Optimization of the use of polyelectrolytes for dewatering industrial sludges of various origins

 Four different industrial slurries were flocculated with polymeric flocculating agents (port sediment, sewage sludge, sugar beet washings and an aluminum hydroxide suspension). The quantities of flocculating agent employed were optimized with the aid of a patented, portable flocculation and dewatering apparatus. Using sewage sludge as an example, it was possible to arrive at predictions for particular doses of flocculating by means of a combined method of dewatering experiments and electrokinetical measurements. The results of monoflocculation and dual flocculation made it possible to deduce that there are similarities in the flocculation and dewatering behavior of slurries with comparable parameters. Comparison of the sediment particles and the polymer coils revealed a size ratio of 60:1, with the former being the larger. This was then used to devise modifications to the patch charge model and the bridging model as a function of the molar mass of the flocculating agent. The modifications were found to agree well with the experimental findings and the structural conceptions of macromolecular substances. Received: 26 July 1996 Accepted: 29 August 1996