Aim:
We evaluated glycerol as an alternative carbon source to methanol and acetic acid in a Denitrification. Objectives included assessing denitrification performance, incomplete denitrification, user-friendliness, substrate efficiency, costs, and health and safety.
Materials and Methods:
Research was conducted in a commercial salmon RAS in Norway. Biofilters were supplemented with glycerol vs. acetic acid. Performance metrics included total dissolved nitrogen (TDN) removal, pH stability, and chemical oxygen demand (COD) consumption. Economic analysis compared costs per kilogram of TDN removed. Health and safety were assessed across hazard categories. Total gas pressure residual (TGP res) was evaluated as an indicator of denitrification performance.
Results:
Glycerol demonstrated effective denitrification, with similar or higher TDN removal. Glycerol maintained stable pH, enhancing bioreactor stability and allowing higher dosing without compromising user-friendliness. Complete glycerol consumption indicated efficient utilization. Glycerol was 1.5 times more cost-effective than acetic acid and received the highest health and safety scores. TDN removal correlated well with TGP res.
Discussion and Conclusions:
Glycerol is a suitable and advantageous carbon source for denitrification in land-based salmon RAS. Benefits include stable pH levels, complete COD consumption, superior cost efficiency, and reliable performance indication through TGP res. Glycerol’s high health and safety scores make it a preferred choice. Recommendations: 1. Use glycerol at concentrations below 80% to maintain low viscosity and a lower freezing point. 2. Monitor nitrite production and consider higher COD levels and extended hydraulic retention times if nitrite production persists. 3. Install sensors for detecting total dissolved gas pressure and dissolved oxygen levels. 4. Conduct periodic analysis of dissolved nitrogen species to refine performance calibration. This study highlights glycerol’s potential as a sustainable and efficient carbon source, encouraging its broader adoption in aquaculture systems.