Part B: Sludge sewage pre-treatment and codigestion Technical Note 2 – Contributions about sewage sludge pre-treatment techniques

Abstract

Anaerobic digestion is a widely used and well-established technology for sewage treatment. Derived from this practice, the great advantage of enabling the biogas production, clean and sustainable energy, through sludge hydrolysis. However, one of the main limitations of this technology is the resistance to degradation of microbial cells present in this sludge. These cells often contain complex carbohydrates resistant to biodegradation, making the hydrolysis step slower compared to the other steps. In this sense, a series of technologies and methods are available for the pre-treatment of sludge, aiming to overcome these difficulties. Technical aspects and qualitative comparison of these techniques, discussed in this work, show that, in order to select the best pre-treatment technology, important variables such as availability of operational labor and sludge constitution should be taken into account. Some disadvantages associated with these technologies were also identified, such as high energy consumption and excessive degradation with biodegradable substrate loss. Thus, the authors conclude that the mixture of processes and the use of alternative energy sources are potential ways to make pretreatment techniques viable. However, the use of alternative energy for this purpose is still in initial stages, and it is necessary to go deeper into the subject in order to consolidate it in the near future.