Method for alkaline flocculation harvesting and circulation culture of microalgae

Abstract

The invention provides a method for alkaline flocculation harvesting and circulation culture of microalgae. According to the method, bicarbonate is utilized as a carbon source to culture the microalgae. During the cultivation process, as the microalgae biomass grows and hydrogencarbonate is consumed, the pH rises, to form a highly alkaline environment which can induce self-flocculation of the microalgae, and the harvesting of the microalgae biomass is achieved; low concentrations of flocculating ions such as calcium, magnesium and iron are added into a culture liquid in the highly alkaline environment, the occurrence of flocculation can be produced, the microalgae biomass is harvested efficiently and quickly, the use of a high-cost high-concentration flocculant is avoided, and the problemof biomass pollution is solved. After the flocculation is harvested, CO2 is absorbed by a high alkaline medium rich in carbonate, and bicarbonate is regenerated as a carbon source and reused for microalgae cultivation to re-use water and nutrients, reducing the cost of microalgae cultivation. Therefore, the method can reduce cultivation and harvesting costs of the microalgae simultaneously and have promotion and application prospects in the field of large-scale cultivation of the microalgae.

Description

technical field [0001] The invention relates to the field of microalgae biotechnology, in particular to a method for harvesting microalgae by means of cyclic cultivation of microalgae and alkaline flocculation. Background technique [0002] Microalgae are a type of photosynthetic autotrophic microorganisms, rich in protein, polyunsaturated fatty acids, pigments and other nutrients. At the same time, because of its strong environmental adaptability, fast growth, high carbon sequestration efficiency, and high biomass, it has important applications in the fields of pharmaceutical industry, food industry, animal feed, bioenergy, and environmental protection. But large-scale cultivation of microalgae is still limited by high costs, including the cost of carbon sources, the cost of water and nutrients, and the cost of harvesting microalgae. [0003] Among them, the cost of carbon source is the main factor limiting the large-scale cultivation of microalgae. The traditional algae ...

AI Technical Summary

Problems solved by technology

The traditional algae culture system continuously bubbles CO into the culture system 2 Although providing carbon source for algae can ensure high-efficiency gas-liquid mass transfer, there are still deficiencies in this technology: first, CO 2 The high transportation cost, high energy consumption and low utilization efficiency make the cost of algae culture remain high

It has been reported in the literature that CO in flue gas can be utilized 2 , but due to the high concentration of CO separated from the flue gas 2 Need to consume a huge amount of energy; secondly, the separated CO 2 It needs to be transported to the algae culture base through pipelines, and the cost of pipelines is relatively high; moreover, the flue gas contains a large amount of toxic substances, including substances rich in sulfur and nitrogen, which will seriously affect the normal growth of algae; The second is CO 2 Aeration makes microalgae culture reactor scale-up problematic, limiting its large-scale commercial production

These problems can be overcome by using bicarbonate, but the cost of bicarbonate itself is relatively high, so it needs to be recycled

In addition, the high pH generated by bicarbonate consumption not only inhibits the growth of microalgae, but also carbonate cannot be utilized by microalgae at high pH, ​​so that the growth of microalgae is limited by carbon sources.

In addition, if the microalgae culture medium cannot be reused and discharged directly, the large amount of nutrients it contains not only has a huge environmental damage effect, such as water pollution, but also becomes a waste of resources, reducing the income of microalgae will also cause

[0004] In addition, due to the characteristics of microalgae cells, harvesting is difficult and costly, and the cost of harvesting microalgae accounts for 20-30% of the entire industrial chain

The traditional microalgae biomass harvesting methods are mainly centrifugation, filtration, flocculation by adding inorganic or organic flocculants, etc. Among these harvesting methods, there are advantages and disadvantages: centrifugal harvesting has high efficiency and wide applicability but consumes energy Larger, it will damage the algae and is not suitable for large-scale application; filtration is more economical, but it is easy to cause membrane pollution and reduce the recovery efficiency; the effect of flocculant recovery is obvious, but adding flocculant to the water body will introduce foreign Compounds cause water pollution, affecting downstream operations and making it difficult to separate again

On the other hand, due to the high price of flocculants, the use of flocculants will increase production costs, and their use in large-scale commercial production of microalgae is limited.

[0005] In summary, the use of traditional microalgae cultivation methods and biomass harvesting methods still have disadvantages such as high energy consumption and high cost, which hinder the commercialization of large-scale production of microalgae.

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