Strong bacterial stochasticity and fast fungal turnover in Taihu Lake sediments, China.

Understanding the assembly and turnover of microbial communities is crucial for gaining insights into the diversity and functioning of lake ecosystems, a fundamental and central issue in microbial ecology. The ecosystem of Taihu Lake has been significantly jeopardized due to urbanization and industrialization. In this study, we examined the diversity, assembly, and turnover of bacterial and fungal communities in Taihu Lake sediment. The results revealed strong bacterial stochasticity and fast fungal turnover in the sediment. Significant heterogeneity was observed among all sediment samples in terms of environmental factors, especially ORP, TOC, and TN, as well as microbial community composition and alpha diversity. For instance, the fungal richness index exhibited an approximate 3-fold variation. Among the environmental factors, TOC, TN, and pH had a more pronounced influence on the bacterial community composition compared to the fungal community composition. Interestingly, species replacement played a dominant role in microbial beta diversity, with fungi exhibiting a stronger pattern. In contrast, stochastic processes governed the community assembly of both bacteria and fungi, but were more pronounced for bacteria (R2 = 0.7 vs. 0.5). These findings deepen the understanding of microbial assembly and turnover in sediments under environmental stress and provide essential insights for maintaining the multifunctionality of lake ecosystems.

[Adsorption Characteristics and Mechanism of Ammonia Nitrogen in Water by Nano Zero-valent Iron-modified Biochar].

The adsorption performances of ammonia nitrogen (NH+4-N) in water by unmodified biochar are ineffective. In this study, nano zero-valent iron-modified biochar (nZVI@BC) was prepared to remove NH+4-N from water. The NH+4-N adsorption characteristics of nZVI@BC were investigated through adsorption batch experiments. The composition and structure characteristics of nZVI@BC were analyzed using scanning electron microscopy, energy spectrum analysis, BET-N2 surface area (SSA), X-ray diffraction, and FTIR spectra to explore the main adsorption mechanism of NH+4-N by nZVI@BC. The results showed that the composite synthesized at the iron to biochar mass ratio of 1:30 (nZVI@BC1/30) performed well in NH+4-N adsorption at 298 K. The maximum adsorption amount of nZVI@BC1/30 at 298 K was remarkably increased by 45.96% and reached 16.60 mg·g-1. The pseudo-second-order model and Langmuir model fitted well with the adsorption process of NH+4-N by nZVI@BC1/30. There was competitive adsorption between coexisting cations and NH+4-N, and the sequence of coexisting cations to the adsorption of NH+4-N by nZVI@BC1/30 was Ca2+> Mg2+> K+> Na+. The adsorption mechanism of NH+4-N by nZVI@BC1/30 could be mainly attributed to ion exchange and hydrogen bonding. In conclusion, nano zero-valent iron-modified biochar can improve the adsorption performance of NH+4-N and enhance the application potential of biochar in the field of nitrogen removal from water.

[Main Influencing Factors and Strengthening of Anaerobic Transformation of Excess Sludge in China].

The anaerobic conversion efficiency of excess sludge in China is significantly lower than that in developed countries. Sludge characteristics are important influencing factors in the anaerobic degradability of sludge. The typical differences between excess sludge in China and in developed countries are mainly reflected in three aspects:long sludge age, high content of micro-sized grits, and high content of metal ions. Therefore, the effects of sludge age, micro-sized grits (represented by silica particles), and metal ions on the anaerobic digestion (AD) of excess sludge were studied systematically. Quantified comparison and targeted enhancement research were also carried out. The results showed that the negative effect of grit in the influent on VS reduction of sludge during AD was not obvious, while sludge age and metal ions were the main inhibitory factors. In addition, the inhibition level of sludge age was significantly higher than that of metal ions (P<0.05). With an increase in sludge age, the inhibition level of metal ions showed a further strengthening trend. Therefore, it could be concluded that long sludge age was the most important factor limiting the degradability of excess sludge. Moreover, with thermal hydrolysis pretreatment (160℃, 0.55 MPa, 30 min), the cumulative methane yield and VS reduction of sludge with long sludge age (40 d) almost increased to the values of sludge with a sludge age of 5 d. That is, thermal hydrolysis pretreatment has the potential to break through the bottleneck of degradability of sludge caused by long sludge age.

[Comparison of the Microbial Community Structure in Nitrifying Processes Operating with Different Dissolved Oxygen Concentrations].

