Enhanced Biological Nutrients Removal in Modified Step-feed Anaerobic/Anoxic/Oxic Process

In order to enhance phosphorus removal in traditional step-feed anoxic/oxic nitrogen removal process,a modified pilot-scale step-feed anaerobic/anoxic/oxic(SFA 2/O) system was developed,which combined a reactor similar to UCT-type configuration and two-stage anoxic/oxic process.The simultaneous nitrogen and phosphorus removal capacities and the potential of denitrifying phosphorus removal,in particular,were investigated with four different feeding patterns using real municipal wastewater.The results showed that the feeding ratios(Q1)in the first stage determined the nutrient removal performance in the SFA 2/O system.The average phosphorus removal efficiency increased from 19.17% to 96.25% as Q1 was gradually increased from run 1 to run 4,but the nitrogen removal efficiency exhibited a different tendency,which attained a maximum 73.61%in run 3 and then decreased to 59.62%in run 4.As a compromise between nitrogen and phosphorus removal,run 3 (Q1=0.45Qtotal) was identified as the optimal and stable case with the maximum anoxic phosphorus uptake rate of 1.58 mg·(g MLSS)-1 ·h-1.The results of batch tests showed that ratio of the anoxic phosphate uptake capacity to the aerobic phosphate uptake capacity increased from 11.96% to 36.85% with the optimal influent feeding ratio to the system in run 3,which demonstrated that the denitrifying polyP accumulating organisms could be accumulated and contributed more to the total phosphorus removal by optimizing the inflow ratio distribution.However,the nitrate recirculation to anoxic zone and influent feeding ratios should be carefully controlled for carbon source saving.

Transformation of phthalic acid diesters in an anaerobic/anoxic/oxic leachate treatment process

Transformations of di-n-butyl phthalate(DBP) and di(2-ethylhexyl) phthalate(DEHP) have been investigated in anaerobic/anoxic/oxic(A/A/O) leachate treatment processes. Although the DBP removal processes are different when the DBP initial concentration is different, the overall system DBP removal efficiencies are high(N 94%).DEHP is much more difficult to remove than DBP. The removal efficiency of DEHP is approximately 75%–78%.The results of mass balance calculations indicate that approximately 33.7%–50.7% of the DBP is degraded by the activated sludge, 48.9%–64.9% accumulates in the system, and 0.4%–1.4% is contained in the final effluent. Approximately 15.0%–19.0% of the DEHP is degraded by activated microcosms, 75.8%–79.0% accumulates in the system, and 5.2%–6.0% is contained in the final effluent. Biodegradation and adsorption to the activated sludge are the main mechanisms for DBP removal and adsorption to the activated sludge is the main mechanism for DEHP removal. The different removal mechanisms of the two PAEs may be related to their different molecular structures. However, PAEs are not really removed when they adsorb onto the sludge. Therefore, methods for decreasing PAEs adsorption and increasing the biodegradation efficiencies of the leachate treatment processes should be further investigated.

The first metagenome of activated sludge from full-scale anaerobic/anoxic/oxic(A2O) nitrogen and phosphorus removal reactor using Illumina sequencing

The anaerobic/anoxic/oxic（A2O） process is globally one of the widely used biological sewage treatment processes. This is the first report of a metagenomic analysis using Illumina sequencing of full-scale A2O sludge from a municipal sewage treatment plant.With more than 530,000 clean reads from different taxa and metabolic categories, the metagenome results allow us to gain insight into the functioning of the biological community of the A2O sludge. There are 51 phyla and nearly 900 genera identified from the A2O activated sludge ecosystem. Proteobacteria, Bacteroidetes, Nitrospirae and Chloroflexi are predominant phyla in the activated sludge, suggesting that these organisms play key roles in the biodegradation processes in the A2O sewage treatment system.Nitrospira, Thauera, Dechloromonas and Ignavibacterium, which have abilities to metabolize nitrogen and aromatic compounds, are most prevalent genera. The percent of nitrogen and phosphorus metabolism in the A2O sludge is 2.72% and 1.48%, respectively. In the current A2O sludge, the proportion of Candidatus Accumulibacter is 1.37%, which is several times more than that reported in a recent study of A2O sludge. Among the four processes of nitrogen metabolism, denitrification related genes had the highest number of sequences（76.74%）, followed by ammonification（15.77%）, nitrogen fixation（3.88%） and nitrification（3.61%）. In phylum Planctomycetes, four genera（Planctomyces, Pirellula, Gemmata and Singulisphaera） are included in the top 30 abundant genera, suggesting the key role of ANAMMOX in nitrogen metabolism in the A2O sludge.

