Reduction of membrane fouling in MBR by ZSM-5 nano adsorbent in various sludge retention times for phenol removal

In this paper, the effect of different sludge retention times (SRTs) on membrane fouling of membrane bioreactor (MBR) systems including synthesized ZSM-5 nano-adsorbent was investigated. Three MBRs including nano-adsorbent were applied in SRTs of 10, 50 and 100 d during six months for wastewater treatment. Soluble microbial products (SMP) and extracellular polymeric substance (EPS) concentration analyses were conducted on the sludge of the bioreactors. Particle size distribution (PSD), Fourier-transform infrared (FTIR) spectroscopy, excitation- emission matrix (EEM) fluorescence spectroscopy, gel permission chromatography (GPC) were performed for determining the properties of the formed cake. Based on GPC test, at SRT of 10 d, organic compounds with varied molecular weights had the low concentration, while compounds with lower molecular weight were found more at SRTs of 50 and 100 d. FTIR and EEM analyses also revealed high concentration of protein compounds in MBR. Consequently, the membrane fouling was decreased in MBR at SRT of 10 d compared to SRTs of 50 and 100 d. In fact, transmembrane pressure (TMP) was 15, 21 and 25 kPa for SRTs of 10, 50 and 100 d, respectively. The EEM results showed that in addition to reduction of proteins by nano-adsorbent in SRTs of 10 and 50 d, the humic compounds were also reduced. The results showed the high efficiency of ZSM-5 nano-adsorbent for reducing of membrane fouling at the low SRT.