Application of Biological and Adsorption Treatment Techniques for the Degradation of Phenol and COD from Coke Oven Wastewater

Abstract

Over the last decade, rapid industrialization has contaminated water resources; iron and steel plants are among the most polluting industries. A million litres of wastewater are produced daily during the coal carbonization and quenching of hot coke, which contains a significant concentration of suspended solids, oil & grease that are high in chemical oxygen demand (COD), biochemical oxygen demand (BOD), phenols, ammonia, cyanide, and other toxic substances. These are disposed into water bodies without proper treatment, resulting in contamination of aquatic ecosystems. The present study focused on investigating the efficiency of using biological treatments and adsorption as a method for removing phenol and COD from real coke oven wastewater. The aim is to explore the potential of using biological treatments methods and natural adsorbents, such as agricultural or household residues, for effective phenol removal. Specifically, we used bench scale bioreactors and activated carbon derived from banana peel waste as the adsorbent. Initially the physico chemical properties of the coke oven wastewater samples were analysed that confirms the presence of phenol (190-200 mg/L) and COD (645mg/L) in a non-permissible level as per the IS-2490. Consequently, the study has been isolated, identified and characterized and four indigenous phenol-degrading microorganisms were identified from coke oven wastewater. The phylogenetic analysis confirms the isolated strains and identifies them as Brevibacillus borstelensis (R1), Bacillus cohnii (R2), Bacillus aerius (R3), and Bacillus haynesii (R4). Out of these four strains two of the isolates have ability for high phenol tolerant capacity up to 500 mg/L and biofilm formation ability when attached to media i.e., coconut coir fibre. By varying operating parameters of the bench scale rotating biological contactor the degradation efficiency of phenol and COD have been investigated. Response surface methodology is used for the optimization of variable parameters of RBC. Growth of microbial biofilms resulted the degradation of harmful chemical compounds like phenol and COD in coke oven wastewater. The scanning electron microscope (SEM) results showed that indigenous microorganisms within coke oven wastewater have a strong affinity to form biofilms and degrade phenol by 96% and COD up to 67%. Also, the study investigated the phenol removal efficiency by using natural adsorbents (or biosorbent) specifically derived from the agricultural or household residues. The current research deals with the efficient removal of phenol concentration from real coke wastewater using activated carbon extracted from banana peel waste as an adsorbent. The maximum phenol removal efficiency from coke wastewater were optimized and statistically analysed by using Box Behnken design (BBD). The use of activated banana peel biosorbent resulted to achieve maximum phenol removal efficiency of 89%. A brief study of techno-economic study and cost analysis has been performed to ensure that rotating biological contactor system unit regrading treatment of industrial effluent is cost-effective.