EcoEng Newsletter No. 11, October 2005

Peering beyond the end of the pipe: Non-monetary methods for comparing wastewater treatment options

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 Barton Kirk, SEEDS, USA
Carl Etnier, Stone Environmental Inc., USA
Erik Kärrman, Ecoloop, SE

Barton Kirk:
East Coast Office
22 North Ave., Suite 10
Burlington, VT 05401, USA

Barton Kirk is a graduate student at the University of Vermont (USA) studying ecological economics, planning, and design in the Rubenstein School of Environment and Natural Resources. He completed his recent work for the (US) National Decentralized Water Resources Capacity Development Project as an engineer and researcher for Ocean Arks International. In addition to his graduate studies, Barton currently provides water systems engineering for SEEDS, a non-profit organization offering incubation of projects and ideas committed to sustainability.



  Conventional methods for evaluating the consequences of wastewater treatment systems typically use economic criteria and environmental criteria which only take into account the direct effect of effluent on receiving waters, disregarding indirect and cumulative environmental effects. True environmental and social costs of wastewater treatment are often not included in decision making. Many communities face decisions regarding integrative waste and water management, centralized versus decentralized wastewater treatment, as well as choices amongst numerous strategies and technologies available within the centralized and decentralized sectors. This paper summarizes a report 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).

Introduction and Background

  As communities and institutions move in the direction of sustainable development, there is a growing interest in evaluating the sustainability of the water and waste infrastructure. This interest stems, in part, from the role these systems and their management may have in shaping the nature of future development. Wastewater treatment systems generally require a large commitment of resources per end user and are expected to function for a relatively long period of time. A chosen system will generally be in use for several decades with limited options for change. And as communities are developed around these systems, it becomes increasingly difficult to consider other options, both physically and institutionally. The consequences of today's wastewater decisions matter.

Currently, decisions in the US regarding waste and water systems are based primarily on economics and consider a very limited set of treatment options. These economic considerations often focus on capital cost, with considerably less emphasis on the life-cycle costs or operational costs placed on the user. In cases where non-monetary impacts are accounted, only odor and the direct impacts of the wastewater effluent on receiving waters are typically weighed. As a result, the true environmental and social costs of wastewater treatment are often not included in decision making. Combined sewer overflows, heavy metal contamination of agricultural land, and disruption of hydrological cycles serve as regular reminders of the unexpected, direct, indirect, and cumulative impacts of wastewater treatment decisions.

Throughout the second half of the 20th century, scientists and engineers - and even historians and social critics - have questioned whether wastewater treatment is providing a net benefit to the environment and society. Their observations suggest that our conventional methods of conveyance and treatment may be simply moving problems in time and space, to be dealt with later or by someone else or both. (Antonucci and Schaumberg, 1975; Illich, 1986; Tarr, 1996; Tillman et al., 1998)

A study published as early as 1975 by Antonucci and Schaumberg may have been the first to evaluate this concern quantitatively and systematically. Their early attempt to understand and account for the total (direct and indirect) environmental impact of wastewater systems was an evaluation of the South Lake Tahoe (Nevada, USA) plant, which was considered one of the most advanced systems in the world (Antonucci and Schaumberg, 1975). The authors documented that the advanced treatment processes required exponentially increasing energy use, indirectly resulting in increased air emissions; as well as processes which directly transferred pollutants from the water to the air; or processes which utilized chemicals produced from energy-intensive and polluting processes in other locations.