High-throughput sequencing was applied to analyze the microbial community structure of nitrifying reactors operated with different dissolved oxygen (DO) levels. Results showed that the nitrifying reactor (RL) run with low DO (0.2-0.3 mg·L-1) exhibited greater microbial richness and diversity than the reactor run under the high DO condition[RH, DO=(2.0±0.1) mg·L-1]. In contrast, the microbial community in RH was more highly functionally organized than that in RL. Although the communities in RH and RL shared over 85% of the total sampled genetic information, the relative abundance of some individual species varied between the different DO conditions. Members of the Proteobacteria phylum, which accounted for 80.7% of the total microbes in RH, were highly enriched, and the relative abundance of Nitrosomonas reached to 65.1%. However, the microbial community in RL was dominated by Proteobacteria (43.8%), Firmicutes (20.0%), and Bacteroidetes (15.1%). In addition, a large fraction of bacteria possessing hydrolyzation and fermentation functions under anaerobic or anoxic conditions were also present in RL including Lactococcus, Anaerolineaceae, and Rhodocyclaceae. As known ammonium-oxidizing bacteria, Nitrosomonas oligotropha and Nitrosomonas europaea were enriched in the RH and RL, respectively, while Nitrospira defluvii, being a nitrite-oxidizing bacteria, dominated both reactors. Rather than DO, ammonia and nitrite availability should be key factors in the selective enrichment of these nitrifiers.

[High-rate Nitrogen Removal in a Two-stage Partial Nitritation-ANAMMOX Process Under Mainstream Conditions].

A two-stage partial nitritation (PN)-ANAMMOX process was successfully carried out for low-strength NH4+-N (50 mg·L-1) wastewater treatment at ambient/low temperatures. The results show that an average total nitrogen removal rate and removal efficiency above 0.6 kg·(m3·d)-1and 80% could be maintained, respectively, at temperatures between 20℃ and 14℃. The two-stage PN-ANAMMOX process was successful both under NO2--N-limited and NH4+-N-limited conditions. When the two-stage PN-ANAMMOX process was operated under NH4+-N-limited conditions, the "limit of technology" for nitrogen removal (TN<3 mg·L-1) could be easily achieved by following anoxic denitrification. Lowering the temperature to 12℃ resulted in the reduction of the total nitrogen removal rate to~0.5 kg·(m3·d)-1. Due to the low temperature, the anammox reaction became the rate-limiting step for nitrogen removal, while the PN reaction was not impacted. In the temperature range of 10-20℃, the activity-temperature coefficients (θ) of the PN granules and ANAMMOX sludge were 1.056 and 1.172, respectively, suggesting that the anammox bacteria have a higher temperature sensitivity than the ammonium oxidizing bacteria (AOB). Overall, the results clearly indicate that the nitrogen removal loading rate of the two-stage PN-ANAMMOX process is mainly controlled by the activity and quantity of anammox biomass. In contrast, the process nitrogen removal efficiency mainly depends on the performance of the first-stage PN (i.e., effluent NO2--N/NH4+-N ratio and NO3--N concentration) under a constant nitrogen removal loading rate (no overload). Based on these results, a hierarchically separate control strategy was proposed to obtain a high-rate nitrogen removal during the two-stage mainstream PN-ANAMMOX process.

[Analysis of microbial community structure at full-scale wastewater treatment plants by oxidation ditch].

The microbial populations of the oxidation ditch process at the full-scale municipal wastewater treatment plants (WWTP) in a city in north China were analyzed by fluorescent in situ hybridization (FISH). Fractions structure varieties and distribution characteristics of Accumulibacter as potential phosphorus accumulating organisms (PAOs), and Competibacter as potential glycogen accumulating organisms (GAOs) were quantified. The results indicated that Accumulibacter comprised around 2.0% +/- 0.6%, 3.4% +/- 0.6% and 3.5% +/- 1.2% of the total biomass in the anaerobic tank, anoxic zone and zone, respectively, while the corresponding values for Competibacter were 25.3% +/- 8.7%, 30.3% +/- 7.1% and 24.4% +/- 6.1%. Lower Accumulibacter fractions were found compared with previous full-scale reports (7%-22%), indicating low phosphorus removal efficiency in the oxidation ditch system. Statistical analysis indicated that the amount of PAOs was significantly higher in the anoxic zone and the aerobic zone compared with that in the anaerobic tank, while GAOs remained at the same level.

