Aerobic N2O emission for activated sludge acclimated under different aeration rates in the multiple anoxic and aerobic process

Nitrous oxide (N₂O) is a potent greenhouse gas that can be emitted during biological nitrogen removal. N₂O emission was examined in a multiple anoxic and aerobic process at the aeration rates of 600 mL/min sequencing batch reactor (SBR_L) and 1200 mL/min (SBR_H). The nitrogen removal percentage was 89% in SBR_L and 71% in SBR_H, respectively. N₂O emission mainly occurred during the aerobic phase, and the N₂O emission factor was 10.1% in SBR_L and 2.3% in SBR_H, respectively. In all batch experiments, the N₂O emission potential was high in SBR_L compared with SBR_H. In SBR_L, with increasing aeration rates, the N₂O emission factor decreased during nitrification, while it increased during denitrification and simultaneous nitrification and denitrification (SND). By contrast, in SBR_H the N₂O emission factor during nitrification, denitrification and SND was relatively low and changed little with increasing aeration rates. The microbial competition affected the N₂O emission during biological nitrogen removal.     

强化除磷曝气生物滤池反冲洗优化及其污泥特性

为探讨BAF(曝气生物滤池)最佳反冲洗强度及其选择依据,以某处理石化二级出水的强化除磷BAF为研究对象,采取不同的反冲洗强度进行气-水联合反冲洗,探讨反冲洗过程中出水污泥量峰值出现时间、污泥的SOUR(比好氧呼吸速率)变化、反冲洗前后微生物量和微生物脱氢酶活性(DHA)的变化以及反冲洗后的恢复效果,并对反冲洗强度参数的选择进行了优化. 结果表明:在该研究条件下,采用气洗〔强度为12 L/(m2·s)〕4 min,气-水联合洗〔气洗强度为12 L/(m2·s),水洗强度为6 L/(m2·s)〕5 min,最后用清水漂洗9 min的反冲洗方式,排水中污泥的ρ(SS)可在最短时间(3 min)达到峰值;反冲洗排水中污泥的SOUR较低,平均值为0.5 mg/(mg·h);距离底端进水口1.3和2.2 m处的滤料层微生物的量损失较小,分别为4.4%和5.3%,其相应微生物的活性有所增加. 研究显示,该条件下反冲洗可有效清除滤料颗粒间所截留及滤料表面脱落的老化生物膜,并可保留适量活性较高的生物膜,强化了传质条件,反冲洗后对污染物的处理能力能恢复迅速.      

从含铬铝泥中回收铝的新工艺

采用"打浆水洗除Cr(Ⅵ)—电渗析除Cr(Ⅵ)—碱浸提铝—碳酸化分解法精制Al_2O_3"的新工艺处理含铬铝泥(以下简称铝泥),并回收Al_2O_3。实验结果表明:铝泥在70℃下经3次打浆水洗后,w(Na_2CrO_4)(以干铝泥计)降至5.0%;采用电渗析除Cr(Ⅵ)工艺可有效去除铝泥中以结合态和结晶态形式存在的Na_2CrO_4,在55 V直流电压下电渗析6h后铝泥中的w(Na_2CrO_4)降至0.98%;在碱浸温度为100℃、碱浸时间为3 h、NaOH质量浓度为150 g/L的优化碱浸条件下,铝浸出率(以Al_2O_3计)高达90.0%;经3次碳酸化分解处理后,Al_2O_3产品的纯度达98.65%,满足GB/T 24487-2009《氧化铝》中的一级标准,Al_2O_3回收率为96.37%。     

ClO_2溶液去除烟气中NO的效果及工程应用

采用实验室规模喷淋脱硝装置对ClO_2溶液去除NO的效果及影响因素进行探讨,通过脱硝产物的测定对ClO_2溶液去除NO的能力及机理进行分析;在此基础上考察ClO_2溶液对供热厂燃煤锅炉烟气的实际脱硝效果。实验结果表明:在液气比为20L/m~3、反应温度为20℃,反应pH为4.0、进气NO质量浓度为250 mg/m~3,ClO_2质量浓度为200 mg/L的条件下,NO去除率达97%以上;ClO_2溶液可将NO氧化吸收为NO_3~-,氧化后产生的NO_x也可被NaOH溶液吸收转化为NO_2~-和NO_3~-;在ClO_2质量浓度为200~500 mg/L,反应pH为5.5~7.0的条件下处理初始NO质量浓度为212~230 mg/m~3的燃煤锅炉烟气,NO去除率为85.7%~94.6%,NO_x去除率为80.4%~88.8%,出口NO_x质量浓度低于46 mg/m~3,远低于GB 13271—2014规定的排放限值。     

