BIOLOGICAL AND ALGAE HARVESTING AND CULTIVATION SYSTEMS AND METHODS
Algae harvesting and cultivating systems and methods for producing high concentrations of algae product with minimal energy. In an embodiment, a dead-end filtration system and method includes at least one tank and a plurality hollow fiber membranes positioned in the at least one tank. An algae medium is pulled through the hollow fiber membranes such that a retentate and a permeate are produced.
1 . An algae harvesting system comprising:
at least one treatment tank;
at least one membrane filtration module positioned inside the at least one treatment tank, the at least one membrane filtration module including a plurality of hollow fiber membranes defining lumens; and
wherein the system is configured to:
(a) perform dead-end filtration of an algae slurry contained in the at least one treatment tank by pulling a substantially algae-free permeate through pores of the plurality of hollow fiber membranes so that the permeate flows inside the lumens of the plurality of hollow fiber membranes and a retentate of the algae slurry is produced outside the lumens of the plurality of hollow fiber membranes, and
(b) perform a backwash sequence in which a backwash fluid flows inside the lumens of the plurality of hollow fiber membranes and is pushed through the pores of the plurality of hollow fiber membranes to remove any foulants that have accumulated on the plurality of hollow fiber membranes, the backwash sequence including an off-line period of less than about twelve seconds.
2 . The algae harvesting system of claim 1 , wherein the backwash sequence includes an interval of less than about three minutes, and the interval including the time between the start of one backwash cycle and the start of a next backwash cycle.
3 . The algae harvesting system of claim 2 , wherein (i) the algae slurry in the at least one treatment tank is a non-flocculated algae slurry having a first concentration of suspended algae, and (ii) the retentate has a second concentration of suspended algae that is greater than the first concentration, the second concentration equal to at least three percent.
4 . The algae harvesting system of claim 2 , wherein (i) the algae slurry in the at least one treatment tank is a non-flocculated algae slurry having a first concentration of suspended algae, and (ii) the retentate has a second concentration of suspended algae that is about fifty times greater than the first concentration.
5 . The algae harvesting system of claim 2 , wherein the at least one treatment tank includes (a) a plurality of treatment tanks in which each of the treatment tanks defines one stage of a plurality of filtration stages and contains at least one of a plurality of membrane filtration modules, or (b) at least one divider separating the at least one treatment tank into a plurality of filtration stages, each of the plurality of filtration stages containing at least one of a plurality of membrane filtration modules.
6 . The algae harvesting system of claim 2 ,
wherein the plurality of hollow fiber membranes are a first plurality of hollow fiber membranes and which includes a second plurality of hollow fiber membranes;
wherein the at least one filtration module is a first at least one membrane filtration module and which includes a second at least one membrane filtration module; and
wherein the least one treatment tank defines a plurality of filtration stages including at least a first filtration stage and a second filtration stage, and
wherein the first filtration stage includes:
the first at least one membrane filtration module positioned inside the at least one treatment tank, said at least one membrane filtration module including the first plurality of hollow fiber membranes defining lumens and having a first total outside filtration area,
a retentate outlet, and
a permeate outlet, and
wherein the second filtration stage includes:
the second at least one membrane filtration module positioned inside the at least one treatment tank, said second at least one membrane filtration module including the second plurality of hollow fiber membranes defining lumens and having a second total outside filtration area,
an inlet coupled fluidly to the retentate outlet of the first filtration stage,
a retentate outlet, and
a permeate outlet; and
wherein the system is configured to perform the dead-end filtration by pulling the permeate through (i) the pores of the first plurality of hollow fiber membranes in the first filtration stage and (ii) pores of the second plurality of hollow fiber membranes so that the retentate is produced outside the lumens of the first and second plurality of hollow fiber membranes.
7 . The algae harvesting system of claim 6 , wherein the first total outside filtration area of the first plurality of hollow fiber membranes is different from the second total outside filtration area of the second plurality of hollow fiber membranes.
8 . The algae harvesting system of claim 6 ,
which includes at least one backwash tank constructed and arranged to hold the backwash fluid and coupled fluidly with the first and second filtration stages via at least one conduit, the backwash tank positioned such that the level of backwash fluid in the backwash tank is above the level of fluid in the at least one treatment tank; and
wherein the system is configured to perform the backwash sequence by gravity flowing the backwash fluid from the backwash tank to the inside of the lumens of the first and second plurality of hollow fiber membranes so that the backwash fluid is pushed through the pores of the first and second plurality of hollow fiber membranes to remove any foulants that have accumulated on the plurality of hollow fiber membranes.
