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Management of reject streams from hybrid membrane processes applied to phenolic compounds removal from olive mill wastewater by adsorption/desorption and biological processes

Abstract:

This work studies the valorisation of the concentrates obtained through membrane processes for the purification of olive oil washing wastewater (OOWW). The adsorption with resins/desorption process, followed by a biological treatment with sequencing batch reactor SBRs. Three different wastewater samples were treated: an ultrafiltration reject stream (UF-R), with a high organic load and low content of phenolic compounds; a nanofiltration reject stream (NF-R), which rich in phenolic compounds and with medium organic load; a stream concentrated by forward osmosis (FO-C) with high organic content and concentration of phenolic compounds. Through the adsorption/desorption process, it was possible to recover 90 % and 73 %, which corresponds to 1.69 and 1.66 g∙L−1 of the total phenolic compounds reject streams of NF-R and FO-C, respectively. With the SBRs, it was possible to eliminate around 80 % of the organic matter present in the effluent of adsorption, and also 90 % of the remaining phenolic compounds in the case of UF-R. The results obtained are promising since, on the one hand, a high recovery of phenolic compounds was achieved and, on the other hand, a large part of the organic matter of the remaining streams after adsorption was eliminated. In this way, a solution for the management of the membrane reject streams is proposed, allowing a circular economy in the wastewater treatment of olive oil processing.