**1. Introduction**

The need for energy source is one of the important things in human life. Fossil fuel, geothermal, water potential, and nuclear energy are some energy sources that have been commonly used. In addition to some of these energy sources, wind energy, solar radiation, ocean

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

waves, biomass, and other renewable energy sources have also been widely researched and developed as an alternative energy source. Nevertheless, until now fossil fuels are still one of the primary energy sources that cannot yet be completely replaced by other types of energy sources. The decrease in availability of fossil fuels as non-renewable energy sources is inversely proportional to the increasing population of the world. Raising awareness of the limited reserves of fossil fuel and of the need for another energy source as alternative energy source is needed. One alternative energy source that can be considered is the biomass content of sludge produced from biological wastewater treatment. Carbon compounds contained in biological sludge (bio-sludge) can be converted into energy through thermal process, biodigestion, lipid/oil extraction, or other methods that are in accordance with its characteristics [1, 2, 12, 15, 25, 34]. Therefore, the main objective of this research is to identify the prospect of several technologies to treat organic sludge in terms of mass reduction and energy recovery as a basis for feasibility study and further development. The thermal process of converting biomass to energy is also accompanied by a decomposition process of complex carbon into a simpler form of carbon compounds. So that, in this case, not only the conversion of biomass into energy, but also the mass reduction of sludge should be processed and managed to minimize the negative impacts that can be generated from the sludge generated by the wastewater treatment process [11].

required to ensure that the wastewater that flows to the treatment facility has characteristics that are in accordance with the processing capability and capacity of the existing treatment facilities. The treatment process is generally divided into several stages, among others primary treatment, secondary treatment, tertiary treatment, and other treatment options accord-

Energy Prospects of Hazardous Sludge from Wastewater Treatment Facilities

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Referring to the regulation of Republic Indonesia environment minister No. 5 year 2014 concerning wastewater quality standards, stated that each type of industry that produces wastewater from the results of its activities and conducts types of treatment activities, it is a mandatory to comply with the applicable quality standards [23]. Likewise, with centralized wastewater treatment facilities located in industrial estates, it is mandatory to comply with the applicable quality standards. One of the centralized wastewater treatment facilities in the industrial estate in Indonesia is the Jababeka's wastewater treatment facility located in Bekasi Regency, West Java. The main process in this treatment facility is a biological treatment process

As can be seen in **Figure 1**, there are several treatment stages at the Jababeka's wastewater treatment facilities. Among them are the removal stages of sand, gravel, and rough mud on the grit chamber unit. Furthermore, wastewater will flow due to gravity toward the primary settling tank unit. In this unit, suspended solids will settle, while floating material will be separated with the scum collector and then flow to the sludge treatment unit. The primary settling tank effluent is flowed to the oxidation ditch which utilizes biological process (activated sludge) to decompose pollutants contained in wastewater. This process will produce

ing to the wastewater characteristics to be treated.

equipped with other treatment process units.

**Figure 1.** Schematic flow diagram of Jababeka's wastewater treatment facilities.

Before discussing further the next section, it is necessary to clarify in advance some terms in this paper. What is meant by sewage is liquid waste (in this case, it is wastewater) that flows in the sewer [31]; so, the terms sewage and wastewater will be used interchangeably according to the context of the sentence. Sewage sludge is mud that originated from a sewer, whereas treated sewage sludge means sludge that is produced from the treatment process in wastewater treatment facilities.
