HPLC-SEC chromatograms as surrogates for BOD and other organic quality indicators of septic tank effluents

Abstract

<p>HPLC-SEC with UV254, trytophane-like and tyrosine-like fluorescence detection was used to characterize onsite wastewater effluents from septic tanks. In total, 69 wastewater effluents, 15 of them greywater (GWE) and 54 blackwater effluents (BWE), were analysed for water quality indicators: BOD-7, DOC, COD, Total-N and TDP using conventional methods. The chromatograms showed well-separated three regions, referred to as chromatographic indicators (ChIs), which were tested as surrogates for the conventional indicators. The best surrogates for BOD-7 and DOC were found in region 3 of the tyrosine-like chromatograms. Data showed that Tyr-3, representing the sum of the tyrosine-like fractions from 8.25 min, could be used reliably to assess the BOD-7 and DOC of GWE and to approximate the BOD-7 of BWE. In addition, Tyr-3a, the fractions between 8.25 and 14 min, could be used to approximate the DOC of BWE. Furthermore, the strong correlation between COD and Tyr (all the tyrosine-type fractions) for GWE and between COD and UV254-3 for BWE allows reliable calculation of the COD of GWEs and its approximation of BWEs by linear regression. Total-N correlated weakly with tryptophan-like fractions. The use of ChI as surrogates for BOD-7, DOC and COD is an important finding that enables reliable and fast analysis without use of harmful chemicals.</p>