Disintegration of Wastewater Activated Sludge (WAS) for Improved Biogas Production

Abstract

Due to rapid urbanization, the number of wastewater treatment plants (WWTP) has increased, and so has the associated waste generated by them. Sustainable management of this waste can lead to the creation of energy-rich biogas via fermentation processes. This review presents recent advances in the anaerobic digestion processes that have led to greater biogas production. Disintegration techniques for enhancing the fermentation of waste activated sludge can be apportioned into biological, physical and chemical means, which are included in this review; they were mainly compared and contrasted in terms of the ensuing biogas yield. It was found that ultrasonic- and microwave-assisted disintegration provides the highest biogas yield (>500%) although they tend to be the most energy demanding processes (>10,000 kJ kg−1 total solids).

Performance and Microbial Community Dynamics in Anaerobic Digestion of Waste Activated Sludge: Impact of Immigration

“…The CH 4 yield generally decreased as the HRT decreased from 25 to 11.5 d (Figure 2b); this result suggests that the higher CH 4 production rate at shorter HRTs was due to increased substrate input rate to the bioreactors. This observation has been reported in previous literature [35][36][37][38]; use of a pretreatment [15,29] or a co-substrate [16,39] can increase CH 4 productivity. However, a conventional process (WAS digestion without pretreatment) was used in this study to achieve the objective of investigating microbial community dynamics for AD of WAS.…”

“…AD of sludge sometimes involves pretreatment of the substrate [15]. However, the pretreatment requires extensive use of chemicals, heat, electricity, or some combination of these, so its application is limited.…”

The Future Agricultural Biogas Plant in Germany: A Vision

“…Pretreatment technologies for positive effects on rheology, increased degradability and gas production, and a reduction of the necessary retention time will become increasingly important. There is a multitude of pretreatment techniques decomposing the biomass physically (mechanical, thermal, baric, ultrasound, microwave), chemically (acid, alkali) or biologically (composting, ensiling, enzymes, fungi) [148,154,[156][157][158]. Mechanical and enzymatic disintegration methods, in particular, have largely evolved within recent years, but further research is required to identify the most effective pretreatment techniques for different types of biomass, to upscale them from lab to pilot to full scale and to consider net effects on energy yield, greenhouse gas emissions and profitability.…”

Combined freezing-thawing pretreatment and microbial electrolysis cell for enhancement of highly concentrated organics degradation from dewatered sludge

“…One way to increase the hydrolysis rate, as stated, was introducing the pretreatment method. To date plenty of studies focused on the pretreatment to enhance the digestion performance [8][9][10], few researches were reported for the influence of the pretreatment method on the MEC in terms of sludge [11,12]. Our previous study [12] demonstrated the efficiency of alkaline pretreatment for DS as this process affected soluble organic matter content and microbial community structures during electrogenesis.…”