Desenvolvimento de biossorvente a partir de lodo anaeróbio granular para aplicação em sistemas de remoção de fosfato e em sistemas para a remoção de íons metálicos

Abstract

The removal of certain classes of pollutants from wastewater is still a challenge for engineering projects, for example, when the objective involves the removal of phosphorus and metals. The accumulation of phosphorus in the environment is harmful to nature and aquatic life forms, and anthropogenic sources, such as agricultural and industrial activities, are primarily responsible for this process. The removal of phosphorus from wastewater in conventional biological treatment systems (activated sludge or anaerobic systems) is efficient, however, it depends on complex and expensive sewage and/or effluent treatment plant projects. In addition to the problem of phosphorus accumulation and removal, there are water contaminated by metals, which when present in the environment cause several problems to nature and human health. Adsorption using biological materials as adsorbents (biosorption) has shown satisfactory results for the removal of numerous environmental pollutants, however, few studies have been conducted using biosorption for phosphorus removal and, in the case of metals, there is still a large gap regarding efficient methods involving the removal of this type of pollutant. This work evaluated the biosorption of phosphorus and the metals zinc, nickel and chromium, using pellets made with granular anaerobic sludge as biosorbents. The methodology of this work was divided into three phases. The first was based on the characterization of granular anaerobic sludge, development and characterization of the pellet, and application in phosphate, zinc, nickel and chromium biosorption systems. The second stage was based on the performance of kinetic and adsorption isotherm studies and the third stage included tests of desorption of the phosphate ion, zinc, nickel and chromium of the tablet. In the characterization of the granular anaerobic sludge, it was observed its high degradation as a function of temperature, with 82.22% of mass loss at 650°C. The tablet used as a biosorbent showed efficiency between 70 and 79% in the removal of phosphate for concentrations from 30 to 360 mg/L, in up to 144h, and between 68 and 92.41% for the metals zinc, nickel and chromium after 96h of contact. In the case of metals, it can be observed that the efficiency values decrease as a function of the increase in the concentration of metals in the aqueous solution. More than one kinetic model was fitted to the data obtained for phosphate removal, which shows that the adsorption process can be controlled by more than one type of mechanism, for metals, only the pseudo second order model showed a satisfactory fit. For zinc and nickel isotherms, the Langmuir and Freundlich fit models were well fitted, for chromium, the fit to such models did not occur satisfactorily, however, the adsorption process was favorable for the 3 metals. The development of granular anaerobic sludge pellets and their application in biosorption systems proved to be a route of environmental and economic interest, with high removal efficiencies of the tested pollutants.