Rapid cultivation of the aerobic granules for simultaneous phenol degradation and ammonium oxidation in a sequencing batch reactor

The potential effects of N-Acyl homoserine lactones on aerobic sludge granulation during phenolic wastewater treatment

The formation of aerobic granular sludge (AGS) is relatively difficult during the treatment of refractory wastewater, which generally shows small granular sizes and poor stability. The formation of AGS is regulated by N-Acyl homoserine lactones (AHLs)-mediated quorum sensing (QS). However, the potential role of AHLs in AGS formation under the toxic stress of refractory pollutants and the heterogeneity in the distribution and function of AHLs across different aggregates are not well understood. This study investigated the potential effects of AHLs on the formation of AGS during phenolic wastewater treatment. The distribution and succession of AHLs across varying granular sizes and development stages of AGS were investigated. Results showed that AGS was successfully formed in 13 days with an average granular size of 335 ± 39 μm and phenol removal efficiency of >99%. The levels of AHLs initially increased and then decreased. C4-HSL and 3-oxo-C10-HSL were enriched in large granules, suggesting they may play a pivotal role in regulating the concentration and composition of extracellular polymeric substances (EPS). The content of EPS constantly increased to 149.4 mg/gVSS, and protein (PN) was enriched in small and large granules. Luteococcus was the dominant genus constituting up to 62% after the granulation process, and exhibited a strong association with C4-HSL. AHLs might also regulate the bacterial community responsible for EPS production, and pollutant removal, and facilitate the proliferation of slow-growing microorganisms, thereby enhancing the formation of AGS. The synthesis and dynamics of AHLs were mainly governed by AHLs-producing bacterial strains of Rhodobacter and Pseudomonas, and AHLs-quenching strains of Flavobacterium and Comamonas. C4-HSL and 3-oxo-C10-HSL might be the major contributors to promoting sludge granulation under phenol stress and play critical roles in large granules. These findings enhance our understanding of the roles that AHLs play in sludge granulation under toxic conditions.

Biochar inoculated with Rhodococcus biphenylivorans altered microecological regulation by promoting quorum sensing and electron transfer: Up-regulation of related genes and enhancement of phenol and ammonia degradation

Bioaugmentation is an efficient method for improving the efficiency of coking wastewater removal. Nevertheless, how different immobilization approaches affect the efficiency of bioaugmentation remains unclear, as does the corresponding mechanism. With the assistance of immobilized bioaugmentation strain Rhodococcus biphenylivorans B403, the removal of synthetic coking wastewater was investigated (drying agent, alginate agent, and absorption agent). The reactor containing the absorption agent exhibited the highest average removal efficiency of phenol (99.74 %), chemical oxygen demand (93.09 %), and NH4+-N (98.18 %). Compared to other agents, the covered extracellular polymeric substance on the absorption agent surface enhanced electron transfer and quorum sensing, and the promoted quorum sensing benefited the activated sludge stability and microbial regulation. The phytotoxicity test revealed that the wastewater's toxicity was greatly decreased in the reactor with the absorption agent, especially under high phenol concentrations. These findings showed that the absorption agent was the most suitable for wastewater treatment bioaugmentation.

Direct start-up of aerobic granular sludge system with dewatered sludge granular particles as inoculant

Aerobic granular sludge (AGS) is a promising technology for engineering applications in the biological treatment of sewage. New objective is to skip the conventional granulation step to integrate it into a continuous-flow reactor directly. This study proposed a method for integrating spherical pelletizing granular sludge (SPGS) into a new patented aerobic granular sludge bed (AGSB), a continuous up-flow reactor. AGSB system could be startup directly, and after 120 days of operation, the SPGS maintained a relatively intact spherical structure and stability. With an initial high chemical oxygen demand (COD) volume loading of over 2.0 kg/(m³·d), this system achieved the desired effect as the same as a mature AGS system. The final mixed liquid suspended solids, and the ratio of 30 min-5 min sludge volume index (SVI₃₀/SVI₅) were 20,000 mg/L, and 0.84, respectively. Although hydraulic elution and filamentous bacteria (FBs) had a slightly negative impact on initial phase pollutant removal, the final removal rates for COD, total nitrogen (TN), ammonia nitrogen (NH₄⁺-H), and total phosphorus (TP) were 90%, 70%, 95%, and 85%, respectively. The presence of specific functional microorganisms promoted the secretion of extracellular polymeric substances (EPS), from 90.65 to 209.78 mg/gVSS. The maturation process of SPGS altered the microbial community structures and reduced the species abundance of microbes in sludge.

