The use of decentralized/distributed sewering is an emerging trend intended to bridge the gap between both central sewer and residential septic systems. Upgrading and improving a city’s wastewater-treatment infrastructure is one of the most important public policy issues and the most costly. Often not an environmental benefit, there is conclusive evidence that centralized sewer collection systems are leaking and causing treatment-plant overflows during strong, wet-weather events. Leakage into streams and ground water are a common occurrence in many places and a significant problem in many communities across the U.S. A study in Albuquerque, New Mexico concluded that 10 percent of average expected daily flow or [approximately] five million gallons per day at their wastewater treatment plant was lost due to leakage. With infrastructure costs rising and these types of overflow issues, alternative ways of providing wastewater service in suburban areas are gaining increasing attention.

In many situations, a decentralized/distributed system is the better way to go. Frequently seen as only a suitable choice in low-density/rural situations or for temporary solutions, the decentralized-wastewater-treatment system is not the usual choice as an option for a community – until now. With proper design, installation and operation, the advantages of decentralized systems are many. By collecting, treating, and reusing or disposing of wastewater from the homes, buildings, and/or cluster systems onsite or near the point of generation, decentralized/distributed systems can reduce the time, amount of water, and energy involved in treating wastewater with a higher pollutant removal rate. This takes the strain off an overloaded plant and provides the community with highly treated water available for reuse.

Benefits for Developers

Developers who look into alternatives to traditional sewer or center-collection systems actually see plenty of reasons to choose decentralized/distributed systems for their homes. For example, a developer who is looking to build 50 suburban homes can have his project delayed up to five years while the city extends the existing sewer lines to the homes. Plus, the developer is likely to pay significant sewer-tap fees as well as substantial fees for the cost of extending sewer lines so that current sewer customers will not have to see their rates increase. If the developer is charged more, chances are the cost increases will be passed along to the new residents. Additionally, especially in places like coastal areas, small lots and heavy regulation can tie the developer’s hands when trying to put in a sewer connection, which will further delay the development’s completion.

Because decentralized/distributed systems are typically composed of modular, interconnected, and easily replaceable parts, installation and maintenance is simple. It only takes a matter of days or weeks to install and start-up a decentralized system. The savvy developer does not have to plan as extensively in comparison to building a neighborhood with a central-sewer connection. The developer may also decide to use these decentralized systems instead of building out from the central infrastructure because they require less time and money to obtain permits. But one of the major benefits of these systems is the developer can build out slowly and add to the treatment system as needed to maintain treatment meaning the upfront costs are significantly lower.

An onsite wastewater treatment option is the small, quick-to-install, MicroFAST^® wastewater-treatment unit from Bio-Microbics, Inc., based in Shawnee, KS. These modular units can treat 500 gallons per day or significantly more by using a cluster system treating from 3,000 up to 160,000+ gallons/day—enough to accommodate an entire community. These advanced systems treat the water to considerably higher standards for subsurface irrigation or other reuse method. These units are easily upgradable, scalable, and take up considerably less space than centralized treatment options.

Moreover, these advanced treatment systems offer a water-reuse opportunity for community parks, schools, golf courses and reduce potable water consumption for non-potable uses. The developer also has more options in terms of the topography and/or type of land available, which not only increases property value but can lead to a decrease in urban sprawl.

Benefits for Residents

Homeowners generally do not like to think about sewage treatment. Quite frequently, a neighborhood near a large treatment plant will be irritated by its smell, noise or appearance. Odor is usually less of a concern with decentralized/distributed systems and they are practically unseen because they can be installed below ground.

Since the size of land normally reserved for the drain field on a given property can be reduced by using individual, onsite systems or eliminated by using cluster systems, the residual land can be used for other structures like a swimming pool or common areas like parks and green space.  Additionally, [the effluent of] these systems can be reused for drip-tube irrigation of a lawn or other landscaped areas.

Whenever a community has a centralized wastewater system and developments are proposed, questions are likely to arise over how the costs and benefits of the system are to be distributed, which can be avoided when all the costs and benefits go to single homes or clustered developments. Also important to consider is the fact that property near large, centralized systems decreases in value, which is understandable. Houses with individual or distributed systems have a more equal distribution of value. In addition, distributed/decentralized systems are often much more economical for smaller communities than sewers.

