EcoEng Newsletter No. 11, October 2005

NOWRA Promotes Decentralized Wastewater Treatment in the US

Content No. 11/05
Title page / Index
From the editors
Faces: H.v.Bohemen
Review: EE Book
Overview, Etnier
Kirk et al.
Composting (ch. 4)
Fecal composting
Policy Finl, Mattila
Desert infrastruct.
Writers' Fund
Ecosan Durban 05
Good bye T. Rohrer
Various issues:
Joe's Corner
Mailing list
By Carl Etnier, co-editor of the EcoEng-Newsletter

Stone Environmental, Inc.
535 Stone Cutters Way
Montpelier, Vermont 05602

Carl Etnier has worked with wastewater technologies and management for 15 years and has organized several international conferences on ecological engineering for wastewater treatment. His Ph.D. studies at the Agricultural University of Norway (currently ABD) were in decision making for sustainable wastewater treatment, and he has helped numerous communities wrestle with wastewater decisions. He currently works at the environmental science firm, Stone Environmental, in Montpelier, Vermont, where he assists communities and conducts research. He is pleased to have just been appointed Sewage Officer in his town of East Montpelier, Vermont (population approximately 2,500), where he expects to write about 30 permits a year for onsite wastewater treatment systems.


NOWRA and Ecological Engineering - a match?

  Ecological engineering for wastewater treatment is loosely - very loosely - connected with small-scale treatment systems. Yes, there are large-scale constructed wetlands or effluent fish farming operations that embody ecological engineering principals. Yet the space requirements of such treatment systems make them more the exception than the rule - it is often difficult to find land for wetland treatment systems in large cities where large-scale wastewater treatment is called for. Furthermore, making good use of the nutrients in wastewater implies re-using them in agricultural (or aquacultural) production. The short transport distances possible with decentralized wastewater/food systems are key to both environmental sustainability - energy used in transport of food and nutrients is an environmental cost - and economic sustaiability - the twenty-first century is likely to see the depletion (and thereby skyrocketing prices) of oil and other energy sources that underpin economies based on long transport distances.

For that reason, ecological engineers can learn from taking part in organizations working with decentralized wastewater treatment, even when ecological engineering is not at the heart of their work. The National Onsite Wastewater Recycling Association (NOWRA) is a US-based organization that has been promoting decentralized wastewater treatment for over a decade. This issue of Eco-Eng takes a peek at some of the work presented in the NOWRA 2004 annual conference held in Albuquerque, New Mexico last October.

NOWRA is an organization of manufacturers of equipment used in decentralized wastewater treatment, regulators, academics, and others who work with decentralized treatment. The exact scale of decentralized treatment is fuzzy; it is often explained as treatment "at or near the source." What most decentralized systems have in common, at least as seen at NOWRA's annual conference, is that the effluent is discharged to the soil. This soil-based dispersal of the effluent discharge gives rise to the WR (Wastewater Recycling) in NOWRA's name. Effluent discharged to the groundwater can recharge aquifers and/or provide groundwater flows to streams, rivers, and lakes. Alternately, the effluent can be treated to such a degree that it can be used for local irrigation or even reused for toilet flushing. (While some discussions of recycling the nutrients in wastewater have been started within NOWRA circles, nutrient recycling does not yet occupy a large part of the organization's consciousness.)

While the annual NOWRA conference and exposition has primarily attracted people from the US, many prominent NOWRA members realize that there is much decentralized wastewater work happening around the world that US-based practitioners would benefit from learning more about. At the same time, much of the work presented at NOWRA's meetings would be of wide international interest. For that reason, a NOWRA conference focused on international sharing of issues and knowledge around decentralized wastewater has been scheduled for March 10-15, 2007 in Baltimore, Maryland (on the east coast of the US, near Washington, DC). A special section of is to be dedicated to the international conference in December, 2005 and a call for papers is to be issued in January 2006. For more information about the conference, or to make suggestions for its content, please contact NOWRA's executive director, Linda Hanifin Bonner (


