A comparative study of abiological granular sludge (ABGS) formation in different processes for zinc removal from wastewater

Abiological granular sludge (ABGS) formation is a potential and facile strategy for improving sludge settling performance during zinc removal from wastewater using chemical precipitation. In this study, the effect of pH, seed dosage, and flocculant dosage on ABGS formation and treated water quality was investigated. Results show that settling velocity of ABGS can reach up to 4.00 cm/s under optimal conditions, e.g., pH of 9.0, zinc oxide (ZnO) seeds dosage of 1.5 g/l, and polyacrylamide (PAM) dosage of 10 mg/l. More importantly, ABGS formation mechanism was investigated in NaOH precipitation process and compared with that in bio-polymer ferric sulfate (BPFS)–NaOH precipitation process regarding their sludge structure and composition. In the NaOH precipitation process, ABGS formation depends on some attractions between particles, such as van der Waals attraction and bridging attraction. However, during the BPFS–NaOH sludge formation process, steric repulsion becomes dominant due to the adsorption of BPFS on ZnO seeds. This repulsion further causes extremely loose structure and poor settling performance of BPFS–NaOH sludge.     

固定化小球藻与活性污泥的共生系统处理含锌废水

研究固定化小球藻与活性污泥的共生系统对含锌废水中Zn2+的去除效果,分析菌藻状态、初始Zn2+浓度、pH、固定化菌藻小球投加量和菌藻体积比等5个因素对固定化菌藻共生系统去除Zn2+的影响。结果表明,固定化活性污泥、固定化小球藻和固定化菌藻对Zn2+的去除效果均优于悬浮小球藻,其中固定化菌藻对Zn2+的去除效果最好;废水中初始Zn2+浓度小于100 mg/L时,固定化菌藻系统对废水中Zn2+的去除率达到90.5%;固定化菌藻系统去除废水中Zn2+的最佳条件是:初始Zn2+浓度为80 mg/L,pH=7,固定化小球投加量为80 mL,菌藻体积比为1∶2。     

Effects of aging and sediment composition on hexachlorobenzene desorption resistance compared to oral bioavailability in rats

Studies were conducted to assess the effects of black carbon, clay type and aging (1-1.5yr) on desorption and bioavailability of hexachlorobenzene (HCB) in spiked artificial sediments. Tenax (a super sorbent)-mediated desorption was used to examine the effects of these parameters on the physicochemical availability of HCB. The Tenax-mediated desorption of HCB from the four aged artificial sediments exhibited biphasic kinetics. The fast desorbing fractions ranged from 64.8% to 22.3%, showing reductions of 4.0-18.9% compared with freshly-spiked sediments. Statistical analysis on the fast desorbing fractions showed that all three treatment effects (i.e., montmorillonite clay, black carbon content, and aging) were significant. Two sediments with higher black carbon content exhibited much greater aging effects (i.e., greater reduction in fast desorbing fraction) than the other two sediments without the addition of black carbon. For both freshly-spiked and aged sediments, the desorption resistant sediment-bound HCB (i.e., slow desorbing fraction) correlated reasonably well to previously reported rat fecal elimination of HCB, which is a measure of the non-bioavailable fraction of sediment-bound HCB. A similar correlation was also observed between fast desorbing fraction and previously reported accumulation of HCB in the rat body (carcass+skin). These observations suggest that physicochemical availability, as defined by the desorption of HCB from sediments, provides a reasonable prediction of the oral bioavailability of sediment-bound HCB to rats. These results showed that montmorillonite clay, black carbon and aging reduced physicochemical availability and ultimately bioavailability of sediment-bound HCB.     

碳酸钙和粉煤灰对铅胁迫下小麦毒害的缓解效应

采用室内盆栽和网室盆栽的方法,研究了碳酸钙和粉煤灰对铅污染土壤的小麦幼苗生物效应、成熟期籽粒含铅量和蛋白质含量及生物产量的影响,探讨了碳酸钙和粉煤灰缓解铅毒害小麦的生理机制.结果表明,在轻度铅污染(铅为350 mg/kg)的小麦农田,1.0 g/kg碳酸钙或50 g/kg粉煤灰对小麦生长有明显的促进作用.能有效缓解铅对小麦的毒害;在重度铅污染(铅为600mg/kg)的小麦农田,1.0～2.0 g/kg碳酸钙或50～100 g/kg粉煤灰对小麦铅毒害缓解效果较好.     

绿色建筑小区雨水资源化综合利用技术

运用生态学原理设计绿色建筑小区已逐渐成为潮流,节水与水资源利用的问题正日益受到关注.绿色建筑小区雨水资源化综合利用技术集成优化了小区雨水收集与分散处理系统、雨水集中收集与处理系统、雨水渗透系统等技术,具有投资省、处理效果好、管理方便等优点,适合为今后的绿色建筑小区雨水资源化综合利用建设参考.     

