was the addition of ZVI. This may explain the different microbialcommunities in the reactors, which we discuss in Section 3.4.
Table 1 gives the settling velocities of aerobic granules in R1 andR2 as 47.4 ± 4.86 m/h (R1) and 56.8 ± 3.4 m/h, respectively (n = 3).The settling velocity of aerobic granules in R2 was significantlyhigher than that in R1 (p < 0.05). The result was similar to that forthe SVI of aerobic granules in the two reactors. Other importantparameters of the physical characteristics of granules, such as spe-cific gravity, integrity coefficient, and moisture content, were betterin R2 than in R1. It is thus concluded that ZVI enhances the physicalcharacteristics of aerobic granules.In this research, ferrous iron ions enhance cell aggregation.Because of the reduction reaction of ZVI (Fe0− 2e–= Fe2+), the Fe2+concentration in R2 had a range 8–17 mg L−1during the study.According to DLVO theory, divalent metal ions reduce electricrepulsion and facilitate cell-to-cell interaction between bacte-ria. Fe2+dissolved from ZVI intensifies microbial agglomerationthrough charge neutralization and double-layer compression. Thus,the Fe2+dissolution from ZVI reduced the start-up time of aerobicgranulation.
3.3. EPS content and EEM spectra of EPSs
EPSs are metabolic products that accumulate on the surfacesof bacterial cells. EPSs play a key role in the process of aerobicgranulation [30]. They are mainly composed of polysaccharides,protein, DNA, and humic acid substances that surround cells andcreate a matrix [31]. The EPS contents in R1 (in 1 g SS) on day 85were 29.8 ± 1.7 mg PN, 47.9 ± 4.6 mg humic acid, and 19.6 ± 2.2 mgpolysaccharides (n = 3). The EPS content of each gram of the aero-bic granules in R2 (in 1 g SS) on day 85 increased to 36.7 ± 2.5 mgprotein, 50.4 ± 5.1 mg humic acid, and 21.7 ± 2.6 mg polysaccha-rides (n = 3). Compared with the case for R1, the production yieldof protein was significantly greater in R2 (p < 0.05). The increase
was the addition of ZVI. This may explain the different microbialcommunities in the reactors, which we discuss in Section 3.4.Table 1 gives the settling velocities of aerobic granules in R1 andR2 as 47.4 ± 4.86 m/h (R1) and 56.8 ± 3.4 m/h, respectively (n = 3).The settling velocity of aerobic granules in R2 was significantlyhigher than that in R1 (p < 0.05). The result was similar to that forthe SVI of aerobic granules in the two reactors. Other importantparameters of the physical characteristics of granules, such as spe-cific gravity, integrity coefficient, and moisture content, were betterin R2 than in R1. It is thus concluded that ZVI enhances the physicalcharacteristics of aerobic granules.In this research, ferrous iron ions enhance cell aggregation.Because of the reduction reaction of ZVI (Fe0− 2e–= Fe2+), the Fe2+concentration in R2 had a range 8–17 mg L−1during the study.According to DLVO theory, divalent metal ions reduce electricrepulsion and facilitate cell-to-cell interaction between bacte-ria. Fe2+dissolved from ZVI intensifies microbial agglomerationthrough charge neutralization and double-layer compression. Thus,the Fe2+dissolution from ZVI reduced the start-up time of aerobicgranulation.3.3. EPS content and EEM spectra of EPSsEPSs เป็นผลิตภัณฑ์เผาผลาญอาหารที่สะสมในเซลล์แบคทีเรีย surfacesof EPSs มีบทบาทสำคัญในกระบวนการ aerobicgranulation [30] ที่มีองค์ประกอบส่วนใหญ่ของแซ็ก โปรตีน ดีเอ็นเอ และสารกรดฮิวมิคที่ล้อมรอบเซลล์ andcreate เมทริกซ์ [31] EPS เนื้อหาใน R1 (ใน 1 g SS) ในวัน 85were ± 1.7 มิลลิกรัม PN 29.8, 47.9 ± 4.6 มิลลิกรัมกรดฮิวมิก และ mgpolysaccharides 19.6 ± 2.2 (n = 3) เนื้อหา EPS แต่ละกรัมของ aero bic เม็ดใน R2 (ใน 1 กรัม SS) วัน 85 เพิ่มขึ้น 36.7 ± 2.5 mgprotein, 50.4 ± 5.1 มิลลิกรัมกรดฮิวมิก และ 21.7 ± 2.6 มิลลิกรัม polysaccha-ขี่ (n = 3) เมื่อเทียบกับกรณี R1 โปรตีน yieldof ผลิตได้มากใน R2 (p < 0.05) การเพิ่มขึ้น
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