond (SB-OMW100%) produced the same plant length at the end of the growing period. Conclusion The concentrations of N, P, and K of treated OMW (0.21, 0.06, and 0.68 respectively) were quite low and supplementary fertilization was necessary to improve the nutrients value of the treated OMW. The solar reactor could be a valuable and useful tool in treatment of olive mill wastewater for agricultural purposes mainly on small scale sites.