Since that time, Europe, and particularly Sweden, has led the charge to evaluate the sustainability of urban water and waste systems (Balkema, 1998; Lundin et al., 2000; Tillman et al., 1998). Several methods and analytic tools have been developed, applied, and compared, primarily in the European context (Bengtsson et al., 1997; Björklund et al., 2001; Brix, 1999; Dennison et al., 1998; Dixon et al., 2003; Emmerson et al., 1995; Hellström and Kärrman, 1997; Jeppsson and Hellström, 2002; Jönsson, 2002; Kärrman et al., 2004). Using such tools, European analysts have added other considerations also missing from conventional comparisons of wastewater treatment options. These studies expanded the evaluations to include the resulting societal and environmental effects of wastewater system interactions with other technical systems, both upstream (e.g., input systems, such as drinking water and stormwater, in addition to chemical and energy systems) and downstream from the wastewater treatment system (e.g., potential users of biosolids, biogas, and reclaimed water; such as agriculture, industry, and energy producers) (Sundberg et al., 2004; Tillman et al., 1998).

These methods have been developed but not used much. This is particularly true for decisions regarding onsite and decentralized systems, where regulation generally requires little analysis. In these cases, property owners, developers, and designers tend to respond to the least capital cost, minimum regulatory compliance, and/or the most conventional practices. For many of those involved in making wastewater decisions, it may be difficult to look much further beyond minimum capital cost and minimum regulatory compliance without incentives to do otherwise. However, as communities have begun to make written commitments to sustainability, as the conservation and protection of regional and global resources becomes a priority, and as the concepts of green building and sustainable development rapidly increase in popularity, decision making tools which assist in comparing the sustainability of water and waste systems are becoming increasingly relevant.

This paper summarizes material presented in a report for the National Decentralized Water Resources Capacity Development Project (NDWRCDP) entitled "Methods for Comparison of Wastewater Treatment Options," which sought to identify formal analytical tools with the potential to compare the non-monetary impacts of wastewater treatment options, determine which methods if any were most appropriate for use in the US by wastewater treatment decision makers, and identify the barriers to implementation in the US.



  The study began with an extensive review of US and European literature on methods for comparing wastewater treatment options, complemented by a review of databases and the availability of data required for each method. Discussions with US and European researchers and practitioners helped determine how the methods worked, and how well. Interviews with US decision-makers gave a sense of what types of comparison tools might be needed, as well as what barriers exist to implementation and the relative magnitude of those barriers.

The methods were evaluated in the context of several wastewater decision-making situations facing decision-makers and actual case studies, both with considerations of the resources available and the barriers to implementing formal analytical tools for comparing wastewater treatment options.


Review of methods

  From the review of literature, research, and case studies, 18 methods with potential relevance to comparing wastewater treatment options were examined. Within these, three methodologies emerged: life-cycle assessment (LCA); environmental impact assessment (EIA); and open wastewater planning (OWP) where:
  • LCA is a method of accounting for the environmental impacts of a product, service, or process over the course of its life cycle, from extraction of materials to disposal or reuse of the final product;
  • EIA is a framework for identifying, predicting, evaluating, and mitigating the biophysical, social, and other effects of proposed projects or plans and physical activities; and
  • OWP is a participatory approach to wastewater decision making which broadens the boundaries of options considered and expands typical evaluation criteria to include indirect environment impacts.

EIA as a formal process was developed in the US, but is used worldwide. In the US, it is used for all federally-funded and many state-level wastewater treatment projects. LCA, while actively used in many industry sectors in the US, has not been applied to wastewater as it has in Europe - and in Europe, it has been used more by researchers than decision makers. OWP is a much less formalized process developed specifically for wastewater decision making which has been used successfully in Sweden and the Baltic Sea Region.


Methods applied

  Examples help clarify how the methods work. Below, the methods are described in greater detail, and brief case studies show how the methods are applied.

