# Nitrate-Polluted Waterbodies Remediation: Global Insights into Treatments for Compliance
## 1 Introduction  
Water is essential for economic growth, human health, and the environment. In terms of quantity and quality, freshwater is a limited resource on Earth. The pollution of surface and groundwater poses a threat to aquatic ecosystems and society. The challenge of providing quality water, both for human consumption and for food production and recreational use, is undoubtedly one of the most pressing of the 21 st century. Global warming, desertification, and the contamination of surface and groundwater have drastically reduced the availability of freshwater [1], and it is a key issue in meeting the Sustainable Development Goals (SDG) included in the 2030 Agenda for Sustainable Development, adopted by all United Nations Member States [2, 3]. Nitrogen compounds in the soil may have a natural origin where they are subsequently oxidized to nitrates. Nitrate ions, driven by its extreme water solubility and resistance to fixation by soil colloids, are very susceptible to contamination by leakage. They can be easily washed into deep areas of the soil by rainfall and/or overirrigation, reaching groundwater bodies [4]. Diffuse agricultural pollution is the contamination of water, soil, and air, as a result of farming practices. This pollution depends on what happens on the Earth's surface and practically affects large areas of our planet. It is very significant in many world regions because of the cumulative effect that certain discharges can have on the environment. Agricultural practices such as seedbed preparation, ploughing, fertilization, slurry application,and crop spraying are all possible contributors to diffuse pollution [5; 6]. Thus, there is a wide range of potential sources of diffuse pollution that are linked to agricultural practices and that can damage the environment. This diffuse pollution is particularly evident in water bodies, when due to rainfalls and the way the land is managed, nutrients, pesticides, faecal bacteria, chemicals, and fine sediments are leached from the land into streams, rivers, lakes, and groundwater. European legislation, in the form of the Water Framework Directive 2000/60/EC of the European Parliament and of the Council, of 23 October 2000, highlights the issue of diffuse pollution [7]. Its main topic is integrated water management, and its primary objectives are to prevent degradation, and restore and improve surface and groundwater to reach and preserve their healthy ecological balance. Agriculture can lead to serious environmental impacts, sometimes difficult to quantify, on the surrounding waterbodies [8; 9]. Within this European framework, different proposals are put forward, such as the so-called \"from farm to fork\", aligned with the Biodiversity Strategy for 2030, included in the European Green Deal, which contribute to tackling this problem. These lines of action set, among other objectives, a 50% reduction in excess nutrients, which will entail a 20% reduction in the use of fertilizers. The targets set by the Member States with these goals must be reached by the end of 2030, within a period close to the end of 2027, set as the deadline for achieving the environmental objectives in waterbodies [10]. By reason of its inherent nature, the effective nitrate pollution control and management is not simple and demands accurate analysis and insight into a variety of anthropogenic and natural processes. One of the effects of modern agriculture is the excessive use of fertilisers and manure, which causes high levels of certain nutrients, particularly phosphorus and nitrogen, to be transferred to waterbodies through diffuse processes [11]. Overconcentration of these nutrients in water leads to harmful impacts by promoting eutrophication, resulting in the consequent loss of both animal and vegetal species.