Abstract
Global deposits of concentrated phosphates, which are a necessary source for the production of phosphate fertilizers, are limited. These reserves keep getting thinner, and every day, large amounts of phosphorus end up in watercourses. In this study, we verified that modified biochar (saturated with FeCl3 solution and then neutralized with NaOH solution) can adsorb significant amounts of phosphorus from wastewater. Moreover, the agrochemical qualities of sludge water from a municipal wastewater treatment plant, struvite, phosphorus-saturated biochar, and iron(III) phosphate from a reused biochar filter were tested in this study. We determined the amount of mobile phosphorus as well as the amount of extractable phosphorus and its five fractions. It was found that modified biochar can hold one-third of the phosphorus amount contained in the commonly used agricultural fertilizer simple superphosphate (1 × 105 g of modified biochar captures up to 2.79 × 103 g of P). Moreover, plants can more easily access phosphorus biochar fractions than struvite, which is formed spontaneously during sludge management. The results of this research prove that the proposed method of recycling phosphorus from wastewater can be applied in technological practice.
Highlights
Phosphorus (P) is the 11th most abundant element in the Earth’s surface and is, not considered to be geochemically rare [1]
Water was taken in September 2018 from the central wastewater treatment plant in Prague (Bubeneč, part of the city) after it passed through a sedimentation tank
Four products were obtained from sludge management, which can be used as phosphorus fertilizers, and were analyzed
Summary
Phosphorus (P) is the 11th most abundant element in the Earth’s surface Phosphorus is limited either because it is present in insufficient amounts in soils or in forms that are inaccessible to plants These factors subsequently lead to a decrease in agricultural production [18]. PO4 3− is removed from sludge water by porous P-selective media, exchanging with cations such as Cl− to produce P-depleted effluent while maintaining charge neutrality in the solid media [36] The sorbents used are fly ash, Fe oxides, blast furnace slag, and bauxite extraction wastes These technologies are suitable when there are higher concentrations of P in sludge water and the plant-accessibility of P in the product is low [37]. The aim is to purify wastewater by removing phosphorus and, reduce the amount that enters the environment as well as obtain a high-quality phosphorus fertilizer with high added value
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