Comparative evaluation of advanced oxidation processes (AOPs) for reducing SARS-CoV-2 viral load from campus sewage water

Abstract

Presence of SARS-CoV-2 in wastewater is a major concern as the wastewater meets rivers and other water bodies and is used by the population for various purposes. Hence it is very important to treat sewage water in an efficient manner in order to reduce the public health risk. In the present work, various advanced oxidation processes (AOPs) have been evaluated for disinfection of SARS-CoV-2 from sewage water collected from STP inlet of academic institutional residential. The sewage water was subjected to ten AOPs, which include Ozone (O₃), Hydrodynamic cavitation (HC), Ultraviolet radiation (UV), and their hybrid combinations like HC/O₃, HC/O₃/H₂O₂, HC/H₂O_2, O₃/UV, UV/H₂O₂, UV/H₂O₂/O_3, and O₃/H₂O₂ to reduce SARS-CoV-2 viral load. Further, AOP treated sewage water was subjected to total nucleic acid isolation followed by RT-qPCR for viral load estimation. The sewage water treatment techniques were evaluated based on their viral concentration-reducing efficiency. It was found that ozone and ozone-coupled hybrid AOPs showed the most promising result with more than 98 % SARS-CoV-2 viral load reducing efficiency from sewage water. Interestingly, the best six AOPs used in this study significantly reduced both the SARS-CoV-2 and PMMoV (faecal indicator) viral load and improved water quality in terms of increasing DO and decreasing TOC.

Keywords: AOPs and hybrid AOPs; Hydrodynamic cavitation; Ozonation; PMMoV; SARS-CoV-2; Sewage water treatment.

Graphical abstract

Fig. 1

Experimental scheme illustrating treatment of raw sewage water samples (from STP) with different treatment techniques for reduced SARS-Cov-2 viral load.

Fig. 2

Setup for hydrodynamic cavitation and its hybrid techniques.

Fig. 3

Setup for UV/ozonation and its hybrid processes.

Fig. 4

Bar plot illustrating evaluation of disinfecting efficiency of different AOPs for reduced viral load. (Experimental conditions: 8 gm/hr ozone flow rate, 400 mg/L H₂O₂ and ultraviolet radiation (254 nm) were set for 90 min in respective AOPs treatments on X-axis.).

Fig. 5

Variations of initially screened treatment techniques using raw sewage water samples. The Y-axis at the left shows the viral load (copies/µL) of raw sewage water (red bar), and the secondary Y-Axis axis depicts the viral load (copies/µL) of AOP treated sewage water.

Fig. 6

Graphical representation of the SARS-CoV-2 viral load reduction for the three different sewage water samples collected on different days using six best AOP techniques. The Y-axis at the left shows the viral load (copies/µL) of raw sewage water (checkered pattern bar), and the secondary axis represents the viral load (copies/µL) of AOP treated water.

Fig. 7

PMMoV RNA (copies/µL) reduction. After treatment of the three different sewage water samples collected using the six best AOP techniques.