Debromination of decabromodiphenyl ether by organo-montmorillonite-supported nanoscale zero-valent iron：Preparation, characterization and influence factors

An organo-montmorillonite-supported nanoscale zero-valent iron material(M-NZVI) was synthesized to degrade decabromodiphenyl ether(BDE-209). The results showed that nanoscale zero-valent iron had good dispersion on organo-montmorillonite and was present as a core-shell structure with a particle size range of nanoscale iron between 30–90 nm, characterized by XRD, SEM, TEM, XRF, ICP-AES, and XPS. The results of the degradation of BDE-209 by M-NZVI showed that the efficiency of M-NZVI in removing BDE-209 was much higher than that of NZVI. The efficiency of M-NZVI in removing BDE-209 decreased as the pH and the initial dissolved oxygen content of the reaction solution increased, but increased as the proportion of water in the reaction solution increased.     

Enhanced struvite recovery from wastewater using a novel cone-inserted fluidized bed reactor

The feasibility of struvite recovery at low （12.5 mg/L） and high （120 mg[L） phosphorus concentrations was studied by constructing a novel fluidized bed reactor with cones （FBRwc） and without cones （FBRwoc）. The crystallization process was continuously operated for 133 days under different hydraulic retention times （HRT = 1-10 hr）, pH （7.5-10）, and molar ratios of Mg/P （0.75-1.75）, N/P （1-10） and Ca/Mg （0-2）. The optimum operating conditions of HRT, pH, Mg/P and N/P molar ratios were found to be 2 hr, 9, 1.25, and 7.5, respectively. Under these optimum conditions, the phosphorus precipitation efficiencies of FBRwc were 93% for low and 98% for high phosphorus influent; however, the efficiencies were 78% and 81% for FBRwoc, respectively. Due to crystal losses at each junction （17%-31%）, the crystal recovery efficiency of FBRwoc was relatively low （47%-65%） for both influent concentrations. However, the losses were minimal in FBRwc, which showed 75% and 92% crystal recovery for low and high phosphorus concentrations, respectively. At low calcium concentration, crystal chemical analysis showed the product to be pure struvite （〉 99%）. The scanning electron microscope and X-ray diffraction results further confirmed that the crystal recovered from FBRwc contained pure struvite, which could be considered a high quality fertilizer. Except HRT, all parameters （pH, Mg/P, N/P and Ca/Mg） were found to be influencing factors for FBRwc performance. Overall, inserting cones in each part of the reactor played a significant role in enhancing struvite recovery from a wide range of phosphorus-containing wastewater.     

Removal of phosphate from wastewater using alkaline residue

Alkaline residue(AR) was found to be an efficient adsorbent for phosphate removal from wastewater. The kinetic and equilibrium of phosphate removal were investigated to evaluate the performance of modified alkaline residue. After treatment by NaOH(AR-NaOH), removal performance was significantly improved, while removal performance was almost completely lost after treatment by HCl(AR-HCl). The kinetics of the removal process by all adsorbents was well characterized by the pseudo second-order model. The Langmuir model exhibited the best correlation for AR-HCl, while AR was effectively described by Freundlich model. Both models were well fitted to AR-NaOH. The maximum adsorption capacities calculated from Langmuir equation were in following manner: AR-NaOH AR AR-HCl. Phosphate removal by alkaline residue was pH dependent process. Mechanisms for phosphate removal mainly involved adsorption and precipitation, varied with equilibrium pH of solution. For AR-HCl, the acid equilibrium pH( 6.0) was unfavorable for the formation of Ca-P precipitate, with adsorption as the key mechanism for phosphate removal. In contrast, for AR and ARNaOH, precipitation was the dominant mechanism for phosphate removal, due to the incrase on pH( 8.0) after phosphate removal. The results of both XRD and SEM analysis confirmed CaHPO4·2H2O formation after phosphate removal by AR and AR-NaOH.     

Nitrogen mass balance in a constructed wetland treating piggery wastewater effluent

The nitrogen changes and the nitrogen mass balance in a free water surface flow constructed wetland （CW） using the four-year monitoring data from 2008 to 2012 were estimated. The CW was composed of six cells in series that include the first settling basin （Cell 1）, aeration pond （Cell 2）, deep marsh （Cell 3）, shallow marsh （Cell 4）, deep marsh （Cell 5） and final settling basin （Cell 6）. Analysis revealed that the NH4＋-N concentration decreased because of ammonification which was then followed by nitrification. The NO4＋-N and NO4＋-N were also further reduced by means of microbial activities and plant uptake during photosynthesis. The average nitrogen concentration at the influent was 37,819 kg/year and approximately 45% of that amount exited the CW in the effluent. The denitrification amounted to 34% of the net nitrogen input, whereas the accretion of sediment was only 7%. The biomass uptake of plants was able to retain only 1% of total nitrogen load. In order to improve the nutrient removal by plant uptake, plant coverage in four cells （i.e., Cells 1, 3, 4 and 5） could be increased.     