Role of cycle duration on the formation of quinoline-degraded aerobic granules in the aspect of sludge characteristics, extracellular polymeric substances and microbial communities

This study investigated the culture and characteristics of quinoline-degraded aerobic granular sludge (AGS) under 8-h and 12-h cycle duration. According to results, the cultivation of an 8-h cycle duration enhanced the growth of quinoline-degraded AGS, as well as the settleability of sludge and the retention of biomass. Quinoline can be removed from mature AGS at a rate of more than 90%, but it is removed at a rate slightly higher when the AGS are cultured for 12-h. Compared to 12-h cycle duration, 8-h cycle duration result in a greater increase in the production of extracellular polymeric substances, particularly extracellular proteins. In these two systems, Acidovorax and Paracoccus dominated the quinoline degrading bacteria. In addition, analysis by non-metric multidimensional scaling (based on Bray-curtis distance) showed significant differences of community structure between the two reactors. Clostridia and Acidaminobacter are different bacteria with an 8-h cycle duration compared to 12 h. Relative abundance of nitrogen metabolism genes based on PICRUSt2 prediction, which explain the better total nitrogen removal for an 8-h cycle duration compared to a 12-h cycle duration. Finally, the KEGG pathway was analyzed in order to confirm the results of the microbial analysis.

Reaction of the anammox granules to various antibiotics and operating the anammox coupled denitrifying reactor for oxytetracycline wastetwater treatment

The anaerobic ammonium oxidation (anammox) basedtechnology has been considered as an economic and efficient way to remove nitrogen. However, the anammox bacteria could be strongly inhibited by antibiotics. In present research, inhibiting properties of oxytetracycline, penicillin and polymyxin sulfate upon the anammox activity were investigated through batch experiment. The results implied that anammox activity was significantly inhibited by oxytetracycline and polymyxin sulfate. The non-competitive inhibiting model showed that the inhibiting constants (Ki) of oxytetracycline and polymyxin sulfate were 188.5 and 17.7 mg/L, respectively. Meanwhile, the anammox process was not suppressed while the concentration of penicillin reached 3000 mg/L. In long-run experiment, the influent oxytetracycline concentration of the anammox coupled denitrifying reactor was operated at 20 mg/L. It was observed that the anammox performance completely deteriorated, while the NO₂^--N removing efficiency reached 15.8%. The obtained findings could provide important instruction for the treatment of antibiotic contaminated wastewater.

Quantitative proteomic analysis reveals the metabolic characteristics and adaptive mechanism of Cupriavidus oxalaticus T2 in the process of simultaneous nitrogen and phenol removal

Phenol and ammonia in wastewater pose a serious threat to ecosystems and human health. However, the currently limited studies on single bacterium simultaneously removing phenol and nitrogen pollution have not fully elucidated the relevant metabolic mechanisms. The differences in proteomic profile after supplementing with phenol and ammonia for 6 and 24 h, respectively, were evaluated to explore the metabolic characteristics and adaptive mechanism of Cupriavidus oxalaticus T2 during the simultaneous removal process of phenol and nitrogen. Results revealed that a new potential phenol para-degradation pathway appeared in T2. Phenol induced changes in nitrogen metabolism, resulting in increased denitrification and decreased synthesis of glutamate from ammonia at 6 h. In addition, phenol exposure enhanced the expression of cytochrome oxidases with high oxygen affinity and increased ATP synthesis. The increase in chemotaxis and flagellar assembly was conducive to the uptake and utilization of phenol. The synthesis of lipoic acid and biotin was also promoted to resist phenol toxicity. Moreover, phenol triggered cellular stress response, thereby leading to the upregulation of anti-stress proteins, such as universal stress protein, iron‑sulfur cluster protein, and chaperones. This study contributes to revealing the metabolic characteristics and adaptive mechanism of T2 during simultaneous nitrogen and phenol removal. SIGNIFICANCE: Phenol and ammonia often co-exist in wastewater, causing serious environmental problems. The information on the metabolic mechanism of simultaneously removing these two pollutants by bacteria is insufficient at present. Moreover, phenol is toxic to microbial and causes cells damage. Therefore, exploring the response mechanism of bacteria to phenol stress is conducive to understand their tolerance mechanism to aromatic compounds. In this study, the metabolic characteristics and adaptive mechanism of C. oxalaticus T2 during the simultaneous removal of phenol and nitrogen process were evaluated by comparing the proteome profiles at different stages. The results revealed the degradation pathways of phenol and nitrogen by strain T2. A variety of phenol response mechanisms were determined, including enhanced energy production, improved cell motility, increased the synthesis of lipoic acid and biotin, and combined action of multiple anti-stress proteins. This study is potentially useful to future phenol and nitrogen co-pollution bioremediation strategies and provides insight into the phenolic compound resistance mechanism in bacteria.