Study on Piggery Anaerobic Fermentation Slurry Treated by Anoxic/Oxic Process

[Objective] The aim of this study was to provide a fast, stable and efficient piggery wastewater processing technology. [Method] The start-up process was studied through the experiment of piggery anaerobic fermentation slurry treated by Anoxic/Oxic （A/O） reactor. The process was divided into two stages： at the first stage, dominant micro flora were cultivated in Anoxic and Oxic reaction tanks respectively; at the second stage. Anoxic and Oxic reaction tanks were initiated jointly to gradually enhance water load and continued to cultivate and domesticate microorganisms, and finally the start-up process was completed. [ Result] The results showed that return mixture ratio and return sludge ratio was 2 and 1 respectively when the temperature reached 32 ±2 ℃. However. when aeration rate of Oxic reaction amounted to 0.5 m^3/h, the re- moval rate of COD and NH4^＋ -H were 89.87% and 89.31% respectively through practical operation within 50 days, which indicated that the start- up process through A/O reactor was successful. Conclusion This study can provide a scientific basis and reference for innocuous technique of piggery anaerobic fermentation slurry treatment.

Effect of short-term atrazine addition on the performance of an anaerobic/anoxic/oxic process

In this study,an anaerobic/anoxic/oxic(A^(2)O)wastewater treatment process was implemented to treat domestic wastewater with short-term atrazine addition.The results provided an evaluation on the effects of an accidental pollution on the operation of a wastewater treatment plant(WWTP)in relation to Chemical Oxygen Demand(COD)and biological nutrient removal.Domestic wastewater with atrazine addition in 3 continuous days was treated when steady biological nutrient removal was achieved in the A^(2)O process.The concentrations of atrazine were 15,10,and 5 mg%L–1 on days 1,2 and 3,respectively.The results showed that atrazine addition did not affect the removal of COD.The specific NH4þoxidation rate and NO3–reduction rate decreased slightly due to the short-term atrazine addition.However,it did not affect the nitrogen removal due to the high nitrification and denitrification capacity of the system.Total nitrogen(TN)removal was steady,and more than 70%was removed during the period studied.The phosphorus removal rate was not affected by the short-term addition of atrazine under the applied experimental conditions.However,more poly-hydroxy-alkanoate(PHA)was generated and utilized during atrazine addition.The results of the oxygen uptake rate(OUR)showed that the respiration of nitrifiers decreased significantly,while the activity of carbon utilizers had no obvious change with the atrazine addition.Atrazine was not removed with the A^(2)O process,even via absorption by the activated sludge in the process of the short-term addition of atrazine.

Denitrifying phosphorous removal in anaerobic/anoxic SBR system with different startup operation mode

To achieve stable and efficient nitrogen and phosphorus removal and to investigate the characteristics of the A/A SBR enriched with denitrifying phosphorus removal bacteria(DPB),the whole course of startup was studied with two reactors operated in different mode.The reactor I was operated under anaerobic/settling/anoxic/settling mode,and the reactor II was operated under anaerobic/anoxic/settling mode.Differences between the two reactors in removal efficiency of COD,nitrogen and phosphorus were examined.The results indicated that efficient performance could be achieved in both reactors with different startup operation mode,while the phosphorus removal efficiency was improved sooner in reactor I than in reactor II,which suggested that reactor I would supply a more favorable condition for DPB proliferation.Meanwhile,it was observed that the amount of organic substrates consumption had a linear correlation to that of phosphorus release in anaerobic phase when DPB was accumulated in the A/A SBR denitrifying phosphorus removal system.

