Post-treatment of anaerobic reactor effluent by double filtration with gravel and clinoptilolite and ozone disinfection

Abstract

Anaerobic reactors are an excellent alternative in the treatment of domestic effluents. However, this system presents the disadvantage of requiring post-treatment. Many technologies have been studied and rapid filtration systems have proven to be a viable alternative for the post-treatment of anaerobic reactor effluents. This study evaluates the efficacy of an anaerobic reactor effluent post-treatment system using double filtration (DF), which consists of an upward gravel filter and a downward filter of clinoptilolite, and disinfection by ozonation. The system was evaluated using physicochemical and microbiological parameters. The lowest ozone dose (0.4 mg L-1) indicated possible oxidation of fractions of biodegradable organic matter with BOD removals above 95%. Higher ozone concentrations (5.0 and 7.0 mg L-1) improved COD removal and total nitrogen removal. Regarding microbiological parameters, over 87% E. coli and 89% total coliforms could be removed only with the use of DF, while total inactivation was observed using doses above 5.0 mg L-1 ozone. The results showed that following the proposed treatment, the effluent treated with the DF/Ozonation combination meets the guidelines for reuse in toilets, irrigation of orchards, cereals, pastures, and other crops through runoff or by punctual irrigation system according to the NBR 13969/97. According to these results, DF using clinoptilolite followed by ozonation is a promising technology for the anaerobic reactor effluent post-treatment.