Total suspended solids and their impact in a biofloc system: Current and potentially new management strategies

Heterotrophic bacterial activity generates a load of total suspended solids (TSS) in biofloc systems (BF). This accumulation affects animal health and product quality in terms of the gills blocked function and flesh off-flavor, but TSS elimination causes a sudden change in microbial composition and nutrients concentration, leading to a decreased nitrifying bacterial load and facilitating pathogenic bacterial growth. The accumulated or drained TSS from BF system results in an increased of pathogenic bacterial abundance, in this review, we suggest novel management strategies to manipulate the TSS level by manipulating the heterotrophic and nitrifying bacterial activities. Hybrid activity between heterotrophic and nitrifying bacteria may decrease the bacterial intensity and carbon source supplement in BF. Based on this complex interaction we suggested novel management strategies of nitrifying activity induction and heterotrophic activity manipulation. Nutrient availability (Ca+2 and alkalinity as carbon sources, for example lime), biofilm induction (homoserine lactone supplementation as a quorum sensing agent), and environmental conditions (temperature, and a complex carbon source as a substrate carrier) may induce nitrifying bacterial activity. Decreasing C/N ratio may induce a low C/N dependent heterotrophic activity, whereas increased algal abundance would provide a photosynthetic carbon for heterotrophic activity and would recycle the nitrogenous compounds (NO3). The hybrid bacterial activities may result in an increased productivity, zero mortality, stable water quality, longer culture capacity, and a free off-flavor product.