EVALUATION OF THE TREATMENT EFFICIENCY OF A HYBRID POPLAR Populus spp VEGETATIVE FILTER ON HYBRID STRIPED BASS Morone chrysops x Morone saxatilis POND EFFLUENTS

In the United States, the Clean Water Act require states to issue permits to aquaculture facilities producing over 100,000 pounds of fish and/or releasing water more than 30 days a year with explicit discharge limits. An alternative practice to simply releasing effluents is their application to vegetative filters, or phytoremediation (PR). PR is commonly used in the treatment of land applied wastewaters, nutrient remediation, and hydraulic management. In addition, PR with hybrid poplars (Populus spp.) may provide opportunity to produce woody biomass for the emerging bioenergy markets. This study evaluated land application of aquaculture effluents to a hybrid poplar vegetative filter consisting of 16 clones for PR of nutrients and contaminants entering local surface and groundwater.

Effluent was land applied weekly from April to October at a rate of 22.86 mm per event. Water quality samples were collected biweekly from the irrigated effluent, shallow groundwater monitoring wells, and subsurface discharge to surface water. As of August 2015, this 0.49 ha hybrid poplar biofilter treated 572 m³ of effluent over 32 irrigation events, increasing the total amount of water trees received each month, beyond precipitation, by an average of 40% (Fig. 1).

Removal efficiencies for total suspended solids (TSS) and chlorophyll A (Chl a) were evaluated in a hybrid poplar vegetation filter receiving land applied hybrid striped bass (HSB) aquaculture effluent from intensively managed freshwater ponds. A trend of improving water quality was observed with a mean decline of 78.19% in Chl a levels and of 44.11% in TSS in irrigated effluent as compared to subsurface export (Fig. 2). The site export levels of both TSS and Chl a remained stable throughout the season even as the application levels of both increased with growing pond productivity. The top producing tree clones reached heights of roughly 15 feet and could be harvested for bioenergy production in 2-4 years. Other data on nitrogen and phosphorous dynamics will be presented.