Phosphorus Uptake Rate Research Articles

Combined Effects of Tetracycline and Copper Ion on Microorganisms During the Biological Phosphorus Removal.

Tetracycline and copper ion are common pollutants in wastewater, and the effects of mixed pollutants on microorganisms in wastewater biological treatment have been less studied. In order to reveal the effects of mixed pollutants of tetracycline and copper ion on the microorganisms during the biological phosphorus removal, three ratios of tetracycline and copper ions were designed by the direct equipartition ray method. The relative abundance and diversity of microbial community were investigated, and the microbial interactions were revealed through microbiological methods. The results demonstrated that, for three different ratios, the inhibitory effect of specific phosphorus uptake rate became more significant with the increase of the tetracycline-copper ions concentration and the reaction time. The microbial community decreased with the increase of the proportion of tetracycline in different ratios. The relative abundance of Acinetobacter decreased with the increase of the proportion of tetracycline, while the relative abundance of Ca.Competibacter was higher under the conditions of low mixtures concentrations. Positive interactions and symbiotic relationships among microorganisms were predominant for three different ratios. However, as the proportion of tetracycline increased, the community structure of microorganisms shifted from phosphate-accumulating organisms to glycogen accumulating organisms and denitrifying bacteria. This study can provide a reference for the effect of mixed pollutants on microorganisms and the mechanism of wastewater treatment.

Metabolic response and clade variation in Accumulibacter under phosphorus deprivation stress

Two enhanced biological phosphorus removal systems (R1 and R2) fed with different carbon sources (acetic acid and propionic acid) were used to investigate the metabolic response of nitrite-type denitrifying phosphorus removal functional bacteria Accumulibacter to different phosphorus concentrations and the changes of its clade community structure. The results indicated that the systems almost lost the ability to release phosphorus after 15 d phosphorus deprivation, the contents of poly-P in the sludge of R1 and R2 decreased from 0.63 to 0.02 mgP/mgVSS and from 1.23 to 0.05 mgP/mgVSS, respectively. According to the analysis of stoichiometric parameters, the functional bacteria in both systems performed glycogen accumulating organism metabolism to survive under phosphorus-poor condition. Besides, the two systems exhibited a stronger EBPR ability even after 42 d phosphorus deprivation, and the maximum anoxic phosphorus uptake rate was 1.92 times and 2.29 times of those under phosphorus-rich conditions. Real-time quantitative Polymerase Chain Reaction detection indicated that the proportion of Accumulibacter in the two systems decreased from 16.45 % to 8.78 % and from 31.00 % to 8.43 %, respectively, as phosphorus was deprived. Clade IIC maintained its dominance in both systems, while clade IID was gradually washed out from propionic acid system, suggesting that clade IIC had a more flexible metabolic response to phosphorus deprivation stress.

Pressure of different level PFOS on aerobic granule sludge: Insights on performance, AGS structure, community succession, and microbial interaction responses

Perfluorooctane sulfonic acid (PFOS) has received much attention due to its potential environmental risks. However, the response of aerobic granular sludge (AGS) to PFOS exposure, particularly the microbial interactions, remains unclear. In this study, we investigated the particle structure of AGS, pollutant removal performance, community succession, and microbial interaction in the AGS system under different PFOS concentrations (0.1 and 1 mg/L). The mass balance showed that PFOS was mainly removed by adsorption with a removal rate of >85 %. PFOS caused some particles to break up and decreased the average particle size from 3.37 mm to 2.64 mm. It also significantly decreased the total nitrogen and total phosphorus removal rates, which was consistent with the deterioration of microbial activity, such as denitrification rate (25 % inhibition), phosphorus uptake rate (73.19 % inhibition), and phosphorus release rate (73.33 % inhibition). PFOS promoted the secretion of extracellular polymer (EPS) in AGS, especially proteins, leading to poor particle hydrophobicity. The network analysis illustrated that PFOS slowed down the information transfer between microorganisms, and increased the competition between them, which may be responsible for the deterioration of the system performance. Connections related to rare species accounted for >75 % of the network, suggesting that rare species have an indispensable role in community information exchange. In addition, rare species acted as seed banks for microorganisms, and under PFOS stress, they transformed into keystone species, which could contribute to system stabilization. This study provides new insights into the effects of PFOS on microbial interactions in AGS systems and the roles of rare species in the AGS microbial community.

