Exploring efficient strategies for air quality improvement in China based on its regional characteristics and interannual evolution of PM2.5 pollution.

Fine particulate matter (PM2.5) harms human health and hinders normal human life. Considering the serious complexity and obvious regional characteristics of PM2.5 pollution, it is urgent to fill in the comprehensive overview of regional characteristics and interannual evolution of PM2.5. This review studied the PM2.5 pollution in six typical areas between 2014 and 2022 based on the data published by the Chinese government and nearly 120 relevant literature. We analyzed and compared the characteristics of interannual and quarterly changes of PM2.5 concentration. The Beijing-Tianjin-Hebei region (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD) made remarkable progress in improving PM2.5 pollution, while Fenwei Plain (FWP), Sichuan Basin (SCB) and Northeast Plain (NEP) were slightly inferior mainly due to the relatively lower level of economic development. It was found that the annual average PM2.5 concentration change versus year curves in the three areas with better pollution control conditions can be merged into a smooth curve. Importantly, this can be fitted for the accurate evaluation of each area and provide reliable prediction of its future evolution. In addition, we analyzed the factors affecting the PM2.5 in each area and summarize the causes of air pollution in China. They included primary emission, secondary generation, regional transmission, as well as unfavorable air dispersion conditions. We also suggested that the PM2.5 pollution control should target specific industries and periods, and further research need to be carried out on the process of secondary production. The results provided useful assistance such as effect prediction and strategy guidance for PM2.5 pollution control in Chinese backward areas.

[Determination of 10 mycotoxin contaminants in Panax notoginseng by ultra performance liquid chromatography-tandem mass spectrometry].

To ensure the quality and safety of Panax notoginseng, a method for the simultaneous determination of 10 mycotoxins in Panax notoginseng was developed using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The sample was extracted with acetonitrile and purified by HLB multifunction cleanup column. The separation was performed on a Phenomenex Kinetex XB-C18 column by gradient elution using methanol and 5 mmol·L(-1) ammonium acetate as mobile phase. The targeted compounds were detected in MRM mode by mass spectrometry with electrospray ionization (ESI) source operated in both positive and negative ionization modes. The linear relationships of the 10 mycotoxins were good in their respective linear ranges. The correlation coefficients (r) ranged from 0.9981 to 1.0000. The LOQs of the 10 mycotoxins were between 0.15 and 8.6 µg·kg(-1). The average recoveries ranged from 73.8% to 107.0% with relative standard deviations (RSDs) of 0.10%-10.9%. The results demonstrated that the proposed method was sensitive and accurate, and suitable for the mycotoxins quantification in Panax notoginseng.

[Particle settling characteristics of alcohol precipitation mixture of Paeoniae Radix rubra extract and models establishment of settling velocity].

OBJECTIVE: To understand the particle settling characteristics of alcohol precipitation mixture of Paeoniae Radix rubra extract and establish models of the sedimentation rate. METHODS: Focusing on the particle settling characteristics such as particle settling curve, particle settling velocity (PSV), particle volume index (PVI), the particle settling process of alcohol precipitation was investigated. The effect of three key process factors on the settling process was discussed and mathematical models for describing the particle settling velocity were developed. RESULTS: Controlling of higher final alcohol concentration, higher density of Paeoniae Radix rubra extract, or lower initial alcohol concentration, was conducive to settlement of alcohol precipitation particles. In the constant speed phase, an empirical calculation formula of v(0) was established, with both the variables PSV and PVI (v(0)=-0.236PSV+0.022PVI+7.521). Another developed model was applied to predict the settling velocity in decelerated phase and the simulation was very good [v=k(1-n(1)X)(4)exp(-n(2)X)/X]. CONCLUSION: The results of this work will contribute to a better control and optimization of alcohol precipitation process, and help to implementation of accuracy control in the manufacture of botanical medicines.

Revealing hydrodynamics and energy efficiency of mixing for high-solid anaerobic digestion of waste activated sludge.

