Industrial wastewater treatment for fertilizer industry- A case study

Wastewaters from chemical fertilizer industry mainly contain organics, alcohols, ammonia, nitrates, phosphorous, heavy metals such as cadmium and suspended solids. The nature of effluent streams varies in terms of its constituents and complexity. The present work attempts to fill the void in the literature that mostly reports synthetic wastewater treatment studies; by evaluating effluent treatment solutions and comparison of different methods for real wastewaters from fertilizer industry. An attempt has been made to devise suitable methodology mainly using a new device in the form of Vortex Diode for hydrodynamic cavitation and also using adsorption, for several real wastewater streams from different locations in one major fertilizer industry of Maharashtra, India. The strategy involved characterization of wastewaters, studies on effective removal of Chemical Oxygen Demand(COD) and devising solutions for effective reduction in ammoniacal nitrogen-a more serious issue in the fertilizer industry. The characterization of wastewaters from different streams revealed huge variation in COD from 50 to 140,000 ppm and ammoniacal nitrogen from 6 to 1700 ppm. Some effluent streams contained alcohol up to 5 %. Hydrodynamic cavitation using vortex diode and adsorption with modified carbons were used to treat these streams. Cavitation studies were carried out on a pilot plant and effect of pressure drop, cavitating device and process intensification were studied. It was observed that the effluent treatment strategy requires careful identification and application of suitable treatment method on the basis of nature of the effluent. Also, hydrodynamic cavitation, using vortex diode is techno-economically attractive option in treating fertilizer wastewaters giving a very high reduction in COD and ammoniacal nitrogen (up to 85%), similar to adsorption. The results clearly identify potential of newer methodologies in treatment of effluents in fertilizer industry.