Dioxin formation in pulp and paper mills of India

Samples of effluents, sludge, pulp, final products (paper) and soil were collected from the identified pulp and paper mills in India. The samples were analysed for 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2,3,7,8-TCDD) and other dioxin congeners and precursors. Pulp and paper mills using chlorine for the bleaching process showed the presence of 2,3,7,8-TCDD in effluent samples. In the effluent and pulp samples from mills where chlorine dioxide was used as a bleaching agent, the 2,3,7,8-TCDD congener ranged from below the detection limit 0.05 to 0.12 ngL⁻¹/ngg⁻¹. The relative standard deviation of reproducibility and the percent recovery of 2,3,7,8-TCDD were 2.07 and 82.4% in pulp and 2.8 and 92% in effluent, respectively. The 1,3,6,8-TCDD was the only other major dioxin congener found in the treated and untreated effluent and sludge samples. However, dichlorobenzene, trichlorophenyl, and hexachlorobiphenyl were detected in all samples. The formation of dioxins can be minimised by replacing chlorine with chlorine dioxide in bleaching processes in pulp and paper mills.     

微波萃取技术在分析土壤中有机污染物的应用

介绍了微波萃取技术及其使用的试剂、设备和条件,对微波萃取在分析土壤中有机污染物的应用予以综述,阐述了微波萃取技术是分析土壤中有机污染物的好方法。     

Formation of aerobic granules in the presence of a synthetic chelating agent

This paper examines the development of aerobic granular sludge in the presence of a synthetic chelating agent, nitrilotriacetic acid (NTA), in sequencing batch reactors (SBR). The growth of seed sludge at 0.26 mM, 0.52 mM and 1.05 mM of NTA was found to be significantly lower as compared to that in the absence of NTA. Aerobic granulation was significantly enhanced in the three SBRs (R2, R3 and R4), which were fed with 0.26 mM, 0.52 mM and 1.05 mM of NTA as a co-substrate, in comparison to the acetate-alone fed SBR (R1). After 2 months of operation, the mean diameter of the biomass stabilized at 0.35 mm in R1 (acetate alone), as compared to 2.18 mm in R4 (1.05 mM NTA+acetate). NTA degradation was established in SBRs, with almost complete removal during the SBR cycle. Batch experiments also showed efficient degradation of NTA by the aerobic granules.     

Degradation and plant uptake of nonylphenol (NP) and nonylphenol-12-ethoxylate (NP12EO) in four contrasting agricultural soils

Nonylphenol polyethoxylates (NPEOs) are surfactants found ubiquitously in the environment due to widespread industrial and domestic use. Biodegradation of NPEOs produces nonylphenol (NP), an endocrine disruptor. Sewage sludge application introduces NPEOs and NP into soils, potentially leading to accumulation in soils and crops. We examined degradation of NP and nonylphenol-12-ethoxylate (NP12EO) in four soils. NP12EO degraded rapidly (initial half time 0.3-5 days). Concentrations became undetectable within 70-90 days, with a small increase in NP concentrations after 30 days. NP initially degraded quickly (mean half time 11.5 days), but in three soils a recalcitrant fraction of 26-35% remained: the non-degrading fraction may consist of branched isomers, resistant to biodegradation. Uptake of NP by bean plants was also examined. Mean bioconcentration factors for shoots and seeds were 0.71 and 0.58, respectively. Removal of NP from the soil by plant uptake was negligible (0.01-0.02% of initial NP). Root concentrations were substantially higher than shoot and seed concentrations.     

污泥加热预处理对中温厌氧消化的影响

对污泥加热预处理给中温厌氧混合消化和污泥单独消化带来的影响进行了研究.研究结果表明,污泥加热预处理有利于提高混合消化对 COD 的去除率,尤其是 SCOD 的去除率由 77%增长到 93%,但不利于 TS 和 VS 的去除;而对污泥单独消化,预处理则不利于有机物的去除.采用加热预处理后的污泥进样,混合消化和污泥单独消化的甲烷产气量均有所提高.     

硝化污泥低温冲击强化试验

采用完全好氧式膜生物反应器富集耐低温硝化污泥,通过低温冲击强化试验研究硝化污泥的耐低温特性.结果表明,低温对硝化污泥中微生物的群落多样性影响较大,温度越低,微生物多样性越低.低温强化组投加了耐低温高硝化菌含量硝化污泥,使得硝化菌在反应器内生长趋势良好,对低温冲击的恢复更有效果,且低温硝化污泥比中温硝化污泥具有更好的氨氮...     

pH和元素摩尔比对污泥酸化液沉淀法脱氮除磷的影响

针对剩余污泥水解酸化产生大量多糖、蛋白质和VFAs碳源的同时会有较高浓度的NH+4-N和PO3-4-P溶出的问题,考察了pH值和元素摩尔比对以沉淀法同时去除NH+4-N和PO3-4-P的影响.结果表明,最佳pH为9.0,当pH升高到10.0时NH+4-N去除率略有下降,在特定摩尔比范围内摩尔比对沉淀形成的影响大于pH值...     

污泥好氧颗粒化过程中氨氧化菌群结构的演替与分析

为了揭示颗粒污泥形成过程中氨氧化菌(AOB)群落结构的演替规律,利用变性梯度凝胶电泳(DGGE)、克隆测序和实时定量聚合酶链式反应(real-time PCR)等分子生物学技术对AOB群落的演替进行了研究。DGGE结果表明,污泥接种驯化期,AOB群结构的变化较为剧烈,在外加选择压的作用下,种群多样性迅速下降;但随着污泥颗粒化的完成而趋于稳定。测序结果表明,接种污泥中的大多数亚硝化单胞菌属因可快速适应工艺的淘洗过程而被保留在系统内,而亚硝化螺菌属逐渐被淘汰。real-time PCR结果表明,在经历了运行初期的淘洗后,AOB含量随着污泥浓度的提高而逐渐增长;但污泥的氨氧化活性随着污泥浓度的增长而降低。     

混合接种PN与PN/A颗粒污泥快速启动连续流自养生物脱氮反应器

在连续流条件下,快速培养亚硝化-厌氧氨氧化（PN/A）颗粒污泥是实现污水高效生物脱氮处理的关键技术. 与PN/A污泥相比,亚硝化（PN）颗粒污泥具有生长周期短、易于批量化培养的优点,并可作为富集厌氧氨氧化菌（AMX）的载体. 在3个完全混合流反应器（R1~R3）中,分别按照质量比3∶1、1∶1和1∶3混合接种PN/A和PN颗粒污泥,并通过设置高氨氮负荷、短水力停留时间和强水力剪切条件,成功启动了连续流自养生物脱氮工艺. 结果表明,尽管R3的启动时长较R1和R2更长,但污泥接种比并未显著影响连续流反应器在稳定状态下的脱氮性能,总氮去除负荷均可达到2.6 kg·（m³·d）^-1以上. 接种的PN颗粒污泥通过提供好氧氨氧化菌种（AOB）,为AMX生长供给了充足的亚硝态氮基质,充分发挥了培养PN/A颗粒污泥的前驱体作用. 由高通量测序结果可知,R1~R3中成熟颗粒的微生物丰度和多样性指数均明显高于接种污泥. AOB（Nitrosomonas属）和AMX（Candidatus Kuenenia和Brocadia属）与Chloroflexi、Bacteroidetes和Chlorobi等异养菌门是驱动自养生物脱氮和维持颗粒结构稳定的关键菌群. 总之,PN与PN/A颗粒污泥的混合接种是快速启动连续流自养脱氮工艺的可行策略,对工程应用具有指导意义.