BACKGROUNDBioaugmentation and biostimulation were investigated for their ability to improve the removal of thiocyanate (SCN-), polycyclic aromatic hydrocarbons (PAHs), phenol and trace metals in coke wastewater. Additionally, the ability of the microorganisms supplemented with the bioaugmentation product to survive in a simulated river water discharge was evaluated. RESULTSA commercially available bioaugmentation product composed mainly of Bacillus sp. was mixed with activated sludge biomass. A dose of 0.5gL(-1) increased the removal of sigma 6PAHs (sum of fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and benzo[g,h,i]perylene) by 51% and reduced SCN- below 4mgL(-1) enabling compliance with the EU Industrial Emissions Directive (IED). Biostimulation (supplementing micronutrients and alkalinity) allowed compliance for both SCN- and phenol (<0.5mgL(-1)). Bacillus sp. accounted for 4.4% of the microbial population after 25h (1.5gL(-1) dose) which declined to 0.06% after exposure to river water (24h). Exposure of the activated sludge biomass to river water resulted in a 98.6% decline in viable cell counts. CONCLUSIONIn order to comply with the IED, bioaugmentation and biostimulation are recommended for the treatment of coke wastewater to enable an effluent sigma 6PAHs of 6.6 mu gL(-1), 0.3mgL(-1) phenol and 1.2mgL(-1) SCN-. Such techniques are not anticipated to impact on downstream river water quality. (c) 2018 Society of Chemical Industry