Treatment of Wastewater Containing Heavy Metals Using Dissolved Air Released Flotation Column

A new type of dissolved air released flotation column is developed to treat wastewater containing Cr(VI)based on advantages of both dissolved air floatation and column floatation. By using a column with a diameter of 50mm and a specially made dissolved air releaser, micro-bubbles inside the column can be formed. N2H4·H2O was usedas reductant, AlCl3 as flocculant, C12H25SO3Na(SDS) as surfactant in the experiment. The effects of pH of wastewa-ter, pressure of dissolved air, ratio of return water, and concentration of flocculant and surfactant on the removal effi-ciency are studied. The results show that the efficiency of dissolved air released flotation column is much higher thanthat of other approaches after the operation parameters are optimized, with the reduction ratio of Cr(VI) in wastewaterreaching 98%. So this technique can be widely used in wastewater treatment.

Experimental Study of Effluent Salty Wastewater Treatment from a Solar Desalination Pond

In this research, the quality of the wastewater discharged into the environment has been investigated. The effluent from solar desalination pond contains large amounts of TDS (3.68 grams per liter) and TH (6.50 grams per liter). Since the use of filter is not economical in this case, three types of commercial coagulants such as aluminum sulfate, ferric chloride and ferric sulfide have been used in this study. The main parameters such as effectiveness of three inorganic coagulants, ammonium sulfate, ferric sulfate, and ferric chloride, which separately help to remove hardness, have been studied. According to the results, using laboratory test, 25/g of ferric sulfate as coagulant is best coagulant mass and the ratio of 4 to 3 for auxiliary coagulant (sodium carbonate and sodium hydroxide) to coagulant will be best ratio. Also, the mixing rate of 120 rpm in the first reactor will give the best mixing speed. These conditions will lead to 0.348 grams per liter of TDS, 0.345 grams per liter of TH and 0.195 grams per liter of calcium hardness and 300 micro Siemens electrical conductivity of the purified sample.

Oxygen Transfer and Hydrodynamics in a Flexible Fibre Biofilm Reactor for Wastewater Treatment

A flexible fibre biofilm reactor was developed for treatment of organic wastewaters.The hydrodynamic characteristics and mass transfer coefficients of oxygen were studied and compared with those of the conventional activated sludge processes.Tracer experiments were performed to obtain the residence time distributions of the reactors.The results indicated that both reactors could be treated as mixed flow reactors.The effects of flow rates of water and air on the overall mass transfer coefficient of oxygen were investigated,and the correlations between the mass transfer coefficient and the ratio of flow rates were obtained.Compared to the conventional activated sludge reactor,the mass transfer coefficients in the flexible fibre reactor were similar to but slightly lower,and less sensitive to the variation in the ratio of flow rates.It indicated that the fibre packing in the reactor hindered the oxygen transfer to some extent.

Dissolved oxygen concentration control in wastewater treatment process based on reinforcement learning

In this article, the dissolved oxygen(DO) concentration control problem in wastewater treatment process(WWTP) is studied.Unlike existing control strategies that control DO concentration at a fixed value, here we develop a different control framework.Under the proposed control framework, an intelligent control method of DO concentration based on reinforcement learning(RL)algorithm is presented to resolve the DO concentration control problem. By using the deep deterministic policy gradient(DDPG)algorithm, the DO concentration of the fifth tank in the activated sludge reactor can be adjusted dynamically. In addition, by designing two different reward functions and by analysing the relationships among effluent quality, energy consumption, and DO concentration, the target of energy-saving and emission-reducing is achieved. The simulation results indicate that the designed control method can reduce energy consumption while ensuring that the effluent quality meet the specified standards.