Optimization of biodemulsifier production from Alcaligenes sp. S-XJ-1 and its application in breaking crude oil emulsion.

A biodemulsifier-producing strain of Alcaligenes sp. S-XJ-1, isolated from petroleum-contaminated soil of the Karamay Oilfield, exhibited excellent demulsifying ability. The application of this biodemulsifier significantly improved the quality of separated water compared with the chemical demulsifier, polyether, which clearly indicates that it has potential applications in the crude oil extraction industry. To optimize its biosynthesis, the impacts of carbon sources, nitrogen sources and pH were studied in detail. Paraffin, a hydrophobic carbon source, favored the synthesis of this cell wall associated biodemulsifier. The nitrogen source ammonium citrate stimulated the production and demulsifying performance of the biodemulsifier. An alkaline environment (pH 9.5) of the initial culture medium favored the strain's growth and improved its demulsifying ability. The results showed paraffin, ammonium citrate and pH had significant effects on the production of the biodemulsifier. These three variables were further investigated using a response surface methodology based on a central composite design to optimize the biodemulsifier yield. The optimal yield conditions were found at a paraffin concentration of 4.01%, an ammonium citrate concentration of 8.08 g/L and a pH of 9.35. Under optimal conditions, the biodemulsifier yield from Alcaligenes sp. S-XJ-1 was increased to 3.42 g/L.

Comparison between waste frying oil and paraffin as carbon source in the production of biodemulsifier by Dietzia sp. S-JS-1.

In order to lower the production cost, waste frying oils were used in the biosynthesis of demulsifier by Dietzia sp. S-JS-1, which was isolated from petroleum contaminated soil. After 7 days of cultivation, the biomass concentration of the most suitable waste frying oil (WFO II) culture reached 3.78 g/L, which was 2.4 times the concentration of paraffin culture. The biodemulsifier produced with WFO II culture broke the emulsions more efficiently than that produced with paraffin culture, given the same volume ratio of carbon source in the culture medium and the same cultivation conditions. It achieved 88.3% of oil separation ratio in W/O emulsion and 76.4% of water separation ratio in O/W emulsion within 5 h. With the aid of thin layer chromatography (TLC) and Fourier transform infrared (FTIR) spectrometry, biodemulsifiers produced from both paraffin and WFO II were identified as a mixture of lipopeptide homologues. The subtle variation in the distribution of these homologues and high biomass concentration of WFO II cultures may account for the afore-mentioned good demulsification performance.

[Production of biodemulsifier by Alcaligenes sp. XJ-T-1 with waste frying oil].

As a new member of demulsifier family, biodemulsifier is applied in oil-water emulsion breaking. A strain, XJ-T-1, was isolated from petroleum-contaminated soil and identified as Alcaligenes sp.. Its physicochemical properties, demulsification capability and utilization of waste oil were further investigated. With waste frying oil (WFO) as carbon source, the demulsifier produced by Alcaligenes sp. showed high demulsifying capability. Moreover, the production of demulsifier was 4.6 times of that generated with paraffine as the carbon source. The CMC(-1) of biodemulsifier produced by paraffine and waste frying oil was achieved at 10 and 20, respectively. The biodemulsifier cultured with paraffine as the carbon source achieved 96% and 50% of emulsion breaking ratio in W/O (water in oil) and O/W (oil in water) model emulsion, while the demulsifier cultured on waste frying oil II as carbon source exhibited 97.8% and 65% demulsification ratio in the two model emulsions correspondingly. From the dynamic change of kerosene breaking ratio, emulsion breaking ratio and water breaking ratio during demulsification process, it was found that this biodemulsifier reacted with the continuous phase of the emulsion prior to its reaction with the dispersed phase. It was identified the valid part of biodemulsifier produced by WFO II was lipopeptide by TLC and IR.

Evaluation of screening methods for demulsifying bacteria and characterization of lipopeptide bio-demulsifier produced by Alcaligenes sp.

