Complexing agents in waste waters of finnish electrolytic and chemical surface treatment plants

Goal, Scope and Background  Complexing agents are one of the major environmental concerns in electrolytic and chemical surface treatment (ECST) industry; e.g. the EU reference document on the best available technology (BREF) pays special attention to the usage of EDTA. However, no comprehensive studies are available on usage of EDTA or other complexing agents or their load to the receiving waters from ECST industry. In this study, the concentrations of complexing agents were analyzed to get an overview of their usage and load and also to recognize their relevance in the environmental permitting and compliance monitoring of such facilities. Methods  Complexing agent concentrations of treated waste water samples of 23 ECST plants with vat volume exceeding 30 m³ was studied. HPLC and GC-MS were used to analyze and identify complexing agent concentrations, ICP-AES to analyze metals, and TOC to analyse the organic load. The number of the plants in this study equals around 50% of such installations in Finland subject to environmental permit as the IPPC directive provides. Results  EDTA, DTPA, and NTA were found in 11 samples out of 23 mainly in rather small concentrations. Their annual load to the receiving waters may be estimated to be 0.3 tons and the total load from Finnish ECST industry can be extrapolated to be up to 1 ton. Compared to the estimated use of 5–10 tons in the industry this finding is rather low, even though in Finland cast-off treatment baths are typically delivered to the hazardous waste treatment plants. Discussion  Since the load of complexing agents is rather low, the chemical waste water treatment seems to be either capable of reducing complexing agent concentrations to some extent or their usage is lower than expected. On the other hand, it is possible that not all complexing agents were identified from the samples. The metal concentrations and TOC were well hand in hand with concentrations found in the Finnish environmental database, which proves that the samples were of average quality of the waste water from the facilities. Conclusions  According to the results, complexing agents cannot be considered as an environmental risk in the ECST industry in Finland; EDTA concentrations are clearly below PNEC_aqua (2.2 mg/l) and the total discharge is very marginal compared to the discharge from the pulp and paper industry. However, DPTA seems to be as commonly used as EDTA, but also biodegradable NTA was found. Recommendations and Perspectives  Since EDTA has gained plenty of attention in the BREF, DTPA and other, poorly biodegradable complexing agents should also be taken into account when the BREF is updated within a few years. Also an EU risk assessment report especially for DTPA should be supplied, since its use is obviously increasing.     

Chelant-aided enhancement of lead mobilization in residential soils

Chelation of metals is an important factor in enhancing solubility and hence, availability to plants to promote phytoremediation. We compared the effects of two chelants, namely, ethylenediaminetetraacetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS) in enhancing mobilized lead (Pb) in Pb-based paint contaminated residential soils collected from San Antonio, Texas and Baltimore, Maryland. Batch incubation studies were performed to investigate the effectiveness of the two chelants in enhancing mobilized Pb, at various concentrations and treatment durations. Over a period of 1 month, the mobilized Pb pool in the San Antonio study soils increased from 52 mg kg⁻¹ to 287 and 114 mg kg⁻¹ in the presence of 15 mM kg⁻¹ EDTA and EDDS, respectively. Stepwise linear regression analysis demonstrated that pH and organic matter content significantly affected the mobilized Pb fraction. The regression models explained a large percentage, from 83 to 99%, of the total variation in mobilized Pb concentrations.     

微生物菌剂与新型填料联用除磷研究

以模拟含磷废水作为研究对象,研究不同工况条件下,复合微生物制剂、新型填料以及复合微生物制剂与新型填料结合对模拟含磷废水中磷的去除效果。实验结果表明:复合微生物制剂在曝气并且与新型填料结合的条件下对总磷的去除效率较高。对ρ(COD)<1 000 mg/L,ρ(TP)为15.34～20.96 mg/L的模拟含磷废水进行总磷的去除,其最佳工况参数为:复合微生物制剂投加量为0.2 g/L,pH值为9,曝气时间为48 h,反应时间为60 h。     

基于成组生物毒性测试的PM2.5毒性

为了准确评估PM_(2.5)的综合生物毒性,采用发光细菌急性毒性、斑马鱼胚胎急性毒性和体外人肺腺癌细胞(A549)毒性试验对常州市冬季雾-霾天、冬季正常天和夏季这3个时间段的PM_(2.5)进行生物毒性评价,并结合大气理化指标进行分析.结果表明,3个时间段的PM_(2.5)均表现出急性毒性或发育毒性.冬季雾-霾天、冬季正常天和夏季PM_(2.5)对发光细菌的毒性单位(toxicity unit,TU)值分别为1. 74(有毒)、1. 19(有毒)和0. 92(微毒);对斑马鱼胚胎的TU值从大到小排列为:冬季正常天(TU=1. 14,有毒)、冬季雾-霾天(TU=0. 79,微毒)和夏季(TU=0,无毒);对A549的TU值为:冬季雾-霾天(TU=0. 61,微毒)夏季(TU=0. 38,微毒)冬季正常天(TU=0. 31,微毒).在发育毒性方面,除夏季PM_(2.5)样品,其余2个时间段的PM_(2.5)均对斑马鱼胚胎发育有影响,主要表现出心包囊肿、脊椎弯曲和尾部畸形.平均毒性(average toxicity,Av Tx)、毒性指数(toxic print,Tx Pr)和最敏感测试(most sensitive test,MST)综合毒性评价方法表明冬季雾-霾天和冬季正常天PM_(2.5)均表现出有毒,夏季则表现出微毒,以冬季雾-霾天PM_(2.5)样品的综合毒性最高.此外,3种测试生物对PM_(2.5)污染物的敏感度排序为发光细菌斑马鱼胚胎 A549.理化指标和生物毒性的相关性分析结果表明,PM_(2.5)中所含的污染物对生物毒性效应产生影响,可为PM_(2.5)生物毒性综合评价和人体健康风险评估提供依据.     

