Biosolids soil application: Agronomic and environmental implications 2014

World production of biosolids is continuously increasing due to global urbanization of society and the increase in wastewater treatment coverage [1, 2]. Nowadays, the accumulation of biosolids poses a growing environmental problem. With the recent banning of ocean disposal and new stringent landfilling regulations, much more biosolids are now beneficially reused. Agriculture use of biosolids is still considered the main feasible disposal option, being both a cost-effective practice and a way to close the nutrient loop in agriculture and remediated soils. On the other hand, due to the ever increasing transportation, disposal costs, and increasing public pressure, efforts are being made to reduce the quantity of biosolids for disposal [3]. However, the demographic dynamics and technoeconomical problems in some developing countries lead to uncontrolled use of raw sewage in land application. This is mainly due to the fact that, in several areas around the world, increasing urbanization may lead to wastewater production in the order of 4.106 L per day, of which only a minor proportion can be effectively treated. Therefore, sewage systems often flow together with industrial effluents, enriching the biosolids with heavy metals, organic xenobiotics, endocrine disruptors, and hormones [4]. Land disposal of such material may cause detrimental effects on soil quality, crop production, and animal or human health. In many countries, water shortages result in the use of treated municipal wastewater for agriculture irrigation. Moreover, this practice is considered a valuable source for recycling and reuse of nutrients and water [5]. However, the use of sewage effluents for irrigation may cause soil pollution by the accumulation of hazardous elements [6]. Consequently, there is a considerable interest in the effects of this practice on the quality of crops intended for human consumption.