Recovery of phosphates(V) from wastewaters of different chemical composition

Abstract

Phosphate(V) ions were recovered from wastewaters of different chemical compositions in a continuous reaction crystallization of struvite. Two real wastewaters were represented by an effluent sample from the phosphorus mineral fertilizer industry and by liquid manure derived from a cattle-breeding farm. Two other wastewaters were prepared under laboratory conditions. Impurities present in the wastewaters caused the precipitation of solid products of distinctly different quality. The mean size of struvite crystals varied from ca. 18 to ca. 40 μm. Homogeneity within their populations, quantified by the coefficient of variation CV, varied from satisfactory (CV ca. 75%) to unfavorable (CV ca. 100%), which resulted in the elongation of necessary filtration time. Calcium ions in wastewater precipitated as amorphous hydrated calcium phosphates ACP. Their content in the products varied from 33.4 up to 73.1 mass %. Also 28.32 – 32.74 mass % of P2O5, 6.35 – 14.12 mass % of MgO and 4.35 – 16.94 mass % of CaO were confirmed in the products, together with hydroxides of some metals and salts of other impurities. Based on the chemical composition of the products derived from the investigated wastewaters, their application in agriculture as valuable mineral fertilizers is recommended.

Recovery of Phosphorus from Waste Water Profiting from Biological Nitrogen Treatment: Upstream, Concomitant or Downstream Precipitation Alternatives

“…The presence of suspended particles (1-3 g L −1 ) may favour the aggregation/agglomeration of small phosphate crystals, resulting in bigger crystalline structures [134]. The presence of inorganic impurities in the waste water will also affect the quality (i.e., composition), particle size (i.e., mean, homogeneity), and separation capacity of the precipitated products [135,136].…”

Selection of chemical phosphorus removal scheme based on Analytic Hierarchy Process

“…It ultimately leads to the deterioration of environmental water quality. At present, most urban domestic sewage treatment plants use biological methods to remove nitrogen, phosphorus and organic pollutants in sewage, and some industrial wastewater with better biodegradability also uses biological methods to remove nitrogen and phosphorus [3]- [4]. Limited by the mechanism of biological phosphorus removal, in the process of industrial wastewater treatment, if a single biological method is used to treat industrial wastewater with high phosphorus concentration, it is often difficult to meet the total phosphorus treatment requirements in the relevant discharge standards.…”