THE LIFE DENTREAT PROJECT: AUTOTROPHIC REMOVAL OF NITROGEN FROM WASTEWATERS FROM DIGITAL TEXTILE PRINTING WITH THE PN/A PROCESS

Abstract

Digital textile printing (STD) is a rapidly spreading technology in the textile finishing sector, thanks to its ability to make the printing process much more flexible and faster. However, the wastewater from the rinsing baths is rich in nitrogen (up to 600 mg/L), due to the massive use of urea used to prepare the fabric for printing and facilitate the penetration of color into the fiber. Such a high concentration prevents the direct discharge of STD waste into water bodies or public sewers and a specific pre-treatment on site is required. STD wastewater is characterized by a COD/N ratio < 4, which is even lower if we consider the biodegradable COD (bCOD, 30% - 50% of the total COD). The Partial Nitritation/Anammox (PN/A) process can offer a cost-effective alternative to conventional nitrogen removal processes, which would require considerable dosages of biodegradable carbonaceous substrate. The first results of the LIFE DeNTreat project verified the feasibility of the PN/A process on STD wastewater through the use of batch manometric tests and preliminary tests on a 2 L SBR laboratory pilot plant. Subsequently, in the project LIFE DeNTreat, nitrogen removal efficiencies were investigated both on the laboratory scale reactor and in a 12 m³ SBR reactor on a demonstration scale. The data reported in this work have shown promising results, despite the variability of the characteristics of the wastewater and the difficult control of operating conditions during the process.