COULD HIGH-THROUGHPUT WASTEWATER ANALYSIS BECOME A KEY TOOL IN SARS-COV-2 SURVEILLANCE?


Introduction


As governments and public health organisations globally use prevention and control methods to stop the spread of COVID-19, strategies to monitor the pandemic have been a primary area of focus. In many countries, the COVID-19 pandemic has been exacerbated by the implementation of unoptimised testing strategies. Antigen and PCR testing, for example, has largely proven insuffi cient to monitor disease transmission in local communities, primarily because testing strategies often do not include systematic testing of the general population, making it challenging to monitor asymptomatic patients. As such, complementary methods have been implemented by many authorities around the world to provide more holistic information about public health.


Monitoring wastewater has been successfully used as one such method to detect SARS-CoV-2 levels in local communities [1]. SARS-CoV-2 can be shed in the faeces of individuals with symptomatic or asymptomatic infection, meaning wastewater surveillance is able to capture data on both types of infection. The fl uctuation of viral levels in sewage systems provides an indirect early warning system of COVID-19 outbreaks in the surrounding communities, and can assess how preventative methods of vaccination drives and social distancing are reducing transmission.


While this method does not provide detailed information about how many people have the virus or who they are, it does give population-level oversight of SARS-CoV-2 levels with the benefi t of a readily accessible testing sample. Sewage water samples can then be tested in local COVID-19 laboratories to inform public health decision-making.


Wastewater-based epidemiology (WBE) programmes traditionally use wet chemistry methods to measure several biomarkers of COVID-19 in addition to viral levels of SARS-CoV-2 to give more comprehensive information about public health. Effective SARS- CoV-2 surveillance needs accurate results for large numbers of samples, but WBE workfl ows are often time-consuming, labour- intensive and costly, meaning the potential for tracking COVID-19 in water samples cannot be utilised by many laboratories. This article discusses how high-throughput and cost-effective discrete analysis workfl ows are overcoming these limitations, enabling testing laboratories to monitor infection rates, and the spread or control of SARS-CoV-2 in communities.


is already seeing infection extent and trend information, with wastewater viral concentration levels closely matching the number of new cases in an area [2].


Laboratories mainly rely on quantitative reverse transcription polymerase chain reaction (RT-qPCR) techniques to measure and quantify SARS-CoV-2 RNA in wastewater, although several variables can make this challenging. For example, viral load measurement of SARS-CoV-2 is critical, and survival of the virus in water depends on temperature, pH, concentration of suspended solids and organic matter, and levels of disinfectant. As such, complementary methods to provide more comprehensive and contextualised population data are required for a more accurate measurement of infection within a community.


Measurements of several chemical and physiochemical biomarkers provide longitudinal information about community-wide health conditions that can be tracked and compared with COVID-19 viral data. These biomarkers include total nitrogen, phosphorus, ammoniacal nitrogen, urea and creatinine, and indicate normal faecal load and seasonal or daily fl uctuations against which viral data can be analysed. Additionally, markers, such as pH, conductivity, ammonia, nitrate, nitrite, total organic nitrogen, ortho-phosphate, and other ions such as chloride and sulphate, can provide indirect information about the survival period of a virus within the wastewater.


Traditional techniques can’t keep up with the throughput


How can wastewater testing contribute


to the control of COVID-19? SARS-CoV-2 detection in wastewater can indicate the prevalence of COVID-19 in a community, and when used over time, show how infection levels respond to preventative measures. The National Wastewater Surveillance System (NWSS) in the U.S.


IET SEPTEMBER/OCTOBER 2021 WWW.ENVIROTECH-ONLINE.COM


Together, RT-qPCR measurement of SARS-CoV-2 and wet chemistry measurement of complementary biomarkers is an effective way of assessing the level of infection within communities. However, these methods are time-consuming and costly, which can severely limit the capability of local authorities to track COVID-19 infection in wastewater.


WBE programmes in testing laboratories rely on complex workfl ows with several moving parts that must integrate to be successful. For example, specialist scientists are required to run and monitor each test, and each test requires multiple methods


with sequential steps for each parameter, all needing separate samples and large reagent volumes for each sample. A typical determination of ammonia by titration not only requires a large sample volume (~100 ml) to reach appropriate limits of detection but also requires glassware and an adequate cleaning process to avoid contamination, creating barriers to rapid testing of high numbers of samples. Using hazardous reagents containing mercury means a mercury recovery procedure must be included for any waste and large volumes of acid may also be required, exposing the analyst to unnecessary and avoidable risks. Greater statistical variance between analysts during the method validation process results in a higher limit of detection and therefore a narrower analytical range for which parameters such as fl ow and faecal load can be estimated against.


Another challenge is to do with how samples are collected in the fi eld and how this affects bulk testing in wet-chemistry labs. For SARS-CoV-2, seven day monitoring of wastewater samples is essential if trends and patterns in data are to be identifi ed and interpreted correctly whilst the data is still relevant and a local government can respond in time. Often, scientists fi nd that it is only possible to take a quick ‘grab sample’ than a more representative composite from sampling locations due to the large number of sites needing to be tested. ‘Grab samples’ are more challenging to analyse as it is important to monitor complimentary analytes such as ammonia, phosphate, pH, and conductivity in order to estimate a correction of the PCR results. The ammonia result is used to adjust for fl ow and population input, adding context and perspective to the data. Phosphate, pH, conductivity and suspended solids can provide additional and confi rmatory information about the sample, as well as acting as qualifi ers for the ammonia result. It is therefore important that rapid repeat analysis is performed to confi rm suspect or erroneous results – something that simply isn’t feasible with traditional wet-chemistry techniques when dealing with hundreds of samples per day.


With slow processes like these, labour-intensive and costly


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84