Brief review of the history and characteristics of the acid tar-contaminated site Predajná I and the potential application of electrochemical oxidation for the remediation of surface waters from uncapped lagoon

Historical disposal of acid tars from Petrochema refinery operations has resulted in persistent environmental hazards arising from the open acid-tar lagoons. These lagoons accumulate strongly acidic, highly contaminated waters enriched with organic compounds and heavy metals, posing significant risks of overflow and contamination of surrounding soils and groundwater. To mitigate these risks, electrochemical advanced oxidation using boron-doped diamond electrodes (BDD) was investigated as a treatment method for the contaminated surface water. Laboratory experiments demonstrated progressive degradation of organic pollutants, with chemical oxidation demand (COD) and total organic carbon (TOC) reductions of up to 94 % after four hours. Sulfonated compounds were oxidatively cleaved, releasing sulfate ions, while oxalate formed as a transient intermediate before complete conversion to CO2 and water. Instantaneous current efficiencies reached ~90 % and specific energy consumption 25 kWh per kg of COD removed in the initial current-limited stage, decreasing at higher currents due to mass transport limitations and side reactions. These results highlight the potential of electrochemical oxidation to achieve near-complete mineralization of persistent organics, and provide a sustainable solution for the remediation of acid-tar-contaminated waters at legacy industrial sites.