Life-Cycle Assessment

Life-cycle assessment is the most standardized and quantified evaluation methodology of those compared. In its broadest definition, LCA is a summation of all environmental burdens that occur from "cradle to grave" during a product’s or service’s life cycle: the extraction of raw materials; transportation; manufacturing; operation, maintenance, and reuse; and disposal of wastes. The environmental burdens of concern generally include use of land, energy, water, and other materials and the release of substances (harmful and beneficial) to the air, water, and soil. The evaluation typically proceeds as follows:

  • Goal and scope definition. This includes the purpose of the study, the system boundaries, and the functional unit of comparison. A material and energy flow chart is also mapped.
  • Life-cycle inventory (LCI). In this phase, all information on emissions and the resource consumption of the activities in the system under study are catalogued.
  • Life-cycle impact assessment (LCIA). In this phase, the environmental consequences of the inventory are assessed and sensitivity analyses of the results are developed. This typically includes aggregation of the inventory into impact categories (Table 1).
  • Interpretation. This fourth but controversial step occasionally included by some LCA methods is the interpretation of the results, which may include normalization, weighting and/or additional aggregation.
Table 1: LCA Impact categories
  This description is consistent with the standards developed for LCA by the International Standards Organization (ISO) as part of its 14000 series on environmental management. These standards address both the technical details and conceptual organization of LCA and are widely accepted (Guinee, 2001). While the standards do attempt to maintain consistency between studies, they do allow for and recommend some customization of the method to adjust for limitations in data availability and the needs and goals of the decision makers.

LCA applied – Bergsjön and Hamburgsund, Sweden

A customized LCA of wastewater treatment options which has received particular attention was conducted as part of the Swedish ECO-GUIDE project. Tillman et al. (1998) evaluated several hypothetical wastewater treatment scenarios. The study included a life-cycle comparison of wastewater treatment options for two Swedish locations: Bergsjön, a section of the city of Gothenburg; and Hamburgsund, a coastal town with 900 year-round residents.

The primary purpose of the study was to determine the environmental impacts of using more localized treatment with increased recycling of nutrients. A second, but important, intention of the study was to compare the environmental impacts associated with the construction of the system components ("investment") with those arsing from the operational activities of the system.

In Bergsjön, the existing wastewater treatment system (Alt 0) was a conventional centralized system with denitrification and biogas production. Hamburgsund had a small conventional system, with sludge transported to a larger facility for processing. For each case, the existing system was compared with two decentralized options:

  1. Alt 1 - Utilizing the existing collection system and plumbing, solids are collected at the residences and transported to local digestion and drying facilities, while the liquids are treated on site in sand filters and then piped to a constructed wetland. The solids are used as fertilizer.
  2. Alt 2 – Graywater, urine, and feces are separated using urine-diverting ("no-mix") toilets and additional plumbing. The graywater is treated on site in sand filters. Feces, flushwater, and graywater solids are collected at the residences and digested and dried locally. The urine and solids are used as fertilizer.

In defining the goal and scope of analysis, Tillman et al. (1998) expanded the system boundaries to more accurately compare the environmental impacts of options focused on conserving and recovering water, energy, and nutrients in wastewater treatment. They understood that changes in the existing wastewater facilities could decrease drinking water use (with low-flow toilets); reduce energy consumption, through biogas production; and reduce use of chemicals fertilizers, through agricultural use of urine and treated solids. Accordingly, Tillman et al. (1998) included additional technical systems in what they defined as the extended system (in contrast to the the core system for wastewater treatment (Figure 1)).

Figure 1: Flow chart of the core wastewater treatment and extended system boundaries. Adapted from: Tillman et al. (1998).
  The researchers compiled an extensive inventory of resources used, substances emitted, and wastes produced for each activity in the two systems. This included inventories of the material and energetic "investment" in and operation of the core system (Table 2) as well as an inventory of the operation of the extended system. The inventory of operations resulted from an analysis of the material and energy flows across the system boundaries to and from nature, as well as, to and from other components of the technical system.
Table 2: Inventory results of the operation of Bergsjön’s core system (per person equivalent / yr). Adapted from Tillman et al. (1998)
  To compare the three scenarios (Alt 0, 1, and 2) for each of the two towns, Tillman et al. (1998) employed a customized LCA methodology. Their approach generally follows the ISO guidelines for goal and scope definition and inventory analysis, but for the core system stops short of impact assessment of the inventory results, a step which is typically taken to help decision makers make sense of the extensive inventory so that they can begin to weigh the information. The inventory results were instead used directly for discussion amongst the researchers, avoiding some of the subjectivity introduced by assessment methods but also requiring that the decision makers be able to characterize the resultant impacts of the emissions and resource uses they are comparing.