Electricity Generation Performance of Microbial Fuel Cell Embedded in Anaerobic-Anoxic-Oxic Wastewater Treatment Process

Microbial fuel cell (MFC) embedded in anaerobic-anoxic-oxic (A2/O) process has positive effects on wastewater treatment, which can enhance the efficiencies of pollutants’ removal, along with electricity production. But the electricity generation performance and its optimization of MFC embedded in A2O process still needs to be further investigated. In this study, in order to optimize the contaminants removal and electricity production of the MFC-A2/O reactor, a lab-scale corridor-style MFC-A2/O reactor, which could simulate the practical A2/O biological reactor better, was designed and operated. The removal efficiencies of chemical oxygen demand, total nitrogen and total phosphorus were continuously monitored so as the electricity generation. In addition, the influences of the structural parameters’ changes of MFC on the output voltage, including electrode material, the directly connected area and the distance between electrodes, were also studied. The results elucidated that the effluent quality of A2/O reactor could be improved when MFC was embedded, and all the investigated structural factors were closely related to the electricity generation performance of MFC to some extent.

Characteristics of anoxic phosphors removal in sequence batch reactor

The characteristics of anaerobic phosphorus release and anoxic phosphorus uptake were investigated in sequencing batch reactors using denitrifying phosphorus removing bacteria （DPB） sludge. The lab-scale experiments were accomplished under conditions of various nitrite concentrations （5.5, 9.5, and 15 mg/L） and mixed liquor suspended solids （MLSS） （1844, 3231, and 6730 mg/L）. The results obtained confirmed that nitrite, MLSS, and pH were key factors, which had a significant impact on anaerobic phosphorus release and anoxic phosphorus uptake in the biological phosphorous removal process. The nitrites were able to successfully act as electron acceptors for phosphorous uptake at a limited concentration between 5.5 and 9.5 mg/L. The denitrification and dephosphorous were inhibited when the nitrite concentration reached 15 mg/L. This observation indicated that the nitrite would not inhibit phosphorus uptake before it exceeded a threshold concentration. It was assumed that an increase of MLSS concentration from 1844 mg/L to 6730 mg/L led to the increase of denitrification and anoxic P-uptake rate. On the contrary, the average P-uptake/N denitrifying reduced from 2.10 to 1.57 mg PO4^3--P/mg NO3^--N. Therefore, it could be concluded that increasing MLSS of the DEPHANOX system might shorten the reaction time of phosphorus release and anoxic phosphorus uptake. However, excessive MLSS might reduce the specific denitrifying rate. Meanwhile, a rapid pH increase occurred at the beginning of the anoxic conditions as a result of denitrification and anoxic phosphate uptake. Anaerobic P release rate increased with an increase in pH. Moreover, when pH exceeded a relatively high value of 8.0, the dissolved P concentration decreased in the liquid phase, because of chemical precipitation. This observation suggested that pH should be strictly controlled below 8.0 to avoid chemical precipitation if the biological denitrifying phosphorus removal capability is to be studied accurately.

Effects of loading rate and hydraulic residence time on anoxic sulfide biooxidation

The optimal operation conditions in an anoxic sulfide oxidizing (ASO) bioreactor were investigated. The maximal removal rates for sulfide and nitrate were found to be 4.18 kg/(m3·d) and 1.73 kg/(m3·d), respectively. The volumetrical volumetric loading rates (LRs) observed through decreasing hydraulic retention time (HRT) at fixed substrate concentration are higher than those by increasing substrate concentration at fixed HRT. The sulfide oxidation in ASO reactor was partially producing both sulfate and sulfur; but the amount of sulfate produced was approximately one third that of sulfur. The process was able to tolerate high sulfide concentration, as the sulfide removal percentage always remained near 99% when influent concentration was up to 580 mg/L. It tolerated relatively lower nitrate concentration because the removal percentage dropped to 85% when influent con- centration was increased above 110 mg/L. The process can tolerate shorter HRT but careful operation is needed. Nitrate conversion was more sensitive to HRT than sulfide conversion since the process performance deteriorated abruptly when HRT was decreased from 3.12 h to 2.88 h. In order to avoid nitrite accumulation in the reactor, the influent sulfide and nitrate concentrations should be kept at 280 mg/L and 67.5 mg/L respectively. Present biotechnology is useful for removing sulfides from sewers and crude oil.

