Abstract
Abstract Caustic (NaOH) solution is used to remove H 2 S from hydrocarbon streams in petroleum refining industry, gradually being, so called, spent sulfidic caustic (SSC) which has high levels of H 2 S and alkalinity. Thus, SSC can be used as an electron donor and a buffering agent for autotrophic denitrification. As SSC, however, contains some non-biodegradable organics, air stripping was conducted to remove the non-biodegradable organics. As a result, over 93 % of the non-biodegradable organics was removed within 30 min of aeration. Then, Na 2 S 2 O 3 ·5H 2 O, methanol and organic matters, which are produced from a biodiesel production plant, were added to reform the air-stripped SSC and their products being referred to new sulf idic caustics (NSCs) Ⅰ, Ⅱ and Ⅲ, respectively. Thereafter, to investigate the effect of these products on the removal of COD and TN, these products were injected to a biological nitrogen removal (BNR) process, resulting in additional 44 % TN removal without noticeable increase in the effluent COD level. Therefore, it can be said that the BNR process is a promising option to treat NSC as demonstrated in this study whose results can be useful for developing resource recovery technologies.
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