The effect of carrier addition on Anammox start-up and microbial community: a review

The Anaerobic Ammonia Oxidation (Anammox) wastewater treatment process has attracted significant attention ever since its discovery in the Netherlands in the 1990 ' s. This has mostly been due to the potential cost-effectiveness associated with the process in large scale application. However, the application of the Anammox process on an industrial-scale has been curtailed mainly due to the long start-up time of the Anammox bacteria. In order to ensure the feasibility of industrial-scale Anammox application, researchers have employed various means; experimenting with different reactor types, membrane types, as well as the usage of chemicals such as hydrazine, acyl-homoserinelactones (AHL), etc. Most recently however, more attention has been directed towards the addition of biomass carriers such as biochar, zeolites, sponges, non-woven membrane etc. for the optimization of the Anammox process. This article provides an up-to-date overview of the various carriers (Non-woven fabric, Biochar, Down-flow hanging sponge, Zeolite, Zero-violent iron, Polyethylene glycol gel, Activated-carbon, Polyethylene sponge, etc.) that have so far been used to better the performance of the Anammox process. It also focuses on the effect of these biomass carrier additions on the microbial growth and community structure. Understanding the metabolomics of microorganisms in carrier-amended media promises to enhance our knowledge of carriers' influence on the microbial community structure. Generally, the metabolic effects of carrier-amendment on microbial growth and community are largely uninvestigated. Future researches focusing on this area could tremendously improve our comprehension of the inner-workings of the carrier amended Anammox set-up.