A modified active disturbance rejection control for a wastewater treatment process

Waste water treatment process(WWTP)control has been attracting more and more attention.However,various undesired factors,such as disturbance,uncertainties,and strong nonlinear couplings,propose big challenges to the control of a WWTP.In order to improve the control performance of the closed-loop system and guarantee the discharge requirements of the effluent quality,rather than take the model dependent control approaches,an active disturbance rejection control(ADRC)is utilized.Based on the control signal and system output,a phase optimized ADRC(POADRC)is designed to control the dissolved oxygen and nitrate concentration in a WWTP.The phase advantage of the phase optimized extended state observer(POESO),convergence of the POESO,and stability of the closed-loop system are analyzed from the theoretical point of view.Finally,a commonly accepted benchmark simulation model no.1.(BSM1)is utilized to test the POESO and POADRC.Linear active disturbance rejection control(LADRC)and the suggested proportion-integration(PI)control are taken to make a comparative research.Both system responses and performance index values confirm the advantage of the POADRC over the LADRC and the suggested PI control.Numerical results show that,as a result of the leading phase of the total disturbance estimation,the POESO based POADRC is an effective and promising way to control the dissolved oxygen and nitrate concentration so as to ensure the effluent quality of a WWTP.

Photosensitivity sources of dissolved organic matter from wastewater treatment plants and their mediation effect on 17α-ethinylestradiol photodegradation

Dissolved organic matter(DOM)from each treatment process of wastewater treatment plants(WWTPs)contains abundant photosensitive substances,which could significantly affect the photodegradation of 17α-ethinylestradiol(EE2).Nevertheless,information about EE2 photodegradation behavior mediated by DOM from diverse WWTPs and the photosensitivity sources of such DOM are inadequate.This study explored the photodegradation behavior of EE2 mediated by four typical WWTPs’DOM solutions and investigated the photosensitivity sources of DOM in the anaerobic-anoxic-oxic(A2/O)process.The parallel factor analysis identified three varying fluorescing components of these DOM,tryptophan-like substances or protein-like substances,microbial humuslike substances,and humic-like components.The photodegradation rate constants of EE2 were positively associated with the humification degree of DOM(P<0.05).The triplet state substances were responsible for the degradation of EE2.DOM extracted from the A2/O process,especially in the secondary treatment process had the fastest EE2 photodegradation rate compared to that of the other three processes.Four types of components(water-soluble organic matter(WSOM),extracellular polymeric substance,humic acid,and fulvic acid)were separated from the A2/O process DOM.WSOM had the highest promotion effect on EE2 photodegradation.Fulvic acid-like components and humic acid-like organic compounds in WSOM were speculated to be important photosensitivity substances that can generate triplet state substances.This research explored the physicochemical properties and photosensitive sources of DOM in WWTPs,and explained the fate of estrogens photodegradation in natural waters.

Singlet oxygen-dominated peroxymonosulfate activation by layered crednerite for organic pollutants degradation in high salinity wastewater

Advanced oxidation processes have been widely studied for organic pollutants treatment in water,but the degradation performance of radical-dominated pathway was severely inhibited by the side reactions between the anions and radicals,especially in high salinity conditions.Here,a singlet oxygen(^(1)O_(2))-dominated non-radical process was developed for organic pollutants degradation in high salinity wastewater,with layered crednerite(CuMnO_(2))as catalysts and peroxymonosulfate(PMS)as oxidant.Based on the experiments and density functional theory calculations,^(1)O_(2)was the dominating reactive species and the constructed Cu-O-Mn with electron-deficient Mn captured electron from PMS promoting the generation of^(1)O_(2).The rapid degradation of bisphenol A(BPA)was achieved by CuMnO_(2)/PMS system,which was 5-fold and 21-fold higher than that in Mn_(2)O_(3)/PMS system and Cu_(2)O/PMS system.The CuMnO_(2)/PMS system shown prominent BPA removal performance under high salinity conditions,prominent PMS utilization efficiency,outstanding total organic carbon removal rate,wide range of applicable pH and good stability.This work unveiled that the^(1)O_(2)-dominated non-radical process of CuMnO_(2)/PMS system overcame the inhibitory effect of anions in high salinity conditions,which provided a promising technique to remove organic pollutants from high saline wastewater.

