Waste activated sludge in China are mostly subjected to dewatering process before final disposal without stabilization. This study investigated the feasibility of organics degradation and H production from non-stabilized dewatered sludge (DS) by microbial electrolysis cells (MECs). Alkaline pretreatment was used to disintegrate sludge matrix and solubilize organic matters in DS. Then, the treatment performance of DS supernatant in a single-chamber MEC at various applied voltages was investigated. The COD (chemical oxygen demand) removal rate increased with increasing voltage, which ranged from 26.35 to 44.92% at 0.5-0.9 V. The average coulombic efficiency was 75.6%, while the cathodic hydrogen recovery was not satisfied (15.56-20.05%) with H production rates of 0.027-0.038 m H/(m day). The reasons could be ascribed to the complexity of the substrate, H loss, and the confinement of configuration in scale-up. The organic matter degradation was influenced by the composition of DS. The carbohydrates could be readily used; meanwhile, the major component of the DS supernatant, i.e. proteins, was difficult to be utilized, which resulted from the low biodegradability of the transphilic fractions during the MEC operation.

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.

2020) Combined freezing-thawing pretreatment and microbial electrolysis cell for enhancement of highly concentrated organics degradation from dewatered sludge, Bioengineered, 11:1, 301-310, ABSTRACTThe influence of freezing-thawing (F/T) pretreatment on the degradation of highly concentrated organic matters from dewatered sludge (DS) in microbial electrolysis cell (MEC) was investigated in this study. Extended freezing disintegrated the DS matrix and resulted in accelerated hydrolysis rate. The biogas production and stabilization were increased due to the pretreatment by 25-70% of H 2 production rate and 17.8-33.8% of COD reduction rate, respectively. Fourier transform infrared spectroscopy analysis indicated that the pretreatment was unable to alter the bioelectrochemical reactions except for accelerating degradation rate. Excitation and emission matrix (EEM) spectra showed that aromatic protein and soluble microbial products (SMPs)like materials in DS were increasingly solubilized by the pretreatment and significantly removed during electrogenesis. The F/T-pretreated DS favored the enrichment of exoelectrogens in MEC. ARTICLE HISTORY