In this paper, surface tension measurement, oil-spreading test and blood-plate hemolysis test were attempted in the screening of demulsifying bacteria. After the comparison to the screening results obtained in demulsification test, 50 mN/m of surface tension of culture was proposed as a preliminary screening standard for potential demulsifying bacteria. For the identification of efficient demulsifying strains, surface tension level was set at 40 mN/m. The detected strains were further verified in demulsification test. Compared to using demulsification test alone as screening method, the proposed screening protocol would be more efficient. From the screening, a highly efficient demulsifying stain, S-XJ-1, was isolated from petroleum-contaminated soil and identified as Alcaligenes sp. by 16S rRNA gene and physiological test. It achieved 96.5% and 49.8% of emulsion breaking ratio in W/O and O/W kerosene emulsion within 24h, respectively, and also showed 95% of water separation ratio in oilfield petroleum emulsion within 2h. The bio-demulsifier was found to be cell-wall combined. After soxhlet extraction and purification through silicon-gel column, the bio-demulsifier was then identified as lipopeptide biosurfactant by TLC and FT-IR.

[Migration and transformation of nitrogen in a HRAP treating domestic wastewater in rural area].

The migration and transformation of nitrogen were studied in a high-rate algal pond (HRAP) treating domestic wastewater. Total nitrogen varied from 17.13 mg/L to 133.2 mg/L while ammonia ranged from 1.85 mg/L to 108.3 mg/L in domestic wastewater. At HRT of 8 d, the annual average removal efficiency for TN and ammonia were 29.4% and 91.6%, respectively in the two-stage HRAP. The treatment performance ranked in a descending order as follows: summer, autumn, spring, winter. The major mechanism for the migration and transformation of nitrogen in HRAP were nitrification, assimilation by algae and others such as ammonia evaporation. Nitrification contributed to more than 50% of ammonia removal. Despite the possibility, the contribution of ammonia precipitation was negligible in HRAP. The total nitrogen was mainly removed through assimilation into particular organics and subsequent separation. The contribution of ammonia evaporation to total nitrogen removal was marginal. The overall removal of TN can be improved by recycling some treated effluent to the upstream septic tank or by upgrading a polishing hydrophyte pond.

[Effects of external carbon source on nitrogen and phosphorus removal in subsurface flow and free water surface integrated constructed wetland].

By adding municipal wastewater in effluent of ANOXIC-OXIC (A/O) reactor as external carbon source, effects of external carbon source on nitrogen and phosphorus removal in subsurface flow and free water surface integrated constructed wetland were studied in pilot-scale. Results indicate that, COD/TN and (NO2(-) + NO3(-))/TN in influent of wetland are 1.00 and 0.48, respectively, and load removal rates of COD, TN and TP are 1.82, 1.59 and 0.14 g (m2 x d)(-1), respectively, as directly treating effluent of A/O reactor in wetland (working condition I). COD/TN and (NO2(-) + NO3(-))/TN in influent of wetland are 3.55 and 0.44, respectively, and load removal rates of COD, TN and TP are 19.03, 5.42 and 0.29 g (m2 x d)(-1), respectively, as adding municipal wastewater in effluent of A/O reactor as external carbon source in wetland (working condition II). Compared with working condition I, load removal rates of TN and TP for working condition II increase 3.4 times and 2.1 times, respectively. Impact factors of load removal rate of TN and TP are water temperature, HRT, COD/TN and (NO2(-) + NO3(-))/TN, respectively, when ranges of influent load rates are 3.8 - 38.7 g x (m2 x d)(-1) for COD, 5.07 - 13.08 g x (m2 x d)(-1) for TN and 0.57 - 1.92 g x (m2 x d)(-1) for TP, respectively, and range of HRT is 0.5 - 1.0 d. TN load removal rate decreases by exponent function along with increase of HRT, linearly increases along with increase of water temperature and (NO2(-) + NO3(-))/TN, and increases by power function along with increase of COD/TN. TP load removal rate also increases by power function along with increase of COD/TN.

[Influence of wastewater initial pH on enhanced biological phosphorus removal in sequencing batch reactor (SBR)].

Two laboratory-scale sequencing batch reactors (SBRs) were operated continuously to investigate the influence of wastewater initial pH on enhanced biological phosphorus removal (SBR1: pH = 6.8; SBR2: pH = 7.6). Results show that SBR2 exhibits greater anaerobic phosphorus release than SBR1. During aerobic stage, SBR2 degrades less polyhydroxyalkanoates (PHA) than SBR1, and the ratio of glycogen synthesis to PHA degradation in SBR2 is much less than that of SBR1, but SBR2 takes up more phosphorus. Further studies show that due to less glycogen synthesis in SBR2 than in SBR1, lower PHA degradation in SBR2 doesn't result in lower phosphorus uptake. The higher phosphorus uptake and PHA utilization efficiency in SBR2 is probably caused by its more phosphorus accumulating organisms (PAO). At the end of aerobic phase, SBR2 has significantly higher phosphorus removal efficiency than SBR1 (93.67% against 65.06%). Thus, the efficiency of enhanced biological phosphorus removal can be significantly improved by controlling the initial pH of wastewater. This method is much more convenient than controlling the entire process pH of wastewater biological treatment.

