The agricultural industry uses substantial amounts of water (the highest in the world) mostly for irrigation purposes. Rapid population growth and, consequently, growing demand for food have increased the use of pesticide to have higher yield for crops and other agricultural products. Wastewater generated as a result of excessive use of pesticides/herbicides in agricultural industry is becoming a global issue specifically in developing countries. Over 4,000,000 tons of pesticides are currently used in the world annually and high concentrations above their threshold limits have been detected in water bodies worldwide. The generated wastewater (contaminated with pesticides) has negative impacts on human health, the ecosystem, and the aquatic environment. Recently, biodegradable and biocompatible (including plant-based) pesticides have been introduced as green and safe products to reduce/eliminate the negative impacts of synthetic pesticides. Despite positive advantages of biopesticides, their use is limited due to cost and slow interaction with pests compared to chemical pesticides. Pesticides may also react with water and constituents of soil resulting in formation of intermediates having different physical and chemical properties. Diffusion, dispersion, and permeation are main mechanisms for transfer of pesticides in soil and water. Pesticides may degrade naturally in nature; however, the time requirement can be very long. Many mathematical models have been developed to simulate and estimate the final fate of pesticides in water resources. Development of new technologies and environmentally friendly pesticides to reduce water contamination is becoming increasingly important.

Photocatalysis application in water treatment has been the object of many researchers worldwide in recent decades. However, there are limited commercial applications due to low photon transfer efficiency, which create barriers leading to challenges in making the process efficient and economically feasible. Fixed UV/visible light sources, which are generally located outside the reactor or encapsulated in quartz tube inside the reactor are the source of energy to activate photocatalyst generating powerful oxidants such as electrons and holes. Suspended waterproof LED visible lights were employed to enhance photon transfer efficiency. Consequently, the required energy was lower resulting in negligible temperature increase and eliminated the need for an external cooler, no need for quartz (UV transparent) or treated glass reactors, enhanced mixing due to continuous movement of light bulbs by convective currents, and minimum/no attenuation. Direct Blue 15 (DB15) dye was used as model compound and the photocatalyst was P25 TiO2 (Average particle: 30 nm, Surface area: 50 m2 g−1). The samples taken at different time intervals were analyzed by UV-Vis. spectrophotometer (UV-3600), and TOC-V CPN total organic carbon analyzer (both from Shimadzu). It was found that for the same level of degradation, the degradation rate increased by about 50% compared to conventional fixed light photoreactor. Overall, the cost of the operation can be reduced substantially, paving the road for feasible commercialization of the process.