Synergy of N-(3-oxohexanoyl)-L-homoserine lactone and tryptophan-like outer extracellular substances in granular sludge dominated by aerobic ammonia-oxidizing bacteria.

Nitrogen removal via nitrite is an energy-saving method for high-strength ammonia wastewater treatment. A better understanding of the formation of granular sludge dominated by aerobic ammonia-oxidizing bacteria (AerAOB) could facilitate the improved use of rapid sludge granulation for nitritation. In this study, AerAOB-dominated activated sludge (NAS) and granular sludge (NGS) produced different N-scyl-homoserine lactones (AHLs). N-(3-oxohexanoyl)-L-homoserinelactone (OHHL), only released from NGS, was shown to accelerate sludge aggregation by increasing the biomass growth rate, microbial activity, extracellular protein, and AerAOB biomass. For both NAS and NGS, sludge cells were glued together by inner extracellular polymeric substances (EPSs) with similar components to form microcolony. Different from the characterized negative effect of NAS's outer-EPS on cell adhesion, the outer-EPS of NGS played a positive role in the attached growth of AerAOB-dominated sludge and contained more tryptophan-like substances. More interesting, OHHL enhanced the yields of tryptophan-like substances after mixing with the outer-EPS of NGS, enhancing cell adhesion. In a word, OHHL and more tryptophan-like substances were produced in the process of granulation under the selective sludge discharge condition, which was proved to be able to accelerate NAS granulation. Therefore, the sludge granulation process for nitritation can be improved by increasing the levels of OHHL and tryptophan in the initial startup stage. The appropriate engineering strategy should be further studied to facilitate the actual application of granular sludge for nitrogen removal on a large scale.

Effect of Endometrial Stem Cell-derived Cytokine Cocktail on a Mouse Model of Myocardial Reperfusion Injury.

Objective To study the effect of endometrial stem cells (EnSCs) derived cytokine cocktail (EdCC) on myocardial ischemic reperfusion injury (I/R) in a mouse model. Methods EdCC was concentrated from the culture medium of EnSCs with Millipore ultra-filtration technology and was administrated to a myocardial I/R mouse models through tail vein injection. The infarct area was determined by TTC/Evans Blue staining. The apoptotic cells were counted by TUNEL assay and the protein level of cleaved caspase 3 was evaluated by Western blotting. Results The EdCC extraction efficiency was (222.4±29.3) Μg/10(6) cells in every 24 h,but the protein gradually degraded under-80 ℃ storage. As compared with I/R group,100 Μg fresh EdCC decreased infarct area (P=0.001),reduced apoptotic nuclei in the infarct border (P=0.019),and inhibited cleaved caspase 3 expression (P=0.002). Increasing EdCC dosage did not further reduce the infarct area. The myocardial protective effect of EdCC diminished after 90 days' storage under-80 ℃. Conclusion EdCC reduces myocardial I/R injury through protecting cardiomyocytes from apoptosis within 30 days storage under-80 ℃.

[Decision-making Analysis of Excess Sludge Pretreatment for Struvite Recovery Based on AHP-PROMETHEE â ¡ Method].

Phosphorus is a non-renewable resource. The recovery of phosphorus from excess sludge by the struvite precipitation process has been applied on a full-scale. However, different sludge pretreatment methods have been used to release carbon, nitrogen, and phosphate from excess sludge, which could affect the subsequent struvite precipitation process. In this study, the decision-level analytical structure of the 3-layer and 6-index was constructed to evaluate the effects of six excess sludge treatment processes on struvite recovery. According to the preference ranking organization method for the enrichment of evaluations Ⅱ (PROMETHEEⅡ) decision-making analysis, enzymatic hydrolysis or enzymatic hydrolysis-anaerobic fermentation was the better sludge treatment choice for struvite recovery under the "product quality" priority case, while thermal hydrolysis or thermal hydrolysis-anaerobic fermentation could be better under the "time and economy" priority case. This study provides a recommendation for the selection and design of excess sludge treatment for struvite recovery.

Microbial population dynamics during aerobic sludge granulation at different organic loading rates.

