Ajit Haridas

Photocatalytic treatment of toxic organics in wastewater: Toxicity of photodegradation products

The tested compounds, methyl vinyl ketone, pentachlorophenol and 2,4-dichlorophenol, inhibited the respiratory activity of activated sludge. Detoxification of these compounds was achieved by exposing the compounds (75 mg/l) to sunlight with the addition of TiO2 (1000 mg/l), which acts as a photocatalyst. Ultraviolet absorption spectra of the photocatalytically treated samples were deprived of the characteristic peaks showing that the compounds have undergone photoxidation. Prior to complete detoxification of pentachlorophenol and 2,4-dichlorophenol there was an increased inhibition of the activity of the activated sludge, indicating the photocatalytic generation of intermediary toxic products.

Anaerobic protozoa and their growth in biomethanation systems

This study was to investigate growth of protozoa and its influence on biodegradation in anaerobic treatment systems. It was done by specifically controlling and monitoring growth of protozoa versus degradation in continuous stirred anaerobic reactors and batch anaerobic reactors. Occurrence of a diverse protozoa population such as the ciliates, Prorodon, Vorticella, Cyclidium, Spathidium, Loxodes, Metopus were observed in stable anaerobic systems and the flagellates, Rhynchomonas, Naeglaria, Amoeboflagellates, Tetramitus, Trepomonas and Bodo during increased VFA concentration and affected periods of biomethanation. The abundance of ciliates in the anaerobic system had significant correlation with the reduction of MLSS, increased rate of COD removal and higher methane production. The results of this study thus tend to relate increased anaerobic degradation with the abundance of protozoa, mainly ciliates, which indicate their possible involvement in the process. Present study also reveals that performance of anaerobic process can be assessed by monitoring the protozoa population in the system.