湖库型饮用水源蓝藻水华应急处置模拟实验

水源水体富营养化及造成的藻类水华是淡水生态系统面临的主要问题之一，严重威胁城市供水。以华南地区赤水水库为例，基于2019年5月暴发的蓝藻水华事件，开展了水库水质、蓝藻密度的监测分析及壳聚糖改性高岭土复合聚合氯化铝的应急除藻技术研究，确定了絮凝剂的最佳投加量并评估了除藻效果。结果表明: 水华暴发时取水口表层TN、TP浓度超过地表水III标准且水体主要限制性元素为磷，若集水区内磷的浓度继续增大，则水华暴发的频率继续增加；此次蓝藻水华的优势种为铜绿微囊藻，且垂向主要聚集在表层及水下5 m处，随水深的增加藻细胞密度逐渐降低，表层藻细胞密度高达6.87×10⁸ cells·L⁻¹；采用壳聚糖改性高岭土复合聚合氯化铝去除蓝藻效果较好，在改性黏土投加100 mg·L⁻¹，聚合氯化铝投加10 mg·L⁻¹时，1 h去除率约60%，且随着时间延长，去除率持续提高。改性黏土复合聚合氯化铝能在短期内使藻类沉降至水库底部，可应用于湖库型饮用水源蓝藻水华的应急处置。

Simulation study on emergency treatment of cyanobacterial bloom in drinking water reservoir

One of the major problems in freshwater ecosystem that threaten urban water supply is eutrophication and algal blooms that caused by it. In this paper, cyanobacterial bloom happened in May 2019 in Chishui reservoir, a drinking water reservoir in south China, was taken as a typical case to study variation of water quality and cyanobacterial cell density, as well as the emergency treatment technology. During this cyanobacterial bloom case, an in-field experiment of emergency treatment by adding chitosan-modified-kaolin and polyaluminum chloride (PAC) was carried on to assess the treatment efficiency and the optimal dosage. Results showed that total nitrogen (TN) and total phosphorus (TP) concentrations in the surface layer exceeded level III of the national water quality standard, and eutrophication in the reservoir was controlled by phosphorus concentration. If the phosphorus concentration kept increasing, so as the frequency of cyanobacterial bloom. Microcystis aeruginosa was found to be the dominant species in this case, and the M. aeruginosa cells were mainly distributed within 5m below the water surface. The cell density in the surface was highest and reached 6.87×108 cells·L−1 and it decreased with increase in water depth. The efficiency of chlorophyll a removal by adding chitosan-modified-kaolin and PAC was satisfactory. The removal rate was up to 60% after adding 100 mg·L−1 chitosan-modified-kaolin and 10 mg·L−1 PAC in one hour, which increased with the extension of time afterwards. Algal cells can be precipitated into the bottom area of the reservoir in a short period of time by addition of chitosan-modified-kaolin and PAC. As such, this technology is suitable for emergency treatment of cyanobacterial bloom in drinking water reservoir.