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 pretr eatment step in a platform for the treatment of liquid wastes. The aim of t he 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 characterist ics of the wastewater and the treatment methodologies were critically discu ssed. The process management was subsequently (Jul-Aug 1997) modified in or der to take advantage of the synergic power among the different liquid wast es to reduce the use of strong oxidative treatments (i.e., the Fenton proce ss) which determined, during the first research period, a large increase of the total dissolved solids and salinity in the effluent, without meaningfu l chemical oxygen demand reductions. Moreover, the N-NH4 removal was perfor med by struvite precipitation, using phosphate-rich wastewater or pure chem icals. A good indicator of the reliability of the new flow scheme was the s alinity reduction-a loss of 2800 mg/L-during the first 2 months. A larger r eduction was obtained after a further 3 months (total dissolved solids pass ed from 17 000 to 5000 mg/L). Therefore, the effluent characteristics becam e suitable for the following biological process.