Journal of Water Process Engineering 49 (2022) 103069 Available online 23 August 2022 2214-7144/© 2022 Elsevier Ltd. All rights reserved. Municipal wastewater treatment and fouling in microalgal-activated sludge membrane bioreactor: Cultivation in raw and treated wastewater Saleh Najaf Chaleshtori a , Mehrdad Shamskilani b , Azadeh Babaei c, * , Masoomeh Behrang d a Chemical Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), P.O. Box 15875-4413, Tehran, Iran b Department of Chemical and Materials Engineering, University of Alabama in Huntsville, Huntsville, AL 35899, USA c Chemical and Petroleum Engineering Department, Sharif University of Technology, PO Box 11365-8639, Tehran, Iran d Department of Chemical Engineering, Brigham Young University, Provo, UT 84602, USA A R T I C L E INFO Keywords: Microalgal-activated sludge Membrane bioreactor Nutrient removal Membrane fouling ABSTRACT Since the advent of conventional activated sludge biological treatment plants, their low effciency in nitrogen and phosphorus removal has become a signifcant concern. Therefore, in this study, the performance of microalgal- activated sludge membrane bioreactor (MAS-MBR) as a self-biological treatment or as a post-treatment for conventional biological treatments was investigated. A continuous MAS-MBR with two ratios of algae/sludge (only microalgae and 5:1) was used to treat raw and treated wastewater. The optimum case was achieved with the cultivation of mixed algae/sludge in raw wastewater (R2 case). In this case, the ammonium and phosphorus removal effciencies were 94.36 ± 3.5 and 88.37 ± 3 %, respectively. Furthermore, the highest oxygen pro- duction rate (OPR) and oxygen uptake rate (OUR) values were obtained in this case (145.58 ± 3 and 68.43 ± 1.5 mgO 2 /lit.d, respectively). In addition, membrane fouling was adversely increased in R2 compared with other cases, indicating the necessity of membrane cleaning for high-performance bioreactors in nutrient removal. Transmembrane pressure (TMP) jump in R2 was captured after 14 days, while the results supported that the membrane fouling was infuenced by raised production of carbohydrate fraction of soluble microbial products (SMP c ) and protein fraction of extracellular polymeric substances (EPS p ) at frst and last stages, respectively. Therefore, although the MAS-MBR is a potential candidate as a self-biological treatment, the membrane fouling is high in this case. 1. Introduction The increasing demand for water as one of the most essential and critical resources for life, and mounting water pollution are major issues of water management. Only 2.5 % of the water present on the earth is fresh, and only a small percentage of that amount is accessible for human kind [1]. In addition, the increase of population and anthropo- genic activities result in dumping of wastes into aquatic bodies, increasing inputs of nutrients (mainly nitrogen (N) and phosphorus (P)). This process leads to development of algal blooms, spread of aquatic plants, oxygen depletion, loss of key species and degradation of fresh- water ecosystems [2,3]. For these reasons, fnding an effective waste- water treatment for nutrient (mostly N and P) removal before releasing the effuent to the environment to avoid nutrient enrichment or eutro- phication which imbalance the ecosystem is an active research area [3,4]. There are several conventional methods for wastewater treatment including coagulation-focculation, electrochemical treatment, adsorp- tion, ion-exchange, ultrafltration, chemical and physical precipitation, etc. [1]. In this case, biological methods are preferred because they are more cost effcient and environmentally friendly [5]. One of the frst and most widely used methods introduced in the wastewater treatment is activated sludge (AS). Pollutants including inorganics, bacteria, and protozoa can be removed by AS [6]. One of the major drawbacks regarding AS is that this method is energy intensive which makes the search for alternative approaches essential. On the other hand, microalgae are metabolically fexible. They have the ability to grow under photoautotrophic, mixotrophic, or heterotro- phic conditions, and other metabolisms. In addition, urban wastewater is a proper source of nitrogen and phosphorous; thus, it can be used as a great source for microalgae growth. Hence, microalgae systems are considered as promising methods for treating a variety of wastewater * Corresponding author. E-mail address: a.babaee.h@gmail.com (A. Babaei). Contents lists available at ScienceDirect Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe https://doi.org/10.1016/j.jwpe.2022.103069 Received 27 May 2022; Received in revised form 12 August 2022; Accepted 13 August 2022