Method for Rapid Labeling of Waste Sludge from a Food Factory with ¹⁵N-Glycine and Evaluation of N Use Using Komatsuna (Brassica rapa Var. perviridis)

Figure 1

The cylindrical tank used to prepare the labeled sludge with ¹⁵N-glycine. 50 L of wastewater from a bean curd factory was mixed with 1 L of active sludge and 3 g of ¹⁵N-glycine (98 atom% ¹⁵N) and aerated at 25 L·min⁻¹ from the bottom of the cylindrical tank, 72 cm h × 62 cm ϕ, at 25°C for 5 days. During the aeration, samples were collected and allowed to stand for 1 h for floc sedimentation, and the supernatant was recovered to estimate various parameters described in Section 2.4. Experiments without the addition of glycine were done several times. The mixing with cold glycine and with ¹⁵N-glycine was performed 3 times and 1 time, respectively.