Packed bed biofilm reactor for high-rate, robust and efficient nitrification in recirculating aquaculture system: A preliminary investigation

Abstract

Recirculating aquaculture system (RAS) – wherein water gets treated and recirculated – is an environment-friendly, sustainable, and highly desirable method for the cultivation of aquatic organisms. Attaining compact, robust, and efficient reactor for ammonia removal by nitrification is the bottleneck in RAS. Packed bed biofilm reactors (PBBRs) are among the most compact, known to be capable of offering efficient and robust nitrification with rates of about 1 kg N-NH4+∙m−3 d−1. Attempts to realise high-rate and efficient PBBRs for RAS are scanty and without much success. Existing literature have mostly achieved nitrification rates <100 g m−3 d−1 only. This preliminary investigation demonstrates successful application of PBBR accomplishing high-rate and efficient nitrification in a simulated lab-scale RAS. Operated over a period of about 120 days and ammonia loading rates ranging from 200 to 800 g N-NH4+∙m−3 d−1, the PBBR consistently achieved more than 99.7% ammonia removal, maintaining N-NH4+ concentrations of 0.1–1.1 mg/L in the culture tank. The study presents the potential to achieve compact, robust, and efficient nitrification process in RAS using PBBRs.