Anaerobic digestion is a feasible and promising technique to deal with emerging waste activated sludge issues. In this work, the hydrodynamics and digestion performance of horizontal anaerobic systems equipped with double-bladed impeller and ribbon impeller were investigated. Simulation using computational fluid dynamics technique visually showcased the favorable mixing status implementing ribbon impeller. The mixing modes were considered as the major motivation for the difference of mixing efficiencies. Tracing experiment indicated that the minimum thorough mixing time with ribbon impeller was 20 min at a rotation speed of 50 rpm, whereas it was 360 min for the double-bladed impeller under similar conditions. The superior mixing performance of ribbon impeller resulted in better anaerobic digestion and energy efficiency outputs. The digester employing ribbon impeller obtained an ultimate biogas yield of 340.38 ± 15.91 mL/g VS (corresponding methane yield of 210.34 ± 7.55 mL/g VS) and produced a surplus energy of 16.23 ± 0.76 MJ/(m3·d). This study thus ascertained that ribbon impeller was proficient for high-solid anaerobic digestion and it will prominently benefit future system designs.

[Process Control and Operation Optimization of PN-SAD Coupling Process Based on SBR-ABR].

This study uses three different operating phases for a sequencing batch reactor (SBR) combined with an anaerobic baffled reactor (ABR) to determine the effect of deep nitrogen and carbon removal by the "partial nitrification-anaerobic ammonium oxidation combined denitrification" (termed PN-SAD) reaction. The effluent of the SBR (NO2--N/NH4+-N ratio range of 1-1.32) was accessed directly to the single compartment ABR anammox system in phase Ⅰ. The results showed that although the anammox reaction was stable, the combined process total nitrogen (TN) removal efficiency was<80%, and the TN concentration of effluent was~20 mg·L-1. In order to increase the denitrification function in the ABR, denitrifying sludge was added to the third compartment of the ABR in phase Ⅱ. We found that the TN removal efficiency of the coupling reaction was still low. An organic carbon source should be supplied in the latter stage of anammox if deep nitrogen removal is required. Therefore, in phase Ⅲ, the effluent of the SBR (NO2--N/NH4+-N ratio of ~5) was mixed with the partial raw water (mixed water NO2--N/NH4+-N ratio of ~1.4; C/N ratio of 2.5). The mixed water was connected to the single compartment of the ABR. The PN-SAD system not only achieved a good matrix ratio at the anammox stage, but also provided a good carbon source for denitrification. The chemical oxygen demand (COD) concentration of the effluent in the whole process was 50 mg·L-1, the TN concentration of the effluent was<6 mg·L-1, and the TN removal efficiency was 95%. We conclude that the stable operation of the combined PN-SAD reaction provides the basis for deep nitrogen and carbon removal using the combined SBR-ABR process.

[Characteristics of ANAMMOX Granular Sludge and Differences in Microbial Community Structure Under Different Culture Conditions].

Anaerobic ammonium oxidation (ANAMMOX) granular sludge was cultured during different operating conditions by an expanded granular sludge bed (EGSB) reactor and up-flow anaerobic sludge bed (UASB) reactors, and the characteristics of the granular sludge and microbial community were compared. The results showed that the flocculent ANAMMOX sludge can be granulated after being operated for 384 days by the EGSB and UASB reactors. The average particle size reached 1.17 mm and 1.21 mm, respectively. The particle size ratio of each range (<0.2, 0.2-1.5, 1.5-3, and>3 mm) was 6.06%, 60.05%, 25.25%, and 8.64% in the EGSB reactor, and 7.40%, 58.90%, 32.04%, and 1.66% in the UASB reactor, respectively. The results of scanning electron microscopy showed that the bacterial flora during different operating conditions were mainly Brevibacterium and Cocci aggregates. High-throughput sequencing results showed that the Shannon index of the EGSB reactor was 7.52, higher than the 7.18 of the UASB reactor on day 384; Proteobacteria was the main phylum of the sludge at each stage, and Planctomycetes increased from 3.30% to 12.30% in the EGSB reactor and 13.30% in the UASB reactor on day 384. The main ANAMMOX genera in the EGSB reactor were Candidatus Brocadia, accounting for 7.53%, followed by Candidatus Kuenenia accounting for 1.61%, whereas in the UASB reactor, Candidatus Kuenenia was the dominant anaerobic ammonia genus, accounting for 7.54%, followed by Candidatus Brocadia, which accounted for 3.69%. The proportion of dominant species was related to the change in environmental factors. The proportion of Candidatus Brocadia was positively correlated with the up-flow rate and nitrogen removal rate (NRR), but negatively correlated with hydraulic retention time (HRT). Candidatus Kuenenia was positively correlated with nitrogen removal efficiency (NRE), NRR, and HRT, but negatively correlated with the up-flow rate.

