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Poultry litter (PL) was pre-treated in order to reduce its nitrogen content and to increase the C/N ratio. The pre-treatment consisted of a first anaerobiosis phase of about 60 days in order to accumulate ammonia nitrogen, followed by an ammonia stripping phase by heating the substrate at 80 °C for 24 h. The digestion was performed with PL and pre-treated PL (TPL) after ammonia stripping as mono-substrate under four total solids loads, i.e. 5%, 10%, 15% and 20%. The TPL after ammonia stripping displayed lower ammonia (62–73%) and VFA (41–65%) concentrations compared to digesters with raw PL, while bio-methane yield increased about 8–124%. Bio-methane yields in the series with TPL after ammonia stripping were about 193, 196, 215 and 147 L CH 4 /kg COD , based on the COD added, for 5%, 10%, 15% and 20% TS load, respectively. The results indicate that lowering nitrogen content using the suggested process improves bio-methane yields significantly. [ABSTRACT FROM AUTHOR]

Abstract: Up-flow oxygen-controlled biofilm reactors equipped with a non-woven fabric support were used as a single reactor system for autotrophic nitrogen removal based on a combined partial nitrification and anaerobic ammonium oxidation (anammox) reaction. The up-flow biofilm reactors were initiated as either a partial nitrifying reactor or an anammox reactor, respectively, and simultaneous partial nitrification and anammox was established by careful control of the aeration rate. The combined partial nitrification and anammox reaction was successfully developed in both biofilm reactors without additional biomass inoculation. The reactor initiated as the anammox reactor gave a slightly higher and more stable mean nitrogen removal rate of 0.35 (± 0.19) kg-Nm−3 d−1 than the reactor initiated as the partial nitrifying reactor (0.23 (± 0.16) kg-Nm−3 d−1). FISH analysis revealed that the biofilm in the reactor started as the anammox reactor were composed of anammox bacteria located in inner anoxic layers that were surrounded by surface aerobic AOB layers, whereas AOB and anammox bacteria were mixed without a distinguishable niche in the biofilm in the reactor started as the partial nitrifying reactor. However, it was difficult to efficiently maintain the stable partial nitrification owing to inefficient aeration in the reactor, which is a key to development of the combined partial nitrification and anammox reaction in a single biofilm reactor. [ABSTRACT FROM AUTHOR]