National working group focused on the integrated management of urban waters in small and medium-sized municipalities

In small and medium-sized municipalities across France and its overseas territories, urban water management and treatment are undergoing constant change, with processes becoming increasingly diverse. Set up on INRAE’s initiative, the Epnac national working group offers both practical and technical support to the sanitation sector through gathering, sharing and disseminating knowledge on the integrated management of urban waters of the concerned municipalities, in particular about their wastewater treatment processes.

The EPNAC working group

Various public-sector sanitation actors in France constituted this group in 2008 subsequent to a consensual observation. The diversity of wastewater treatment processes in small and medium-sized municipalities, as well as their rapid evolution spurred by construction firms or the public sector, were complicating the validation and dissemination of independent technical opinions on these processes. This difficulty stemmed from both a lack of experience with respect to such new processes and the presence of miscellaneous and dispersed information. The investments these infrastructures require are indeed significant for such municipalities in order to satisfy regulations (increasingly stringent requirements to reduce discharge levels). For an optimal use of public finances earmarked for sanitation, the definition and dissemination of clear design and management rules have become necessary.

The Epnac working group, launched and overseen by INRAE, combines the entire set of public-sector sanitation actors:

  • Ministry of Ecological Transition
  • French Office of Biodiversity
  • Regional Water Agencies
  • International Water Office
  • Departmental Councils responsible for providing assistance to treatment plant operators
  • Departments overseeing Water Enforcement Divisions


The national Epnac group’s goals are to acquire, share and disseminate knowledge on the integrated management of urban waters in small and medium-sized municipalities, in particular on wastewater treatment processes.

Operations: Supervision and studies

The diversity of actors involved serves to address broadly the sanitation field with respect to its technical, regulatory, scientific and economic layers. This panel of complementary individuals yields a better analysis of the problems facing municipal authorities, engineering consultants, facility operators, builders, decision-makers, etc.

A committee comprising all participating organizations supervises the group’s tasks. This steering committee plays a key decision-making role on issues related to organization as well as strategic, scientific and technical options.

This organization relies on subgroups in the areas of knowledge production and dissemination. More specifically, dedicated workshops held for several years running handle the study topics targeted by the group. Attended on a volunteer basis, such workshops assemble roughly 10 to 15 professionals around objectives pertaining to: treatment process design, scaling and operations, process valuation or general information collection specific to urban wastewater management concerns voiced by smaller municipalities.

The Epnac group’s ongoing workshops focus on the following topics:

  • Treatment plant refurbishment (facultative ponds, French vertical flow treatment wetlands, trickling filters, etc.)
  • Integrated stormwater management
  • New processes (aerated treatment wetlands, physicochemical phosphate removal, disinfection of treated wastewater, etc.)
  • Regulatory frameworks
  • Interaction with municipal agencies
  • Reuse of treated wastewaters

Dissemination of results:

Reference documents are available in open access on the Epnac group’s website ( Many of these documents originate from the output of the group’s workshops, while other documents published by partners, have also been uploaded to the site after being validated by the scientific committee.

Moreover, a Technical Workshop is organized every year for all personnel with Epnac group partner organizations. This 2-day forum provide a privileged moment for exchanging views and technical opinions, in addition to hosting debates on current topics related to sanitation; moreover, they serve as a venue for sharing the group’s recent research achievements. This event takes place annually in a different catchment basin zone and gathers around 150 people from all the country and its overseas territories.

Since 2021, Epnac also offers a one-day online session open to both private actors and public authorities, in partnership with the OiEau organization. The aim is triple: promoting professional skills in this field, providing public policy guidance, and thus better preserving precious water resources. . The topics presented are a selection of the most useful presentations of the annual Technical Workshop.


LinkedIn: EPNAC - Groupe National | LinkedIn


Modification date : 24 May 2023 | Publication date : 17 October 2022 | Redactor : RC