Jump to Main Content
Aerobic bioconversion of aquaculture solid waste into liquid fertilizer: Effects of bioprocess parameters on kinetics of nitrogen mineralization
- Khiari, Zied, Kaluthota, Soba, Savidov, Nick
- Aquaculture 2019 v.500 pp. 492-499
- ammonification, ammonium, aquaculture farms, aquaponics, bioprocessing, bioreactors, biotransformation, fish, liquid fertilizers, livestock, mineralization, nitrates, nitrification, nitrifying bacteria, nitrogen, nutrients, operating costs, oxidation, pH, seafoods, solid wastes, temperature
- Aquaculture has experienced a burgeoning growth worldwide in the last decade resulting in nearly 50% of seafood originating from aquaculture farms. However, there are less studies on the utilization of the manure produced by aquatic organisms in comparison to warm-blooded livestock. Aquaponics offers more efficient utilization of nutrients and can reduce the operational costs in aquaculture. This paper presents the results of a study to identify the optimal settings to digest fish manure through a microbial-assisted aerobic bioprocess, using endogenous heterotrophic and nitrifying bacteria. The effects of pH (5.5, 6.0 and 6.5), temperature (30, 35 and 40 °C) and duration (1–30 days) on kinetics of nitrogen mineralization were investigated and compared to a control bioreactor (carried out without pH adjustment). The mineralization dynamics for all pH-controlled bioreactors revealed that only ammonification occurred. No nitrification was observed for all three-temperature conditions and throughout the entire bioprocessing period. The mineralization process in the control bioreactor, on the other hand, followed the typical non-inhibited nitrogen mineralization (i.e., release of ammonium followed by oxidation into nitrate). However, nitrate was only observed at temperatures <40 °C indicating a complete suppression of nitrification at higher temperatures. Analytical data and modeled parameters indicated that the bioprocessing of aquaculture solid waste for 15 days at 35 °C using either pH 6.0 or 6.5 maximized nitrogen bioconversion in the form of ammonium ions (NH4+). This study indicates the importance of temperature and pH optimization for more efficient processing of aquaculture solid waste such as fish manure.