Remoção de amônia através da precipitação da estruvita em um reator airlift: construção de uma unidade experimental e análise de eficiência do processo

Abstract

Certain effluents contain a high concentration of nutrients. They are contaminating agents if dumped into sources without proper treatment. It is the cause of eutrophication of lakes and rivers, seen as a significant environmental problem. One possibility is to carry out the treatment of effluents rich in ammonia converting to struvite by crystallization. Thus, the objective of this work was to build a fluidized bed reactor to convert ammonia present in an industrial effluent through precipitation in the form of struvite. The proposed equipment allows treating up to 10 L of effluent by applying precipitation techniques. Initially, the effluent was diluted so that the initial ammonium concentration was 250 mg.L-1. For carrying out the precipitation experiments, an experimental design of type 2² + 3 central points was used. The variables investigated were compressor airflow (3 L.min-1 e 6 L.min-1), molar ratio ([NH4+:PO43-:Mg2+] [1: 1.30: 1.30; 1: 1.30: 1.63; 1: 1.30: 1.96]) and reaction time (20, 40 and 60 min). Analysis of the precipitated material was carried out, such as sedimentability, x-ray diffraction, and image capture under an electron microscope to evaluate the morphology. The crystals showed excellent sedimentability with IVL less than 4.63 mL.g-1. A cost analysis of an industrial plant was also carried out. The percentage of ammonia removal was satisfactory, greater than 90%. The morphological analysis was shown to be adequate for presenting crystals in the form of dendritic X and needles, as described in the literature. The estimated financial analysis for struvite production proved to be profitable if the market value is greater than $ 3.40 kg-1. It was found that the recovery of construction investment occurs in 1.6 years. The estimate predicted that at the end of 10 years of operation, the net present value obtained was 1.2 million dollars