Production of biodiesel and water conservation through conversion of free fatty acids from a domestic wastewater drain

ABSTRACT

Wastewater discharge from restaurants, hotels, household kitchens, confectionaries, meat, fruits, and vegetable processing units contain free fatty acids (FFAs) from fats, oils, and greases (FOG). These FFAs are one of the major causes of sewer overflows and blockages that cause health and environmental issues. This study has investigated the use of sewer wastewater as a source of lipids for the production of alkyl esters (Biodiesel) and provides a characterization of the resulting processed water. Amberlyst A21 basic resin in a column reactor was used to recover the FFAs by adsorption from an oily layer collected from the domestic wastewater drain (Chakri drain, Rawalpindi, Pakistan) having a 33.0 ± 2.08% oily fraction with 59.7 ± 1.1% FFAs. The recovered ethanol washed FFAs from the Amberlyst A21 surface were then turned into Fatty Acid Ethyl Esters (FAEEs) in the presence of an acidic resin catalyst Amberlyst 15. The esterification reaction was studied at temperatures 50, 60, and 70°C, molar ratios of 1:2 to 1:3, acidic resin weight % of 2 to 6, and reaction time of 2 to 8 hr, respectively. A maximum FFAs conversion into esters of 91.38 ± 1.13% was noted at an esterification temperature of 70°C, molar ratio of 1:3, acidic resin weight of 6%, and a reaction time of 8 h. The fractional distillation of the esterified reaction product at 100°C improved the ester content in the reaction mixture up to 96.6 ± 0.18%, with a distilled biodiesel yield of 95.52 ± 0.21%. The collected top oily layer from sewer drain wastewater was found to have a density 947.31 kg/m³, kinematic viscosity 32.69 mm²/sec, flash point 283°C, and LHV and HHV of 26 and 28 MJ/kg, respectively, while for the produced biodiesel the density was 886 kg/m³, kinematic viscosity 4.3 mm²/sec, flash point 137°C, and LHV and HHV of 39 and 41 MJ/kg was noted, respectively. Only oily layer free wastewater after passing through PAC was found to meet Pakistan NEQS, with COD <150 mg/L, pH 6–8, Alkalinity <1000 mg/L, and Ammonia-nitrogen <40 mg/L. For every 1000 gallons of domestic sewer drain wastewater treated per 8 h work shift or 3 work shifts in a day with FFAs recovered and their conversion into biodiesel, a net profit of 54.89 and 93.32 million Pakistani rupees can be gained in the first year and then in successive years, respectively. Thus, this research provides a way to produce renewable energy fuel, biodiesel from the waste lipids (FFAs) of wastewater drains to meet the energy requirements and a solution for the conservation of water bodies.

KEYWORDS:

• Amberlyst A21
• Amberlyst 15
• adsorption
• esterification
• fractional distillation

Acknowledgments

The authors like to say thanks to the School of Civil and Environmental Engineering (SCEE), National University of Sciences and Technology (NUST), Sector H-12, Islamabad, Pakistan for providing laboratory support for the analysis of this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Authorship contribution statement

All authors read and approved the final manuscript.

Data availability staement

The datasets generated and/or analyzed during the study are available from the corresponding author [email protected]) on a reasonable request.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567036.2022.2105452.

Additional information

Funding

This research work was funded by the School of Civil and Environmental Engineering (SCEE), National University of Sciences and Technology (NUST), sector H-12, Islamabad, Pakistan.

Notes on contributors

Ehsan Mustafa Hashmi

Ehsan Mustafa Hashmi Investigation and writing original draft.

Yousuf Jamal

Yousuf Jamal Overall supervision, project administration, editing final draft.

Nida Maqbool

Nida Maqbool Associate supervision, formal analysis, and review of original draft.

Hafiz Muhammad Aamir Shahzad

Hafiz Muhammad Aamir Shahzad Water and wastewater sample analysis and design of methodology.

Beenish Imtiaz

Beenish Imtiaz Manuscript draft layout, figures, and tables formatting.

Sher Jamal Khan

Sher Jamal Khan Associate supervision for experimental work, design of methodology.