Background: Wastewater-based epidemiology (WBE) has become crucial for early microbial outbreak detection and public health surveillance globally, underscored by the COVID-19 pandemic. However, despite advancements in sampling and analyses, interpreting results and estimating infection rates pose challenges. Enhancements in sewer system engineering, understanding the wastewater environment, and addressing the impact of the environment on the accuracy of results are needed. Objective: This scoping review aims to identify engineering knowledge gaps in WBE to guide future study designs. Design: Research on “wastewater-based epidemiology” involving “engineering”, published between 2015 and 2023, was extracted from the Scopus database. Results: This scoping review examines elements influencing WBE’s precision and reliability, especially in identifying and measuring SARS-CoV-2 RNA. It identifies significant effects of engineering, analytical practices, and the wastewater’s composition on WBE performance. Conclusions: This review calls for further investigation into economical evaluation methods of these factors to enhance WBE data normalization and interpretation, utilizing existing wastewater treatment plant data used for treatment control, which could be a cost-effective approach over more expensive population biomarkers. This approach, aside from SARS-CoV-2, holds potential for application to a broader number and types of diseases, as well as population consumption habits.

Diagram showing how population, weather and urban activities influence wastewater composition, where parameters BOD5, COD, N, NH4-N, P and PO4-P are analysed to support wastewater-based epidemiology normalization. Wastewater-based epidemiology uses data from wastewater treatment plants to monitor the health of a population, but requires accurate normalization to provide per-capita, or individual-based, health indicators. This study assessed the long-term stability and suitability of key wastewater parameters for population normalization using data from 45 treatment plants across Latvia over a ten-year period, representing two-thirds of the national population. Specific pollutant loads were calculated for biochemical oxygen demand, chemical oxygen demand, total nitrogen, ammonium nitrogen, total phosphorus, and orthophosphate. Overall, pollutant loads remained stable during the study period, though an increase was observed in recent years, with ammonium rising by 27%, total nitrogen by 15%, and phosphorus by 11%. Industrial plants consistently showed higher pollutant loads than municipal facilities. Nitrogen exhibited the lowest variability among the evaluated hydrochemical parameters, suggesting its suitability as a robust normalization indicator within the studied dataset, while chemical oxygen demand can serve as a supporting indicator. In contrast, biochemical oxygen demand and phosphorus were less suitable due to operational sensitivity and high variability. The study recommends using rolling, plant-specific median values over two to three years to enhance the precision and comparability of population-normalized wastewater-based health assessments.

Wastewater-based epidemiology (WBE) is increasingly used to monitor public health trends and chemical consumption by analyzing biomarkers in untreated wastewater. As a complementary approach to traditional epidemiological surveillance, WBE provides insights into infectious disease spread, drug use, and pharmaceutical consumption. However, accurate population normalization remains a major challenge, because census-based population estimates often do not correspond to hydrologically defined wastewater catchments. This study evaluates whether routinely monitored wastewater quality parameters can serve as cost-effective population-normalization proxies in WBE. Using data from Latvia’s national COVID-19 wastewater surveillance program, the performance of conventional wastewater parameters (BOD₅, COD, suspended solids, total phosphorus, and total nitrogen) was compared with endogenous and exogenous biomarkers, including 5-HIAA, caffeine, cotinine, ethyl sulfate, gabapentin, ibuprofen, and diclofenac. Population estimates based on census and operator data were assessed under varying weather conditions. The results indicate that routine wastewater parameters, particularly total nitrogen, may serve as suitable indicators for population normalization in WBE, with performance comparable to or exceeding that of commonly used biomarkers. These findings support the use of routinely monitored parameters as scalable and accessible tools for improving WBE reliability and strengthening public health surveillance and early warning systems.

Drinking water for Riga city is provided by the groundwater well field “Baltezers, Zakumuiza, Rembergi” and by the Daugava river as a surface water source. Presently (2016), it amounts to 122 thous.m3/day and both sources do not exploit even half of their power. Therefore, in future it seems reasonable to use only groundwater, because the river water is of low quality and its treatment is expensive. Scientists of Riga Technical University by using hydrogeological model of the well field “Baltezers, Zakumuiza, Rembergi” proved that its capacity covers the demand for 120–122 thous.m3/day of drinking water in Riga until 2030. Therefore, it is possible not to exploit the Daugava river as the water source. The research was done as to the request of the company “Aqua-Brambis”. The company asked to evaluate hydrogeological properties of several versions of water supply of Riga city. It was necessary to check the stability of syphon type systems that extract the groundwater for the city under the conditions of their increased productivity. It was also proved that the syphons may be replaced by a pumping station. Then the number of exploitation wells considerably decreases. The impact of expenses related to reconstruction of the wellfield and the water distribution network was not considered. The publication may be of interest for the specialists dealing with problems of water supply for large cities.