[Effect of C/N and Sludge Concentration on the pH-Regulated Nitrosation System].

pH is one of the most important means of control for the realization and stability of the nitrosation system. To study the change rule of pH values of the nitrosation system and the influence of pollution removal and transformation at different pH under the conditions of different C/N (0, 1, 2, 3,4) and sludge concentrations (sludge amount:water content was 1:6, 1:3, 1:1), batch tests were conducted with tapered bottles using sodium acetate as the carbon source and inoculated with mature nitrosation sludge. The results showed that the higher the C/N, the higher the pH increment and the denitrification efficiency at the same sludge concentration. At the same C/N, a higher sludge concentration corresponded to a smaller pH increment but a higher denitrification efficiency. The removal and transformation of carbon and nitrogen was highly correlated with pH changes in the reaction system, and the denitrification and nitrosation reactions were in sequence. Throughout the operational period of the system, as pH increased, the specific organic matter removal rate was 7-16 times as much as when pH decreased. However, as pH decreased, the specific ammonia oxidation rate (SAOR) was 1-20 times that of when pH increased. When pH was less than 6.1, the system lost its ability to oxidize ammonia-nitrogen. The highest removal efficiency of carbon and nitrogen in the system was achieved when C/N was 4. Ammonia transformation 80% COD removal at the three sludge concentrations took 480, 350, and 300 min, respectively. Under different conditions, the proportion of nitrosation in the system remained above 50% and the concentration of NO3--N remained below 5 mg·L-1, which indicated that the system was dominated by nitrosation.

[Effect of Substrate Concentration on SAD Collaborative Nitrogen and Carbon Removal Efficiency in an ABR Reactor].

In order to solve the problem of declining total nitrogen (TN) removal caused by anaerobic ammonium oxidation (ANAMMOX) and the suppression of organic matter for ANAMMOX, the anaerobic baffled reactor (ABR), inoculating ANAMMOX sludge and anaerobic sludge from a municipal WWTP, was selected to construct system of ANAMMOX coupled denitrification (SAD) by the control of different substrate concentration. The SAD was constructed to study the effects of different influent substrates (COD, NO2--N, NH4+-N) on the performance of nitrogen and carbon removal in the coupled system and pollutant removal rules. The results showed that the coupling reaction was achieved in the ABR reactor and the inhibitory effect of organic compounds on anaerobic ammonium oxidation bacteria (AAOB) was relieved. When influent concentrations of COD, NO2--N, and NH4+-N were 260, 185, and 100 mg·L-1, respectively, which equates to a ratio of 2.6∶1.85∶1, the concentrations of these substances in the effluent decreased to 10, 1.0, and 0.9 mg·L-1, respectively. The TN removal rate reached 99%, hence stable system operation and ultra-low emissions of carbon and nitrogen pollutants were achieved. Under different conditions of substrate concentrations and ratios, the targeted pollutants were generally eliminated in the first compartment, in which the removal rate reached higher than 75%, and ANAMMOX held the dominant position in the SAD coupled system.

[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.

[Priming effect of biochar on the minerialization of native soil organic carbon and the mechanisms: A review.] / ç”Ÿç‰©ç‚­å¯¹åœŸå£¤æœ‰æœºç¢³çŸ¿åŒ–çš„æ¿€å‘æ•ˆåº”åŠå ¶æœºç†ç ”ç©¶è¿›å±•.

