Growth of mono- and mixed cultures of Nannochloropsis salina and Phaeodactylum tricornutum on struvite as a nutrient source.

The suitability of crude and purified struvite (MgNH4PO4), a major precipitate in wastewater streams, was investigated for renewable replacement of conventional nitrogen and phosphate resources for cultivation of microalgae. Bovine effluent wastewater stone, the source of crude struvite, was characterized for soluble N/P, trace metals, and biochemical components and compared to the purified mineral. Cultivation trials using struvite as a major nutrient source were conducted using two microalgae production strains, Nannochloropsis salina and Phaeodactylum tricornutum, in both lab and outdoor pilot-scale raceways in a variety of seasonal conditions.

Size and structure of Chlorella zofingiensis/FeCl(3) flocs in a shear flow.

Flocculation is a promising method to overcome the economic hurdle to separation of algae from its growth medium in large scale operations. However, understanding of the floc structure and the effects of shear on the floc structure are crucial to the large scale implementation of this technique. The floc structure is important because it determines, in large part, the density and settling behavior of the algae.

Critical conditions for ferric chloride-induced flocculation of freshwater algae.

The effects of algae concentration, ferric chloride dose, and pH on the flocculation efficiency of the freshwater algae Chlorella zofingiensis can be understood by considering the nature of the electrostatic charges on the algae and precipitate surfaces. Two critical conditions are identified which, when met, result in flocculation efficiencies in excess of 90% for freshwater algae. First, a minimum concentration of ferric chloride is required to overcome the electrostatic stabilization of the algae and promote bridging of algae cells by hydroxide precipitates.

Shear-induced phase separation in polyelectrolyte/mixed micelle coacervates.

A quantitative study of the shear-induced phase separation of a polycation/anionic-nonionic micelle coacervate is presented. Simultaneous rheology and small-angle light scattering (SALS) measurements allow the elucidation of micrometer-scale phase separation under flow in three coacervate solutions. Below 18 degrees C, all three of the coacervate solutions are optically clear Newtonian fluids across the entire shear rate range investigated.