Many smaller communities do not have the financial resources to construct, rehabilitate, or expand centralized wastewater treatment plants. Decentralized wastewater treatment systems provide cost effective solutions with substantial environmental, public health, and economic benefits.
Excessive nitrogen from inadequately treated wastewater causes blue-green algae blooms like this one in the Potomac River near Washington, DC. Image Credit: Alexandr Trubetskoy via Wikimedia Commons
For many smaller coastal communities and rural towns, traditional centralized wastewater treatment systems are simply too expensive. Residents and business owners in these areas rely on septic systems that are prone to leaching nitrogen and other pollutants into the watershed. In addition to causing public health issues, insufficiently treated wastewater causes eutrophication or excessive plant and algae growth due to high levels of nitrogen and phosphorous that overwhelm natural flushing of these nutrients from the water.
The Costs of Insufficiently Treated Wastewater
During the 1990s, scientists pinpointed the cause of massive algae blooms off the coast of Cape Cod to septic systems leaking nitrogen into the groundwater. In fact, water treatment professionals have identified similar problems in Long Island Sound, Puget Sound, Chesapeake Bay, off the coasts of New Jersey and Delaware as well as along rivers in inland communities. In addition to the environmental impacts, the damage from algae blooms caused by inadequately treated wastewater cost the United States $2.2 billion each year. What is a sustainable and cost effective wastewater management solution to minimize these costs?
Pre-Engineered Decentralized Water Treatment Systems: Scalable and Cost Effective
Septic Tank Effluent Pump (STEP) collection systems can be installed at shallow depths that facilitate their use on hilly or rocky terrains. Image Credit: Soil Science via Flickr
A recent article published on the website Civil and Structural Engineer proposes that decentralized Alternative Onsite Water Treatment Systems (AOWTS) paired with Septic Tank Effluent Pump Collection systems (STEP) and scaled down versions of secondary and tertiary effluent systems typically used in large centralized wastewater treatment plants. Homeowners, business owners, and developers can easily install small pre-engineered AWOTS on their properties as an alternative to cesspools and as a means to eliminate surface discharge of pollutants. For communities that need an economically feasible means of rehabilitating or expanding their existing wastewater treatment systems, AOWTS combined with modern treatment plant parts, and new dispersal field parts, such plastic chambers or geosynthetic bundles are likely to be an effective and efficient solution.
STEP systems use a septic tanks to collect wastewater and allow solid waste to settle onsite. A pump in tanks provides pressure to drive the settled wastewater in narrow diameter collection lines leading to a centralized treatment facility or decentralized wastewater treatment system. This saves space since there is no need for any additional primary settling of the wastewater at te treatment site. For secondary and tertiary wastewater treatment, pre-engineered systems like activated sludge systems, trickling media filters, and moving bed bioreactors typically used in large centralized wastewater treatment plants can be scaled down for use in smaller decentralized systems.
Benefits of Small Decentralized Wastewater Treatment Systems
Decentralized wastewater treatment systems provide rural communities an economically achievable means of keeping their estuaries clean and healthy. Image Credit: California Department of Water Resources via Wikimedia Commons
Communities that have employed decentralized wastewater treatment systems have realized the following benefits:
- Developers and home builders do not have to wait for local water management authorities to complete an extension of the sewer system in order to finish a project, which fosters economic development.
- Small towns do not have to spend limited financial resources to expand their centralized water treatment facilities to promote growth.
- The systems provide affordable long term solutions to wastewater management challenges.
- Engineers can easily adapt small decentralized wastewater treatment systems to a variety of site conditions.
- Officials are able to provide their communities with public health protections and preservation of natural resources without excessive expenditure of limited taxpayer funds.
- Treated water can be dispersed into the soil near groundwater extraction sites, which permits recharging of the aquifer.
What experience do you have with decentralized wastewater treatment systems? Are they solutions you would recommend to your clients?