Studies in newer methodologies and materials/ material modifications for environmental, pollution control applications specifically for water treatment and desulfurization

Abstract

Safe and clean environment is most essential for the ecosystem and Water and Air are two most critical components. The present research addresses two specific studies in this regard; one pertaining to the safe water and other pertaining to clean air, Disinfection of water and Desulfurization of transportation fuels. Safe drinking water is necessary to prevent occurrence of large number of waterborne diseases and to save millions of lives, one of the most priority subjects for developing country like India. The main objective of this research is to develop methodology which provides safe and healthy drinking water at low cost with substantial ease of operation, scale-up and without harmful disinfection by products. The study is an attempt to improvise the hydrodynamic cavitation methodology for effective disinfection of water and also to suggest prototype development for practical application. The enhancement in the disinfection efficiency was evaluated specifically for the effect of pressure, temperature, pH, microbial inoculum size and also on effect of different additives for the two model microbial strains, gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus). Also, complete removal of antimicrobial resistant (AMR) and relatively less researched, gram-negative opportunistic pathogen, Pseudomonas aeruginosa and gram-positive methicillin resistant, Staphylococcus aureus was studied. The efficacy of the hydrodynamic cavitation was evaluated for the two types of flows/cavitation devices – linear flow in the case of orifice and vortex flow for vortex diode. The present study, for the first time, reports possible use of different natural oils such as castor oil, cinnamon oil, eucalyptus oil, clove oil, lemongrass oil, peppermint oil etc. in conjunction with hydrodynamic cavitation. Exceptionally high rates were obtained for practically complete removal of all types of bacteria, within less than 10 minutes. The nature of oil modifies the cavitation behaviour and an order of magnitude enhancement in the cavitation rate was observed for the oils such as eucalyptus, clove oil and peppermint oil, for a very small concentration of 0.1%. Process intensification using simple aeration can further increase the rates resulting in significant lowering of oil dose. The use of natural resources such as plant extracts (ginger, turmeric, mango ginger etc.) was also successfully reported in disinfection for the first time. Differences between oil and water soluble additives were highlighted. The increased rates of disinfection using oil/extract can drastically reduce the time of operation and consequently reduce cost of disinfection. A possible mechanism is proposed for the effect of oil/extract and hydrodynamic cavitation in cell destruction through the rupture of cell wall, oxidative damage and possible DNA denaturation. A cavitation model using per pass disinfection was used to correlate the data. The developed methodology, Safe Water and Sustainable Technology Initiative from Indian Knowledgebase, SWASTIIK, has the potential to provide viable alternative to chemical disinfection methods and operating cost of only 0.036 $/m3 was estimated (~Rs. 2.5/ m3 or 0.25 Paise per liter). Synthesis, design and development of new materials for disinfection of water and desulfurization of liquid fuels was also investigated for the role of adsorbent modifications. Spherical activated carbons from polymer resin were developed with metal modifications, using copper and nickel, for gradation of zeta potential (-5.01 to 8.64mV) and high metal loading (up to 12.3%). The materials provide improved removal of various contaminants from aqueous and organic streams removal of bacteria from water and sulfur removal from fuel. Overall, the present research has resulted in development of a new technology and methodologies for disinfection of water.