Purpose

Olive mill wastewater (OMW) is one of the main waste streams of olive processing and its disposal can represent a relevant environmental issue in Mediterranean countries. OMW is characterised by high pollutant load, salinity and phytotoxic levels of polyphenols, but also by a high amount of organic compounds and plant mineral nutrients. This study aimed to investigate the OMW reuse as a whole effluent for its soil conditioner and fertilizer potentialities in agriculture, in the frame work of circular economy.

Methods

For this purpose, OMW was applied at three doses (50, 100 and 200 m³ ha⁻¹ year⁻¹) over three successive years in olive field. Soil physico-chemical characteristics, enzymes activities and microbial properties, olive yield and olive oil quality were analysed.

Results

The findings revealed that the electrical conductivity, organic matter, total nitrogen, sodium, and potassium soil contents increased proportionally with OMW concentration and application frequency in the soil OMW-treated layers. Compared to their control soil counterparts, aerobic bacteria and fungi increased in proportion with the OMW spreading rates. Furthermore, all the soil enzyme activities tested (dehydrogenase, β-glucosidase and urease) were enhanced in the OMW-amended soils compared to the control. Vegetative activity and olive yield showed improvement according to the OMW level spread. With the only exception of the phenol content, which was significantly higher in the oils extracted from OMW treated olive trees than the control, the oil quality parameters did not show any significant difference.

Conclusions

OMW agronomic application constitutes a suitable practice to better manage this effluent, with positive effects on olive production and oil quality. Consequently, OMW could be considered as a useful and low cost fertilizer in olive orchard requiring the use of suitable doses especially in the Mediterranean area where this practice has been extended.

中文翻译：

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橄榄磨坊废水在农林中的推广应用

目的

橄榄厂废水（OMW）是橄榄加工的主要废物之一，其处理可能代表地中海国家的相关环境问题。OMW的特点是多酚的高污染物负荷，盐度和植物毒性水平，而且还具有大量有机化合物和植物矿物质营养素。这项研究的目的是在循环经济的框架内，调查OMW作为其土壤改良剂和农业肥料潜力的整体废水的再利用。

方法

为此，在橄榄田中连续三年以三种剂量（50、100和200 m ³ ha - ¹年^-1）施用OMW 。分析了土壤理化特性，酶活性和微生物特性，橄榄产量和橄榄油品质。

结果

研究结果表明，土壤OMW处理层中土壤的电导率，有机质，总氮，钠和钾含量与OMW浓度和施用频率成正比。与对照土壤对应物相比，好氧细菌和真菌与OMW扩散速率成比例增加。此外，与对照相比，OMW改良土壤中所有测试的土壤酶活性（脱氢酶，β-葡萄糖苷酶和脲酶）均得到增强。根据OMW水平的分布，营养活性和橄榄产量均显示出改善。除了苯酚含量（从OMW处理过的橄榄树中提取的油中的酚含量显着高于对照物）外，油质参数没有显示任何显着差异。

结论

OMW农艺应用构成了一种合适的做法，可以更好地管理这种废水，并对橄榄的产量和油质产生积极影响。因此，在需要使用适当剂量的橄榄园中，OMW可以被认为是一种有用且低成本的肥料，尤其是在地中海地区，这种做法已经得到推广。