Screening of Polyphosphate Accumulating Organisms and Their Phosphorus Removal Performance

[Objectives]To study the phosphorus removal performance of phosphate accumulating organisms(PAOs).[Methods]Activated sludge from domestic sewage treatment plant was used as the strain source,and phosphate accumulating organisms were screened by plate streaking method and dilution coating plate method.Six kinds of excellent phosphate accumulating organisms were obtained by metachromatic granule staining experiment,total phosphorus experiment and simulated sewage phosphorus removal experiment to assist the observation of bac-terial morphology and experiment of phosphorus removal capacity.In addition,the influencing factors of phosphorus removal capacity(nitrogen source,trace metal ions)were analyzed.[Results]In the case of simulated sewage,the phosphorus removal rate of strain b was the highest,reaching 66.25%,while the phosphorus removal rate of strain e and f was about 10%lower than that of the phosphorus uptake experiment.[Conclusions]This study is expected to provide a theoretical reference for the gradual optimization of the screening method of phosphorus re-moval bacteria in domestic sewage treatment.

Removal of nitrogen and phosphorus in a combined A^2/O-BAF system with a short aerobic SRT

A bench-scale anaerobic/anoxic/aerobic process-biological aerated filter （A^2/O-BAF） combined system was carded out to treat wastewater with lower C/N and C/P ratios. The A^2/O process was operated in a short aerobic sludge retention time （SRT） for organic pollutants and phosphorus removal, and denitrification. The subsequent BAF process was mainly used for nitrification. The BAF effluent was partially returned to anoxic zone of the A^2/O process to provide electron acceptors for denitrification and anoxic P uptake. This unique system formed an environment for reproducing the denitdfying phosphate-accumulating organisms （DPAOs）. The ratio of DPAOs to phosphorus accumulating organisms （PAOs） could be maintained at 28% by optimizing the organic loads in the anaerobic zone and the nitrate loads into the anoxic zone in the A^2/O process. The aerobic phosphorus over-uptake and discharge of excess activated sludge was the main mechanism of phosphorus removal in the combined system. The aerobic SRT of the A^2/O process should meet the demands for the development of aerobic PAOs and the restraint on the nitrifiers growth, and the contact time in the aerobic zone of the A^2/O process should be longer than 30 min, which ensured efficient phosphorus removal in the combined system. The adequate BAF effluent return rates should be controlled with 1--4 mg/L nitrate nitrogen in the anoxic zone effluent of A^2/O process to achieve the optimal nitrogen and phosphorus removal efficiencies.

Comparing results of cultured and uncultured biological methods used in biological phosphorus removal

Increasing attention has been paid to phosphate-accumulating organisms （PAOs） for their important role in biological phosphorus removal. In this study, microbial communities of PAOs cultivated under different carbon sources （sewage, glucose, and sodium acetate） were investigated and compared through culture-dependent and culture-independent methods, respectively. The results obtained using denaturing gradient gel electrophoresis （DGGE） of polymerase chain reaction-amplified 16S rDNA fragments revealed that the diversity of bacteria in a sewage-fed reactor （1#） was much higher than in a glucose-fed one （2#） and a sodium acetate-fed one （3#）; there were common PAOs in three reactors fed by different carbon sources. Five strains were separated from three systems by using a phosphaterich medium; they were from common bacteria isolated and three isolates could not be found in DGGE profile at all. Two isolates had good phosphorus removal ability. When the microbial diversity was studied, the molecular biological method was better than the culture-dependent one. When phosphorus removal characteristics were investigated, culture-dependent approach was more effective. Thus a combination of two methods is necessary to have a comprehensive view of PAOs.

