Bioaugmentation of a biological contact oxidation ditch with indigenous nitrifying bacteria for in situ remediation of nitrogen-rich stream water Yan Jiao a,b , Qingliang Zhao a,⇑ , Wenbiao Jin c , Xiaodi Hao d , Shijie You a a State Key Laboratory of Urban Water Resource and Environment (SKLUWRE), School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China b Applied Economic Research Institute, Shanxi University of Finance and Economics, Taiyuan 030006, China c Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China d The R&D Center for Sustainable Environmental Biotechnology, Beijing Institute of Civil Engineering and Architecture, Beijing 100044, China article info Article history: Received 7 June 2010 Received in revised form 11 September 2010 Accepted 14 September 2010 Available online 21 September 2010 Keywords: Bioaugmentation Nitrifying bacteria Biological contact oxidation ditch Nitrogen-rich stream water abstract In this study, specialized bacteria were domesticated and cultivated with polluted stream water. The bioaugmentation of specialized bacteria would significantly enhance the removal efficiency of TN and NH 4 + –N from 25.9% to 50.3%, and from 34.5% to 60.1%, respectively. Concomitant increases in the number of microbial communities and the proportion of nitrifying bacteria were also identified by the most prob- able number (MPN) method. PCR–DGGE profiles revealed that the bacterial community could be success- fully enriched and the ammonia-oxidizing bacteria communities were shown predominant by the species of Nitrosomonas. The biological contact oxidation ditch (BCOD) system augmented with specialized bac- teria can be a viable alternative for treating polluted stream water to achieve improved nitrogen removal. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Bioaugmentation is the introduction of indigenous, allochtho- nous, or genetically modified organisms into a microbial commu- nity of polluted hazardous waste sites or bioreactors in order to accelerate the removal and biodegradation of undesired pollutants (Odokuma and Dickson, 2003; Fantroussi and Agathos, 2005). Bioaugmentation has been used as a treatment strategy for not only bioremediation of contaminated soils (D’Annibale et al., 2005; Hamdi et al., 2007) but also improvements of the activated sludge process (McLaughlin et al., 2006), as well as enhanced treat- ment of polluted solid and water areas (Top et al., 2002; Mohan et al., 2005). Despite a long cultural history of bioaugmentation in laboratory-scale projects (Friis et al., 2006; Hu et al., 2008; Semprini et al., 2007), attempts to scientifically carry out many of these processes have only recently been addressed such as in a full-scale biological treatment process with genuine process var- iability (Ma et al., 2009; Park et al., 2008). Nitrogen removal from wastewater with bioaugmentation in various bioreactors has been reported (Ahmad et al., 2008; Salem et al., 2004; Jun et al., 2004) and bioaugmentation has been used in such projects as shortening the start-up of a reactor, thus enhancing reactor performance, protecting existing microbial communities against adverse effects, accelerating the onset of degradation, and compensating for organ- ic or hydraulic overloading. It is always desirable to cultivate the existing endogenous population (Bouchez et al., 2000) rather than to add a potential non-representative type of nitrifier. Despite the success of bioaug- mentation studies, there have been many unsuccessful experi- ments, which have been well detailed and reviewed (Bouchez et al., 2000; Vogel and Walter, 2001). Although the bioaugmenta- tion for the degradation of nitrogen has been widely described in the literatures, to date very few examples of successful bioaug- mentation of indigenous enrichment specialized bacteria with a biological contact oxidation ditch (BCOD) for the treatment of nitrogen-rich stream water have been reported. Moreover, the engineering and economic applications have also limited the pop- ularization and application of bioaugmentation (Bouchez et al., 2000; Park et al., 2008). Located within Shenzhen of China, Buji stream represents a typ- ical polluted urban stream, due to the arbitrary discharge of muni- cipal wastewater. The deficiency of nitrifying bacteria made nitrification the limiting factor that impacted the nitrogen cycle of river water (Jiao et al., 2009). The aim of this study was to eval- uate the process-enhanced bioremediation of nitrogen-rich stream water by bioaugmentation with indigenous enrichment nitrifying bacteria, which confers a degradation capacity for nitrified nitrogen (nitrate/nitrite), and to discuss the diversity and numbers of microbial communities in water and AquaMats carriers in a 0960-8524/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2010.09.061 ⇑ Corresponding author. Tel.: +86 451 86283017; fax: +86 451 86282100. E-mail address: qlzhao@hit.edu.cn (Q. Zhao). Bioresource Technology 102 (2011) 990–995 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech