Application of nanofiltration for reuse of municipal wastewater and quality analysis of product water

doi:10.1016/j.desal.2012.11.015

Desalination

Volume 315, 15 April 2013, Pages 33-36

https://doi.org/10.1016/j.desal.2012.11.015 Get rights and content

Abstract

In this study, the municipal wastewater treated by biological methods was used for further treatment by nanofiltration method for wastewater reuse. For this purpose, different nanofiltration (NF) membranes, such as CK, NF-90, and NF-270 were employed. The quality analysis of product water was carried out using various analytical techniques. The results revealed that the NF-90 membrane can produce the best water quality compared to other two membranes. The CK membrane showed also a good rejection property after NF-90 membrane but its big inconvenience is that it gave a lower water flux. Despite the good water flux by NF-270, the permeate quality obtained with this membrane was not as good as obtained with the NF-90 and CK membranes.

Highlights

► Reuse of bio-treated municipal wastewater ► Application of nanofiltration for wastewater reuse ► Best product water quality with NF-90 membrane

Introduction

Globally, the water resources in various regions and countries are expected to face unprecedented pressures in the coming decades as a result of continuing population growth and uneven distributions of population and water. The concentration of populations within urban areas further exacerbates the disparity between water demand and regional water availability [1].

Wastewater can be an alternative water resource which can decrease the demands for fresh water. Some municipalities and industries are dealing with high salt concentration in their wastewaters. Saline effluents are conventionally treated through physicochemical means, as biological treatment is strongly inhibited by salts [2]. Most of such systems involve anaerobic or aerobic biological treatment. Biological treatment systems offer the best alternative to treat wastewaters containing carbonaceous organic and nitrogen matter [3]. However, high salt content in wastewater is known to significantly reduce the treatment efficiency of conventional activated sludge, anaerobic, nitrification and denitrification processes [4], [5].

In order to attain the environmental standards, membrane technologies provide an important solution in wastewater discharge, reuse and recovery of water, recycling valuable components from the waste streams [6]. Those membrane technologies are namely nanofiltration (NF) and reverse osmosis (RO) that can be used as advanced treatment technologies. NF falls between ultrafiltration and reverse osmosis and its separation characteristics are based on sieve effect. But most commercial NF membranes are also charged, so ion rejection by NF membranes results from the combination of electrostatic and steric interactions associated with charge shielding, Donnan exclusion and the degree of ion hydration [7], [8].

In this study, different kinds of NF membranes were investigated for assessing their performance in rejection of contaminants that are not removed by biological treatment of municipal wastewater. The product water quality was compared with irrigation water standards in order to assess its reusability in agriculture for irrigation.

Section snippets

Materials and methods

NF tests were performed by using a cross-flow flat-sheet membrane test unit (SEPA CF-II, GE) for the filtration of the conventionally bio-treated municipal wastewater. The flow sheet of the membrane filtration system was shown in Fig. 1.

In this study, three different types of NF membranes were used. Two of them namely NF-270 and NF-90 (Dow-FilmTech) are thin film polyamide membranes with a surface negatively charged and one is cellulose acetate membrane, CK (GE-Osmonics). The membrane

Results and discussion

Conventionally bio-treated municipal wastewater was further treated by using NF membranes. As the three NF membranes tested have different properties; their performances were also obtained as different. Regarding to the membrane pore size; the more effective membrane was NF-270 with a permeate flux which rises up to 81 L/h m². The membranes NF-90 and CK showed a permeate flux up to 49.3 L/h m² and 26.6 L/h m², respectively. However, except for the CK membrane; the two other membranes showed some

Conclusions

Conventionally bio-treated municipal wastewater was further treated by NF membranes using 10 bar of applied pressure and a concentrate flow rate maintained at 96 L/h. The product water quality obtained was different for each membrane. The best water quality was obtained with the NF-90 membrane. According to the obtained results, it was concluded that NF could be a potential method to reuse biologically treated municipal wastewater for irrigation purposes.

Acknowledgment

This work was partly supported by Ege University Scientific Research Project (EU-2011-FEN-089). We acknowledge Izmir Metropolitan Municipality Directorate-İZSU-Çiğli Wastewater Treatment Plant for bio-treated wastewater samples. We acknowledge Dr. Markus Busch and Mr Eduard Gasia Bruch, Dow Chem. for sending us some of the NF membrane samples. We thank M. Akçay for AAS analyses and G. Serin for TOC analyses.

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Application of nanofiltration for reuse of municipal wastewater and quality analysis of product water

Abstract

Highlights

Introduction

Section snippets

Materials and methods

Results and discussion

Conclusions

Acknowledgment

Desalination

Desalination

Sep. Purif. Technol.

J. Membr. Sci.

Desalination

Mem. Technol.