For the analysis of the inventory results of the extended system, impact assessment and weighting methods were applied. The details of this analysis are not extensively reported except to say that the impact assessment and weighting were not used to rank the options, but rather to determine the most important parameters for discussion.

Some of the key findings and conclusions reported by Tillman et al. (1998) include:

Core system:

  • For the small town of Hamburgsund, the operational impact was clearly larger than the impact of the investment.
  • For Bergsjön, where the scale was considerably larger, the distinction was less apparent.
  • The impacts of the "investment" varied less over the alternatives than those of the operation.

Extended system:

  • The lowest level of nitrogen emissions to water was found with the urine-diverting alternative (Alt 2), followed by the existing centralized plant (Alt 0).
  • The centralized system (Alt 0) in both locations used considerably more energy than the decentralized systems for the core system. In Hamburgsund, this relationship carried through to the extended system. In Bergsjön, however, a heat pump extracted heat from the wastewater in the centralized system, and the heat was used to warm buildings. This made the extended centralized system a net producer of fossil energy, while the decentralized systems were both net consumers of fossil energy.
  • Phosphorus can be measured both in emissions to water and in use of raw phosphate in fertilizer - and the two yardsticks give much different results. In Bergsjön, phosphorus emissions to water were slightly lower for the existing system (Alt 0) than the urine-diverting alternative (Alt 2) and half that of Alt 1.All alternatives resulted in net reductions in the use of raw phosphate, since recycled nutrients from the wastewater replaced chemical fertilizer. However, the urine-diverting alternative resulted in about a 25% greater reduction in raw phosphate use than the other two alternatives.
  Environmental Impact Assessment

Environmental impact assessment is generally a more familiar method in the US, as it is often a bureaucratically required process used to insure that environmental and other non-monetary concerns are considered in the process of planning government funded or regulated projects. EIA is a process of identifying, predicting, evaluating, and mitigating the biophysical, social, and other relevant effects of proposed projects or plans and physical activities prior to major decisions and commitments being made. EIA was introduced in response to the US National Environmental Protection Act (NEPA) of 1968 and the US Environmental Quality Improvement Act of 1970, which mandated that all federal agencies systematically integrate environmental concerns into the planning and decision making for all Federal projects, plans, and activities. Since then, NEPA-like policies have been adopted and adapted by 20 of the 50 United States for state-level projects and by many countries world-wide, including the European Community (Kontos and Asano, 1996).

The general procedure for EIAs includes the following steps:

  1. Scoping. Identify key issues and concerns.
  2. Screening. Decide whether an EIA is needed (e.g., is there a significant environmental impact?)
  3. Identify Alternatives. List the alternatives, sites, and techniques; and describe the affected environment.
  4. Assess Impacts. Assess the social and environmental impacts of each alternative
  5. Mitigation Measures. Develop mitigating actions to prevent or reduce potential impacts
  6. Issue Environmental Statement. Produce a non-technical report on findings of the EIA

Steps 2, 5, and 6 are unique to EIAs when compared to LCA. Step 3 is similar to the LCI step of LCA, but it in practice it has been less comprehensive. Likewise, at first glance step 4 is similar to the LCIA step of LCA, but is not nearly as standardized. In Table 3 Kontos and Asano offer eight generic impact categories for consideration in step 4 (Kontos and Asano, 1996).

