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AbstractThis study aims to investigate the diagnosis of acidification and efficient recovery of a laboratory-scale anaerobic sequencing batch reactor (ASBR) which treats synthetic glucose wastewater under mesophilic conditions (35°C). The diagnosis of the ASBR showed that acidification occurred on the seventh day after adding 20 mmol/L of sodium 2-bromoethanesulfonate into the reactor. A three-step recovery strategy was employed to recover the acidified reactor efficiently and to study its restoration process. Results indicated that the acidified ASBR can be revived in approximately 50 d. The specific methanogenic activities of the sludge, which were based on the substrate of acetate, propionate, and butyrate, were restored at 0.85, 0.67, and 0.51 (gCOD-CH4)/(gVSS∙d), respectively. The fluorescent observation images revealed large amounts of Methanosarcina-like and rod-shaped methanogens distributed in the sludge flocs after reactor restoration, thus ensuring that the fermentative, acidogenic, and methanogenic processes proceeded effectively in the anaerobic system.

This study aims to investigate the diagnosis of acidification and efficient recovery of a laboratory-scale anaerobic sequencing batch reactor (ASBR) which treats synthetic glucose wastewater under mesophilic conditions (35°C). The diagnosis of the ASBR showed that acidification occurred on the seventh day after adding 20 mmol/L of sodium 2-bromoethanesulfonate into the reactor. A three-step recovery strategy was employed to recover the acidified reactor efficiently and to study its restoration process. Results indicated that the acidified ASBR can be revived in approximately 50 d. The specific methanogenic activities of the sludge, which were based on the substrate of acetate, propionate, and butyrate, were restored at 0.85, 0.67, and 0.51 (gCOD-CH4)/(gVSS∙d), respectively. The fluorescent observation images revealed large amounts of Methanosarcina-like and rod-shaped methanogens distributed in the sludge flocs after reactor restoration, thus ensuring that the fermentative, acidogenic, and methanogenic processes proceeded effectively in the anaerobic system.

AbstractThe anaerobic sludge granulation was studied in two laboratory-scale continuous-flow stirred tank reactors (CSTRs), which treating synthetic glucose wastewaters under a mesophilic constant temperature of 35 ± 1°C. Different stirring strategies were employed in the two CSTRs. Magnetic stirring at a rotation speed of 140 rpm was used in CSTR1 and axial continuous agitation at a speed of 90 rpm in CSTR2. It was observed that highly activated granular sludge formed in CSTR2, but flocculent sludge still remained in CSTR1 after about 45 days’ cultivation. Liquid circulation analysis of the two stirring modes displayed that the overall circulation in CSTR2 was more uniform. Furthermore, calculation results proved that the hydraulic shear force produced in CSTR2 was more suitable for granules formation than it in CSTR1, and granules did form in the CSTR2. Therefore, it could be concluded that in the laboratory-scale CSTR, stirring strategy played a key role in sludge granulation. On the other hand, scanning electron microscope images of granular sludge displayed that filamentous bacterial dominated in the outer layer and bacilli surrounded by lots of extracellular polymeric substances in the inner layer. Both of these are beneficial to promote the granules formation and maintenance.

The anaerobic sludge granulation was studied in two laboratory-scale continuous-flow stirred tank reactors (CSTRs), which treating synthetic glucose wastewaters under a mesophilic constant temperature of 35 ± 1°C. Different stirring strategies were employed in the two CSTRs. Magnetic stirring at a rotation speed of 140 rpm was used in CSTR1 and axial continuous agitation at a speed of 90 rpm in CSTR2. It was observed that highly activated granular sludge formed in CSTR2, but flocculent sludge still remained in CSTR1 after about 45 days’ cultivation. Liquid circulation analysis of the two stirring modes displayed that the overall circulation in CSTR2 was more uniform. Furthermore, calculation results proved that the hydraulic shear force produced in CSTR2 was more suitable for granules formation than it in CSTR1, and granules did form in the CSTR2. Therefore, it could be concluded that in the laboratory-scale CSTR, stirring strategy played a key role in sludge granulation. On the other hand, scanning electron microscope images of granular sludge displayed that filamentous bacterial dominated in the outer layer and bacilli surrounded by lots of extracellular polymeric substances in the inner layer. Both of these are beneficial to promote the granules formation and maintenance.

The volume ratio of anaerobic/anoxic/aerobic was an important factor for the removal of nitrogen and phosphorus in the A2/O process. A pilot plant of A2/O process was built in Xi’an to do the research about the influence on nitrogen and phosphorus removal when the volume ratio of anaerobic/anoxic/aerobic was changed. When the HRT was 10.1h and the volume rate of anaerobic/anoxic/aerobic was 1/1.7/2.4, the removal rate of COD didn’t raise substantially than that of normal volume ratio A2/O process, the removal rate average value of TN and phosphorus were 61.5% and 85.4% respectively. On this condition, the HRT in aerobic zone shorted to 4.7h, energy was saved about 33.8% in comparing with that of conventional volume ratio A2/O process.

Enhancing nitrification from municipal wastewater by bioaugmentation was investigated in a pilot plant operated in A2/O process. Reject water was used to cultivate nitrifier in O/A process (side stream), and the exceed sludge in side stream was used to bioaugmentation. The experimental results showed that bioaugmentation was very effective for enhancing nitrification. After nitrifier bioaugmentation, the NH4+-N removal rate was improved more than 30% in main stream. And AUR and NUR of the activated sludge increased from 2.61 mgNH4+-N /(gMLSS•h) and 2.38 mgNO2--N/(gMLSS•h) to 5.32 mgNH4+-N /(gMLSS•h) and 3.81 mgNO2--N/(gMLSS•h), which was as 2.04 times and 1.60 times as those of before bioaugmentation in main stream respectively.

This paper reported the study of the photocatalytic activity of immobilized Fe3+ doped TiO2 on glass fibre yarn. A dip-coating technique fixing catalyst onto the support surface was applied to get the TiO2/Fe3+ coated filler. A photo reactor consists of a cylindrical quartz tube and filler with the immobilized catalyst was applied in the study. The photocatalytic activity was determined by the degradation of phenol in water (10 mg L-1). Results suggested that the fibre glass coated TiO2/Fe3+ photocatalysis filler has very excellent performances in repeat using and the supported TiO2 was very stable in photocatalysis reaction.

In order to study the differences of dissolved organic matter (DOM) characteristics between the secondary effluent and the surface water, ultrafiltration (UF) was combined with three-dimensional excitation-emission matrix (EEM) spectroscopy to investigate the fluorescence characteristics of total DOM and different molecular weight fractions of them. Moreover, the DOM removal characteristics by coagulation were analyzed also under the respective optimal dosage of coagulant (PAC). The results showed that: DOM of secondary effluent contained four notable fluorescence peaks: humic acid-, fulvic acid-, aromatic protein- and soluble microbial product-like fluorophores, which were more than surface water. Coagulation was easy to remove macromolecules as humus, but the removal efficiency was not high enough for the relative small molecules as protein and microbial products. Fluorescence index (FI) indicated that secondary effluent after biotreatment were mainly from microbial sources. The correlation relationship between the humus-, protein-like fluorescence intensity and UV254 are strong in secondary effluent.