Phosphorus release and uptake behavior and microbial metabolic activity in reversed A2O process: Importance of influent VFAs/COD and anaerobic duration

The reversed A2O (anoxic/anaerobic/aerobic) process is efficient in nitrogen removal from domestic wastewater, while phosphorus removal performance needs further optimization. In this study, the effects of influent VFAs/COD and anaerobic duration on anoxic/anaerobic phosphorus release and aerobic phosphorus uptake were investigated in the reversed A2O process. The results indicated that the maximum anoxic P release rate of 37.6 mg P/(L·h) was achieved in synthetic wastewater with influent VFAs/COD of 100%. With increasing VFAs/COD from 15% to 100%, the aerobic phosphorus uptake rate increased by 2.8–3.7 times. Proper extension of the anaerobic duration can marginally enhance the phosphorus uptake rate and aerobic microbial activity, thus resulting in higher phosphorus removal efficiency. As a consequence, the optimal anaerobic duration for domestic wastewater was confirmed to be 4 h. Additionally, there is a significant correlation between phosphorus removal related indicators of substances metabolism and microbial activity in synthetic wastewater. However, poor correlation between the indicators of phosphorus metabolism and microbial activities was observed in domestic wastewater, mainly due to the coexistence of other competitive biological reactions.

Effect of biofilm thickness on the activity and community composition of phosphorus accumulating bacteria in a moving bed biofilm reactor

Can biofilms enhance the rates of phosphorus removal in wastewater treatment? In order to narrow the scientific gap on the effect of biofilm thickness on the activity and microbial community of phosphorus-accumulating bacteria, this study investigated biofilms of 30 to 1000 µm thickness in a moving bed biofilm reactor. Measurements on 5 different biofilm carriers showed that biomass-specific phosphorus release and uptake rates increased as a function of biofilm thickness for biofilms thinner than about 110 µm but were lower for thicker biofilms of about 550–1000 µm. The reduced phosphorus uptake and release rates in the thickest biofilms can result from substrate mass transfer limitations whereas the low activity in the thinnest biofilms can be related to a too high turnover rate in the biofilm due to heterotrophic growth. Additionally, the microbial ecology of the different biofilms confirms the observed phosphorus uptake and release rates. The results from the full-length 16S rRNA gene sequencing of the bacterial community showed that the thicker biofilms were characterized by higher relative abundance (40–58%) of potential phosphorus accumulating genera Zoogloea, Acinetobacter, Dechloromonas and Ca. Accumulibacter. In contrast, the thinner biofilms were dominated by the genus Ferribacterium (34–60%), which might be competing with phosphorus-accumulating bacteria as indicated by the relatively high acetate uptake rates in the thinner biofilms. It is concluded that there is an optimal biofilm thickness of 100–500 µm, at which the phosphorus accumulating bacteria have the highest activity.

