Systems for algae-based water filtration and algae harvesting are described herein. A flow-way comprises a channel and a divider positioned within the channel that separates the channel into sub-channels. The flow-way further includes an algal growth that grows on a sidewall of the channel and/or the divider. The algal growth can be established in the flow-way by positioning a pre-seeded mesh element within the channel, the pre-seeded mesh element having an algae culture growing thereon prior to positioning the pre-seeded mesh within the channel. A harvesting system comprises a hinged container that includes a straining screen. The hinged container is positioned downstream from a flow-way and receives water from the flow-way. Biomass in the water is strained by and accumulates on the screen. Weight of the accumulated biomass causes the hinged container to tip and deposit the accumulated biomass in a second container.

A recirculating aquaculture system comprising a microorganism growing apparatus and a method of using microorganisms to remove a pollutant from a fluid utilized in a recirculating aquaculture system. Furthermore, the microorganisms are harvested and used as a foodstuff fertilizer, biofuels, and bioplastics.

The present invention relates to a method and a device for controlling pollutants in basin water used for irrigating farmland in extremely water-scarce areas. The device includes an alternate vertical flow constructed wetland, which is constructed 4-10 m far from basin revetment. After feeding basin water into the constructed wetland, pollutants, such as heavy metals, nitrogen, phosphorus and organic matters, are adsorbed or degraded through the constructed wetland, and then the treated basin water is transported to the farmland.

A method of removing nitrogen-bound nitrate from at least one of groundwater, surface water, or waste water is disclosed. The method includes providing contaminant-containing water from groundwater, surface water, and/or waste water sources. The method further includes adding the contaminant-containing water to an algal photobioreactor system. The method further includes adding an alga culture to the alga photobioreactor system. The method further includes adjusting temperature, CO.sub.2 concentration, pH, light wavelength, and/or light intensity in the algal photobioreactor system to optimize the growth of the algae. The method further includes separating the algae from the water and harvesting algal biomass.

A vacuum airlift system for treating an aqueous effluent includes an upflow liquid portion, where the upflow liquid portion is configured to retain a fluid, and a fluid inlet, the fluid inlet being fluidly coupled with the upflow liquid portion, where the fluid inlet is positioned at about a bottom of the upflow liquid portion. The vacuum airlift system can also include a downflow liquid portion, where the downflow liquid portion is fluidly coupled with the upflow liquid portion, and a fluid outlet, the fluid outlet being fluidly coupled with the downflow liquid portion, where the fluid outlet is positioned at about a bottom of the downflow liquid portion. The vacuum airlift system can also include a photobioreactor fluidly coupled with the downflow liquid portion such that the fluid is configured to pass through the upflow liquid portion, into the downflow liquid portion, and into the photobioreactor.

The present disclosure relates to methods of culturing algae that overcomes catabolic repression of photosynthesis in mixotrophic growth.

Provided is a technique capable of efficiently removing nitrogen contained in water to be treated and efficiently recovering microplastics from the water to be treated. An aspect of the present invention is a water treatment system 10 including an aquaculture tank 20 and a water treatment tank 30. Aquatic organisms are cultivated in the aquaculture tank 20. In the water treatment tank 30, algae having a microplastic adsorption and recovery ability grow in the water to be treated introduced from the aquaculture tank 20. The microplastics contained in the water to be treated are recovered, and the nitrogen compounds contained in the water to be treated are removed, by the algae.

To provide a new technique for efficiently recovering microplastics from water to be treated, in which problems of conventional techniques such as large energy consumption are solved. A method for recovering microplastics from water to be treated containing the microplastics, the method comprising a step of allowing algae having microplastic adsorption and recovery ability to be present in the water to be treated, in which the algae are algae that secrete a sticky substance, and an amount of a sticky substance secreted by the algae is such that a volume of a sticky substance secreted to an outside of cells is 0.25 times or more and 100 times or less compared to a cell volume.

A method comprises flowing a mixture comprising a water-based reaction medium and at least one microalgae into a reaction vessel, wherein the reaction medium comprises a nutrient material that is consumable by a live microalgae, bacterium, or protozoa present in the reaction medium, incubating the mixture under at least intermittent illumination with a specified luminous flux such that the microalgae forms a supporting matrix that incorporates the live microalgae, bacterium, or protozoa into biologically-active bioaggregate granules, selecting out a first specified portion of the biologically-active bioaggregate granules that are smaller than a first specified size or below a first specified weight or selecting out a second specified portion of the biologically-active bioaggregate granules that are larger than a second specified size or over a second specified weight and removing the first and/or the second specified portions of the biologically-active bioaggregate granules in an effluent stream.

The present application discloses a method of binding a metal ion in water. The method comprises contacting the water with a fraction of dissolved organic material (DOM) to form a complex between the DOM fraction and the metal ion; and optionally separating the complex from the water. The present application also discloses a use of DOM for binding a metal ion in water.