OPTIMISING THE SUSTAINABILITY OF
wastewater treatment
Alissa Pallagrosi, Andrea Carotti, David Lehmann and Joseph Lehmann, Saipem, look at the development of electrochemical technology designed to remove ammonia and urea contaminants from fertilizer plant process wastewater.
T
he abatement of emissions and implementation of sustainable processes are key targets in redefining the world economy, and are significant drivers of continuous innovation. Wastewater generated at large-scale complexes should ideally be recycled and re-used or, when that is not feasible, treated so that it has a near-zero environmental impact. One area of particular concern is wastewater that is rich in nitrogen eluates. This is typical of effluent from many industrial and municipal plants, with nitrogenous fertilizer plants being a prime example. Such wastewater is associated with severe environmental impacts, including eutrophication of surface waters, toxic phenomena and decline in biodiversity. Ammonia is the main contaminant of concern, being extremely widespread and toxic at even low concentrations. The treatment technologies that are currently available are complex, costly and unreliable; as a result nitrogen-rich wastewater remains a major ‘pain point’ of the fertilizer and similar industries. In response to the sustainability challenge and to the increasingly urgent need for effective and economically feasible solutions, Saipem S.p.A. sought to find a solution to the issue of nitrogen-rich wastewater. Particular attention was paid to novel electrochemical technologies, in line with the ‘Emerging wastewater treatment techniques’ defined in the 2016 BAT review.1 In 2017, following a rigorous evaluation process, the company established a collaboration with Purammon Ltd., a technology start-up specialising in electrochemical technologies and processes, to commercialise a new electrochemical technology for the combined removal of ammonia and urea contaminants from process wastewater: SPELL. The technology quickly and cost-effectively transforms ammonia and/or urea into their harmless elemental components (e.g. gaseous nitrogen) with no sludge or other byproducts. The technology has been commercially implemented (Figure 1) and further engineered up to a full-scale package application, capable of satisfying all applicable international industrial standards and the most stringent environmental requirements. It is simple, modular, robust and stable under volatile operating conditions. The SPELL technology is based on an electrolytic reactor packed with electrodes coated with special catalysts that selectively react with nitrogen molecules when an electrical current is applied. These reactions continuously remove the contaminants as the wastewater flows through the reactor. An illustration of a typical application of the system for direct removal of ammonia from the wastewater of fertilizer plants is presented in Figure 2.
44
