Pima County's 'Smart Collection System': Real-Time H2S Monitoring Pinpoints Problematic Sites in Pima County, AZ

SUMMARY
Pima County's unique landscape includes climate temperatures ranging from the low 60's in winter months to the 100's during the spring and summer. Vast coverage areas include urban and suburban populations with numerous mountain ranges resulting in large elevation swings. Due to the extensive network of sewer lines and manholes, Pima County experienced high hydrogen sulfide (H2S) amounts throughout their collection system. The Odor Control Conveyance team wanted to monitor problematic sites to validate known issues and discover any unknown issues which could cause potential health hazards to employees and the public; nuisance due to smell; and pipe corrosion/damaged infrastructure, leading to lowered asset life and possible SSO's due to potential pipe/manhole collapse. KEYWORDS: hydrogen sulfide, odors, SSO, smart sewer, smart water, automation, smart city, smart infrastructure, remote sewer monitoring

INTRODUCTION A UNIQUE CLIMATE LANDSCAPE
Pima County Regional Wastewater Reclamation Department (RWRD) serves 280,000 customers across the Tucson area, covering 420 square miles, 5 jurisdictions, and 2 tribal nations. Vast coverage areas include urban and suburban populations with numerous mountain ranges resulting in large elevation swings. RWRD maintains and operates 3,500 miles of sanitary sewer lines, 67,000 manholes and 8,400 public cleanouts. Pima County's unique landscape includes climate temperatures ranging from the low 60's in winter months to the 100's during the spring and summer. During rain events, data collection from sensors provides flow level data alongside 8 rain collection sites. GPS sensor monitoring provides RWRD with not only sanitary sewer system capacity in monitored areas, but also the amount of Inflow & Infiltration (I&I) entering the collection system that ultimately goes towards the Agua Nueva & Tres Rios Treatment Facilities for treatment.

THE CHALLENGE WHAT'S THAT SMELL?
Due to the extensive network of sewer lines and manholes, Pima County experienced high hydrogen sulfide (H2S) amounts throughout their collection system. The Odor Control Conveyance team wanted to monitor problematic sites to validate known issues and discover any unknown issues which could lead to potential health hazards to employees and the public; nuisance due to smell; and pipe corrosion and damaged infrastructure causing lower asset life and a threat to the Sanitary Sewer System environment (i.e. possible SSO's due to potential pipe/manhole collapse). Prior to deploying smart sewer technology, reactive dosage amount performed at Chemical Dosing Units (CDU) were based on odor complaints within odor loggers capturing H2S PPM data for analysis. Both Liquid Phase and Vapor Phase Treatment were used which increased chemical and labor costs and created greater inefficiencies.

THE SOLUTION: SMART SEWER H2S MONITORING TECHNOLOGY
In order to take a more proactive approach, Pima County deployed 44 real-time satellite monitoring H2S units to provide real-time, low-cost hydrogen sulfide (H2S) monitoring at problematic sites across the collection system. Large amounts of data collected from the units allowed Pima County to better understand their system, pinpoint problem areas and fine tune chemical dosage, in turn, optimizing resources to prevent asset degradation. Pima County was then able to integrate H2S data with their asset management system which gave them the ability to monitor CDU dosing changes and, within an hour or two, see the H2S level change based upon the dosing values applied; reduce chemical dosing based on live trend H2S values; and determine the required usage based on CDU tank level volume to not only extend chemical usage, but to also use the chemical more efficiently. With the API integration, approximately 25,000 data points were pulled into the MS Power BI platform for evaluation along with the Asset Management system (Infor IPS). Numerous sensors monitor mid-large size interceptors and other problematic areas and the sensor data capture allows the department to look at the Conveyance system and more efficiently visualize the data through dashboards, analyze collected sensor data and work orders, and use those dynamic measures to understand the collection system status.

THE PROOF: PINPOINTING HOTSPOTS LEADS TO IMMEDIATE ROI
In addition to a better overall understanding of the system, Pima County has been able to quickly identify and address problematic areas, including CDU site dosing, H2S PPM values, and areas where flow monitoring is needed. Smart sewer technology has allowed them to better allocate resources (staff and vehicle travel costs) based on work order evaluations in comparison with unneeded site visits. The County has gained improved visualization of site conditions leading to a more proactive versus reactive decision-making process. The creation of visual baselines and development of KPIs has minimized issues and alleviated known odors. And, the 24/7/365 eyes and ears of the sewer allow real-time evaluation of any changes in the system, making chemical dosing dynamic, thus allowing for reduction in chemical costs and/or allocation of saved chemicals for timeframes when chemical is needed.