Simulation and control strategy for the variational influent of WWTP

With the development of activated sludge model, the simulation software for the design and operation of wastewater treatment plant （WWTP） was produced and has been widely used. The dynamic change of the quality and flow of influent are major factors causing the unstable operation of wastewater treatment process. As a basic model, ASMI model was used for the simulation of activated sludge process, and double exponential model was selected for the simulation of secondary sedimentation tank. The influences of influent change to the aeration tank and secondary sedimentation tank were investigated, and the relationship among influent change, the quality of effluent and the level of sludge blanket in secondary sedimentation tank was established. On the basis of the simulation results, the operation of the WWTP could be adjusted under the dynamic change of the influent. Furthermore, the controlling strategy combined the feed-forward on the influent flow and the feedback on the level of sludge blanket in the secondary sedimentation tank was studied.

Feedback Between Influent Condition Heterogeneity and Diversity of Bacterial Community in Bioreactor at Low Substrate Concentration

In order to investigate the effect of influent condition heterogeneity on diversity of the bacterial community,the degree of microbial resolution and effluent quality,biological treatment of micro-polluted source water is proposed. Scanning Electron Microscopy( SEM) analysis reflects that influent conditions change the morphologies of biofilm. Denaturing Gradient Gel Electrophoresis( DGGE) analysis shows differences of H values are due to succession of functional bacterial communities. Microbial resolution values and species identifications reveal organic carbon is the main cause of community differentiation and bacterial migration.

Daily Influent Quantity Forecasting Method for Sewage Treatment Plant Considering Uncertain Factors

Daily influent quantity forecasting plays an important role in sewage treatment plant design and operation.Its uncertain factors are classified into three categories including day types,weather conditions and special events,of which the latter two are consicered with a BP(Back Propagation)model.On this basis,the daily period feature is taken into account in the presented model.The data from a practical sewage treatment plant utility is employed to show the effectiveness of the method.

Online machine learning for stream wastewater influent flow rate prediction under unprecedented emergencies

Accurate influent flow rate prediction is important for operators and managers at wastewater treatment plants(WWTPs),as it is closely related to wastewater characteristics such as biochemical oxygen demand(BOD),total suspend solids(TSS),and pH.Previous studies have been conducted to predict influent flow rate,and it was proved that data-driven models are effective tools.However,most of these studies have focused on batch learning,which is inadequate for wastewater prediction in the era of COVID-19 as the influent pattern changed significantly.Online learning,which has distinct advantages of dealing with stream data,large data set,and changing data pattern,has a potential to address this issue.In this study,the performance of conventional batch learning models Random Forest(RF),K-Nearest Neighbors(KNN),and Multi-Layer Perceptron(MLP),and their respective online learning models Adaptive Random Forest(aRF),Adaptive K-Nearest Neighbors(aKNN),and Adaptive Multi-Layer Perceptron(aMLP),were compared for predicting influent flow rate at two Canadian WWTPs.Online learning models achieved the highest R2,the lowest MAPE,and the lowest RMSE compared to conventional batch learning models in all scenarios.The R2 values on testing data set for 24-h ahead prediction of the aRF,aKNN,and aMLP at Plant A were 0.90,0.73,and 0.87,respectively;these values at Plant B were 0.75,0.78,and 0.56,respectively.The proposed online learning models are effective in making reliable predictions under changing data patterns,and they are efficient in dealing with continuous and large influent data streams.They can be used to provide robust decision support for wastewater treatment and management in the changing era of COVID-19 and also under other unprecedented emergencies that could change influent patterns.