Effective CO2 capture by the fed-batch culture of Chlorella vulgaris

Microalgae are promising candidates for CO2 capture and concomitant biomass production. Chlorella vulgaris was grown in the batch and fed-batch cultures to develop a culture strategy targeting maximum CO2 capture and conversion to biomass. Growth at five different dissolved CO2 (dCO2) concentrations in the feeding media (atmospheric, 1.55, 1.62, 1.75 and 1.88 g L−1) was tested to assess the effect of dCO2 concentration on the growth, biomass productivity, and nutrients removal efficiency of microalgae. Results suggest that fed-batch culture outperformed “standard” batch cultivation with a higher algal growth rate (2.3 times). As expected, the algal growth was limited at low (atmospheric) dCO2 concentrations and inhibited at high levels (1.75 and 1.88 g L−1). C. vulgaris grown with medium containing 1.62 g L−1 dCO2 showed the highest growth rate (0.094 h−1) with the shortest doubling time (7.4 h), maximum biomass productivity, nitrogen and phosphorus uptake rates (222, 7.5 and 1.6 mg L−1 d−1, respectively). By pre-dissolving CO2 into the feeding media and using the fed-batch culture mode, a high CO2 removal efficiency could be achieved.

Soil phosphorus availability alters the correlations between root phosphorus-uptake rates and net photosynthesis of dominant C3 and C4 species in a typical temperate grassland of Northern China.

Phosphorus (P) fertilization can alleviate a soil P deficiency in grassland ecosystems. Understanding plant functional traits that enhance P uptake can improve grassland management. We measured impacts of P addition on soil chemical and microbial properties, net photosynthetic rate (Pn ) and nonstructural carbohydrate concentrations ([NSC]), and root P-uptake rate (PUR), morphology, anatomy, and exudation of two dominant grass species: Leymus chinensis (C3 ) and Cleistogenes squarrosa (C4 ). For L. chinensis, PUR and Pn showed a nonlinear correlation. Growing more adventitious roots compensated for the decrease in P transport per unit root length, so that it maintained a high PUR. For C. squarrosa, PUR and Pn presented a linear correlation. Increased Pn was associated with modifications in root morphology, which further enhanced its PUR and a greater surplus of photosynthate and significantly stimulated root exudation (proxied by leaf [Mn]), which had a greater impact on rhizosheath micro-environment and microbial PLFAs. Our results present correlations between the PUR and the Pn of L. chinensis and C. squarrosa and reveal that NSC appeared to drive the modifications of root morphology and exudation; they provide more objective basis for more efficient P-input in grasslands to address the urgent problem of P deficiency.

Effects of different artificial photosynthetically active radiation (PAR) sources and intensity on the growth and nutrient uptake in Ulva prolifera and Neopyropia yezoensis

Fluorescent lamps and semiconductor light-emitting diodes (LEDs) lamps are commonly used as artificial light sources in the indoor algae cultivation system. In this study, we tested the effect of two types of fluorescent lamps (T8 and T5) and white LED lamp on the growth, photosynthesis, and nutrient uptake rates of Neopyropia yezoensis and Ulva prolifera under three photosynthetically active radiation (PAR) conditions (80, 150 and 300 μmol photon m2 s−1). White LED and T8 fluorescent light induced the highest and the lowest growth rates, respectively, in both species under each PAR. The effect of T5 fluorescent light on growth rate depends on the species and PAR. Interestingly, the T8 fluorescent light significantly increased the uptake rate of phosphorus under all PARs and nitrogen uptake rate was enhanced under 150 μmol photon m2 s−1 in U. prolifera, which was not observed in N. yezoensis. Our results suggest that white LED lamp is a more economical and efficient artificial light source than fluorescent lamps because of their highest enhancement of growth. The optimal PAR of T5 fluorescent light for growth is lower than T8 fluorescent light in the cultivation of U. prolifera. T8 fluorescent increases phosphorous uptake rate in U. prolifera.