粉煤灰铁屑组合处理印染废水的研究

提出采用粉煤灰和铁屑组合处理印染废水的方法。该方法以电化学作用为主 ,兼有还原、物理吸附和混凝等多种机制。试验研究了实际应用的最佳条件 ,结果表明 ,处理后印染废水的COD和色度去除率分别达到 77%和 95 %。     

无纺布填料处理污水试验及机理

采用无纺布作为一种新型悬浮填料,探索无纺布填料处理污水的适用条件、运行参数及降解机理.研究认为不同容积负荷应采取不同的填料投配率:当CODCr容积负荷低于1.2kg/(m³·d)时,取填料投配率为20%;当CODCr容积负荷在1.2～2.0kg/(m³·d)之间时,取填料投配率为38%;当CODCr容积负荷达2.0 kg/(m³·d)以上时,取填料投配率为29%模型结果表明,附着微生物降解有机物的规律可用Monod方程的形式描述.     

Fabrication of PVDF nanofibrous hydrophobic composite membranes reinforced with fabric substrates via electrospinning for membrane distillation desalination

To improve the mechanical properties of the electrospun nanofibrous membrane, the nonwoven fabrics and spacer fabrics were employed as support substrates to fabricate polyvinylidene fluoride(PVDF) nanofibrous composite membranes. The influences of the substrate on membrane morphology, hydrophobicity, pore size and pore size distribution,porosity, mechanical strength and permeability were comprehensive evaluated. The electrospun composite membranes had a three dimension bead-fiber interconnected open structure and a rough membrane surface. The membrane surface presented a multilevel re-entrant structure and all the water contact angles were above 140°. In contrast with the pure PVDF nanofibrous membrane, the stress at break and the elastic modulus of the composite membranes increased by 4.5–16 times and 17.5–37 times, respectively. Since the spacer fabrics had less resistance to mass transfer, the membranes composited with spacer fabrics exhibited greater permeate fluxes compared with the composite membranes with the nonwoven fabrics as substrates.During the membrane distillation test, the highest permeate flux was up to 49.3 kg/m~2/hr at the feed temperature of 80°C. The long-time and repeat operation of membrane distillation desalination indicated the fabricated membrane with a good resistance to scaling and wetting.The results suggested the potential of the electrospun composite membrane for membrane distillation application.     

强化混凝处理制革废水的优化研究

对皮革废水混凝处理的条件进行优化,分别采用FeSO4·7H2O和阳离子聚丙烯酰胺作为混凝剂和助凝剂,以COD、总铬和硫化物为指标,设计正交试验确定强化混凝处理皮革废水的最优条件并进行验证性试验。结果表明:当FeSO4·7H2O投加量为1800mg/L,阳离子聚丙烯酰胺投加量为7.5mg/L,pH为10,混凝效果最好,对COD、总铬和硫化物的平均去除率分别为14.92%、99.40%和99.71%。     

应用于Anammox-MBR的尼龙织布亲水改性研究

采用聚乙烯醇（PVA）对尼龙织布表面涂覆改性,对改性前后织布进行表征并进行纯水通量测试,随后以牛血清蛋白（BSA）模拟污染物测试尼龙织布改性前后的抗污染性能,并对改性后的织布进行溶解性有机碳（DOC）浸出实验.改性过程中,优选3%涂覆浓度和250μm涂层厚度,改性后织布的纯水通量值约提高85.0%,对BSA的截留率由6.0%±0.5%上升至7.2%±0.7%,通量恢复率由90.0%提高到96.1%,可逆污染比重上升,不可逆污染比重下降,污染形式主要表现为可逆污染.为避免改性尼龙织布应用于厌氧氨氧化-膜生物反应器（Anammox-MBR）时对厌氧氨氧化反应产生不可逆危害,提出应对制备完成的改性尼龙织布进行为期3d及以上的静态清水浸泡或动态浸出处理.     

铬渣污染土壤稳定化技术研究

选用3种不同类型的铬渣污染土壤(A土、B土和C土)作为研究对象,探讨了6种稳定化药剂对污染土壤中Cr(Ⅵ)的还原效果,并研究了不同药剂对各形态Cr稳定化效果。结果表明:FeSO4和Na2S对Cr(Ⅵ)都有很好的还原效果,葡萄糖次之,Na2SO3效果一般,柠檬酸和腐植酸效果不好;FeSO4和Na2S对B土、C土中Cr(Ⅵ)的还原率达到90%以上,对A土中Cr(Ⅵ)的还原率则低于85%;稳定化药剂主要是将酸可提取态Cr转化为其他形态,FeSO4效果最明显,可将80%以上的酸可提取态Cr转化为其他形态,主要为可还原态Cr;葡萄糖主要将之转化为可氧化态Cr;鉴于FeSO4的良好的还原效果,选择FeSO4作为稳定化药剂,且FeSO4添加量为理论投加量的20时较合适,浸出液可以满足地下水三级标准的50μg/L;经济性分析,处理1t清洗后土壤的药品费用为8.91元。