Contents lists available at ScienceDirect Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe Removal of nitrogen by a sulfur-based carrier with powdered activated carbon (PAC) for denitrification in membrane bioreactor (MBR) Yun Chul Woo a , Jeong Jun Lee b , Ahyoung Jeong c , Jiyoung Song c , Youngkwon Choi d , Han-Seung Kim c, * a Department of Land, Water, and Environment Research, Korea Institute of Civil Engineering and Building Technology (KICT), 283 Goyang-Daero, Ilsanseo-Gu, Goyang-Si, Gyeonggi-Do, 10223, Republic of Korea b BKT Inc., 25 Yuseong-Daero 1184 Beon-gil, Yuseong-Gu, Daejeon, 34109, Republic of Korea c Department of Environmental Engineering and Energy, Myongji University, 116 Myongji-Ro, Cheoin-Gu, Yongin-Si, Gyeonggi-Do, 17058, Republic of Korea d Extreme Engineering Research Center (E2RC), Korea Institute of Civil Engineering and Building Technology (KICT), 283 Goyang-Daero, Ilsanseo-Gu, Goyang-Si, Gyeonggi-Do, 10223, Republic of Korea ARTICLE INFO Keywords: Sulfur-based carrier Powdered activated carbon Membrane bioreactor Nitrogen removal Denitrification ABSTRACT In this study, the effect of the addition of powdered activated carbon (PAC) to sulfur-based carrier for auto- trophic denitrification was evaluated on the removal efficiency of nitrate in MBR process for advanced waste- water treatment without any external organic carbon source. As a result of the comparative experiment with PAC 0 % and 15 % carrier, the removal efficiency of NO 3 − -N was enhanced up to 3 % by adding PAC to the carrier. Based on the results, the carrier was injected every seven day with 10 % of reactor volume. During the operating period of 30 days, the removal of T-N was 72.7 % and 31.8 % for the operating condition with and without the carrier, respectively. In the long-term MBR experiments, which was operated with the addition of the carrier to anoxic tank day by day, the tendency of T-N removal was relatively stable. The removal of T-N was observed at 55.80 % and 19.73 % for with and without the carrier, respectively. Based from the results, it was obvious that the removal of T-N was enhanced to around 40 % by adding the sulfur-based carrier into MBR system. The present study exhibited relatively good efficiencies so that the sulfur-based carrier will be applied for a pilot experiment. 1. Introduction As the water quality, a standard of the nitrogen in the effluent from the wastewater treatment plant is getting continuously strengthened, development of practical treatment technology for high-quality treat- ment becomes increasingly important [1]. The discharge of nitrogen containing sewage or waste water, not only adversely affects aquatic ecosystems such as eutrophication, dissolved oxygen depletion, but also poses risks to human health and living environment such as methe- moglobinemia. EPA defined the maximum contaminant level (MCL) of drinking water of nitrate as 10 mg/L [2]. The biological treatment processes for the removal of nitrogen from contaminated nitrate containing groundwater are considered to be en- vironmentally friendly and economical processes because it utilizes microbial metabolism, unlike the physicochemical treatment processes in which nitrogen are removed by injecting a chemical [3,4]. Several biological treatment processes for nitrogen removal have been studied, including MLE (Modified Ludzack-Ettinger), A2/O (Anaerobic/Anoxic/ Oxic), and UCT (University of Cape Town) [5–7]. Such processes re- quire a large area, and particularly in the case of sewage having a low C/N ratio, it takes a lot of energy to supply oxygen necessary for ni- trification and requires an external carbon source such as methanol to be added [8]. Recently, to overcome these problems, an advanced treatment processes using autotrophic denitrification, which use hydrogen, iron, sulfur or the like as an electron donor is attracting attention. Among them, sulfur (S) based autotrophic denitrifiers utilize sulfur as their electron donor, inorganic carbon such as HCO 3 − as a carbon source and nitrate as a final electron acceptor. The stoichiometric formula is as shown in the following equation [9]: NO 3 − + 1.11S + 0.4CO 2 + 0.76H 2 O + 0.08NH 4 + → 0.5N 2 + 1.1SO 4 2- + 1.28H + + 0.08C 5 H 7 O 2 N (1) This process does not require an external carbon source such as https://doi.org/10.1016/j.jwpe.2020.101149 Received 10 August 2019; Received in revised form 31 December 2019; Accepted 8 January 2020 ⁎ Corresponding author. E-mail address: kimhs210@mju.ac.kr (H.-S. Kim). Journal of Water Process Engineering 34 (2020) 101149 2214-7144/ © 2020 Elsevier Ltd. All rights reserved. T