Abstract
The treatment of the yeast industry wastewater was investigated by nanofiltration (NF) membrane process on a pilot scale. Two wastewaters were used as feed: (i) dilute wastewater with COD 2000 mg/L and (ii) concentrate wastewater with COD 8000 mg/L. The permeate flux, COD retention, color and electrical conductivity (EC) removal were evaluated in relation to trans-membrane pressure and long-term filtration. A linear growth in permeate flux was found with increasing in trans-membrane pressure for wastewaters. In addition, the COD retention, color and EC removal increased with trans-membrane pressure enhancement. The results obtained from the long-term nanofiltration of dilute wastewater indicated that the permeate flux decreased from 2300 L/day to 1250 L/day and COD retention increased from 86% to 92%. The quality of the permeate in term of COD is lower than the discharge standard in river (200 mg/L). Thus, this process is useful for treatment of wastewaters produced by yeast industry.
Highlights
The increasing demand of bread as staple food of human beings has developed backer’s yeast industry
Permeate flux of nanofiltration system during filtration of wastewaters The passage of water through the membranes or permeability, which is an important parameter in the design and economical feasibility analysis of membrane separation processes, depends on several parameters including transmembrane pressure, operating temperature, feed velocity, feed solution concentration and membrane properties such as porosity, material, hydrophilicity, roughness and charge
The current study shows that the pilot scale nanofiltration process is technical and efficient process for treatment of the yeast industry wastewater
Summary
The increasing demand of bread as staple food of human beings has developed backer’s yeast industry. The sugar beet molasses are used as a main raw material. These molasses contains 45–50% residual sugars, 15–20% nonsugar organic substances, 10–15% ash (minerals), and about 20% water [1]. A major part of the non-sugar substances in the molasses are not assimilable by the yeast and are released unchanged to the processing wastewater. These compounds represent the principal waste from the yeast production process [2]. A high chemical oxygen demand (COD), dark color, and high concentrations of total nitrogen (Ntot) and non-biodegradable organic pollutants are the characteristics of the wastewater produced by yeast industry [3]. Two types of wastewater are produced in Iran's yeast industry; (i) concentrate wastewater with COD of 25000 mg/L; this wastewater is originated from yeast separators and processes such as centrifuges and rotary
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