Enhancement of Sludge Dewatering: A look at Polymer Maturation and Shear Optimization
The expected growth in global population and overall development of living standards will inevitably have an impact on wastewater treatment infrastructure. This will in turn put pressure on local wastewater treatment plants to handle greater throughput at a higher efficiency. Sludge treatment is one of the components of a treatment plant that will need to be enhanced as various elements rely heavily on operator empirical experience, or tests that reveal information about sludge after the fact.
... ge after the fact. For example, crystalline polymers are often used for coagulation and flocculation of solids, however, the preparation methodology that is currently employed is typically based on operator judgement. Furthermore, the attempts that have been made to quantify polymer quality in terms of its optimal maturation time, with the use of viscosity and electrical conductivity, have not yielded conclusive results to determine optimal polymer age for application to sludge. In addition, the laboratory tests used measure sludge characteristics (such as total solids) are time consuming and by the time results are generated, sludge characteristics have likely changed. The first phase of this study was aimed at developing a new methodology to determine the optimal polymer maturation time which would yield the highest quality of dewatering. With the use of spectrophotometry, the optimal maturation time was estimated and corroborated by spiking anaerobically digested sludge with polymers of different age. A significant difference (p<0.05) was found between the filtration volume of sludge spiked with polymer that was aged for three hours compared to six hours. In addition, the spectrophotometer had the sensitivity to detect changes to polymer temperature, pH, chlorine content, and mixing method. Temperature, pH, and mixing regime had the greatest influence on maturation. In the second phase of the study ii the rheological properties of conditioned sludge were used to determine a relationship between the degree of shear and the resulting sludge dewaterability. The rheometer used for measuring sludge network strength was also able to capture the optimal polymer dose range. iii