以丝瓜络为碳源的固相反硝化系统性能

构建以丝瓜络为碳源的固相反硝化系统,探究不同水力停留时间(HRT)和进水硝酸盐浓度(INC)下该系统的反硝化性能,为丝瓜络作为水产养殖尾水反硝化碳源的工艺优化提供理论依据。以丝瓜络(LS)为一维反硝化反应器(denitrification reactor,DR)外加碳源,在流场环境下,测定不同HRT(16、20、24和28 h)和INC(50、75、100和125 mg/L)下反硝化系统对硝酸盐氮(NO_(3)^(-)-N)、亚硝酸盐氮(NO_(2)^(-)-N)、氨氮(NH_(4)^(+)-N)、总氮(TN)、总磷(TP)和化学需氧量(CODcr)的去除效果。并采用高通量测序技术对丝瓜络反硝化反应器(LS-DR)在运行初期和末期时的细菌群落结构进行分析。当INC为50 mg/L,HRT为24h时,LS-DR对NO_(3)^(-)-N和TN均有较好的去除效果,去除率分别为98.97%±0.52%和97.84%±0.94%,此时出水NO_(2)^(-)-N浓度也达到较低水平(小于0.5 mg/L);在HRT为24 h的基础上,当INC增加至75、100和125 mg/L时,其NO_(3)^(-)-N去除率和NO_(3)^(-)-N去除速率(NRR)均随INC的增加而显著增加,出水COD则随INC的增加而降低,但均未实现完全反硝化,然而,LS-DR在整个实验期间均能完全去除NH_(4)^(+)-N;扫描电镜结果显示,丝瓜络表面结构有利于微生物附着生长;高通量测序结果显示,LS-DR的优势菌门包括变形菌门、拟杆菌门、弯曲杆菌门、厚壁菌门和疣微菌门;被鉴定的优势菌属中热单胞菌属(1.46%)、陶厄氏菌属(0.55%)、固氮螺菌属(3.32%)、Simplicispira(1.01%)、假黄色单胞菌属(0.39%)、草螺菌属(3.02%)和Uliginosibacterium(0.9%)主要参与反硝化的进行,Cytophaga xylanolytica(1.61%)和Cloacibacterium(2.69%)主要参与了丝瓜络的降解,黄杆菌属(1.17%)和Diaphorobacter(0.64%)既能进行反硝化,也能降解丝瓜络。LS-DR的最佳HRT为24 h,最适宜的INC为50 mg/L。本研究为丝瓜络固相反硝化工艺的优化提供了理论基础,为开发新型缓释碳源在养殖尾水处理中的应用提供参考。

Natural continuous influent nitrifier immigration effects on nitrification and the microbial community of activated sludge systems

Two sequencing batch reactors（SBRs） were operated for 100 days under aerobic conditions,with one being fed with unsterilized municipal wastewater（USBR）, and the other fed with sterilized municipal wastewater（SSBR）. Respirometric assays and fluorescence in situ hybridization（FISH） results show that active nitrifiers were present in the unsterilized influent municipal wastewater. The maximum ammonia utilization rate（AUR） and nitrite utilization rate（NUR） of the unsterilized influent were 0.32 ± 0.12 mg NH4＋-N/（L·hr） and0.71 ± 0.18 mg NO2--N/（L·hr）. Based on the maximum utilization rates, the estimated seeding intensity for the ammonia oxidizing bacteria（AOB） and nitrite oxidizing bacteria（NOB） of the USBR was 0.08 g AOB/（g AOB·day） and 0.20 g NOB/（g NOB·day） respectively. The fraction of nitrifiers/total bacteria in the influent was 5.35% ± 2.1%, the dominant AOB was Nitrosomonas spp., Nitrosococcus mobilis hybridizated with Nsm156, and the dominant NOB was Nitrospira hybridizated with Ntspa662. The influent nitrifiers potentially seeded the activated sludge of the bioreactor and hence demonstrated a mitigation of the acclimatization times and instability during start-up and early operation. The AUR and NUR in the USBR was 15% and 13% higher than the SSBR respectively during the stable stage, FISH results showed that nitrifiers population especially the Nitrospira in the USBR was higher than that in the SSBR. These results indicate that the natural continuous immigration of nitrifiers from municipal influent streams may have some repercussions on the modeling and design of bioreactors.