Bimetallic catalysts as electrocatalytic cathode materials for the oxygen reduction reaction in microbial fuel cell:A review

Microbial fuel cell(MFC) is one synchronous power generation device for wastewater treatment that takes into account environmental and energy issues, exhibiting promising potential. Sluggish oxygen reduction reaction(ORR) kinetics on the cathode remains by far the most critical bottleneck hindering the practical application of MFC. An ideal cathode catalyst should possess excellent ORR activity, stability, and costeffectiveness, experiments have demonstrated that bimetallic catalysts are one of the most promising ORR catalysts currently. Based on this, this review mainly analyzes the reaction mechanism(ORR mechanisms, synergistic effects), advantages(combined with characterization technologies), and typical synthesis methods of bimetallic catalysts, focusing on the application effects of early Pt-M(M = Fe, Co, and Ni) alloys to bifunctional catalysts in MFC, pointing out that the main existing challenges remain economic analysis, long-term durability and large-scale application, and looking forward to this. At last, the research trend of bimetallic catalysts suitable for MFC is evaluated, and it is considered that the development and research of metal-organic framework(MOF)-based bimetallic catalysts are still worth focusing on in the future, intending to provide a reference for MFC to achieve energy-efficient wastewater treatment.

市政污水生化处理过程中曝气控制系统研究进展

为了促进污水处理厂(WWTPs)的低碳可持续运营管理,近年来致力于改善出水质量、削减运营成本和降低温室气体排放的智能曝气控制技术蓬勃发展,但关于可持续污水处理厂的最佳曝气控制策略尚未达成共识。系统综述了曝气过程中溶解氧浓度对于N2O释放的影响,通过分析对比不同曝气控制策略的差异及优缺点,提出曝气控制策略进一步优化的建议,为实现市政污水处理厂溶解氧的综合科学管理提供理论支撑,旨在为污水处理行业提供科学依据和技术支持,促进环境保护和可持续发展。在曝气控制系统中加入N2O排放量化模型来实现出水水质、曝气能耗、温室气体排放三者之间的平衡是未来的关键研究方向,需开发更准确、更合适的温室气体量化模型、灵活的控制方法和智能曝气策略,以满足污水处理厂更多的需求。

The nitritation performance of biofilm reactor for treating domestic wastewater under high dissolved oxygen

The objective of this study was to investigate the nitritation performance in a biofilm reactor for treating domestic wastewater.The reactor was operated in continuous feed mode from phases 1 to 3.The dissolved oxygen（DO）was controlled at 3.5–7 mg/L throughout the experiment.The biofilm reactor showed excellent nitritation performance after the inoculation of nitrifying sludge,with the hydraulic retention time being reduced from 24 to 7 hr.Above 90%nitrite accumulation ratio（NAR）was maintained in phase 1.Afterwards,nitratation occurred with the low NH4^＋–N concentration in the reactor.The improvement of NH4^＋–N concentration to 20–35 mg/L had a limited effect on the recovery of nitritation.However,nitritation recovered rapidly when sequencing batch feed mode was adopted in phase 4,with the effluent NH4^＋-N concentration above 7 mg/L.The improvement of ammonia oxidizing bacteria（AOB）activity and the combined inhibition effect of free ammonia（FA）and free nitrous acid（FNA）on the nitrite oxidizing bacteria（NOB）were two key factors for the rapid recovery of nitritation.Sludge activity was obtained in batch tests.The results of batch tests had a good relationship with the long term operation performance of the biofilm reactor.

Characterization of dissolved organic matter in a dynamic membrane bioreactor for wastewater treatment

This paper systematically examined the characteristics of dissolved organic matter(DOM) in a dynamic membrane bioreactor(DMBR) for municipal wastewater with a laboratory-scale continuous-flow device.Experimental results showed that the system performed excellent pollutants' removal efficiencies.The increase of trans-membrane pressure(TMP) for the dynamic membrane(DM) could be divided into three stages,i.e.,zero increase stage,slow increase stage and abrupt rise stage.The maximal fouling rate of the DM reached to 4.34 kPa/h in abrupt rise stage.It was observed that the polysaccharides(PS) concentration of DOM samples gradually increased from the anaerobic zone to the aerobic zone in sequence,but the proteins(PN) concentration performed an opposite trend.The DM could retain a small part of the large molecular substances(>10 kDa) in the aerobic zone.Two particular fluorescence peaks appeared in the anaerobic zone and in the anoxic zone were also found in the effluent,which illustrated the dynamic cake layer closed to the stainless steel mesh might induce an anaerobic/anoxic micro environment.Based on the three-dimensional excitation-emission matrix(EEM) fluorescence spectroscopy analysis,aromatic proteins,aromatic proteinlike substance,fulvic acid-like substances and soluble microbial by-product-like materials could be biodegraded effectively in the DMBR,and the DM could partly remove the humic acid-like substances and soluble microbial by-product-like materials.

