Comparative investigation on integrated vertical-flow biofilters applying sulfur-based and pyrite-based autotrophic denitrification for domestic wastewater treatment

Two parallel biofilters applying sulfur/pyrite-based autotrophic denitrification were investigated for removing COD, TP and TN by a coordinated process. Results demonstrated good performance by removing 86.32% vs 87.14% COD and 92.56% vs 89.65% NH4+-N. Biofilter with sulfur (BS) was superior on nitrate (89.74% vs 80.72%) and TN removal (83.18% vs 70.42%) while biofilter with pyrite (BP) was better on TP removal (82.58% vs 77.40%) and maintaining sulfate (27.56 mg L-1 vs 41.55 mg L-1) and pH (7.13 vs 6.31). Water-permeable adsorbents lowered clogging risk and buffered loading. Clone library revealed reasons of diversities, pH variation and sulfate accumulation of both biofilters. Sulfur was efficient on denitrification but whose byproducts were troublesome, pyrite produced less byproduct but which was sensitive to organics. This research was the first attempt to systematically compare two promising alternatives and their merits/demerits for rural wastewater on-site treatment. (C) 2016 Elsevier Ltd. All rights reserved.