Pós-tratamento de efluente de reator anaeróbio em lagoa com lemna

Abstract

The absence of treatment and improper disposal of effluents contribute to the deterioration of receiving water bodies. However, among the proposed alternatives for post-treatment of wastewater ponds are to lemnas. These lagoons are capable of capturing the nutrients sewage efficiently and reduce a large amount of suspended solids Also act by inhibiting algae, and generate biomass rich in protein, which has utilities such as animal feed and fertilizer. This research aimed to evaluate and compare the efficiency of the treatment of domestic sewage pond lemnas in two phases, with different hydraulic retention time (HRT). This pond, in phase I, operated with influent volume of 75 liters/day and HDT of 5, 10 and 15 days, while phase II, the volume was increased to 140 liters/day TDH was decreased to 2.7, 5.4 and 8.0 days. The structure of the pond lemna had a volume of 1,125 m3 and surface area of 2.25 m2 (total depth of 0.6 m, 0.5 m water depth, length of 1.5 m and width 1.5 m). Therefore, during the two phases of this research the following parameters were monitored: the wastewater - temperature, pH, biochemical oxygen demand (BOD5), dissolved oxygen (DO), total suspended solids (TSS), phosphorus (P), coliforms thermotolerant in macrophyte - nitrogen (N), phosphorus (P), biomass and crude protein (%). The treatment system performance as presented in polishing domestic wastewater, following the removal efficiency of organic and nutrient load: 80% (phase I) and 66% (phase II) for BOD5, 83% (phase I) and 34% (phase II) for P. The lemnas converts these nutrients into biomass rich in proteins with an average grade of CP% from 27.93%. The production of protein in lemnas throughout the experiment was: 355 g (LMN1), 367 g (LMN2) and 370 g (LMN3). Notably, the ability of the system to treat these waters was higher in phase I, which has the greatest TDH. The presence of algae genus Uronema was found, as well as the competition with these lemna study, but after the modifications aimed at mitigating the temperatures this competition was controlled. With this study, it was possible to evaluate the post-treatment of domestic wastewater, the limiting factors for this system and the biomass of Lemna valdiviana Phil., under the climatic conditions of Feira de Santana, Ba. Finally, we conclude that there is potential for nutrient recovery of these waters, as well as reuse of biomass produced as a possible source of animal feed and income.