Do you know that?/You know what? Do you know that?/You know what? In the vast blue ocean, there is a tiny creature that people can't see with naked eyes, but under the microscope, we can clearly see their strange shapes: some are like balls, some are like hearts, some are like full moons, some are like silver spindles, some are like crescent moons, and some are triangles. Although their own sports ability is very weak, their special body shape can adapt to floating life well, and they can float or suspend on the bright sea.
Similar to trees, crops and weeds on land, these creatures have chlorophyll, which can carry out photosynthesis, synthesize carbon dioxide, nitrogen, phosphorus and other nutrients in seawater into organic substances they need, and release oxygen into the atmosphere at the same time. Most of them are unicellular organisms, so people call them unicellular algae. Because algae are tiny (generally only a few thousandths of a millimeter), people also call them microalgae. Taxonomically, researchers often classify some cyanobacteria plants with centrosomes (such as spirulina) as microalgae.
At present, there are about 1800 species of marine microalgae recorded in China Sea. Because different kinds of microalgae contain different pigment components (chlorophyll, carotenoid, phycobiliprotein, etc. ) and their proportion, showing colorful colors: green algae is grass green because of its rich chlorophyll a and chlorophyll b; Cyanobacteria are blue-green because they contain more chlorophyll "phycocyanin"; Red algae mainly contain phycoerythrin, which is red or rose red; Diatoms and Chrysophytes are yellow, brown, golden brown or yellowish brown because they contain more lutein.
The great use of microalgae
Studies since 1950s have proved that microalgae is the main primary producer in the ocean and the foundation of the marine food chain, which drives the energy flow and material flow of the whole marine ecosystem and directly and indirectly feeds hundreds of millions of marine animals, so it plays a very important role in the material cycle of the marine ecosystem. Once marine microalgae are destroyed, it will endanger other marine life and the whole marine ecosystem.
Microalgae also plays a very important role in the production and life of human society. At present, the development and utilization of marine microalgae mainly focus on the following aspects, and some uses have reached the level of industrial production, such as: as nutritious food and healthy food for human beings; As a renewable bioenergy, biomass fuel can be obtained by pyrolysis, and water can be decomposed into hydrogen and oxygen through photosynthesis and its unique hydrogenase system. Extract chemical products such as pigment, medicine and glycerin; As bait for aquatic animals and additive for livestock feed.
However, the uses of microalgae are far more than these. Eliminating pollutants into the sea and cleaning the marine environment are their new uses that have attracted much attention in recent years. Purification of mariculture wastewater
In today's intensive mariculture, wastewater discharge is an important cause of seawater pollution. In the process of industrial culture and seedling raising of fish, shrimp, shellfish and crabs, only about 20% of dry and wet feed is eaten by cultured animals, and the excess feed diffuses and accumulates in the cultured water, resulting in an increase in nitrogen and phosphorus content in the water. At the same time, the metabolism of cultured animals will also cause the concentration of ammonia nitrogen and organic nitrogen in water to increase. Once this kind of wastewater is discharged into the coastal waters, the seawater will become eutrophic or produce red tide due to the increase of inorganic nitrogen and phosphorus concentration, which seriously threatens the growth of marine life. Therefore, aquaculture wastewater must be effectively treated before it can be discharged. Microalgae can effectively purify aquaculture wastewater.
During the growth of microalgae, various forms of inorganic nitrogen and organic nitrogen can be utilized by microalgae, while phosphorus is mainly absorbed by microalgae in the form of potassium dihydrogen phosphate and potassium dihydrogen phosphate. When microalgae are introduced into aquaculture wastewater, algae cells provide oxygen to the water through photosynthesis, which increases the dissolved oxygen in the water, so that aerobic bacteria can continuously decompose organic matter, and then produce carbon dioxide as the carbon source for photosynthesis of algae cells. Therefore, in the process of purifying water quality, people often combine microalgae with bacteria, which is what we usually call "algae bacteria". At the same time, microalgae absorb and utilize nutrients such as nitrogen and phosphorus to synthesize complex organic matter. This is the mechanism of microalgae purifying aquaculture wastewater.
The characteristics of microalgae, such as high utilization efficiency of light energy, rapid growth and reproduction, and high yield, determine its rapid absorption and accumulation of nutrients. The concentration of pollutants in aquaculture wastewater is much lower than that of industrial wastewater and domestic sewage, so as long as suitable growth conditions (light, temperature, pH value, etc. ) can quickly improve the quality of wastewater.
Researchers at China Ocean University identified a green algae, Platymonas subcordiformis.
Platymonas subcordiformis was introduced into the optical membrane combined bioreactor to remove nitrogen and phosphorus nutrients from Penaeus vannamei wastewater. Through the good separation and interception performance of ultrafiltration membrane module, the reactor can maintain a high microalgae cell density (algae density reaches 2.5 1× 107 cells /ml). The results of continuous operation show that the removal rates of inorganic nitrogen and inorganic phosphorus in wastewater reach 83% and 95.8% respectively. The concentrations of inorganic nitrogen and inorganic phosphorus in the purified water meet the requirements of Class II standard of Seawater Quality Standard (GB3097- 1997), which can be recycled for seawater culture, greatly reducing the nitrogen and phosphorus pollution load of coastal seawater.
The patent "sponge-microalgae" integrated system invented by Dalian Institute of Chemistry, Chinese Academy of Sciences is to inoculate microalgae in industrial aquaculture wastewater, absorb and transform inorganic nitrogen and inorganic phosphorus in seawater into microalgae biomass; After inoculation for a certain period of time, the sponge is placed in a wastewater pool with increased microalgae biomass, and the microalgae are filtered. Through the joint action of microalgae and sponge, the polluted water body is purified, and the eutrophication problem caused by excessive inorganic nitrogen and phosphorus nutrients discharged into seawater is greatly alleviated.
Decompose organic poisons in the ocean