In recent years, studies on carbon sequestration of biochar in soil has been in spotlight owing to the specific characteristics of biochar such as strong carbon stability and well developed pore structure. However, whether biochar will ultimately increase soil carbon storage or promote soil carbon emissions when applied into the soil? This question remains controversial in current academic circles. Further research is required on priming effect of biochar on mineralization of native soil organic carbon and its mechanisms. Based on the analysis of biochar characteristics, such as its carbon composition and stability, pore structure and surface morphology, research progress on the priming effect of biochar on the decomposition of native soil organic carbon was reviewed in this paper. Furthermore, possible mechanisms of both positive and negative priming effect, that is promoting and suppressing the mineralization, were put forward. Positive priming effect is mainly due to the promotion of soil microbial activity caused by biochar, the preferential mineralization of easily decomposed components in biochar, and the co-metabolism of soil microbes. While negative priming effect is mainly based on the encapsulation and adsorption protection of soil organic matter due to the internal pore structure and the external surface of biochar. Other potential reasons for negative priming effect can be the stabilization resulted from the formation of organic-inorganic complex promoted by biochar in the soil, and the inhibition of activity of soil microbes and its enzymes by biochar. Finally, future research directions were proposed in order to provide theoretical basis for the application of biochar in soil carbon sequestration.

[Start-up and Characteristics of the Microbial Community Structure of ANAMMOX].

An anaerobic ammonium oxidation (ANAMMOX) reactor was successfully started up in 17 days, with the up-flow anaerobic sludge blanket (UASB) reactor being seeded with mixed anaerobic sludge from laboratory cultures with an ANAMMOX function and aerobic activated sludge from a municipal sewage treatment plant in a volume ratio of 1:2. The processes could be divided into two phases of hydrolysis, enhanced and steady. Anaerobic ammonium oxidation bacteria (AAOB) were enriched by improving the reactor volume load gradually after the steady phase. When the volume load increased from 0.10 kg·(m3·d)-1 to 0.44 kg·(m3·d)-1, the removal of total nitrogen (TN) also increased from 0.09 kg·(m3·d)-1 to 0.42 kg·(m3·d)-1. The color of the sludge changed from a light red that deepened gradually in the UASB reactor. At that time, the proportion of the sludge particle size greater than 0.2 mm increased from 10.90% to 38.37%.The sludges from the inoculation phase and from the phase when the volume load was increasing were analyzed by high-throughput sequencing, indicating that Chloroflexi, Proteobacteria, WWE3, Actinobacteria, Planctomycetes, and so on were the dominant species. The proportion of Proteobacteriain the denitrification bacteria was gradually reduced from 21.60% to 14.20% with an increase in the degree of AAOB enrichment, while the Planctomycetes increased from 0.73% to 15.50%. Candidatus Brocadia, Candidatus Jettenia, and Candidatus Kuenenia were the main species of Planctomyceteswhen the volume load increased to 0.44 kg·(m3·d)-1 in the reactor, and the Candidatus Brocadia was the main species of AAOB, which accounted for 13.40%.

[Characteristics of Microbial Community in Each Compartment of ABR ANAMMOX Reactor Based on High-throughput Sequencing].

In order to investigate the characteristics of microbial community in each compartment of ABR anammox reactor, a five-compartment ABR reactor was used to analyze the microbial community by Miseq High-throughput Sequencing during the steady operational process. The results indicated that the denitrifying bacteria coexisted in the reactor, such as Proteobacteria, Planctomycete, and Nitrospirae bacteria, and the percentages of these three microbial populations in the sludge were 11.66%-20.28%, 2.18%-7.94% and 0.19%-6.30%, respectively. In addition, there were four dominant genera in the phylum Proteobacteria:Rhodoplanes, Dok59, Rubrivivax and Bdellovibrio. Furthermore, Candidatus brocadia and Candidatus kuenenia were the main genera in the phylum Planctomycete. The color of sludge in the five compartments, in turn, varied from red to black. In addition, the biodiversity index of Chao, ACE, Shannon and Simpson indicated that the richness and diversity of microbial community increased gradually, and at the same time, the relative abundance of Proteobacteria increased while that of Planctomycetes gradually decreased. The above conclusion was consistent with the laws of substrate degradation and enrichment of functional microorganisms.

