Abstract
Partially neutralized aluminium sulphate (PNAS) has been tested in laboratory and in full‐scale experiments. Better removal of colour, permanganate COD and lower residual aluminium concentrations were achieved in both tests. The PNAS use also enabled to shut down the raw water prealkalinization. Results of two years operational use of PNAS at two small treatment plants are also evaluated. Partially neutralized aluminium sulphate seems to be a good alternative to alum in treatment of low alkalinity waters.