The reduction of total nitrogenous output remains a significant challenge in the pond culture of prawns. The majority of total nitrogen (TN) output from the Australian prawn industry is organic nitrogen, of which microalgae assimilate a large proportion. In response to the industry’s need to remove or reduce microalgae and TN from large quantities of release water, our team proposes a project that would investigate the use of electro-coagulation (EC) technology to remove microalgae and TN from settlement pond discharge. EC is a highly effective electrochemical approach to wastewater treatment, and has been successfully used to assist in the removal of both organic and inorganic contaminants from wastewater (Moussa et al., 2017). This technology works by applying an electrical current through the water, destabilizing/neutralizing the repulsive forces that keep particles suspended, causing these particles to form larger particles that settle for easier separation from water. This method of coagulation has a significant advantage over chemical coagulation/flocculation: coagulants are formed in-situ by electrolytic oxidation of an anode, and therefore additional chemicals, metal salts or polyelectrolytes do not need to be added to the system. This results in less sludge generation as a bi-product of the filtration process (Moussa et al., 2017). NaturalShrimp has spent many years developing, patenting, and commercializing the EC technology for use specifically for aquaculture that not only helps with coagulation but also removes pathogens and ammonia.
The proposed project will be undertaken by Nautilus Collaboration (primary investigators: C van Rijn and C Huynh), Natural Aquatic Solutions (technology supplier – Rep: Tom Untermeyer) and Fresh By Design (installation and maintenance – Lachlan Bassett). The proprietary EC technology developed by Natural Aquatic Solutions has the capacity to treat around 20.5 m3/hr of water. The electrical current passing between the plates removes chlorine from the saltwater as it passes between the plates. The chlorine then combines with the ammonia to form chloramine which is then removed by a carbon filter downstream from the EC. The current is manually adjusted as the ammonia changes to effectively remove the ammonia in one pass through the EC. The ammonia removed by the EC prevents it from further converting to nitrite or nitrate. This controls the level of bacteria, removes ammonia, greatly reduces nitrate output and produces an anti-oxidative water chemistry beneficial to the health of the receiving ecosystem (T Untermeyer, pers. comm.).