A practical approach for the determination of environmental quality standards-based discharge limits: the case of Tersakan sub-basin of Yeşilırmak River in Turkey.

Abstract

The control of point source discharges to rivers has become more significant since the establishment of environmental quality standards (EQSs). Many countries, including Turkey, have set EQS values for various contaminants. One important challenge regarding these EQSs is to reconcile the effluent limits that are technically and economically achievable with the ones that are required to accomplish the EQSs. The Tersakan sub-basin of Yeşilırmak River acquires good examples of this challenge due to the industrial and agricultural discharge activities present. In this study, a new, simplistic, and less data-driven approach is developed to facilitate this compromise and implemented for all suitable discharge points within the sub-basin. The foundation of this approach is that effluent discharges may mix and become diluted within negligibly short distances from the point of discharge where exceedance of EQSs can be permissible. The approach modularly combines different analytical solutions of the advective-dispersive mass transport equation that are applicable under different mixing conditions and estimates maximum allowable discharge concentrations of contaminants. The results of the case study in the Tersakan sub-basinindicate that none of the studied discharges need load reduction to achieve EQSs. However, in various points, tridecane, nickel, bis(2-ethylhexyl) terephthalate, NH4-N, total phosphorus, and free cyanide have consumed more than 10% of their discharge quotas estimated by the mentioned approach. Therefore, for the sub-basin, these six contaminants and their corresponding two discharge points may require more attention in the future.