A Reliable Solution for Treatment of River Water Using Hydrodynamic Cavitation in Combination with Chemical Additives

Abstract

Hydrodynamic cavitation treatment of Indrayani river water was carried out using hydrodynamic cavitation (HC) and in combination with soda lime. An in-house cavitation setup has been developed. As a cavitating device orifice plates of different geometries-single orifice plate diameter (4 mm), multiple orifice plates-6 holes diameter (1 mm) and 9 holes diameter (0.8 mm) were used in HC reactor. Tests were carried out with a sample size of (wastewater) 50 L, for 2 h duration. The effect of process parameters such as inlet pressure, cavitation number (CV), flow rates and soda lime loading on the extent of reduction of COD, TDS, permanent hardness, pH, color were studied. Observation shows that as cavitation no (CV) decreases from 4.25 to 0.55 percent removal for COD reaches up to 71.4%. At the same time percentage reductions for TDS and permanent hardness reaches up to 85% and 82.5% respectively. For 9 hole orifice plate (CV 0.55) there was the maximum percentage reduction of 71.4% COD, 85% TDS, 82.5% removal of permanent hardness at a pressure of 2 atm and flow rate 3 m3/h. For 9 holes plate results shows that the COD, TDS, and permanent hardness levels reduced to the limit of drinkable water. With HC alone pH goes up to 6.7. Experiment with soda lime in addition to HC shows a further reduction in permanent hardness up to 87% but for COD results were the same as a 72% reduction. Hence hydrodynamic cavitation represents a reliable and cost-effective way for water treatment with the very less initial cost.