Xiuping Yue

Evaluation of surfactants on waste activated sludge fermentation by pyrosequencing analysis

The effects of three widely-used surfactants on waste activated sludge (WAS) fermentation and microbial community structures were investigated. Rhamnolipid bio-surfactants (RL) showed more positive effects on WAS hydrolysis and acidification compared to chemosynthetic surfactants, such as sodium dodecylsulphate (SDS) and sodium dodecyl benzene sulfonate (SDBS). The highest SCOD and VFAs concentrations obtained with RL were 1.15-fold and 1.16-fold that of SDS, and up to 1.73 and 3.63 times higher than those obtained with SDBS. Pyrosequencing analysis showed that an evident reduction in bacterial diversity in surfactant-treated WAS. Moreover, acid-producing bacteria (such as Megasphaera and Oscillibacter), detected with RL, were (6.8% and 6.4% in proportion) more abundant than with SDS, and were rarely found in SDBS and the control. The results also revealed that RL allowed efficient hydrolysis enhancement and was favorable to functional microorganisms for further acidification during WAS fermentation.

Characterization of biocarbon-source recovery and microbial community shifts from waste activated sludge by conditioning with cornstover: Assessment of cellulosic compositions

Most studies on the production of volatile fatty acids (VFAs) from waste activated sludge (WAS) digestion have focused on operating conditions, pretreatments and characteristic adjustments. Conditioning by extra carbon sources (ECS), normally added in a solid form, has been reported to be an efficient approach. However, this has caused considerable waste of monomeric sugars in the hydrolysate. In this study, the effects of two added forms (pretreated straw (S) and hydrolyzed liquid (L)) of cornstover (CS) on WAS acidification were investigated. To obtain different cellulosic compositions of CS, low-thermal or autoclaved assisted alkaline (TA or AA) pretreatments were conducted. The results showed that AA-L test achieved the highest VFAs value (653 mg COD/g VSS), followed by AA-S (613 mg COD/g VSS). These values were 12% and 28% higher, respectively, than that obtained in the TA-L and TA-S tests. Meanwhile, higher percentages of acetic acid were observed after AA pretreatment (~62% versus ~53% in TA). The added forms of CS played an important role in structuring the innate microbial community in the WAS, as shown by high-throughput sequencing and canonical correspondence analysis. The findings obtained in this work may provide a scientific basis for the potential implementation of co-digesting WAS with ECS simultaneously obtaining energy and high value-added products.

EPS solubilization and waste activated sludge acidification enhanced by alkaline-assisted bi-frequency ultrasonic pretreatment revealed by 3D-EEM fluorescence

The effect of alkaline-assisted bi-frequency (28 + 40 kHz) ultrasonic pretreatment on extracellular polymeric substances (EPS) solubilization and waste activated sludge (WAS) acidification was investigated. Experimental results showed that WAS disintegration and (volatile fatty acids) VFAs production were effectively improved by the pretreatment. The optimal ultrasonic treatment time and alkaline dosage were 45 min and 0.04 g NaOH per g TS. Under this optimal condition, a lysis rate of WAS of 36.8% was achieved, and the corresponding increased solute protein and carbohydrate concentrations were 4173 and 853 mg L−1, respectively. Three-dimensional excitation–emission matrix (3D-EEM) fluorescence indicated that the pretreatment applied in this study could effectively decompose the tightly-bound EPS matrix, located in the inner parts of sludge flocks, and further destroy the microbial cell wall. The detachment of EPS and release of intracellular substrates provided sufficient substrates for anaerobic acid-producing microorganisms, which evidently improved the subsequent VFA production from WAS fermentation. The maximum VFA concentration was 10 816 ± 275 mg COD per L (457.1 g COD per g VS) for 72 h fermentation time, which was 5.4-fold higher than that obtained for the un-pretreated WAS.

Microbial community response reveals underlying mechanism of industrial-scale manganese sand biofilters used for the simultaneous removal of iron, manganese and ammonia from groundwater

Most studies have employed aeration–biofiltration process for the simultaneous removal of iron, manganese and ammonia in groundwater. However, what’s inside the “black box”, i.e., the potential contribution of functional microorganisms behavior and interactions have seldom been investigated. Moreover, little attention has been paid to the correlations between environmental variables and functional microorganisms. In this study, the performance of industrial-scale biofilters for the contaminated groundwater treatment was studied. The effluent were all far below the permitted concentration level in the current drinking water standard. Pyrosequencing illustrated that shifts in microbial community structure were observed in the microbial samples from different depths of filter. Microbial networks showed that the microbial community structure in the middle- and deep-layer samples was similar, in which a wide range of manganese-oxidizing bacteria was identified. By contrast, canonical correlation analysis showed that the bacteria capable of ammonia-oxidizing and nitrification was enriched in the upper-layer, i.e., Propionibacterium, Nitrosomonas, Nitrosomonas and Candidatus Nitrotoga. The stable biofilm on the biofilter media, created by certain microorganisms from the groundwater microflora, played a crucial role in the simultaneous removal of the three pollutants.

