Treatment of oilfield produced water by anaerobic process coupled with micro-electrolysis

Treatment of oilfield produced water was investigated using an anaerobic process coupled with micro-electrolysis (ME), focusing on changes in chemical oxygen demand (COD) and biodegradability. Results showed that COD exhibited an abnormal change in the single anaerobic system in which it increased within the first 168 hr, but then decreased to 222 mg/L after 360 hr. The biological oxygen demand (five-day) (BOD5)/COD ratio of the water increased from 0.05 to 0.15. Hydrocarbons in the wastewater, such as pectin, degraded to small molecules during the hydrolytic acidification process. Comparatively, the e ect of ME was also investigated. The COD underwent a slight decrease and the BOD5/COD ratio of the water improved from 0.05 to 0.17 after ME. Removal of COD was 38.3% under the idealized ME conditions (pH 6.0), using iron and active carbon (80 and 40 g/L, respectively). Coupling the anaerobic process with ME accelerated the COD removal ratio (average removal was 53.3%). Gas chromatography/mass spectrometry was used to analyze organic species conversion. This integrated system appeared to be a useful option for the treatment of water produced in oilfields.     

Physiological responses and detoxific mechanisms to Pb, Zn, Cu and Cd in young seedlings of Paulownia fortunei

Paulownia fortunei has been successfully used in the phytoremediation of many Pb/Zn mine tailings. However, seed germination and young seedlings of P. fortunei rarely occurred in these mine tailings. The physiological responses and detoxific mechanisms of P. fortunei young seedling to Pb, Zn, Cu and Cd stress were investigated. The germinated rate, shoot length, chlorophyll and carotenoid contents in leaves of young seedlings had a great reduction under Zn and Cu treatments, but had little decrease under Pb and Cd treatments. The production rate of O₂^•−, H₂O₂ and malondialdehyde (MDA) contents significantly increased in response to added Zn and Cu indicating great oxidative stress for young seedlings, but they had no significant change to added Pb and Cd. Young seedlings had effective detoxific mechanism to Pb and Cd, as antioxidant enzymes activities, phytochelatins (PCs-SH) and proline contents increased with increasing rates of added Pb and Cd. However, young seedlings had un-effective detoxific mechanisms to Zn and Cu stress. Results revealed the heavy metals (such as Cu) that present at low concentrations in mine tailings may be major constraint for the survival of young seedlings.     

Effect of chemical and thermal activations on the properties of rice husk ash-based solidified wastes

Strength development,leachability and microstructure of heavy metals from the solidified waste using synthesis rice husk ash (sRHA) and lime blended at the weight ratio of 1:1 were used as binders.The heavy metal-containing sludge was used at the level of 0 wt.%,30 wt.%,and 50 wt.% dry weight,respectively.The sample specimens with and without 1.5 wt.% of sodium silicate (SiO 2 /Na 2 O=1.0) were cured under the ambient condition and elevated temperature curing at 50°C for 24 hr.Experimental results showed that the introduction of sodium silicate solution and elevated temperature curing to sRHA-based solidified waste containing 30 wt.% of heavy metal sludge gave one day strength of 20 kg/cm 2 compared to 0.9 kg/cm2 for the control sample.XRD patterns indicated that most metal-sulfides present in the sludge were appeared in the solidified waste and SEM coupled with EDX techniques reveal these metal-sulfide particles were trapped within the lime-sRHA matrices.In addition,cumulative leaching behavior by tank test (EA NEN 7375:2004) showed that solidified waste containing up to 30 wt.% of heavy metal sludge was suitable to dispose in a secured landfill.     

