Investigating the coagulation of non-proteinaceous algal organic matter: Optimizing coagulation performance and identification of removal mechanisms

The removal of algal organic matter(AOM) is a growing concern for the water treatment industry worldwide. The current study investigates coagulation of non-proteinaceous AOM(AOM after protein separation), which has been minimally explored compared with proteinaceous fractions. Jar tests with either aluminum sulphate(alum) or polyaluminium chloride(PACl) were performed at doses of 0.2–3.0 mg Al per 1 mg of dissolved organic carbon in the p H range 3.0–10.5. Additionally, non-proteinaceous matter was characterized in terms of charge, molecular weight and carbohydrate content to assess the treatability of its different fractions. Results showed that only up to 25% of non-proteinaceous AOM can be removed by coagulation under optimized conditions. The optimal coagulation p H(6.6–8.0 for alum and 7.5–9.0 for PACl) and low surface charge of the removed fraction indicated that the prevailing coagulation mechanism was adsorption of non-proteinaceous matter onto aluminum hydroxide precipitates. The lowest residual Al concentrations were achieved in very narrow p H ranges, especially in the case of PACl. High-molecular weight saccharidelike organics were amenable to coagulation compared to low-molecular weight( 3 k Da)substances. Their high content in non-proteinaceous matter(about 67%) was the reason for its low removal. Comparison with our previous studies implies that proteinaceous and nonproteinaceous matter is coagulated under different conditions due to the employment of diverse coagulation mechanisms. The study suggests that further research should focus on the removal of low-molecular weight AOM, reluctant to coagulate, with other treatment processes to minimize its detrimental effect on water safety.     

Simultaneous elimination of cyanotoxins and PCBs via mechanical collection of cyanobacterial blooms: An application of “green-bioadsorption concept”

In this study, the distribution, transfer and fate of both polychlorinated biphenyls (PCBs) and cyanotoxins via phytoplankton routes were systematically investigated in two Chinese lakes. Results indicated that PCB adsorption/bioaccumulation dynamics has significantly positive correlations with the biomass of green alga and diatoms. Total lipid content of phytoplankton is the major factor that influences PCB adsorption/bioaccumulation. Cyanobacterial blooms with relatively lower lipid content could also absorb high amount of PCBs due to their high cell density in the water columns, and this process was proposed as major route for the transfer of PCBs in Chinese eutrophic freshwater. According to these findings, a novel route on fates of PCBs via phytoplankton and a green bioadsorption concept were proposed and confirmed. In the practice of mechanical collections of bloom biomass from Lake Taihu, cyanotoxin/cyanobacteria and PCBs were found to be removed simultaneously very efficiently followed this theory.     

水利工程背景下河流水华暴发成因分析及模拟研究

研究发现,河流水华暴发的主要驱动因素除受过量营养盐摄入、气候变化导致的气温上升和降雨等限制外,水文情势的影响尤为显著.在高强度人类活动影响下,水利工程开发导致的水文情势改变是否为河流水华加剧的成因之一,是水与环境学科交叉研究亟待探索的一个重要应用基础问题.通过对近10年来国内外在水利工程背景下河流水华暴发成因研究进展的综述,辨识了河流水华发生的"水循环-水环境-水生态"相互作用关系;对考虑水文变化的河流水华预测统计学模型、智能算法和水质水量耦合机理模型等进行了回顾和总结,并提出了基于水循环物理过程联系的生物及生物地球化学过程、社会经济用水与管理人文过程等与河流水华发生相互作用与反馈的水系统论研究体系.当前我国水利工程调水影响区下的河流水华问题研究仍面临着一些难点和挑战:① 过去关于水利工程调水对河流中下游水生态的影响研究多数是基于情景假设和规划条件下的预断,随着近年来我国多个大型水利工程的正式实施运行,当前以实际工程调水为背景（如南水北调、引江济汉工程等）开展水华模拟的研究成果仍然十分有限;② 水利工程调水影响区下的河流水华发生机理尚不明确,当前多数藻类生长模型并没有将流域水循环过程影响纳入考虑因素,对河流生态水文过程作用机理与耦合及定量关系分析方面的研究相对匮乏;③ 现阶段水利工程背景下的河流水华问题研究多停留在定性分析和宏观定量阶段,缺乏基于以水系统理论为导向的水生态系统与河流水文情势共同作用机制的定量化研究.      

湖泊水面温度遥感定量反演研究综述

湖泊水面温度与藻类生长密切相关,通过获取水体表层温度信息来监测湖泊水面温度时空动态变化,对于蓝藻水华预警监控具有重要意义。湖泊水面温度遥感定量反演的理论方法与反演地表、海洋表面温度基本相同。本文在介绍遥感反演地表温度原理的基础上,总结了国内外基于热红外波段反演水体表面温度的单窗算法、劈窗算法、多通道算法等几种常用方法,重点分析了各算法的优缺点和反演的主要难点,并对今后在内陆水体藻华预测顸警等方面的应用趋势进行了展望。     

水库热分层期藻类水华与温跃层厌氧成因分析

以西安市李家河水库为研究对象,通过对水体理化因子和浮游植物的连续监测,对热分层期藻类垂向分布与温跃层厌氧成因进行了初步分析.结果表明:①6～9月,李家河水库水体稳定指数为2～10 m~(-1),处于稳定热分层状态,水体溶解氧呈明显的垂向以及季节差异,p H、电导率均与溶解氧呈现相同的分层结构;②李家河水体的富营养状态诱导夏季藻类水华暴发;藻细胞密度垂向差异大,集中悬停于水深0～5 m区域内,最高为2. 95×10~8cells·L~(-1),叶绿素a含量最大为46. 42mg·m~(-3);高密度藻类在温跃层内堆积分解,水深5～24 m内出现较大面积的厌氧区,pH下降、电导率和高锰酸盐指数升高;③高密度藻类分解耗氧是夏季分层期温跃层厌氧形成的主要原因.     