The impact of pH on the anaerobic and aerobic metabolism of Tetrasphaera-enriched polyphosphate accumulating organisms

Members of the genus Tetrasphaera are putative polyphosphate accumulating organisms (PAOs) that have been found in greater abundance than Accumulibacter in many full-scale enhanced biological phosphorus removal (EBPR) wastewater treatment plants worldwide. Nevertheless, previous studies on the effect of environmental conditions, such as pH, on the performance of EBPR have focused mainly on the response of Accumulibacter to pH changes. This study examines the impact of pH on a Tetrasphaera PAO enriched culture, over a pH range from 6.0 to 8.0 under both anaerobic and aerobic conditions, to assess its impact on the stoichiometry and kinetics of Tetrasphaera metabolism. It was discovered that the rates of phosphorus (P) uptake and P release increased with an increase of pH within the tested range, while PHA production, glycogen consumption and substrate uptake rate were less sensitive to pH changes. The results suggest that Tetrasphaera PAOs display kinetic advantages at high pH levels, which is consistent with what has been observed previously for Accumulibacter PAOs. The results of this study show that pH has a substantial impact on the P release and uptake kinetics of PAOs, where the P release rate was >3 times higher and the P uptake rate was >2 times higher at pH 8.0 vs pH 6.0, respectively. Process operational strategies promoting both Tetrasphaera and Accumulibacter activity at high pH do not conflict with each other, but lead to a potentially synergistic impact that can benefit EBPR performance.

Comparison on biological nutrient removal and microbial community between full-scale anaerobic/anoxic/aerobic process and its upgrading processes

A comparative study was conducted for the anaerobic/anoxic/aerobic (AAO) process and its two upgrading processes, five-stage Bardenpho and AAO coupling moving bed bioreactors (AAO + MBBR), using long-term operation data of six full-scale wastewater treatment plants. The three processes all had good COD and phosphorus removal performance. The reinforcing effects of carriers on nitrification were moderate at full-scale applications, while the Bardenpho was advantageous in nitrogen removal. The AAO + MBBR and Bardenpho processes both had higher microbial richness and diversity than the AAO. The AAO + MBBR favored bacteria to degrade complex organics (Ottowia and Mycobacterium) and to form biofilms (Novosphingobium), and preferentially enriched denitrifying phosphorus-accumulating bacteria (DPB) (norank_o__Run-SP154) with the highest anoxic to aerobic phosphorus uptake rates of 65.3 % − 83.9 %. The Bardenpho enriched bacteria tolerant to varied environments (Norank_f__Blastocatellaceae, norank_o__Saccharimonadales, and norank_o__SBR103), and was more suitable for the upgrading of the AAO because of its excellent pollutant removal performance and flexible operation mode.

Bioaugmentation with Tetrasphaera to improve biological phosphorus removal from anaerobic digestate of swine wastewater

Tetrasphaera-enhanced biological phosphorus removal (T-EBPR) was developed by augmenting conventional EBPR (C-EBPR) with Tetrasphaera to improve phosphorus removal from anaerobic digestate of swine wastewater. At influent total phosphorus (TP) concentrations of 45–55 mg/L, T-EBPR achieved effluent TP concentration of 4.17 ± 1.02 mg/L, 54 % lower than that in C-EBPR (8.98 ± 0.76 mg/L). The enhanced phosphorous removal was presumably due to the synergistic effect of Candidatus Accumulibacter and Tetrasphaera occupying different ecological niches. Bioaugmentation with Tetrasphaera promoted the polyphosphate accumulation metabolism depending more on the glycolysis pathway, as evidenced by an increase in intracellular storage compounds of glycogen and polyhydroxyalkanoates by 0.87 and 0.34 mmol C/L, respectively. The enhanced intracellular storage capacity was coincidentally linked to the increase in phosphorus release and uptake rates by 1.23 and 1.01 times, respectively. These results suggest bioaugmentation with Tetrasphaera could be an efficient way for improved phosphorus removal from high-strength wastewater.

The growth and lipid accumulation of Scenedesmus quadricauda under nitrogen starvation stress during xylose mixotrophic/heterotrophic cultivation.

