The relative risk assessment responds to a Congressional mandate to conduct a relative risk assessment of deep well injection, ocean disposal, surface discharge, and aquifer recharge of treated effluent in South Florida. Several factors important for determining risk were considered, including: what level of treatment and disinfection is provided; what stressors remain (after treatment) that may be a concern, both to human health and to ecological health; and what exposure pathways are (or may be) of significance, both to human health and ecological health. Option-specific risk assessments were then compared to determine: what is the overall estimate of risk, both to human health and ecological health and what are the important data or knowledge gaps.