T. Rauckyte-Żak, S. Żak
University of Science and Technology, Faculty of Chemical Technology and Engineering, Bydgoszcz, PL

Part 1. Characteristics of sludges from one-stage pretreatment

Manufacturing of construction chemicals is bound to generating process wastewaters which structure of pollutants load is determined by composition parameters of the final products, however repeatedly diluted, which is the result of the of aqueous cleaning of wash appliances and manufacturing surfaces. One-stage physicochemical pretreatment of industrial wastewaters originating from construction chemicals manufacturing with the use of coagulation methods mainly leads to the removal of dispersed phases – colloids and suspensions. In case of obtaining the final reaction concerning precipitation of hydroxides and/ or sparingly soluble salts, i.e. of heavy metals present in wastewaters with the present anions, such pollutions can be effectively removed in the form of the concentrated sediment phase. The aim of this part of the research was the risk assessment based on fractional composition of the selected heavy metals and TCLP leaching procedure tests performed on sludges dewatered gravitationally or on the pressurised chamber filter press for sludges generated during one – stage physicochemical pretreatment of process wastewaters. The described sludges were generated on three pretreatment installations of similar configuration in full technological scale, which were worked out and implemented to industrial practices in order to physicochemically pretreat the wastewaters from construction chemicals manufacturing, mainly water borne paints and silicone facade plasters for concrete constructions and interiors, adhesive mortars for tiles, ceramic tiles and milled rock tiles, protective and decorative finishing plasters, plaster and gypsum finishes, self-levelling concrete and also jointing compounds and sealing coatings. In case of ‘water-free’ samples of dehydrated sludges obtained by application of iron coagulant of category PIX® and/or the alkaline ones of category PAX®, TCLP leaching procedure and the risk assessment were carried out with the application of RAC code. It was found that the gravitationally or pressure dewatered sludges present low risk regarding Cd, Cr, Cu, Ni, Mn, Pb and Zn. In accordance with TCLP classification, the investigated wastewaters were classified as non-toxic.

Keywords: sludges from construction chemicals manufacturing, sludges from one-stage physicochemical pretreatment, TCLP test, risk assessment code (RAC).