Preparing Operations for Direct Potable Reuse

Last Modified: Oct 30, 2015


  • Ben Stanford, Troy Walker - Hazen and Sawyer

Operational interface protocols should provide detail on the water quality and monitoring requirements for upstream and downstream entities, such as wastewater and drinking water treatment plants, as well as collection and distribution systems.

Several alarm types are available with strategically managed alarm thresholds. One example is a Block Average Alarm, depicted above. The alarm is set to the average value over a pre-determined time period, rather than a single input, within the alert period. In this example, the alarm notification (when Block Average exceeds Alert Threshold) would only occur for block 3 of the true example, since the Process Value average of the time block is above the alert threshold.

Operator training should include risk management, understanding of regulations, CCPs, understanding of upstream and downstream interfaces, and sampling and analysis.

This infographic illustrates the process of identifying CCPs and implementing appropriate operational responses.

Direct potable reuse (DPR) represents significant innovation in the field of public health. While the technology upon which it relies has been proven for many years, the barrier to more widespread adoption has been a reluctance, real and perceived, among customers to consume drinking water produced from wastewater that did not travel through “nature” between uses. Consumer education and widening gaps between supply and demand have helped overcome this reluctance, yielding a recent boom of DPR development.

This recent development reveals another “human” barrier to widespread adoption of DPR. DPR facilities are typically highly automated and include several advanced technologies, many of which are not currently well-covered in existing training and certification programs. DPR operators will in most cases be drawn from the existing pool of drinking water and wastewater operators. These operators have a valuable knowledge base, but they will need to be supported with additional technical training and operational management plans and procedures as they undertake their new roles.

Through work at DPR facilities with our clients and cutting-edge research, Hazen and Sawyer is developing the training and certification programs to help ensure operations staff have the tools and information they need to produce high-quality, reliable water for their community. With appropriate development of critical control points (CCPs), response procedures, alarm management, and proper training, staff can be prepared to handle all levels of operation at DPR facilities.

Operating Procedures
The operations, maintenance, and monitoring plan (OMMP) for a facility identifies the risks to successful system operation, how the system should mitigate those risks, and what procedures should be followed in the event of system failure. It will include dedicated response procedures at each critical process barrier or CCP to ensure a consistent approach for managing health risk. Emergency response procedures and emergency response communication requirements must also be clearly established.

Operational Interfaces
Operational interface protocols should provide detail on the water quality and monitoring requirements for upstream and downstream entities, such as wastewater and drinking water treatment plants, as well as collection and distribution systems. Historically, recycled water plants operate independently from upstream wastewater plants. In the DPR scenario, the protocol will detail cooperative operating procedures, communications protocols, data sharing, and other elements necessary to integrate multiple entities in the one DPR scheme. This requires DPR operators to understand essential elements of wastewater treatment, while focusing on finished water production and distribution system management.

Operational Monitoring
The high level of automation in DPR facilities requires that information be strategically managed. Alarm flooding poses a significant risk, with the acute possibility of far too many alarms being generated, leading to overwhelmed operations teams overlooking important alarms. Development of effective and realistic performance monitoring, trending, and alarming is critical to anticipating performance risks and taking preventative action before a problem occurs. Dashboard reports are particularly useful for operations teams to clearly keep their eye focused on operational targets.

Operator Skills and Training
Relative to existing water and wastewater treatment systems, DPR operations teams are under much greater scrutiny for performance and must therefore have adequate training and certification processes in place to provide a framework for developing and evaluating the necessary skills for successful operation and management of water recycling systems.

Appropriately developed training and certification is critical to support this requirement. But certification programs can only develop a minimum standard for operations. Beyond this, each facility will require a thorough ongoing training program that is tailored to that facility and includes items such as:

  • Demonstrated knowledge of operational response procedures, with appropriate testing and “fire drills.”
  • Detailed monitoring of operator competence, with demonstration of knowledge and experience in the field.
  • Effective knowledge of performance monitoring and trending – making sure to anticipate performance and meet performance targets.
  • Good understanding of regulatory and permit targets, with regular updates as these develop.
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