饮水型砷中毒病区人群砷暴露量及尿砷的季节变化

地下水高砷暴露的健康危害是环境与健康领域面临的巨大挑战。水砷含量及暴露人群饮水量参数的季节性变化可能影响饮水砷暴露评估的准确性。本研究选择内蒙古饮水砷中毒病区为研究区,测定丰水期(2013年5月)和枯水期(2013年12月)居民饮用水和尿液各形态砷(三价无机砷iAs~(3+)、五价无机砷iAs~(5+)、一甲基砷MMA~(5+)和二甲基砷DMA~(5+)+)含量,研究砷暴露量和尿砷的季节变化。结果表明,丰水期水砷含量(134.4±25.8)μg·L~(-1)显著低于枯水期的(163.2±38.1)μg·L~(-1),且丰水期水中iAs~(3+)的含量(58.9±51.2)μg·L~(-1)也显著低于枯水期的(100.1±49.0)μg·L~(-1)。研究人群丰水期通过饮水的摄砷量为313.1μg·d~(-1),低于枯水期的378.6μg·d~(-1)。此外,丰水期居民尿液总砷含量(218.6μg·L~(-1))显著低于枯水期(283.1μg·L~(-1))。丰水期女性居民尿液iAs、MMA~(5+)和总砷含量随当季饮水iAs~(5+)含量的升高而显著降低,枯水期女性尿液MMA5+含量随当季饮水iAs~(3+)及iAs含量的升高而显著升高。可见,病区居民饮水砷暴露量与尿砷含量具有明显的季节差异性,饮水砷与尿砷的关系受饮水砷形态、季节变化及性别等因素影响。     

《国家危险废物名录》在危险废物管理中的存在的问题

本文介绍了我国危险废物名录目前的现状,分析了危险废物名录在危险废物监管中存在的问题,对危险废物的监管提出了建设鉴定机构、严格鉴定程序、豁免制度等建议。     

全国土壤污染状况调查样品采集质量保证

土壤污染危害巨大,它直接关系到人体健康、生态安全和农业可持续发展。目前中国土壤污染状况形势严峻,对全国各地土壤污染状况进行调查是一件意义重大而且势在必行的事情。土壤样品采集是土壤污染状况调查工作的重要组成部分,所采集的样品的代表性直接关系到调查工作的成效。质量保证对数据的准确性、精密性、可靠性和代表性有着十分重要的意义,因此土壤样品采集过程中应严格按照质量保证程序进行全过程质量控制。     

Effects of Modified Starch and Different Molecular Weight Polyvinyl Alcohols on Biodegradable Characteristics of Polyvinyl Alcohol/Starch Blends

The common biodegradable properties of polymer make them an excellent pair for blending, and the water solubility of polyvinyl alcohol (PVA) makes it easy to mix evenly with the starch. In this study, PVAs with different molecular weights were blended with various compositions of cross-linked starch (CLS) to explore the effects of molecular weight of PVA on the biodegradable characteristics of the PVA/starch blends. Comparing the biodegradability of all the various PVA/starch blends, a PVA was singled out from the PVA/starch blends of higher biodegradability. Further, the chosen PVA was then blended with the acid-modified starch (AMS) to systematically investigate the effects of the modified processing of starch on the biodegradable characteristics of the PVA/starch blends. Differential scanning calorimetry (DSC) analysis of PVA and PVA/starch specimens reveal that the T_m values of PVA/starch specimens reduce gradually as their CLS or AMS contents increase. After the CLS is blended in PVAs of different molecular weights, the tensile strength (??_f) and elongation at break (??_f) values of (P₁₀₀S₀)G₂₀M₁ specimen increase and simultaneously reduce, respectively, as their molecular weights of PVA increase from about 80,000 (PVA_BF-17) to 120,000 (PVA_BF-26). The ??_f and ??_f values of the PVA/modified-starch blends decrease with an increase in the modified starch contents. The ??_f values of the PVA/AMS specimens decrease with an increase in the concentrations of hydrochloric acid. Comparing the ??_f values of the PVA/CLS specimens with those of the PVA/AMS specimens, the ??_f values of the PVA/CLS specimens are better than those of the PVA/AMS specimens. On the contrary, the ??_f values of the PVA/AMS specimens are better than those of the PVA/CLS specimens. According to the biodegradability of all the PVA/starch blends, PVA with higher molecular weights displays higher biodegradability. The biodegradability of the PVA/modified-starch blends increase as the modified starch contents of the PVA/modified-starch blends increase. As evidenced by the results of the biodegradability test, the biodegradability of the PVA/modified-starch blends, therein PVA is blended with 1N AMS, shows better biodegradability. The result of bio-reaction kinetics experiment can evaluate the decomposition tendency of the PVA/starch blends up to any biodegradable rate under ambient environment. Using the kinetic model of the first order reaction, it is estimated that 16.20?years and 12.47?years will be needed for the PVA_BF-17/starch blends, containing 20 and 40% of CLS respectively, to be degraded up to 70% under ambient environment. In addition, it is 1.68?years for the PVA_BF-26 blends with the 40% 2N AMS under decomposition environment while it is 1.94?years for the 40% 1N AMS. Overall, the decomposition potential of PVA/AMS specimens is better than PVA/CLS specimens. Furthermore, the 1N(26P₆₀AS₄₀)₁₀₀G₂₀M₁ specimen is coincidence the biodegradable material criteria of Environmental Protection Administration (EPA) of Taiwan.