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Outdated legacy systems include stone and pipe leachfields.

U.S. engineering schools are still catching up with decentralized wastewater treatment systems course delivery.

By Robert L. Siegrist. Ph.D., .PE., BCEE

For nearly a generation, the virtues and benefits of decentralized systems for water supply and sanitation have been widely recognized and approaches, devices, and technologies have been advocated as critical components for a sustainable 21st Century. Yet, the principles and practices of modern decentralized systems have not yet been broadly incorporated into curriculum within U.S. higher education.

Needs and options evolve

In the United States, systems for water supply and sanitation evolved during the 20th Century in response to a growing recognition that providing safe drinking water and adequate treatment of wastewaters were needed to protect public health and preserve water quality. During this evolution, there was a mix of systems, with the relative proportion of the U.S. population and development served by the different system types varying and evolving over time to broadly include two system types — those serving individual homes, businesses, and mixed-use developments in rural and suburban areas; and large centralized systems serving densely populated urban areas.

Today, nearly 30 percent of individual household wastewater treatment systems in the U.S. are decentralized and approximately 35 percent of new development is supported by such systems. This amounts to roughly 25 million existing systems with about 200,000 new systems being installed each year.

The growing interest in sustainability has contributed to an increasing interest in modern decentralized wastewater treatment as a more widespread solution due the significant benefits that can be realized, including:

  • conserving potable water by reclaiming water for nonpotable use;
  • preventing combined sewer overflow pollutant discharges;
  • recharging local water resources near the point of water extraction;
  • enabling recovery and reuse of wastewater resources, including water, organic matter, nutrients, and energy;
  • lowering consumption of energy and chemicals;
  • reducing greenhouse gas emissions;
  • improving resilience to natural disasters and climate change; and
  • earning points for a green building or sustainability rating.

During this period, there was also a growing recognition that the capabilities of 21st Century decentralized systems should not be judged based on the performance of older 20th Century systems. The outdated systems (e.g., cesspools, seepage pits, non-code compliant systems) were typically installed to be simple and cheap methods of wastewater disposal. During the latter decades of the 20th Century, increased water use and wastewater generation and more widespread use of disposal-based systems in a growing suburban America, contributed to occurrences of hydraulic malfunctions, groundwater contamination, and surface water quality deterioration. To properly distinguish and refer to these older disposal-based systems, they became known as “legacy systems.” In contrast to the legacy systems, modern decentralized systems can be designed for effective treatment as well as resource conservation and recovery.

Based on major research and development efforts during the last two decades or longer, modern decentralized systems have evolved to include a growing array of approaches, devices, and technologies that can be used to serve buildings and developments with design flows of less than 100 gallons per day to 100,000 gallons per day or more.

The purpose of common and emerging applications within the U.S. include to:

  • provide effective wastewater treatment for homes and businesses in rural and peri-urban areas and residential, commercial, and mixed-use developments in suburban areas;
  • provide nutrient attenuation in environmentally sensitive areas;
  • provide effective wastewater treatment for buildings and developments while also producing a reclaimed water for nonpotable reuse purposes such as toilet flushing or irrigation;
  • recover valuable wastewater resources, including nutrients, organic matter, and energy; and
  • earn points for a green building or sustainability rating through the low impact water and wastewater management options enabled by decentralized systems.

Applications worldwide are similar but also encompass safe drinking water and adequate sanitation in developing regions of the world.

Engineering course delivery

New wastewater treatment plant with 2.0 million-gallon-per-day Infiltrator Chamber drainfield solves effluent surfacing and overflow challenges for Gold Beach, Ore.

Evolving the curriculum in higher education to prepare undergraduate and graduate students to be water reclamation (modern name that encompasses wastewater treatment) design professionals and decision makers is key to managing future worldwide water and wastewater challenges effectively. A keen understanding of decentralized system approaches, devices, and technologies is critical to future professionals’ ability to recommend the most advantageous design solutions to meet individual situations and development and community needs.

During the 20th Century, U.S. higher education curriculum concerning wastewater systems engineering was predominantly focused on design and operation of wastewater collection systems and centralized treatment plants for cities and other urbanized areas. That decentralized systems education was available to a lesser extent is not surprising since the focus of federal research and educational funding was on centralized wastewater systems, and that is where careers were mostly available for university graduates.

Today, many U.S. universities offer some undergraduate and graduate curriculum addressing decentralized systems. This typically involves faculty mentoring of students involved in research or lecture delivery on water supply and wastewater treatment. In a few cases, specialty programs such as a Water and Sanitation for Health (WASH) program include lectures on decentralized water and wastewater systems. Students also receive relevant education through projects sponsored by Engineers Without Borders or other aid organizations.

Where universities have sustained decentralized system courses, they are generally offered within Agricultural and Biosystems Engineering or Civil and Environmental Engineering and cross-listed in other departments including Soil Science, Natural Resources Science, or Water Resources Management. Courses are delivered through classroom lectures complemented by laboratory or field sessions, such as those at the Colorado School of Mines, University of Wisconsin, and University of Washington. Others, including those at the University of Arizona, are delivered as online courses. All generally satisfy Accreditation Board for Engineering and Technology (ABET) criteria.

Future need

Advanced decentralized treatment unit features an ECOPOD Fixed Film Bioreactor inside an Infiltrator IM-Series Tank.

With the exploding need for wastewater treatment solutions in the U.S. and worldwide, expanding the number of universities offering decentralized systems courses is essential. This includes realizing the environmental and public health benefits of decentralized systems where little to no treatment exists and that have extremely limited resources. While it is essential that more U.S. universities offer decentralized wastewater treatment systems engineering courses, this goal is not without its challenges, including:

  • engaging a faculty member with expertise in the decentralized approach;
  • access to textbooks and course materials, including “real world” design experiences;
  • a receptive administration that recognizes the value;
  • a credit-hour space in one or more degree programs; and
  • perception of career placement opportunities in the decentralized arena.

Conclusion

The virtues and benefits of modern decentralized systems have been widely recognized, and approaches, devices, and technologies continue to be advanced and promoted for widespread use across the United States and abroad. Yet, the principles and practices of modern decentralized systems have not yet been broadly incorporated into curriculum within U.S. higher education.

Existing regulations and requirements, often based on legacy system performance, is often prescriptive, constraining, and conservative. Modernized regulations and requirements will help facilitate creative engineering to realize the full benefits of decentralized systems.

Among the thousands of U.S. universities, only a few have been successful in incorporating semester-long courses focused on engineering of decentralized systems. More sustainable funding at the national, state, and local levels is needed for course offerings, grants for research, student fellowships and traineeships, and funding for new infrastructure construction and rehabilitation of aging infrastructure. Realizing this outcome is critical to develop the next generation of engineering professionals who are informed design professionals and decision makers.


Robert L. Siegrist. Ph.D., P.E., BCEE, University Professor Emeritus and research professor, Colorado School of Mines (CSM), Department of Civil and Environmental Engineering, is former director of the Environmental Science and Engineering Division at CSM and founding director of the Small Flows Program. Before joining CSM in 1995, he held positions with the University of Wisconsin, Norwegian Institute for Georesources and Pollution Research, Ayres Associates Inc., and Oak Ridge National Laboratory. During his 40-year career he published more than 300 technical papers and three books and was awarded two patents. His new textbook, Decentralized Water Reclamation Engineering, was recently published by Springer (www.springer.com/us/book/9783319404714). He can be contacted at siegrist@mines.edu.

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