Establishing control points for promoting bottom-up management of domestic wastewater treatment systems in the Republic of Ireland: A national household survey and research agenda

Where correctly installed and maintained, domestic wastewater treatment systems (DWWTSs) provide effective, environmentally sustainable wastewater disposal in rural and peri-urban areas. In contrast, poorly sited and/or mismanaged systems can contaminate private drinking water sources and public watercourses, posing a serious environmental health threat. Almost 30% of households in the Republic of Ireland (ROI) rely on DWWTSs, with systems often co-occurring with (unregulated) private domestic groundwater wells or adjoning surface water body margins. Dual reliance on decentralised, private drinking water sources and wastewater disposal in vulnerable catchments places a premium on voluntary system maintenance actions (e.g. desludging). However, despite recent introduction of mandatory, targeted system inspections and ancillary public engagement, system maintenance rates in the ROI remain low. Untreated domestic wastewater discharges pollute almost 10% of low status national water bodies and jeopardise private well water quality due to locally dense rural settlement patterns and historically poor DWWTS installation. The ROI currently reports elevates incidence rates of waterborne illnesses such as Shiga-toxin producing Escherichia coli (STEC), currently almost 10 ten times the EU mean and consistently linked with well water consumption. As such, mitigation of water contamination risk posed by DWWTSs via improved behaviour promotion represents a vital policy measure.

To this end, a national online survey (hosted by SurveyMonkey) was developed to identify and measure key cross-thematic precursors to household DWWTS maintenance measures. The survey considered both actual and conjectural reactions to household DWWTS inspection in addition to behaviour change (i.e., commencement vs. cessation of system maintenance). Preliminary analysis of approximately 500 survey responses found that 71% of Irish system users reported previous system desludging. However, of serviced systems reported to exceed 5 years in age (i.e. warranting ≥ 1 historical desludging events), 20.2% were infrequently desludged. Reported adoption and historical continuity of general system maintenance  were both significantly associated with occupancy during system installation (p <0.001, respectively) and self-perceived confidence regarding system management (p <0.001, respectively). Adoption of system maintenance after previous inaction was significantly more likely where prior system issues were reported (p <0.001), highlighting a priori intangibility of system malfunction/contamination risk as a likely behavioural barrier. Subsequent analysis will seek to identify opportunities for optimal intervention strategies via predictive agent-based modelling (ABM) of system maintenance behaviours. Development of weights via respondent policy preferences and cited barriers will be used to inform policy-based scenarios for behaviour promotion and their potential impact on system maintenance behaviours. Adoption of artificial intelligence to delineate optimal interventions from a ‘legislative sandbox’ represents a novel contribution to behavioural research within the socio-hydrogeological paradigm. Resultant findings may help ‘unblock’ current knowledge impediments to mitigation of domestic wastewater-induced water contamination.

Keywords: behaviour change ∙ domestic wastewater ∙ environmental policy ∙ risk management ∙ socio-hydrology ∙ water contamination