Evaluation of Effectiveness of On-site Wastewater Treatment Systems Located at Roadside Rest Areas: Recognition and Diagnosis of Existing Problems in the Operation of Selected Facilities

The effects of a dynamic increase in the total length of expressways in Poland include the issue of wastewater generation and disposal at roadside rest areas, which has been gaining importance, especially regarding the safety of local water ecosystems. Currently, the total number of roadside rest areas in Poland is nearly 400, yet in the future it could double, because of road infrastructure expansion and the need to improve road travel comfort. The most common approaches to wastewater disposal are septic tanks or wastewater treatment plants. In view of Poland’s environmental goals, only the second solution can be regarded as a form of final wastewater disposal. The aim of this study was to analyse available solutions for wastewater treatment at roadside rest areas, analysis of the effectiveness of their performance and identification, and diagnosis of existing problems. The tested facilities contained solutions based on biological wastewater treatment, preceded by a mechanical stage with the use of a two-chamber primary settling tank. Two solutions involved a sequencing batch reactor, and the remaining ones used submerged fixed-bed bioreactors. Finally, the obtained results showed unsatisfactory wastewater treatment effectiveness. Parameters such as chemical oxygen demand (COD) were exceeded at five of the six study sites, biochemical oxygen demand (BOD5) was exceeded at three sites, and total suspended solids was exceeded at two sites, which indicates a disturbance in the operation of the treatment plant. The reason for the poor effluent was primarily inadequate technological supervision of the operation of these facilities.