Send Orders for Reprints to reprints@benthamscience.ae 56 Current Environmental Engineering, 2015, 2, 56-63 Biological Denitrification: Screening of Packing Material, Comparison of Denitrification Rate by Pseudomonas aeruginosa and Pseudomonas stutzeri, Application and Design of Bioreactor Akshay Jakhete, Sayali Titre, Pritam Patil * and Jitendra B. Naik Department of Chemical Engineering, University Institute of Chemical Technology, North Maharashtra University, Jalgaon, Maharashtra, 425001, India Abstract: Current studies explore the viability, applicability and comparison of Pseudomonas aeruginosa and Pseudomonas stutzeri based biological denitrification of waters containing high concentration of nitrate and nitrite waste originating from various agricultural and industrial sources. This process converts the readily soluble nitrates to harmless nitrogen gas through a formation of series of intermediates. Experimental work involved use of varying concentration of nitrates and nitrites with different packing conditions, substrates and were analyzed by UV-Vis spectrophotometer. The parameters such as C/N ratio, temperature and pH were optimized for decreasing concentration of nitrates and nitrites. Best packing materials for nitrate reduction proved to be the agro waste based materials which have potential to be used for nitrate reduction of various waste water samples obtained around the city. Average nitrate reduction rates obtained for agro based waste packing condition exhibited about 96.55% and 95% for Pseudomonas aeruginosa and Pseudomonas stutzeri respectively. When applied for denitrification of waste water sample using the obtained reaction parameters, average nitrate reduction obtained was 53.84% and 33.72% for Pseudomonas aeruginosa and Pseudomonas stutzeri respectively. Based on the obtained observations and experimental results, general bioreactor for denitrification process has been designed. Keywords: Agro waste, denitrification, nitrates, nitrites, Pseudomonas aeruginosa, Pseudomonas stutzeri. 1. INTRODUCTION The increasing contamination of water of nitrogenous materials and the destruction of habitats endangers the availability of water for human consumption and wildlife development. In the country like India, this problem is mainly due to the excessive use of agricultural fertilizers, septic tank systems, animal waste disposal, explosives and industrial effluents. The increasing nitrate concentration in ground water is one of the most important and serious environmental problems because it poses serious health risk to humans due to the body´s reduction of nitrate to nitrite [1, 2]. The nitrite reacts with the hemoglobin in the blood and thus oxygen transfer to cells is inhibited. This phenomenon is called methaemoglobinemia or the blue baby syndrome [3- 5]. Water containing high NO 3 -N concentrations should be avoided for consumption, since it increases the probability of non-Hodgkin’s lymphoma and gastric cancer [6]. Also, scientific evidence shows that nitrate and nitrite are likely to cause mutagenesis and teratogenesis, miscarriage in pregnant women, coronary cardiac diseases, and cancer of the ovaries and growth of hypertrophy of the thyroid [7-9]. Nitrate and Nitrite nitrogen are known to be toxic for animals and aquatic life, like for fish, benthic fauna, plants, and bacterioplankton. At lower concentrations, nitrate poisoning have known to result in increasing cases of still birth incalves, ovaries with cyst development, lower milk production, reduced weight gains, and vitamin A deficiency *Address correspondence to this author at the Department of Chemical Engineering, University Institute of Chemical Technology, North Maharashtra University, Jalgaon, India; E-mail: patilpritamb29@gmail.com [10, 11]. This danger necessitates the removal of nitrate from water reserves. The U.S. Environmental Protection Agency and WHO has set 10 ppm of nitrate nitrogen as desirable limit for human consumption [12, 13] whereas Indian standard for nitrates has been set at 45 ppm, which is desirable for human consumption [14]. Nitrates from different waste can exhibit the characteristics of either point or nonpoint source pollution. Point sources occur at or near the actual waste facility involved and typically exhibit high levels of nitrate or ammonia in a limited area. Nonpoint sources are spread over large areas [10]. Increased nitrate concentrations in groundwater have led to the shutdown of wells and rendered aquifers unusable as water sources. Hence nitrates removal is an important aspect of present day wastewater treatment process [15]. Several techniques are available for nitrate reduction such as reverse osmosis, chemical denitration, biological denitrification along with physiochemical methods each with its own advantages and disadvantages [16-20]. Physiochemical treatments involve processes such as ion exchange and reverse osmosis which produces secondary concentrated waste and is not feasible [21]. Another way to remediate nitrates is by thermal denitration which requires a temperature of more than 950 0 C and also produces large amount NOx. The best way to remediate nitrates is to convert them into nitrogen gas which is achieved by both chemical denitration and biological denitrification [21]. Chemical denitration results in nitrate reduction to nitrogen gas using suitable reducing agents in presence of catalysts but is feasible only when nitrate concentration is very high. For lower concentrations of nitrate, biological denitrification is the most effective method and is generally preferred for industrial and domestic sewage 2212-7186/15 $58.00+.00 © 2015 Bentham Science Publishers