Study on Nitrogen Recovery from Nutrient-Rich Waste by ADCSTR System

Abstract

The landfill sites in Vietnam are struggling to carry huge amounts of organic waste every day. While the domestic demand of using organic fertilizers for clean agriculture is increasing, these organic materials are disposed in a wasteful way. This study indicated that the nitrogen (N) concentration of the waste that include septic tank sludge (STS), food waste (FW) and sludge from seafood waste water treatment plant (SFS) is quite high by 965 mg/L, 34,314 mg/L and 1,756 mg/L. In this study, an Anaerobic Digester_Continuously Stirred Tank Reaction (AD <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CSTR</sub> ) system was established to recover the N from these wastes. The AD <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CSTR</sub> was made of 5 mm thick tempered glass, with the dimension of the tank is H x D x R = 1,000 mm x 300 mm x 300 mm. The C/N ratio used for the AD <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CSTR</sub> was 25, which was identified by pre-testing seven small AD systems with different C/N ratios. The result revealed that after 50 d of anaerobic digestion, the Carbon (C) and Nitrogen (N) concentrations of liquid product was 9,628.3 mg/L and 648.5 mg/L, and the carbon to nitrogen ratio (C/N) was 11.35 as well, equivalent to 78.2 % of recovering efficiency. This study also indicated the potential to recover nutrition, produce organic fertilizer from recycling the STS, FW and SFS in Vietnam, significantly contribute to reducing waste to the disposals.