Behaviour of physicochemical and microbiological characteristics of vertical flow constructed wetland substrate after treating a mixture of urban and olive mill wastewaters.

Ayoub El Ghadraoui,Naaila Ouazzani,Abdessamed Hejjaj,Laila Mandi,Massimo Del Bubba,Faissal Aziz,Chaima Saf,Abdelaali Ahmali

doi:10.1007/s11356-021-14874-7

Ayoub El Ghadraoui, Naaila Ouazzani + Show 6 more

Open Access

https://doi.org/10.1007/s11356-021-14874-7

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Abstract

The aim of the current work is to evaluate the effect of a mixture of olive mill wastewater (OMWW) and urban wastewater (UW) on constructed wetland (CW) substrate physicochemical parameters, and to study the abundance and behaviour of microbial community at different depths. In this regard, substrate samples were investigated at three depth levels (0-10 cm, 10-20 cm and 20-30 cm) inside a pilot scale CW treating the mixture. In order to compare the obtained results with the conventional case, a control (CW pilot plant treating only UW) was implemented. Result shows that an increase in electrical conductivity (from 0.134 to 0.222 mS/cm in 0-10 cm and from 0.131 to 0.283 mS/cm in 10-20 cm), total dissolved salts (from 65.45 to 108.67 mg/kg in 0-10cm and from 64.33 to 135.3 mg/kg in 10-20 cm), total organic carbon (from 0.86 to 6.84%), total nitrogen (from 0.1 mg/kg to 0.45, 0.43 and 0.41 mg/kg, in 0-10 cm, 10-20 cm and 20-30 cm respectively) and C/N ratio take place in the substrate after the treatment of the mixture. As for the microbiological parameters, treating the mixture in a CW results in an increase in the yeast and fungi which may optimize the biodegradation of compounds such as polyphenols that are non-easily degraded.

Highlights

Olive oil production is an important agro-industrial activity especially in Mediterranean countries (Elmansour et al 2020; Bruzzoniti et al 2020)
olive mill wastewater (OMWW) is acidic, characterized by a high conductivity 28.23 mS/cm, a high organic content evaluated in terms of COD 264.05 g/l and high content of total suspended solids of 2066 mg/l
The effects of OMWW application on substrate physicochemical parameters were observed at all depths

Summary

Introduction

Olive oil production is an important agro-industrial activity especially in Mediterranean countries (Elmansour et al 2020; Bruzzoniti et al 2020). Different treatment methods have been studied in lab and in large scale including physical (dilution, filtration, evaporation, sedimentation and centrifugation), biological (activated sludge) and physicochemical (flocculation, precipitation, adsorption, chemical oxidation, ion exchange and coagulation) treatments. These treatments were either not able to reduce organic loads and toxicity to acceptable limits or are relatively expensive as energy or large quantities of chemicals are required (Pelendridou et al 2014; Paraskeva and Diamadopoulos 2006; Mantzavinos and Kalogerakis 2005; Galanakis 2017). Novel materials such as pozzolan (El Ghadraoui et al 2020), tire chips (Chyan et al 2013), oyster shells (Park and Polprasert 2008) and construction wastes (Shi et al 2017) have proven their efficiency in the increase of the treatment capacity and the prevention from clogging issues in constructed wetlands

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