Coal Gasification Wastewater Pretreatment with Coagulation and N₂ Flotation Combined System

Hong-Jun Han, Qian Zhao, Chun-Yan Xu, Hai-Feng Zhuang, Peng Xuª¤

(State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China)ª¤ª¤ª¤



Abstract:

A N₂ flotation tank combined with coagulation was developed as a pretreatment equipment of biological process to remove oil and other pollutants in coal gasification wastewater (CGW). With optimal PAC dosage of 20 mg/L, the sole coagulation process achieves removal efficiencies of 29.34£¥ and 26.83£¥ for oil and COD, respectively. For the sole N₂ floatation process, the optimal N₂ flux and HRT are 20 m³/h and 20 min. Meanwhile, the oil and COD removal efficiencies are 35.41£¥ and 14.26£¥, respectively. For the combined system of coagulation and N₂ floatation, the optimal parameter values are the same as the ones of separate processes. Correspondingly, the removal efficiencies are 46.28£¥ and 31.89£¥ for oil and COD, respectively. Besides, BOD₅/COD of the effluent is improved. In contrast with conventional dissolved air floatation, the inert gas-N₂ prevents the formation of cyclopentenone, pyridine derivatives, and other heterocyclic aromatic hydrocarbons, thus improving the biodegradability of influent for the subsequent biological processes.ª¤

Key words:  N₂ flotation tank  coagulation  coal gasification wastewater  oil  biodegradabilityª¤

DOI£º10.11916/j.issn.1005-9113.2013.05.004

Clc Number:X 703.1

Fund: