[Effect of temperature on the response characteristics of shortcut nitrification granular sludge].

The experiment was carried out in a sequencing batch reactor (SBR), using granular sludge with 90% shortcut nitrification accumulation ratio, which had been cultivated by the laboratory to seed the reactor. The effects of temperature on characteristics, stability, nitrogen conversion properties and activity of short-cut nitrification granular sludge were investigated. The results show that the temperature has a significant influence on structure and short-cut nitrification performance of short-cut nitrification granular sludge. 30 degrees C was the optimum temperature for shortcut nitrification granular sludge cultivation, and the granules were more compact which led better flocculation and settleability. SVI and average diameter of sludge reached up to 39 mL x g(-1) and 3.03 mm, respectively. The nitrification accumulation was maintained at 96.17% during this period. When the temperature was at 25 degrees C, the granules changed to a loose-structure along with the electronegativity increased as well as the hydrophobicity decreased, which was due to the increase of EPS and decreased ratio of protein to polysaccharide. The granules disintegrated during this period, at the same time, the nitrification accumulation ratio was below 35%. It can be seen that the shortcut nitrification performance was destroyed. At 15 degrees C, the shortcut nitrification sludge also disintegrated and had a looser structure. However, the oxygen penetration depth increased at a lower temperature, which made the relative quantity of ammonia oxidizing bacteria (AOB) in reactor increased, the nitrification accumulation was around 68% ultimately.

Effects of continuous thermophilic composting (CTC) on bacterial community in the active composting process.

The method of continuous thermophilic composting (CTC) remarkably shortened the active composting cycle and enhanced the compost stability. Effects of CTC on the quantities of bacteria, with a comparison to the traditional composting (TC) method, were explored by plate count with incubation at 30, 40 and 50°C, respectively, and by quantitative PCR targeting the universal bacterial 16S rRNA genes and the Bacillus 16S rRNA genes. The comparison of cultivatable or uncultivatable bacterial numbers indicated that CTC might have increased the biomass of bacteria, especially Bacillus spp., during the composting. Denaturing gradient gel electrophoresis (DGGE) analysis was employed to investigate the effects of CTC on bacterial diversity, and a community dominated by fewer species was detected in a typical CTC run. The analysis of sequence and phylogeny based on DGGE indicated that the continuously high temperature had changed the structure of bacterial community and strengthened the mainstay role of the thermophilic and spore-forming Bacillus spp. in CTC run.

Effect of trace amounts of polyacrylamide (PAM) on long-term performance of activated sludge.

This study aims at evaluating the impacts of PAM addition on activated sludge performance. Four lab-scale sequencing batch reactors (SBRs), each with a working volume of 3L, were investigated with different PAM concentrations. Experiments were conducted with varying organic loading rate and the sludge volume index (SVI), particle size, zeta potential, specific oxygen uptake rate (SOUR), mixed liquor suspended solids (MLSS), COD and ammonium removal efficiency were monitored over a 105-day period. The results showed that all of the PAM addition not only improved the removal efficiencies of COD and ammonium, but also exhibited some advantages on sludge performance. It was found that the sludge performance of settling property, flocculation and microbial activity increased with increasing concentration of PAM. However, high level of PAM (1mg/L) led to the formation of large amounts of loose-structure flocs, which eliminated dissolved oxygen transfer and caused the sludge disintegration, resulting in bad settleability and lower microbial activity. In this way, when the dosage of PAM was 0.1mg/L, the sludge had the best settling property and activity.

[Achieve single-stage autotrophic biological nitrogen removal process by controlling the concentration of free ammonia].

Through controlling the concentration of free ammonia in the sequencing batch reactor (SBR), the single-stage autotrophic biological nitrogen removal process was achieved, including partial nitrification and anaerobic ammonium oxidation. The experiment was completed via two steps, the enrichment of nitrite bacteria and the inoculation of the mixture of anammox biomass. The operating temperature in the SBR was (31 +/- 2) degrees C. During the step of the enrichment of nitrite bacteria, pH was about 7.8. Changes of FA concentration were achieved by controlling the concentration of influent NH4(+) -N(56-446 mg x L(-1)), in order to inhibit and eliminate the nitrate bacteria. The activity tests of the sludge, 55d after enrichment, showed strong activity of aerobic ammonium oxidation [2.91 kg x (kg x d)(-1)] and low activity of nitrite oxidation [0.03 kg x(kg x d)(-1)]. During the inoculation of the mixture of anammox biomass, changes of FA concentration were achieved by controlling the concentration of influent NH4(+) -N and pH. As the inoculation of anammox biomass, abundant of bacteria and nutrient content were into the reactor and there kept high activity of aerobic ammonium oxidation [2.83 kg x (kg x d)(-1)] and a certain activity of nitrite oxidation, at the same time, the activity of anammox and heterotrophic denitrification reached 0.65 kg x (kg x d)(-1) and 0.11 kg x (kg x d)(-1), respectively.

Changes in the actinomycetal communities during continuous thermophilic composting as revealed by denaturing gradient gel electrophoresis and quantitative PCR.

Actinomycetes degrade cellulose and solubilize lignin during composting. Changes in the diversity of the actinomycetal communities and the 16S rDNA copy numbers of actinomycetes were monitored by denaturing gradient gel electrophoresis (DGGE) and quantitative PCR (qPCR), respectively, during continuous thermophilic composting (CTC) and traditional composting (TC). qPCR indicated that the copy numbers from the CTC samples were 25-80% higher than those from the TC samples during similar phases of active composting and they were lower than 3×10(9) gene copies/g (dry weight) in the mature compost from both runs. DGGE showed a more diverse actinomycetal community in the CTC than in TC, averaging 16 bands as compared to 12 bands, at the post peak temperature phase. The study suggested that temperatures higher than 50 °C in CTC benefited the growth of actinomycetes.

Biological treatment of landfill leachate with the integration of partial nitrification, anaerobic ammonium oxidation and heterotrophic denitrification.

A biological treatment with the integration of partial nitrification, anaerobic ammonium oxidation (Anammox) and heterotrophic denitrification was successfully developed in a SBR with periodical air supply to treat landfill leachate. An operating temperature of 30+/-1 degrees C and a dissolved oxygen concentration within 1.0-1.5 mg/L were maintained in the SBR. First, the mixture of Anammox biomass and aerobic activated sludge (80% w/w) were inoculated, and inorganic synthetic wastewater with progressively increased N-loading was added. The activities of maximum aerobic ammonium oxidizing and anaerobic ammonium oxidizing reached 0.79 and 0.18(kg NH(4)(+)-N/kg(dw)/day) after the inoculation lasting 86 days, respectively. Secondly, an unexpected group of heterotrophic denitrifying bacteria was inoculated into the reactor along with the feeding of raw landfill leachate, and the final maximum activities of aerobic ammonium oxidizing, anaerobic ammonium oxidizing and denitrification reached 2.83 (kg NH(4)(+)-N/kg(dw)/day), 0.65 (kg NH(4)(+)-N/kg(dw)/day) and 0.11 (kg NO(3)(-)-N/kg(dw)/day), respectively.

Continuous thermophilic composting (CTC) for rapid biodegradation and maturation of organic municipal solid waste.

Fewer and fewer municipal solid wastes are treated by composting in China because of the disadvantages of enormous investment, long processing cycle and unstable products in a conventional composting treatment. In this study, a continuous thermophilic composting (CTC) method, only a thermophilic phase within the process, has been applied to four bench-scale composting runs, and further compared with a conventional composting run by assessing the indexes of pH, total organic carbon (TOC), total Kjeldahl nitrogen (TKN), C/N ratio, germination index (GI), specific oxygen uptake rate (SOUR), dissolved organic carbon (DOC) and dehydrogenase activity. After composting for 14 days, 16 days, 18 days and 19 days in the four CTC runs, respectively, mature compost products were obtained, with quality similar to or better than which had been stabilized for 28 days in run A. The products from the CTC runs also showed favorable stability in room temperature environment after the short-term composting at high temperature. The study suggested CTC as a novel method for rapid degradation and maturation of organic municipal solid wastes.

[Effect on the performance of SBBR and the form transformation of nitrogen by different influent pattern].

The difference of sequencing batch biofilm reactor (SBBR) performance and nitrogen transformation mechanism which caused by four different influent patterns were researched. Through variance analysis of SBBR performance, microbial community structure and nitrogen transformation, the results indicated that, on the one hand the dispersed influent pattern displayed higher anti-load ability than the centralized one, under the same efficiency, COD and ammonia load of the dispersed M4 reached 2540 mg x (L x d)(-1) and 540 mg x (L x d)(-1) respectively compared with 2000 mg x (L x d)(-1) and 420 mg x (L x d)(-1) by the centralized M1; on the other hand, considering the dispersed influent pattern, the closer influent mood was to the cycle mood of operation, the higher the nitrogen transformation efficiency was, which finally led residual nitrogen concentration declined.

[Control of shortcut nitrification in SBBR with adequate oxygen supply].

At the high level of dissolved oxygen (DO) in sequencing batch biofilm reactor (SBBR), the approach and mechanism for realizing shortcut nitrification were researched. Landfill leachate was used as handling of object, the mainly environment parameters of the reactor were controlled as follow: DO 5 mg/L, pH 7.0, temperature 25 degrees C, adopted all drainage mode and 12-hour cycle influent. Through mathematical derivation and modeling analysis, determined free ammonia (FA), CO2 and HNO2 as the direct control factors, whereas the influent cycle time was the indirect one, shortcut nitrification was achieved effectively in SBBR. When the volume load of ammonia (NH4(+) -N) was 0.52 kg/(m3 x d) and NaHCO3 was 1.5 mg/L in the reactor, the shortcut nitrification effect was apparent as NH4(+) -N conversion rate was 89% and NO2(-) -N accumulation rate achieved 83% at the same time. With adequate oxygen supply, the key factors of achieving NO2(-) -N accumulation is FA concentration, and as the carbon source of ammonia-oxidizing bacteria, CO2 can upgrade the reactor performance further.

[Bacterial diversity in sequencing batch biofilm reactor (SBBR) for landfill leachate treatment using PCR-DGGE].

For studying the bacterial diversity and the mechanism of denitrification in sequencing bath biofilm reactor (SBBR) treating landfill leachate to provide microbial evidence for technique improvements, total microbial DNA was extracted from samples which were collected from natural landfill leachate and biofilm of a SBBR that could efficiently remove NH4+ -N and COD of high concentration. 16S rDNA fragments were amplified from the total DNA successfully using a pair of universal bacterial 16S rDNA primer, GC341F and 907R, and then were used for denaturing gradient gel electrophoresis (DGGE) analysis. The bands in the gel were analyzed by statistical methods and excided from the gel for sequencing, and the sequences were used for homology analysis and then two phylogenetic trees were constructed using DNAStar software. Results indicated that the bacterial diversity of the biofilm in SBBR and the landfill leachate was abundant, and no obvious change of community structure happened during running in the biofilm, in which most bacteria came from the landfill leachate. There may be three different modes of denitrification in the reactor because several different nitrifying bacteria, denitrifying bacteria and anaerobic ammonia oxidation bacteria coexisted in it. The results provided some valuable references for studying microbiological mechanism of denitrification in SBBR.

[Approaches of biological nitrogen removal in a single sequencing batch biofilm reactor].

The conventional microorganism techniques and the molecule biological techniques such as PCR and DGGE were utilized to study the approaches of biological nitrogen removal in a single sequencing batch biofilm reactor (SBBR). The main approach of biological nitrogen removal, no less than 65% of the total NH4(+)-N was removed in this approach, was composed of partial nitrification, anaerobic ammonium oxidation and denitrification. The second approach included twain processes such as partial nitrification and denitrification, and the third one was conventional nitrogen removal process (nitrification and denitrification). All approaches accomplished simultaneously or asynchronously. When the approach occurred in the simultaneous way, it performed as nitrogen-loss. The accomplisher of asynchronous way depended on the microbe's different activity between aerated phase and anaerobic phase. First, ammonia was converted to nitrite in the aerated phase when the nitrite bacteria performed high activity, and then anaerobic phase was operated in turn when the denitrifying bacteria and the anammox bacteria eliminated the nitrogen form gases.