Table 3. EIA Generic Impact Categories
  The Draft Environmental Impact Report (EIR) prepared for a wastewater treatment plant in Willits, California, provides an example of a state NEPA-like process (Planwest Partners et al., 2002). The city’s wastewater treatment plant has a capacity of 1.3 million gallons per day and was 25 years old at the time the EIR was prepared. Much of the key equipment was wearing out or close to wearing out. The wastewater collection system was wearing out as well, and high levels of inflow and infiltration occurred during the winter rainy season. Furthermore, the plant had exceeded 75% of design capacity, an indicator used by the local regulators to show a need for upgrading for future demand increases, and it was regularly violating its discharge permit limit of 1% of the hydraulic flow of the receiving water, Outlet Creek. After a three-year facility plan process, the Proposed Project was selected and an EIR was prepared. The EIR cost about $250,000 to produce and took about two years to complete (Herman, 2004).

Overall goals were set for any improvements in the wastewater treatment system:

  1. "Provide wastewater treatment and disposal (sic) to accommodate 20 years of expected growth in the City of Willits service area, and
  2. "Develop and operate the wastewater treatment and disposal (sic) system in ways that protect public health and safety and promote the wise use of water resources."

In addition, project objectives were defined, including addressing cost effectiveness, reliability, and providing recreational opportunities on the open space used for wastewater treatment. Through review of recent engineering documents, a proposed project was developed, along with three alternatives and a "no project" alternative. The proposed project included:

  • Changing from a mechanical extended aeration activated sludge process to an oxidation pond and constructed wetland on a larger site,
  • Changing the disinfection method from chlorination to ultraviolet light
  • Adding longer on-site retention, and
  • Moving the points of discharge and storage downstream.

The disadvantages of the "no project" alternative were described, and the proposed project and alternatives were evaluated according to a host of criteria (Table 4):

Table 4. EIA Evaluation Criteria
  Interestingly, the "environmentally superior alternative" was selected, without considering non-environmental factors like cost and access to the site. After hundreds of pages of consideration of the above impacts, the justification for selecting the proposed project as the environmentally superior alternative was surprisingly short: "Due to reduced hydrological and wetlands impacts, and other factors, compared to the other alternatives, the Proposed Project is considered the environmentally superior alternative."

The EIA methodology could be combined with a more sophisticated way of aggregating the comparisons on each of the criteria into a final choice of the "environmentally superior alternative."

  Open Wastewater Plannning

Open wastewater planning is a newer, less well known, and less formalized method than LCA or EIA. It has been developed especially for wastewater treatment decisions. OWP begins by setting goals for the wastewater treatment process. The decision makers may be guided in their goal setting by a third party (e.g., a consultant and/or regulators), but it is crucial that the decision makers take ownership of the goals. When the goals are set, a third party generates a diverse set of design alternatives which meet most or all of those goals and presents them simply, at the level of a feasibility study. The ways in which the alternatives affect the established goals are described briefly, and decision makers use the material as a decision aid.

The general procedure for OWP is quite simple and includes the following steps:

  1. Define goals and system boundaries,
  2. Identify alternatives,
  3. Develop criteria to evaluate alternatives, and
  4. Compare alternatives.

This process has been used on a limited basis in Sweden, and a document describing a case study of the process in English has been distributed to promote OWP as a model to use throughout the Baltic Sea region (Ridderstolpe, 1999).

OWP applied – Vadsbro, Sweden

The successful case study documented by Ridderstople is that of Vadsbro, Sweden, a village of forty households, in the same region as Stockholm [see also EcoEng-Newsletter No. 1/2000, the editor]. The village had renovated the sewer system connected to failing wastewater treatment plant. Their next step was to upgrade the treatment plant. The regulatory authority, the municipality’s Environmental and Public Health Committee, believed that a package treatment plant was the appropriate solution, but they wanted to work with someone to confirm that choice. They embarked on a two-month process of OWP, which cost them 35,000 kronor (about $4,400) in consulting fees (Ridderstolpe, 2004).

