Anammox cultivation in a closed sponge-bed trickling filter.

A feasibility study was carried out to assess the cultivation of Anammox bacteria in lab-scale closed sponge-bed trickling filter (CSTF) reactors, namely: CSTF-1 at 20°C and CSTF-2 at 30°C. Stable conditions were reached from day 66 in CSTF-2 and from day 104 in CSTF-1. The early stability of CSTF-2 is attributable to the influence of temperature; nevertheless, by day 405, the nitrogen removal performed by CSTF-1 increased up to similar values of CSTF-2. The maximum total nitrogen removal efficiency was 82% in CSTF-1 and 84% in CSTF-2. After more than 400 days of operation, CSTF-1 and CSTF-2 were capable to attain a total nitrogen removal efficiency of 74±5% and 78±4% with a total nitrogen conversion rate of 1.52 and 1.60kg-N/m(sponge)(3)d, respectively. The proposed technology could be a suitable alternative for mainstream nitrogen removal in post-treatment units via the Anammox conversion pathway.

Autotrophic nitrogen removal over nitrite in a sponge-bed trickling filter.

Partial nitritation in sponge-bed trickling filters (STF) under natural air circulation was studied in two reactors: STF-1 and STF-2 operated at 30°C with sponge thickness of 0.75 and 1.50cm, respectively. The coexistence of nitrifiers and Anammox bacteria was obtained and attributed to the favorable environment created by the reactors' design and operational regimes. After 114days of operation, the STF-1 had an average NH4(+)-N removal of 69.3% (1.17kgN/m(3)sponged) and a total nitrogen removal of 52.2% (0.88kgN/m(3)sponged) at a Nitrogen Loading Rate (NLR) of 1.68kgN/m(3)sponged and Hydraulic Retention Time (HRT) of 1.71h. The STF-2 showed an average NH4(+)-N removal of 81.6 % (0.77kgN/m(3)sponged) and a total nitrogen removal of 54% (0.51kgN/m(3)sponged), at an NLR of 0.95kgN/m(3)sponged and HRT of 2.96h. The findings suggest that autotrophic nitrogen removal over nitrite in STF systems is a feasible alternative.