Optimization of Chemical and Physical Pretreatments in a Platform for the Treatment of Liquid Industrial Wastes

The paper presents the results of management of the chemical−physical pretreatment step in a platform for the treatment of liquid wastes. The aim of the work was to optimize the organization of the flow scheme to achieve the best performances in the chemical−physical pretreatment step. Starting from the initial situation (Jan−Apr 1997), the types, amounts, and characteristics of the wastewater and the treatment methodologies were critically discussed. The process management was subsequently (Jul−Aug 1997) modified in order to take advantage of the synergic power among the different liquid wastes to reduce the use of strong oxidative treatments (i.e., the Fenton process) which determined, during the first research period, a large increase of the total dissolved solids and salinity in the effluent, without meaningful chemical oxygen demand reductions. Moreover, the N−NH<INF>4</INF> removal was performed by struvite precipitation, using phosphate-rich wastewater or pure chemicals. A good indicator of the reliability of the new flow scheme was the salinity reduction&sbd;a loss of 2800 mg/L&sbd;during the first 2 months. A larger reduction was obtained after a further 3 months (total dissolved solids passed from 17 000 to 5000 mg/L). Therefore, the effluent characteristics became suitable for the following biological process.