9 . The algae harvesting system of claim 6 ,
which includes at least one permeate tank coupled fluidly with the first and second filtration stages via at least one conduit so as to receive the permeate from the first and second filtration stages, the at least one permeate tank positioned such that that the level of fluid in the at least one permeate tank is lower than the level of fluid in the at least one treatment tank; and
wherein the system is configured to perform the dead-end filtration by siphoning the permeate through the pores of the first and second plurality of hollow fiber membranes.
10 . The algae harvesting system of claim 6 , wherein (i) the interval of the backwash sequence is a first interval in the first filtration stage, and the interval includes a second interval in the second filtration stage, the second interval including the time between the start of one backwash cycle in the second filtration stage and the start of a next backwash cycle in the second filtration stage, and (ii) the second interval is shorter than the first interval.
11 . The algae harvesting system of claim 6 , wherein the backwash sequence off-line period is a first off-line period in the first filtration stage, and the backwash sequence off-line period includes a second off-line period in the second filtration stage, wherein the second off-line period is shorter than the first off-line period.
12 . The algae harvesting system of claim 6 , wherein the first filtration stage includes an earthen lined pond.
13 . The algae harvesting system of claim 1 , wherein at least about seventy-five percent of the suspended algae in the retentate is alive.
14 . The algae harvesting system of claim 1 , wherein the backwash off-line period includes the time to (i) disallow the permeate flow inside the lumens of the plurality of hollow fiber membranes, (ii) begin the backwash fluid flow to the inside of the lumens, (iii) disallow the backwash fluid flow to the inside of the lumens, and (iv) begin the permeate flow inside the lumens.
15 . The algae harvesting system of claim 1 ,
which includes (i) at least one conduit coupled fluidly to the at least one membrane filtration module, and (ii) a plurality of valves coupled fluidly to the at least one conduit; and
wherein the system is configured to: (a) selectively open and close the plurality of valves to disallow the permeate flow inside the lumens and allow the backwash fluid flow inside the lumens, and (b) open and close the plurality of valves to disallow the backwash fluid flow inside the lumens and to allow the permeate flow inside the lumens, and wherein an actuation time for the plurality of valves is about three seconds or less, the actuation time including the time to open the plurality of valves or close the plurality of valves.
16 . The algae harvesting system of claim 1 ,
which includes at least one permeate tank coupled fluidly with the at least one treatment tank via at least one permeate conduit so as to receive the permeate, the at least one permeate tank positioned such that that the level of permeate fluid in the at least one permeate tank is lower than the level of fluid in the at least one treatment tank; and
wherein the system is configured to perform the dead-end filtration by siphoning the permeate through the pores of the plurality of hollow fiber membranes.
17 . The algae harvesting system of claim 16 , which includes a purge conduit coupled fluidly to the at least one permeate conduit, and a gas purge valve coupled fluidly to the purge conduit such that when the gas purge valve is opened during the backwash sequence, an increase in pressure in the at least one permeate conduit also increases a pressure in the purge conduit to allow any gas to be purged through the purge conduit.
18 . The algae harvesting system of claim 1 , which includes at least one backwash tank constructed and arranged to hold the backwash fluid, the backwash tank positioned such that the level of backwash fluid held in the backwash tank is above the level of fluid in the at least one treatment tank, and wherein the system is configured to perform the backwash sequence by gravity flowing the backwash fluid from the backwash tank to the inside of the lumens of the plurality of hollow fiber membranes so that the backwash fluid is pushed through the pores of the plurality of hollow fiber membranes to remove any foulants that have accumulated on the plurality of hollow fiber membranes.
19 . The algae harvesting system of claim 1 , wherein the backwash fluid is the permeate.
20 . The algae harvesting system of claim 1 , wherein the system includes a controller, the controller configured to perform the dead-end filtration and the backwash sequence.
21 . The algae harvesting system of claim 1 ,
which includes an air blower coupled fluidly to the at least one treatment tank; and
wherein the system is configured to control the blower so as to generate air bubbles below the hollow fiber membranes so as to aid in removing any foulants that have accumulated on the hollow fiber membranes.