Temporal Dynamics and Performance Association of the Tetrasphaera-Enriched Microbiome for Enhanced Biological Phosphorus Removal

Tetrasphaera have been recently identified based on the 16S ribosomal RNA(rRNA)gene as among the most abundant polyphosphate-accumulating organisms(PAOs)in global full-scale wastewater treatment plants(WWTPs)with enhanced biological phosphorus removal(EBPR).However,it is unclear how Tetrasphaera PAOs are selectively enriched in the context of the EBPR microbiome.In this study,an EBPR microbiome enriched with Tetrasphaera(accounting for 40%of 16S sequences on day 113)was built using a top-down design approach featuring multicarbon sources and a low dosage of allylthiourea.The microbiome showed enhanced nutrient removal(phosphorus removal~85%and nitrogen removal~80%)and increased phosphorus recovery(up to 23.2 times)compared with the seeding activated sludge from a local full-scale WWTP.The supply of 1 mg·L^(-1)allylthiourea promoted the coselection of Tetrasphaera PAOs and Microlunatus PAOs and sharply reduced the relative abundance of both ammonia oxidizer Nitrosomonas and putative competitors Brevundimonas and Paracoccus,facilitating the establishment of the EBPR microbiome.Based on 16S rRNA gene analysis,a putative novel PAO species,EBPR-ASV0001,was identified with Tetrasphaera japonica as its closest relative.This study provides new knowledge on the establishment of a Tetrasphaera-enriched microbiome facilitated by allylthiourea,which can be further exploited to guide future process upgrading and optimization to achieve and/or enhance simultaneous biological phosphorus and nitrogen removal from high-strength wastewater.

Isolation and Identification of Phosphate-accumulating Strain PAO3-1 and Its Phosphorus Removal Characteristics

A phosphate-accumulating bacteria strain PAO3-1 was isolated from biological phosphorus removal sludge supplied with sodium acetate as carbon source under stable performance. This strain has good enhanced biological phosphorus removal effect on normal activated sludge system. Phosphorus removal ratio was raised form 44% with no added strain to more than 82% with strain strengthening biological phosphorus removal. It is identified to be Alcaligenes sp. according to its morphology, biochemical characteristics and 16S rDNA sequence analysis. The cell of strain PAO3-1 is straight bacilli form, 0.4×1.1μm, no flagellum, gram negative and special aerobiotic. The optimal temperature and pH for growth are 32℃-37℃ and 5.5-9.5, respectively. The shape of slant clone is feathery. The phosphate accumulating rate of strain PAO3-1 was 8.1mgP/g cell·h, and 14.3 mgP/g cell·h when in phosphate-starving situation, which was 76.5% higher than that in non-starving situation. Its phosphate release rate of log course in anaerobic phase and in culture without phosphorus was 7.6mgP/g cell·h, while in stable course the rate was 6.1mgP/g cell·h. The rate in stable course was 19.7% lower than that in log course.

Performance of biological phosphorus removal and characteristics of microbial community in the oxic-settling-anaerobic process by FISH analysis

Performance of biological phosphorus removal in the oxic-settling-anaerobic(OSA) process was investigated. Cell staining and fluorescent in situ hybridization(FISH) were used to analyze characteristics and microbial community of sludge. Experimental results showed that phosphorus removal efficiency was near 60% and the amount of biological phosphorus accumulation in aerobic sludge of the OSA system was up to 26.9 mg/g. Biological phosphorus removal efficiency was partially inhibited by carbon sources in the continuous OSA system. Contrasted to the OSA system,biological phosphorus removal efficiency was enhanced by 14% and the average total phosphorus(TP) contents of aerobic sludge were increased by 0.36 mg/g when sufficient carbon sources were supplied in batch experiments. Staining methods indicated that about 35% of microorganisms had typical characteristics of phosphorus accumulating organisms(PAOs) . FISH analysis demonstrated that PAOMIX-binding bacteria were predominant microbial communities in the OSA system,which accounted for around 28% of total bacteria.