Heavy metals in rice and garden vegetables and their potential health risks to inhabitants in the vicinity of an industrial zone in Jiangsu, China

Contamination of soil and agricultural products by heavy metals resulting from rapid industrial development has caused major concern. In this study, we investigated heavy metal (Cu, Zn, Pb, Cr, Hg and Cd) concentrations in rice and garden vegetables, as well as in cultivated soils, in a rural-industrial developed region in southern Jiangsu, China, and estimated the potential health risks of metals to the inhabitants via consumption of locally produced rice and garden vegetables. A questionnaire-based survey on dietary consumption rates of foodstuffs showed that rice and vegetables accounted for 64% of total foodstuffs consumed, and over 60% of rice and vegetables were grown in the local region. Average concentrations of Cr, Cu, Zn, Cd, Hg and Pb were 0.75, 2.64, 12.00, 0.014, 0.006 and 0.054 mg/kg dw (dry weight) in rice and were 0.67, 1.18, 4.34, 0.011, 0.002 and 0.058 mg/kg fw (fresh weight) in garden vegetables, respectively. These values were all below the maximum allowable concentration in food in China except for Cr in vegetables. Leafy vegetables had higher metal concentrations than solanaceae vegetables. Average daily intake of Cr, Cu, Zn, Cd, Hg and Pb through the consumption of rice and garden vegetables were 5.66, 16.90, 74.21, 0.10, 0.04 and 0.43 μg/(kg·day), respectively. Although Hazard Quotient values of individual metals were all lower than 1, when all six metal intakes via self-planted rice and garden vegetables were combined, the Hazard Index value was close to 1. Potential health risks from exposure to heavy metals in self-planted rice and garden vegetables need more attention.     

Fractionation of heavy metals in shallow marine sediments from Jinzhou Bay, China

This work investigated the distribution and speciation of Cd, Cu, Pb, Fe and Mn in the shallow sediments of Jinzhou Bay, Northeast China, which has been heavily contaminated by nonferrous smelting activities. The concentrations of Cd, Cu and Pb in sediments were found to be 100, 13 and 7 times, respectively, being higher than the national guideline (GB 18668-2002). Sequential extraction test showed that 39%-61% of Cd were exchangeable fractions, indicating that Cd in the sediments posed a high risk to local...     

Releases of phosphate fertilizer industry in the surrounding environment: Investigation on heavy metals and polonium-210 in soil

Distribution of Cu,Zn,Pb,Cr,Ni,Mn concentrations and the activity of polonium-210 in the surrounding area of a phosphate fertilizer industry located on the eastern coast of the Mediterranean Sea has been determined.Nineteen sampling sites were distributed around the industrial zone on a surface area of about 100,000 m2.Atomic absorption spectroscopy and Alpha spectroscopy were used to quantify the heavy elements and polonium-210,respectively.Investigation on a particle scale was conducted by TEM and SEM coupled to EDX and X-ray cartography to determine the nature of heavy elements carriers and their distribution.Heavy elements were mainly concentrated inside the particle size fraction 50 μm.Their levels decreased with distance increasing from the industry.According to the reference soil,enrichment factors were about 10,15,32 and 100 times for Zn,Pb,Cu,and Cr,respectively inside the particle size fraction 50 μm on the closest sites to the industry.The main contaminant sources were transport and storage of row materials and the free release of phosphogypsum waste.Heavy elements were entrapped inside agglomerates of sulfates,phosphates and iron oxihydroxides in a di used shape.Polonium-210 with an enrichment factor of about 56,showed the same behavior of the spatial distribution of the trace elements.     

Carbonaceous particles in the atmosphere and precipitation of the Nam Co region, central Tibet

A continuous air and precipitation sampling for carbonaceous particles was conducted in a field observatory beside Nam Co, Central Tibetan Plateau during July of 2006 through January of 2007. Organic carbon (OC) was the dominant composition of the carbonaceous particles both in the atmosphere (1660 ng/m³) and precipitation (476 ng/g) in this area, while the average elemental carbon (BC) concentrations in the atmosphere and precipitation were only 82 ng/m³ and 8 ng/g, respectively. Very high OC/BC ratio suggested local secondary organic carbon could be a dominant contribution to OC over the Nam Co region, while BC could be mainly originated from Southern Asia, as indicated by trajectory analysis and aerosol optical depth. Comparison between the BC concentrations measured in Lhasa, those at “Nepal Climate Observatory at Pyramid (NCO-P)” site on the southern slope of the Himalayas, and Nam Co suggested BC in the Nam Co region reflected a background with weak anthropogenic disturbances and the emissions from Lhasa might have little impact on the atmospheric environment here, while the pollutants from the Indo-Gangetic Basin of Southern Asia could be transported to the Nam Co region by both the summer monsoon and the westerly.     

