Selection and evaluation of a septage management concept for islands: The case study of Brač Island

This paper analyses the problem of septage mining on islands in accordance with the circular economy (CE) concept. Islands are natural and socioeconomic systems wherein seasonal tourism and agriculture are the major economic activities, while environmental and health security are the top priorities. The majority of the individual housing facilities on islands are not connected to a public sewage system, thereby rendering the treatment and disposal of septage difficult. A significant degree of seasonal variability is observed in the quantities and characteristics of the septage produced, which hinders the sustainability of potential solutions. Consequently, there is a need to elucidate the benchmarks of a sustainable solution and quantify the CE implementation. This problem was solved using a simple two-step process. First, a concept for septage management was selected based on a waste hierarchy approach. Second, a sustainability policy was quantified by evaluating a composite indicator that accounts for economic, environmental, and social issues. The application of the sustainability index enables the assessment of the cumulative impact of the proposed solution on the environment of the island. The applied methodology has proven to be useful in the creation of a sustainable management concept that minimises negative impacts and protects resources. The proposed septate mining concept can strengthen the self-sustainability of islands and alleviate the threat to their business and environment.