Algal biofilm harvesting method capable of reducing release of planktonic microalgae

Patent metadata

Field	Value
Publication number	US-12570951-B2
Application number	US-202519190623-A
Country	US
Kind code	B2
Filing date	Apr 26, 2025
Priority date	Jun 4, 2024
Publication date	Mar 10, 2026
Grant date	Mar 10, 2026

Abstract

An algal biofilm harvesting method capable of reducing release of planktonic microalgae includes the following steps: S 1 : constructing an algal biofilm treatment system; S 2 : calculating a cutting area; S 3 : harvesting microalgae biomass; and S 4 : cyclic harvesting. By constructing an algal biofilm treatment system, a surface of an algal biofilm can be regularly cut to harvest microalgae biomass, thereby keeping activity of the biofilm in a best state all the time. In addition, the harvested microalgae biomass can be used as a high-quality substrate for subsequent fermentation, which can achieve resource saving. Quality attainment of effluent from a sewage tank with planktonic microalgae as a suspended solid indicator can be achieved, the treated effluent can be prevented from deteriorating due to an increase of the planktonic microalgae, and a risk that the planktonic microalgae in the effluent of the algal biofilm affects a subsequent treatment process is reduced.

First claim

The invention claimed is:

1 . An algal biofilm harvesting method capable of reducing release of planktonic microalgae, comprising the following steps:
S 1 : constructing an algal biofilm treatment system: placing a biofilm ( 1 ) as a growth carrier of microalgae in a sewage tank, inoculating microalgae communities on the biofilm ( 1 ) to form an algal biofilm, constructing an algal biofilm treatment system after maturation of the algal biofilm, and arranging a plurality of the algal biofilm treatment systems in the sewage tank in turn; S 2 : calculating a cutting area: calculating a coverage area T A of a single algal biofilm, and dividing the algal biofilm into a plurality of cutting units with an area of T C , wherein a total number of cuts is that n=T A /T C , setting the number of days Δt required for cutting all cutting units of the single algal biofilm as a harvest cycle, wherein the number of cutting units cut per day is that n d =T A /(Δt×T C )=n/Δt; S 3 : harvesting microalgae biomass: harvesting microalgae biomass from the single algal biofilm according to the area T C of the cutting unit and the number n d of cutting units cut per day, harvesting one cutting unit from a top corner of the algal biofilm, wherein in each harvest cycle, the cutting units on a same day have no adjacent sides, and the cutting units on adjacent days have no adjacent sides; and controlling a harvest cycle length between the cutting units with adjacent sides to be maximized; wherein in step S 3 , a specific harvesting method of the microalgae biomass is as follows: S 3 - 1 : harvesting one cutting unit from a top corner of the algal biofilm, after collecting one cutting unit along a long side of the algal biofilm, collecting a next cutting unit at an interval of one cutting unit, and harvesting the microalgae biomass from the algal biofilm in sequence until the number of cuts reaches the number of cutting units cut per day; S 3 - 2 : next day, continuing to collect a next cutting unit along a same direction by a cutting method in step S 3 - 1 from a position spaced apart from a previous cutting unit by one cutting unit, if a cutting path has reached a maximum allowable travel distance along the long side of the algal biofilm in the middle, continuing to start traveling again along the long side of the algal biofilm from a position flush with an initial cutting unit at the top corner at an interval of a width of one cutting unit; S 3 - 3 : when a displacement of a column interval of the cutting unit along a short side of the algal biofilm reaches a maximum movable value, starting from an inner vertex of the initial cutting unit at the top corner of the algal biofilm, continuing to harvest the algal biofilm along the long side of the algal biofilm by the cutting method in step S 3 - 1 from a position after respectively moving a length and a width of one cutting unit along the short and long sides of the algal biofilm, when the cutting path reaches the bottom along the long side of the algal biofilm, continuing to travel along the long side from a position flush with the initial cutting unit in the step at an interval of the width of one cutting unit; S 3 - 4 : when a displacement of a column interval of the cutting unit along the short side of the algal biofilm reaches a maximum movable value in step S 3 - 3 , starting from the initial cutting unit at the top corner, continuing to harvest the algal biofilm along the long side of the algal biofilm by the cutting method in Step S 3 - 1 from a position of the cutting unit intersecting the short side and a side edge of the algal biofilm, and when the cutting path reaches the bottom along the long side of the algal biofilm, continuing to travel along the long side from a position flush with the initial cutting unit in the step at an interval of the width of one cutting unit; S 3 - 5 : when a displacement of a column interval of the cutting unit along the short side of the algal biofilm reaches a maximum movable value in step S 3 - 4 , starting from the initial cutting unit at the top corner, continuing to harvest the algal biofilm along the long side of the algal biofilm by the cutting method in Step S 3 - 1 from a position of the cutting unit intersecting the long side and the side edge of the algal biofilm, and when the cutting path reaches the bottom along the long side of the algal biofilm, continuing to travel along the long side from a position flush with the initial cutting unit in the step at an interval of the width of one cutting unit; S 3 - 6 : when a displacement of a column interval of the cutting unit along the short side of the algal biofilm reaches a maximum movable value in step S 3 - 5 , completing one harvest cycle Δt; wherein in step S 1 , the biofilm ( 1 ) as a growth carrier of microalgae is wound on upper and lower drive shafts ( 2 ) in the form of a conveyor belt and rotates synchronously with the drive shafts ( 2 ), the lower drive shaft ( 2 ) is immersed in the sewage tank, the biofilm ( 1 ) is inoculated with microalgae communities to form the algal biofilm, and one algal biofilm treatment system is constructed after the algal biofilm matures; in step S 3 , two algal biofilms on both sides of the single algal biofilm treatment system are taken as two independent algal biofilms and are respectively used for harvesting microalgae biomass; for the algal biofilm at one side, when harvesting the microalgae biomass, the rotating drive shaft ( 2 ) is stopped to a fixed position for microalgae biomass collection, and one cutting unit is harvested from a top corner of the algal biofilm, the drive shaft ( 2 ) is continuously started to rotate the algal biofilm treatment system after harvesting is completed, and the microalgae biomass is synchronously harvested by the algal biofilms on both sides in a mirror-image symmetrical manner; and S 4 : cyclic harvesting: after harvesting microalgae biomass in step S 3 is completed once, harvesting the microalgae biomass again in a same method as in step S 3 to achieve cyclic harvesting.

