The study present the feasibility of a bioelectrochemical cell (BeCC) integrated with Granular Activated Carbon (GAC) as the bacterial attachment medium in treating spent caustic wastewater. BeCC is a bioelectrochemical reactor that uses activated sludge for substrate degradation while also capable in energy recovery. Unlike the general MFC configuration, the BeCC reactor is cost effective as it was operated without a proton exchange membrane (PEM). Instead, a baffle is used to reduce the oxygen transfer to the other side of the reactor and the employment of the baffle has divide the reactor into hybrid of anoxic and aerobic conditions. Also, instead of using packed GAC, the BeCC was integrated with 10 g of suspended GAC in order to increase the surface area available for bacteria to attach. The study investigated the best operating MLSS for the system to treat spent caustic wastewater whereby the BeCC was tested at various MLSS of range within 2500 mg/L to 4000 mg/L and its performance in terms of Chemical Oxygen Demand (COD) and sulfide removal as well as it open circuit voltage (OCV) were evaluated throughout 30 days of operation. From the study, the highest COD removal of the system was 95.6% achieved at MLSS of 3500 mg/L whereas the highest sulfide removal was 87.1% achieved at MLSS of 3000 mg/L. The highest OCV was 413.7 mV achieved at MLSS of 3000 mg/L.
The study aims to treat spent caustic wastewater by using a bioelectrochemical cell (BeCC) integrated with Granular Activated Carbon (GAC) as the bacterial attachment medium. BeCC is a bioelectrochemical reactor which employs microorganisms for substrates degradation and has the capacity to produce energy simultaneously. Microbial Fuel Cell (MFC) is also known as the bioreactor that could treat wastewater while producing energy. However, the BeCC reactor in the present study is more cost effective than an MFC reactor, since the BeCC was operated without the employment of a proton exchange membrane (PEM). The reactor was operated in a hybrid of anoxic and aerobic conditions whereby a baffle is used as the separator to minimize the oxygen transfer from the cathodic to the anodic side of the reactor. For enhancement of the BeCC performance, 10 g of suspended GAC was added into the BeCC reactor. The use of the suspended GAC is to allow higher surface area available for bacteria attachment. The study determined the best operating solid retention time (SRT) and organic loading rate (OLR) of BeCC in treating spent caustic wastewater and its performance throughout 30 days of operation was evaluated based on its Chemical Oxygen Demand (COD) removal and open circuit voltage (OCV). For SRT study, BeCC was tested at various SRT of range within 10 to 30 days whereas for OLR study, BeCC was tested at various OLR of range within 700 to 900 mg COD/L.d. From the study, the highest COD removal were 94.17% and 92.7% achieved at SRT of 30 days and OLR of 700 mg COD/L.d respectively. Whereas for energy recovery, the highest OCV were 336.4 mV and 362 mV achieved at SRT of 20 days and OLR of 800 mg COD/L.d respectively. Biochemical bacteria identification test was also carried out to identify the bacteria morphology attached on GAC in the BeCC at SRT of 20 days with 700 mg COD/L.d of OLR and it is found that Klebsiella Oxytoca was the dominant bacteria attached on the GAC.
In this work, a comparative analysis of the gasification process of sawdust (SW) and sawdust pellet (SWP) utilizing a downdraft gasifier was performed. The gasification was conducted in a research-scale fixed-bed gasifier applying air as an oxidizing agent. The comparison between the raw (sawdust, SW) and treated biomass (sawdust pellet, SWP) was investigated for the syngas composition and gasification performance at the fixed condition of gasification temperature at 750 °C and equivalence ratio of 0.25. The gasification performance was tabulated in the form of heating value of the syngas (HHVsyngas), gasification efficiency (ηGE) and carbon conversion efficiency (ηCCE). It was found out that SWP produced the highest H2 and the lowest CO2. Furthermore, SWP also present the better gasification performance than SW. SWP achieved the high HHVsyngas, ηGE, and ηCCE at 4.2152 MJ/Nm3, 24% and 37%, respectively.
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