Energy production from rubber processing effluents through biomethanation

Abstract

The generation and disposal of large quantities of biodegradable wastes such as Rubber Processing Effluents (RPE) without adequate treatment result in significant environmental pollution. Some of the waste streams are treated by conventional means like aeration, which is energy intensive and expensive. In this context, anaerobic digestion offers potential energy savings and is a more stable process for medium and high strength organic effluents. Apart from treating the wastewater, the methane produced from the anaerobic system can be recovered which results in saving the global environment by reducing the use of fossil fuels. The study was aimed at assessing the pollution hazard caused by rubber processing units, understanding the biomethanation characteristics of RPE and to evaluate the performance of locally available agricultural wastes viz. coconut shell, rubber seed shell etc. as packing media in high rate anaerobic bioreactors. Two types of effluent were identified, one which is generated during the production of rubber sheet (RPE 1) and other one from the centrifuge plants (RPE 2). It was revealed that the RPE had a low pH and high BOD and COD. This reveals the extend of variation of characteristics from the standards. The batch digestion studies proved that RPE1 is suitable for biomethanation whereas RPE 2 is not suitable. The specific gas production of RPE1 found to be 6665.3 ml/l. Batch digestion studies with different media viz. coconut shell, rubber seed inner shell, and rubber seed outer shell reveals that any media can be used in the high rate bioreactor considering the physical characteristics and availability. Also, the amount of inoculum added to start the biomethanation did not showed any remarkable changes in the gas production. The pollution caused by RPE can be effectively reduced by anaerobic treatment with the added advantage of energy production. This can be further used to ensure better management of energy in the processing plants.