On-site wastewater guidance as a tool for improving regulatory compliance: evidence from a national policy campaign in Finland

Malfunctioning or inadequate on-site wastewater treatment systems (OWTS) are a major source of diffuse pollution in European water bodies. To improve regulatory compliance and support property owners, Finland implemented a unique guidance program from 2011 to 2019. This study evaluates the effectiveness of the on-site guidance campaigns in promoting regulatory compliance and pro-environmental behaviour and identifies factors influencing their impact. Analysis of combined survey data from advisors and property owners suggests that the guidance was associated with positive outcomes: over half of respondents reported taking action towards regulatory compliance, and two-fifths reported improvements to their OWTS. The findings indicate that the effectiveness of guidance may be strengthened by behaviour change techniques leveraging social norms (e.g. communicating information about others’ compliance) and by combining normative messaging with place-based framing that highlights shared environmental consequences in locally relevant contexts. To promote broader compliance, guidance efforts should be complemented by regulatory supervision measures.