微气泡O_(3)/H_(2)O_(2)深度处理某化工园区二级出水效能与机制

化工园区废水经过二级处理后,仍含有多种有毒污染物,依然对生态环境存在较大风险,为此,建立微气泡O_(3)/H_(2)O_(2)深度处理工艺,研究某工业园区二级出水处理效能,确定最佳工艺参数,探究污染物降解机制,并对处理出水进行毒性评价。结果表明:在pH为7.3、臭氧投加量为60 mg/L、H_(2)O_(2)初始投加量为114 mg/L、反应时间为15 min条件下,微气泡O_(3)/H_(2)O_(2)对二级出水中有毒污染物具有良好的降解效果,COD和TOC去除率分别达到47.41%和46.61%;微气泡O_(3)能够显著提高臭氧利用效率,缩短反应时间;与普通O_(3)曝气相比,臭氧利用率提高10%,反应时间缩短2/3;微气泡O_(3)/H_(2)O_(2)工艺过程中,有机物去除过程遵循表观二级反应动力学;电子顺磁共振(EPR)技术证明羟基自由基(·OH)参与有机物的降解过程,H_(2)O_(2)促进·OH的生成,微气泡曝气强化O_(3)/H_(2)O_(2)产生更多的·OH;二级出水中溶解性有机物(DOM)在深度处理过程中存在大分子物质向小分子物质转化的趋势;H_(2)O_(2)能够增强臭氧对疏水中性组分的去除能力,改变臭氧对污染物的降解途径。添加H_(2)O_(2)后,发光抑制率由100%(微气泡O_(3))降低至20%(微气泡O_(3)/H_(2)O_(2)),表明H_(2)O_(2)能够有效抑制臭氧氧化深度处理过程中急性毒性的升高。

臭氧催化氧化系统在膜法有机浓水深度处理中的应用

洱源县某污水厂处理规模为1.0×10^(4)m^(3)/d,主体工艺为“膜生物反应器(MBR)-纳滤”双膜工艺,其中纳滤系统产生的浓水经臭氧催化氧化处理系统处理后与纳滤产水混合,混合出水主要指标达到国家《地表水环境质量标准》(GB 3838—2002)中Ⅲ类(湖、库)标准,实现污水零排放。臭氧催化氧化处理系统采用两段式设计,处理规模为1000 m^(3)/d。臭氧催化氧化系统通水运行一年后的性能测试显示,系统总体处理效果稳定,臭氧催化氧化处理后化学需氧量(CODCr)平均质量浓度由148.39 mg/L降低到75.45 mg/L,耗电量约为1.85 kW·h/m^(3)。结果表明,臭氧催化氧化工艺是膜法有机浓水深度处理的有效工艺。

浅析污水处理厂的溶解氧与氧化还原电位

随着污水处理技术的不断发展,溶解氧和氧化还原电位逐步成为污水处理过程中重要的综合性水质指标。本文选取典型污水处理厂作为研究对象,了解和掌握污水处理流程中DO、ORP的变化规律以及DO与ORP之间的关系,从而为水质净化提供过程控制参数。

Sustainable micro-activation of dissolved oxygen driving pollutant conversion on Mo-enhanced zinc sulfide surface in natural conditions

