(380f) Identification of the Most Appropriate Method to Use Sewage Sludge As a Source of Alternative Energy

Y.PLIEGO-BRAVO, M.VERGARA-HERNÁNDEZ, M.E.GARCÍA- REYES,  G. URREA-GARCÍA

INSTITUTO TECNOLÓGICO DE ORIZABA, ORIZABA, VERACRUZ, MÉXICO.

ypliego2002@gmail.com;  marverher@hotmail.com; galourrea@hotmail.com; mgarcía@itorizaba.edu.mx

 key words:   SEWAGE SLUDGE,  ALTERNATIVE ENERGY

                                                    Introduction                

The generation of sewage sludge in Mexico has increased over the past 10 years, making more difficult to find places to discard them. Over 40% of the cost of wastewater treatment corresponds to the application of depurification processes and the disposal of the generated sludge. One of the issues in the treatment of sewage sludge is their chemical composition and especially the presence of heavy metals. The concentration of heavy metals and toxic elements of biological origin may cause the sludge to be unsuitable for certain uses. Therefore further processing and special precautions need to be applied (Mahamud, 1996).

Recently, research efforts have been channeled to the potential use of biosolids as an alternative fuel. Biosolids are those compounds of organic nature that are generated as a residual after a biological or industrial process, such as sludge from the food industry, paper industry, sugar cane  or wastewater treatment plants.

To take advantage of the chemical value of sewage sludge these can be used as raw material for second-generation processes, primarily focused on the recovery of organic content, reducing the risks of spontaneous combustion, pests, odors and leach (Ramirez, 2007).

Some studies claim that wastewater contains ten times the energy needed for its own treatment and that it is technically feasible to recover energy from sewage sludge. Sewage sludge can generate renewable energy, which may be used directly in the same process, reducing the dependence on conventional energy sources.

The purpose of studies of this nature is to identify the thermochemical properties of sewage sludge and thereby take advantage of these properties in a process of alternative energy generation, which contributes to solve the worldwide energy crisis.

The objective of this research was to characterize biologically, physically, chemically and thermochemically a particular sewage sludge originated from urban and industrial stream, and its potential as source of alternative energy.

Methodology

The sewage sludge studied in this work was obtained from a water treatment plant of urban and industrial wastewater deposit. This deposit serves 11 municipalities and 6 industries, which discharge their wastewaters into a collector of approximately 30 Km in length to finally reach the floor where it is treated by means of physical and biological processes. Sewage sludge generated from the wastewater treatment plant of Ixtaczoquitlan, Veracruz, Mexico were collected in a receiving tank and are transported to the laboratory.

The methodology consisted of the proximate and ultimate characterization, as well as microbiological analysis to ascertain the potential application of the sludge. Additionally the thermochemical characterization aided in the identification of the most appropriate process for the recovery of the energy contained in the studied sewage sludge.

Table 1 shows the evaluated parameters, the units and the standardized methods used for the characterization of the sewage sludge.

Table 1 Parameters evaluated in the sludge.

Conclusions

Certain methods of wastewater treatment and disposal are not entirely satisfactory. Therefore, it is important to develop a technology for adequate treatment of sewage sludge in order to reduce the environmental problem. For that reason, it is important to identify the properties of the sewage sludge, since will reveal the best method to take advantage of the energy content of these materials.

In conclusion, the most appropriate method to maximize the energy recovery for the studied sewage sludge resulted from urban and industrial wastewater sludge was hydrothermal processing.

References

1. Mahamud L. M., Gutiérrez L. A. y Sastre A. H. (1996), “Biosólidos generados en la depuración de aguas (I): Planteamiento del problema”, Universidad de Oviedo.
2. Moeller G. (1997) “Biological Treatment of Municipal Sludge”. Biotechnology for Water Use and Conservation The Mexico 96 Workshop, OECD, Cedex, París, Francia.
3. Ramírez M. C, Larrubia M. A, Herrera M. C., Guerrero P. y Malpartida I., (2007) “Valorización energética de biosólidos. Algunos aspectos económicos y ambientales en la EDAR Guadalhorce (Málaga)”, Universidad de Málaga. Facultad de Ciencias. Departamento de Ingeniería Química.
4. Turovskiy Izrail, S. Mathai, P. K. (2006) “Wastewater sludge processing”, Wiley-Interscience.
5. NOM-004-SEMARNAT-2002, “Protección ambiental.- Lodos y biosólidos.- Especificaciones y límites máximos permisibles de contaminantes para su aprovechamiento y disposición final”.
6. NOM-021-RECNAT-2000, “Que establece las especificaciones de fertilidad, salinidad y clasificación de suelos. Estudios, muestreo y análisis”.