The application of anaerobic digestion technology is growing worldwide because of its economic and environmental benefits. As a consequence, a number of studies and research activities dealing with the determination of the biogas potential of solid organic substrates have been carrying out in the recent years. Therefore, it is of particular importance to define a protocol for the determination of the ultimate methane potential for a given solid substrates. In fact, this parameter determines, to a certain extent, both design and economic details of a biogas plant. Furthermore, the definition of common units to be used in anaerobic assays is increasingly requested from the scientific and engineering community. This paper presents some guidelines for biomethane potential assays prepared by the Task Group for the Anaerobic Biodegradation, Activity and Inhibition Assays of the Anaerobic Digestion Specialist Group of the International Water Association. This is the first step for the definition of a standard protocol.

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In this work the autotrophic nitrogen removal was carried out at moderately low temperatures using two configurations: a) two-units one comprising a SHARON reactor coupled to an Anammox SBR and b) single-unit one consisting of a granular SBR performing the CANON process. At 20°C the two-units system was limited by the Anammox step and its nitrogen removal capacity was around ten times lower than the CANON system (0.08 g N/(L d) versus 1 g N/(L d)). When the CANON system was operated at 15°C the average removed nitrogen loading rate decreased to 0.2 g N/(L d). The CANON system was operated in order to limit the ammonia oxidation rate to avoid nitrite inhibition of Anammox bacteria. Since both, temperature and dissolved oxygen (DO) concentration regulate ammonia oxidizing bacteria activity, once the temperature of the reactor is decreased the DO concentration must be decreased to avoid the deeper oxygen penetration inside the granule which could cause inhibition of Anammox bacteria by oxygen and/or nitrite.

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The effects of two broad-spectrum antibiotics, chloramphenicol and oxytetracycline hydrochloride, on the microbial activity and biofilm stability of a mixed nitrifying culture were studied. These antibiotics are present in some wastewaters generated in cattle farms or pharmaceutical industries. A 1-L fermentor, in which nitrifiers grew both in suspension and in a biofilm, was used during the experiments. Chloramphenicol (10-250 mg/L) barely had any effect on biofilm stability and nitrification. Ammonia was fully oxidized to nitrate. However, oxytetracycline caused biofilm sloughing at concentrations of 10 mg/L, but nitrification was not inhibited at antibiotic concentrations up to 100 mg/L. When the concentration of oxytetracycline chlorohydrate was increased stepwise from 100 to 250 mg/L, nitrification was inhibited by 50%. The dissolved organic carbon measurements in both the influent and effluent showed that the antibiotics were neither mineralized by the mixed nitrifying culture nor accumulated in the system. Furthermore, the microbial tests did not reveal the presence of active antibiotics in the effluent. This fact indicates that both cloramphenicol and oxytetracycline were degraded by the nitrifying sludge but not mineralized.