Nitrogen Removal Performance of Continuous Anoxic/Oxic System Using Activated Sludge and Sludge Biofilms

Nitrogen is the most important component for living beings while the excessive discharge of organic and inorganic nitrogen may create severe environmental problems.In this study,a continuous anoxic/oxic(A/O)reactor adopting activated sludge and sludge biofilms in the anoxic and oxic zones was applied for total nitrogen(TN)and chemical oxygen demand(COD)removal,and the efficiencies of nitrification and denitrification were compared as well.Results showed that when using activated sludge,the effluent concentrations of NH_(4)^(+)-N,NO_(3)^(-)-N,NO_(2)^(-)-N,TN and COD were inconsistent and fluctuated greatly,and the removal efficiencies of corresponding nitrification,denitrification and TN were also unstable;the obtained average COD removal efficiency was 85%.While using sludge biofilms,the acquired effluent concentrations of NH^(+)_(4)-N,NO^(-)_(3)-N,NO_(2)^(-)-N,TN and COD became stable and constant.The nitrification,denitrification,TN and COD removal efficiencies were 96%,84%and 65%and 94%,respectively.Bacterial community analysis of sludge biofilms indicated that the genus Arcobacter was the major denitrifiers in the anoxic zone with relative abundance of 76.1%,and in the oxic zone the abundances of Acinetobacter,Hydrogenophaga and Nitrospira responsible for complete nitrification were 20.05%,7.6%and 3.7%respectively.The high abundance of nitrifying bacteria and denitrifiers were related with the high and stable nitrogen and COD removal.

Kinetics model of aerobic phase in hybrid anoxic-oxic process

Kinetics models of COD degradation,biomass growth of the anoxic-oxic ( A/O) system as well as NH3-N degradation in aerobic phase were presented according to the mass balance theory,reaction-diffusion theory and Fick law. Then these models were testified by comparson with experimental results. It is demonstrated that the variation trends of theoretical and experimental values for COD degradation and biomass growth are similar. The deviation rate between theoretical and experimental values is always under 20% even it increases along with the fluctuation of influent organic loading. In terms of NH3-N degradation,nitrification can also be well simulated by the model as the substrates of influent are sufficient. It indicates that the model can accurately reflect the reaction in hybrid A/O process. Models presented herein provide a theoretical basis for the design, operation and control of hybrid A/O process.

臭氧氧化+A/O+臭氧氧化工艺在化工园区污水处理厂中的运用

化工园区废水成分复杂,难降解物质多。某化工园区污水处理厂选用分质强化混凝沉淀+臭氧氧化作为预处理工艺,同时采用水解酸化+厌氧好氧(Anaerobic/Oxic,A/O)的二级处理工艺和混凝沉淀+臭氧氧化的深度处理工艺。实际运行结果表明,该组合工艺对化学需氧量(Chemical Oxygen Demand,COD)的平均去除率为85.7%,COD去除效果良好,出水水质优于《城镇污水处理厂污染物排放标准》(GB 18918—2002)的一级A标准。

Carbonaceous and nitrogenous disinfection byproduct precursor variation during the reversed anaerobic–anoxic–oxic process of a sewage treatment plant

Disinfection byproduct（DBP）precursors in wastewater during the reversed anaerobic–anoxic–oxic（A^2/O）process,as well as their molecular weight（MW）and polarity-based fractions,were characterized with UV scanning,fluorescence excitation emission matrix,Fourier transform infrared and nuclear magnetic resonance spectroscopy.Their DBP formation potentials（DBPFPs）after chlorination were further tested.Results indicated that the reversed A^2/O process could not only effectively remove the dissolved organic carbon（DOC）and dissolved total nitrogen in the wastewater,but also affect the MW distribution and hydrophilic–hydrophobic properties of dissolved organic matter（DOM）.The accumulation of low MW and hydrophobic（HPO）DOM was possibly due to the formation of soluble microbial product-like（SMP-like）matters in the reversed A^2/O treatment,especially in the anoxic and aerobic processes.Moreover,DOM in the wastewater displayed a high carbonaceous disinfection byproduct formation potential（C-DBPFP）in the fractions of MW100 k Da and MW5 k Da,and revealed an increasing tendency of nitrogenous disinfection byproduct formation potential（N-DBPFP）with decrease of MW.For polarity-based fractions,the HPO fraction of wastewater showed significantly higher C-DBPFP and N-DBPFP than hydrophilic and transphilic fractions.Therefore,although the reversed A^2/O process could remove most DBP precursors by DOC reduction,it led to the enhancement of DBPFP with the formation and accumulation of low MW and HPO DOM.In addition,strong correlations between C-DBPFPs and SUVA,and between N-DBPFPs and DON/DOC,were observed in the wastewater,which might be helpful for DBPFP prediction in wastewater and reclaimed water chlorination.

