Introduction to Decentralized Wastewater Treatment
What are "Onsite" wastewater treatment systems?
Quite literally, an "Onsite" or "On-lot" wastewater treatment system is one that treats wastewater and discharges effluent into the ground 'onsite' at the location the sewage is generated. Perhaps the simplest example of this is a septic tank and leachfield serving a single home. Instead of sending wastewater into a sewer system serving many homes, the water is treated and returned to the ground on the same property.
What is a "Decentralized" wastewater system?
The terms "Decentralized" and "Onsite" are often interchanged. However, a "Decentralized" system also refers to the use onsite or cluster systems to treat all of the wastewater collectively generated by many homes or an entire community. Rather than operating a centralized wastewater treatment system where all sewage flows to one treatment plant, most rural communities today still use a decentralized wastewater treatment approach, traditionally with one onsite system per household, though few local local leaders would ever think of their community as having a decentralized system.
The Problem with Traditional Decentralized Systems
The obvious problem with a traditional decentralized approach in suburban and rural areas is that all care and maintenance of onsite wastewater treatment systems is entirely left in the hands of homeowners. As with any type of home maintenance, some people are good about the upkeep of their septic systems, and others aren't. Many simply do not know how to care for them, and some do not know where to even find their onsite systems burried underground. Unfortunately, the result of years of neglect is a failing system that can pollute the groundwater as well as nearby lakes and streams. Failing systems also often generate foul odors. These are pollution problems that obviously do not stay 'onsite', and because there are commonly several failing systems in any given area, it can become a real nuissance and public health issue for rural residents. The biggest concern, of course, is the impact on drinking water sources, not only private wells, but also for larger communities that may use groundwater or surface water downstream.
The Push Towards Managed Decentralized Systems
For small communities with a few hundred homes or less, particularly where homes are not close together, there are real advantages to a decentralized wastewater treatment approach versus a centralized system. For centralized systems, the biggest capital cost in any size community is usually not the treatment plant itself, but rather the collection system, which are generally gravity sewers. In rural areas where there are far fewer homes per mile of pipe, centralized collection systems are simply cost prohibitive. Also, many small communities do not have the resources to properly maintain a multimillion dollar centralized wastewater collection and treatment system. Another big concern is the potential for unwanted suburban sprawl and development that can negatively change the rural qualities of an area its residents value.
From a regulatory agency standpoint, though, it is better to have one entity and one point source of pollution to monitor rather than a hundred non-point sources (i.e individual homeowners), most of whom are already neglecting their onsite systems. The solution for communities that cannot afford or do not want 'the big pipe', but need to address onsite system failures, may be to adopt a managed decentralized system. This can range from friendly reminders to residents about proper maintenance, to a government entity or homeowners association actually taking ownership and maintaining individual onsite systems. The US EPA has developed five different Management Models communities can consider when exploring a managed decentralized approach. Funding is available to help communities pay for planning, engineering and construction of decentralized wastewater systems.
Where to Start
So where does a community interested in exploring a managed decentralized wastewater system begin? Some good materials to start with are listed below, or contact the Ohio Rural Community Assistance Program.