In order to conquer the block of high cost and low yields which limit to realize the commercialization of microalgal biodiesel, the mixotrophic and heterotrophic cultivation of Scenedesmus quadricauda FACHB-1297 fed on xylose was separately studied employing six forms of media: phosphorus sufficient, phosphorus restricted, and phosphorus starvation were combined with nitrogen sufficient and nitrogen starvation conditions. The maximum lipid content (about 41% of dry weight) was obtained on the 5th day (heterotrophic cultivation) and 8th day (mixotrophic cultivation) under the nitrogen starved and phosphorus sufficient (N0&P) conditions, which was about twofold in comparison to the final lipid content on the sufficient nitrogen condition (control). Under mixotrophic and heterotrophic modes, the highest lipid production was achieved in the N0&P trial, with the value of 274.96mg/L and 193.77mg/L, respectively. Xylose utilization rate of 30-96% under heterotrophic modes was apparently higher than that of 20-50% in mixotrophic modes. In contrast, phosphorus uptake rate of 100% under mixotrophic cultivation was significantly more than that of 60-90% in heterotrophic cultivation. Furthermore, under the condition of heterotrophic cultivation using xylose as a carbon source, the phosphorus had a positive impact on microalgae cell synthesis and the lipid content enhanced with the augmentation in phosphorus concentrations. We suggested that sufficient phosphorus should be supplied for obtaining higher microalgal lipid production in the lack of nitrogen under xylose heterotrophic/mixotrophic condition. This was a highly effective way to obtain efficient microalgae lipid production.

Redox environment inducing strategy for enhancing biological phosphorus removal in a full-scale municipal wastewater treatment plant

Phosphorus removal from wastewater is crucial for limiting water eutrophication. However, due to improper operating conditions, tremendous phosphorus removal chemicals addition or low C/N ratio in the influent, biological phosphorus removal (BPR) has been regarded as a difficult issue in real full-scale municipal wastewater treatment plants (WWTPs), especially in the membrane bioreactor (MBR) plants with long sludge retention time. Therefore, application of effective enhanced biological phosphorus removal (EBPR) technologies in WWTPs is of great significance to improve the BPR efficiency, reduce chemicals consumption and operating cost. Favorable redox environment, characterized by ORP is important for the growth and enrichment of phosphate-accumulating organisms (PAO), which is mainly responsible for BPR. In this study, a redox environment inducing strategy for EBPR was taken in a real full-scale MBR-WWTP (treatment capacity of 2 × 106 m3/d). The results indicated that the phosphorus release and uptake rate were rather low in the biochemical tank, which reflected the low phosphate-accumulating organisms (PAO) activity and poor BPR efficiency. This problem may be due to inappropriate redox environment, inhibition by phosphorus removal chemicals or low C/N in the influent. After EBPR, the contribution percentage of BPR increased by up to 18% and chemicals dosage reduced by up to 60%. Furthermore, the relative abundance of PAO (Dechloromonas, Thauera and OLB12) was significantly increased in anaerobic tank (4.62, 1.33 and 1.18%), in anoxic tank (4.85, 1.93 and 0.88%) and in oxic tank (5.17, 1.71 and 0.84%) for appropriate redox environment and relieved inhibition by less dosage of phosphorus removal chemicals. In addition, bacteria related to COD degradation and nitrogen removal were also enriched. The simultaneous enhancement of biological phosphorus removal, carbon removal and nitrogen removal was successfully realized in this research, which indicated that the strategy was effective in real large-scale WWTPs.

Combined toxic effects of enrofloxacin and microplastics on submerged plants and epiphytic biofilms in high nitrogen and phosphorus waters

