STRUVITE

Nutrient removal and value added product formation from wastes via struvite precipitation

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 Obiettivo del progetto (Objective)

'The major goal of the proposed research is the investigation of the applicability of struvite precipitation technique (SPT) separately or coupled with in an anaerobic digester for recovering nutrients from the anaerobic digestion process (ADP) residues. Optimising SPT will not only improve the performance of ADP which is the most commonly used process for disposing many agro-industrial wastes, in terms of reduced the nutrient (nitrogen and phosphorus) loads discharged to natural aquatic environments, but also lead production of a value-added product in the form of struvite fertilizer. Nutrient recovery from sewage sludge and other organic solid wastes in the form struvite has become the focus of many research studies because of limited phosphorus (P) rock reserves, which are mainly exploited for the production of fertilizers, in the world. There are many additional benefits of recovering nutrients during the anaerobic digestion of the organics by fixing N and P as follows; • controlling struvite formation within the digester may prevent the undesired accumulation of struvite, which causes problems in the hydraulic works, • enrichment of the anaerobic sludge produced in huge amounts in terms of N and P and improvement of its fertilizer quality, • avoiding the nutrient removal requirement of the effluent from anaerobic digesters, which contains usually higher concentrations of N and P than discharge limits, • making the digestion process more self sustainable in terms of avoiding different pretreatment techniques for N and P, • more widespread use of anaerobic biotechnology due to better performance in terms of nitrogen and phosphorus, • reduced oxygen demand in the receiving water bodies, • reduced eutrophication risks in the lakes, etc.'

Introduzione (Teaser)

Researchers have investigated whether valuable elements can be recovered from anaerobic digestion of waste from farms and factories.

Descrizione progetto (Article)

Struvite is a crystal that can form naturally as part of industrial recovery processes such as anaerobic digestion. The crystal represents an appealing way to recover phosphorus, magnesium and nitrogen from these waste streams.

The EU-funded 'Nutrient removal and value added product formation from wastes via struvite precipitation' (STRUVITE) project aimed to investigate whether the struvite precipitation technique could be applied to anaerobic digestion of agricultural and industrial waste.

STRUVITE found that mixtures of poultry waste and sewage sludge decreased the effectiveness of struvite formation. An excess of magnesium also decreased the precipitation of the crystal.

Researchers found that using an acid to dissolve the phosphorus resulted in improved struvite formation. This was particularly effective for recovering phosphorus if magnesium was added in an appropriate concentration.

The project team concluded that using both liquid and solid effluent was the best approach for struvite precipitation from an anaerobic digester. This technology has the potential to render a major source of struvite-based fertiliser and at the same time provide sustainable mineral recovery from waste streams.