Holistically Managing Pathogens and Nutrients in Urbanizing Tropical Towns: Can Sanitation Technologies Create Safer Conditions for Beach Recreation?

Rapidly
urbanizing coastal communities are prone to overpopulation
and unrestrained growth that result in pathogen and nutrient emissions,
which impair beach water quality and jeopardize human and environmental
health. Decision makers face
complex, context-dependent choices when selecting sanitation technologies
with varying abilities to remove pathogens and nutrients. The goal
of this study was to identify context-appropriate sanitation solutions
that manage pathogens and nutrients to ensure safe beach swimming
conditions in an urbanizing coastal town that relies on tourism. Quantitative
microbial risk assessment was utilized to determine the pathogen log10 reduction values (LRVs) required for safe swimming. A lack
of consensus in the literature about an aggregation parameter in the
norovirus dose–response model resulted in predicted LRVs that
differed by as much as 3 orders of magnitude. Local experts identified
nine context-appropriate infrastructure scenarios, and their ability
to reduce pathogen and nutrient loadings was modeled. The model showed
that spatially targeted sanitation infrastructure scenarios could
effectively meet LRV targets. Seasonal increases in population were
predicted to greatly impact pathogen and nutrient loadings. Top-performing
scenarios that managed both pathogens and nutrients included centralized
treatment with disinfection and integrated resource recovery. Future
research is needed to understand the scenarios’ sociocultural
feasibility and costs.