Microbial community and performance of a partial nitritation/anammox sequencing batch reactor treating textile wastewater

Implementation of onsite bioremediation technologies is essential for textile industries due to rising concerns in terms of water resources and quality. Partial nitritation-anaerobic ammonium oxidation (PN/A) processes emerged as a valid, but unexplored, solution. In this study, the performance of a PN/A pilot-scale (9 m3) sequencing batch reactor treating digital textile printing wastewater (10–40 m3 d−1) was monitored by computing nitrogen (N) removal rate and efficiencies. Moreover, the structure of the bacterial community was assessed by next generation sequencing and quantitative polymerase chain reaction (qPCR) analyses of several genes, which are involved in the N cycle. Although anaerobic ammonium oxidation activity was inhibited and denitrification occurred, N removal rate increased from 16 to 61 mg N g VSS−1 d−1 reaching satisfactory removal efficiency (up to 70%). Ammonium (18–70 mg L−1) and nitrite (16–82 mg L−1) were detected in the effluent demonstrating an unbalance between the aerobic and anaerobic ammonia oxidation activity, while constant organic N was attributed to recalcitrant azo dyes. Ratio between nitrification and anammox genes remained stable reflecting a constant ammonia oxidation activity. A prevalence of ammonium oxidizing bacteria and denitrifiers suggested the presence of alternative pathways. PN/A resulted a promising cost-effective alternative for textile wastewater N treatment as shown by the technical-economic assessment. However, operational conditions and design need further tailoring to promote the activity of the anammox bacteria

Assessment of anammox, microalgae and white-rot fungi-based processes for the treatment of textile wastewater

The treatability of seven wastewater samples generated by a textile digital printing industry was evaluated by employing 1) anammox-based processes for nitrogen removal 2) microalgae (Chlorella vulgaris) for nutrient uptake and biomass production 3) white-rot fungi (Pleurotus ostreatus and Phanerochaete chrysosporium) for decolorization and laccase activity. The biodegradative potential of each type of organism was determined in batch tests and correlated with the main characteristics of the textile wastewaters through statistical analyses. The maximum specific anammox activity ranged between 0.1 and 0.2 g N g VSS-1 d-1 depending on the sample of wastewater; the photosynthetic efficiency of the microalgae decreased up to 50% during the first 24 hours of contact with the textile wastewaters, but it improved from then on; Pleurotus ostreatus synthetized laccases and removed between 20-62% of the colour after 14 days, while the enzymatic activity of Phanerochaete chrysosporium was inhibited. Overall, the findings suggest that all microbes have great potential for the treatment and valorisation of textile wastewater after tailored adaptation phases. Yet, the depurative efficiency can be probably enhanced by combining the different processes in sequence

Partial nitritation/anammox process treating digital textile printing effluent: lab-scale experimental and modelling trial

In recent years, single-stage partial nitritation/anammox process emerged as a sustainable solution for nitrogen removal from industrial wastewater. However, the process application often requires case-specific adaptation. In the present study, process application as a decentralized treatment to digital textile printing wastewater was assessed. The biomass was inoculated in a lab-scale reactor and progressively acclimated until reaching the target loading rate. The experimental campaign was characterized by the occurrence of biomass inhibition phenomena causing process instability. At quasi-stable conditions, total nitrogen removal was in compliance with regulations on discharge in the public sewer (100 mgN/L). Process modelling could simulate experimental data, also indicating its importance for process monitoring and control practices

Il progetto LIFE DeNTreat: rimozione autotrofa dell’azoto nei reflui da stampa tessile digitale con processo PN/A

La stampa tessile digitale (STD) è una tecnologia in rapida diffusione nel settore della nobilitazione tessile, grazie alla sua capacità di rendere il processo di stampa molto più flessibile e veloce. Tuttavia, le acque reflue provenienti dai bagni di risciacquo sono ricche di azoto (fino a 600 mg/L), a causa dell’uso massiccio di urea utilizzata per preparare il tessuto alla stampa e facilitare la penetrazione del colore nella fibra. Una tale elevata concentrazione impedisce lo scarico diretto dei reflui da STD nei corpi idrici o nelle fognature pubbliche ed è necessario uno specifico pretrattamento in loco. I reflui da STD sono caratterizzati da un rapporto COD/N < 4 che è ancora più basso se si considera il COD biodegradabile (bCOD, pari al 30%-50% del COD totale). Il processo di Nitritazione Parziale/Anammox (PN/A) può offrire un’alternativa economicamente vantaggiosa rispetto ai processi convenzionali di rimozione dell’azoto, che richiederebbero considerevoli dosaggi di substrato carbonioso biodegradabile. Una prima fase della ricerca, preliminare al progetto LIFE DeNTreat, ha verificato la fattibilità del processo PN/A sui reflui da STD attraverso l’utilizzo di prove manometriche in batch e prove preliminari su impianto pilota da laboratorio SBR di 2 L. Successivamente, nel progetto LIFE DeNTreat sono state studiate le efficienze di rimozione dell’azoto sia sul reattore a scala di laboratorio sia in un reattore SBR di 12 m3 su scala dimostrativa. I dati riportati in questo lavoro hanno dimostrato risultati promettenti, nonostante la variabilità delle caratteristiche dei reflui e il difficile controllo delle condizioni operative durante il processo.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

Nitrogen Removal from Ink-Jet Textile Printing Wastewater by Autotrophic Biological Process: First Results at Lab and Pilot Scale

Digital textile printing is a rapidly spreading technology in the textile finishing industry due to the great advantages in making printing much more flexible. On the other hand, wastewater originating from rinsing baths are rich in nitrogen (up to 600 mg/L of ammonium nitrogen) due to the massive use of urea in conditioning the textile before printing. Such high concentration prevents the direct discharge into water bodies or even in public sewers and specific dedicated on-site pre-treatment is necessary. PN/anammox processes can offer an economically feasible alternative to conventional nitrogen removal processes, as these require a COD/N ratio of at least 8. The first results of the EU-LIFE DeNTreat project, consisting in the start-up of PN/anammox lab and pilot scale reactors are promising in spite of the variability of the characteristics of the wastewater originating from rinsing digitally printed textiles