A robust and accurate surrogate method for monitoring the frequency and duration of combined sewer overflows

Abstract

Discharges of untreated wastewater from combined sewer overflows (CSOs) can affect hydraulic stress and have significant environmental impacts on receiving water bodies. Common flow rate and water level sensors for monitoring of CSO events are expensive in terms of investment costs, installation, operation and maintenance. This paper presents a novel surrogate method to detect CSO events by using two low-cost temperature sensors. The novelty is the experimental setup for installation of temperature sensors in CSO structures and an algorithm developed to automatically calculate the duration of CSO events considering the response time of the system. The occurrence and duration of CSO events is computed based on the convergence of the two temperature signals. The method was tested under field conditions in a CSO structure, and the results were compared to the information gathered from a parallel installed flow sensor. The application of two temperature sensors installed inside a CSO structure was proven to be robust and accurate for the automatic detection of the occurrence and duration of CSO events. Within the 7-month test phase, 100% of the 20 CSO events could be detected without false detections. The accuracy of detecting the start and end of the CSO events was 2 min in comparison to the flow sensor.Electronic supplementary materialThe online version of this article (10.1007/s10661-018-6589-3) contains supplementary material, which is available to authorized users.

Combined sewer overflows: A critical review on best practice and innovative solutions to mitigate impacts on environment and human health

“…(2013) by adding a second temperature sensor, improving the detection accuracy by implementing an algorithm that accounted for the response time of the system and automatically calculated the duration of CSO events (Hofer et al, 2018). As a result, in a 7-month test phase, all 20 CSO events were recognised without false detections.…”

Design of a monitoring network: from macro to micro design

“…A recent study introduced a rather robust and simple method to detect overflow events and record their duration (Hofer et al, 2018). This method requires two thermometers: one in the main pipe and one at the invert level of the overflow pipe: once the temperatures are equal at both sites, there is an overflow.…”

Can Smart Stormwater Systems Outsmart the Weather? Stormwater Capture with Real-Time Control in Southern California

“…Smart stormwater systems are gaining popularity as a tool to increase the efficiency of conventional stormwater capture. These systems rely on an integrated network of sensors and control structures for real-time control (RTC) of stormwater infrastructure at a system level. , For example, smart stormwater detention ponds respond to weather forecasts by releasing stored water in advance of precipitation events. − Smart systems have been developed to detect and reduce combined sewer overflows − and forecast and reduce urban flood risk. − Recent studies have explored the use of RTC technology to manage environmental flows, shape streamflow, and achieve multi-objective scenarios including, for example, stormwater retention and pollutant removal. ,,− RTC technology also allows for the adaptation of stormwater systems to future land use changes, population growth, and climate change. ,, While the addition of RTC to a stormwater capture system cannot directly increase water supply, it can increase the volume of stormwater captured. ,− For example, Luthy et al . suggested that “in drought-prone regions where stormwater capture can contribute to water supply, RTC can improve both the quality and quantity of water recharged” to aquifers.…”