Huifeng Lu

The structure, density and settlability of anammox granular sludge in high-rate reactors

Microscopic observation and settling test were carried out to investigate the structure, density and settlability of anammox granules taken from a high-rate upflow anaerobic sludge blanket (UASB) reactor. The results showed that the anammox granules were irregular in shape and uneven on surface, and their structure included granule, subunit, microbial cell cluster and single cell. The gas pockets were often observed in the anammox granules, and they originated from the obstruction of gas tunnel by extracellular polymer substances (EPSs) and the inflation of produced dinitrogen gas. The volume of gas pockets became larger with the increasing diameter of anammox granules, which led to the decreasing density and the floatation of anammox granules. The diameter of anammox granules should be controlled at less than 2.20mm to avoid the granule floatation. A hypothesized mechanism for the granulation and floatation of anammox biomass was proposed.

Physical characteristics and formation mechanism of denitrifying granular sludge in high-load reactor.

The physical characteristics of denitrifying granular sludge and their granulation mechanism were investigated in two denitrifying reactors (R1 and R2). The results showed that the denitrifying granular sludge was streamlined in shape with the aspect ratio (AR) of 0.62 ± 0.05, large in size with the diameter of 2.39 ± 0.05 mm, and fast in settlement with the average settling velocity (VS) of 126.36 ± 13.32 m/h at the nitrate loading rate (NLR) of 35.14 ± 0.38 kg/(m(3)d). The dominance of denitrifying granular sludge with good settleability was attributed to the enhanced growth of granular sludge by extracellular polymers (EPS) and the shaping of granular sludge by shear force.

Toxicity assessment of anaerobic digestion intermediates and antibiotics in pharmaceutical wastewater by luminescent bacterium.

In order to evaluate the effect of anaerobic digestion intermediates and antibiotics in pharmaceutical wastewaters on anaerobic digestion process, their acute toxicities were tested using the 15 min median inhibitory concentration (IC(50)) at pH 7.00 ± 0.05. The results showed that the IC(50) of ethanol, acetate, propionate and butyrate were 19.40, 20.71, 10.47 and 12.17 g L(-1) respectively, which suggested the toxicity descended in the order of propionate, butyrate, ethanol and acetate. The IC(50) of aureomycin, polymyxin and chloromycetin were 12.06, 6.24 and 429.90 mg L(-1) respectively, which indicated the toxicity descended in the order of polymyxin, aureomycin and chloromycetin. Using equitoxic ratio mixing method, the joint toxicities of five groups referred by A (four anaerobic digestion intermediates), B (four anaerobic digestion intermediates and aureomycin), C (four anaerobic digestion intermediates and polymyxin), D (four anaerobic digestion intermediates and chloromycetin) and E (four anaerobic digestion intermediates, aureomycin, polymyxin and chloromycetin) were investigated respectively. Their interactions were additive (A), synergistic (B), additive (C), synergistic (D) and synergistic (E). The investigation would lay a basis for the optimization of anaerobic biotechnology for pharmaceutical wastewater treatment.

Ecological characteristics of anaerobic ammonia oxidizing bacteria

Anaerobic ammonium oxidation (anammox) is the microbial conversion of ammonium and nitrite to dinitrogen gas. The functional microbes of anammox reaction are anammox bacteria, which were discovered in a wastewater treatment system for nitrogen removal. Anammox bacteria are prevalent in anoxic ecosystems and play an important role in both biological nitrogen cycle and nitrogen pollution control. In this paper, we reviewed the investigation on ecological characteristics of anammox bacteria, and tried to figure out their complicated intraspecies and interspecies relationships. As for intraspecies relationship, we focused on the quorum sensing system, a cell density-dependent phenomenon. As for interspecies relationship, we focused on the synergism and competition of anammox bacteria with other microorganisms for substrate and space. Finally, we discussed the great influence of environmental factors (e.g., dissolved oxygen, organic matters) on the constitution, structure and function of anammox bacteria community.

