Coupling of endogenous/exogenous nitrification and denitrification in an aerobic granular sequencing batch reactor.

The performance of endogenous/exogenous nitrification and denitrification in an aerobic granular sequencing batch reactor was investigated for treating inorganic wastewater with ammonia nitrogen of 250 mg/L. The sequencing batch reactor with an effective volume of 120.5 L was started by seeding autotrophic nitrifying granular sludge (ANGS) and operated under oxic (110 min)/anoxic (120 min)/oxic (110 min) aeration mode. The total inorganic nitrogen (TIN) removal efficiency of ANGS was between 60% and 70% without external carbon sources in days 1-25. However, the operation mode was unsustainable as endogenous nitrification and denitrification would lead to an obvious decrease of sludge concentration. After sodium acetate (the contributed chemical oxygen demand in the reactor was 250-300 mg/L) was added at the beginning of the anaerobic/anoxic stage from day 26, aerobic granules were inadaptable in a few days, which resulted in particle disintegration and SVI increase. As microbes gradually acclimated to the new environment, the aerobic granular sludge became smoother and denser, the relative abundance of denitrifying bacteria increased to 66.07%, and the removal efficiency of TIN gradually increased to more than 90% from day 89. Contributions of endogenous/exogenous nitrification and denitrification to TIN removal were 54.09% and 46.01%, respectively. The coupling of endogenous/exogenous nitrification and denitrification could reduce the aeration consumption, save the external carbon source dosage and decrease the alkalinity consumption, which provided another option for treating wastewater from ionic rare earth mine.

Rapid domestication of autotrophic nitrifying granular sludge and its stability during long-term operation.

The nitrifying granular sludge process is a prospective technology for the efficient treatment of rare earth mine wastewater in southern Jiangxi, China. However, the long formation time of nitrifying granular sludge greatly restricted its application. In the present study, nitrifying granules were domesticated in a pilot-scale sequencing batch reactor by using heterotrophic granular sludge as carriers and adding exogenous nitrifying bacteria concentrate. According to variations of granular properties and ammonia removal, autotrophic nitrifying granules were successfully domesticated within 38 days using the strategy. It was found that the process involved secondary nucleation and microbial community evolution of the seed heterotrophic granules, and Nitrosomonas replaced most heterotrophic bacteria and became the dominant species with the largest relative abundance. During the subsequent 168 days of operation, the domesticated autotrophic nitrifying granules were stable, and their structures were denser than those of the inoculated granules. The ammonia nitrogen removal rate of the reactor was greater than 90% for a long period of time, and persistent partial nitrification was once achieved. However, severe fluctuation of influent ammonia nitrogen during the 120th to 206th day significantly inhibited the activity of nitrifying bacteria, which gradually led to the decrease of the ammonia nitrogen removal rate.

Rapid cultivation and stability of autotrophic nitrifying granular sludge.

Autotrophic nitrifying granular sludge (ANGS) was cultivated by gradually decreasing the influent organics and adding exogenous nitrifying bacteria. Under the strategy, ANGS was domesticated within 36 days. Stability of the seed heterotrophic granules decreased significantly during conversion of organic wastewater to inorganic ammonia wastewater. Obvious granular breakage was observed during these days. However, the granular debris still had good settlement performance. With microbes gradually acclimated to the new environment, the debris provided a large number of carriers for the attached growth of the exogenous nitrifying bacteria, and they replaced the heterotrophic bacteria and became the dominant species. The domesticated ANGS showed good nitrification performance during the 37th to the 183rd day (ammonia nitrogen load between 0.28 and 0.29 kg/m3 · d). The removal rate of ammonia nitrogen was usually more than 95%, and nitrite accumulation rate was always larger than 50%. However, nitrification ability was gradually lost with the increase of the ammonia nitrogen load (0.3-0.64 kg/m3 · d) from the 184th day, and it almost approached the influent ammonia nitrogen at the 269th day. Interestingly, good structure stability of the ANGS was maintained during long-term operation, and the ANGS became smoother and denser at the end of the experiment.

IL1A polymorphisms is a risk factor for colorectal cancer in Chinese Han population: a case control study.

BACKGROUND: Colorectal cancer (CRC) is one of the most common cancers worldwide, and genetic variations exert distinct roles in its pathogenesis. Single nucleotide polymorphisms (SNPs) in interleukin 1 alpha (IL1A) were reported to be correlated to the susceptibility of diverse cancers. The aim of this study was to assess the association of IL1A SNPs with the risk of colorectal cancer in a Chinese Han population. METHODS: To evaluate the correlation between IL1A polymorphisms and CRC risk, Agena MassARRAY platform was used for genotype determination among 248 CRC patients and 463 controls. The relationships between IL1A variants and CRC susceptibility were examined by logistic regression analysis. Stratified analysis was conducted for the association detection in males and females. Haplotype construction and analysis were applied to evaluate the potential relationship between the genetic block and the risk of CRC. SNP functional exploration was performed with available bioinformatics datasets. RESULTS: After adjusting for age and gender, the "AA" genotype of rs2856838 exhibited a risk association with colorectal cancer in the recessive model (adjusted OR = 1.98, 95% CI: 1.05-3.72, p = 0.036). With stratified analysis, the recessive models of rs3783550 (OR = 2.17, 95% CI: 1.03-4.60, p = 0.043), rs2856838 (OR = 2.58, 95% CI: 1.13-5.87, p = 0.024), rs1609682 (OR = 2.20, 95% CI: 1.04-4.65, p = 0.040), and rs3783521 (OR = 2.13, 95% CI: 1.01-4.49, p = 0.048) revealed significant relationships between these variants and an increased CRC risk only in females. Bioinformatics analysis also revealed the putative functions of the selected SNPs. CONCLUSIONS: This study demonstrated that rs2856838 could influence the susceptibility to CRC in Chinese Han population from northwest China. IL1A variants rs3783550, rs2856838, rs1609682, and rs3783521 were associated with CRC risk only in females.

Evolution of microbial community during dry storage and recovery of aerobic granular sludge.

Aerobic granular sludge (AGS) was imbedded in agar and stored at 4 °C for 30 days, and then the stored granules were recovered in a sequencing batch reactor fed real wastewater within 11 days. Variations in microbial community compositions were investigated during dry storage and recovery of AGS, aiming to elucidate the mechanism of granular stability loss and recovery. The storage and recovery of AGS involved microbial community evolution. The dominant bacterial genera of the mature AGS were Zoogloea (relative abundance of 22.39%), Thauera (16.03%) and Clostridium_sensu_stricto (11.17%), and those of the stored granules were Acidovorax (26.79%), Macellibacteroides (12.83%) and Pseudoxanthomonas (5.69%), respectively. However, the dominant genera were Streptococcus (43.64%), Clostridium_sensu_stricto (12.3.6%) and Lactococcus (11.47%) in the recovered AGS. Methanogens were always the dominant archaeal species in mature AGS (93.01%), stored granules (99.99%) and the recovered AGS (94.84%). Facultative anaerobes and anaerobes proliferated and dominated in the stored granules, and their metabolic activities gradually led to granular structure destruction and property deterioration. However, the stored granules served as carriers for the microbes originated from the real septic tank wastewater during recovery. They proliferated rapidly and secreted a large number of extracellular polymeric substances which helped to recover the granular structure in 11 days.