Ridderstolpe began by asking the Committee what their goals for the wastewater treatment plant were. They identified measurable goals in the areas of cost, nutrient and BOD removal, potential for recycling nutrients, energy use, chemical use, and public health, as well as qualitative goals that the solution fit in with local conditions and that responsibility and maintenance requirements be clear. Ridderstolpe then developed six alternatives, including the package treatment plant, which more or less met the criteria. The other alternatives were quite different from one another:

  • Land application of wastewater: Bio-fuel plantation irrigation
  • Stabilization pond with calcium hydroxide precipitation
  • Packed media filter plus biofilter ditch (a long, narrow wetland)
  • Land application of wastewater: Crop-wetland rotation
  • Sand filter

The Committee was surprised that the criteria could be fulfilled by such widely varying options. They were aided in deciding among all the options by a report with two-page spreads on each alternative. The first page was a textual description of the alternative, with information about how it fulfilled the chosen criteria. The second page contained a sketch or sketches of the system, and a very short summary of how the system performed over the criteria (Figure 2).

Figure 2: Open wastewater planning: A summary sketch of Vadsbro’s alternative 2: Stablization ponds with chemical precipitation. Source: (Ridderstolpe, 1999)
  The relative strengths and weaknesses of the alternatives were compared on a single chart (Figure 3). The chart is not a formal decision-making tool; there are no specific definitions for the differences between two plusses and three plusses, for example, and there is no method for adding the plusses and minuses together. Rather, the chart is more a means of semi-quantitative visualization. The descriptions of each treatment alternative provide the details of the way the alternative performs according to each criterion; the chart in Figure 3 merely provides an overview to be used in deliberations. The Committee used all of these aids in discussing their way to a decision: the filter bed followed by a biofilter ditch - a type of long, thin wetland.
  The selection of criteria is as important to the outcome of the process as the options considered. In the Vadsbro case, Ridderstolpe (2002) suggested to the Committee the criteria they used. The method could be made more generally applicable by drawing up a long list of criteria from which to select.

Comparison of methods

  The primary difference between environmental impact assessment and life-cycle assessment is that EIA is a framework for conducting assessments, not a precise method for analysis. For most practical purposes, LCA is associated with specific methods of analysis. Within EIA there are no assigned or standardized categories or methods of analysis for those categories.

This difference is due to differences in the scope of assessment between EIA and LCA. EIA generally addresses more localized impacts and allows for the most appropriate methods for the uniqueness of the site and significant impacts. However, the flexibility of the EIA process, combined with less attention to system boundaries, allows some indirect and cumulative impacts to be skipped, particularly those which affect other locations or which are regional or global in scale. The standard LCA methods, on the other hand, are virtually incapable of detailing most local impacts, but generally provide the most reliably complete quantification of net environmental impact from a regional or global perspective.

Since the environmental impacts of wastewater treatment occur at both local and global scales, environmental sustainability generally requires considerations of both (Balkema et al., 1998). Fortunately, EIA and LCA do not appear to be mutually exclusive; they are more likely complimentary. In fact for LCA to be included in US decision making in a systemic way, some complementary association of these items is likely necessary. EIA is often the means to meeting state or federal environmental laws; LCA can add a broader perspective to the analysis.

Open wastewater planning may adopt characteristics of both LCA and EIA, but is most similar to EIA. OWP may adopt the system boundaries of analysis and global or regional impact assessment characteristic of LCA, but OWP’s flexibility to adapt to the decision making needs and context mimic the framework of EIA. Unfortunately this also makes OWP more vulnerable to allowing decision makers to ignore externalities. An aspect which is unique to OWP is that it is developed specifically for wastewater treatment. Another is that it is practical for smaller-scale decisions or smaller communities, particularly those with less monetary and human resources.

Open wastewater planning may share the methodology of LCA and EIA, but is more than a formal analytical model; it is a decision-making method, from framing the problem to choosing among alternatives. The beauty of open wastewater planning lies in its simplicity and its adaptation to local conditions, as well as its flexibility in identifying various non-economic criteria to use in judging wastewater treatment alternatives. By helping the decision makers identify which criteria are most important to them, it is possible to concentrate data gathering on information which will make a difference for the decision. It is also possible to gauge the level of sophistication needed in the analysis to provide useful information. The analysis can then use any of the methods discussed in this report, or others, and streamline any LCA component as appropriate. The method has been used in relatively small decisions like Vadsbro. The larger the project and the larger the constellation of interest groups, the greater the demand is likely to be for a more formally documented process. As the formal documentation increases, the OWP process begins to resemble environmental impact assessment more.

