Remoção de nitrogênio e fósforo de efluentes de suinocultura e abatedouro por meio da precipitação de estruvita

Abstract

Agro-industrial effluents such as swine and slaughterhouse are rich in nutrients, whose removal by biological processes is not efficient. Thus, physicochemical processes have been

widely studied to remove Phosphorus (P) and Nitrogen (N) in orthophosphate precipitates (P- PO4

3- ) with lime, aluminum and iron salts. The method that has stood out is the precipitation process with struvite crystal generation (MgNH4PO4.6H2O), which can be an alternative to recover the Phosphorus present in wastewater, minimizing environmental impacts and allowing nutrient cycling in agriculture. The present work aimed to recover the Phosphorus and Nitrogen in the form of struvite salt in two types of effluents, the pig and slaughterhouse, and to evaluate the quality of the crystals generated, with the possible identification of struvite. The swine effluent was collected at three points: after the preliminary treatment (pretreated effluent); and after different forms of treatments: anaerobic (treated effluent 1); and anaerobic / aerobic (treated effluent 2); and slaughterhouse effluent was collected at two points: after undergoing preliminary treatment (pretreated effluent); and after treatment in facultative pond (treated effluent). Initially, the pH of the samples was adjusted to around 9.5. Three tests were performed in jartest (400 rpm, approximately 1,285 s-1

for 15 min) varying

the stoichiometric ratio: Mg2+ , P-PO4 3- 1: 1 (test 1), Mg2+ , P-PO4 3- 1: 1.6: 1. (test 2), and Mg2+ ,

P-PO4 3- and N-NH4 + 1: 1: 1 (test 3). After 15 min, the equipment was turned off and

supernatant samples were collected at 20, 40, 60, 80, 100 and 120 min for P-PO4 3- analysis. The precipitated solids were oven dried, sieved, and analyzed for the presence of NTK, PT and total Mg. The solids recovered from the pretreated effluents (test 3) and treated effluents were analyzed by Scanning Electron Microscopy (SEM) and Infrared Spectroscopy (FTIR). The observed results show an efficient way of phosphate removal from both pretreated and treated swine and slaughterhouse effluents. The highest P-PO4 3- removal efficiencies after 120 minutes were for treated effluents (> 90%) in test 3. The recovered solids were rich in N and P, and the qualitative results of the recovered crystals shown in the analyzes. SEM and FTIR were mostly struvite. In addition, a high similarity was observed between the results of the present work and the results of the standard sample, reflecting the applicability and efficiency of the experiment for P and N recovery of swine and slaughterhouse wastewater.