The anaerobic digestibility of a targeted substrate, measured as methane yield is conducted via biochemical methane potential (BMP). In this study, the batch BMP test was conducted using Automatic Methane Potential Test System (AMPTS II) for 25 days and focused on the methane production from the digestion of food waste (FW, in the form of raw and diluted) at inoculum to substrate ratio (I/S) ratio of 2:0 and under mesophilic temperature.  The results showed that solids (TS and VS) concentration reduced significantly due to the       dilution. The ultimate methane yields from the digestion of raw FW and diluted FW were 1891.91ml CH4/gVS and 1983.96 ml CH4/gVS respectively. This showed that the dilution significantly improved the methane yield. In addition, the lag phase of the methane yield curve for both BMP tests was less than one (1) day, showing the good biodegradability of FW. The kinetic methane production from laboratory data and Modified Gompertz modelling fitted well. However, the kinetic equation parameters such as Mo, Rm and l from the model were slightly lower based on the observation of the laboratory data.

Biochemical methane potential (BMP) is a standard test to assess the biogas (including methane) production from the anaerobic digestion of any organic waste. In many anaerobic digestions of sewage sludge, the inoculum to substrate ratio and mixing were variable to take into consideration for efficient performance. However, the organic content in sewage sludge varied due to the composition of the raw wastewater being treated and the treatment condition. This study is focused on the methane production from the digestion of domestic mixed sewage sludge in the batch reactor at different organic contents. Biochemical methane potential (BMP) was conducted at the inoculum to substrate ratio (I/S) ratio of 2:0, each with different organic content. On the termination day of the BMP assay, the sample from each BMP reactor was tested for pH, and alkalinity to determine the status of the anaerobic process. Results showed that the anaerobic process was stable since the pH remained in the pH range which is suitable for the anaerobic process to take place. The anaerobic process was also confirmed stabled as indicated by low value (< 0.3) of intermediate alkalinity to partial alkalinity ratio (IA/PA). The ultimate methane yield was 588.3 ml CH 4 /g VS at the organic content of 0.52 and 1244.5 ml CH 4 /g VS at the organic content of 0.68 respectively. For the organic content of 0.68, the maximum methane production rate constant was 13.97 mL CH 4 /g VS /hr. For the case of lower organic content, the maximum methane production rate constant was 6.41 mL CH 4 /g VS /hr. However, the lag phase of the methane yield curve for both organic content was less than one (1) day, showing the good biodegradability of domestic mixed sewage sludge.

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Food waste was massively disposed at landfills daily, and this method is no longer effective in managing waste due to the limited space and environmental issues. An alternative solution was explored in managing the food waste, and anaerobic digestion serve as the best solution. Food waste was digested anaerobically in a lab-scale and pilot-scale anaerobic digester. The performance of a batch pilot-scale anaerobic digestion of food waste, on the other hand, is less documented. The goal of this research is to look into a batch pilot-scale anaerobic digester for food waste, with a focus on methane potential and kinetic studies. A single-stage anaerobic digestion of food waste was carried out with an inoculum to substrate ratio (I/S) of 2.0. A variety of tests were carried out to identify the properties of the food waste and the inoculum employed. Effluent was collected daily for the monitoring process. The pH and volatile fatty acid to total alkalinity ratio (VFA/TA) were monitored daily to ensure that the anaerobic digestion process remained stable. The VFA/TA ratio suggested that the anaerobic digestion process was stable throughout the anaerobic digestion process. The methane accumulation for 26 days monitoring is 463250 mL. The ultimate methane yield of 5103.6 mL CH4/gVS was observed. The maximum removal efficiency for TS, VS, and COD in this investigation was 85.32, 94.15, and 93.52 %, showing that food waste was efficiently decomposed for biomethane conversion. The Modified Gompertz (GM) and Logistic function models were used to conduct the kinetic analysis. The results reveal that the GM model provides a higher R2 value than the logistic function model, thus the GM model is more suited in explaining the performance of the anaerobic digestion process.

Abstract. Sewage sludge, normally in form of mixed sewage sludge is treated using anaerobic digester worldwide. In Malaysia, sewage sludge was categorized as domestic sewage sludge since sewage treatment plant treats only domestic sewage. The complex organic compounds in form of carbohydrates and proteins are transformed to methane during anaerobic digestion. The characteristics of complex organic compounds in domestic mixed sewage sludge are needed to assess the energy recovery form digesting domestic mixed sewage sludge. Besides that, it is common to use anaerobic biomass from existing anaerobic digester for the new setup of the anaerobic reactor. Therefore, this study was outlined to study the characteristics of domestic mixed sewage sludge and anaerobic biomass, particularly on the complex organic compounds. The complex organic compounds measured were carbohydrates and proteins. The higher complex organic solubilisation as a result of thermal pre-treatment was proven to improve the methane production. Therefore, in this study, the impact of low thermal pre-treatment in improving the organics solubilisation was assessed too. Low thermal pre-treatment at 70 o C and 90 o C at various treatment time were applied to the domestic mixed sewage sludge. The results indicated that the domestic sewage sludge and anaerobic biomass from a full-scale anaerobic digester contained complex organic compounds; existed mostly in form of particulate as shown by the low value of soluble to total ratio. Besides that, the low thermal treatment at 70 o C and 90 o C increased the organics solubilisation. Protein solubilisation was observed exceeded 8% after being treated for 20 min at both thermal treatments. However, the impact of low thermal treatment was better at 90 o C, in which higher solubilisation was observed at longer treatment time.

Abstract. In practice, primary and secondary sludge are fed into anaerobic digestion. However, the microbial cell exists in secondary sludge are an unfavorable substrate for biodegradation. Thermal pretreatment is proved to increase the bioavailability of organic and improve the biodegradation subsequently. During low thermal pretreatment, both intracellular (within the microbial cell) and extracellular (within the polymeric network) materials were extracted. This process increases the bioavailability meaning that organic compounds are accessible to the microorganisms for their degradation. This research aims to investigate the effect of thermal pretreatment on domestic mixed sludge disintegration. Domestic mixed sludge was thermally treated at 70 0 C for various holding times. The pre-thermally treated domestic mixed sludge was measured for protein and carbohydrates following the Lowry Method, and Phenol-Sulphuric Acid Method respectively. DR 6000 UV-Vis spectrophotometer, DRB200 Reactor (digester) and COD vial (TNT plus 822) were used for COD determination, based on Reactor Digestion Method approved by USEPA. The results showed that the organic matter in domestic mixed sludge is efficiently solubilised during thermal treatment organic matter. The higher soluble yield for each monitored parameter determined in this study indicated that low thermal pretreatment improve bioavailability.

It is challenging to manage the organic fraction of municipal solid waste (OFMSW) because it is putrescible. OFMSW is dominated by food waste, and food waste is easily degradable and causes unpleasant odor at the landfill. Anaerobic digestion was preferable for food waste stabilization. However, the methane production of food waste was low. This research aims to analyze the methane yield and its kinetics from the digestion of thermally treated food waste. In preparing the thermally treated food waste, the water bath at 50°C was used and operated for two hours. The biochemical methane potential (BMP) was conducted in a batch reactor. The reactor was operated at a mesophilic temperature at inoculum to substrate ratio of 2.0. The results showed that the ultimate methane yield of thermally treated food waste increased with 630 mL CH4/g VS higher than untreated food waste. The thermal pre-treatment improved the methane production rate with an increment of 9.8%. Besides, kinetic parameters observed from Modified Gompertz modeling were found lesser than laboratory observation. Despite that, thermal pre-treatment at 50°C significantly improved the digestion of food waste.