Distribution, residence time, autotrophic production, and heterotrophic removal of DOP in the Mirs Bay, northern South China Sea

The importance of dissolved organic phosphorus(DOP) as a potential nutrient source for primary producers in marine systems has been recognized for up to eight decades, but currently, the understanding of the biogeochemistry of DOP is in its infancy. In the present study, monthly data between 2000 and 2014 were used to analyze the temporal and spatial distributions of DOP in the Mir Bay, the northern South China Sea. The DOP residence time(TDOP) was also investigated using a simple regression analysis in combination with chlorophyll a(Chl a) measurements while excess DOP(ΔDOP), produced by the biogeochemical processes of autotrophic production and heterotrophic removal, was determined using a two-component mixing mass-balance model in combination with salinity measurements. The results showed that the DOP concentration was(0.017±0.010) mg/L higher in the surface-water compared with the bottom-water and higher in the inner Tolo Harbour and waters adjacent to Shatoujiao compared with the main zone of the bay. Although seasonal changes and annual variability in the DOP were small, the surface DOP concentration was higher in the wet season(April–September)than in the dry season(October–March) due to the impacts of seaward discharges and atmospheric deposition into the bay. Measurement and regression results showed that the DOP release rate from phytoplankton production was about 1.83(gP)/(gChl a) and the TDOP was about 7 d, which implied that the DOP cycle in the bay was rapid. The ΔDOP was calculated from the model to be about 0.000 mg/L in the main zone of the bay and about 0.002 mg/L in the inner Tolo Harbour and waters adjacent to Shaotoujiao, suggesting that the autotrophic production of DOP was almost balanced by the heterotrophic removal in the main zone of the bay and dominated in the inner Tolo Harbour and waters adjacent to Shaotoujiao. In conclusion, the Mirs Bay is very productive and fairly heterotrophic.

Effects of phosphorus resorption on bioactive phosphorus of different-aged Pinus massoniana plantations

Phosphorus(P)is an important nutrient element in the photosynthesis process of plants.The effect of stand age on P nutrient dynamics in subtropical plantations is unclear.In this study,the mechanisms of above-and belowground P cycling in subtropical P.massoniana plantations of different stand ages(5,9,19,29 and 35 years)were investigated.The percentage of metabolic P in leaves exhibited an initial rise and subsequent decline with stand age of P.massoniana throughout the growing season,culminating in a metabolic P proportion of 34%–68% in litter.During the non-growing season,the main change in the P components of P.massoniana fine roots was a transition from metabolic P to residual P.Relative to during the growing season,soil ligand P fractions decreased by 7%–22% and exchangeable P fractions increased by 0–16%in the non-growing season.Organ P components tended to decrease with increasing stand age,mainly due to the gradual decrease in soil-bioavailable P,a trend alleviated by litter input.The generation of dissolved P by soil phosphatases would limit the reduction in soilbioavailable P caused by leaf P resorption to some extent.The differences in leaf organ P components between the growing and non-growing seasons are attributed to the allocation of P by the P.massoniana.Overall,the results of this study provide a basis for exploring the mechanisms of soil bioavailable P and soil P enzymemediated organ P component allocation in P.massoniana forests.These findings will help improve the management of P-limited P.massoniana plantations to enhance their productivity.

Denitrifying phosphorus removal in a step-feed CAST with alternating anoxic-oxic operational strategy

A bench-scale cyclic activated sludge technology （CAST） was operated to study the biological phosphorus removal performance and a series of batch tests was carried out to demonstrate the accumulation of denitrifying polyphosphate-accumulating organisms （DNPAOs） in CAST system. Under all operating conditions, step-feed CAST with enough carbon sources in influent had the highest nitrogen and phosphorus removal efficiency as well as good sludge settling performance. The average removal rate of COD, NH4^＋-N, PO4^3--P and total nitrogen （TN） was 88.2%, 98.7%, 97.5% and 92.1%, respectively. The average sludge volume index （SVI） was 133 mL/g. The optimum anaerobic/aerobic/anoxic （AOA） conditions for the cultivation of DNPAOs could be achieved by alternating anoxic/oxic operational strategy, thus a significant denitrifying phosphorus removal occurred in step-feed CAST. The denitrification of NO^x--N completed quickly due to step-feed operation and enough carbon sources, which could enhance phosphorus release and further phosphorus uptake capability of the system. Batch tests also proved that polyphosphate-accumulating organisms （PAOs） in the step-feed process had strong denitrifying phosphorus removal capacity. Both nitrate and nitrite could be used as electron acceptors in denitrifying phosphorus removal. Low COD supply with step-feed operation strategy would favor DNPAOs accumulation.