缺氧生物膜转型厌氧氨氧化生物膜培养与富集特性

接种西安市某污水处理厂缺氧池生物膜构建升流式厌氧固定床生物膜(UAFB)反应器从而富集培养厌氧氨氧化(Anammox)生物膜,通过测定生物膜Anammox活性和酶活性并进行高通量测序分析,探讨城市污水处理厂现有填料转型培养Anammox生物膜的可行性及生物膜内菌群演替规律.结果表明,经29d培养后的UAFB-Anammox反应器TN去除率高达76.22%,快速启动成功;负荷提升阶段,表面氮负荷(SNLR)由0.23g/(m^(2)·d)提升至2.59g/(m^(2)·d),最大Anammox活性维持2.15g/(m^(2)·d),TN去除率高达83.68%.Illumina MiSeq测序结果发现,富集后的生物膜中优势菌属为Ca.Brocadia,相对丰度为33.38%,富集效果明显.同时缺氧生物膜上反硝化菌Denitratisoma以Anammox的产物NO_(3)^(-)-N为基质,逐渐与AnAOB形成共生存关系.这说明利用城市污水处理厂现有缺氧生物膜可以快速培养Anammox生物膜,对Anammox工艺在城市污水处理厂升级改造中的应用提供一定参考.

水解酸化+A2/O+AO+芬顿氧化工艺处理工业园区污水

针对工业园区的污水排放企业种类较多、进水水量水质波动较大、污染物复杂且可生化性差、排放标准高的特征,以浙江省德清县某工业园区实际污水处理工程为对象,分析了水解酸化+A2/O+AO+芬顿氧化工艺处理以印染、食品制造、金属加工企业为主的废水排放的技术经济可行性.实践结果显示,出水水质的COD、NH_(3)-N、TN及TP能稳定达到《城镇污水处理厂主要染物排放标准》(DB33/2169—2018)中的限值,其余指标达到《城镇污水处理厂染物排放标准》(GB18918—2002)的一级A标准;工程投资金额为8200元/m^(3),实际直接运行成本为2.39元/m^(3).

提标升级对乡镇污水处理厂碳排放特征的影响

在碳达峰、碳中和和流域水污染防治的背景下,乡镇污水处理厂减污降碳协同势在必行。基于成都市某乡镇市政污水处理厂2016—2022年水质水量数据,分析提标升级前后化学需氧量、氨氮、总磷、总氮的时间变异性,利用《IPCC 2006国家温室气体清单指南》(2019年修订版)、《城镇水务系统碳核算与减排路径技术指南》评估直接、间接碳排放强度特征,探究提标升级前后碳排放量对季节、水质及污染物削减量的响应。结果表明:1)污水处理厂主体工艺从周期循环活性污泥法(CASS)升级为厌氧-缺氧-好氧-膜生物反应器法(AAO-MBR)后,出水水质满足DB 51/2311—2016《四川省岷江、沱江流域水污染物排放标准》,升级后通过增加碳源、利用MBR膜截留污泥等措施,使出水水质指标更加稳定,对污染物的处理效率更高;2)提标升级后,直接、间接碳排放强度分别为0.296和1.082 kg/m^(3)(以CO_(2)当量计),分别增加41.59%和105.70%,且夏季碳排放强度显著低于其他季节(P<0.01),升级前后的间接碳排放强度均高于直接碳排放强度;3)提标升级后,总碳排放强度增加了0.643 kg/m^(3)(以CO_(2)当量计),工艺升级导致的电耗增加,使得间接碳排放强度变化更显著。乡镇污水处理厂提标升级在提高处理效能的同时也增加了碳排放量,建议在工艺改造中协同考虑污染物去除与能耗控制,以实现减污降碳协同增效。

