Effects of sludge retention time, carbon and initial biomass concentrations on selection process: From activated sludge to polyhydroxyalkanoate accumulating cultures

Four sequence batch reactors (SBRs) fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding (ADF) mode with different configurations of sludge retention time (SRT), carbon and initial biomass concentrations to enrich polyhydroxyalkanoate (PHA) accumulating mixed microbial cultures (MMCs) from municipal activated sludge. The stability of SBRs was investigated besides the enrichment performance. The microbial community structures of the enriched MMCs were analyzed using terminal restriction fragment length polymorphism (T-RFLP). The optimum operating conditions for the enrichment process were: SRT of 5 days, carbon concentration of 2.52 g COD/L and initial biomass concentration of 3.65 g/L. The best enrichment performance in terms of both operating stability and PHA storage ability of enriched cultures (with the maximum PHA content and PHA storage yield (Y_PHA/S) of 61.26% and 0.68 mg COD/mg COD, respectively) was achieved under this condition. Effects of the SRT, carbon concentration and initial biomass concentration on the PHA accumulating MMCs selection process were discussed respectively. A new model including the segmentation of the enrichment process and the effects of SRT on each phase was proposed.     

不同粒径羟基磷灰石对污染土壤铜镉磷有效性和酶活性的影响

为研究不同粒径羟基磷灰石对重金属污染土壤的修复效果,采用向污染土壤添加常规磷灰石（150 μm）、微米（3 μm）和纳米（40 nm）羟基磷灰石的田间原位试验方法,考察其钝化修复5 a后对土壤铜镉磷有效性和酶活性的影响.结果表明:3种粒径羟基磷灰石均提高了土壤pH,降低了土壤交换性酸和交换性铝的含量,且微米羟基磷灰石处理效果最好.常规磷灰石、微米和纳米羟基磷灰石处理分别使w（离子交换态铜）降低了62.6%、74.3%和70.4%,w（离子交换态镉）降低了15.7%、25.3%和26.7%.3种材料均增加了土壤w（TP）,其中4.61%~17.4%和73.4%~89.8%分别转化为树脂磷和稳定态磷.微米羟基磷灰石处理分别使土壤脲酶活性和微生物量碳含量提高了4.66和0.66倍.研究显示,微米羟基磷灰石更有利于铜和镉由活性态向非活性态转化,增加土壤磷的有效性,提高土壤微生物活性,在我国南方重金属污染红壤区具有较好的应用潜力.      

Distribution characteristics of poly- and perfluoroalkyl substances in the Yangtze River Delta

In this work, a method was developed and optimized for the analysis of polyfluoroalkyl and/or perfluoroalkyl substances(PFASs) content in surface water and sediment samples with high instrumental response and good separation. Surface water and sediment samples were collected from the Yangtze River Delta(YRD) to analyze the distribution characteristics of perfluoroalkyl carboxylic acids(PFCAs), perfluoroalkane sulfonic acids(PFSAs), perfluoroalkyl phosphonic acids(PFPAs), perfluoroalkyl phosphinic acids(PFPiAs), and polyfluoroalkyl phosphoric acid diesters(di PAPs). The results showed that the total concentrations of PFCAs and PFSAs in YRD varied from 31 to 902 ng/L. PFCAs(≥ 11 carbons) and PFSAs(≥ 10 carbons atoms) were not detected in any surface water samples. The mean concentrations of all PFCAs and PFSAs in surface water from the sampling areas decreased in the following order:Yangtze river(191 ng/L) ≈ Taihu lake(189 ng/L) Huangpu river(122 ng/L) ≈ Qiantang river(120 ng/L) Jiaxing urban river(100 ng/L). Strong significant(p 0.05) correlations between the concentrations of many of the compounds were found in the sampling areas, suggesting a common source for these compounds. Only perfluorooctanoic acid(PFOA) was observed in all sediment samples, at concentrations varying from 0.02 to 1.35 ng/g. Finally, detection rates of two di PAPs were only 8% and 10%, respectively and the concentration of di PAPs was two to three times lower compared to PFCAs and PFSAs.     

烟草废弃物快速堆肥过程中重金属Cd形态变化特征

以烟草废弃物为原料,活性土壤为载体建立堆体,研究重金属镉的形态变化,及堆肥过程中的动态变化规律。结果表明,烟草废弃物与活性土壤混合能快速腐熟。堆肥总质量下降,重金属镉含量相对增加。重金属镉的铁锰氧化态比例增加19%,有机结合态比例在堆肥升温阶段增加,腐熟后有所下降。残渣态比例大幅度上升,增加达到5倍,且在腐熟阶段增幅最大。说明堆肥处理有利于降低重金属镉的活性。     

Increasing the application of gas engines to decrease China’s GHG emissions

This paper employs a review of the technical literature to estimate the potential decrease in greenhouse gas (GHG) emissions that could be achieved by increasing the application of gas engines in China in three sectors: urban public transport vehicle; shipping; and thermal power plants. China’s gas engine development strategies and three types of gas resource are discussed in the study, which indicates that gas engines could decrease GHG emissions by 520 megatonnes (Mt) of carbon dioxide equivalent (CO_2e) by 2020. This would account for 9.7 % of the government’s target for decreasing GHG emissions and is dominated by methane recovery from the use of coal mine gas (CMG) and landfill gas (LFG) for power generation. In the public urban transport vehicle and shipping sectors the low price of natural gas and the increasing demand for the control of harmful emissions could spur the rapid uptake of gas engine vehicles. However, the development of CMG- and LFG-fuelled power plants has been limited by the unwillingness of local enterprises to invest in high-performance gas engine generators and the associated infrastructure. Therefore, further compulsory policies that promote CMG use and LFG recovery should be implemented. Moreover, strict regulations on limiting methane leakage during the production and distribution of gas fuels are urgently needed in China to prevent leakage causing GHG emissions and largely negating the climate benefits of fuel substitution. Strategies for increasing the application of gas engines, promoting gas resources and recovering methane in China are instrumental in global GHG mitigation strategies.     