上海宝山区农用土壤重金属分布与来源分析

以上海宝山区为典型区域,在获取216个农用表层土壤样品重金属实测数据的基础上,运用多元统计和地统计相结合的方法,对上海宝山区农用土壤重金属的含量水平、分布特征和来源进行系统分析.结果表明,上海市宝山区农用土壤重金属Cd、Hg、As、Cr、Pb、Cu、Zn的平均含量值分别为0.195、0.148、7.44、82.5、29.1、33.2、124.5 mg.kg-1,均没有超过国家土壤环境质量二级标准,但Cd、Zn、Cr、Pb、Cu、Hg元素平均含量值超过上海市土壤背景值,其中Cd、Hg、Zn最为显著,分别是对应背景值的1.50、1.48、1.45倍,呈现出明显的累积趋势.相关分析和因子分析结果显示,各元素的来源可分为三类,Zn、Cd、Hg和Pb为一类,Cr和Cu为一类,As单独为一类;前两类元素含量远高于对应元素背景值,来源主要受各种人为活动影响,As元素含量与背景值相当,各样品含量的变异程度最低,来源主要与成土母质有关.空间结构分析表明,As元素以土壤母质、地形等结构性变异为主,其它元素主要受人为活动等随机因子影响;通过对临界值概率等值线的分布分析发现,Cd、Zn、Cr、Cu、Hg来源以点源为主,来源较为集中,Pb来源相对较为分散.     

水中Cu~(2+)、Ni~(2+)与腐殖酸、膨润土的相互作用研究

研究了Cu2+、Ni2+与腐殖酸以及膨润土与腐殖酸的共存吸附剂的相互作用,考察了相互作用时间、初始pH、温度对相互作用的影响.结果表明,金属离子的去除率随时间增加而增大,吸附量随温度升高而增大.初始pH对Cu2+、Ni2+的去除率影响很大,pH在中性范围附近Cu2+、Ni2+的去除率可以达到最大.吸附动力学实验表明,Cu2+、Ni2+在腐殖酸及共存吸附剂上的吸附符合伪二级吸附速率模型,并得到Cu2+在腐殖酸及共存吸附剂上吸附的活化能Ea分别为17.01和38.49 kJ.mol-1,Ni2+在腐殖酸及共存吸附剂上吸附的活化能Ea分别为15.15和13.35 kJ.mol-1,表明吸附过程以物理吸附为主.Cu2+、Ni2+在腐殖酸及共存吸附剂上的吸附符合Langmuir等温线模型.得到的ΔH0、ΔS0和ΔG0表明金属离子在腐殖酸及共存吸附剂上的吸附是一个吸热、熵增、自发的过程.     

摩尔配比对MAP沉淀法回收模拟废水中磷的影响

以磷浓度50mg/L的实验室模拟废水为研究对象,考察了以鸟粪石(MAP)形式回收磷的最佳摩尔配比,并借助X-衍射(XRD)对不同摩尔配比条件下得到的沉淀物进行分析。试验结果表明,在pH=9.5时,以鸟粪石形式回收磷的最佳Mg:N:P=4:1.6:1。对沉淀物的XRD分析发现,在pH=9.5,当固定Mg:P=1.6时,N:P=1时沉淀物中基本不含MAP,当N:P=2时,生成的沉淀物中混有少量的副产物Mg(3PO)42,当N:P2时则生成较纯的MAP;当固定N:P=4时,Mg:P=2是生成较纯的MAP的临界值,超过此比例则生成副产物Mg(3PO)42;当反应按照理论配比投加氨氮和镁盐时,所得产物基本不是MAP,而是副产物Mg(3PO)42。故鸟粪石沉淀结晶反应中应尽量提高氨氮配比,并避免投加过量的镁盐,以保证回收产物的纯度。