22 . The algae harvesting system of claim 1 ,
which includes at least one cassette positioned inside the at least one treatment tank, the cassette including the at least one membrane filtration module; and
wherein the at least one membrane filtration module includes a plurality of membrane filtration modules coupled fluidly in parallel via a cassette header.
23 . The algae harvesting system of claim 1 ,
which includes a bank positioned inside the at least one treatment tank, the bank including a first cassette and a second cassette, the first cassette and the second cassette coupled fluidly in parallel via a bank header; and
wherein (i) the at least one membrane filtration module includes a first plurality of membrane filtration modules and a second plurality of membrane filtration modules, and (ii) the first cassette includes the first plurality of membrane filtration modules coupled fluidly in parallel via a first cassette header, and the second cassette includes the second plurality of membrane filtration modules coupled fluidly in parallel via a second cassette header.
24 . The algae harvesting system of claim 1 , wherein the system is configured to use less than 0.16 kWh of energy per cubic meter of permeate to perform (i) and (ii) so as to produce a retentate that has a concentration of solid algae of at least 1%.
25 . The algae harvesting system of claim 1 , wherein the backwash fluid includes at least one of a liquid and a gas.
26 . An algae harvesting system comprising:
at least one treatment tank;
at least one membrane filtration module positioned inside the at least one treatment tank, the at least one membrane filtration module including a plurality of hollow fiber membranes defining lumens; and
wherein the system is configured to:
(a) perform dead-end filtration of an algae slurry contained in the at least one treatment tank by pulling a substantially algae-free permeate through pores of the plurality of hollow fiber membranes so that the permeate flows inside the lumens of the plurality of hollow fiber membranes and a retentate of the algae slurry is produced outside the lumens of the plurality of hollow fiber membranes, and
(b) perform a backwash sequence in which a backwash fluid flows inside the lumens of the plurality of hollow fiber membranes and is pushed through the pores of the plurality of hollow fiber membranes to remove any foulants that have accumulated on the plurality of hollow fiber membranes, the backwash sequence including an interval of less than about three minutes, and the interval including the time between the start of one backwash cycle and the start of a next backwash cycle.
27 . The algae harvesting system of claim 26 , wherein at least about seventy-five percent of the suspended algae in the retentate is alive.
28 . The algae harvesting system of claim 26 ,
which includes (i) at least one conduit coupled fluidly to the at least one membrane filtration module, and (ii) a plurality of valves coupled fluidly to the at least one conduit; and
wherein the system is configured to: (a) selectively open and close the plurality of valves to disallow the permeate flow inside the lumens and allow the backwash fluid flow inside the lumens, and (b) open and close the plurality of valves to disallow the backwash fluid flow inside the lumens and to allow the permeate flow inside the lumens, and wherein an actuation time for the plurality of valves is about three seconds or less, the actuation time including the time to open the plurality of valves or close the plurality of valves.
29 . The algae harvesting system of claim 26 , which includes at least one permeate tank coupled fluidly with the at least one treatment tank via at least one permeate conduit so as to receive the permeate, the at least one permeate tank positioned such that that the level of permeate fluid in the at least one permeate tank is lower than the level of fluid in the at least one treatment tank, and wherein the system is configured to perform the dead-end filtration by siphoning the permeate through the pores of the plurality of hollow fiber membranes.
30 . The algae harvesting system of claim 26 , which includes a purge conduit coupled fluidly to the at least one permeate conduit, and a gas purge valve coupled fluidly to the purge conduit such that when the gas purge valve is opened during the backwash sequence, an increase in pressure in the at least one permeate conduit also increases a pressure in the purge conduit to allow any gas to be purged through the purge conduit.
31 . The algae harvesting system of claim 26 ,
which includes at least one backwash tank constructed and arranged to hold the backwash fluid, the backwash tank positioned such that the level of backwash fluid held in the backwash tank is above the level of fluid in the at least one treatment tank; and
wherein the system is configured to perform the backwash sequence by gravity flowing the backwash fluid from the backwash tank to the inside of the lumens of the plurality of hollow fiber membranes so that the backwash fluid is pushed through the pores of the plurality of hollow fiber membranes to remove any foulants that have accumulated on the plurality of hollow fiber membranes.
32 . The algae harvesting system of claim 26 , wherein the backwash fluid is the permeate.
