Effectiveness of halophytic plants in the treatment of marine aquaculture wastewater

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This study aims to assess the overall efficiency of S. europaea and A. tripolium plants in wastewater treatment in saline aquaculture systems (IMTA), while generating a valuable secondary crop. Specifically plant N uptake and/or biomass production under different N concentration and forms, salinity, irradiance, temperature and cropping regimes are investigated. It is estimated that at a constant supply of ≥ 300 μmol NO3- l-1 S. europaea N removal of 65.3 ± 18.1 mmol N plant-1 can be achieved over one growing season. Plant growth in a non N limited hydroponic system, with or without a repeated harvest regime, showed that uncropped plants accumulated more fresh biomass than cropped (S. europaea 34 kg m-2 and 17 kg m-2, A. tripolium 21 kg m-2 and 10 kg m-2, respectively). N removal is closely related to plant biomass, and therefore the repeated harvesting can reduce N removal, however it provides a regular high value product for marketing. S. europaea showed better growth when supplied with NO3- or NH4NO3, comparing to NH4+, while A. tripolium growth was not affected by the form of N. The measured A. tripolium and S. europaea DIN uptake, as NH4+ and NO3-, when supplied separately or in an equimolar mix were in general good fits to the Michaelis-Menten model. NH4-15N uptake rates are higher than NO3-15N uptake, except in non-starved S. europaea for single N forms supplied alone. Inhibition of NO3-15N uptake by the presence of NH4+ in solution was observed in non-starved plants. S. europaea responds negatively to salinity 1 compared to 10 and 30, while A. tripolium responds negatively to salinity 30, indicating the suitability of both plant species to be used in systems with middle range salinities, but preference for S. europaea over A. tripolium at higher salinities and vice versa. DIN uptake in both plant species increased linearly with increasing irradiance, and was higher at the mid-range of temperatures tested (20-40 °C). Differences in N uptake with varying environmental conditions needs to be further investigated and taken in account when designing the treatment system. S. europaea and A. tripolium were shown to uptake organic N at comparable rates to DIN uptake, and when in solution more than 68% of organic N uptake was as intact alanine and trialanine indicating the potential of these plants to directly remove DON from the wastewater. Overall the results obtained indicate that S. europaea and A. tripolium are able to perform well in IMTA, with efficient N removal and high biomass production. The data obtained provides a sound basis for system design and scaling up.


Original languageEnglish
    Award dateJan 2013