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Improvement of the cost effectiveness of marine land based aquaculture facilities through use of Constructed Wetlands with Salicornia as an environmentally friendly biofilter and a valuable by product

Final Report Summary - ENVIROPHYTE (Improvement of the cost effectiveness of marine land based aquaculture facilities through use of Constructed Wetlands with Salicornia ...)

The cost of water treatment in land based aquaculture facilities is of major importance for the economic viability of the small and medium enterprises (SMEs) operating in the sector. Fishmeals are only partially consumed by the species. An important amount of their contents is excreted into water, mainly as solid organic or dissolved inorganic compounds which could pollute coastal ecosystems. The European and international regulations require treatment of fisheries effluents prior to their discard to the sea, thus imposing an economic burden on SMEs viability.

The ENVIROPHYTE project proposed a low cost, simply to operate alternative to conventional treatment through the use of constructed wetlands (CWs) planted with halophytes, which converted the nutrient rich wastewater into marketable plant biomass. The selected halophyte was salicornia, which could survive in different climatic conditions and had various applications in the health food, nutraceutical and beauty industries, thus being a commercially interesting species. The market of salicornia consisted of gathering branches of wild plants, resulting in inconstant quality and quantity of the raw material; hence the potential for cultivation appeared particularly attractive. As a result, the exploitation of the plant as an inexpensive CW biofilter along with its commercial viability could increase significantly the profitability of marine land based facilities.

ENVIROPHYTE specific objectives were to:
1. develop CW with salicornia in warm, temperate and cold water conditions and prove that it was feasible to remove at least 80 % of the pollutants in all cases;
2. present innovative agronomic management practices to improve salicornia productivity using marine fishpond effluents;
3. increase the cost-effectiveness of CW salicornia by enhancing the quality and thus, the value of the unprocessed material to meet specifications of health food markets;
4. use the raw material for production of specific extracts for high value applications in order to prove that profitable production of new active substances was feasible;
5. analyse the costs and benefits of the CW under different scenarios and climate conditions.

Engineering design, specifications' definition and optimisation of the three experimental CWs were performed, so that the developed prototypes could be applied, in case successful, at a commercial scale. The sites were operated under surface and subsurface flow regimes. The latter were more efficient for both water treatment and plant production. The temperate water conditions' site though, treating flow-through farms, was not as effective as those of warm and cold water temperature, which removed up to 90 % of the nutrients.

A new agronomic technique for increased salicornia production within the CW was developed. The proposed cultivation units, growth medium and agro-management practices were ready for application. Recommended topics for future research concerned the refinement of harvesting methods so as to reduce labour cost and the examination of other alternative crop plants.

The produced salicornia properties were assessed using quality control, sensory evaluation and results of submission to wholesaler or end-users. All samples met the market demands and applicable regulations' standards. The alternative sarcocornia samples from the temperate conditions' site were not exploitable by the food industry; nevertheless, they could be used for cosmetics applications. In addition, two extracts possessing anti-oxidant properties were produced and used for different types of cosmetic formulations, with promising results. However, further research was required in this direction before delivering end products to the market.

The bioeconomic evaluation of CWs showed that they were well adaptable and offered an interesting profit margin to marine hatcheries and land-based recirculated fish farms, which had limited water flows and sufficient nutrient concentrations. The technology was less efficient in flow-through fish farms with high flow rates and low nutrient loads. The construction of larger sites was expected to confirm the pilot scale analysis outcomes.

The ENVIROPHYTE project offered an effective and profitable alternative to the applied fisheries water treatment techniques. The investigation of additional uses of salicornia in the cosmetics industry rendered the proposal even more appealing as an income source. Potential clients were mainly land based marine farmers, including on-growing facilities, pre-growing facilities and marine hatcheries. Moreover, the method could be applied in underdeveloped regions with salty water, which were unsuitable for conventional agriculture.

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