Nitrification efficiency in biofilters under various bioloading methods for closed-cycle water supply plants

Abstract

The rapid development of world aquaculture requires the development of modern technological solutions to maintain stable water quality in industrial aquaculture systems. One of the most effective technologies is recirculation aquaculture system (RAS) installations, which allow significantly reducing the cost of natural and energy resources per kilogram of grown products and ensuring full control of chemical and physical parameters of water. One of the most important elements of the RAS is a biological filter. In this work, a study of the functioning of various types of biological filter designs used in RAS was carried out, namely: biofilters with fixed bioloading, biological filters with moving bioloading, and drip biofilters. The influence of hydraulic load, water temperature, biological loading area and the influence of contact time on the efficiency of the nitrification process in the RAS were studied. The ammonia concentration was artificially raised from 1 to 5 mg/l. At the same time, the hydraulic load was increased from 10 to 80 l/min per 1 m2 of the bioloading surface area. The results of the study showed that biological filters with moving bioloading showed the highest water filtration efficiency – 95% at the minimum water velocity and ammonia concentration. It has been found that increasing the surface area of biological loading and optimizing hydraulic loading can significantly improve the quality of biological filtration. The integral efficiency coefficient (ICE) of nitrification in the biofilter with a moving bioloading was 91.25, which is 6.43% higher than the ICE of the biofilter with a fixed bioloading and 11.91% higher than the ICE of the trickling biofilter. The results of scientific research can be used in aquaculture farms to improve the nitrification process in the RAS system.