Characterization of Sludge from the Wastewater-treatment Plant of a Refinery

In this study, characterization of filtrated cake of sludge drying section from a petroleum refinery wastewater treatment plant in Melaka was carried out with the objective to analyze its chemical, physical and fuel characteristics. Proximate analysis, ultimate analysis and higher heating value (HHV) are very important in chemical and fuel characterization. Dielectric properties and density test were also carried out to determine it suitability as microwave thermal treatment candidate. The density was found higher compared to those reported in literature. According to proximate analysis, moisture content of sludge is very high (75.3 wt%) which would decrease the heating value. However, the higher heating value (HHV) of 20.5 MJ/kg of sludge in this study is higher than HHV in other petroleum sludge probably due to the hydrocarbon content in the sludge. It is also found that volatile matter is high at 58.6 wt% where it can be converted into valuable products via material decomposition. Relatively high content of oxygen element (39.7 wt%) contributed to the low value of HHV and possible highly oxygenated liquid product during pyrolysis. Metal content analysis revealed high content of Fe (1,850 ppm) and also significant amount of Al, Mg, Zn and Na which categorize the waste as schedule waste. The values of dielectric constant were found to follow the trend that of water because of its high moisture content at 1.24 to 20 GHz. However, the dielectric loss trend is opposite to the water at frequency below 5.0 GHz. It was found that the value of dielectric constants at frequency of 2.45 GHz, which is common in industrial processing, were 50.8 and 2.3 for wet sludge and dried sludge, respectively. While for dielectric loss, its values were 15.7 and 0.1, respectively. Hence, good penetration can be achieved by microwave energy during microwave thermal treatment process to allow material decomposition but the energy conversion will be occur fairly.