Minimum requirements for trace metals (iron, nickel, cobalt, and zinc) in thermophilic and mesophilic methane fermentation from glucose.

The minimum requirements for four essential trace metals were examined in both thermophilic and mesophilic methane fermentation of glucose. The minimum requirement here was defined as the amount that supports the effluent soluble chemical oxygen demand (COD) of 1000 mg/ L or less for the duration of several times the hydraulic retention time (HRT). For this purpose, completely mixed reactors were run semi-continuously at 5 days HRT, with 10 g/L substrate COD.

Elutriated acid fermentation of municipal primary sludge.

The performance of a novel fermentation process, adopting a sludge blanket type configuration, for higher hydrolysis/acidogenesis of the municipal primary sludge was investigated under batch and semi-continuous conditions with varying pH and temperature. This acid elutriation slurry reactor provided higher system performance with a short HRT (5d) and higher acidogenic effluent quality under pH 9 and thermophilic (55 degrees C) conditions. The hydrolysis of the sludge was revealed to be significantly dependent on seasonal effects for sludge characteristics but with little impact on acidogenesis.

The role of pH in mesophilic anaerobic sludge solubilization.

The effect of pH on anaerobic solubilization of synthetic sludge (dog food) and domestic primary sludge was investigated and compared. Anaerobic solubilization was carried out in Continuously Stirred Anaerobic Reactors at mesophilic temperature (35 degrees C) and pH was fixed at 6.5 (pH-controlled).

Acetoclastic methanogenic activity measurement by a titration bioassay.

A titration bioassay, designed to accurately determine the activity of acetoclastic methanogens, is described that also allows evaluation of inhibition due to potential toxicants on the active biomass. The instrument is made of a pH-stat connected to an anaerobic batch reactor. Acetate is blended and mixed with anaerobic sludge in the reactor where a 1:1 N2 and CO2 mixture is sparged at the beginning of each test.