Rationale for level of impacts of oil refinery discharge

Oil refineries are often situated in coastal locations, typically on estuaries, allowing relatively easy transport links and access to water for cooling etc. during the refining process. In this case study, the discharge from a single refinery, situated on an estuary is considered. The emission routes and subsequent movement in the environment are shown in Figure 4.1.

Refinery effluents are complex mixtures of organic and non-organic chemicals, discharged directly into the environment. Much of the chemical components will be hydrocarbons, with a non-specific mode of action, causing baseline toxicity and untreated refinery effluents discharged into an estuary have the potential to impact a wide range of SPUs, across all taxonomic groups as shown in Table 4.1. Before discharge, refinery waste waters are subjected to a variety of different physical, chemical and/or biological treatment processes that significantly reduce total emissions and their potential to cause adverse environmental effects (Comber et al, 2015).  However, for the purposes of this case study, it is assumed that the refinery effluent is not treated.

Figure 4.1: Refinery discharge into estuarine environment

Table 4.1: Potential impact of an oil refinery discharge on specific ecosystem services (green: no impact; yellow: moderate impact; red: severe impact) and potentially impacted service-providing units (SPU)