反硝化颗粒污泥系统和反硝化生物膜系统深度脱氮对比研究

对比分析了反硝化颗粒污泥系统和反硝化生物膜系统在不同进水条件和不同水力停留时间(HRT)下的脱氮效果。结果表明,当进水COD较高即外部碳源较为充足时,反硝化颗粒污泥系统和反硝化生物膜系统脱氮效果接近;而当进水总氮浓度较高即外部碳源受限时,生物膜系统的脱氮效果优于颗粒污泥系统。在不同的HRT条件下(3~6 h),反硝化生物膜系统的深度脱氮效果均优于反硝化颗粒污泥系统,且当HRT=5 h时,两系统的脱氮性能均达到最高。实验结果表明反硝化生物膜系统在脱氮性能方面略胜一筹。但是,结合经济性和去除性能进一步分析可知,与生物膜系统相比,颗粒污泥系统具有占地面积小、无载体成本等低成本的显著优势,在既有工艺出水深度脱氮的工程实践中,可优先选择反硝化颗粒污泥工艺,并可通过控制颗粒粒径和系统运行参数等措施强化脱氮性能。

Evaluation of the k-nearest neighbor method for forecasting the influent characteristics of wastewater treatment plant

The k-nearest neighbor （k-NN） method was evaluated to predict the influent flow rate and four water qualities, namely chemical oxygen demand （COD）, suspended solid （SS）, total nitrogen （T-N） and total phosphorus （T-P） at a wastewater treatment plant （WWTP）. The search range and approach for determining the number of nearest neighbors （NNs） under dry and wet weather conditions were initially optimized based on the root mean square error （RMSE）. The optimum search range for considering data size was one year. The square root-based （SR） approach was superior to the distance factor-based （DF） approach in determining the appropriate number of NNs. However, the results for both approaches varied slightly depending on the water quality and the weather conditions. The influent flow rate was accurately predicted within one standard deviation of measured values. Influent water qualities were well predicted with the mean absolute percentage error （MAPE） under both wet and dry weather conditions. For the seven-day prediction, the difference in predictive accuracy was less than 5% in dry weather conditions and slightly worse in wet weather conditions. Overall, the k-NN method was verified to be useful for predicting WWTP influent characteristics.

A^(2)/O+反硝化深床滤池在城镇污水处理厂深度经济脱氮的运行优化

脱氮是当前城镇污水处理的重点,其中A^(2)/O+反硝化滤池工艺是生活污水处理主流工艺,四川省岷江流域某城镇污水处理厂通过优化进水流量分配比、调节溶解氧和内回流比、碳源筛选等工艺试验,综合考察了工艺调控措施对系统脱氮效能的提升以及脱氮成本的经济化控制。结果表明,A^(2)/O池进水100%进入厌氧区、内回流比200%、A^(2)/O池末端溶解氧控制在1.5 mg/L、反硝化深床滤池投加液体复合碳源,在有效深度脱氮的同时节约运行费用,总氮指标满足岷沱江标准,脱氮费用降低0.37元/m^(3)。

Characteristic and correlation analysis of influent and energy consumption of wastewater treatment plants in Taihu Basin

The water quality and energy consumption of wastewater treatment plants(WWTPs)in Taihu Basin were evaluated on the basis of the operation data from 204 municipal WWTPs in the basin by using various statistical methods.The influent ammonia nitrogen(NH3-N)and total nitrogen(TN)of WWTPs in Taihu Basin showed normal distribution,whereas chemical oxygen demand(COD),biochemical oxygen demand(BOD5),suspended solid(SS),and total phosphorus(TP)showed positively skewed distribution.The influent BOD5/COD was 0.4%-0.6%,only 39.2%SS/BOD5 exceeded the standard by 36.3%,the average BOD5/TN was 3.82,and the probability of influent BOD5/TP>20 was 82.8%.The average energy consumption of WWTPs in Taihu Basin in 2017 was 0.458 kWh/m^3.The specific energy consumption of WWTPs with a daily treatment capacity of more than 5×10^4 m^3 in Taihu Basin was stable at 0.33 kWh/m^3.A power function relationship was observed between the reduction in COD and NH3-N and the specific energy consumption of pollutant reduction,and the higher the pollutant reduction is,the lower the specific energy consumption of pollutant reduction presents.In addition,a linear relationship existed between the energy consumption of WWTPs and the specific energy consumption of influent volume and pollutant reduction.Therefore,upgrading and operation with less energy consumption of WWTPs is imperative and the suggestions for Taihu WWTPs based on stringent discharge standard are proposed in detail.

