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°C and 90°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°C and 90°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°C, in which higher solubilisation was observed at longer treatment time.
Highlights
Anaerobic digestion is a biological process to degrade the organic pollution with the existence of several types of anaerobic microorganisms, in which the biogas is produced
The lower concentration of soluble form of chemical oxygen demand (COD), carbohydrates, and proteins showed that the organics mostly existed in the form of a particulate
The present paper studied the characteristics of anaerobically digested sludge (AnDS) and DMS originated from full-scale anaerobic digester treating domestic mixed sewage sludge
Summary
Anaerobic digestion is a biological process to degrade the organic pollution with the existence of several types of anaerobic microorganisms, in which the biogas is produced. The biogas has a high calorific value and is considered as a renewable energy source [1]. The airtight tanks are used for anaerobic digestion. Many types of the organic material can be digested, except for stable woody materials. The lignin in the stable wood is hard to be degraded by the anaerobic micro-organisms lignin [1]. Substrate to anaerobic digester varies including landfill leachate, and sewage sludge [2], [3]
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