Feasibility of typha latifolia for high salinity effluent treatment in constructed wetlands for integration in resource management systems

Abstract

High salinity wastewaters have limited treatment options due to the occurrence of salt inhibition in conventional biological treatments. Using recirculating marine aquaculture effluents as a case study, this work explored the use of Constructed Wetlands as a treatment option for nutrient and salt loads reduction. Three different substrateswere tested for nutrient adsorption, of which expanded clay performed better. This substrate adsorbed 0.31 mg kg−1 of NH4 +−N and 5.60 mg kg−1 of PO4 3−−P and 6.9 mg kg−1 dissolved salts after 7 days of contact. Microcosms with Typha latifolia planted in expanded clay and irrigated with aquaculture wastewater (salinity 2.4%, 7 days hydraulic retention time, for 4 weeks), were able to remove 94%NH4 +−N(inlet 0.25±0.13 mg L−1), 78%NO2 −−N(inlet 0.78±0.62 mg L−1), 46% NO3 −−N (inlet 18.83 ± 8.93 mg L−1) whereas PO4 3−−P was not detected (inlet 1.41 ± 0.21 mg L−1). Maximum salinity reductions of 52% were observed. Despite some growth inhibition, plants remained viable, with 94% survival rate. Daily treatment dynamics studies revealed rapid PO4 3−−P adsorption, unbalancing the N:P ratio and possibly affecting plant development. An integrated treatment approach, coupled with biomass valorization, is suggested to provide optimal resource management possibilities.