Monitoring microbial community structure and succession of an A/O SBR during start-up period using PCR-DGGE

Polymerase chain reaction （PCR）-denaturing gradient gel electrophoresis （DGGE） protocol was employed for revealing microbial community structure and succession in a sequential anaerobic and aerobic reactor performing enhanced biological phosphorus removal （EBPR） during start-up period. High phosphorus removal was achieved after 15 d. On day 30, phosphorus removal efficiency reached to 83.2% and the start-up was finished. DGGE profiles of periodical sludge samples showed that dominant microbial species were 19 OTUs （operational taxonomy units）. Unweighted pair-group method using arithmetic averages （UPGMA） clustering analysis revealed that rapid community succession correlated to low phosphorus removal rate and high phosphorus removal efficiency reflected on steady community structure. Sequencing results indicated that determined sequences （12 OTUs） belonged to Proteobacterium, Actinobacteria, Gemmatimonadales and unaffiliate group. Proteobacterium, Tetrasphaera elongate and Gemmatimonas aurantiaca may act important roles in phosphorus removal. With little amount as known glycogen accumulating organisms, Candidatus Competibacter phosphatis still at accumulating-phase had limited effect on microbial community structure. When climax community was obtained, dominant microbes were 14 OTUs. Microbes in a large amount were uncultured bacterium Thauera sp., uncultured y-Proteobacterium and Tetrasphaera elongata.

Coagulation Mechanisms during the Substitution of Inorganic Salts with Cationic Polymers to Increase the Sludge Value

Phosphorus in wastewater sludge is a valuable resource although coagulated sludge reported to give only 10% of plant availability of phosphates. Since all Al and Fe added as coagulants end up in sludge, the potential to substitute them with cationic coagulants was studied. During combined coagulation, substitution possibilities up to 44% were observed with low coagulant-to-particle ratio where the adsorption-charge neutralisation (ACN) anticipated being the predominant mechanism. Comparatively high coagulant-to-particle ratio preferred Sweep-floc mechanism giving <20% substitution possibilities, though even lower values anticipated at higher phosphate removals. The cationic polymers’ ability to compete with positively charged Al- and Fe-hydrolysis products was argued as the explanation for higher substitution possibilities during ACN mechanism. Sub-stitutions can be enhanced with dual coagulation with intermediate sludge separation by avoiding competition between two coagulants.

Hypothesis for metabolites of denitrifying phosphate accumulating organisms by the restriction of denitrifying bacteria in anoxic phase

The objective of this work is to verify a hypothesis that nitrite accumulation comes from the metabolites of denitrification phosphate accumulating organisms (DPAOs),not denitrifying bacteria.On the precondition of the restriction of denitrifying bacteria in anoxic phase,static experimental test was designed using NO3-as electron acceptor,effluent was removed after sedimentation in anaerobic phase,and the same concentration solution of PO43--P was returned,so that TOC was excluded and denitrification was inhibited in the next phases.A parallel experiment was carried out simultaneously with the normal anaerobic-anoxic progress.The results showed that,in static test,by keeping the normal growth of DPAO and inhibiting denitrification of denitrifying bacteria,P-release in anaerobic and P-uptake in anoxic phase proceeded normally.DPAO had obvious effect on P-removal and the P-removal efficiency was 69%.The effluent concentration of NO3--N and NO2--N was 7.62 mg/L and 6.05 mg/L respectively,compared with parallel experiments,and nitrogen removal rate was lower.No nitrite residue was found in parallel test.Therefore,it can confirm the hypothesis that the metabolites of DPAO are both nitrogen and nitrite when nitrate is taken as electron acceptor,and nitrite is subsequently converted to nitrogen by denitrifying bacteria.