The activation of inert oxygen(O_(2))often consumes enormous amounts of energy and resources,which is a global challenge in the field of environmental remediation and fuel cells.Organic pollutants are abundant in electrons and are promising alternative electron donors.Herein,we implement sustainable microactivation of dissolved oxygen(DO)by using the electrons and adsorption energy of pollutants by creating a nonequilibrium microsurface on nanoparticle-integrated molybdenum(Mo)lattice-doped zinc sulfide(ZnS)composites(MZS-1).Organic pollutants were quickly removed by DO microactivation in the MZS-1 system under natural conditions without any additional energy or electron donor.The turnover frequency(TOF,per Mo atom basis)is 5 orders of magnitude higher than those of homogeneous systems.Structural and electronic characterization technologies reveal the change in the crystalline phase(Zn-S-Mo)and the activation of π-electrons on six-membered rings of ZnS after Mo doping,which results in the formation of a nonequilibrium microsurface on MZS-1.This is the key for the strong interfacial interaction and directional electron transfer from pollutants to MZS-1 through the delocalized π-π conjugation effect and from MZS-1 to DO via Zn-S-Mo,as demonstrated by electron paramagnetic resonance(EPR)techniques and density functional theory(DFT)calculations.This process achieves the efficient use of pollutants and the low-energy activation of O_(2) through the construction of a nonequilibrium microsurface,which shows new significance for water treatment.

活性污泥过程溶解氧浓度预测

溶解氧浓度是活性污泥法污水处理过程中的重要过程参数。准确的溶解氧浓度测量是保证出水水质达标以及节能生产的前提,对此,提出了一种基于优化神经网络的溶解氧浓度软测量模型。首先,将自适应步长策略和学习策略引入标准的麻雀搜索算法,提高了算法的搜索能力和搜索精度。其次,为了提高溶解氧浓度的预测精度和效率,采用改进麻雀搜索算法用于优化BP神经网络模型参数,并以自动获取的最佳参数组合构建溶解氧软测量模型。最后,利用该软测量模型对国际基准仿真模型BSM1和实际污水处理过程的溶解氧浓度进行预测。仿真结果表明:与BP、RBF、ELM、JS-BP和PSO-BP等预测模型相比,ISSA-BP预测模型的预测精度更高,收敛速度更快,具备更好的实践应用价值。

海拔对生活污水处理厂生化池曝气量影响探讨

我国地域广阔,平均海拔跨度大,海拔越高氧气越稀薄、气压越低,对污水处理厂标准传氧速率和曝气量具有明显影响。本文结合相关工程实例,对0、500、1000、1500、2000、2500、3000、3500、4000、4500、5000 m海拔下生化池实际需氧量、标准传氧速率和曝气量相关参数进行计算和校核。结果表明,考虑氧分压修正工况下曝气量与未考虑修正工况下差值随着海拔增加逐渐增大;实际需氧量不受海拔影响;标准传氧速率、供气量与海拔呈现一定指数关系,高海拔地区标准传氧速率和曝气量成倍增长,与平原地区差距显著。该研究结果也可为相关高原地区生化池曝气量的计算和设备选型提供参考。

火电厂废水处理过程中氧腐蚀问题的应对策略研究

在火电厂废水处理过程中,特别是在曝气池和滤池处理环节容易出现氧腐蚀问题,导致设备损坏和效率下降。基于此,研究火电厂废水处理过程中的氧腐蚀问题,并探索缓蚀阻垢剂的用量,提高废水处理系统的处理效率和使用寿命。分析了共聚物缓蚀阻垢剂的制备过程,并进行性能测试实验,验证其缓蚀阻垢效果。结果表明,该缓蚀阻垢剂配方在实验条件下表现出了良好的缓蚀性能和阻垢性能,且旋转挂片法实验和碳酸钙沉积法实验结果均符合规范要求。

某电厂1000MW超超临界机组给水加氧异常原因分析

某1000MW超超临界机组在给水加氧出现了省煤器入口溶解氧异常降低的现象。通过排查机组运行日志、加氧系统、水汽品质和取样系统,结果表明:给水取样系统在高负荷下的加氧转化不完全,引起氧的消耗量增大,导致省煤器入口溶解氧降低。高温取样架运行排污过程中,高温、高压、高流速样水经过未完全钝化的Y型过滤器滤网,表面的钝化膜发生部分脱落,再度修复引起氧的消耗量增大,造成省煤器入口溶解氧降低。