[Start-up Performance of ANAMMOX Enrichment with Different Inoculated Sludge in Anaerobic Baffled Reactor].

Two anaerobic baffled reactors (ABR) were compared for anaerobic ammonium oxidation (ANAMMOX) enrichment using synthetic wastewater with different inoculated sludge, the mixed anaerobic flocculent sludge/granular sludge (R1) and anaerobic activated sludge (R2). The research showed the ANAMMOX activity occurred in both reactors allowing continuous removal of ammonium and nitrite, in which the ammonia and nitrite nitrogen loading was about 54.5-68.0 g (m3 x d)(-1), when maintaining the temperature at 30-35 degrees C, pH at 7.5 +/- 0.5 and HRT at 26 h. However, the ANAMMOX reaction was successfully started after 120 d and 125 d, respectively. The removal rules of the two reactors were basically similar, and the enrichment processes occurred in both reactors could be divided into 4 phases, which were sluggish phase, expressive phase, enhanced phase and steady phase. In the steady phase, the average removal rates of NH4+ -N, NO2- -N were higher than 90%, and the average removal load achieved 57.3-67.9 g x (m3 x d)(-1). Moreover, the ammonium removal load in R1 was slightly higher than that in R2. Additionally, more than 90% of nitrogen was dramatically removed in the first compartment of ABR. Meanwhile, the color of sludge gradually changed from brown, litter bed brown to black along with the flow direction, which was similar to the removal rule of nitrogen. In a word, the results showed the different inoculated sludge did not cause obvious differences in the starting rule and the removal characteristics of ANAMMOX reactor.

[Effect of Increasing Organic Loading Rate on the Formation and Stabilization Process of Aerobic Granular Sludge].

In order to evaluate the effect of organic loading rate ( OLR) on the formation of aerobic granular sludge (AGS), a lab-scale cylindrical SBR reactor (sodium acetate as carbon source) was constructed and inoculated with collected sewage sludge. The evolution of morphology, microbial activity and extracellular polymeric substances (EPS) characteristics of sludge samples in the reactor were recorded and analyzed. The results showed that AGS has the highest growth rate under the condition of 3. 20-4. 84 kg.(m3.d)-1 OLR, and a selective discharging strategy of the floccular sludge was suggested to maintain the predominance of AGS in reactor. The accumulated sludge concentration, SVI30, mean granule size, settling velocity and SOUR value of the AGS in steady-state operated SBR was 23. 9 g.L-1, 20 mL.g-1, 1. 4 mm, 102 m.h-1 and 50. 2 mg.(g.h)-1, respectively. The granulation process not only obviously changed the sludge appearance, but also significantly improved the microbial activity. Meanwhile, linear correlation was observed between the variation of protein/polysaccharide concentration and the granule size of AGS. Thus, variation of protein/ polysaccharide concentration of the EPS could be applied as an indicator for optimization of the cultivation method of AGS.

[Treatment effect of biological filtration and vegetable floating-bed combined system on greenhouse turtle breeding wastewater].

Unorganized discharge of greenhouse turtle breeding wastewater has brought several negative influences on the ecological environment in the rural area of Yangtze River Delta. Biological filtration and vegetable floating-bed combined system is a potential ecological method for greenhouse turtle breeding wastewater treatment. In order to explore the feasibility of this system and evaluate the contribution of vegetable uptake of nitrogen (N) and phosphorus (P) in treating greenhouse turtle breeding wastewater, three types of vegetables, including Ipomoea aquatica, lettuce and celery were selected in this study. Results showed the combined system had a high capacity in simultaneous removal of organic matter, N and P. The removal efficiencies of COD, NH4(+)-N, TN and TP from the wastewater reached up to 93.2%-95.6%, 97.2%-99.6%, 73.9%-93.1% and 74.9%-90.0%, respectively. System with I. aquatica had the highest efficiencies in N and P removal, followed by lettuce and celery. However, plant uptake was not the primary pathway for TN arid TP removal in the combined system. The vegetable uptake of N and P accounted for only 9.1%-25.0% of TN and TP removal from the wastewater while the effect of microorganisms would be dominant for N and P removal. In addition, the highest amounts of N and P uptake in I. aquatica were closely related with the biomass of plant. Results from the study indicated that the biological filtration and vegetable floating-bed combined system was an effective approach to treating greenhouse turtle breeding wastewater in China.

