Denitrification is a crucial step in maintaining water quality in Recirculating Aquaculture Systems. Conventional liquid carbon sources for denitrification create issues in RAS due to overdose hazard and the requirement of separate loop operation. Our study deals with the development of a unique approach which employs Poly(3-hydroxybutyrate-co-3-valerate) (PHBV)-Biomass composite pellets as a solid carbon source for denitrification in a recirculating aquaculture system. The study investigates the potential of combining PHBV with four biomass materials (saw dust, switch grass, sugarcane bagasse, and rice husk) to make cost-effective and durable pellets. Composite pellets were made with different ratios of PHBV to Biomass (50-90%) by using both a Heated Pellet Pressing Die Set with hydraulic press and a pellet mill. Pellets are submerged for 24 hours for testing physical cohesiveness. The blends pellets passing the physical cohesiveness test are then subjected to comprehensive physical and mechanical evaluation, including wet abrasion resistance in fluidized bed filters.
Based on mechanical properties, basic cohesiveness and wet abrasion tests, a set of finalist pellets is selected. Composite pellets with the best pellet properties and lowest PHBV content are used in denitrification testing experiments. Denitrification experiments were conducted using PVC bioreactor column filled with the selected bio-pellets. The nitrate reduction rate, pellets consumption rate and COD accumulation are quantified. Cost analysis of the selected blends will also be discussed.