Experimental investigation of a new process for treatment and valorisation of pot ale wastewaters

This study investigated an innovative process for the treatment and valorisation of pot ale wastewater. The first phase was to balance the pH to precipitate nitrogen, phosphorus and magnesium, recovering them as fertiliser, the second phase investigated the evaporation of water, reducing the volume of liquid to be transported to an anaerobic digester. In the pH balancing phase we investigated the effect of the final pH, in the range 8–11, on the removal of calcium, magnesium, ammonia, phosphorus and copper. We observed that for all the species most of the precipitation occurred when pH was increased from 8 to 9. By pH balancing, a removal from the liquid phase of up to 65% of ammonia and 60% of total phosphorus was obtained. Calcium and magnesium also precipitated from the liquid phase, giving solids with the following composition, calculated from liquid phase measurements: 24–27% magnesium, 4–5% nitrogen, 16–18% phosphorus. We investigated the evaporation process at pH 6 and 10 and at atmospheric pressure and under vacuum. The results showed that only a few % of the COD evaporates, indicating very little loss of organic substance for anaerobic digestion. Mass balances for this process in a medium-size whisky distillery were also carried out.