[Effect of pilot UASB-SFSBR-MAP process for the large scale swine wastewater treatment].

In this paper, a treatment process consisted of UASB, step-fed sequencing batch reactor (SFSBR) and magnesium ammonium phosphate precipitation reactor (MAP) was built to treat the large scale swine wastewater, which aimed at overcoming drawbacks of conventional anaerobic-aerobic treatment process and SBR treatment process, such as the low denitrification efficiency, high operating costs and high nutrient losses and so on. Based on the treatment process, a pilot engineering was constructed. It was concluded from the experiment results that the removal efficiency of COD, NH4(+) -N and TP reached 95.1%, 92.7% and 88.8%, the recovery rate of NH4(+) -N and TP by MAP process reached 23.9% and 83.8%, the effluent quality was superior to the discharge standard of pollutants for livestock and poultry breeding (GB 18596-2001), mass concentration of COD, TN, NH4(+) -N, TP and SS were not higher than 135, 116, 43, 7.3 and 50 mg x L(-1) respectively. The process developed was reliable, kept self-balance of carbon source and alkalinity, reached high nutrient recovery efficiency. And the operating cost was equal to that of the traditional anaerobic-aerobic treatment process. So the treatment process could provide a high value of application and dissemination and be fit for the treatment pf the large scale swine wastewater in China.

[Research progress in anammox-denitrification coupling process].

Anammox (anaerobic ammonium oxidation) is an important process of nitrogen cycle, with great potential for the practical use in removing nitrogen from the wastewater containing high concentration ammonium. However, the presence of high concentration organic carbon source is considered unfavorable to anammox. Coupling anammox and denitrification under the presence of organic carbon source could be a useful technique for removing both nitrogen and carbon. This paper reviewed the mechanisms of anammox-denitrification coupling process, functional microbial groups, initiation of the coupling process and its control, and related environmental affecting factors. The future research prospects and potential applications of anammox-denitrification coupling process in wastewater treatment were discussed.

Improving Anammox start-up with bamboo charcoal.

Three Upflow Anaerobic Sludge Blanket (UASB) reactors were compared for Anammox enrichment using synthetic wastewater with Spherical Plastic (SP) and Bamboo Charcoal (BC) addition, and without carrier (CK). After four months of operation, the Anammox activity occurred in all reactors allowing continuous removal of ammonium and nitrite. Ammonium and nitrite removal efficiencies were all higher than 98% in steady phase with the effluent concentrations below 1 mg L(-1). The start-up time could be shortened from 117 to 97 d in CK and SP reactor to 85 d in BC amendment reactor. Quantitative PCR (q-PCR) analyses indicated a significant increase in the number of Anammox bacteria in BC amended reactor as compared with CK and SP during the entire start-up periods. The copy numbers of Anammox of 16S rRNA gene in the reactor with BC amendment could reach up to 6×10(9)copies g(-1) Volatile Suspended Solids, around 22.5 times and 12.3 times greater than that in CK and SP reactor, respectively. BC addition could accelerate the start-up of Anammox and significantly increase the Anammox bacteria number.

[Periphyton and its application in water purification].

Periphyton widely exists in natural water bodies, with the characteristics of huge biomass generation, strong ecological function, and sensitive response to water quality. It removes the pollutants in water bodies mainly through the processes of absorption, metabolism, adsorption, and complexation, etc. Owing to its high tolerance against pollution and high removal efficiency for nitrogen and phosphorus, as well as the feasibility of recycling its cells at low cost, periphyton is a promising candidate for developing the treatment techniques of water purification. The newly-developed artificial periphyton systems, e.g., algal turf scrubbers, periphyton biofilm systems, periphyton aquaculture systems, have been successfully applied in treating livestock manure, aquaculture wastewater, and municipal sewage. However, further researches are needed to understand the growth patterns of periphyton, its physiological responses to pollutants concentration, and its molecular biological mechanisms in removing pollutants.