THE INFLUENCE OF FIBERS ON THE STRUCTURE OF THERMALLY DRIED SLUDGE PRODUCT

There appears to be a limited experience world-wide in the application of thermal drying technology to processing raw undigested sludge. Thi s limited experience has shown that the products from raw sludge proce ssing have a much lower bulk density than those from digested sludge. The apparent reason for this phenomenon demonstrated by this work, is the high concentration of fibres in the raw undigested sludge. Differe nt sludges show varying degrees of fibre concentration with a decrease in fibre content as the proportion of secondary sludge increases. The relationship between the bulk density of the product and the fibre co ntent are given and this shows that as the fibre content increases the bulk density of the product will fall. It is recommended that a compa ction/pelletisation stage is included in the process stream for high f ibre sludges. Copyright (C) 1996 IAWQ. Published by Elsevier Science L td