Elemental sulfur-based autotrophic denitrification in stoichiometric S0/N ratio: Calibration and validation of a kinetic model.

The inclusion of S0 hydrolysis in a kinetic model of autotrophic denitrification has been recently proposed; however the model has not been calibrated or validated yet. Thus, a new methodology was developed and applied to calibrate and validate this kinetic model for the first time. An inoculum adapted from a poultry wastewater treatment plant at stoichiometric S0/NO3- ratio was used. The model was calibrated with batch data (initial nitrate concentrations of 50 and 6.25 mg NO3--N/L) at an S0/N ratio = 2.29 mg S/mg N and validated with seven different batch data. The sensitivity analysis showed that the most sensitive parameters are related to S0 hydrolysis. The kinetic model was successfully calibrated with the new methodology and validated, with Theil inequality coefficient values lower than 0.21. Thus, the proposed model and methodology were proved to be well suited for the simulation of elemental sulfur-based autotrophic denitrification in batch systems.

Application of zeolites for biological treatment processes of solid wastes and wastewaters - A review.

This review reports the use of zeolites in biological processes such as anaerobic digestion, nitrification, denitrification and composting, review that has not been proposed yet. It was found that aerobic processes (activated sludge, nitrification, Anammox) use zeolites as ion-exchanger and biomass carriers in order to improve the seattlebility, the biomass growth on zeolite surface and the phosphorous removal. In the case of anaerobic digestion and composting, zeolites are mainly used with the aim of retaining inhibitors such as ammonia and heavy metals through ion-exchange. The inclusion of zeolite effect on mathematical models applied in biological processes is still an area that should be improved, including also the life cycle analysis of the processes that include zeolites. At the same time, the application of zeolites at industrial or full-scale is still very scarce in anaerobic digestion, being more common in nitrogen removal processes.

Use of solid residue from thermal power plant (fly ash) for enhancing sewage sludge anaerobic digestion: Influence of fly ash particle size.

The influence of fly ash particle size on methane production and anaerobic biodegradability was evaluated. Assays with different fly ash particle sizes (0.8-2.36mm) at a concentration of 50mg/L were ran under mesophilic conditions. In anaerobic processes operating with fly ash, greater removal of both volatile total and suspended solids, chemical oxygen demand (total and soluble) was achieved, with an increase of methane production between 28% and 96% compared to the control reactors. The highest increase occurred at ash particles sizes of 1.0-1.4mm. The metal concentrations in the digestates obtained after anaerobic digestion of sewage sludge are far below those considered as limiting for the use of sludge in soils.

Simultaneous nitrate and organic matter removal from salmon industry wastewater: the effect of C/N ratio, nitrate concentration and organic load rate on batch and continuous process.

Although simultaneous denitrification-anaerobic digestion has been studied extensively, the use of salmon effluents as organic matter source has received little attention. This study evaluated the effect of C/N ratio, nitrate concentration, and organic load rate (OLR) on simultaneous nitrate and organic matter removal using salmon effluents. The study was carried out in a batch reactor with suspended biomass at 37 °C and pH 7.5, and in continuous biofilm tubular reactors at 37 °C fed with a mixture of a synthetic substrate and a saline protein-rich salmon-plant effluent. The results of the batch and continuous experiments showed that nitrate abatement was greater than 95% at all the studied C/N ratios, without effect of the C/N ratio on NO(3)(-)-N transformation and ammonia production. An increase of nitrate concentration increased organic matter consumption as well as the hydrolytic rate. The organic matter reduction varied between 88% and 40% in the continuous process. For a continuous process, the increase of the OLR decreases the removal of organic matter.

Organic and nitrogenous matter effects on the denitrification of saline and protein-rich effluents.

The separate effect of protein concentration, nitrate concentration and carbon/nitrogen (C/N) ratio on the rate and efficiency of nitrate reduction was studied in batch reactors fed with a mixture of a synthetic substrate and a saline protein-rich salmon-plant effluent. At a constant nitrate concentration (40 mg L(-1)), the specific rate of nitrate removal decreased by 60% with increasing initial protein concentration (392 to 1900 mg L(-1)) and ammonification prevailed under these conditions; meanwhile at a constant protein concentration (1104 mg L(-1)), the specific rate of nitrate removal increased 58 times with increasing nitrate concentrations (0.5 to 78 mg L(-1)) and denitrification was the main route for nitrate reduction. The C/N ratio had an inverse effect on the specific rate of denitrification; the latter ranged from 227 to 563 [mg NO3(-)-N (g VSS d)(-1)] for a C/N ratio of 163 to 16 [mg TOC (total organic carbon) (mg NO3(-)-N)(-1)], respectively. On the other hand, the ammonia production rate was proportional up to a C/N ratio of 150.