An Application of Low-cost IoT Sensors for Automated Real-time Detection of Illicit Discharges in Orange County's MS4

Abstract Submission: National Pollutant Discharge Elimination System (NPDES) permittees are required to implement a program of illicit discharge detection and elimination (IDDE) in the municipal separate storm sewer system (MS4). Common approaches include crowd-source reporting to hotlines or periodically sampling MS4 outfalls for evidence of illicit discharges. Success of a manual sampling approach requires that an illicit discharge is actively occurring while the sampling team is on-site, an unlikely outcome due to the limited scope of site visits and large number of outfalls. Orange County (California) Public Works (OCPW) is partnering with the Southern California Coastal Water Research Project, the University of Guelph and the BoSL Lab to pioneer development of an automated method for real-time illicit discharge detection. The pilot program deploys a network of internet-of-things (IoT) sensors to continuously monitor storm drains to establish, then identify deviations from, a baseline trend. If an anomaly is detected, an email/text alert calls the IDDE team to the offending site in near real-time for source investigation and mitigation. The low-cost IoT, open-source sensors from the BoSL lab deployed in the OCPW MS4 use cellular telemetry to deliver real-time monitoring information about water depth, electrical conductivity (EC), temperature, turbidity, and velocity to an online dashboard and database. Custom automated post-processing routines continuously analyze the incoming data to generate alarms for suspected illicit discharges and sensor maintenance reports to the IDDE program manager. Descriptions of the technical hurdles, logistical planning, and proof-of-concept results of this pilot test are intended to help improve the efficacy of IDDE programs required by NPDES permits nationwide.

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