Short-term prediction of influent flow rate and ammonia concentration in municipal wastewater treatment plants

The prediction of the influent load is of great importance for the improvement of the control system to a large wastewater treatment plant. A systematic data analysis method is presented in this paper in order to estimate and predict the periodicity of the influent flow rate and ammonia （NH3） concentrations： 1） data filtering using wavelet decomposition and reconstruction; 2） typical cycle identification using power spectrum density analysis; 3） fitting and prediction model establishment based on an autoregressive model. To give meaningful information for feedforward control systems, predictions in different time scales are tested to compare the corresponding predicting accuracy. Considering the influence of the rainfalls, a linear fitting model is derived to estimate the relationship between flow rate trend and rain events. Measurements used to support coefficient fitting and model testing are acquired from two municipal wastewater treatment plants in China. The results show that 1） for both of the two plants, the periodicity affects the flow rate and NH3 concentrations in different cycles （especially cycles longer than 1 day）; 2） when the flow rate and NH3 concentrations present an obvious periodicity, the decreasing of prediction accuracy is not distinct with increasing of the prediction time scales; 3） the periodicity influence is larger than rainfalls; 4） the rainfalls will make the periodicity of flow rate less obvious in intensive rainy periods.

Influence of influent on anaerobic ammonium oxidation in an Expanded Granular Sludge Bed-Biological Aerated Filter integrated system

Shortcut nitrification-denitrification,anaerobic ammonium oxidation(ANAMMOX),and methanogenesis have been successfully coupled in an Expanded Granular Sludge Bed-Biological Aerated Filter(EGSB-BAF)integrated system.As fed different synthetic wastewater with chemical oxygen demand(COD)of 300-1200 mg·L^(-1)and NH_(4)^(+)-N of 30-120 mg·L^(-1)at the outer recycle ratio of 200%,the influence of influent on ANAMMOX in the integrated system was investigated in this paper.The experimental results showed that higher COD concentration caused an increase in denitrification and methanogenesis but a decrease in ANAMMOX;however,when an influent with the low concentration of COD was used,the opposite changes could be observed.Higher influent NH_(4)^(+)-N concentration favored ANAMMOX when the COD concentration of influent was fixed.Therefore,low COD=NH_(4)^(+)-N ratio would decrease competition for nitrite between ANAMMOX and denitrification,which was favorable for reducing the negative effect of organic COD on ANAMMOX.The good performance of the integrated system indicated that the bacterial community of denitrification,ANAMMOX,and methanogenesis could be dynamically maintained in the sludge of EGSB reactor for a certain range of influent.

优化污泥回流方式对多级AO-MBR工艺的影响

采用处理水量为0.15 m^(3)/h的中试装置,开展多级AO-MBR工艺处理低C/N城市污水试验研究,通过优化污泥回流方式、溶解氧及污泥浓度控制等措施,降低高溶解氧污泥回流对前端生化池的影响,实现出水水质达到地表水准Ⅳ类标准(TN除外)。结果表明,在耦合MBR工艺的形式下,经过生化池多级回流能显著保证各反应区的溶解氧环境,保持各反应区的污泥浓度平衡,进一步提高出水水质。在水温低于12℃、进水TN质量浓度为23~33 mg/L时,采用回流方式4能稳定保证TN去除率达到60%以上,实现出水TN质量浓度达到10 mg/L左右;进水TP质量浓度为2~4 mg/L时,TP去除率达到85%以上,实现出水TP质量浓度低于0.3 mg/L的要求。

提质增效下河网地区典型城镇污水厂污泥产率变化趋势研究

近年来,我国大力推进城镇污水系统提质增效,污水厂进水浓度、进水量大幅度提升,污泥产量也随之提升。通过对广州市河网地区N污水厂调研研究,分析污泥产率在提质增效前后的变化规律,深入研究进水COD、BOD、SS浓度和进水量等因素在提质增效前后对污泥产率的具体影响,结果表明:污水厂污泥产率在提质增效前后具有明显差异,提质增效后污泥产率大幅度上升,后逐步降低并趋于稳定;提质增效强化了污泥产率与进水COD、SS浓度的正相关性关系,强化了污泥产率与进水量的负相关关系;污泥产率与进水BOD浓度在提质增效前呈弱的负相关关系,提质增效后呈弱的正相关关系。