Arsenic removal from groundwater by acclimated sludge under autohydrogenotrophic conditions

Arsenic in the environment is attracting increasing attention due to its chronic health effects. Although arsenite(As(III)) is generally more mobile and more toxic than arsenate(As(V)), reducing As(V) to As(III) may still be a means for decontamination, because As(III) can be removed from solution by precipitation with sulfide or by adsorption or complexation with other metal sulfides. The performance of As(V) bio-reduction under autohydrogenotrophic conditions was investigated with batch experiments. The results showed that As(V) reduction was a biochemical process while both acclimated sludge and hydrogen were essential. Most of the reduced arsenic remained in a soluble form, although 20% was removed with no addition of sulfate, while 82% was removed when sulfate was reduced to sulfide. The results demonstrated that the reduced arsenic was re-sequestered in the precipitates, probably as arsenic sulfides. Kinetic analysis showed that pseudo first-order kinetics described the bio-reduction process better than pseudo second-order. In particular, the influences of pH and temperature on As(V) reduction by acclimated sludge under autohydrogenotrophic conditions and total soluble As removal were examined. The reduction process was highly sensitive to both pH and temperature, with the optimum ranges of pH 6.5–7.0 and 30–40°C respectively. Furthermore, Arrhenius modeling results for the temperature effect indicated that the As(V) reduction trend was systematic. Total soluble As removal was consistent with the trend of As(V) reduction.     

辽河保护区七星湿地表层水与间隙水中氮的时空分布

将大型人工湿地工程技术应用于支流河口,可以有效减轻干流污染物负荷。研究了辽河流域典型支流河口湿地的营养盐迁移转化特征。利用2012年5—7月的采样监测数据分析辽河保护区七星湿地表层水和间隙水中不同形态氮的时空分布规律。结果表明,氨氮浓度为表层水小于间隙水,而硝氮和亚硝氮浓度为表层水高于间隙水;氨氮、硝氮以及亚硝氮浓度随空间的变化趋势均体现为支流河入口处浓度较高,湿地中部及出口处浓度明显降低。水体氨氮浓度表现出随时间推移呈逐渐下降的趋势,硝氮和亚硝氮浓度呈现波动。七星湿地3个月内的氨氮总去除量为1.99 t。     

新型IC反应器在山梨醇废水处理中的工程应用

将布水装置优化后的新型内循环(IC)反应器应用于某山梨醇生产企业实际废水的二级厌氧生化处理,获得了较好的处理效果。调试阶段的结果表明:经过IC反应器的处理后,废水COD浓度由处理前的2 374~4 967 mg/L降至301~823 mg/L,COD去除率达81.4%~91.2%,COD容积负荷达8.1~13.7 kg/(m3·d);总体来说,当水力负荷增大时,COD容积负荷也相应增大;IC反应器的出水挥发性脂肪酸(VFA)基本控制在200 mg/L以下;厌氧出水再依次经过接触氧化池和絮凝沉淀池等配套工艺的处理后,COD降至80 mg/L以下,实现达标排放。     

铁碳微电解法预处理聚氯乙烯(PVC)离心母液废水

采用铁碳微电解法对聚氯乙烯(PVC)离心母液废水进行预处理。分别考察反应时间、铁粉投加量、Fe/C(质量比)、pH值及曝气速率对母液废水中的COD和聚乙烯醇(PVA)去除率的影响,并在此基础上通过正交实验确定了废水COD的最佳处理条件。结果表明,最佳处理条件为:反应时间为4 h、铁粉投加量为30 g/L、Fe/C为1:2、pH值为2、曝气速率为0.8 L/min。在该条件下,废水中COD、PVA和TOC的平均去除率分别为(67%±2)%、(98%±1)%和(55%±3)%,废水的BOD/COD值从0.3提高到0.5,可生化性得到了显著提高。同时,废水中的NH3-N、浊度也在很大程度上得到了去除,出水中总铁含量也很低。     

氯化铵处理含钒废水的研究

钒是一种非常重要的金属元素,被广泛用于钢铁与机械制造等行业以提高金属的抗拉强度。在钒的冶炼过程中,大量的含钒废水会排放出来,其中钒的含量也远超过《钒工业污染物排放标准》(GB 26452-2011)中规定的排放标准。如果不对含钒废水加以处理,不仅仅是钒资源的浪费,排入环境的钒会对生态系统造成巨大的危害。文章针对湿法提钒工艺排放的含钒废水,提出了用铵盐处理含钒废水的处理工艺。酸性含钒废水中,钒的主要形态为六聚钒酸盐的形态存在(V6O162-),当含废水为50 mL时(含钒207.7 mg/L),5 g/L的NH4Cl用量为25 mL,待反应60 min后,铵离子和六聚钒酸盐生成六聚钒酸铵(APV)沉淀,再通过离心除去沉淀物。该方法操作简单可行,废水中钒的去除率可达96%以上,可为含钒废水的后续达标处理奠定基础。     

钦州湾无机氮入海通量及其富营养化症状分析

根据对环钦州湾区域的入海河流、直排海污染源及养殖废水无机氮入海通量的估算,2011年钦州湾无机氮入海通量约为7 655 t,其中入海河流无机氮入海通量占总量的96.4%,直排海污染源次之。入海无机氮占钦州湾无机氮总量的比重为36.7%,说明钦州湾已属中等强度人为影响海域。根据对钦州湾富营养化症状——叶绿素a含量的分析,钦州湾富营养化症状不明显,钦州湾整体的富营养化程度较低。因而仅以营养盐含量评价目标海域的富营养化程度,易失之偏颇,宜结合富营养化症状来判断目标海域的富营养化程度。