Response of chemical and biochemical soil properties to the spreading of biochar-based treated olive mill wastewater

TL;DR

This study shows that treating olive mill wastewater with poplar biochar reduces its harmful effects and improves soil quality by increasing organic carbon and phosphorus.

Contribution

The study demonstrates that poplar biochar is more effective than conifer biochar in treating olive mill wastewater for soil amendment.

Findings

Poplar biochar at 10% rate reduced OMW phytotoxicity and phenolic compounds by up to 28%.

Biochar-treated OMW increased soil organic carbon by 15% and microbial biomass carbon four-fold.

Soil amended with biochar-treated OMW showed no phytotoxicity on cress seeds.

Abstract

Despite the polluting potential olive mill wastewater (OMW) can be a useful source of nutrients and organic compounds to improve soil properties. The aim of this paper was to verify if biochar-based treatment of OMW could be an efficient method to contrast the richness in phenolic compounds and phytotoxicity of OMW making it more suitable. for soil amendment. In this study poplar biochar (BP) was more effective than conifer biochar (BC) in terms of adsorbing phenols and reducing phytotoxicity at different biochar rates (5 and 10 %). In soil amendment BP-treated OMW induced an increase of organic carbon by approximately 15 % and notably BP10 treated OMW enhanced available phosphorous by 25 % after 30 days of incubation. In soil amended with 10 % BP-treated OMW microbial biomass and enzymatic activities were significantly enhanced after 30 and 90 days, with no effect on cress seed germination. Therefore, biochar based-treatment could be cost-effective and able to facilitate the long-term management of OMW in terms of storage and disposal.

Image 1

•Poplar biochar at 10 % rate was able to reduce phytotoxicity of OMW especially in term of seed germination (100 %) and phenolic compounds content up to 28 % of the initial concentration after 60 d.•The soil amendment with biochar treated OMW increased the OC (+15 %) and stimulated also four-fold MB-C by after 30 d-incubation time.•Soil amended with biochar treated OMW showed no phytotoxicity on cress seeds.

Poplar biochar at 10 % rate was able to reduce phytotoxicity of OMW especially in term of seed germination (100 %) and phenolic compounds content up to 28 % of the initial concentration after 60 d.

The soil amendment with biochar treated OMW increased the OC (+15 %) and stimulated also four-fold MB-C by after 30 d-incubation time.

Soil amended with biochar treated OMW showed no phytotoxicity on cress seeds.

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