中低温下基于纯膜条件多段A/O-MBBR系统脱氮能力中试研究

针对低温条件下活性污泥法生物硝化限制性瓶颈问题,构建了三段式A/O-MBBR中试系统,对其在中低温条件下的脱氮能力开展研究,结合生物膜在静态实验条件下的硝化能力及形态变化,分析了系统脱氮效果的影响因素。研究结果表明,在反应温度为10~16℃、处理水量为(23.6±5.4) m^(3)/d、碳源投加量为50~90 mg/L条件下,系统进水SCOD、NH+4-N和TIN浓度分别为(147±30)、(38.3±2.1)和(39.6±2.3) mg/L,出水分别降至(26±6)、(0.4±0.6)和(6.8±3.6) mg/L,去除率分别达到82.3%、99.0%和82.8%,其中系统中第2段A/O-MBBR分系统表现出良好的硝化能力,其硝化去除负荷可达0.9 g/(m^(2)·d),NH_(4)^(+)-N硝化贡献率可达54%;生物膜厚度是影响其硝化能力的重要因素。

有机负荷率对新型厌氧/好氧/缺氧工艺的影响机制探究

为了探究进水有机负荷对新型厌氧/好氧/缺氧工艺(AOA)工艺的影响,构建了新型AOA生物脱氮除磷反应器,通过控制进水COD考察了有机负荷率(OLR)对AOA工艺对污染物和营养盐去除的影响,并通过分析不同OLR工况影响下污泥特征及胞内聚合物的变化规律、微生物群落特征揭示了OLR对AOA工艺的影响机制。结果表明进水OLR由200 mg/L提高至400 mg/L,AOA工艺具有良好的去除效率,COD、TN和SOP的去除效率分别达到93.6%~96.2%、82.45%~85.1%和94.2%~98.5%。进水OLR提高了污泥往胞外聚合物含量,且显著提高了PN含量。在进水OLR为400 mg/L时,聚羟基脂肪酸酯(PHA)最大积累量为5.98 mmol/g,糖原质含量下降至6.03 mmol/g。OLR能影响AOA工艺内微生物群落结构,适量提高OLR促进了Proteobacteria和Firmicutes在污泥内的占比。研究结果为AOA工艺处理不同进水OLR的废水提供一定的数据支撑和理论依据。

中和过滤-缺氧反硝化-好氧硝化工艺处理电极箔生产废水

以江苏某电极箔生产企业废水处理工程为研究对象,采用“中和过滤-缺氧反硝化-好氧硝化”为主体工艺进行处理,通过工艺参数的优化调节,工程运行结果表明该工艺可有效处理电极箔生产废水,氨氮、总氮去除率可达90%、87.5%以上,对应出水低于5、25 mg/L,优于国家《电子工业水污染物排放标准》(GB 39731-2020)间接排放标准以及下游污水处理厂接管标准,直接运行成本约为3.58元/m3。

Effects of Coagulation and Ozonation Pretreatments on Biochemical Treatment of Fluid Catalytic Cracking Wastewater

Fluid catalytic cracking (FCC) salty wastewaters, containing quaternary ammonium compounds (QACs), are very difficult to treat by biochemical process. Anoxic/oxic (A/O) biochemical system, based on nitrification and denitrification reactions, was used to assess their possible biodegradation. Because of the negative effects of high salt concentration (3%), heavy metals and toxic organic matter on microorganisms’ activities, some techniques consisting of dilution, coagulation and flocculation, and ozonation pretreatments, were gradually tested to evaluate chemical oxygen demand (COD), ammonia-nitrogen (ammonia-N) and total nitrogen (TN) removal rates. In this process of FCC wastewater, starting with university-domesticated sludge, the ammonia-N and TN removal rates were worst. However, when using domesticated SBR’s sludge and operating with five-fold daily diluted influent (thus reducing salt concentration), the ammonia-N removal reached about 57% while the TN removal rate was less than 37% meaning an amelioration of the nitrification process. However, by reducing the dilution factors, these results were inflected after some days of operation, with ammonia-N removal decreasing and TN barely removed meaning a poor nitrification. Even by reducing heavy metals concentration with coagulation/flocculation process, the results never changed. Thereafter, by using ozonation pre-treatment to degrade the detected organic matter of di-tert-butylphenol and certain isoparaffins, COD, ammonia-N and TN removal rates reached 92%, 62% and 61%, respectively. These results showed that the activities of the microorganisms were increased, thus indicating a net denitrification and nitrification reactions improvement.