The cooler column base clogged inside a chemical plant producing titanium dioxide (TiO2) and sulphuric acid; due to depressurisation and via the condenser, a solution of titanium oxide in the 20% sulphuric acid composing the hydrolysate polluted the site’s industrial water circuit. The pH and visual appearance of the industrial water caught the operator’s attention. This water circuit was drained, generating a 65cu.m discharge of hydrolysate diluted in 10,000cu.m of effluent. In order to limit production of this hydrolysate, the operator shut down as many machines as possible, activated a 200 m3/h pumping operation on the facility’s collection basin and organised the lorry-based pumping of cooling basin effluent. Despite these remedial measures, the site’s effluent treatment capacities were surpassed, causing discharge into the natural environment of the residual water loaded with iron and titanium (in amounts of 330 g and 35 g, respectively, over 2 days). Moreover, after failing to drain the column initially responsible for the accident, the operator decided to siphon plant equipment. While preparing for this intervention, the column base suddenly became unblocked, triggering a sprinkling of hydrolysate, via the lower receptacle that had been opened as part of the operating protocol, onto 2 technicians working on a scaffold. With serious eyes burns, both had to be hospitalised. Property damage inside the facility was evaluated at €500,000. To lower the probability of repeating this type of accident, various measures were adopted, namely the modification of the alarm threshold setting on cooling water pH; the installation of a 2nd drainage valve at the column base; drafting of a specific procedure detailing the shutdown, control and restart of the cooler by depressurisation; scheduling of monthly inspections on the column base.