Abstract
This study investigates the feasibility of ultrasonic pretreatment for improving treatment efficiency of waste activated sludge (WAS) in microbial electrolysis cell (MEC). Results showed that at applied voltage of 0.5 V, biogas production and cathodic hydrogen recovery enhanced 3.68-fold and 2.56-fold, respectively. Due to the transformation of soluble COD accelerated by the pretreatment, the removal rates of suspended solids and volatile suspended solids were significantly enhanced by 1.38-fold and 1.48-fold, respectively. Various kinds of organics, including VFAs (volatile fatty acids), proteins and carbohydrates, could be utilized in sequence. The primary biodegradable substance in MEC was hydrophilic fraction from sludge organics and the pretreatment effectively resulted in an elevated concentration of this fraction. The 16S rRNA pyrosequencing analysis demonstrated multiple syntrophic interactions between fermentative bacteria, exoelectrogenes, and methanogenic archaea in MEC for WAS.
Highlights
There is a strong consideration toward waste activated sludge (WAS), which is massively generated by commonly used biological wastewater treatment process, as a source of renewable energy, i.e., named biomass
At day 4, the current density in the WAS microbial electrolysis cell (MEC) decreased significantly; whereas in the U-suspended solid (SS) MEC, the decrement delayed until day 9
Ultrasonic pretreatment resulted in solubilization of various organics from sludge matrix, accelerating the microbial electrohydrogenesis
Summary
There is a strong consideration toward WAS, which is massively generated by commonly used biological wastewater treatment process, as a source of renewable energy, i.e., named biomass. A mixed culture was required for achieving better performance rather than pure culture (Liu W.Z. et al, 2016) In this opinion, microbial electrolysis process could combine with fermentation process for sludge treatment. Microbial electrolysis process could combine with fermentation process for sludge treatment During this process, it is very important to reveal how the multiple groups of microorganisms work together to transform complex substrate to energy products, such as hydrogen or methane. The hypothesis that sludge utilization can be directly achieved for hydrogen production in MEC instead of sludge fermentation liquid was explored in the present study From this aspect, variations of both soluble organics and EBOM in influent and effluent from MEC were examined using hydrophilichydrophobic fractionation and EEM fluorescence spectroscopy. The microbial community structure of anode biofilm was analyzed using high-throughput 16S rRNA pyrosequencing in order to relate reactor performance with microbial function, with emphasize on the microbial behavior and interactions
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