石墨烯复合材料在水处理中的应用研究

新型碳材料石墨烯,因其比表面积大,物理、化学特性优异,通常作为吸附剂或复合材料载体,用于难降解有机废水处理.载体石墨烯改性后,可优化复合材料性能,包括溶解性和可控性.基于复合材料制备,选取典型污染物废水,如染料废水、苯酚废水、农药废水,从吸附处理和催化降解两方面展开,简要介绍石墨烯复合材料的应用研究及作用效果,显示出复合材料可有效提高污染物降解效率,回用效果好.此外,石墨烯复合材料在回用及实际应用方面仍有待进一步研究.     

杭州湾表层海水营养盐分布特征及富营养化状况研究

根据2015年3月和8月杭州湾的海水质量监测数据,分析了该海域的营养盐分布特征以及富营养化状况,结果表明:杭州湾表层海水无机氮变化范围为0.36~4.22 mg/L,活性磷酸盐的含量范围为0.014~1.51 mg/L,化学需氧量含量范围为0.56~3.18 mg/L.该海域无机氮和活性磷酸盐超标严重,表层海水已处于重度富营养化状态,调查站位EI均大于1.该海域表层海水无机氮、活性磷酸盐、化学需氧量和富营养化指数高值区均与陆源入海口、养殖区、排污口等人类活动影响较大的区域有关.     

城市应急避难场所服务能力评价综述

应急避难场所对于救灾及灾后恢复都具有至关重要的作用。近年来有关应急避难场所的研究重点逐渐由场地选址转移到了空间优化配置及服务能力提升等方面。对我国城市应急避难场所的现状问题进行分析,提出从避难者的需求出发提升应急避难场所的服务水平;对城市应急避难服务能力评价的有关研究进行了整理,总结归纳了相关评价指标及评价方法。认为目前应急避难场所服务能力评价工作还有待进一步研究,应该建立合适的评价体系,为提高城市应急避难场所服务能力提供决策依据。     

黄河下游滩区开封段土壤重金属分布特征及其潜在风险评价

按照土壤采样规范,对开封段黄河滩区及滩外土壤采样,表层0～20 cm样品48个,垂直剖面采样100 cm,2个;并按照土壤化学分析方法,对Pb、Cr、Hg、As和Cd这5种重金属进行分析;最后,按照国家土壤一级标准,采用单因子污染指数、内梅罗综合污染指数和Hkanson潜在生态危害指数法对开封市黄河滩区土壤重金属分布特征、污染状况和潜在生态危害进行了分析.结果表明:①开封市黄河滩区土壤Pb、Cr、Hg、As和Cd这5种重金属含量就平均值而言,Cr的平均含量最大,Pb、Hg的平均含量最小.除Hg之外,其它重金属元素的变异系数均较小,说明重金属Hg存在较大差异;滩区土壤的主要污染元素为Hg、As、Pb,其中Pb的污染为普遍性污染.Cr和Cd在各村间变化不大,且含量均在国家一级标准(自然保护区)以下.②土壤各重金属元素的空间分布特征研究区内上下段之间分异明显,上段呈清洁状态,中段有少量污染,下段表现出明显富集的分布状态;③以黄河大堤为界,滩区内外重金属分异与居民点分布密切相关,在滩区上段(西南部)居民集中,土壤各重金属浓度较高,表现为沿河区<大堤外,中下游段(滩区东北部)重金属含量大于大堤外土地,下游段东北趋向于污染富集.④以重金属平均单项潜在生态风险指数(Eri)评价表明,开封市黄河滩区土壤Hg的潜在生态风险达到强烈水平,Pb在重金属综合潜在生态风险的贡献率高达50.5%,是最主要的生态风险重金属,各个重金属的污染程度为Hg>Pb>As>Cd>Cr.⑤各重金属生态危害的次序为Hg>Cd>As>Pb>Cr.由RI值对应的潜在生态风险等级可知,开封市黄河滩区土壤存在中等级别重金属潜在生态危害.     

聚磷污泥去除高浓度铅的影响因素研究

利用聚磷活性污泥去除废水中的铅[ρ(Pb2+)=150.0 mg·L-1],研究了反应体系内不同溶解氧状况和初始pH值对污泥除铅的效率和稳定性的影响.结果表明,厌氧条件下,pH 6时,铅的去除率随时间增长呈上升趋势,32 d后铅去除率达99.8%,其中有机物及硫化物结合态铅、残渣态分别占41.8%和52.6%,污泥中铅的稳定性良好.好氧条件下,在相对较短时间内铅的去除率随pH上升而增加,反应2 h时,pH 6、pH 4和pH 2对应的铅的去除率分别为99.9%、96.9%和30.3%;而好氧32 d后pH 6、pH 4和pH 2的污泥中残渣态铅含量分别为3 072.3、4 726.8和2 359.1 mg·kg-1,分别占污泥中总铅的41.8%、65.8%和88.8%.综合考虑除铅率和除铅后污泥稳定性,好氧且pH 4理论上是聚磷污泥除铅的最佳条件.