With the wide application of plastic products, microplastic pollution has become a major environmental issue of global concern. Microplastics in aquatic environments can interact with organic pollutants, causing a combined effect on submerged macrophytes. This study investigated the response mechanisms of the submerged plant Myriophyllum verticillatum and epiphytic biofilm to the antibiotic enrofloxacin, microplastics, and their combined exposure in a high nitrogen and phosphorus environment. The results indicated that Myriophyllum verticillatum was not sensitive to enrofloxacin of 1 mg L−1, while 10 and 50 mg L−1 enrofloxacin inhibited the uptake of nitrogen and phosphorus by the plants, as well as triggered oxidative stress in the plant leaves, causing irreversible damage to the plant cells. In addition, enrofloxacin altered the structure of the leaf epiphytic biofilm community. Interestingly, 1, 5, and 20 mg L−1 microplastics had no significant effect on the plant, while they facilitated the aggregation of microorganisms, increasing the abundance of the leaf epiphyte biofilm. The combination of enrofloxacin and microplastics induced a synergistic effect on Myriophyllum verticillatum. Specifically, the rate of nitrogen and phosphorus uptake by the plant was reduced, the content of photosynthetic pigments decreased, and antioxidant enzyme activity was further increased. In addition, the diversity of the leaf epiphytic biofilm community was similar to the single enrofloxacin exposure. These results demonstrated the differences between single and combined exposures and provided a new theoretical basis to evaluate the harmful effects of enrofloxacin and microplastics on submerged macrophytes.

Phosphorus Removal from Aerobic Granular Sludge: Proliferation of Polyphosphate-Accumulating Organisms (PAOs) under Different Feeding Strategies

Aerobic granular sludge (AGS) is known for high phosphorus removal from wastewaters, and phosphorus can be recovered from high phosphorus-containing waste sludge granules. This study aimed at determining the feeding strategy that provides the best performance in terms of the proliferation of polyphosphate-accumulating organisms (PAOs) and phosphorus removal. Using three AGS bioreactors, this study compared phosphorus removal and the proliferation dynamics of PAOs under three different feeding strategies: anaerobic slow feeding (R1), pulse feeding + anaerobic mixing (R2), and pulse feeding (R3). Results indicate that R1 and R2 achieved significantly higher phosphorus removal (97.6 ± 3% for R1 and 98.3 ± 1% for R2) than R3 (55 ± 11%). The anaerobic slow feeding procedure (R1) achieved the highest specific phosphorus release rate (SPRR) and specific phosphorus uptake rate (SPUR) as compared to the other two feeding conditions. 16S ribosomal ribonucleic acid (rRNA) gene sequencing assay of the microbial community for the three feeding strategies indicated that although the feeding strategy impacted reactor performance, it did not significantly alter the microbial community. The bacteria community composition maintained a similar degree of diversity. Proteobacteria, Bacteroidetes, and Verrucomicrobia were the dominant bacterial phyla in the system. Dominant PAOs were from the class Betaproteobacteria and the genera Paracoccus and Thauera. Glycogen-accumulating organisms were significantly inhibited while other less-known bacteria such as Wandonia and Hyphomonas were observed in all three reactors.

HPLC and 32P‐radiolabeling method for quantification of microbial adenylate concentrations and turnover rates in seawater

AbstractWe optimized a high throughput method to quantify turnover rates of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) in marine microbes from simultaneous measures of the respective stocks and phosphorylation rates. We combined a microbial adenylate extraction method using boiling 20 mM Tris buffer with purification and analysis by high pressure liquid chromatography optimized to quantify these intracellular adenylate concentrations in marine microbes. Additionally, we incorporated radiolabeled phosphate (32Pi) incubations to quantify phosphorus (P) uptake rates and the phosphorylation rates for these adenylate compounds in microbial cells. With this method, we can directly assess the variations in microbial growth rates, metabolic turnover rates, energy charge, and adenylate storage. We applied and validated this method application with environmental samples from Biscayne Bay, Florida, and quantified adenylate turnover times of 12, 15, and 73 min, for ATP, ADP, and AMP, respectively. Future incorporation of this method into experiments and geographic surveys across marine environments will allow for direct assessments of changes in microbial metabolic activity in relation to other ecological variables.

