Recovery of Phosphorous from Sewage Sludge Ash Prior to Utilization as Secondary Resource in Concrete and Bricks

Sewage sludge ash (SSA), which today is residual waste, can be separated into two resources, phosphorous and a particulate material for use in production of concrete or brick, by electrodialytic separation (EDS). Three SSAs from different sewage sludge mono-incineration plants were included in this investigation. Overall they had similar characteristics, but still the differences meant that the EDS process needs optimization for each ash type. Under the same experimental conditions, 80% P was recovered from two of the SSAs whereas only 65% was recovered from the third SSA. After EDS, the investigation points at a decrease in Ca and P may be beneficial if using the SSA-EDS in concrete. The investigation also showed that the investigated SSAs had high Fe contents, which may be problematic if used in brick production. In conclusion, the investigation points at a potential for SSA to be considered as secondary resource in the construction materials after EDS.