## 3 Results
### EB Application Case Studies  
Significant examples of EB irradiation include, so far, a full-scale treatment facility for textile wastewater in South Korea treating a flow of 10,000 m\({}^{3}\)/day. The facility consists of a high-power electron accelerator (1 MeV, 400 kW) operated since 2005 at irradiation doses of 1-2 kGy added to the existing industrial biological treatment plant to achieve partial organic compound degradation. This allows to obtain a more readily biodegradable wastewater, without the use of chemical additives, by radiolytic transformation of refractory compounds into easily biodiestible forms. Irradiation before biological treatment resulted in a dramatic reduction of chemical reagent and biological process time requirements, with up to 40% increased efficiency of COD and BOD\({}_{5}\) removal, compared to the original (EB-less) plant configuration [30]. Required purification levels, that were earlier obtained without irradiation after 17 h of biological processes, with the aid of chemicals additives, were then achieved after just 8 h of combined irradiation and biological treatment.  
Application of low irradiation doses (2-3 kGy) proved to decompose the entire spectrum of alkylphenolic molecules (potential estrogens) simultaneously removing surfactants (ionic and non-ionic) in urban sewage treatment plant effluents [31].  
In agreement with reported evidence, it was postulated that water EB radiolysis could be an alternative to other AOPs [15]. Elimination of diclofenac (DCF) from WWTP effluent by irradiation at 1.5 kGy/h was studied [32]. At 1-kGy dose, about 50% of chemical oxygen demand (COD) was already removed, and complete degradation of DCF and of its first-step by-products was achieved. However, as DCF is a medium-toxic compound, solution toxicity remained basically unchanged. Increasing absorbed dose, further toxicity decrease could be observed, while complete mineralization required irradiation doses up to 5-10 Gy.  
While the high efficiency of energy conversion and radical generation of EB makes it a possible standalone process, it was shown that addition of between 3-12% concentrations of H\({}_{2}\)O\({}_{2}\) to the treated solutions could increase degradation rates by promoting enhanced generation of -OH radicals [33]. An efficiency improvement of about 10% was achieved with 3% peroxide addition, but after that the level decreased significantly. In fact, when the peroxide dosage exceeds its optimal value, it reacts with hydroxyl radicals, to generate the weaker radical HO\({}_{2}\), resulting in an overall decrease of efficiency. The presence of CH\({}_{3}\)OH and thiourea also reduced significantly DCF degradation, as the former acts as a -OH scavenger and the latter as scavenger of -H, and \(\mathrm{e_{aq}}^{-}\), since DCF degradation may occur both by oxidation and reduction.  
Radiolytic decomposition of CBZ and DCF in river and hospital waters spiked with those compounds, with simultaneous monitoring of toxicity changes, showed that at initial DCF concentration of 50 mg/L, its decomposition in aerated solution required a 4.0 kGy dose. Saturating the solution with N\({}_{2}\)O, which substantially increases hydroxyl-radical production, the required dose dropped to 1 kGy. Irradiation of hospital effluent spiked with 10 ug/L each of DCF and CBZ, with absorbed doses up to 0.5 kGy showed complete decomposition of DCF at 0.25 kGy, while decomposition of carbamazepine required much larger doses than in river water samples. A 100-Gy dose allowed 90% CBZ decomposition in the latter, but only by 37% in hospital effluents. For DCF, complete decomposition in river waters was obtained at 100-Gy, while in hospital effluents 250 Gy were needed [34].