Towards a methodology for recovering K‐struvite from manure

Abstract

BACKGROUND This study provides a methodology for recovering two essential macronutrients (potassium and phosphorus) from the liquid fraction of manure. This methodology paves the way for K‐struvite recovery from manure by determining the suitable operational conditions (pH and temperature). RESULTS The theoretical operational conditions were established by modelling and experimentally adjusted with manure, achieving the highest recoveries (80% of P‐recovery) at pH 10 and 38 °C when using a 10% manure solution. Then, the suitable operational conditions were evaluated using 0–10–50–100% manure solutions. The lowest percentages of manure (0–10%) favoured the co‐precipitation of other products besides K‐struvite (magnesium phosphate and magnesium hydroxide); and at the highest percentages of manure (50–100%), all the phosphate was recovered as K‐struvite, but also the co‐precipitation of magnesium hydroxide due to the Mg/P molar ratio applied (Mg/P = 2). Suspended particles acted as nuclei for heterogeneous nucleation and favoured the aggregation of crystals resulting in a star‐asterisk form. CONCLUSION The viability of the process was demonstrated, this study being the first proof‐of‐concept of K‐struvite recovery from complex waste streams. © 2017 Society of Chemical Industry

Effect of suspended solids and its role on struvite formation from digested manure

“…The first, is reported to be stable at high concentrations of magnesium and at low pH values, and the second at low ammonium concentrations . In this study, struvite was recovered from manure at pH 8.5, which did not enhance the formation of newberyite, as its precipitation would occurs at pHs below neutral, nor the formation of K‐struvite, as it occurs at low concentrations of ammonium when the reactivity of K‐struvite formation surpasses that of struvite and at higher pHs …”

“…11 In this study, struvite was recovered from manure at pH 8.5, which did not enhance the formation of newberyite, as its precipitation would occurs at pHs below neutral, 25 nor the formation of K-struvite, as it occurs at low concentrations of ammonium when the reactivity of K-struvite formation surpasses that of struvite 11 and at higher pHs. [26][27][28] The role of solids on struvite formation The effect of solids on struvite crystallization was evaluated in the tests carried out with diluted digestate (M1-M3), and compared with the test performed with synthetically prepared digestate solution, used as a control (S4). The effect of solids is determined through the composition and structure of the product recovered.…”

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

“…Mg precipitates Ca precipitates P precipitation after biological N treatment [73][74][75][76] P precipitation together with biological N treatment [70][71][72] P precipitation before biological N treatment [66][67][68][69] Precipitated-P fertilisation testing [63][64][65] Demonstration & full-scale P recovery experiences [9,28,[61][62] Prediction of P precipitation in waste water treatment systems [55][56][57][58][59][60] P recovery as a resource [10,13,21,[53][54] Formation of P precipitates & deposits in waste water treatment systems [22,[24][25]52] P removal as a pollutant [23,[49][50][51] Chemical properties of MeP: solubility, crystallisation [45][46][47][48] Figure 1. Trend on the number of published papers related to mineral phosphate precipitation from waste water (Source: Web of Science; Accessed: January 10th 2020).…”

“…Previous experiences reporting P precipitation after biological N oxidation or removal are summarised in Table 4 [73][74][75][76]99,124,[205][206][207][208][209][210] (an extended version of this table is provided as Supplementary Material). Biological N treatment based on nitrification involves a reduction in the buffering capacity of the liquid effluent.…”

Potassium recovery from centrate: taking advantage of autotrophic nitrogen removal for multi‐nutrient recovery

“…Thus the recovery of MPP should be applied to high nutrient streams after nitrogen removal. Previous approaches to recover MPP from waste streams include a full‐scale plant treating denitrified calf manure, and lab‐scale experiments on digested manure, synthetic urine or hydrolysed urine subjected to ammonia stripping …”