The determination of fertiliser quality of the formed struvite from a WWTP

Abstract

Struvite from nutrient-rich wastewaters has been identified as a potential substitute for commercial mineral fertilisers, with the added benefit of reducing threats to global food security by prolonging phosphate rock reserves. A fertilisation test using grass (Brachiaria brizantha Marandú) and a sand column leaching test was conducted to determine the agronomic effectiveness of struvite precipitates produced from the supernatant of dewatered sewage sludge (centrate) from a municipal Wastewater Treatment Plant (WWTP). The performance of this struvite as a fertiliser was compared with biosolids and commercial fertilisers (Urea and Triple15). The results show that the concentration of heavy metals in struvite was lower than in biosolids and below the limits of Colombia and European fertiliser regulations. Struvite increased the uptake of N and P in grass, resulting in crop yields similar to other treatments tested. Struvite use as an effective slow-release fertiliser is highly dependent on the size of crystal particles, particularly in achieving low P losses, but resulted in high N loss in the sand columns tested; N loses from struvite were higher than in the commercial fertilisers due to the struvite small particle size. Therefore, struvite represents a suitable opportunity to recover and recycle nutrients from municipal sewage sludge, facilitating the effective reuse of P and N in agriculture and uptake by plants. HIGHLIGHTS Heavy metal concentrations of the struvite from the studied centrate of a WWTP were below the threshold limits.; P uptake and apparent P recovery efficiency by the grass were significantly higher in two struvite treatments than in the commercial fertilised tested.; N and P leaching depend on particle size. Smaller crystals can produce greater N uptake by the grass but at the same time more significant N losses by leaching.;

Keywords

• biosolid
• centrate
• crop yield
• nutrients recovery
• struvite