Abstract

The partial nitritation-anammox (PN-AMX) process applied to wastewaters with high NaCl concentration was studied until now using simulated media, without considering the effect of organic matter concentration and the shift in microbial populations. This research work presents results on the application of this process to the treatment of saline industrial wastewater. Obtained results indicated that the PN-AMX process has the capability to recover its initial activity after a sudden/acute salt inhibition event (up to 16 g NaCl/L). With a progressive salt concentration increase for 150 days, the PN-AMX process was able to remove the 80% of the nitrogen at 7–9 g NaCl/L. The microbiological data indicated that NaCl and ammonia concentrations and temperature are important factors shaping PN-AMX communities. Thus, the NOB abundance (Nitrospira) decreases with the increase of the salt concentration, while heterotrophic denitrifiers are able to outcompete anammox after a peak of organic matter in the feeding.

Abstract

The concerns related to the environmental impact related to energy production from fossil fuel are increasing. In this context, the substitution of fossil fuel based energy by bio-energy can be an effective solution. In this study, the production of electricity and heat in Italy in a combined heat and power plant (CHP) based on an Organic Rankine Cycle (ORC) turbine from wood based biomass both from forest and agricultural activities has been analysed considering four potential alternative scenarios to the current energy status: biomass from very short rotation forestry (VSRF) poplar and willow stands as well as residues from natural forests and from traditional poplar plantations. The evaluation has been performed by applying Life Cycle Assessment (LCA) method and an attributional cradle-to-gate approach has been followed. The expected savings of greenhouse gases emission and fossil fuels demand have been quantified, as well as derived emissions of toxic pollutants and substances responsible for acidification, eutrophication and photochemical oxidant formation.The results have been also compared with the conventional Italian scenario considering the current Italian electricity profile and heat production from natural gas. Among the different scenarios, due to the lower transport distance, the use of biomass from traditional poplar plantation residues shows the lowest impact. The biomass combustion emissions are the main hotspot for several evaluated impact categories (e.g., particulate matter formation, human toxicity). In fact, when the produced bio-energy is compared to the reference system (i.e., electricity produced under the Italian electric profile) the results do not favor bio-energy systems. The results reported in this study support the idea that forest residues would be an interesting and potential feedstock for bio-energy purposes although further research is required specifically with the aim of optimizing biomass supply distances.