Contents lists available at ScienceDirect Aquacultural Engineering journal homepage: www.elsevier.com/locate/aque Remediating sulfadimethoxine-contaminated aquaculture wastewater using ZVI-activated persulfate in a flow-through system Chanat Chokejaroenrat a , Chainarong Sakulthaew b, ⁎ , Athaphon Angkaew a , Tunlawit Satapanajaru a , Amnart Poapolathep c , Tharisara Chirasatienpon d a Department of Environmental Technology and Management, Faculty of Environment, Kasetsart University, Bangkok, Thailand b Department of Veterinary Technology, Faculty of Veterinary Technology, Kasetsart University, Bangkok, Thailand c Department of Pharmacology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand d Department of Physical Education, Faculty of education, Kasetsart University, Bangkok, Thailand ARTICLE INFO Keywords: Aquaculture wastewater Flow-through system Persulfate oxidation Sulfadimethoxine ZVI activation ABSTRACT Antibiotic resistant bacteria can result from the improper discharge of water from the aquaculture farming industry. This calls for the development of a low-cost remediation technology. Our research verified the use of ZVI-activated persulfate (PS) to treat antibiotic-contaminated aquaculture discharge water in a flow-through system. We selected sulfadimethoxine (SDM) as a representative antibiotic residual and tested SDM degradation under varying parameters: activator dose, initial pH, chloride concentration, activator dose and timing. The results demonstrated that increasing the ZVI dosage significantly decreased SDM degradation due to the scavenging effects for the persulfate radical (SO 4 %- ). SDM decomposition occurred when SO 4 %- attacked the aniline moiety via electron transfer prior to undergoing hydrogen abstraction/addition on the sulfonamide. A high pH produced the fastest degradation with reaction rates following the order pH 11 > > pH 9 > pH 3 > pH 5. A high Cl - concentration (> 100 mM) enhanced SDM degradation because of the production of chlorine radicals. The experiment results from ZVI sequential addition indicated that only a small continual input of ZVI was sufficient to generate SO 4 %- to react with SDM. We used a flow-through concept for the real discharge water that was spiked with SDM prior to treating with PS/ZVI. The results showed that our system was able to remove approximately 68% of SDM from filtered and 74% from unfiltered discharge water. These results provide proof-of-concept that our PS/ZVI system could potentially be developed to remediate antibiotic-con- taminated aquaculture wastewater. 1. Introduction Veterinary antibiotics are an indispensable input for aquaculture practices. While both prophylactic and therapeutic uses of antibiotics are very common, many farmers have insufficient information on the efficient use of antibiotics (Kumar et al., 2005; Alarcon et al., 2014; Moreno, 2014; Speksnijder and Jaarsma, 2015). Improper discharge from aquaculture farming may affect the environment by introducing antibiotic-resistant pathogens that can be self-developed and trans- ferred among local microorganisms in the environment (Jørgensen and Halling-Sørensen, 2000; De Liguoro et al., 2003; Kay et al., 2004; Brambilla et al., 2007; Hatosy and Martiny, 2015; Heuer et al., 2002; Bergeron et al., 2015). Sulfadimethoxine (SDM) is one of the most-used veterinary antibiotics for the treatment of bacterial infections in freshwater ani- mals (Gutiérrez et al., 2010; Morrison and Saksida, 2013; Ou et al., 2015; Boison and Turnipseed, 2015). Dietze et al. (2005) collected 189 water samples from 13 freshwater hatcheries and detected 23 samples contaminated with SDM. An SDM concentration range of 11 to 74 ng/l was found in Italian surface and drinking water (Perret et al., 2006). Brambilla et al. (1994) found that SDM reduced the hatching rate for Artemia sp. cysts and caused a high mortality rate for Artemia sp. nauplii. Compounding the high use rate of SDM is the fact that it is not very biodegradable (Wang et al., 2006; Ingerslev, Halling-Sørensen, 2000). Choi et al. (2007) elucidated that SDM self-decomposition was slow and possibly remained in aqueous matrices for weeks. Therefore, SDM oxidation via chemical treatment is likely needed to jump start the biodegradation process. https://doi.org/10.1016/j.aquaeng.2018.12.004 Received 23 May 2018; Accepted 15 December 2018 ⁎ Corresponding author. E-mail addresses: chanat.c@ku.ac.th (C. Chokejaroenrat), cvtcns@ku.ac.th (C. Sakulthaew), athaphon.ak@gmail.com (A. Angkaew), fscitus@ku.ac.th (T. Satapanajaru), fvetamp@ku.ac.th (A. Poapolathep), fedutrc@ku.ac.th (T. Chirasatienpon). Aquacultural Engineering 84 (2019) 99–105 Available online 19 December 2018 0144-8609/ © 2018 Elsevier B.V. All rights reserved. T