First comparison of conventional activated sludge versus root-zone treatment for SARS-CoV-2 RNA removal from wastewaters: Statistical and temporal significance

Manish Kumar; Keisuke Kuroda; Madhvi Joshi; Prosun Bhattacharya; Damia Barcelo

doi:10.1016/j.cej.2021.130635

First comparison of conventional activated sludge versus root-zone treatment for SARS-CoV-2 RNA removal from wastewaters: Statistical and temporal significance

Chem Eng J. 2021 Dec 1:425:130635. doi: 10.1016/j.cej.2021.130635. Epub 2021 Jun 14.

Authors

Manish Kumar^{1

2}, Keisuke Kuroda³, Madhvi Joshi⁴, Prosun Bhattacharya⁵, Damia Barcelo⁶

Affiliations

¹ Discipline of Earth Science, Indian Institute of Technology Gandhinagar, Gujarat 382 355, India.
² Kiran C Patel Centre for Sustainable Development, Indian Institute of Technology Gandhinagar, Gujarat, India.
³ Department of Environmental and Civil Engineering, Toyama Prefectural University, Imizu 939 0398, Japan.
⁴ Gujarat Biotechnology Research Centre (GBRC), Sector- 11, Gandhinagar, Gujarat 382 011, India.
⁵ Department of Sustainable Development, Environmental Science and Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
⁶ Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, and Catalan Institute for Water Research (ICRA)-CERCA, Girona, Spain.

Abstract

In the initial pandemic phase, effluents from wastewater treatment facilities were reported mostly free from Severe Acute Respiratory Coronavirus 2 (SARS-CoV-2) RNA, and thus conventional wastewater treatments were generally considered effective. However, there is a lack of first-hand data on i) comparative efficacy of various treatment processes for SARS-CoV-2 RNA removal; and ii) temporal variations in the removal efficacy of a given treatment process in the backdrop of active COVID-19 cases. This work provides a comparative account of the removal efficacy of conventional activated sludge (CAS) and root zone treatments (RZT) based on weekly wastewater surveillance data, consisting of forty-four samples, during a two-month period. The average genome concentration was higher in the inlets of CAS-based wastewater treatment plant (WWTP) in the Sargasan ward (1.25 × 10³ copies/ L), than that of RZT-based WWTP (7.07 × 10² copies/ L) in an academic institution campus of Gandhinagar, Gujarat, India. ORF 1ab and S genes appeared to be more sensitive to treatment i.e., significantly reduced (p < 0.05) than N genes (p > 0.05). CAS treatment exhibited better RNA removal efficacy (p = 0.014) than RZT (p = 0.032). Multivariate analyses suggested that the effective genome concentration should be calculated based on the presence/absence of multiple genes. The present study stresses that treated effluents are not always free from SARS-CoV-2 RNA, and the removal efficacy of a given WWTP is prone to exhibit temporal variability owing to variations in active COVID-19 cases in the vicinity and genetic material accumulation over the time. Disinfection seems less effective than the adsorption and coagulation processes for SARS-CoV-2 removal. Results stress the need for further research on mechanistic insight on SARS-CoV-2 removal through various treatment processes taking solid-liquid partitioning into account.

Keywords: COVID-19; Conventional activated sludge process; Environmental Surveillance; Root-zone treatment; SARS-CoV-2; Wastewater based epidemiology.