Residence time distribution experiments in a hybrid anaerobic blanket reactor treating real pharmaceutical wastewater

Background: The phenomena of mixing is considered important due to its involvement in modelling and design of reactors. Methods: The residence time distribution (RTD) experiments to find out the mixing characteristics were conducted in hybrid anaerobic blanket reactor (HABR) with four different OLRs of pharmaceutical wastewater using lithium chloride as tracer by means of stimulus-response technique. The mean hydraulic retention time, dispersion and Peclet number for various OLRs in HABR were determined. Significant findings: The experimental COD removal efficiencies in HABR and the theoretical performance were found out using the axial dispersion flow model (ADFM) and plug flow model (PFM). The estimated theoretical chemical oxygen demand (COD) removal efficiencies, using the ADFM were 92.4 %, 82.0 %, 63.0 % and 41.7 % and the values respectively for PFM were 97.27 %, 93.92 %, 83.47 % and 59.34 %. The error percentage detected was less than 7 % in ADFM which exhibited better flow representation in HABR. Furthermore, the value of correlation coefficient (R2 = 0.9956) between the theoretical COD removal efficiencies and experimental values confirmed the suitability of the ADF model.