title: Effect of thermal pre-treatment on co-digestion of duckweed (Lemna gibba) and waste activated sludge on biogas production.
abstract: The duckweeds (DW) are considered as a major problem in tropical aquatic system as they grow very fast and produce enormous rich-biomass, which can be harvested for renewable energy operations. But complex lignocellulosic compounds limit their utility in process like anaerobic digestion. This batch study aimed to analyse characteristics (proximate, ultimate and physico-chemical) and possible utility of DW for anaerobic co-digestion with waste activated sludge (WAS) under mesophilic conditions for 35 d. Two sets of experiment were tested: substrate with and without thermal pre-treatment. Five combinations of DW: WAS (70:20, 60:20, 50:20, 40:20 and 30:20%) were established and biomethanation along with changes in pH, volatile solids (VS), volatile fatty acids (VFAs), and soluble chemical oxygen demand (sCOD) of digestate were recorded. The total CH4yield (mL CH4g-1VS) ranged between 60 and 468 for pre-treated, and 9 and 76 for non-pre-treated. The maximum CH4yield was 468 mL CH4g-1VS in DW: WAS (50:20). Thermally treated setups, showed about 13-, 24.1-, 21.1-, 1.4-, and 2.3-fold higher CH4than non-treated setups. The treated mixtures showed high reduction ofSCOD (>41-96) and VS (>59-98%) in co-digesters. The high degree of Gompertz curve fitting (R2> 0.99) has suggested pre-treatment of substrate for optimal outputs of co-digester. Based on results obtained, it is suggested that DW (50-60% in digester) can be used as renewable energy resource for biomethanation process after thermal pre-treatment.
authors.affiliation: School of Environment & Natural Resources, Doon University, Dehradun 248001, India.
authors.forename: Rubia Zahid
authors.initials: RZ
authors.lastname: Gaur
authors.affiliation: Department of Civil Engineering, Jamia Millia Islamia, New Delhi 110025, India.
authors.forename: Abid Ali
authors.initials: AA
authors.lastname: Khan
authors.affiliation: School of Environment & Natural Resources, Doon University, Dehradun 248001, India. Electronic address: suthariitd@gmail.com.
authors.forename: Surindra
authors.initials: S
authors.lastname: Suthar
mesh_terms: D000693:Anaerobiosis; D029064:Araceae / Q000378:metabolism*; D056804:Biofuels; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors / Q000382:microbiology; D008697:Methane / Q000096:biosynthesis; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology; D013696:Temperature; D014866:Waste Products
chemical_list: D056804:Biofuels; D012722:Sewage; D014866:Waste Products; D008697:Methane
keywords: Anaerobic co-digestion; Aquatic weed (L. gibba); Gompertz equation; Methane; Waste activated sludge