Fermentation liquid production of food wastes as carbon source for denitrification: Laboratory and full-scale investigation

Nitrogen removal is often limited in municipal wastewater treatment due to the insufficiency of carbon source, and using food wastes fermentation liquid as carbon source could cut down the cost of operating and recycle food wastes. Food wastes fermentation liquid production and application as external carbon source were explored in the laboratory and full-scale system in this study. In the laboratory scale, lactic acid and VFAs were the main components of fermentation liquid, and the highest total chemical oxygen demand (TCOD) production was obtained with activated sludge as inoculum. The yield of TCOD was around 794.5 mg/g TSfed and NH4+-N was 3.5 mg/g TSfed. The denitrification rate with fermentation liquid was slightly lower than acetic acid and butyric acid, but higher than lactic acid and starch. In the fullscale investigation, the TCOD concentration in fermentation liquid was in the range of 6.9e12.8 g/L and the ratio of TCOD/inorganic nitrogen was 210.5-504.5:1. NO3--N removal increased from 52.1% to 94.2% after fermentation liquid addition, confirming the potentiality of food wastes fermentation liquid replace the commercial carbon source in wastewater treatment plants. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Food wastes fermentation liquid was investigated as an external carbon source in municipal wastewater treatment for nitrogen removal, showing potential to replace commercial carbon sources with improved nitrogen removal efficiency and reduced operating costs. The laboratory and full-scale experiments demonstrated the effectiveness of using fermentation liquid to enhance denitrification in wastewater treatment plants.