In this study, we present the gasification of microalgae (Chlorella Vulgaris) and glycerol in supercritical water (SCW) using batch (quartz capillaries) and continuous flow reactors. Preliminary tests of algae gasification were done with quartz capillaries at varying operating conditions such as temperature (400-700 °C), reaction time (1-15 min), and the addition of catalysts. The dry gas composition of uncatalyzed gasification of algae in SCW mainly comprised of CO 2 , CO, CH 4 , H 2 , and some C 2 -C 3 compounds. Higher temperatures, low algae concentrations, and longer residence times favored the algae gasification efficiency (GE). The addition of catalysts to the capillaries resulted in higher yields of hydrogen and lower CO yields via enhanced water-gas shift activity. The addition of catalysts accelerated the gasification efficiency up to a maximum of 84% at 600 °C and 2 min reaction time with nickel-based catalysts. Complete gasification is achieved at higher temperatures (700 °C) and with excess amounts of (Ru/TiO 2 ) catalyst. To elucidate part of the difficulties related to the SCWG of algae, reforming of a model compound (here glycerol) in SCW was carried out in a continuous flow reactor in the presence of additives like amino acids (L-alanine, glycine, and L-proline) and alkali salt (K 2 CO 3 ) and combinations thereof. The amino acids L-alanine and glycine have a minor effect on the gasification process of glycerol, and a significant reduction of the gasification efficiency was observed in the presence of L-proline. Coke formation and colorization of the reactor effluent were more noticeable with glycerol-amino acid mixtures. In the absence of amino acids, the glycerol solution gasified without any coke formation and colorization of the reactor effluent. Again this effect was more pronounced in the presence of L-proline. The addition of K 2 CO 3 enhanced the glycerol gasification efficiency and increased the hydrogen yields promoting the water-gas shift reaction.

a b s t r a c tA combination of hydrodynamic cavitation and heterogeneous advanced Fenton process (AFP) based on the use of zero valent iron as the catalyst has been investigated for the treatment of real industrial wastewater. The effect of various operating parameters such as inlet pressure, temperature, and the presence of copper windings on the extent of mineralization as measured by total organic carbon (TOC) content have been studied with the aim of maximizing the extent of degradation. It has been observed that increased pressures, higher operating temperature and the absence of copper windings are more favourable for a rapid TOC mineralization. A new approach of latent remediation has also been investigated where hydrodynamic cavitation is only used as a pre-treatment with an aim of reducing the overall cost of pollutant degradation. It has been observed that approach of latent remediation works quite well with about 50-60% removal of TOC using only minimal initial treatment by hydrodynamic cavitation.

For the first time, hydrodynamic cavitation induced by a liquid whistle reactor (LWR) has been used in conjunction with the advanced Fenton process (AFP) for the treatment of real industrial wastewater. Semi-batch experiments in the LWR were designed to investigate the performance of the process for two different industrial wastewater samples. The effect of various operating parameters such as pressure, H2O2 concentration and the initial concentration of industrial wastewater samples on the extent of mineralization as measured by total organic carbon (TOC) content have been studied with the aim of maximizing the extent of degradation. It has been observed that higher pressures, sequential addition of hydrogen peroxide at higher loadings and lower concentration of the effluent are more favourable for a rapid TOC mineralization. In general, the novel combination of hydrodynamic cavitation with AFP results in about 60-80% removal of TOC under optimized conditions depending on the type of industrial effluent samples. The combination described herein is most useful for treatment of bio-refractory materials where the diminution in toxicity can be achieved up to a certain level and then conventional biological oxidation can be employed for final treatment. The present work is the first to report the use of a hydrodynamic cavitation technique for real industrial wastewater treatment.

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