Enhanced short-cut nitrification in an airlift reactor by CaCO3 attachment on biomass under high bicarbonate condition

Abstract

The short-cut nitrification (SCN) performance of an airlift reactor (ALR) was investigated under increasing bicarbonate condition. The sequential increase of bicarbonate from 2.5 to 7.0 g/L accelerated the nitrite accumulation and improved the NAP to 99 %. With the increase of bicarbonate dose to 11 g/L, the ammonium removal efficiency and the ammonium removal rate (ARR) were improved to 95.1 % and 0.57 kg/m(3)/day, respectively. However, the elevation of bicarbonate concentration from 11.0 to 14.0 g/L gradually depreciated the nitrite accumulation percentage to 62.5 %. Then, the reactor was operated in increasing ammonium strategy to increase the nitrogen loading rate (NLR) to 1.1 kg/m(3)/day under 700 mg/L influent ammonium concentration. The ARR and nitrite production rate were elevated to 1.1 and 0.9 kg/m(3)/day, respectively. The SCN performance was improved to 1.8 kg/m(3)/day (NLR) by the subsequent progressive shortening of HRT to 4.8 h at ammonium concentration of 350 mg/L, which was 1.6 times higher than that of the increasing ammonium strategy. Chemical analysis with EDS, FTIR and XRD confirmed the presence of CaCO3 precipitates on biomass surface during the long-term operation under high bicarbonate conditions. The attachment of precipitates to the SCN sludge helped to improve the biomass settleability and finally enhanced the SCN performance of the ALR.

Failure Mechanism of the Corrugated Medium under Simulated Cold Chain Logistics

“…This phenomenon is attributed to the breakage of the HBs and crystalline regions of the fibers when water is frozen, thereby reducing the crystallinity and strength of the cellulose fibers . This observation is consistent with previous findings, which suggested that the lower strength of the HBs between adjacent cellulose chains loosens the cellulose structure and lowers the crystallinity of a material, thereby decreasing its mechanical properties. , …”

“…Figure presents the crystallinity of S C , S F , and S D obtained through XRD. The signals at 29, 36, 39, 47.5, and 48.5° are diffraction peaks of the calcite-type CaCO 3 fillers . The peaks at 15.4, 16.6, and 22.5° correspond to the crystalline regions of the cellulose fibers .…”

“…A high crystallinity indicates superior mechanical properties of the material. 40 41 The peaks at 15.4, 16.6, and 22.5°correspond to the crystalline regions of the cellulose fibers. 42 The crystallinity of samples S C , S F , and S D calculated using eq 2 is 79.32, 78.94, and 75.85%, respectively.…”

“…43 This observation is consistent with previous findings, which suggested that the lower strength of the HBs between adjacent cellulose chains loosens the cellulose structure and lowers the crystallinity of a material, thereby decreasing its mechanical properties. 41,44 3.5. DP Analysis.…”

The Response of Biogas Production and Methanogenic Community to the Variation of Intermediate Vfas Produced During the Anaerobic Digestionof Food Waste

“…During anaerobic digestion process, high F/I easily lead to VFAs inhibition, which usually effects the variation of methanogenic community structure in the bioreactor [24]. Therefore, the effects of intermediate VFAs produced by the increasing of F/I on the methanogenic community structure were analyzed at the end of each stage used the 16S rRNA high throughput sequencing technique.…”