33 . The algae harvesting system of claim 26 , wherein the system includes a controller, the controller configured to perform the dead-end filtration and the backwash sequence.
34 . The algae harvesting system of claim 26 , which includes an air blower coupled fluidly to the at least one treatment tank, and wherein the system is configured to control the blower to generate air bubbles below the hollow fiber membranes so as to aid in removing any foulants that have accumulated on the hollow fiber membranes.
35 . The algae harvesting system of claim 26 ,
which includes at least one cassette positioned inside the at least one treatment tank, the cassette including the at least one membrane filtration module; and
wherein the at least one membrane filtration module includes a plurality of membrane filtration modules coupled fluidly in parallel via a cassette header.
36 . The algae harvesting system of claim 26 ,
which includes a bank positioned inside the at least one treatment tank, the bank including a first cassette and a second cassette, the first cassette and the second cassette coupled fluidly in parallel via a bank header; and
wherein (i) the at least one membrane filtration module includes a first plurality of membrane filtration modules and a second plurality of membrane filtration modules, and (ii) the first cassette includes the first plurality of membrane filtration modules coupled fluidly in parallel via a first cassette header, and the second cassette includes the second plurality of membrane filtration modules coupled fluidly in parallel via a second cassette header.
37 . The algae harvesting system of claim 26 , wherein the system is configured to use less than 0.16 kWh of energy per cubic meter of permeate to perform (i) and (ii) so as to produce a retentate having a concentration of solid algae of at least 1%.
38 . The algae harvesting system of claim 26 , wherein the backwash fluid includes at least one of a liquid and a gas.
39 . The algae harvesting system of claim 26 , wherein the at least one treatment tank includes (a) a plurality of treatment tanks in which each of the treatment tanks defines one stage of a plurality of filtration stages and contains at least one of the plurality of membrane filtration modules, or (b) at least one divider separating the at least one treatment tank into a plurality of filtration stages, each of the plurality of filtration stages containing at least one of a plurality of membrane filtration modules.
40 . An algae harvesting method comprising:
in a dead end filtration process, pulling a substantially algae-free permeate from an algae slurry through pores of a plurality of hollow fiber membranes positioned inside at least one treatment tank so that the permeate flows inside lumens of the plurality of hollow fiber membranes and a retentate of the algae slurry is produced outside the lumens of the plurality of hollow fiber membranes; and
in a backwash sequence, pushing a backwash fluid through pores of the plurality of hollow fiber membranes to remove any foulants that have accumulated on the plurality of hollow fiber membranes, wherein the backwash sequence includes (i) an interval of less than about three minutes, the interval including the time between the start of one backwash cycle and the start of a next backwash cycle and (ii) an off-line period of less than about twelve seconds.
41 . The algae harvesting method of claim 40 , wherein (i) the algae slurry is a non-flocculated algae slurry having a first concentration of suspended solid algae, and (ii) the retentate has a second concentration of suspended solid algae that is greater than the first concentration, the second concentration equal to at least three percent.
42 . The algae harvesting method of claim 40 , wherein (i) the algae slurry is a non-flocculated algae slurry having a first concentration of suspended solid algae, and (ii) the retentate has a second concentration of suspended solid algae that is about fifty times greater than the first concentration.
43 . The algae harvesting method of claim 40 , wherein at least about seventy-five percent of the suspended algae in the retentate is alive.
44 . The algae harvesting method of claim 40 , wherein said pulling during the dead-end filtration process includes siphoning.
45 . The algae harvesting method of claim 44 , wherein said pushing during the backwash sequence includes pushing gas accumulated in a siphon conduit through a purge conduit coupled fluidly to the siphon conduit.
46 . The algae harvesting method of claim 40 , where said pushing during the backwash sequence includes gravity feeding the backwash fluid.
47 . The algae harvesting method of claim 40 , wherein the backwash fluid includes at least one of a liquid and a gas.
48 . The algae harvesting method of claim 40 , wherein the plurality of hollow fiber membranes are positioned in at least one treatment tank, and the at least one treatment tank includes (a) a plurality of treatment tanks in which each of the treatment tanks defines one stage of a plurality of filtration stages and contains at least one of the plurality of membrane filtration modules, or (b) at least one divider separating the at least one treatment tank into a plurality of filtration stages, each of the plurality of filtration stages containing at least one of a plurality of membrane filtration modules.