Microbial network of the carbonate precipitation process induced by microbial consortia and the potential application to crack healing in concrete

Current studies have employed various pure-cultures for improving concrete durability based on microbially induced carbonate precipitation (MICP). However, there have been very few reports concerned with microbial consortia, which could perform more complex tasks and be more robust in their resistance to environmental fluctuations. In this study, we constructed three microbial consortia that are capable of MICP under aerobic (AE), anaerobic (AN) and facultative anaerobic (FA) conditions. The results showed that AE consortia showed more positive effects on inorganic carbon conversion than AN and FA consortia. Pyrosequencing analysis showed that clear distinctions appeared in the community structure between different microbial consortia systems. Further investigation on microbial community networks revealed that the species in the three microbial consortia built thorough energetic and metabolic interaction networks regarding MICP, nitrate-reduction, bacterial endospores and fermentation communities. Crack-healing experiments showed that the selected cracks of the three consortia-based concrete specimens were almost completely healed in 28 days, which was consistent with the studies using pure cultures. Although the economic advantage might not be clear yet, this study highlights the potential implementation of microbial consortia on crack healing in concrete.

Upgrading VFAs bioproduction from waste activated sludge via co-fermentation with soy sauce residue

Conditioning of extra carbon sources has been widely reported to facilitate fermentation of waste activated sludge (WAS). Soy sauce residue (SSR) was a relatively untapped carbon source for sludge conditioning. This batch study aimed to evaluate the possible implementation of SSR for volatile fatty acids (VFAs) production from WAS. To upgrade the bioavailability of feedstock, three typical pretreatment methods were conducted, i.e., ammonium hydroxide (AH), sulfuric acids (SA) and thermal assisted alkaline (TA). AH pretreated test (AH-PT) outperformed due to a relatively strong structure decomposition of cellulosic materials as revealed by infrared spectroscopic analysis and crystal index. As a result, performed a high hydrolysis rate of 4449 mg COD/d, 1.12-1.23-fold higher than that in TA and SA pretreated tests (TA-PTand SA-PT), and 7.8-fold higher than that in the Control test. Meanwhile, a volatile fatty acids (VFAs) contribution of 401.2 mg COD/g SSR∙L and a maximum acidification rate of 3.59 d–1 was recorded, with a high sum proportion of mall molecular acetic and propionic 82.2%, 11%–70% increase over the other three tests. Besides, speciation process characterized with functional genus differentiation was identified by microbial diversity and distribution investigation and canonical correspondence analysis (CCA). Finally, a potential market value of 0.49–0.65 Billion €/year was preliminary estimated, showing promise of resource recovery from both WAS and SSR instead of extensive disposal.

Publisher Correction: Microbial network of the carbonate precipitation process induced by microbial consortia and the potential application to crack healing in concrete

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Efficient biorefinery of waste activated sludge and vinegar residue into volatile fatty acids: effect of feedstock conditioning on performance and microbiology

Carboxylic acids, particularly short chain (C2 and C3) fatty acids, are the preferable carbon source for many bioprocesses. Production efficiency of volatile fatty acids (VFAs) recovery from waste activated sludge (WAS) is limited by unbalanced nutrient components. In this study, a low-cost alternative approach (i.e., co-digestion with vinegar residue (VR)) to enhance C2–C3 VFAs recovery from WAS is reported. Compared to sole WAS digestion, concentration of total VFAs, C2–C5, increased by 187%, 74% and 44%, when co-digested with thermal-assisted alkaline (TA), ammonium hydroxide (AH) and sulfuric acid (SA) pretreated VR, respectively. Based on composition analysis, this improvement was mainly due to C2–C3 VFAs production. The hydrolysis rate constants in co-digestion tests, e.g., kh_TA = 0.0045 h−1, were also higher than that observed during mono-digestion (0.0018 h−1). Addition of VR greatly increased the hydrolysis of WAS, particularly with TA, thus enhancing the subsequent acidification process. High-throughput sequencing illustrated that certain groups of microbes (particularly hydrolytic and acid-producing bacteria), such as Acetobacterium, Proteiniclasticum, Cloacibacillus, Acinetobacter and Gemmobacter, were enriched in WAS and VR co-digestion. Further investigation of canonical correlation analyses showed that characteristic conditioning of digestion feedstock was an efficient strategy to restructure the inherent microbial community in WAS. The proposed concept in this study may be practical to simultaneously reduce operational, sludge transport and disposal costs of WWTPs.

Efficiency, granulation, and bacterial populations related to pollutant removal in an upflow microaerobic sludge reactor treating wastewater with low COD/TN ratio

In this study, a novel upflow microaerobic sludge reactor (UMSR) was constructed to conduct anaerobic digestion of municipal wastewater with low carbon and nitrogen ratio (C/N). Oxygen in the UMSR was supplied by falling water and external recirculation. Excellent nitrogen removal performance was obtained in the UMSR for treating wastewater with low C/N ratio at a temperature of 25 °C and a hydraulic retention time of 24 h. Ammonium and total nitrogen removal efficiencies averaged 92.35% and 90.41%, respectively, and sludge granulation occurred during acclimation. The inferred metabolism of nitrogen removal and ecological positions of functional microbe were integrated into a granule model by scanning electron microscopy. Additionally, the analysis of microbial community indicated that aerobic nitrifying bacteria and heterotrophic bacteria survived on the surface of sludge floc and granules while the anaerobic autotrophic, heterotrophic denitrifying, and anaerobic ammonia oxidation bacteria were present in the inner layer.