Enhancing the dewaterability and amenability of sludge for subsequent stabilization processes by using organic waste solids as conditioners

Dual-material conditioning of sludge was evaluated using a chemical conditi oner (either alum or ferric chloride), followed by a physical conditioner ( either wood chips or wheat dregs). The combined effects of the conditioners on the dewaterability of the sludge with vacuum filtration and the amenabi lity of the resulting sludge cake for subsequent stabilization processes we re investigated. Results showed that the specific resistance of the conditi oned sludge was effectively reduced when the dose of wood chips or wheat dr egs was increased in each dual-material combination. From the results of an alysis of solids in the cake, the filtered sludge cake with either wood chi ps or wheat dregs conditioning in higher dosage resulted in lower moisture and higher volatile combustible solids content. Accordingly, sludge conditi oning with these two materials substantially increased the heating value of the dewatered sludge. In addition, wood chips are the most widely used bul king agent, and wheat dregs could be suitable to act as amendments in sludg e composting. These results indicate that these two organic waste solids co uld replace a significant portion of the chemicals now used for sludge cond itioning to improve the dewaterability of sludge and the amenability of the resulting sludge cake for incineration and composting processes.