Efficient Removal of Oil, Fats and Grease from Domestic Wastewater for Water Reuse with Energy Generation as Fuel

Abstract

wastewater effluents contain oils, fats and greases which result in choking of the water distribution systems. These problems arise due to the issues like temperature differences in wastewater flow and flow channel structural differences. By using the end of pipeline cleaner production techniques, these oils and fats can be recovered and reused in the biofuel production. Water recovered after the recovery of oils and fats can also be a good resource for reuse in agricultural lands to meet demands in arid lands. In this way reliance on ground water use for agriculture can be reduced along with continuous energy generation from oil and fats recovered from domestic wastewater discharges. The advantages could be the resource recovery, recycling and reuse of problem causing oils, fats and greases as valuable fuels. The recovery of oil, fats and grease from the domestic wastewater streams as a biofuel, the biodiesel, and the generation of reusable water is investigated in thisstudy. A batch reactor system was used to study the removal of oil, fats and greases from the domestic wastewater stream (Chakri drain Rawalpindi) using basic anionic resin catalyst Amberlyst A21. The biofuel generation of the recovered oil was achieved with the macro porous acidic resin Amberlyst 15. Oil separation of 33 ± 2.08% was noted by gravity separation from the water stream after providing a retention time of 72 hours to the oily wastewater sample. Esterification reactions were then carried out at temperatures 50, 60, 70 and 75oC with varying oil to alcohol molar ratios of 1:2 to 1:3. Amberlyst 15 acidic resin catalyst percentages in the reaction mixture varied from 2, 4 and 6% by weight of oil mixture respectively. The maximum mono alkyl ester production was noted at a reaction temperature of 70oC with maximum ester yield of 91.38% at a molar ratio of 1:3, catalyst weight percentage of 6 weight % and reaction temperature and time duration of 70oC and 8 hours respectively. After performing the fractional distillation of the reaction products the ester yield was further increased to 95.75%. The COD of recovered water from oil, required to achieve NEQS of 150 mg/L, was observed at the activated carbon dose of 0.8 grams/liter after an adsorption time interval of 45 minutes, only once the oil separation was done. Moreover, parameters like water pH, alkalinity and ammonia after oil recovery and passing through activated carbon were also found meeting the NEQS. With oil recovery and conversion into biodiesel, a profit of 53.811 Million Rupees can be gained in first year and 91.479 million rupees in successive years while discharging water back to the Chakri drain for pollutant dilution and for reuse in horticulture purpose.