Wastewater treatment from pharmaceuticals: a review

Abstract

A critical analysis of literature data on wastewater treatment from pharmaceuticals was carried out. It was shown that many different methods have been proposed for the treatment of wastewaters containing drugs, pharmaceuticals and veterinary medicines; all these methods can be classified as destructive and non-destructive ones. The traditional methods of wastewater treatment include the following: biological treatment, filtration and coagulation/flocculation/sedimentation processes, they being the most common in sewage purification. Some up-to-date and advanced methods (advanced oxidation processes, electrochemical treatment, etc.) are also known. The used methods of wastewater treatment from pharmaceuticals can be conventionally divided into several following groups: (i) chemical treatment with the addition of hydrogen peroxide and/or other oxidants, such as ozone and sodium hypochlorite, together with catalysts to the system; (ii) photocatalytic methods; and (iii) electrocatalytic methods. It was noted that peroxene-based systems are especially promising for practical application; they imply the use of hydroxyl radical as an effective oxidant that is formed from the primary oxidant by its catalytic decomposition. The so-called conditionally reagent-free methods are considered as an alternative to chemical treatment methods, they include electrocatalytic and photochemical techniques, where oxygen-containing radicals (i.e. oxidizing agents) are formed under the action of electric current or UV radiation on the proper catalysts. An additional advantage of electrochemical methods is the possibility of direct electrochemical destruction of organic substances. The main disadvantages of such methods as well as other heterogeneous catalytic systems are relatively high sensitivity to the composition of a catalyst and too low process rate due to decelerated delivery of pollutants to the interfacial boundary where the reaction occurs.