Enhancing methane production of co-digested food waste with granular activated carbon coated with nano zero-valent iron in an anaerobic digester.

Anaerobic digestion (AD) possesses dual benefits of waste treatment and energy generation. The use of conductive additives in AD matrix has potential to improve process yield. Hence, the study aimed to investigate a thermophilic AD (TAD) inserted by granular activated carbon coated with nano zero-valent iron (GAC/nZVI) in the matrix and was operated for mono-digestion and co-digestion of cow manure with food wastes (rice and bread) to check the bioprocess improvement. The results were compared with the control TAD without conductive additives. Biogas production increased by 11 folds upon using GAC/nZVI addition compared to the control TAD. Moreover, the addition of GAC/nZVI increased the methane in biogas by 20.7 folds compared to control one. With GAC/nZVI, the maximum COD removal of 78.29% and 85.21% were noticed for co-digestion and mono digestion, respectively. Such improvement of TAD performance was due to easy bacterial communication and electron exchange through the conductive particles.

Effect of internal and external resistances on desalination in microbial desalination cell.

The green and cost-effective nature of the microbial desalination cell (MDC) make it a promising alternative for future sustainable desalination. However, MDC suffers from a low desalination rate that inhibits it being commercialized. External resistance (Rext) is one of the factors that significantly affect the desalination rate in MDCs, which is still under debate. This research, for the first time, investigated the impact of Rext on MDCs with different internal resistance (Rint) of the system to discover the optimal range of Rext for efficient MDC performance. The results showed that the effect of Rext on desalination rate (2.52 mg/h) was quite low when the Rint of MDC was high (200 Ω). However, operating the MDC with a low Rint (67 Ω) significantly improved the desalination rate (9.85 mg/h) and current generation. When MDC was operated with a low Rint the effect of variable Rext on desalination and current generation was noticeable. Therefore, low Rint (67 Ω) MDC was used to select the optimum Rext when the optimal range was found to be Rext ≪ Rint, Rext < Rint, Rext ≈ Rint (ranging from 1-69 Ω) to achieve the highest desalination rates (10.41-8.59 mg/h). The results showed the superior effect of Rint on desalination rate before selecting the optimal range of Rext in the outer circuit.