Wastewater Operations
The Wastewater Operations Branch (WWO) is responsible for the collection, conveyance, and treatment of municipal wastewater across the Houston area.
With a dedicated team of more than 600 employees, WWO operates and maintains:
- 38 wastewater treatment plants (WWTPs)
- Two wet weather facilities
- A vast collection system with 370+ lift stations
- More than 6,100 miles of wastewater pipelines, ranging from 2 to 144 inches in diameter
Overview of the Wastewater Treatment Process
Wastewater generated from homes and businesses is transported through a network of pipelines and lift stations to the City’s 38 wastewater treatment plants. Upon arrival, the treatment process follows these steps:
Preliminary Treatment
Raw sewage is pumped through bar screens to remove large debris, followed by a grit removal system to extract sand, silt, and other heavy inorganic materials. These materials are then sent to a municipal landfill for disposal.
Biological Treatment (Activated Sludge Process)
The screened wastewater enters an aeration basin or reactor, where oxygen is introduced to support microorganisms that consume and break down organic pollutants.
Clarification
The treated wastewater flows into secondary clarifiers, where solids (biomass) settle. A portion of these solids is returned to the reactor or aeration basin to maintain the biological process. Excess sludge is removed for further processing and beneficial reuse (e.g., as fertilizer).
Disinfection
The clarified water undergoes disinfection to eliminate pathogens. Sodium hypochlorite (bleach) is commonly used in a chlorine contact basin. At select facilities, ultraviolet (UV) disinfection is employed as an alternative, chemical-free method to ensure public and environmental health.
De-chlorination
To protect aquatic life, any remaining chlorine is neutralized using sodium bisulfite at wastewater treatment facilities with a permitted flow over 1 million gallons per day (MGD) before discharge into receiving streams (e.g., bayous).
Biosolids Management
The solids removed during treatment, known as biosolids, are further treated, stabilized, and reused as beneficial soil amendments or fertilizers in compliance with state and federal regulations.
Wastewater Collection System
To effectively manage and maintain Houston’s extensive wastewater collection system, WWO operates two integrated maintenance programs:
Focuses on rapid response and resolution of customer-reported issues such as sewer backups, blockages, sinkholes, and odor complaints, ensuring public health and safety.
Aims to proactively maintain and rehabilitate the collection system infrastructure to reduce failures, prevent sanitary sewer overflows (SSOs), and extend the life of system assets. This program is a core component of the City’s Consent Decree compliance strategy.
Customer Service Request Maintenance Program
Each year, the City receives more than 20,000 wastewater-related service requests through the 311 Call Center. These requests typically involve a range of issues, including sewer backups, sewer overflows, blockages, cave-ins, sinkholes, damaged or missing manhole covers, odor complaints, etc. To efficiently manage and respond to these concerns, the Customer Service Request Maintenance Program includes the following core components:
Field personnel are dispatched within 24 hours of receiving a customer complaint. This initial site visit includes direct communication with the customer and an on-the-ground assessment to verify the reported issue and determine the appropriate next steps.
Obstructions within the sewer lines are cleared using high-pressure water jetting equipment. This ensures the immediate restoration of flow and reduces the risk of backups and overflows.
When issues require further diagnosis, a comprehensive suite of inspection methods is employed. These include closed circuit television (CCTV) inspections, sewer tracing, dye and smoke testing, and odor detection analysis to identify the root cause and define necessary corrective actions accurately.
To minimize service disruptions, temporary bypass systems equipped with automatic float controls are deployed. These systems maintain sewer flow and customer service continuity until permanent repairs can be implemented.
To ensure public safety during active work, protective measures such as steel plates, traffic barricades, cones, and clear signage are deployed and maintained throughout the duration of the site activity.
Repairs to the public wastewater collection system are carried out by internal crews and supplemented by contracted repair and rehabilitation teams. Once repairs are completed, the site is restored to its original condition to maintain neighborhood aesthetics and safety.