Table 5 summarizes the comparison of the three general methodologies considered for assessing the non-monetary impacts of wastewater treatment options.

Table 5: Comparison of three general methodologies
  The example applications described earlier are indicative of how each of the methods are currently used and to what types of decisions and decision makers the methods provide the most utility. The LCA application was conducted for research purposes and produced results which answered questions about how the methodology affected results, as well has how various hypothetical scenarios might result in quantified amounts of resources consumed and emissions released to the environment. The EIR in the second application was a bureaucratic requirement and was used as legal documentation of the environmental justification for the proposed project. Conversely, the OWP application demonstrated how OWP can be integrated into and guides the decision-making process from the onset and is targeted at identifying and choosing amongst wastewater treatment options, attempting to provide just enough analysis and information for small community decision makers to objectively compare systems in a holistic manner.

None of the methods are limited to these applications however. LCA is not limited to research or policy level studies, rather it also has been used extensively for design purposes in other industries as means of increasing both eco-efficiency and eco-efficacy. EIA may be streamlined and applied to the planning process, independent of governmental policy, in which case it begins to function more like OWP. Likewise OWP may be increasingly formalized to mimic more of the EIA process.

Together these methodologies cover a good deal of the analysis and decision-making support needed to holistically assess the non-monetary impacts of wastewater treatment options. And because each methodology will continue to benefit greatly from further development of the specific analysis methods, software, and data resources, there are great advances to be made in appropriately applying LCA, EIA, or OWP to the wastewater management decisions facing our communities today.


Summary and conclusion

  Of the methodologies, environmental impact assessment and open wastewater planning are broader frameworks for assessment and planning, within which life-cycle assessment methods may be used to more completely account for impacts. Of these, OWP was developed specifically for wastewater decision making and offers more flexibility in the breadth and depth of analysis and formality. EIA is already in use world-wide for wastewater treatment, but it is not clear how much EIA affects choice of treatment alternatives. LCA is currently most suitable for research and policy-level studies requiring highly quantitative results at broader scale, but requires a significant investment in data development to be useful.

Recommendations for the US:

  • Begin employing OWP for internal or participatory decision making in wastewater treatment projects right now.
  • If required to conduct an EIA, consider incorporating the LCA methodology into the process to reduce the risk that impacts are being shifted in time or space.
  • At a research level, continue conducting LCAs of wastewater treatment to improve the global methodology and data resources to make the methods more accessible to decision-makers and allow for more objective and accurate comparisons of the non-monetary impacts of WWT options.

**Note – In addition to the items discussed in this summary, the 200 page parent document contains other important resources including discussions on selecting system boundaries and evaluation criteria, methods for streamlining analyses, a review of data availability, comparison matrices of previous studies and promising electronic and online databases, and others.

The full report may be downloaded at or hard copies may be ordered from the US National Small Flows Clearinghouse at

For further information please contact the author.



Antonucci, D. C., and Schaumberg, F. D. (1975). Environmental effects of advanced wastewater treatment at South Lake Tahoe. Journal of Water Pollution Control Federation 47, 2694-2701.

Balkema, A. J. (1998). Sustainability criteria for the comparison of wastewater treatment technologies. In "11th European Junior Scientist Meeting: "The Myth of Cycles versus Sustainable Water and Material Flux Management"", Wildpark Eekholt, Germany.

Balkema, A. J., Weijers, S. R., and Lambert, F. J. D. (1998). On methodologies for comparison of wastewater treatment systems with respect to sustainability. In "WIMEK Conference "Options for closed water systems"", Wageningen, the Netherlands.

