Aerobic vs. Anaerobic Septic Systems in MS: Which Is Right for Hattiesburg?

When Hattiesburg-area homeowners need to replace a failing septic system or install a new one on a challenging lot, they often face a choice between conventional anaerobic systems and aerobic treatment units (ATUs). These systems work on fundamentally different biological principles and have significantly different cost, performance, and maintenance profiles.

Conventional Anaerobic Systems

The conventional septic system — tank plus drainfield — processes waste through anaerobic (oxygen-free) bacterial activity inside the tank. This is the older, simpler technology. It has no moving parts in the tank itself, requires no electricity to operate, and is highly reliable when properly maintained. The limitation is treatment quality: anaerobic treatment produces effluent that, while partially treated, still contains significant pathogen loads that require adequate soil filtration in the drainfield.

In Hattiesburg's clay soil, where drainfield soil filtration is limited, conventional systems work but require properly sized drainfields and conservative loading rates. They are the standard solution for most Forrest and Lamar County properties that can support them.

Aerobic Treatment Units (ATUs)

ATUs introduce oxygen into the treatment process, supporting aerobic bacterial communities that are significantly more efficient than anaerobic bacteria. The result is higher-quality effluent — ATUs typically produce effluent that meets or approaches secondary treatment standards, with BOD and TSS reductions exceeding 90 percent compared to conventional systems.

This higher treatment quality means ATU effluent can be safely dispersed to smaller drainfield areas, or in some cases to surface spray systems on properties where conventional drainfields cannot be permitted. For Hattiesburg lots that fail conventional perc testing and lack space for a mound, an ATU may be the only viable permitted solution.

The Maintenance Reality of ATUs

ATUs have mechanical components — air compressors, pumps, and sometimes chlorination systems — that conventional systems do not. These components require regular professional maintenance, and MS typically requires an annual maintenance contract with a licensed service provider for ATU systems. The ongoing maintenance cost is higher than conventional systems, but for properties where they are the only viable option, the comparison is irrelevant.