Preventative Maintenance Program
The City’s Preventive Maintenance Program is designed to proactively maintain and renew the sanitary sewer collection system, with the primary goal of minimizing failures and preventing sanitary sewer overflows (SSOs). This program supports compliance with the City’s Wastewater Consent Decree and includes the following key elements:
High-risk areas with a history of SSOs or recurring blockages are prioritized for frequent and scheduled cleaning. This targeted approach reduces the likelihood of future incidents.
Using CCTV inspection technology, the condition of sewer lines is regularly assessed. Footage is reviewed and evaluated by in-house engineers to determine pipe integrity and identify potential issues requiring attention.
Sewer lines exhibiting non-structural defects or operational issues that do not yet warrant rehabilitation are placed on a recurring CCTV monitoring schedule. This enables ongoing oversight and early intervention if conditions worsen.
Sanitary sewer infrastructure, including pipelines, manholes, and service laterals with confirmed structural defects, is repaired, replaced, or rehabilitated. The City employs trenchless technologies to minimize surface disruption. All construction work is executed by qualified rehabilitation contractors and closely monitored by City inspectors to ensure compliance with design and quality standards.
System Oversight and Program Management
To ensure effective wastewater system performance, regulatory compliance, and long-term service reliability, several technical and operational teams work together to oversee planning, project execution, and infrastructure renewal across the collection and treatment systems:
These teams jointly manage the Collection System Pipe Renewal Program, which focuses on identifying, prioritizing, and addressing infrastructure renewal needs across the sanitary sewer network to ensure system integrity and service reliability.
Responsible for providing quality assurance and project oversight, this group monitors the progress and performance of both planned sewer rehabilitation and unplanned emergency repair projects, ensuring work is completed on time, within budget, and in accordance with specifications.
This section develops, administers, and manages a wide range of professional services contracts essential to the ongoing operations of the City’s wastewater system. These contracts include engineering, construction, inspection, consulting, and other technical services necessary for maintaining and enhancing infrastructure performance.
This team plays a pivotal role in coordinating and supporting Wastewater Operations Capital Improvement Projects (CIP). Responsibilities include managing work order contracts for engineering design, staff augmentation, and technical support services. The team also oversees fast-track emergency engineering projects and supports critical tasks to ensure compliance with the Consent Decree through timely project delivery and documentation.
Wastewater Infrastructure Planning (WWIP)
WWIP leverages data, technology, and modeling tools to improve system performance and guide long-term investments:
Continuously update and refine Integrated Catchment Modeling (ICM) tools to evaluate both current and projected system capacities. These models help identify and resolve hydraulic constraints, guide the development of long-term plans and Capital Improvement Projects (CIP), and support compliance with Consent Decree requirements. This proactive approach ensures the infrastructure remains resilient and responsive to community growth and regulatory demands.
Leverage artificial intelligence to enhance preventive maintenance strategies, streamline operational processes, and enable rapid investigation and resolution of O&M issues. AI tools support root cause analysis, enabling data-informed decision-making that reduces downtime, improves system performance, and optimizes resource allocation.
Implement a risk-based approach to asset management, focusing on critical infrastructure components that require timely intervention. This strategy is aligned with the International Organization for Standardization (ISO) 55000 standards, ensuring assets are managed systematically and sustainably throughout their lifecycle. Prioritization is driven by condition assessments, failure risk, and service impact evaluations.
Utilize real-time monitoring and performance tracking through comprehensive dashboards that report on Key Performance Indicators (KPIs). Incorporate big data analytics using the Advanced Infrastructure Analytics Platform (AIAP) hosted on Amazon Web Services (AWS) Data Lake to support predictive insights, optimize system performance, and enable evidence-based planning and investment decisions.
Protect Our Pipes
70% of sewer overflows in Houston are caused by clogs from fats, oils and grease poured down the drain and wipes flushed down toilets.