## 1 Introduction  
Pesticides, herbicides, fertilizers, plant growth regulators, and other agrochemicals play a decisive role in agriculture, protecting crops and improving yields, but the current main challenge is the development of profit-gaining agriculture increasingly geared to environmentally friendly management systems, aimed at reducing the damages produced by agrochemicals to humans and the environment [1]. High intensity agricultural models are characterized by a massive use of pesticides and herbicides contaminating water and soil [2, 3, 4]. In 2018, the worldwide quantities of applied pesticides corresponded to 4112.3 metric tons, and in Italy alone to 54.1 metric tons [5]. Animal waste from farms, sediments, organic debris, pesticides, and fertilizers have long proven to be the major causes of ground and surface water pollution [6, 7]. Soil and water bodies risk contamination every time pesticides are manipulated [8]. Pesticide drift, percolation, drainage, runoff, and leaching greatly depend on their cor rect management, both before and after the treatment, including the correct use of the application equipment, i.e., the pneumatic sprayers [9; 10; 11]. A known source of point source pollution is represented by incorrect practices in the disposal of spray remnants and tank rinsing water. Directive 2009/128/EC [12] regulates the disposal of agro-wastewater containing pesticides; however, it is quite common for, after the application, the spray remnants in the barrel of the spray-tank to be deposited on the ground or even discarded directly into water bodies, often without any dilution. These point sources of pollution from leftover mixture and cleaning water disposal are a matter of concern since pesticide residues may persist for a very long time; some compounds can be still detected many years after their ban [13; 14]. Several solutions have been studied and proposed to remove or inactivate pesticides in water. Most are plants based on water evaporation produced by solar radiation and wind (Heliosec(r), Syngenta Agro sas, Guyancourt, France) or by infrared radiation and heat (Osmofilm(r), Panteck- France sarl, Montesson France) [15]. Quicker evaporation can be obtained by using electrical resistance, filtering the vapors through activated carbon filters (Evapofit(r), Staphytr, Inchy-en-Artois, France) [15]. Otherwise, a chemical pretreatment of coagulation-floculation can be used to produce decantation of the active ingredient as solid material (Sentinel(r), Alba environment as, Cluny, France) [15]. Various systems are based on biomass beds, based on microbial degradation (using fungi, bacteria, actinomycetes, and viruses) into less toxic forms [1; 9; 16]. However, all these solutions require a place and/or a plant where they can be carried out. More effective treatment systems are required, and the most recent and effective water treatment technologies are based on advanced oxidation processes (AOPs), a set of innovative techniques including UV-based techniques, ultrasound, electron beams, \(\gamma\) rays, and plasma methods, which remove organic contaminants by mineralization [17]. The UV treatments are the easier and less expensive ones, optimized by the addition of a photocatalyst or a radical mediator, such as H\({}_{2}\)O\({}_{2}\), which promotes the radical-mediated degradation of the molecules [18; 19; 20], according to the main steps illustrated in Scheme 1. Exactly like other organic pollutants, agrochemicals can be degraded by light irradiation, especially by UV light. A huge number of studies on the photochemistry of these pollutants have been carried out, determining the photodegradation kinetics, the degradation pathways, and the optimal conditions such as the addition of oxidants and/or catalysts able to enhance the process for the most recalcitrant compounds [21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31].