Performance of Full-Scale Thermophilic Membrane Bioreactor and Assessment of the Effect of the Aqueous Residue on Mesophilic Biological Activity

Maria Cristina Collivignarelli,Francesca Maria Caccamo,Marco Carnevale Miino,Alessandro Abbà,Marco Baldi

doi:10.3390/w13131754

Maria Cristina Collivignarelli, Francesca Maria Caccamo + Show 3 more

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https://doi.org/10.3390/w13131754

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Journal: Water	Publication Date: Jun 25, 2021
Citations: 11	License type: CC BY 4.0

Affiliation: University of Pavia, University of Brescia

Abstract

To date, the management of high-strength wastewater represents a serious problem. This work aims to evaluate the performance on chemical pollutants and on sludge production of one of the two full-scale thermophilic membrane bioreactors (ThMBRs) currently operational in Italy, based on monitoring data of the last two and a half years. Removal yields on COD, N-NOx, non-ionic and anionic surfactants (TAS and MBAS), increased with the input load up to 81.9%, 97.6%, 94.7%, and 98.4%, respectively. In the period of stability, a very low value of sludge production (0.052 kgVS kgCOD−1) was observed. Oxygen uptake rate (OUR) tests allowed us to exclude the possibility that mesophilic biomass generally exhibited any acute inhibition following contact with the aqueous residues (ARs), except for substrates that presented high concentrations of perfluoro alkyl substances (PFAS), cyanides and chlorides. In one case, nitrifying activity was partially inhibited by high chlorides and PFAS concentration, while in another the substrate determined a positive effect, stimulating the phenomenon of nitrification. Nitrogen uptake rate (NUR) tests highlighted the feasibility of reusing the organic carbon contained in the substrate as a source in denitrification, obtaining a value comparable with that obtained using the reference solution with methanol. Therefore, respirometric tests proved to be a valid tool to assess the acute effect of AR of ThMBR on the activity of mesophilic biomass in the case of recirculation.

Highlights

To date, the management of high-strength wastewater (WW) represents a very serious problem [1]
The food:microorganism (F/M) ratio was 0.030 ± 0.003 gCOD gVS −1 d−1. This low ratio is related to the high recalcitrance of the organic substance present in the high-strength WW fed to thermophilic membrane bioreactors (ThMBRs), which, on the other hand, would not be treatable with a conventional mesophilic process
With an organic loading rate (OLR) between 1.5 and 2 kg m−3 d−1, the COD removal efficiency was on average 78.2%. This efficiency increased up to 81.9% in the presence of an OLR greater than 3 kg m−3 d−1 (Figure 2a). These results confirm our previous findings: almost 77% of COD fed was effectively removed by the other realscale ThMBR plant operating in Italy [35]

Summary

Introduction

The management of high-strength wastewater (WW) represents a very serious problem [1]. Heavy metals [11,12] These WWs must be treated in special treatment lines built on site or located in authorized WWTPs. Chemical–physical treatments (e.g., coagulation-flocculation) are the most commonly used because of the recalcitrance of these pollutants which tend to inhibit the activity of the biomass with which they come into contact [13,14,15]. Coagulation–flocculation required the use of chemical reagents and produced large quantities of chemical sludge in which some of these pollutants (e.g., heavy metals) are concentrated [16,17] This aspect causes an increase in costs and is against the principle of the circular economy of minimizing the use of resources and optimizing the recovery of materials [18,19,20]

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