高效重金属捕集剂EDTC的结构表征及对酸性络合铜的去除特性研究

以乙二胺和二硫化碳为反应物,无水乙醇和去离子水的混合溶液为溶剂,制备了一种巯基类重金属捕集剂N,N-双(二硫代羧基)乙二胺(EDTC),采用紫外光谱、红外光谱和元素分析对其结构进行表征,重点研究了其对EDTA络合铜、柠檬酸络合铜和酒石酸铜3种酸性模拟络合铜的去除性能及螯合沉淀物的溶出特性,并探讨了EDTC脱除络合铜的机理.研究结果表明,处理50 mg·L-1的含铜废水,p H值范围为3~9,EDTC投加量为mEDTC/mCu=8(质量比),反应时间3 min,PAM投加量为1 mg·L-1,此时出水Cu2+浓度均低于0.25 mg·L-1,去除率达到99.5%以上.螯合沉淀物在弱酸性和弱碱性条件下很稳定,不易产生二次污染.红外光谱图分析结果表明,EDTC与Cu会发生螯合反应,即EDTC直接脱出络合铜中Cu2+,并与Cu2+生成难溶的螯合产物EDTC-Cu,进而有效地去除废水中Cu.     

Preparation, characterization and performance of poly(m-phenylene isophthalamide)/organically modified montmorillonite nanocomposite membranes in removal of perfluorooctane sulfonate

Nanocomposite membranes containing poly(m-phenylene isophthalamide) (PMIA) and organically modified montmorillonite (OMMT) were prepared by a combination of solution dispersion and wet-phase inversion methods, and the effects of OMMT addition on the properties and performance of fabricated nanofiltration membranes were investigated. The membranes were characterized by contact angle measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis, and zeta potential. The performance of the membranes was elucidated by the removal of perfluorooctane sulfonate (PFOS) at neutral pH. Increasing OMMT concentration improved the thermal stability and hydrophilicity of the membranes. The permeation and rejection of PFOS were significantly improved. The performance of fabricated nanofiltration membranes in removal of PFOS varied depending on the solute and membrane properties as well as solution conditions. Finally, a comparison between fabricated membranes and a commercial NF membrane (ESNA1-K1, Hydecanme) proved that the OMMT addition is a convenient procedure for producing nanocomposite membranes with superior properties and performance.     

New insight into adsorption characteristics and mechanisms of the biosorbent from waste activated sludge for heavy metals

The adsorption characteristics and mechanisms of the biosorbent from waste activated sludge were investigated by adsorbing Pb2+and Zn2+in aqueous single-metal solutions. A p H value of the metal solutions at 6.0 was beneficial to the high adsorption quantity of the biosorbent. The optimal mass ratio of the biosorbent to metal ions was found to be 2. A higher adsorption quantity of the biosorbent was achieved by keeping the reaction temperature below 55°C. Response surface methodology was applied to optimize the biosorption processes, and the developed mathematical equations showed high determination coefficients(above 0.99 for both metal ions) and insignificant lack of fit(p = 0.0838 and 0.0782 for Pb2+and Zn2+, respectively). Atomic force microscopy analyses suggested that the metal elements were adsorbed onto the biosorbent surface via electrostatic interaction. X-ray photoelectron spectroscopy analyses indicated the presence of complexation(between –NH2,-CN and metal ions) and ion-exchange(between –COOH and metal ions). The adsorption mechanisms could be the combined action of electrostatic interaction, complexation and ion-exchange between functional groups and metal ions.     

同时脱硫脱硝固态反应剂研究进展

针对于干法同时控制热力发电厂NO_x和SO_2的排放,综述了近年来研究较广泛的钙基吸收剂、改性活性炭吸收剂、γ-Al_2O_3吸收-催化剂、天然锰矿石反应剂等几种同时脱硫脱硝固态反应剂的结构特性,以及脱硫脱硝效率。根据这几种固态反应剂的研究现状指出了应更进一步对氮氧化物和硫氧化物在同时脱除时的相互影响进行研究,从而提高同时脱硫脱硝效率。     

湖北某重金属污染土壤稳定化/固化治理工程实例

为保证南水北调水源地水质安全,该项工程对湖北省郧县境内4个关停搬迁企业原址约16万m3重金属污染土壤进行了修复治理。污染土壤清挖标准为《展览会用地土壤环境质量标准》(HJ350—2007)A级标准,污染土壤无害化处理验收标准为浸出液浓度低于《地表水环境质量标准》(GB3838—2002)中IV类水体标准值。工程采用异位稳定化/固化技术对重金属污染土壤进行了无害化处理,所用稳定化/固化药剂为施工单位自主研发的硫系和铁系稳定化药剂;无害化处理后的近20万m3土壤采用安全填埋进行处置。工程的成功实施为南水北调库区水质安全提供了有力保障。     

中国有色金属行业绿色发展和技术转型

我国有色金属行业发展迅速,铜、铝、铅、锌等10种有色金属产量占世界的40%以上。我国有色金属行业在资源节约、环境友好型产业的方针指导下,不断推动主体工艺技术进步,技术装备水平进入世界先进行列,重金属污染物防治、废物综合利用取得新进展,清洁生产取得显著成果,末端技术取得新突破。目前有色金属行业环境污染压力依然很大,需切实转变发展方式,继续走绿色发展之路。