Estudo da tecnologia do LGA: princípios, remoção biológica de nutrientes e avaliação para efluentes de laticínios

Abstract

The wastewater produced in a dairy is characterized by its high organic load, large amount of nutrients and the presence of chemical and inorganic compounds resulting from cleaning and disinfection steps. Recent researches point to a type of biological treatment with very efficient removal of organic matter and which can still remove nutrients in a single reactor, resulting in area and energy savings. It is a system using aerobic granular sludge through a Sequential Batch Reactor (RBS). The dense spherical structure of the granules allows for greater sedimentation speed and limits oxygen transfer, implying the existence of aerobic, anoxic and anaerobic zones that contribute to the processes of biological removal of nutrients, further favored by the long time of cell residence. Therefore, a survey was carried out with different works in order to gather information and present results already observed by other researchers. In general, it was found that the range from 20 to 30º C had a high rate of nitrification / denitrification and good granule formation. A survey using dairy effluent presents removal efficiency results, as follows: 68 to 96% chemical oxygen demand (COD) removal efficiency, 84.4 to 97.2% oxygen removal removal efficiency ( BOD), 68 to 99.85% ammonium removal efficiency (NH₄), 36.6 to 79.4% total nitrogen removal (Nt) and 11.54 to 72.24% phosphorus removal efficiency total (Pt). Treatment results for other types of effluents were also presented. With urban wastewater effluents, the average NT removal was only 21%, limited due to the low cell retention time (TRC) (2 to 3 days) and reaching NH₄ removal values around 80%, attributed value at relatively high temperatures (16-27°C). For oil refinery wastewater, results of 86% and 92% were found in the removal efficiency of COD and NH₄, respectively. It is concluded that the Aerobic Granular Sludge (LGA) technology is one of the most studied technologies for effluent treatment, however, some points still need to be improved, such as the granule instability problem (crucial factor for long operation deadline).