We report herein the crystal growth of ZnO nanoparticles by the foam fractionation method. In this study, the vertical column height of the foam was fixed and the velocity of the sparging air was varied, and the effect of foam flow rate on the synthesis of ZnO was investigated. The obtained ZnO consisted of aggregated platelets and had differing ultraviolet absorbances. The as-synthesized ZnO was hydrophobic because of the interaction between the anionic head groups of sodium dodecyl sulfate (SDS) and the ZnO under the precipitation conditions. The long chain of the SDS molecule was the cause of hydrophobicity. The contact angle of water was in the range of 95–105° for the obtained ZnO/SDS surface. The photocatalytic degradation efficiency of the as-synthesized (ZnO/SDS) and the calcined ZnO was investigated for methylene blue, and the calcined ZnO retained its activity even after three recycles.

Marine land-based fish farms located in coastal wetlands (salt-pond zones, lagoon banks, etc.), whether extensive or intensive, send farm effluents directly to the sea or after short periods of stocking in retention reservoirs. The aims of our investigation have been to compare the efficiency of current and potential water treatment procedures in open-air. Wastewater retention ponds in commercial farms (Atlantic coasts of France) are efficient in removing up to 1 metric ton of particulate material (dry weight) per hectare and per day (faeces and unconsumed feed), but are inefficient in reducing dissolved wastes, both organic (urea, amino acids, protein) and inorganic (total ammonia nitrogen, phosphates). Forthcoming outdoor technology to treat these forms of waste were examined by trials at different sites: treatment by foam fractionation in extensive systems (Italian fish pond culture), treatment by microalgae production (Skeletonema costatum) and oyster filtration (Crassostrea gigas) in intensive systems (sea bass farm, Dicentrarchus labrax). It can be concluded that foam fractionation coupled with aeration and water circulation is a good way to treat and recirculate wastewaters in extensive systems, but that a multiple treatment combining a retention pond, foam fractionation and microalgae-bivalve filtration, is the best solution to treat all these forms of wastes from intensive systems.