Potential spreading risks and disinfection challenges of medical wastewater by the presence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) viral RNA in septic tanks of Fangcang Hospital

Abstract

First report on disinfection performance for SARS-CoV-2 in medical wastewater • Incomplete removal of SARS-CoV-2 RNA under WHO guideline • High level of DBPs when SARS-CoV-2 is completed removed.

Where do we stand to oversee the coronaviruses in aqueous and aerosol environment? Characteristics of transmission and possible curb strategies

“…4 a). The foremost among pathways are: 1) inadequate collection and treatment of wastewater; 2) untreated sewage flowing directly into receiving aquatic bodies; and 3) even contaminated water production of industry and agriculture [35] , [71] , [72] , [73] . It is well accepted that the major exposure of human to water-related viruses is through unsafe water treatment [74] , [75] .…”

“… 20 May: 10-20(copies/L); 16 June: 0-167(copies/L) [44] France, Paris March 5 to April7, 2020 Municipal WW; 11 mL PowerFecal Pro kit on a QIAsymphony extractor,QIAGEN; PCR Inhibitor removal resin; Ct values 100% of positive rate (over 106(copies/L)) n.a. 75% of positive rate (6/8); (near 105(copies/L)) [25] China, Wuchang February 5 to March 10, 2020 Municipal WW; Grab sampling; 2.0 L; 4 °C EZ1 virus Mini kit; AgPath-ID™ One-Step RT-PCR Kit; Ct values Non-detected (After primary disinfection tank before septic tank) Preliminary disinfection tank + Septic tank (7.5 ± 2.8) × 10 3 to (14.7 ± 2.2) × 10 3 copies/L in the effluents of septic tanks [71] Spain, Ourense April 6 to April 21,2020 Municipal WW; 250 mL; 24h composite samples; 4 °C STARMag 96 x 4 Universal Cartridge Kit; RT-qPCR Allplex system™ 2019-nCoV; Ct values 100% of positive rate (5/5); Grit and sand separator, primary settler, SBR, Microfiltration Secondary effluent: 25% of positive rate (1/4); Finally effluent: No detection [34] Japan, Kofu March 17 and May 7, 202 Municipal WW; Grab sampling; 1.0 L; RNeasy PowerWater Kit; High-Capacity cDNA Reverse Transcription Kit; Ct values 4.0 × 103 to 8.2 × 10 4 copies/L CAS: primary sedimentation, aeration, final sedimentation, chlorination Secondary effluent: 1.4 × 10 2 to 2.5 × 10 3 copies/L [39] USA, Louisiana January to April, 2020 Municipal WW; 24h composite samples; -80 °C ZR Viral RNA Kit; High Capacity cDNA Reverse Transcription Kit; Ct values 13% of positive rate(2/15) n.a. None of the secondary treated and final effluent samples [40] Spain, Ourense April 6 to April 21, 2020 Sludge; 250 mL; 4 °C STARMag 96 x 4 Universal Cartridge Kit; RT-qPCR Allplex system™ 2019-nCoV; Ct values 41% of positive rate(14/34) in primary sludge, biologic sludge, and thickened sludge Gravity thickening and centrifuge, thermal hydrolysis, anaerobic digestion …”

“…One study reported that up to 26% of enveloped viruses were removed by solid settling [100] . However, other studies pointed out that organic matters and suspended solids could help protect and survive for coronaviruses [69] , [71] . A study stated that SARS-CoV-2 RNA was still detected in the wastewater after the primary settler process [34] .…”

“…However, the co-existing high concentration of organic compounds and suspended solids in wastewater would interfere with disinfection for the virus. During the COVID-19 outbreak in Wuhan, China, the treatment of medical wastewater containing SARS-CoV-2 viral RNA located at Wuchang Fangcang hospital, China, in which the wastewater was firstly pumped from toilets and showers into the preliminary disinfection tank, while adding 800 mg L -1 of sodium hypochlorite for disinfecting with contacting time of 1.5 h, then the SARS-CoV-2 viral RNA was not fully detected after this kind of preliminary disinfection process [71] . Thereafter, the wastewater was pumped into the septic tank.…”

“…It was surprising that the SARS-CoV-2 viral RNA was detected from the effluent sample of the septic tank. It is believed due to the suspended solids in the septic tank and thus noting that a small size of particles can shield viruses from disinfection [71] . It is noteworthy that chemical oxidants would mainly damage viral capsid proteins for disinfection, while the UV would damage the viral genome and proteins [114] , [115] .…”