Bengtsson, M., Lundin, M., and Sverker, M. (1997). "Life cycle assessment of wastewater systems: Case studies of conventional treatment, urine sorting, and liquid composting in three Swedish municipalities," Rep. No. 1997:9. Technical Environmental Planning, Chalmers University of Technology, Gothenburg, Sweden.

Björklund, J., Geber, U., and Rydberg, T. (2001). Emergy analysis of municipal wastewater treatment and generation of electricity by digestion of sewage sludge. Resources Conservation and Recycling 31, 293-316.

Brix, H. (1999). How 'green' are aquaculture, constructed wetlands and conventional wastewwater treatment systems? Water Science and Technology 40, 45-50.

Dennison, F. J., Azapagic, A., Clift, R., and Colbourne, J. S. (1998). Assessing management options for wastewater treatment works in the context of life cycle assessment. Water Science and Technology 38, 23-30.

Dixon, A., Simon, M., and Burkitt, T. (2003). Assessing the environmental impact of two options for small-scale wastewater treatment: comparing a reedbed and an aerated biological filter using a life cycle approach. Ecological Engineering 20, 297-308.

Emmerson, R. H. C., Morse, G. K., Lester, J. N., and Edge, D. R. (1995). Life-cycle analysis of small-scale sewage treatment processes. J. CIWEM 9.

Guinee, J. (2001). "Life cycle assessment: An operational guide to the ISO standards." CML (Centre of Environmental Science) Leiden University, Leiden, The Netherlands.

Hellström, D., and Kärrman, E. (1997). Exergy analysis and nutrient flows of various sewerage systems. Water Science and Technology 35, 135-144.

Herman, T. (2004). Personal Communication with Carl Etnier.

Illich, I. (1986). "H2O and the waters of forgetfulness," Marion Boyars Publishers.

Jeppsson, U., and Hellström, D. (2002). Systems analysis for environmental assessment of urban water and wastewater systems. Water Science and Technology 46, 121-129.

Jönsson, H. (2002). Urine separating sewage systems - environmental effects and resource usage. Water Science and Technology 46, 333-340.

Kärrman, E., Jeppsson, U., Van Moeffaert, D., Jönsson, H., and Hellström, D. (2004). Environmental systems analysis for sustainable wastewater and organic waste management in a country town in Sweden. submitted to Water Science and Technology.

Kontos, N., and Asano, T. (1996). Environmental assessment for wastewater reclamation and reuse projects. Water Science and Technology 33, 473-486.

Lundin, M., Bengtsson, M., and Molander, S. (2000). Life cycle assessment of wastewater systems: influence of system boundaries and scale on calculated environmental loads. Environmental Science and Technology 34, 180-186.

Planwest Partners, Graham Matthews & Associates, TCW Economics, Humboldt Water Resources, Jane Valerius Environmental Consulting, Bollard & Brennan Inc., Roscoe & Associates, and Thomas R. Payne & Associates (2002). "Willits wastewater treatment/water reclamation project draft environmental impact report," Rep. No. State Clearninghouse #2001032016. City of Willits, Willits, California.

Ridderstolpe, P. (1999). "Wastewater treatment in a small village: Options for upgrading," Rep. No. 1999:1. Water Revival Systems ekoteknik AB, Uppsala, Sweden.

Ridderstolpe, P. (2002). Personal communication with Carl Etnier. (C. Etnier, ed.).

Ridderstolpe, P. (2004). Personal communication with Carl Etnier. (C. Etnier, ed.).

Sundberg, C., Svensson, G., and Söderburg, H. (2004). Re-framing the assessment of sustainable stormwater systems. Cleaner Technology and Environmental Policy 6, 120-127.

Tarr, J. A. (1996). "The search for the ultimate sink: Urban pollution in historical perspective," The University of Akron Press, Akron, Ohio.

Tillman, A.-M., Svingby, M., and Lundstrom, H. (1998). Life Cycle Assessment of Municipal Waste Water Systems. International Journal of Life Cycle Assessment 3, 145-157.

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