Lettuce Response to Enhanced Struvite Recovered from Faecal Sludge Effluent and the Probabilistic Health Risk Assessment of Heavy Metals Through the Intake of the Lettuce.

Abstract

Precipitating magnesium ammonium phosphate (MAP) to include potassium (K) has been explored to improve the fertilizing ability of the product. The present study aims to precipitate a MAP that also contains K and determine the probable risk to human health through the daily consumption of lettuce cultivated with the enhanced struvite. Analysis of the precipitate revealed that adding cocoa bean husk as seed produced MAP with potassium (K) content. The concentration of the heavy metals in the fresh leaves (concentration range, safe limits in mg/kg) was Cu (6.14 – 12.13, 73.3), Cd (0.11 – 0.43, 0.2), Ni (0.44 – 0.85, 67.9), Pb (0.85 – 1.38, 0.3). The estimated daily intake of heavy metals via the consumption of lettuce grown with struvite was below the tolerable upper dietary intake levels. The 95th percentile of the hazard index for the control, NPK and struvite are 0.047, 0.605, (0.214 – 0.759) respectively. The struvite produced can significantly improve its performance as an alternate phosphorus fertilizer and also show if struvite is safe for use as a fertilizer.