Manual monitoring of algae index at 11 new sites
According to the statistics of the meteorological department, the temperature last winter and this spring has reached a record high, which is conducive to the survival of algae species in winter and maintaining high activity; however, the average temperature in May this year is higher than that of the whole year by more than 3 ℃, and the concentration of total phosphorus in the lake is at a high level, which is conducive to the rapid growth and reproduction of cyanobacteria, which brings challenges to the safety of Taihu Lake in summer.
Previously, blue-green algae were mainly monitored by buoy automatic monitoring station and artificial lake patrol. "Manual monitoring has been encrypted this year." Zhang Junyi, deputy director of ecological Laboratory of Wuxi environmental monitoring center, Jiangsu Province, introduced. This year, 11 new monitoring projects of artificial algae density and chlorophyll a were added in the lake, including 4 samples of artificial algae density in Yixing monitoring sites. The staff took samples of lake algae and water quality on site and took them back to the laboratory for further analysis. "Now there are 4 algae and 8 chlorophyll a samples in our two water sources every day, as well as the monitoring task of algae density and chlorophyll a at 7 points of the lake." Due to the rapid increase in the sample size, the laboratory has five staff members working three shifts a day since April, even 24 hours "continuous rotation" at the busiest time.
"This is the sample of Xi Dong water works at 11:00. The algae density is OK!" At noon on the 10th, a batch of water samples just taken from Taihu Lake were rushed to the ecological Laboratory for algae analysis. Zhang Junyi said that this year, both the sampling frequency and the intensity of Lake patrol have increased a lot. The sampling frequency of algae density monitoring in Xidong and Shazhu water sources has been increased from once a week in previous years to once a day and once a day in the afternoon. At present, Wuxi has established a dynamic monitoring system for Taihu Lake and drinking water source area, which covers the monitoring network of water level, water quality, cyanobacteria density and other hydrometeorological and ecological elements.
Fill in the "blank" of dynamic monitoring of cyanobacteria bloom
There is a two-story white "big football" on the top roof of the office building of the environmental monitoring center station, which can receive 8 satellite data and continuously and automatically "capture" the distribution map of cyanobacteria in Taihu Lake. It is the "remote sensing monitoring system of cyanobacteria in Wuxi City" which can provide data support for the disposal of cyanobacteria.
The system has been upgraded iteratively since it was launched in 2017. This year, in addition to receiving the data of 8 satellites directly, a new satellite has been connected through technical means, which fills the gap in the dynamic monitoring of cyanobacteria bloom in a single day. "Previously, only two times of water bloom data recorded by transit satellites could be received every day at most." Song Ting, an engineer at the center, said that now he can receive eight whole point monitoring data between 8:00 and 15:00 to monitor the dynamic changes of cyanobacteria in a day. once a large area of water bloom is detected, one-day dynamic tracing can be carried out for the cyanobacteria water bloom on that day, and the area growth and fluctuation change of cyanobacteria aggregation can be observed through data playback. As long as the area is larger than the set value, the early warning mechanism will be started.
All round "acceleration" of cyanobacteria fishing and disposal
Since the middle of May, all parts and units along the lake have been fully engaged in the salvage and disposal of cyanobacteria. Relevant salvage points, algae water separation stations, algae mud disposal and transportation units have all extended their working hours, increased their operating load and ensured timely salvage and disposal.
At 10 a.m. on the 11th, the temperature had risen to 31 ℃. Under the Yangwan cyanobacteria fishing platform, the vortex well alginate pump is rumbling. Three Salvage workers in long sleeved trousers waved long rod net bags in the hot weather to retrieve the floating debris beside the algae pump and near the platform to prevent blocking the pump port. Zhou Xiaodi, the salvage team leader of Yangwan salvage station, has been engaged in cyanobacteria salvage for 13 years. They usually start work at 6 a.m. and end work at 6 p.m. when there is a large amount of algae, they need to work until 7 or 8 p.m. or later. "There's not much cyanobacteria in the mouth of the Bay today!" Zhou Xiaodi also arranged for two algae fishing boats to go out of the Bay in turn to catch algae continuously. Recently, the daily salvage volume has reached more than 1000 tons, more than 2300 tons. once upon a time, a fisherman could only fish 150 tons of algae every day, but now with the help of mechanized fishing, aeration boats and other equipment, the fishing efficiency has been greatly improved, and the amount of algae per hour can reach 150 tons.
Algal water enters Yangwan algal water separation station through pipeline. At present, the station has two sets of equipment with different treatment processes of "one floating and one descending" to work together to ensure the efficient operation of the separation station. According to Hu Hangyu, the person in charge of the algae water separation station, the old equipment adopts the "dissolved air flotation" technology. After the algae water is pressurized, it will generate ultra-fine nano bubbles, which will be released through relevant technologies, so that the blue algae will float out of the water like wearing a life jacket, and after reaching a certain thickness, it will be scraped to the rear facilities for dehydration by the slag scraper; the new pump type pressurization technology last year will destroy the false inside of the blue algae air bag The air bubble makes it float up without adjusting the concentration of algal pulp. The operation is simpler and the treatment efficiency is higher. The daily treatment amount of algal pulp can reach up to 3900 tons.
As of June 9, 587400 tons of cyanobacteria had been salvaged in Wuxi waters of Taihu Lake, more than twice the same period last year.