Assessment of enhanced biological phosphorus removal process inhibition

Abstract

Wastewater in industrial regions frequently contains substances which are potentially inhibitory to activated sludge treatment processes. Enhanced biological phosphorus removal (EBPR) is vulnerable to process inhibition mostly because of the location at the beginning of the treatment process and complex characteristics of influent. Much knowledge has been developed on the EBPR process; nonetheless, methods used for estimation of the process inhibition vary largely. There is no easily applicable and reliable method available for rapid determination of inhibition of the EBPR process. In this study, a method for evaluation of inhibition on the EBPR process was developed and controlled. In contrast with previous research, a fresh non-acclimated inoculum was used to enhance the possibility to predict the impact for wastewater treatment plant. The efficiency of the process was evaluated based on the values of orthophosphate release and uptake, synthesis and consumption of polyhydroxyalkanoates. 3,5-dichlorophenol (3,5-DCP) was used as a model inhibitory compound. It was found that the EBPR inhibition tests using a non-acclimated sludge need wastewater as the organic carbon source. Furthermore, the length of aerobic period substantially influenced the inhibition test results—achieved maximum inhibitory concentration (IC50) values were 2.4 times higher when aerobic phase was 6 h instead of 1.5 h. Consequently, extended aeration period was suggested to diminish the inhibition effect. Finally, the impact of the 3,5-DCP on different activated sludge treatment process using respective standard methods was tested and compared. It was found that EBPR process was similarly to the nitrification a sensitive activated sludge process.