[Studies on nitrogen and phosphorus enhancing removal in combined shale and steel slag subsurface constructed wetlands].

Effluent of municipal wastewater treatment plant operated under A/O process was treated by constructed wetlands for reclamation and reuse. These methods, such as phosphorus removal by adsorption of shale and steel slag, regulating C/N ratio and nitrogen oxidability in influent of wetland, were employed to study efficiency and impact factors of nitrogen and phosphorus removal in pilot-scale in combined shale and steel slag subsurface constructed wetlands. Results indicate that, When COD area load rate, TN area load rate, TP area load rate and hydraulic retention time (HRT) is 6.5-20.7 g x (m2 x d)(-1), 2.57-8.22 g x (m2 x d)(-1), 0.41 -1.32 g x (m2 x d)(-1) and 0.5- 1.6d, respectively. Removal efficiency of ammonium nitrogen, nitrite nitrogen and nitrate nitrogen is 85.8%, 56.3% and 18.6%, respectively. Removal efficiency, area load removal rate and removal kinetic constant of total nitrogen are 58.0%, 3.58 g x (m2 x d)(-1) and 0.31m x d(-1), respectively. TN area load removal rate is linearly increased with the increase of total nitrogen area load rate. Removal efficiency, area load removal rate and removal kinetic constant of total phosphorus are 90.4%, 0.89 g x (m2 x d)(-1) and 0.86 m x d(-1), respectively. TP area load removal rate is linearly increased with the increase of total phosphorus area load rate. Water temperature, HRT, COD/TN ratio and (NO2(-) -N + NO3(-) -N) /TN ratio are primary factors impacting nitrogen and phosphorus area load removal rate. Along with HRT and COD/TN ratio increase, TN area load removal rate increases according to power function. Along with water temperature and (NO2(-) -N + NO3(-) -N)/TN ratio increase, TN area load removal rate increases according to exponential function.

Chemical and biological flocculation process to treat municipal sewage and analysis of biological function.

The pilot-scale experimental apparatus and the procedure of the chemical and biological flocculation process to verify the feasibility in treating Shanghai municipal sewage were introduced in this paper. In addition, the biological function of the process was discussed. The results of optimal running showed that in the reaction tank, the concentration of mixed liquor suspended solid(MLSS) was 2 g/L, hydraulic retention time(HRT) was 35 min, dosage of liquid polyaluminium chloride(PAC) was 60 mg/L, and the concentration of polyacrylamide(PAM) was 0.5 mg/L. The effluent average concentrations of COD(Cr), TP, SS and BOD5 were 50 mg/L, 0.62 mg/L, 18 mg/L, and 17 mg/L, respectively. These were better than the designed demand. In addition, the existence of biological degradation in this system was proven by several methods. The removal efficiencies of the chemical and biological flocculation process were 20% higher than that of the chemical flocculation process above at the same coagulant dosage. The treatment process under different situations was evaluated on a pilot-scale experiment, and the results provided magnificent parameters and optimal condition for future operation of the plant.

[Characteristics of municipal sewage chem-bioflocculation treatment process by using PCR-DGGE technology].

It is reported that without cultivation, DNA could be directly extracted from environmental samples with molecular biological methods, such as polymerase chain reaction (PCR) and denaturting gradient gel electrophoresis (DGGE). To analyze the community diversity of activated sludge and bio-film in the municipal sewage, work was done to directly extrude crude DNA from activated sludge and bio-film samples, separate and amplify 16S rDNA by PCR and sequence it with DGGE. The results show the significant microbe community difference between cultivated and uncultivated activated sludge. Further research on the community diversity of two different sewage treatment processes was done and initial discussion on the microbial distribution in the same reactor and microbial structure in different experimental conditions was carried out. The sequences of several 16S rDNA DGGE fragments were determined and some possible bacteria were confirmed in comparision in GeneBank (NCBI). The results show that the PCR-DGGE technology combined with sequences determination is a feasible and efficient method for microorganism analysis in environmental sample.