Fe 3 O 4 nanoparticles (FNP) were implemented in two-stage anaerobic digestion to enhance the biogas production and waste sludge reduction in this study. The degradation and transformation of extracellular polymeric substances (EPS) and dissolved organic matters (DOM) under optimal FNP concentration during two-stage anaerobic process with heat pretreated waste sludge was investigated by analyzing the changes of soluble chemical oxygen demand (SCOD), carbohydrate and protein in EPS and DOM. FNP addition significantly enhanced volatile fatty acids (VFAs) production. The optimal dosage of FNP was 100 mg/L yielded 11.9 ml H 2 /g VS hydrogen and 109.8 ml CH 4 /g VS methane, which increased by 15.1% of hydrogen yield and 58.7% of methane yield compared with that of control. The maximum volatile suspended solids (VS) reduction was 46.9% with the addition of 100 mg/L FNP compared with that of control (34.3%). NH 4 + -N production was inhibited with 20, 50, and 100 mg/L FNP addition comparing with control.
Peng Wang,Chen Zhu,Yingji Gao,Zhonghua Cai,Ye ye,Yi Tao
Nitrate-driven sulfide oxidation has been proven to be a cost-effective approach for controlling sediment odor. However, injecting liquid nitrate (LN) directly into sediment carries ecological risks of nitrate escape and release of pollutants into overlying water. In this study, slow-release nitrate granules (GN) were prepared and applied in a continuous flow reactor to assess the differences between GN and LN in sediment remediation and control of this ecological risk. The results showed that the GN slowly released calcium nitrate, resulting in a decrease in acid volatile sulfide (AVS) from an initial 1328 ± 42.7 mg/kg to 490 ± 341 and 212 ± 32.8 mg/kg in the upper (U) and deeper (D) layers of the sediment, respectively. No significant decrease in AVS concentrations was observed in the LN treatments. Compared with LN-D and -U, the NH 4 + -N production and PO 4 3- -P release doses were reduced by 29.5% and 52.0% for GN-D and 41.2% and 37.8% for GN-U, respectively. Taxonomic analysis showed that sulfide-driven denitrifiers such as Thiobacillus , Rhodanobacter , Sulfurimonas , and Pseudomonas became dominant in the GN treatments, which were 2.8–6.7, 27.0–201.8, 1.5–3.0, and 3.0–496 times that of the LN treatments, respectively. The abundance of sulfur oxidation genes (e.g., sat and aprB ) and denitrifying genes (e.g., nirS and nosZ ) were also upregulated to higher levels by GN. Moreover, the genes (e.g., nrfA ) responsible for the isomerization of nitrate into ammonium were down-regulated by GN. The results showed that the slow-released calcium nitrate should be a promising way for in-situ remediation of sulfide-rich sediment.
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