Removal of Pharmaceutical Residues from Water and Wastewater Using Dielectric Barrier Discharge Methods-A Review

Abstract

Persistent pharmaceutical pollutants (PPPs) have been identified as potential endocrine disruptors that mimic growth hormones when consumed at nanogram per litre to microgram per litre concentrations. Their occurrence in potable water remains a great threat to human health. Different conventional technologies developed for their removal from wastewater have failed to achieve complete mineralisation. Advanced oxidation technologies such as dielectric barrier discharges (DBDs) based on free radical mechanisms have been identified to completely decompose PPPs. Due to the existence of pharmaceuticals as mixtures in wastewater and the recalcitrance of their degradation intermediate by-products, no single advanced oxidation technology has been able to eliminate pharmaceutical xenobiotics. This review paper provides an update on the sources, occurrence, and types of pharmaceuticals in wastewater by emphasising different DBD configurations previously and currently utilised for pharmaceuticals degradation under different experimental conditions. The performance of the DBD geometries was evaluated considering various factors including treatment time, initial concentration, half-life time, degradation efficiency and the energy yield (G₅₀) required to degrade half of the pollutant concentration. The review showed that the efficacy of the DBD systems on the removal of pharmaceutical compounds depends not only on these parameters but also on the nature/type of the pollutant.

Keywords: advanced oxidation technologies; chemicals/contaminants of emerging concern (CEC); dielectric barrier discharge; excilamp; pharmaceutical residues; wastewater; water.

Figure 1

Plasma discharge and common configurations [119,120].

Figure 2

Single dielectric barrier discharge (DBD) reactor used for the decomposition of pentoxifylline and antibiotics in water [155].

Figure 3

Experimental setup of the dielectric barrier discharge (DBD) water treatment process: 1. High voltage (HV) generator, 2. Oscilloscope, 3. Quartz reactor [156].

Figure 4

Diagram of the flow-through reactor. 1—barrier electrodes; 2—catalytic counter-electrodes; 3—corona discharge; 4—stainless steel plane; 5—PTFE isolator; 6—thin water film; 7—airproof case; 8—ceramic isolator; 9—gas inlet and the two injection points; 10—exhaust; 11—frequency generator; 12—high voltage transformer; 13—sample reservoir; 14—external gear pump; 15—flow control; 16—Teflon tube [161].

Figure 5

Diagram of the rotating drum reactor. 1—rotating drum; 2—sample reservoir; 3—barrier electrodes; 4—corona discharge; 5—exhaust; 6—sample drain hose; 7—high voltage transformer; 8—frequency generator [161].

Figure 6

Single-cylinder dielectric barrier discharge reactor used for the degradation of sulfadiazine antibiotics [162].

Figure 7

Experimental set up for the degradation of antibiotics [162].

Figure 8

Reactor experimental set up utilised for the degradation of triclosan (TCS) [163].

Figure 9

Experimental diagram of the dielectric barrier discharge (DBD) reactor used for the decomposition of triclocarban (TCC) [164].

Figure 10

Planar water falling dielectric barrier discharge (DBD) reactor used for the degradation of diclofenac (DCF) and ibuprofen (IBP) pharmaceuticals [165].

Figure 11

Plasma reactor set up used for the decomposition of acetaminophen (APAP) model pollutant [166].

Figure 12

Dielectric barrier discharge (DBD) experimental system used for the decomposition of norfloxacin [167].

Figure 13

Spray dielectric barrier discharge (DBD) reactor set up used for the degradation of paracetamol [50].

Figure 14

Different reaction zones encountered in the dielectric barrier discharge (DBD) system [120].

Figure 15

Coaxial excilamp design (top) and external view during operation (bottom): 1—excilamp bulb; 2—external perforated electrode; 3—internal perforated electrode; 4—discharge gap; 5—high-frequency voltage generator.

Figure 16

Possible scenarios of events indirect photolysis.

Figure 17

Schematic drawing of set-up with dielectric barrier discharge (DBD) driven Xe₂-excilamp for UVU photolysis [200].