Demystifying polyphosphate-accumulating organisms relevant to wastewater treatment: A review of their phylogeny, metabolism, and detection

Currently,the most cost-effective and efficient method for phosphorus(P)removal from wastewater is enhanced biological P removal(EPBR)via polyphosphate-accumulating organisms(PAOs).This study integrates a literature review with genomic analysis to uncover the phylogenetic and metabolic diversity of the relevant PAOs for wastewater treatment.The findings highlight significant differences in the metabolic capabilities of PAOs relevant to wastewater treatment.Notably,Candidatus Dechloromonas and Candidatus Accumulibacter can synthesize polyhydroxyalkanoates,possess specific enzymes for ATP production from polyphosphate,and have electrochemical transporters for acetate and C4-dicarboxylates.In contrast,Tetrasphaera,Candidatus Phosphoribacter,Knoellia,and Phycicoccus possess PolyP-glucokinase and electrochemical transporters for sugars/amino acids.Additionally,this review explores various detection methods for polyphosphate and PAOs in activated sludge wastewater treatment plants.Notably,FISH-Raman spectroscopy emerges as one of the most advanced detection techniques.Overall,this review provides critical insights into PAO research,underscoring the need for enhanced strategies in biological phosphorus removal.

Efects of idle time on biological phosphorus removal by sequencing batch reactors

Three identical sequencing batch reactors （SBRs） were operated to investigate the effects of various idle times on the biological phosphorus （P） removal. The idle times were set to 3 hr （R1）, 10 hr （R2） and 17 hr （R3）. The results showed that the idle time of a SBR had potential impact on biological phosphorus removal, especially when the influent phosphorus concentration increased. The phosphorus removal efficiencies of the R2 and R3 systems declined dramatically compared with the stable R1 system, and the Prelease and P-uptake rates of the R3 system in particular decreased dramatically. The PCR-DGGE analysis showed that uncultured Pseudomonas sp. （GQ183242.1） and β-Proteobacteria （AY823971） were the dominant phosphorus removal bacteria for the R1 and R2 systems, while uncultured γ-Proteobacteria were the dominant phosphorus removal bacteria for the R3 system. Glycogen-accumulating organisms （GAOs）, such as uncultured Sphingomonas sp. （AM889077）, were found in the R2 and R3 systems. Overall, the R1 system was the most stable and exhibited the best phosphorus removal efficiency. It was found that although the idle time can be prolonged to allow the formation of intracellular polymers when the phosphorus concentration of the influent is low, systems with a long idle time can become unstable when the influent phosphorus concentration is increased.

广州垃圾填埋渗滤液中有机污染物的去除效果

采用同时好氧厌氧生物反应器处理广州市大田山垃圾填埋渗滤液,平均出水浓度CODCr为1 31mg·L-1 ,氨氮为7mg·L-1 ,达到了同类废水的国家二级排放标准.同时选择GC MS联用仪对垃圾渗滤液中的有机物进行测定,测得有机污染物87种,其中1 6种有机污染物被列入美国EPA环境优先控制污染物,31种有机物被完全去除,1 4种有机物去除率可达80 %以上,2 5种有机物去除率达5 0 %以上.

GC-MS法对垃圾渗滤液回灌处理前后有机成分的研究

利用模拟垃圾填埋装置进行渗滤液回灌处理的研究,取回灌处理后期的渗滤液与未经回灌处理渗滤液进行水质监测,并运用GC-MS联用技术对两种水样的有机成分进行对比分析。结果表明,羧酸类物质在检出物中所占比例较大,回灌处理对渗滤液中羧酸类物质的去除率达到61.26%,接近于CODC r的去除率59.65%。对一些毒害性物质也有一定的去除,哌啶类物质去除率为79.52%,呋喃的去除率为100%。

