Contents lists available at ScienceDirect Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe Effect of intermittent aeration cycles on EPS production and sludge characteristics in a field scale IFAS reactor Nitin Kumar Singh a, ⁎ , Siddhartha Pandey b , Rana Pratap Singh c , Swati Dahiya b , Sneha Gautam a , Absar Ahmad Kazmi b a Department of Environmental Science and Engineering, Marwadi Education Foundation's Group of Institutions, Rajkot, 360003, India b Environmental Engineering Group, Dept. of Civil Engineering, Indian Institute of Technology, Roorkee, 247667, India c Dept. of Civil Engineering, Katihar College of Engineering, Katihar, 854106, India ARTICLE INFO Keywords: IFAS Intermittent aeration Sludge characteristics Extracellular polymeric substances Energy saving ABSTRACT In the present study, an integrated fixed-film activated sludge (IFAS) bioreactor was subjected to dissimilar intermittent aeration (IA) cyclic operations, and its effects were investigated on extracellular polymeric sub- stances (EPS) production, sludge characteristics, and specific power consumption. A total of three IA cycles (IA1, 150 min aeration on and 30 min off; IA2, 120 min aeration on and 60 min off; IA3, 90 min aeration on and 60 min off) were evaluated in the present IFAS reactor. Specific EPS production (mg/g of suspended solids) was found to be following the increasing trend with respect to the non-aeration to aeration time ratio, whereas, the sludge production followed the reverse trend. The amount of bound EPS was observed to be much higher (6–10 times) than soluble microbial product (SMP) in each intermittent aeration phase. During all the investigated IA cycles, the pilot was observed to be significantly affected in terms of biomass characteristics, which was also confirmed by increasing trends of sludge volume index (SVI) and filamentous index (FI) values. In-situ mon- itoring and measurement of reactor operation parameters such as pH, oxidation reduction potential (ORP), and dissolved oxygen (DO) was also done in all IA cycles. A maximum of 27.05% reduction in electrical energy was observed in highest non-aeration period cycle. 1. Introduction All the biological wastewater treatment systems (suspended and/or attached) produce a complex mixtures of high-molecular-weight sub- stances i.e. polymers secreted by microorganisms, produced from cell disintegration, and adsorbed substrate from wastewaters [1], which are known as extracellular polymeric substances (EPS). These materials play a consequential role in enhanced settling of biomass, and helps them to form the microbial clusters in a wastewater treatment system. The prime components of EPS mixture include macromolecules such as carbohydrates and proteins, which exerts influence on bio-chemical characteristics of microbial consortium [2]. Furthermore, the two forms of EPS exist at outer surface of microbial cells which can be categorized as bound EPS and soluble EPS [3,4]. As the classification term implies, the bound EPS are closely attached with microbial cells, whereas so- luble EPS are those compounds which are either loosely bound with cells or dissolved into the mother solutions [5]. In spite of significant research on EPS, many other factors play important role which could influence the composition and production rate of EPS in environmental systems. This quantitative as well as qualitative variation in con- stituents of the extracted EPS may be attributed to various factors such as type of wastewater, biomass conditions, operational parameters, bioreactor type, and extraction method etc. [3]. Among the various important operational parameters of bioreactors, solid retention time, shear rate or aeration intensity, and aerobic or anaerobic conditions were found to be affecting the EPS production and composition as well. However, the results published in literature are slightly contradictory as some reported increasing trend while others observed the decreasing trend of EPS production with similar change in operating conditions [5,6–9]. To date, although ample amount of literature is published about EPS quantification methods but more studies are required to in- vestigate their roles in the biological wastewater treatment systems under different operational conditions. Therefore, to gain confidence about the fate of EPS it is important to conduct more studies under stressed conditions to investigate the behaviour of biomass with respect to EPS production. https://doi.org/10.1016/j.jwpe.2018.03.012 Received 25 December 2017; Received in revised form 13 March 2018; Accepted 20 March 2018 ⁎ Corresponding author. E-mail addresses: nitin261187@gmail.com (N.K. Singh), siddhartha22@hotmail.com (S. Pandey), rps.eng@gmail.com (R.P. Singh), swatidahiya100@gmail.com (S. Dahiya), gautamsneha@gmail.com (S. Gautam), absarkazmi@yahoo.com (A.A. Kazmi). Journal of Water Process Engineering 23 (2018) 230–238 2214-7144/ © 2018 Elsevier Ltd. All rights reserved. T