Remoção de compostos nitrogenados de água utilizando processos de separação por membranas

Abstract

The presence of nitrogen compounds in their different oxidation states is an indicator of contamination of water resources and possible unsatisfactory sanitary conditions for the population that consumes this water. Nitrite and nitrate are associated with a number of adverse health effects: induction of methemoglobinemia in infants and a potential formation of carcinogenic nitrosamines and nitrosamides in adults. Excess of nitrogen in surface water is mostly derived from animal waste, household and industrial effluents, agricultural fertilizers. In this context, the aim is to evaluate the contamination of the water bodies of the municipalities of Caxias do Sul by nitrogen compounds, through the determination of ammoniacal nitrogen, nitrates and nitrite, before the resolution of the NATIONAL ENVIRONMENTAL COUNCIL (CONAMA) n° 357. In Brazil, the maximum concentration of nitrate, nitrite and ammoniacal nitrogen in water is 10, 1.0, and 1.5 mg.L-1, respectively (CONAMA, 2005). To achieve potability standards, some of the treatment methods that are currently used are: ion exchange, adsorption, biological denaturing, and also membrane separation processes (MSP). In this work, two different MSP systems were tested to treat and separate nitrate (NO3 -), nitrite (NO2 -) and ammonia (NH4 +) ions: reverse osmosis (RO) and electrodialysis (ED). The synthetic solutions containing the ions of interest were used with both processes, separately. Subsequently, a real sample from Arroio Belo (Caxias do Sul) was tested with the system to evaluate its efficiency of removal of ions mentioned above. The results of the ED and RO tests, for which they were synthesized at a removal percentage above 90%. For Arroio Belo water, RO results showed a removal efficiency above 90% for nitrites and ammonia, and 20% for nitrates. Assigning the latter result to the interactions, it was concluded that the units were effective for the removal of nitrogenous from the solutions and from the Arroio Belo sample tested.