Decentralized Wastewater: A Viable Option for Lakeshore Communities

By F. X. Browne, Inc. President, Dr. Frank Browne, P.E.

 

As the need for upgrading wastewater treatment facilities is increasing and costs are rising, decentralized treatment options are becoming more and more attractive, especially in lakefront communities.

A decentralized wastewater system is defined by the US EPA as “An onsite or cluster wastewater system that is used to treat and dispose of relatively small volumes of wastewater, generally from individual or groups of dwellings and businesses.” A comparison of a centralized vs. decentralized system is presented in the figure at right. A centralized wastewater system uses gravity or pressure sewers to transport all of the wastewater in the area to one location for treatment and disposal, usually to a stream discharge.

Decentralized wastewater disposal consists of a system of clusters. Wastewater from each cluster is transported to a smaller wastewater system for treatment and disposal. A decentralized wastewater system breaks up the service area into smaller clusters. Instead of one centralized treatment facility, there are two or more smaller, decentralized wastewater treatment facilities. The cluster treatment systems, being smaller due to the reduced cluster wastewater flow, may be on-site systems such as a mound, drip system, or spray irrigation system. It could also be a small package treatment plant that discharges to a stream.


Comparison of a centralized and decentralized wastewater system.
Source: F. X. Browne, Inc

There are several advantages to a decentralized wastewater system:

 

1.   Decentralized systems usually do not promote uncontrolled growth like centralized systems often do.

 

2.   Decentralized systems often are less expensive to construct and operate. They reduce the length of sewers needed and do not sewer unpopulated areas.

 

3.   Decentralized systems, consisting of a series of smaller wastewater flows, have a greater potential for on-site disposal. Most centralized wastewater systems require a wastewater treatment plant with stream discharge because of the larger wastewater flows being treated.

 

4.   If on-site treatment and disposal is feasible, decentralized systems, by using on-site soil disposal, provide better treatment, better meet EPA and DEP water quality antidegradation requirements, and recharge groundwater.

 

In existing lakeshore communities, decentralized systems can offer distinct benefits. Lakeshore communities often run into lake water quality problems when seasonal residences that were originally built on soils unsuitable for on-lot wastewater treatment begin to age and have septic system failures. In addition, lakeshore homes are increasingly being converted to year-round residences whose wastewater systems are insufficient to treat the increased usage. Since lakefront real estate is usually at a premium, very little land and money may exist for the construction of a centralized treatment facility, so a series of smaller, decentralized systems may be the best option. Decentralized systems can be targeted toward clusters of homes with the most serious problems, leaving newer, well-functioning septic systems out of the loop.

 

There are, however, several disadvantages to decentralized wastewater systems. They usually require more up-front soils testing to locate suitable sites. They may also require slightly higher engineering design fees. Although system maintenance is typically lower than a centralized system, it could be more complicated for multiple cluster systems.

 

In their report entitled “Response to Congress on Use of Decentralized Wastewater Treatment Systems”, the US EPA indicated concern about the gap between wastewater needs and available federal-state funding. The report indicated the need to identify and implement alternatives to costly centralized treatment and collection systems. The conclusion of the EPA report states that “adequately managed decentralized wastewater systems are a cost-effective and long-term option for meeting public health and water quality goals.”

 

EPA recently released a Program Strategy for decentralized wastewater treatment systems. This strategy presents EPA's vision, mission, and actions to improve the performance of decentralized wastewater treatment systems, thereby providing better protection of public health and water resources. The Strategy can be downloaded at http://www.epa.gov/owm/septic/pubs/septic_program_strategy.pdf

 

F. X. Browne, Inc. has extensive experience in designing and implementing decentralized wastewater treatment systems of all sizes. For more information, please contact info@fxbrowne.com.