Advances in treatment of coking wastewater – a state of art review

Abstract

Coking wastewater poses a serious threat to the environment due to the presence of a wide spectrum of refractory substances such as phenolic compounds, polycyclic aromatic hydrocarbons and heterocyclic nitrogenous compounds. These toxic substances are difficult to treat using conventional treatment methods alone. In recent years much attention has been given to the effective treatment of coking wastewater. Thus, this review seeks to provide a brief overview of recent developments that have taken place in the treatment of coking wastewater. In addition, this article addresses the complexity and the problems associated with treatment followed by a discussion on biological methods with special focus on bioaugmentation. As coking wastewater is refractory in nature, some of the studies have been related to improving the biodegradability of wastewater. The final section focuses on the integrated treatment methods that have emerged as the best solution for tackling the highly unmanageable coking wastewater. Attention has also been given to emerging microwave technology which has tremendous potential for treatment of coking wastewater.

An Overview of Coking Wastewater Characteristics and Treatment Technologies

“…2,3 Since the majority of those compounds is toxic, carcinogenic, teratogenic, and mutagenic, coking wastewater is considered one of the most toxic industrial effluents, which causes acute toxicity accompanied with genotoxicity if discharged into natural water bodies without adequate treatment. 2,21 Coking wastewater composition most certainly depends on the nature/quality of the coal and coke production process (technology level and people proficiency). 6,[22][23][24] Therefore, concentrations of pollutants in coking wastewater vary significantly from different coking plants.…”

“…6,[22][23][24] Therefore, concentrations of pollutants in coking wastewater vary significantly from different coking plants. 9 Table 1 shows physicochemical and ecotoxi- 21 This is elaborated in more detail further herein.…”

Treatment of Coking Wastewater by α-MnO2/Peroxymonosulfate Process via Direct Electron Transfer Mechanism

“…However, disposed by biochemical technologies, coking wastewater may not meet the discharge standard due to its low biodegradability: non-biodegradable constituents account for over 40% of total organic compounds, and also large amounts of refractory organics [5,13]. In addition, disadvantages including low efficiency, unstable operation and potential second pollutions have impeded the practical applications of other traditional technologies such as physicochemical ones [14,15]. In the last decade, Advanced Oxidation Processes (AOPs) have emerged as one of the most promising technologies for the elimination of organic contaminants in coking wastewater [16,17].…”

“…Inorganic pollutants including sulfate, chlorides, cyanides and nitrides are widely dispersed in coking wastewater [11]. In addition, coking wastewater is characterized by its high alkalinity and hardness [14]. In all homogeneous AOPs and even some heterogeneous ones, the elimination efficiencies of contaminants varied extensively with changeable water matrix parameters such as reaction pHs, natural organic matter (NOM) and anions [21,22].…”

“…Inspired by the advantage of quickly analyzing the interactions between multiple parameters, optimizing and predicting the experimental parameters with a low number of experiments, the response surface method (RSM) was employed to optimize the reaction conditions of the α-MnO 2 /PMS process [11,13]. Due to the fact that phenols were reported to account for more than 80% of the total COD in coking wastewater [14], we chose phenol as the model compound to uncover the mechanism of our system to degrade organic contaminants. By the aforementioned efforts, we aim to propose a strategy to treat coking wastewater via a non-radical mechanism by the α-MnO 2 /PMS process and evaluate its potential practical applications.…”