Beneficial use of dredged sediment for removal of harmful algal bloom fueling nutrients.

Harmful Algal Blooms (HABs) are pervasive in freshwater and marine waters requiring advances in monitoring, prevention and control of active blooms. Prevention through interception of nutrient runoff that feed HABs is critical to reducing future impacts. This research provides a logical convergence of complementary goals of mitigating the severity of HABs and increasing beneficial use of dredged sediment conveniently sourced from Confined Disposal Facilities (CDFs). This work innovates use of additive manufacturing (AM), or 3D printing, to generate porous, geometrically complex sediment structures to adsorb and intercept nutrients in runoff water prior to discharge into surface water. While this technology application is widely applicable, proof-of-principle of nutrient removal capability is demonstrated using a 3D printed dredged sediment mound that was strategically placed on a 3 by 3-foot physical landscape model that was also completely 3D printed. The sediment mound structure was specifically printed into parallel roadways forming channels to increase preferential infiltration of run-off water into the otherwise clayey sediment. Nutrients were measured before and after pumped runoff water passed through either amended (biochar, commercial resins) or unamended dredged sediment structures and demonstrated that the unamended marine-sourced dredged sediment had sufficient capacity to almost immediately reduce concentrations of phosphate by 79 to 98% and nitrate by 93 to 99% from runoff discharge. This concept may be scaled using hoppers, excavators and trucks to move sediment from nearby CDFs to a runoff site for field demonstration and application.