[Cultivation of aerobic granules in a large pilot SBR with domestic sewage].

The cultivation of aerobic granules in a large pilot-scale SBR was investigated using domestic wastewater. After operation of 210 days, the granules with a diameter of 330 microm were successfully formed by seeding anaerobic digested sludge. Results showed that, during the first three months of operation under low organic load of influent, removal efficiencies of pollutants increased steadily including COD, NH(4+)-N, total nitrogen (TN) and total phosphorous (TP). Meanwhile, microorganisms related to nitrogen and phosphorous were enriched. The organic load was enhanced since cycle time was shortened to 6 h, and the operational performance of the reactor still remained stable. Moreover, the average particle size of the sludge started to increase, along with excellent settling ability and high bioactivity. After the formation of aerobic granules, Sludge volume index (SVI) was maintained at 30 mL x g(-1) and the mixed liquor suspended solid (MLSS) concentration in the SBR reached 8.8 g x L(-1). MLVSS/MLSS ratio of the sludge increased to 82% with a high oxygen uptake rate (OUR) of 5.32 mg x (min x L)(-1). Bacillus was dominant on the outer layer of granules, while cocci were mainly located inside. The average COD and TP removal efficiencies kept at 90% and NH(4+) -N was almost completely depleted, NO(3-) -N and NO(2-) -N were not accumulated in the effluent. The aerobic granules were also capable of achieving simultaneous nitrification and denitrification (SND) in a single SBR cycle, which resulted in a high TN removal efficiency of 80%.

[Cultivation of aerobic granules by a method of alternative feed loading].

The formation process and morphological and physicochemical properties of aerobic granules were examined in a SBR system by a method of alternative feed loading. The results showed that the aerobic granules could be quickly and effectively cultivated using the alternative feeding COD 400, 800, 1200 mg/L [feed loading 0.96, 1.92 and 3.84 kg/(m3 x d)] when other conditions were fixed. The developed granules of the reactor were maintained in MLSS 20-22 g/L and SVI 14-16 mL/g. The average size of completely granular particles was 613.6 microm in diameter. The cocci occupied mainly in outer layer of granules, and both cocci and rods existed in inner layer of particles. The granules reached 95% COD removal and 97% NH4+ -N-removal simultaneously. The analysis of FISH showed AOB was distributed in outer surface of aerobic granules, and NOB existed in outer and inner layer small amounts of aerobic granules.

Formation, physical characteristics and microbial community structure of aerobic granules in a pilot-scale sequencing batch reactor for real wastewater treatment.

In this study, aerobic granular sludge was successfully developed in a pilot-scale sequencing batch reactor (SBR) installed on site to treat real wastewater using traditional activated sludge as inoculum. Compared with 1 or 2 months required by lab-scale reactor for aerobic granulation, it took about 400 days for activated sludge to transform into granule-dominant sludge in the pilot-scale SBR on site. Although the sludge in the reactor after 400-day operation was a mixture of flocs and granules with floc ratio ranged from 5 to 30%, sludge volume index with 5min settling (SVI5) always maintained at around 30mL/g. The similar microbial community structures represented by denaturing gradient gel electrophoresis (DGGE) between coexisted flocs and granules in the reactor indicated no strong microbial selection after the granules were dominant in the reactor. Chemical oxygen demand (COD) and NH4(+)-N removal efficiencies were above 80 and 98%, respectively, after 50-day operation, and the total inorganic N removal efficiency was about 50%. The results in this study demonstrate that it is feasible to form aerobic granules in pilot-scale SBR reactor and maintain the long-term stability of granular sludge with a high influent quality fluctuation. Meanwhile, stable COD and NH4(+)-N removal efficiencies can be obtained in the reactor.

[Filamentous overgrowth in aerobic granules].

Filamentous overgrowth has been observed after aerobic granulation in shaking sequencing batch reactors (SSBR). The factors affecting the filamentous overgrowth in aerobic granules and its possible control methods were investigated. It was found that both the influent and sludge inoculation largely influenced the filamentous overgrowth in aerobic granules. With the same activated sludge inoculation, the filamentous overgrowth in R3 treating fresh wastewater was much more severe than that in R1 treating saline wastewater. The filamentous overgrowth in R2 was the least among the three reactors, which was inoculated anaerobic granules and treated saline wastewater. When the filamentous overgrowth happened at the outer aerobic granules, Delta referring the degree of filamentous overgrowth achieved DeltaR1 = 1.4, DeltaR2 = 1.2 and DeltaR3 = 2.0, respectively. Filamentous identification showed that the filamentous microorganisms in R1 mainly composed of Eikelboom 0092 and Nocardia spp., Fungi spp. and Nocardia spp. in R2, S. natans and H. hydrossis in R3. The identified filamentous microorganisms likely occurred in conditions with long SRT, low dissolved oxygen and biodegradable substrates. However, due to the fact that filamentous overgrowth in aerobic granules initiated in the inner part of the granules and acted as frameworks with rod-shape or coccoid bacteria entrapping into in the granulation period, various strategies effectively in dealing with conventional bulking problems including shorting SRT, changing organic loading rate and enhancing aeration et al, could not effectively inhibit the filamentous growth in aerobic granules. The filamentous overgrowth was ultimately controlled through changing the substrate from synthetic glucose-rich wastewater to non-biodegradable wastewater.

Natural product juglone targets three key enzymes from Helicobacter pylori: inhibition assay with crystal structure characterization.

AIM: To investigate the inhibition features of the natural product juglone (5- hydroxy-1,4-naphthoquinone) against the three key enzymes from Helicobacter pylori (cystathionine gamma-synthase [HpCGS], malonyl-CoA:acyl carrier protein transacylase [HpFabD], and beta-hydroxyacyl-ACP dehydratase [HpFabZ]). METHODS: An enzyme inhibition assay against HpCGS was carried out by using a continuous coupled spectrophotometric assay approach. The inhibition assay of HpFabD was performed based on the alpha-ketoglutarate dehydrogenase-coupled system, while the inhibition assay for HpFabZ was monitored by detecting the decrease in absorbance at 260 nm with crotonoyl-CoA conversion to beta -hydroxybutyryl-CoA. The juglone/FabZ complex crystal was obtained by soaking juglone into the HpFabZ crystal, and the X-ray crystal structure of the complex was analyzed by molecular replacement approach. RESULTS: Juglone was shown to potently inhibit HpCGS, HpFabD, and HpFabZ with the half maximal inhibitory concentration IC50 values of 7.0 +/-0.7, 20 +/-1, and 30 +/-4 micromol/L, respectively. An inhibition-type study indicated that juglone was a non-competitive inhibitor of HpCGS against O-succinyl- L-homoserine (Ki=alphaKi=24 micromol/L), an uncompetitive inhibitor of HpFabD against malonyl-CoA (alphaKi=7.4 micromol/L), and a competitive inhibitor of HpFabZ against crotonoyl-CoA (Ki=6.8 micromol/L). Moreover, the crystal structure of the HpFabZ/juglone complex further revealed the essential binding pattern of juglone against HpFabZ at the atomic level. CONCLUSION: HpCGS, HpFabD, and HpFabZ are potential targets of juglone.

[Experimental investigation of high saline wastewater treatment using aerobic granules].

Complete aerobic granulation could be achieved in shaking sequencing batch reactors (SSBR) with saline wastewater respectively inoculated conventional activated sludge and anaerobic granules. Pretty good specific TOC removal rates could be achieved without inoculating the halo-bacteria at the start-up time. When the salinity was less than 10 g/L NaCl with the synthetic glucose-rich wastewater as substitute, the TOC removal efficiency was in the range of 70.3%-97.6%. After the salinity was 35 g/L NaCl and the influent was completely changed to Vc wastewater as substrate, similar TOC removal efficiency about 70% could be achieved compared with the performance of fresh Vc wastewater treatment under the same condition. The granules in saline wastewater had a diameter of 0.5-3 mm, and saline aerobic granules had much higher settling velocity, higher oxygen utilization rate (OUR), lower sludge production and better structural integrity than those of the granules from fresh wastewater. Saline aerobic granules showed perfect protecting-ability against the saline shock and could quickly recover from long term sharp saline change. Due to the different sludge inoculation, the aerobic granules from aerobic flocs had superior TOC removal performance and inferior saline shock protecting-ability compared with the aerobic granules from anaerobic granules.