As onsite systems continue to be installed in more challenging environments — tight lots, sensitive soils and nutrient-restricted areas — advanced treatment units are no longer niche technology. For many technicians, they’re becoming part of everyday work.
At their core, advanced treatment units are designed to do one thing: treat wastewater to a higher level than a conventional septic tank. The U.S. Environmental Protection Agency notes that advanced onsite systems incorporate additional treatment processes to reduce contaminants before effluent is discharged to the soil.
What Makes a System “Advanced”?
A conventional septic system relies mostly on passive, anaerobic treatment in the tank and soil. An advanced unit adds additional treatment steps — often mechanical, biological or both — to further reduce contaminants before dispersal.
In practical terms, that can include:
- Aeration (adding oxygen to boost bacterial activity)
- Recirculation (cycling effluent for additional treatment)
- Fixed media or biofilm systems
- Nutrient reduction processes (especially nitrogen)
For technicians, the takeaway is straightforward: These systems behave more like small treatment plants than traditional septic systems.
Where and Why They’re Used
ATUs are often required when:
- Soil conditions are poor or shallow
- Sites are near water bodies or environmentally sensitive areas
- Nitrogen or nutrient reduction is mandated
- Lot size limits the use of a traditional drainfield
According to the EPA, many states approve specific advanced technologies to meet these types of site and regulatory challenges as part of decentralized wastewater systems. In short, ATUs allow systems to be installed where conventional systems may not be viable.
How They Work
While designs vary, most advanced systems follow a similar flow:
- Primary treatment (like a septic tank) separates solids
- Secondary/advanced treatment further breaks down organics and nutrients
- Clarification or disinfection (in some systems) further improves effluent quality
- Dispersal sends treated water to soil or another approved method
Aerobic treatment units, for example, introduce oxygen into the wastewater, allowing aerobic bacteria to break down waste more efficiently and produce cleaner effluent. The result is simple: better treatment — but with more components involved.
The Trade-Off: Performance vs. Maintenance
Higher performance comes with additional responsibility. Advanced systems typically require:
- Routine inspections
- Maintenance of mechanical components (blowers, pumps, controls)
- Monitoring to ensure proper treatment
The EPA emphasizes that these systems require more oversight than conventional septic systems because of their added complexity. For technicians, this often means:
- More frequent service intervals
- Greater system familiarity
- A stronger emphasis on ongoing education
Staying Current with Advanced Systems
As advanced systems become more common, the expectations placed on technicians continue to shift. Working with ATUs requires not only understanding how they operate, but also how to maintain performance over time and troubleshoot when conditions change.
Training on these systems is often built into broader, advanced coursework rather than treated as a standalone topic. For example, industry programs such as those offered by the National Association of Wastewater Technicians include advanced system concepts — like ATUs — within higher-level installer and operations courses, as well as through field-focused training such as vacuum truck operations. Supporting materials like O&M checklists, EPA fact sheets and other technical resources are also commonly used to reinforce this knowledge in day-to-day work.
The Bottom Line
ATUs are not simply upgraded septic systems. They are engineered treatment systems that require a higher level of attention, understanding and care. For technicians, that means:
- Expanding practical knowledge
- Staying current with system types and requirements
- Continuing to build skills as technology evolves
As onsite wastewater treatment continues to advance, so does the role of the technician — moving from installer and service provider to an essential part of protecting both public health and the environment.
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