Performance of Anaerobic Hybrid Reactor with Post-Treatment in Intermittent Flow Sand Filter: a Sulfide-Oxidizing Bioprocess for the Treatment of Sanitary Sewage Using Nitrate as Electron Acceptor

Abstract

The aim of the study was to evaluate the oxidation of sulfides using nitrate as an electron acceptor in an anaerobic hybrid reactor (AHR) connected to an intermittent flow sand filter (IFSF) for post-treatment. The study was carried out in four phases in which the AHR was fed with 100% raw sewage (phase I) followed by phases II, III and IV involving different proportions of raw sewage and recycled nitrified IFSF effluent (83:17, 67:33 and 50:50, respectively). The results showed that 41% of the oxidized forms of sulfur were accumulated in the anaerobic phase with 31% in the form of sulfate and 10% as elemental sulfur. Increased proportions of nitrified IFSF effluent into the AHR favored denitrification and afforded up to 38% removal of nitrogen during the anaerobic stage and 46% in the final effluent. The removal efficiency of total dissolved sulfide by the system was up to 99.3% in phase IV, the influent of which contained the highest proportion of nitrified effluent. It is concluded that the combination of AHR and IFSF offers excellent conditions for the removal of chemical oxygen demand, nitrogen and sulfides from sanitary sewage using nitrate as an electron acceptor. Furthermore, the proposed treatment system represents a low-cost and energy-saving approach that addresses the anaerobic digestion of biosolids as well as the control of malodorous gas formation.