CO2 supplementation to domestic wastewater enhances microalgae lipid accumulation under mixotrophic microenvironment: effect of sparging period and interval.

Bio-sequestration of CO(2) through microalgae cultivation is considered as a viable option for biofuel production as well as CO(2) mitigation. Influence of CO(2) sparging period and interval was evaluated on the growth and lipid accumulation of microalgae cultivated in domestic wastewater under mixotrophic microenvironment. Process performance was assessed in two phases viz., growth (GP) and starvation phases (SP) each with 8 days of retention time. Experimental variations depicted marked influence on biomass growth and lipid accumulation of microalgae with the function of harvesting period. Sparging period of 120 s documented maximum biomass growth (GP, 3.4 mg/ml) and lipid productivity (SP, 27.3%) while in intervals, 4h (120 s) condition showed maximum biomass (3.2mg/ml) and lipid productivity (27.8%). Total chlorophyll components documented higher concentrations of Chl b supporting the observed higher lipid productivity. Fatty acid composition varied with the experimental variations and represented higher degree of saturation indicating their utility as biodiesel.

Aerobic remediation of petroleum sludge through soil supplementation: microbial community analysis.

The effect of soil concentration on the aerobic degradation of real-field petroleum sludge was studied in slurry phase reactor. Total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs) showed effective removal but found to depend on the soil concentration. Aromatic fraction (48.12%) documented effective degradation compared to aliphatics (47.31%), NSO (28.69%) and asphaltenes (26.66%). PAHs profile showed efficient degradation of twelve individual aromatic compounds where lower ring compounds showed relatively higher degradation efficiency compared to the higher ring compounds. The redox behaviour and dehydrogenase activity showed a linear increment with the degradation pattern. Microbial community composition and changes during bioremediation were studied using denaturing gradient gel electrophoresis (DGGE). Among the 12 organisms identified, Proteobacteria was found to be dominant representing 50% of the total population (25% of γ-proteobacteria; 16.6% of ß-proteobacteria; 8.3% of α-proteobacteria), while 33.3% were of uncultured bacteria and 16.6% were of firmicutes.