Laboratory experiments were carried out to investigate the evolution of the bacterial community during aerobic sludge granulation. The experiments were conducted in three 2.4L sequencing batch reactors (SBRs) that were seeded with activated sludge and fed with glucose-based synthetic wastewater. Three different influent organic concentrations were introduced into the three SBRs, R1, R2 and R3, resulting in chemical oxygen demand (COD) loading rates of 1.5 (R1), 3.0 (R2) and 4.5 (R3)kg/m(3)d, respectively. Changes in bacterial diversity throughout the granulation process were monitored and analysed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The experimental results demonstrate that glucose-fed aerobic granules could be formed without significant presence of filamentous bacteria. Granules formed at different loading rates had different morphology, structural properties and bacterial species. A higher loading rate resulted in faster formation of larger and loose granules, while a lower loading rate resulted in slower formation of smaller and more tightly packed granules. The biomass underwent a dynamic transformation in terms of bacterial species richness and dominance during the granulation process. The reactor with the highest substrate loading rate had the lowest species diversity, while the reactor with the lowest substrate loading rate had the highest species diversity. Different dominant species of beta- and gamma-Proteobacteria and Flavobacterium within the granule communities from the three different SBRs were confirmed by analysis of 16S rDNA sequences of the PCR products separated by DGGE. It is apparent that a few common bacterial species play an important role in the formation and growth of aerobic granules and help sustain the granular sludge structure in the bioreactors.

[Identification and Influence of Quorum Sensing on Anaerobic Ammonium Oxidation Process].

Anaerobic ammonium oxidation (ANAMMOX), an innovative nitrogen removal technology, has good prospects for applications. However, ANAMMOX bacteria grow slowly and are hardly accumulated in bioreactors. In this study, a UASB reactor inoculated with sludge from landfill leachate treatment plant was used for the start-up of ANAMMOX process. Besides, exogenous quorum sensing signals (DSF and AHL) were added to improve the adhesion of ANAMMOX sludge. The results showed that the UASB successfully started the ANAMMOX process within 150 days of operation. The total nitrogen removal rate reached 80% and the proportion of ANAMMOX bacteria rose to 20%. There was a low concentration of AHLs signal molecules in the ANAMMOX sludge. If the ß-position substituent group of AHL added was a carbonyl group (including 3-oxo-C6-HSL, 3-oxo-C8-HSL, 3-oxo-C10-HSL and 3-oxo-C12-HSL), the adhesion growth ability of the ANAMMOX sludge could be improved. In the case of dosing with AHL molecules without ß-position substituent groups, only C6-HSL and C12-HSL could promote the adhesion of ANAMMOX sludge. The additions of C8-HSL, C10-HSL and DSF all had negative effects on the adhesion of ANAMMOX sludge.

Cell adhesion, ammonia removal and granulation of autotrophic nitrifying sludge facilitated by N-acyl-homoserine lactones.

In this study, six N-acyl-homoserine lactone (AHL) molecules (C6-HSL, C8-HSL, C10-HSL, 3-oxo-C6-HSL, 3-oxo-C8-HSL and 3-oxo-C10-HSL) were each dosed into a bioreactor and seeded using autotrophic nitrifying sludge (ANS). The effects of the AHLs on cell adhesion, nitrification and sludge granulation were investigated. The results indicated that the efficiencies of cell adhesion and ammonia removal both had a close correlation with the side chain length and ß position substituent group of the AHLs. The best-performing AHL in terms of accelerating bacterial attached-growth was 3-oxo-C6-HSL, whereas C6-HSL outperformed the others in terms of the ammonia degradation rate. The addition of 3-oxo-C6-HSL or C6-HSL increased the biomass growth rate, microbial activity, extracellular proteins and nitrifying bacteria, which can accelerate the formation of nitrifying granules. Consequently, selecting AHL molecules that could improve bacteria in attached-growth mode and nitrification efficiency simultaneously will most likely facilitate the rapid granulation of nitrifying sludge.

Fate of aerobic bacterial granules with fungal contamination under different organic loading conditions.

Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. However, the instability of aerobic granules caused by fungal growth is still one of the main problems encountered in granular bioreactors. In this study, laboratory experiments were conducted to investigate the fate and transformation of aerobic granules under different organic loading conditions. Bacterial granules (2-3mm) in a poor condition with fungi-like black filamentous growth were seeded into two 1L batch reactors. After more than 100d of cultivation, the small seed granules in the two reactors had grown into two different types of large granules (>20mm) with different and unique morphological features. In reactor R1 with a high organic loading rate of 2.0g COD L(-1)d(-1), the black filaments mostly disappeared from the granules, and the dominance of rod-shaped bacteria was recovered. In contrast, at a low loading of 0.5g COD L(-1)d(-1) in reactor R2, the filaments eventually became dominant in the black fungal granules. The bacteria in R1 granules had a unique web-like structure with large pores of a few hundred microm in size, which would allow for effective substrate and oxygen transport into the interior of the granules. DNA-based molecular analysis indicated the evolution of the bacterial population in R1 and that of the eukaryal community in R2. The experimental results suggest that a high loading rate can be an effective means of helping to control fungal bloom, recover bacterial domination and restore the stability of aerobic granules that suffer from fungal contamination.

Selective sludge discharge as the determining factor in SBR aerobic granulation: numerical modelling and experimental verification.

Numerical simulation and laboratory experiments were conducted to investigate the determining factor and the underlying mechanism in aerobic sludge granulation in a sequencing batch reactor (SBR). In the numerical simulation, a sectional approach was used to develop a model to describe the biomass dynamics during the granulation process. The growth of different classes of the SBR sludge with different substrate uptake rates and different sludge discharge ratios was simulated. The results indicate that the selective discharge of slow-settling sludge flocs is the key determining factor for granulation. In the laboratory study, experiments were conducted with two identical 2.4-L SBRs, R1 and R2, using different sludge discharge methods - the selective discharge of slow-settling sludge flocs for R1, and mixed, unselective sludge discharge for R2. The SBRs were fed with glucose-based synthetic wastewater at a chemical oxygen demand (COD) loading rate of 1.5 kg/m(3)-d. The evolution of the microbial community during the experimental process was monitored using the molecular techniques of polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE) and clone library analysis. Sludge granulation was achieved in less than three weeks in R1, whereas the sludge in R2 remained in the form of flocs. However, some bacterial species had a significant presence in both the R1 granules and the R2 flocs. The results suggest that aerobic granulation may not require the dominance of any particular species. Small and loose sludge flocs were found to have an advantage over larger and dense granules in substrate uptake. Thus, discharge of loose flocs would remove these competitors from the system and makes the substrate more available for uptake and utilisation by biomass in the attached-growth form, resulting in sludge granulation.

[Efficiency and characteristic of biological activated carbon fluidized bed for oil-field wastewater treatment].

In order to find method to improve biodegradation of oil-field wastewater, the biological activated carbon fluidized bed (BAC-FB) process for oil-field wastewater treatment in aerobic condition is studied. The results show that the process demonstrated highest removal rate with hull activated carbon (AC) as carrier and carrier concentration of 15%. The optimized HRT of the process is 5 h. COD, UV254, UV410, organic acid and organic compounds (GC/MS) were detected as the index to indicate the efficiency of oil-field wastewater treatment by this process. The results show that the removal rate of COD range from 25% to 45%. The average removal rate of UV254, UV410, organic acid is 85.9%, 73.6%, 51.5% respectively. The removal rate of oil content is almost 100%. However, alkane is difficult to remove from wastewater. Furthermore, high concentration inorganic materials such as calcium, chlorine were found to accumulate on activated carbon during treatment process, which is harm to adsorption and biodegradation of organic compound. High temperature of oil-field wastewater is also one of factors to inhibit adsorption and biodegradation of organic compound.

[Characteristic of the removal of 2,4-dichlorophenol by biological activated carbon].

The adsorption characteristics and kinetics of 2,4-Dichlorophenol (2,4-DCP) by biological activated carbon (BAC) was studied through contrast experiments with conventional activated sludge alone or quartz as the carrier. The advantage and disadvantage of removing 2,4-DCP using BAC and the mechanism of this process were investigated. The results show that the method of removing 2,4-DCP by BAC is applicable in practices, and the process of BAC demonstrates high removal rate than the process of suspended activated sludge and biofilm with quartz as the carrier. In addition, the BAC process showed high resistance to shock loadings, therefore, it is suitable to be utilized at high organic loading and under long-term operation. In BAC-system, activated carbon could not only adsorb 2,4-DCP but also oxidized 2,4-DCP.