2 . The algal biofilm harvesting method capable of reducing release of planktonic microalgae according to claim 1 , wherein the biofilm is made of a silicone film.

3 . The algal biofilm harvesting method capable of reducing release of planktonic microalgae according to claim 1 , wherein a result obtained by dividing a length of the algal biofilm by a length of the cutting unit is an integer, and a result obtained by dividing a width of the algal biofilm by a width of the cutting unit is an integer, and the total number n of cuts is greater than or equal to 60 and less than or equal to 375.

4 . The algal biofilm harvesting method capable of reducing release of planktonic microalgae according to claim 1 , wherein a length-width ratio of the algal biofilm is 3:2 or 5:3.

5 . The algal biofilm harvesting method capable of reducing release of planktonic microalgae according to claim 1 , wherein the number n d of cutting units cut per day in step S 2 is an integer, and the harvest cycle Δt is greater than or equal to 7 d and less than or equal to 60 d.

6 . The algal biofilm harvesting method capable of reducing release of planktonic microalgae according to claim 1 , wherein each algal biofilm treatment system in the sewage tank is configured to harvest the microalgae biomass independently and synchronously according to steps in S 3 - 1 to S 3 - 5 .

7 . The algal biofilm harvesting method capable of reducing release of planktonic microalgae according to claim 1 , wherein in step S 3 , the microalgae biomass is harvested by a scraper or hydraulic cutting.

Assignees

• Nanjing University

Inventors

• Lin Yuan
• Chen Yanting
• Wang Liye
• Xu Ke
• Yu Yuexin
• Ren Hongqiang

Classifications

• C02F3/006

  Regulation methods for biological treatment · CPC title

• C02F3/322

  use of algae · CPC title

• C12N1/12 Primary

  Unicellular algae; Culture media therefor (as new plants A01H13/00) · CPC title