Methods for quantification of biosorption in high-rate activated sludge systems

The fundamental mechanism behind biosorption to recover carbon from wastewater through high rate activated sludge (HRAS) system is insufficiently studied. The most accepted method of quantifying biosorption capacity of activated sludge depends on higher settling velocity solids. As HRAS had different settling characteristics and in addition, raw wastewater fed to the HRAS system contained approximately 55% settleable organics, the conventional biosorption capacity test was not capable of accurately defining biosorption. Thus, we studied ex-situ aerobic yield as an alternative approach for determination of biosorption in batch systems. However this approach similarly to biosorption capacity was not sensitive enough to quantify differences between HRAS types, potentially due to enhanced storage mechanisms under the feast-famine approach. A viable method to determine biosorption in the batch system was based on measurement of ex-situ oxygen uptake rate (OUR) of HRAS over 40 h and the biosorption yield was considered as the area underneath the OUR curve normalized for solids concentration. In addition, in-situ based biosorption quantification was proposed in this study based on detailed measurement of carbon mass balances including contribution of extracellular polymeric substances. A clear relationship between biosorption yield and in-situ biosorption with carbon mass-balance, carbon redirection and solids retention time of HRAS systems was observed suggesting two viable methods for quantification of biosorption. (C) 2017 Elsevier B.V. All rights reserved.