Review of Evaluation and Valuation Methods for Cetacean Regulation and Maintenance Ecosystem Services With the Joint Cetacean Protocol Data

Cetaceans provide a range of ecosystem services of value to anthropogenic interests. Following the Common International Classification of Ecosystem Services (CICES) these are categorised as regulation and maintenance, provisioning, and cultural values. This study focuses on those of importance to climate change mitigation through regulation and maintenance. Under regulation and maintenance, cetaceans can store, transport, and influence stocks of carbon through: climate regulation through carbon sequestration, enhanced biodiversity and ecosystem potential, and enhanced primary productivity. ‘Climate regulation through carbon sequestration’ can be quantified as carbon fixation through living biomass and ‘whale-falls’. Cetacean populations store significant stocks of carbon in living biomass. After death, sinking whale carcasses, ‘whale-falls’, provide a significant transfer of biomass and nutrients to benthic sediments and support deep sea ecosystems. During their lifespan, cetaceans also disperse nutrients through feeding and excretion both horizontally through the ‘whale-conveyor’ and vertically through the ‘whale pump’. As nutrient limitations hinder phytoplankton growth, these processes can be quantified as the increased potential of phytoplankton carbon fixation from cetacean driven nutrient cycling. Enhanced biodiversity, ecosystem potential, and primary productivity can be quantified as carbon fixation through nutrient cycling. This study reviews the evaluative and valuative techniques used in cetacean ecosystem service research and adapts and applies them to the Joint Cetacean Protocol (JCP) data which details cetacean abundance and distribution in Europe. They are then reviewed with regards to their robustness, application in markets, and in decision making processes. Cetacean populations are estimated to contain 2 Mt C, cycle 60,000 t N yr-1, and impact carbon fluxes by as much as 22 Mt C yr-1 in the survey area. The values highlight key areas for cetacean conservation: the Outer Hebrides, west of south Wales, around the Isle of Man, to the east of England, and to the north-east of the Shetland Islands. There is, however, large uncertainty in the evaluative processes used; nutrient cycling models presented in this study don’t capture removal of excess nutrients, or the values of enhanced biodiversity and ecosystem potential. As such, they are not sufficiently robust to quantify market values but highlight key areas for future research on climate change mitigation through conservation. Key areas of future research include phytoplankton uptake rates of nitrogen and phosphorus in nutrient limited waters, quantification of ‘enhanced biodiversity and ecosystem potential’, and nutrient removal from coastal waters.

Effect of granular matrix on functional flora in EBPR system

Enhanced biological phosphorus removal (EBPR) is a very mature phosphorus removal technology, but there is still a problem of unstable treatment effect in the operation of actual wastewater treatment plants, so the study on the effect of phosphorus removal performance still needs to be further studied. Because there are a lot of granular matrix in municipal wastewater, it occupies an important proportion in the total Chemical Oxygen Demand (COD) of municipal wastewater, and the fluctuation of granular matrix concentration is also related to the instability of phosphorus removal effect. Therefore, it is of practical guiding significance to further explore the influence of granular matrix on the functional bacteria community of phosphorus removal in the enhanced biological phosphorus removal system. The acetic acid was used as a carbon source to enrich and cultivate phosphorus accumulating bacteria. After the enrichment and the system was stable, soluble starch was added into the water to study the effects of granular matrix on phosphorus removal performance and functional bacteria community in EBPR system. The results showed that acetic acid was beneficial to the proliferation of phosphorus-accumulating bacteria in the enrichment stage, and the phosphate removal rate of the system could reach more than 99%. After the system is stabilized, granular matrix with different concentrations is added to the system in three stages, and the phosphate removal rate of the system gradually decreases. With the increasing of granular matrix concentration in the influent, the phosphorus removal performance of sludge decreased gradually, the maximum phosphorus release rate and maximum phosphorus uptake rate of sludge decreased, and the acetic acid utilization rate ΔP/ΔHAc value also decreased. Fluorescence in situ hybridization was used to measure the changes of functional bacteria in activated sludge under different conditions. With the increase of the concentration of soluble starch, the proportion of PAOs gradually decreased, and the proportion of GAOs gradually increased. Granular matrix exists in the internal of floc sludge and cannot be utilized by PAOs, which results in inhibition of the growth of PAOs and weakened activity. This indicates that the higher concentration of granular matrix will lead to a decrease in the proportion of PAOs in EBPR system, and then lead to a decrease in the phosphorus removal activity of activated sludge, and ultimately reduce the phosphorus removal effect of EBPR system.

