Flow rate influence on sediment depth estimation using temperature sensors

Paper presented at ICUD 2024

Abstract:

Sediment accumulation in sewers is a major concern in urban drainage systems, as it causes the loss of hydraulic capacity, generates hazardous gases, and increases the risk of blockages (Wu et al., 2023). Sewer maintenance operations are mostly performed based on previous experiences, as there is no methodology to continuously monitor sediment build-up processes. This study uses temperature sensors to continuously monitor the thermal oscillations in liquid and sediment layers to measure heat transfer processes between both media and, thus, estimate the accumulation of bed deposits, similar to Sebok et al. (2017) in river streambeds. Temperature-based systems were also developed for monitoring sediments in urban drainage systems, but without considering flow conditions in sewers (Regueiro-Picallo et al., 2023a). Wastewater flows introduce convective heat transfer processes at the water-sediment interface. Consequently, the objective of this study was to evaluate the influence of the convective processes on the estimation of sediment depths using systems based solely on temperature measurements. For this purpose, laboratory experiments in an annular flume were performed using different sediment depths, water temperature gradients and flow rates. The main advantages of this facility were the steady flow conditions to simulate heat transfer processes and the room-temperature control system. The results are of high scientific and operational relevance to improve the understanding of sediment build-up processes and maintenance strategies for urban drainage systems.