The Testing Process Reveals the Transmission of the COVID-19 from Wards to the Sewage System
The article was reproduced with permission from the Journal of Water and Wastewater Engineering, and EnvGuide Team translated the Chinese article into English Version.
The environmental characteristics of transmission of the new coronavirus (COVID-19) have become a topic of concern for all parties involved in the prevention and control of the epidemic. Water-borne environments are not only an important carrier for virus transmission but also a major receptor for secondary environmental risks and ecological damage caused by epidemic prevention and control. Relevant scientific data is extremely lacking for whether the urban drainage pipeline network will become a hiding place for COVID-19 and form a transmission route for residual viruses, as well as whether there are hidden dangers in the sewage treatment plant. It is urgent to investigate and pay attention to these questions.
Academician Xu Zuxin, from School of Environmental Science and Engineering at Tongji University, was responsible for the special research task of “Control Strategy for Potential Transmission Risk Sources of Urban Sewage Collection and Treatment Systems”, conducting an assessment of the potential risks of urban drainage systems, in order to provide empirical data and collaboratively control the spread of the epidemic and secondary environmental risks.
- Sampling points and samples
Academician Xu Zuxin’s team, with the strong support of the Shanghai Public Health Clinical Center and other relevant units, selected the drainage pipelines at the designated quarantine hotel in Shanghai, the designated hospital for patients with COVID-19, and the urban sewage treatment plant at the end. The specific sampling points include wards, disinfection facilities, municipal pipeline networks, and sewage treatment plants. The samples from the COVID-19 patient centralized treatment hospital were taken from the ward drain and the sewage disinfection station drain (4 samples at each point); the samples of the suspected patient quarantine hotel were taken from sewage collection wells outside the hotel, with a total of 6 samples; in the municipal sewage pipeline network, samples were taken from inspection wells along the line, with 6 samples taken from each point; in the sewage treatment plant, samples were taken from the water inlet and outlet with 6 samples from each sampling point. A total of 44 samples are shown in Table 1 and Figure 1.
Table 1. Sampling point settings and number of samples
|Sampling point||Number of the sampling point||Sampling points and samples||Test items||Notes|
|1*6||Sediment samples from outdoor drainage wells||COVID-19||The toilet is disinfected with chlorine tablets|
|COVID-19 Hospital||2*4||Water out of ward drainage station and sewage station||COVID-19||Centralized disinfection of sewage|
|Hospital sewage municipal drainage pipe network||3*6||#2, #44 and #30 Inspection well||COVID-19||Halfway from hospital drainage to sewage treatment plant|
|Municipal sewage pipe end sewage treatment plant||2*6||Sewage plant water intake & sewage plant effluent||COVID-19||Routine disinfection of sewage treatment plants|
Figure 1. Results of sampling points on March 11
- Analytical method
Samples were then sent to the Scientific Research Center of Shanghai Public Health Center Laboratory for analysis. With the primers and probe sequences of the new coronavirus recommended by the Chinese Center for Disease Prevention, 1-2 ml of environmental samples were taken, and RNA was extracted using a universal biological automated nucleic acid sequence extractor along with real-time fluorescent RT-PCR technology to determine the new coronavirus nucleic acid sequence.
- Test results
The analysis of the results of 44 samples of the new coronavirus nucleic acid sequence is as follows:
- From patient centralized treatment hospital, nucleic acid sequence detection of the four samples in the sewage discharged was positive for coronavirus, indicating that the coronavirus can indeed enter the drainage facility through fecal sewage.
- No sample tested positive for the new coronavirus nucleic acid sequence from the outlet of hospital sewage treatment and disinfection station to the municipal drainage pipeline network and the downstream sewage treatment plant inlet and outlet. This shows that under the circumstances of strict disinfection and standard treatment, the coronavirus can be effectively inactivated.
- Since the sampling of the fixed-point quarantine hotel did not have a sewage disinfection device, the coronavirus nucleic acid sequence of its drainage in February this year was detected as weakly positive. Thereafter, the toilets in each living room were disinfected with chlorine tablets, and the coronavirus nucleic acid sequence test in the bottom mud of the hotel drainage inspection well was negative. This shows that the normal disinfection conditions can achieve the effective inactivation of coronavirus in the community drainage network.
Result: Fecal sewage from patients with coronavirus may distribute the virus into the urban drainage system. Normal sewage disinfection methods and doses can effectively inactivate coronavirus.
Therefore, the following suggestions are made:
- Based on the fact that COVID-19 patients lived in residential communities before being hospitalized, special attention should be paid to the maintenance of the sewage pipeline network in residential districts and effective measures should be taken to prevent the overflow of sewage. For home quarantine personnel, issuing disinfected chlorine tablets and placing them in the toilet tank can effectively inactivate coronavirus.
- Considering the problem of mixed rain and sewage in the urban pipeline network, the centralized quarantine point must be installed with a sewage disinfection device. The sewage cannot be discharged into the urban drainage pipeline network before a reasonable level of disinfection treatment.
- Due to the excretion of feces by asymptomatic infected persons, there is a problem of coronavirus transmission in urban sewers. Attention must be paid to the infection protection of the operation and maintenance staffs of urban sewage treatment plants. The outlet water of sewage treatment plants must be disinfected to prevent fecal-oral transmission.
- In the hospital where COVID-19 patients are concentratedly treated, coronavirus can be effectively inactivated in sewage which is disinfected normally according to the current national standard dosage. To avoid secondary environmental risks, it is not necessary to overdose the disinfectants.
A COVID-19 Centralized Treatment Hospital in Shanghai
Detection points along the drainage pipeline and of sewage treatment plant.
Detection point of a certain quarantine hotel in Shanghai
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