Ecological Study of Spring-Early Summer Phytoplankton Blooms in A Semi-Enclosed Estuary

A sampling station in the Eastern Harbour of Alexandria was operated for 51 days between 2 March and 12 June, 1991. the harbour had different wide physical and chemical variations. Six distinct phytoplankton blooms occurred during this period. It is concluded that the physicochemical conditions affected the phytoplankton community structure and species composition. A dense diatom bloom could be maintained in a very weak and/or stabilized water column. A diatom bloom does not necessarily accompany an enhanced nutrient period. the depletion of nutrients and establishment of thermal stratification probably created favourable conditions for dinoflagellate and flagellate species to achieve blooms. the species composition could be shifted over the short term and a dense phytoplankton bloom could possibly dissipate in a few days.     

四斗朱水库蓝藻水华爆发成因分析及治理对策研究

作为饮用水源的小型水库四斗朱连续几年在早春即开始爆发严重束丝藻水华（属于蓝藻）。水质分析发现,四斗朱水库的水质参数如总氮（TN）、总磷（TP）、氨氮（NH4^＋-N）以及BOD和COD浓度并不高,但明显高于其上游的石门塘水库,这说明在四斗朱水库的集水区存在污染源。本文分析了在低营养盐浓度情况下四斗朱水库蓝藻水华爆发的原因,认为由于集水区内的农业、生活、水土淋失以及自然沉降等途径导致水库营养浓度升高。并由于未知营养、气温回升以及水库生态系统失衡等因素,导致蓝藻水华暴发。最后,提出了相应的综合治理对策。     

Three-dimensional eutrophication model and application to Taihu Lake, China

Taihu Lake, the largest freshwater shallow lake in eastern China, has suffered from severe eutrophication over the past two decades. This research developed a three-dimensional eutrophication model to investigate the eutrophication dynamics. The model fully coupled the biological processes and hydrodynamics, and also took into account the effects of sediment release and the external loads from the tributaries. After sensitivity analyses, the key parameters were defined and then calibrated by the field observation data. The calibrated model was applied to study the seasonal primary productions and its regional differences. The comparisons between model results and field data in year 2000 indicated that the model is able to simulate the eutrophication dynamics in Taihu Lake with a reasonable accuracy. From the simulation experiments, it was found that the meteorological forcing have significant influences on the temporal variations of the eutrophication dynamics. The wind-induced circulation and sediment distribution play an important role in the spatial distribution of the algae blooms.     

三峡水库支流大宁河水华特征研究

以三峡水库支流大宁河水华敏感期(2007年4~6月和2008年4~5月)水质和水华的调查数据为依据,研究了其水质变化、营养盐构成及水华特征.结果表明,水华敏感期大宁河自回水段以下氮磷含量较高,总氮范围为0.84~3.21 mg/L,总磷为0.011~0.531 mg/L,氮营养盐主要以TDN为主(TDN/TN为84%),而磷营养盐以TDP占优(TDP/TP为60%);N/P值均高于16,藻类生长受磷限制.高锰酸盐指数和溶解氧含量低且变化稳定.叶绿素a为1.41~219.04 mg.m-3.相关性分析表明Chl-a与TP、高锰酸盐指数、DO、pH呈显著正相关(rChla-TP=0.453、rChla-高锰酸盐指数=0.641、rChla-DO=0.584、rChla-pH=0.409,p0.01),与SD呈显著负相关(rChla-SD=-0.392,p0.01);pH受多参数影响,但受藻类生长影响较大.通过显微镜对藻类进行鉴定,发现大宁河自回水段以下水华敏感期藻类分布较广,共发现8门82属124种,其中硅藻门和绿藻门分布最多,其次为蓝藻门和甲藻门,其余藻种较少.大宁河在水华敏感期暴发了3次自回水段以下大规模水华,水华期间藻密度最高值是正常值的14~1427倍,水华优势种主要有绿藻门的波吉卵囊藻、小空星球藻、土生绿球藻、实球藻和小球藻;裸藻门的扁裸藻、矩圆囊裸藻;硅藻门的小环藻、冠盘藻和舟形藻;甲藻门的埃尔多甲藻等;发生多藻种同时水华的情况;出河口处藻类较少.     

水生植物提取液对蓝藻的抑制作用

采用对照试验,模拟研究不同氮磷营养、水温等条件下,添加水生植物（睡莲）提取液对蓝藻生长的抑制作用。实验证实了植物提取液对蓝藻有抑制作用,在不同生长条件下,细胞密度为6×10^7～2×10^10个／L时,可达到降低蓝藻50％的生长率。