| Summary: | 碩士 === 崑山科技大學 === 環境工程研究所 === 103 === A kinetic model (incorporating intrinsic kinetics) and an empirical model (incorporating apparent kinetics) that can be used for simulating variations in nitrate residual concentration with different operating conditions in the upflow denitrification sludge bed (UDSB) reactor are formulated. Two UDSB reactors (reactors A and B; us = 0.5 m/h; operating temperature = 30℃) were also used to treat low-strength nitrate-containing wastewater. Reactors A and B were respectively fed with wastewater containing 20 and 40 mg NO3--N/L but with three different hydraulic retention time of 2.9, 5.7, 11.4 h and 5.7, 11.4, 22.8 h (i.e., volumetric loading rate = 0.168, 0.084, and 0.042 kg NO3--N/m3-d). Thus, not only the performance of UDSB reactors, granule characteristics, mass transfer, and reaction kinetics can be evaluated but the kinetic and empirical models can also be validated by experiments.
When reactors A and B were respectively maintained at the hydraulic retention time of 2.9–11.4 h and 5.7–22.8 h (volumetric loading rate = 0.168–0.042 kg NO3--N/m3-d), fairly good sludge granulation can be achieved with above 90% of mg NO3--N removal. The granule’s specific gravity and the microbial density of reactor A (1.06–1.1; 57500–73100 mg VSS/L) varied slightly with those of reactor B (1.09–1.1; 53400–60700 mg VSS/L). However, the average granule diameter of reactors A and B (0.66–0.35 mm ; 0.64–0.34 mm) increased with increasing volumetric loading rate.
From the batch experiments, the Monod intrinsic k (0.38–0.43 mg NO3--N/mg VSS-d) was larger than the apparent k' (0.32–0.36 mg NO3--N /mg VSS-d). The Monod intrinsic Ks (8–13 mg NO3--N/L) were smaller than the apparent K's (10–18 mg NO3--N/L). By using the validated kinetic model, the calculated mass transfer parameter 2, Bi and are 3.0–11.4, 1.0–1.7, and 0.26–0.42, respectively, disclosing that not only internal mass transfer resistance imposes an influencing role but the nitrate reduction rate also plays a fairly important role on the overall nitrate removal rate. The calculated NO3--N removal efficiencies using kinetic and empirical models are 6% deviated from the experimental results. The variations of the simulated results using kinetic and empirical models are within 5.5%.
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