兰炭废水中有机污染物组成及其去除特性分析

为了明确兰炭废水中有机污染物的组成及其浓度,采用气相色谱法分析了废水中苯系物、酚类、多环芳烃等有机污染物的分布情况,并对处理过程中上述有机物的去除特性进行了研究。结果表明,在兰炭废水中8种苯系物总质量浓度为111.09 mg/L;14种酚类物质总质量浓度为3350.88 mg/L,其中苯酚质量浓度最高,达到1 333.44 mg/L;废水中检测到5种多环芳烃,总质量浓度为1 335.62 mg/L,其中萘质量浓度高达1328.04 mg/L;邻苯二甲酸二丁酯及吲哚在废水中均能检测到,但未检测到喹啉。物化-生化组合处理工艺对兰炭废水的处理效果良好,其中萃取处理单元对苯系物、酚类物质、多环芳烃的去除效果显著;在生化处理阶段,苯系物、酚类、邻苯二甲酸二丁酯、吲哚、喹啉去除率较高,但多环芳烃的去除效果较差。

Enhanced biological phosphorus removal using thermal alkaline hydrolyzed municipal wastewater biosolids

This study reports the feasibility of using municipal wastewater biosolids as an alternative carbon source for biological phosphorus removal.The biosolids were treated by a lowtemperature,thermal alkaline hydrolysis process patented by Lystek International Inc.(Cambridge,ON,Canada)to produce short-chain volatile fatty acids and other readily biodegradable organics.Two sequencing batch reactors(SBRs)were operated with synthetic volatile fatty acids(Syn VFA)and readily biodegradable organics produced from the alkaline hydrolysis of municipal wastewater biosolids(Lystek)as the carbon source,respectively.Municipal wastewaters with different strengths and COD:N:P ratios were tested in the study.The reactors’performances were compared with respect to nitrogen and phosphorus removal.It was observed that phosphorus removal efficiencies were between 98%–99%and 90%–97%and nitrogen removal efficiencies were 78%–81%,and 67%for the Syn VFA and Lystek,respectively.However,the kinetics for phosphorus release and uptake during the anaerobic and aerobic stages with Lystek were observed to be significantly lower than Syn VFA due to the presence of higher order VFAs(C4 and above)and other fermentable organics in the Lystek.

Short-term effect of temperature variation on the competition between PAOs and GAOs during acclimation period of an EBPR system

Sequencing batch reactor(SBR)for enhanced biological phosphorus removal(EBPR)processes was used to investigate the impact of the temperature shock on the competition between phosphorus-accumulating organisms(PAOs)and glycogen accumulating organisms(GAOs)in start-up stage.During the 34 days operation,SBR was set with temperature variation(0-5 d,22±1℃;6-13 d,29±1℃;14-34 d,14±1℃).PAOs and GAOs were analyzed by fluorescent in situ hybridization(FISH),and intracellular polyphosphate granules were stained by Neisser-stain.The results showed that the influence of temperature shock on PAOs’abundance was more serious than that on GAOs in the enriching process.Under sudden and substantially temperature variation,from 22±1℃ to 29±1℃ and then to 14±1℃,the domination of PAOs was deteriorated.After temperature shock,PAOs’competitive advantages at low temperature that concluded in other study did not appear in our study.As mesophilic,GAOs(indicated by Alphaproteobacteria and Gammaproteobacteria)were more temperature adaptive and better grew and took the domination at 14±1℃ in the end.In the competition process,organisms of tetrad forming organisms(TFOs)-like shape which were considered as typical GAOs,were observed.With the evidence of poly-P granules containing by Neisser-straining and result of FISH,these organisms of TFOs-like shape were better to be assumed as adaption state or a special self-protecting shape of PAOs.

高排放标准下污水处理厂深度处理工艺分析

依托3座市政污水处理厂开展了混凝沉淀-深床滤池-消毒深度处理工艺的效果分析。生物二级处理出水中需要关注SCOD、NO_(3)^(-)-N、颗粒性磷和PO_(4)^(3-)-P的去除效果,这些组分占COD、TN和TP的平均比例分别为71%、87%和75%以上。深度处理对COD、TN和TP的平均去除率分别为25.4%、15.5%和47.6%,ΔCOD/ΔPAC与ΔTP/ΔPAC(平均质量比)分别为1.4和0.07。深度处理显著提升了出厂水水质,对COD、TN、TP、SS和色度稳定达标起到了保障作用。