The selected papers


Specially revised for this issue of EcoEng, the article by Barton Kirk et al. examines formal methods to document the full environmental and social benefits and costs of wastewater treatment options. Typically, decisions on wastewater treatment options are made based only on the direct effect of effluent on receiving waters, without regard to indirect and cumulative environmental effects. Kirk et al.'s paper summarizes a report [1] that reviewed analytical tools and methods that have the potential to capture the environmental consequences of such wastewater alternatives in non-monetary units for US communities. Methods are classified into the broad methodologies of environmental impact assessment (EIA), open wastewater planning (OWP), and life-cycle assessment (LCA). The result is an international menu of options - EIA was pioneered in the US but has not typically been applied to wastewater treatment issues, OWP was developed in Sweden and is focused on wastewater, and LCA has been applied to wastewater treatment decisions primarily in Europe.

One of the unwanted environmental side-effects of using decentralized wastewater treatment in the US has been sprawl - houses have been built on large lots (0.8 – 4 hectare or larger) because regulations for the onsite wastewater treatment systems required it. Sprawl is a major environmental problem in the US, gobbling up both agricultural and wild lands and creating communities where many see the car as the only practical means of personal transportation. With today's treatment systems, it is possible to use decentralized wastewater treatment on developments of much greater density than in the past and still protect public health and the environment. High-density development is called smart growth. How to use decentralized wastewater in connection with smart growth was the focus of a series of documents developed by Scott Johnstone et al. for the planning office of Maine, a state in the northeastern US. The project is summarized in the paper included here (download as PDF) [2].

Decentralized wastewater treatment is often used in small communities that lack the resources to employ a professional planner or a public works department. Many communities have used enthusiastic volunteers to examine their wastewater needs and recommend changes. Ken Jones has observed how these volunteer committees have worked and has interviewed many people involved in the process. He documents many lessons learned and traps to avoid in a manual that can be used by small communities; the paper included (download as PDF) here summarizes that work [3].

A major issue in regulating decentralized wastewater is how to ensure that adequate treatment is taking place. For centralized facilities, it is cost effective to take effluent samples frequently - daily, or even hourly. The cost of sampling and analysis is spread over many users. For decentralized facilities, sampling and analysis costs accrue to as few as one or two individuals, and sampling can mean long trips. When the treatment consists only of a gravity-fed septic tank and a soil absorption system, or leachfield, then the soil provides most of the treatment and can be counted on to do so reliably, as long as the system is properly designed, installed, and maintained. Many advanced treatment units (ATUs) are being installed now, to provide some additional treatment before the septic tank effluent is dispersed into the soil. These are used, for example, where there are especially strict limits on nitrates discharged to the groundwater or where native soils are too shallow or otherwise incapable of providing adequate treatment. ATUs generally have moving parts, like pumps and blowers, and their performance can degrade sharply over time. In Virginia, a state on the east coast of the US, Anish Jantrania and Alan Knapp have begun a project to find a way to monitor the performance of ATUs inexpensively. Ideally, all important performance information would be monitored by an inexpensive instrument on site that uses a modem to telephone in its readings. Their paper here explains how they have set up the project (download as PDF).

With more complicated systems like ATUs being installed, it becomes more important to understand the long-term reliability of systems and their components. The reliability affects the life-cycle cost of a system - a system with a major component that requires replacement every year costs more in the long run than an identical system where the component is replaced every ten years. Life-cycle cost is important to understand when deciding which treatment system to install. For systems already installed, reliability information can help in scheduling maintenance routines, so they are frequent and thorough enough to discover or prevent critical problems in a timely manner, without being inordinately expensive. Etnier et al. have studied asset management and reliability tools used in centralized wastewater treatment and other industries, and they illustrate how the tools can be applied to decentralized wastewater treatment. The paper here describes their findings (download as PDF) [4].

These papers provide just a small glimpse into the world explored at NOWRA's annual conferences. For more information on upcoming NOWRA events, and to inquire about obtaining proceedings from previous conferences, go to NOWRA's web site

1: The full report is available at

2: All the documents produced during the project are available at

3: The full report is available at

4: The full report is available at

© 2005, International Ecological Engineering Society, Wolhusen, Switzerland