What do you really know about Septic Systems?

One of the greatest concerns with individual-home, conventional a septic system is the lack of background information and knowledge. When developers contract with a septic company or individual to install onsite systems, they are looking to minimize costs by adhering to the minimum standards instead of looking to protect the environment. Sometimes they are simply unaware that other alternatives exist. Usually the failures are characterized by very unpleasant events affecting an entire development of homes where the systems were not designed or installed properly. These events are things like untreated wastewater surfacing on the ground or backing up into the houses. Thus, many have assumed that onsite systems simply cannot be reliable. These frequent system failures are associated with the various types of conventional septic systems.

Decentralized systems (also known as advanced wastewater treatment systems) utilize proven technology which is designed, installed, and maintained ­correctly, without the use of harsh chemicals. By providing a larger decentralized/distributed system for the entire community, the maintenance is handled by a professional and requires little, if any, assistance from the homeowners. By reading the owner’s manual of any treatment system, however, the homeowners can help to take care of their system and extend its life. In it, homeowners are reminded that things like paint thinners, medicines, and even liquid fabric softeners can be harmful to a septic system. Regular inspection and pump-out of septic tanks also goes a long way in reducing failures. A professional should always do such maintenance to a system. The good news is that decentralized ­systems require less operation and maintenance than centralized wastewater-treatment plants, and therefore can be less costly to maintain overall. The added benefit is that the community is able to reuse the water for common areas, such as irrigating the landscaping and lawns—parks schools, pool areas, embankments—helping to reduce HOA maintenance costs.

Environmentally Conscious

With centralized systems, untreated water sometimes gets released into the environment, whether due to aging infrastructure, water-main breaks, flooding, or poor operation. Properly designed, installed, and operated decentralized/distributed wastewater systems have significantly cleaner effluent than centralized systems. Often, minimal energy is needed to create this superior effluent. Using again the example of the FAST^® unit from Bio-Microbics with the SFR^® (Sequencing Fixed Reactor) feature that comes integral on every FAST^® system control panel, the blower can be cycled on and off for two reasons: reduced energy operating cost (up to 45%) and improved nitrogen reduction performance (in specific situations).

A great concern of the EPA is the amount of nitrates a system releases into the environment, which can enter groundwater and under the right conditions are implicit in causing certain birth defects and are thought to cause other disorders like hyperthyroidism. If too many nitrates enter a pond or lake, they create algae, which reduce oxygen levels in the water and can result in fish kills. Many centralized systems remove hardly any nitrates, while some distributed/decentralized systems remove an impressive amount of nitrates.

Water-table levels and stream base flows can be adversely affected by centralized systems and are improved or preserved by the use of decentralized/distributed systems. Centralized systems do not discharge their effluent anywhere near where the homes or businesses use and/or obtain their water. Thus, many streams lose their water to these systems. With decentralized systems, the water goes into the nearby leach field and potentially back into the stream. Also important to note is that riparian zones (the area between land and a stream) are less frequently disturbed by the installation and operation of onsite systems than they are by central-sewer systems.

Conclusions 

Decentralized/distributed systems offer an important alternative to individual home septic systems or central municipal sewer. It is very important for developers and residents to decide what type of wastewater system is most feasible to implement, economically, politically and environmentally. With the expectation of high-quality sewer service, the community is left with an established long-term management infrastructure. Land-use planners will see less sprawl and a greater mix of development densities and greater opportunity for desirable green spaces and community amenities. Development can occur while protecting and enhancing the environment. Developers can achieve density goals at affordable economics, resulting in higher net profits. It is not always a clear choice, but there is substantial evidence that decentralized systems are very frequently the answer. They are less of a trouble for responsible builders and homeowners, and they are friendlier to the environment.

The bottom line is that distributed/decentralized/alternative and clustered, onsite advanced wastewater treatment systems are in many ways preferable to centralized sewer systems because of their economic, political and environmental advantages. 

About the authors: Jennifer Cisneros is the marketing communications coordinator and ­Allison Blodig, REHS, is the manager of regulatory affairs and special projects for Bio-Microbics. Cisneros can be reached at (913) 422-0707 or jcisneros@biomicrobics.com. For more information, go to: ­www.biomicrobics.com