清水池水力效率影响因素研究

清水池具有水力调节和消毒接触的双重作用,提高t_(10)/T是提高消毒效率而减少消毒剂投加量和副产物生成量的有效方法。针对清水池实例,进行整体建模,以数值模拟方法,研究主要尺寸对清水池t_(10)/T的影响程度,并验证设计方案的合理性。结果表明:长宽比是t_(10)/T影响最为明显的因素,但变大的趋势放缓。减少弯道数量及宽度和增大进水管管径,均可使t_(10)/T有所增加。清水池实例的长宽比为38,水力效率为0.54,可以满足不少于0.5的设计要求。

长江中下游典型污水系统提质增效案例研究

以长江中下游某城市南部污水系统为例,对污水系统外水入侵、高水位运行、进厂水质浓度低等问题进行分析,针对性的提出分片、分区、分阶段提质增效的思路,并给出降水位排查污水管网、市政管网系统整治、排水单元整治、污水管网优化运行等技术措施.先期实施的1#泵站片区通过上述措施,已挤出外水量约为12 708 m3/d,污水厂进水BOD5浓度由69.6 mg/L提升至78.3 mg/L,较整治前提升12.5%,城市污水集中收集率由61.6%提升至69.3%,基本实现了提质增效的阶段目标.

Distribution,characteristics and daily fluctuations of microplastics throughout wastewater treatment plants with mixed domestic-industrial influents in Wuxi City,China

In wastewater treatment plants(WWTPs),microplastics(MPs)are complex,especially with mixed domestic–industrial influents.Conventional random grab sampling can roughly depict the distribution and characteristics of MPs but can not accurately reflect their daily fluctuations.In this study,the concentration,shape,polymer type,size,and color of MPs were analyzed by micro-Raman spectroscopy(detection limit of 0.05 mm)throughout treatment stages of three mixed domestic–industrial WWTPs(W1,W2,and W3)in Wuxi City,China,and the daily fluctuations of MPs were also obtained by dense grab sampling within 24 h.For influent samples,the average MP concentration of 392.2 items/L in W1 with 10%industrial wastewater was much higher than those in W2(71.2 items/L with 10%industrial wastewater)and W3(38.3 items/L with 60%industrial wastewater).White polyethylene granules with a diameter less than 0.5 mm from plastic manufacturing were the most dominant MPs in the influent of W1,proving the key role of industrial sources in MPs pollution.In addition,the daily dense sampling results showed that MP concentration in W1 influent fluctuated widely between 29.1 items/L and 4617.6 items/L within a day.Finally,few MPs(less than 4.0 items/L)in these WWTPs effluents were attributed to the effective removal of wastewater treatment processes.Thus,further attention should be paid to regulating the primary sources of MPs.

Short-term prediction of the influent quantity time series of wastewater treatment plant based on a chaos neural network model

By predicting influent quantity,a wastewater treatment plant(WWTP)can be well controlled.The non-linear dynamic characteristic of WWTP influent quantity time series was analyzed,with the assumption that the series was predictable.Based on this,a short-term forecasting chaos neural network model of WWTP influent quantity was built by phase space reconstruction.Reasonable forecasting results were achieved using this method.

污水厂低浓度进水问题分析

随着《城镇污水处理提质增效三年行动方案(2019~2021)年》的印发,全国各地积极开展提质增效工作。工程实施后,部分城市污水处理厂进水浓度偏低的问题改善有限,成为提质增效的痛点。基于完成市政排水管网改造工程的情况,对某污水处理厂进水CODCr浓度仍不足100 mg/L的污水分区进行成效评估排查,通过水质水量平衡计算,分析出该新建区存在规划与现状不匹配、非生活用水占比高、雨污混接情况复杂等问题,得出通过工程手段难以彻底解决污水厂低浓度进水问题的结论。为该区域后续提质增效工作提出优化排水结构、强调建管结合、加强排水管理及合理制定提质增效目标的建议。