Ozonização de lodo de filtros biológicos percoladores visando a solubilização de sólidos e o incremento de produção de biogás na digestão em reatores UASB

Abstract

Domestic sewage treatment presents a major challenge in terms of managing subproducts, especially the sludge generated in biological treatment and biogas from the anaerobic stage. The costs for treatment and final disposal of sludge can reach around 60% of the operating cost of a Sewage Treatment Plant, and it is essential to seek alternatives, whether reusing them or reducing their generation. In stations that have aerobic biological treatment, such as Trickling Filter - TF, aerobic sludge is generated, which must undergo digestion. Seeking to optimize sludge treatment, researches are being developed for secondary sludge digestion carried out in the UASB treatment unit. In relation to biogas, its largest constituent is methane (CH4), which must receive some type of treatment to mitigate the greenhouse effect, with the majority of STPs only being burned to release CO2. However, it can be applied to generate electrical energy from its burning or used as biogas. On this perspective, the technique of pre-ozonizing aerobic sludge for subsequent digestion in the UASB has great potential, since studies indicate the possibility of reducing solids in the sludge and increasing biogas generation in the UASB. This study aimed to evaluate the ozonation technique, analyzing the effect of different doses of ozone on sludge quality and methanogenic potential. To this end, bench tests were carried out, with sludge collected in a UASB reactor and an TF. Therefore, ozonation of the sludge was carried out at doses of 20 mgO3/gTS, 150 mgO3/gTS and 275 mgO3/gTS, with a reduction in total solids in the order of 29%, 34% and 50% being observed for each dose, respectively. In relation to methane generation, the study pointed out that the simple fact of sludge recirculation already increases production and the ozonation technique has the potential to increase it even further, with the best value of methane generation being obtained at a dose of 275 mgO3/gTS For the scenarios analyzed in terms of economic forecast, the practice of ozonation and sending sludge for digestion in a UASB reactor proved to be advantageous.