Remoção de nitrogênio e fósforo de lixiviado de aterro sanitário aplicando a Chlorella sp. imobilizada em matriz de alginato de cálcio

Abstract

The generation of solid urban waste represents a challenge that requires the participation of several segments to solve it. The putrescible fraction of the residues during its biodegradation generates the leachate, wastewater of high contaminating power that presents a complex matrix with emphasis on high magnitudes of total solids, N-ammonia, phosphorus, COD and recalcitrant substances. In this context, alginate immobilized alginate technology emerges as a sustainable and efficient strategy for removing pollutants from wastewater. Immobilization consists of cell retention in a particular region of the bioreactor in which chemical reactions must take place. This research investigated the phytoremediation potential of Chlorella sp. removing nutrients from landfill leachate. The leachate was collected at the João Pessoa Metropolitan Landfill and the Chlorella sp. was isolated from the leachate treatment pond system and grown in Bold’s Basal Medium. Tubular and conical bioreactors fed in batch and continuous regimes were monitored. The parameters evaluated were pH, N-ammoniacal, P-Total, ions, Chlorophyll a, dissolved oxygen, ions and turbidity. SEM and EDS microanalysis of the spheres with immobilized algae were performed. The statistical analysis of the data was carried out through a full factorial planning of three levels Box-Behnken 3^(2-0) design (BBD) combined with the response surface methodology and (ANOVA). Bioreactors fed in batches and AG / QT (alginate / chitosan) spheres obtained an average removal of 40% of ammoniacal N with average affluent concentrations of 240 mg.L^-1. In spheres with Chlorella sp. in AG (alginate) the average removals of N-ammonia were in the range of 85.3% in the 1st hour of contact time. In suspended systems, there was cell growth in the N-ammoniacal bands between 47 and 2182 mg.L^-1, with an increase of Chlorophyll a of 1500% in concentrations of 99 mg.L^-1^and removals of up to 88 mg-N in concentrations 798 mg.L-1. It was found that the increase in the percentage of leachate inhibited cell growth. In the continuous bioreactor with Chlorella sp. immobilized in AG, removals of P-total, N-ammoniacal, Na2^+, K^+ and Mg2^+ respectively of 63, 42, 28, 49 and 55% were recorded in 2-hour HRT. Phytoremediation was achieved through a combination of mechanisms including bioassimilation, precipitation as a consequence of pH and adsorption in the polymeric matrix. Thus, the results point to the potential of Chlorella sp. in the treatment of landfill leachate.