Investigating the use of anaerobically stored carbon in post‐anoxic denitrification

Significant methanol savings are hypothesized to result from anaerobic storage of internal carbon that is used for post‐anoxic denitrification. An investigation into this internal carbon‐driven denitrification was performed via a series of batch tests using biomass from Hampton Roads Sanitation District's (HRSD's) water resource recovery facilities (WRRFs): the Virginia Initiative Plant (VIP), Nansemond Plant (NP), and Army Base (AB) Treatment Plant. Internal carbon specific denitrification rates (SDNRs) increased during winter, by as much as 1 mg N/g MLVSS/h for VIP. Increasing the aeration time by 2–4 h lowered the SDNR by an average of 0.21–0.35 mg N/g MLVSS/h. No internal carbon denitrification was observed for biomass from non‐nitrifying/denitrifying, biological phosphorus removal (bio‐P) WRRFs. The increase in internal carbon SDNRs when the anaerobic acetate dose increased from 20 to 100 mg COD/L ranged from 0.06 to 0.28 mg N/g MLVSS/h. Higher phosphorus uptake rates were found to correlate to higher internal carbon SDNRs, but no significant post‐anoxic P uptake was observed. The first steps are taken towards developing a strategy for full‐scale implementation of this relatively novel type of denitrification by evaluating how some factors affect its occurrence.Practitioner Points Significant methanol savings at a full‐scale facility may result from use of internally stored carbon for post‐anoxic denitrification.Short aerobic HRTs and high anaerobic zone VFA loading increase the post‐anoxic internal carbon‐driven denitrification.Non‐nitrifying, bio‐P biomass is not capable of internal carbon‐driven denitrification.Internal carbon‐driven denitrification is correlated with the activity of polyphosphate accumulating organisms.

Assessing the impacts of urbanization on stream ecosystem functioning through investigating litter decomposition and nutrient uptake in a forest and a hyper-eutrophic urban stream

Rapid urbanization significantly affects freshwater systems by interfering with important ecological functions. The responses of different ecosystem functions in urban streams and their potential ecological effects remain largely unknown, impeding their management and restoration in many cases. In this study, we simultaneously assessed two important ecosystem functions, litter decomposition and nutrient uptake, and investigated the associated microbial and benthic macroinvertebrate communities in two subtropical streams (i.e., a forest headwater stream as a reference and an urban stream that was hyper-eutrophic). Litter decomposition was estimated using litter bags with two mesh sizes (i.e., 50 μm and 2 mm) and two leaf species with different qualities (i.e., Alangium chinense and Machilus leptophylla), with a total of 96 litter bags. Nitrogen (N) and phosphorus (P) uptake rates were measured in situ based on the spiraling model. We found that the decomposition rate of A.chinense was approximately seven times that of M. leptophylla in both streams. Moreover, in the urban stream, the litter decomposition rate (0.004 day−1) was one-third that of the forest stream (0.013 day−1), regardless of the litter species. Macroinvertebrates strongly contributed to litter decomposition in the forest stream, where decomposition rates were 1.8-fold higher in the coarse mesh compared to the fine mesh bags, while they had a negligible role in the urban stream (no significant difference between the two mesh bags). P uptake was higher (85-fold) and N uptake was lower (0.13-fold) in the urban compared to forest stream. Litter decomposition and nutrient uptake exhibit decoupled response. These findings show that litter decomposition by kcoarse/kfine metrics and the uptake of N and P are complementary and should be considered in the management and restoration of urban stream ecosystems.