q &a forum, page-11

CaS may be suitable for treating wastewater streams, but these are liquid. The Hunter River dredging will produce mud in suspension with most of the toxic metals already precipitated/adsorbed in with the mud. Adding CaS probably wouldn't make the mud any less toxic and it wouldn't produce a separate precipitate cake for treatment via the Intec process.

However there still may be opportunity for Intec consequent to the dredging process.

My understanding is that the dredged mud would be used to build up land presumably using some kind of bund retaining system. Drainage works would presumably be incorporated into this built up land and the effluent from these drains could be suitable for cleanup using the Intec CaS system.

Some of the areas to be dredged contain high levels of toxic contamination; sufficient to require silt curtains to avoid contaminating the waterway. This highly toxic sediment may require additional containment and may be an additional source of toxic effluent.

Bottom muds in estuaries are likely to present as anoxic environments. Under these conditions, sulphate reduces to sulphide and metal sulphides precipitate. When these muds are exposed to air, the sulphides may oxidize to sulphuric acid. On the North Coast of NSW this sequence of events occurs when swamps are drained for agriculture. The Hunter River dredging may have the same outcome. The acid produced when the mud is exposed to air would very likely leach toxic metals into the drainage. Intec may be in a position to use this toxic drainage to advantage.