Cork industry wastewater partition by ultra/nanofiltration: A biodegradation and valorisation study

Abstract

Abstract:Wastewater from cork processing industry present high levels of organic and phenolic compounds, such as tannins, with a low biodegradability and a significant toxicity. These compounds are not readily removed by conventional municipal wastewater treatment, which is largely based on primary sedimentation followed by biological treatment. The purpose of this work is to study the biodegradability of different cork wastewater fractions, obtained through membrane separation, in order to assess its potential for biological treatment and having in view its valorisation through tannins recovery, which could be applied in other industries. Various ultrafiltration and nanofiltration membranes where used, with molecular weight cut-offs (MWCO) ranging from 0.125 to 91 kDa. The wastewater and the different permeated fractions were analyzed in terms of Total Organic Carbon (TOC), Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Phenols (TP), Tannins, Color, pH and Conductivity. Results for the wastewater shown that it is characterized by a high organic content (670.5-1056.8 mg TOC/L, 2285-2604 mg COD/L, 1000-1225 mg BOD/L), a relatively low biodegradability (0.35-0.38 for BODs/COD and 0.44-0.47 for BOD20/COD) and a high content of phenols (360-410 mg tannic acid/L) and tannins (250-270 mg tannic acid/L). The results for the wastewater fractions shown a general decrease on the pollutant content of permeates, and an increase of its biodegradability, with the decrease of the membrane MWCO applied. Particularly, the permeated fraction from the membrane MWCO of 3.8 kDa, presented a favourable index of biodegradability (0.8) and a minimized phenols toxicity that enables it to undergo a biological treatment and so, to be treated in a municipal wastewater treatment plant. Also, within the perspective of valorisation, the rejected fraction obtained through this membrane MWCO may have a significant potential for tannins recovery. Permeated fractions from membranes with MWCO lower than 3.8 kDa, presented a particularly significant decline of organic matter and phenols, enabling this permeates to be reused in the cork processing and so, representing an interesting perspective of zero discharge for the cork industry, with evident environmental and economic advantages. (C)

Cork processing wastewaters components fractioned by ultrafiltration membranes – studies of antioxidant and antitumoral activity

“…The operating conditions were set in a way that polarization concentration was minimized, i.e. the feed flowrate was set for the maximum value and the transmembrane pressure was kept as low as possible . Other characteristics of this type of membranes have been reported previously by the authors …”

“…These wastewaters were characterized by Minhalma et al . and it has been shown that values for pH (4.97–5.1), COD (2230–7262 mg O 2 L ‐1 ) and BOD 5 (1125–2642 mg O 2 L ‐1 ) are well outside the LEV (limit emission value according to EU directive 91/271/CEE, 6.0 < pH < 9.0; COD < 150 mg L ‐1 ; BOD 5 < 40 mg L ‐1 ) making its release to the environment, without appropriate treatment, hazardous . Total polyphenols and tannin content in these wastewaters can rise to 1.0 g L ‐1 and 0.7 g L ‐1 , respectively, after 4 days of the boiling process, and a low degree of biodegradability (BOD 5 /COD = 0.3) was also observed.…”

“…In previous work, Minhalma et al . also identified and quantified polyphenols (PPs), which are abundant in these wastewaters, such as ellagic and gallic acids …”

Enzyme membrane reactor coupled with nanofiltration membrane process for difructose anhydride III from inulin conversion

“…NF membrane had nominal molecular weight cut-off (MWCO) ranging from 90 to 1000 Da, which could be selected to make the high retention of compounds with molecular weight of over 300 Da molecules. Thus, NF technology had a wide range of applications in various aspects for peptides fractionation, sugar concentration and waste water recycling [13,15,16]. UF and NF membranes have been applied for removing cyanotoxins [17], fractionating whey-derived peptides [16], recovering polyphenols from bergamot juice [18], refining soluble products from rice husk xylan [19] and recycling dairy wastewater [20].…”

Energetic and biochemical valorization of cork boiling wastewater by anaerobic digestion

“…This presents high acute toxicity for several tested organisms [4,5], which means that CBW has to be treated before disposal. The studies undertaken regarding CBW treatment comprise simple and combined methodologies that have been largely based on physical and chemical processes, such as: ultrafiltration and/or nanofiltration [6-11]; flocculation/flotation/ultrafiltration [12]; ozone and membrane filtration [13]; ozonation combined with hydrogen peroxide and UV radiation [14,15]; solarphoto-Fenton and solarphotocatalysis [16,17]; and Fenton oxidation-coagulation/flocculation [18]. However, many of these treatments are expensive and may give rise to pollutants.…”