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Mannucci A.,University of Florence | Munz G.,University of Florence | Mori G.,Consorzio Cuoiodepur | Lubello C.,University of Florence | Oleszkiewicz J.A.,University of Manitoba
Frontiers of Environmental Science & Engineering | Year: 2014

The aim of this work is to identify the range of applicability of Arrhenius type temperature dependence for Ammonia Oxidizing Bacteria (AOB) subjected to temperature time gradients through continuous titrimetric tests. An innovative online differential titrimetric technique was used to continuously monitor the maximum biologic ammonia oxidation rate of the biomass selected in a pilot scale membrane bioreactor, as a function of temperature time gradients. The monitoring technique is based on the measurement of alkalinity and hydrogen peroxide consumption rates in two parallel reactors operated in nonlimiting substrate conditions for AOB; both reactors were continuously fed with mixed liquor and in one of them AOB were inhibited with allylthiourea. The effects of temperature decrease rates in the range 1 to 4°C·h-1 were evaluated by controlling the titrimetric reactor in the temperature range 10°C-20°C. The dependence of growth kinetics on temperature time gradients and the range of applicability of Arrhenius model for temperature dependency of AOB growth kinetics were assessed. The Arrhenius model was found to be accurate only with temperature gradients lower than 2°C·h-1. The estimated Arrhenius coefficients (θ) were shown to increase from 1.07 to 1.6 when the temperature decrease rate reached 4°C·h-1. © 2014 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Mannucci A.,University of Florence | Munz G.,University of Florence | Mori G.,Consorzio Cuoiodepur | Lubello C.,University of Florence
Environmental Engineering and Management Journal | Year: 2014

A pilot scale Upflow Anaerobic Filter (UAF) treating tannery wastewaters was operated for 160 days. The UAF was fed with low COD/SO4 2- ratio (SO4 2- = 1810 mg L-1, CODtotal= 2530 mg L-1) for the investigation of sulphate and COD removal as a function of substrates limitation and ammonia and sulphide inhibition. Sulphate-reducing bacteria (SRB) out-competed methanogenic bacteria due to the low influent COD/SO4 2- ratio, the high concentration of sulphide and the presence of inhibiting compounds in tannery wastewater. An average sulphate removal of 53% and an average COD removal of 42% were obtained. Ammonia and sulphide concentrations were found to play a major role in the process, and their effect was quantified. A simplified mathematical model was calibrated under semi-steady conditions and no substrate limitation, and used to describe sulphide and ammonia inhibition. Half-inhibition constants for ammonia (KNH4) and sulphide (KHS) of 180 mg L-1and 480 mg L-1, respectively, were obtained. No improvements of the biodegradability between the untreated tannery wastewater and the UAF effluent were observed through respirometric tests.

Mannucci A.,University of Florence | Munz G.,University of Florence | Mori G.,Consorzio Cuoiodepur | Lubello C.,University of Florence
Chemosphere | Year: 2012

A pilot scale test on a biotrickling filter packed with polyurethane foam cubes was carried out for 110d at high volumetric mass load (up to 280gm bed -3h -3) with the aim of studying the accumulation of solids in the treatment of H 2S.Removal rate up to 245gm bed -3h -1 was obtained; however, an accumulation of gypsum, elemental sulphur and, above all, inert biomass was identified as the cause of an increased pressure drop over the long term. A mathematical model was applied and calibrated with the experimental results to describe the accumulation of biomass. The model was capable of describing the accumulation of solids and, corresponding to a solids retention time of 50d, the observed yield resulted in 0.07g of solids produced g -1H 2S removed. Respirometric tests showed that heterotrophic activity is inhibited at low pH (pH<2.3), and the contribution to biomass removal through decay was negligible. © 2012 Elsevier Ltd.

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