Synthesis and Characterization of Struvite using Wastewater and Hot Spring Water for Agricultural Applications

THESIS TITLE: Synthesis and Characterization of Struvite using Wastewater and Hot Spring Water for Agricultural Applications

STUDENT’S NAME: Wamechi Juma Edith Nasambu

SUPERVISOR’S NAMES:

1. Dr. Francis Maingi
2. Dr. Linda Ouma

ABSTRACT

Currently, the agricultural sector has been experiencing inorganic fertilizer shortages due to the disintegrating phosphate rock conventionally used as phosphorus source during fertilizer production. The rock disintegration has been caused by its consumption with mining. This has led to low food production amid the increasing human population. For this reason, the conventional inorganic fertilizers availed to the market are scarce and unaffordable because the conventional methods of their syntheses require large amounts of energy and resources. The present study focused on addressing this issue by synthesizing a substitute inorganic phosphate mineral, struvite (MgNH₄PO₄.6H₂O), from sewage wastewater. The cost of production of this mineral heavily relies on the cost of the magnesium source used. To address the gap of unavailability of low cost environmental friendly natural magnesium source, hot spring water was investigated as a potentially cheaper natural source of magnesium ions for struvite synthesis. Hot spring water was found to contain 546.6ppm magnesium ions (ICP-OES) and sewage wastewater contained 76.6ppm nitrogen (Micro-kjeldahl) and 237.6ppm phosphate ions (UV-Vis).The precipitate purity and phosphorous recovery were 68.61% and 76.15% respectively. XRF results showed that synthesized struvite majorly consisted of magnesium oxide and phosphorous (V) oxide with 70.94% and 14.919% respectively. XRD analysis showed the presence of orthorhombic crystalline phases between 4-9 degrees at angle 2? 15.8(002), 20.9(111), 30.6(211), 33.4(022) and 46.3(130) which matched struvite ICDD card information. SEM revealed irregular, crystalline, and rod-like morphological structures that were consistent with those identified in the literature. The synthesized composite contained a percentage purity of. On application of struvite, 0.16% of struvite (P₄) gave the best yield on maize. The study recommended the use of hot spring water and sewage wastewater from other sources in struvite precipitation. Also, the effect of non-struvite ions present in hot spring water and sewage waste water on struvite purity and yield be investigated. Finally, struvite effect on different soils be investigated to determine optimal quantities on different soils.