Effect of particle size on the performance of autotrophic nitrogen removal in the granular sludge bed reactor and microbiological mechanisms

The effect of particle size on the performance of autotrophic nitrogen removal in the granular sludge bed reactor (GSB-ANR) and microbiological mechanisms were investigated. The results indicated that performance of GSB-ANR process decreased gradually with the increase of the granular sludge size. Indeed small granules ranging between 0.5 and 0.9mm had a higher nitrogen removal capacity than large ones. The reasons of this effect were that (i) the aerobic ammonium oxidizing capacity of microorganisms was the bottle neck of nitrogen removal in GSB-ANR process, and the increase of aerobic ammonium oxidizing activity enhances nitrite production in nitrification and promotes subsequent nitrite consumption during anaerobic ammonia oxidation; (ii) the aerobic/anaerobic zone separation in granular sludge was the key factor affecting the aerobic ammonium oxidizing capacity of microorganisms. The small granules had a larger aerobic functional zone (75.1%) which was profitable for up-regulating the expression level of functional gene in aerobic ammonium oxidizing microorganisms.

Acute toxicity assessment of ANAMMOX substrates and antibiotics by luminescent bacteria test

Acute toxicities of anaerobic ammonia oxidation (ANAMMOX) substrates and four antibiotics from pharmaceutical wastewaters on ANAMMOX process were reported. Individual and joint acute toxicity assays were performed using 50% inhibitory concentration (IC50). Results showed that IC50 values and their 95% confidence interval of ammonium chloride (A), sodium nitrite (B), penicillin G-Na (C), polymyxin B sulfate (D), chloramphenicol (E) and kanamycin sulfate (F) were 2708.9 (2247.9-3169.9), 1475.4 (1269.9-1680.9), 5114.4 (4946.4-5282.4), 10.2 (1.8-18.6), 409.9 (333.7-486.1) and 5254.1 (3934.4-6573.8) mgL(-1) respectively, suggesting toxicities were in the order of D>E>B>A>C>F. Joint acute toxicities of bicomponent mixtures A and B, C and D, C and F, D and F were independent; D and E, E and F were additive while C and E were synergistic. Joint acute toxicities of multicomponent mixtures were synergistic or additive. Luminescent bacteria test is an easy and robust method for forecasting the feasibility of ANAMMOX process for pharmaceutical wastewater treatment.

Simultaneous ammonia and nitrate removal in an airlift reactor using poly(butylene succinate) as carbon source and biofilm carrier.

In this study, an airlift inner-loop sequencing batch reactor using poly(butylene succinate) as the biofilm carrier and carbon source was operated under an alternant aerobic/anoxic strategy for nitrogen removal in recirculating aquaculture system. The average TAN and nitrate removal rates of 47.35±15.62gNH4-Nm(-3)d(-1) and 0.64±0.14kgNO3-Nm(-3)d(-1) were achieved with no obvious nitrite accumulation (0.70±0.76mg/L) and the dissolved organic carbon in effluents was maintained at 148.38±39.06mg/L. Besides, the activities of dissimilatory nitrate reduction to ammonium and sulfate reduction activities were successfully inhibited. The proteome KEGG analysis illustrated that ammonia might be removed through heterotrophic nitrification, while the activities of nitrate and nitrite reductases were enhanced through aeration treatment. The microbial community analysis revealed that denitrifiers of Azoarcus and Simplicispira occupied the dominate abundance which accounted for the high nitrate removal performance. Overall, this study broadened our understanding of simultaneous nitrification and denitrification using biodegradable material as biofilm carrier.

Assessment of toxicity of volatile fatty acids to Photobacterium phosphoreum

The toxicity of four volatile fatty acids (VFAs) as anaerobic digestion (AD) intermediates was investigated at pH 7. Photobacterium phosphoreum T3 was used as an indicator organism. Binary, ternary and mixtures of AD intermediates were designated by letters A (acetic acid + propionic acid), B (acetic acid + butyric acid), C (acetic acid + ethanol), D (propionic acid + butyric acid), E (propionic acid + ethanol), F (butyric acid + ethanol), G (acetic acid + propionic acid + butyric acid), H (acetic acid + propionic acid + ethanol), I (acetic acid + butyric acid+ ethanol), J (propionic acid + butyric acid + ethanol) and K (acetic acid + propionic acid + butyric acid + ethanol) to assess the toxicity through equitoxic mixing ratio method. The IC50 values of acetic acid, propionic acid, butyric acid and ethanol were 9.812, 7.76, 6.717 and 17.33 g/L respectively, displaying toxicity order of: butyric acid > propionic acid > acetic acid > ethanol being additive in nature. The toxic effects of four VFAs could be designated as synergistic and one additive in nature.