Enhancing water quality and sustainable organic-phosphate fertilizer production through phytoremediation of cattle farm effluent using artificial wetlands

Abstract

Eutrophication, which results from the excessive introduction of phosphorus into water bodies, poses a critical ecological challenge, although it is not the exclusive factor driving this phenomenon. The indispensability of phosphate fertilizers for global food production, coupled with the gradual depletion of natural phosphate reserves, underscores the urgency of sustainable phosphorus management. This research investigated the efficacy of two aquatic plant species, Salvinia and Pistia, for phosphate removal from cattle farm effluent while also exploring their potential use as organic fertilizers. These two species have been extensively employed in phytoremediation studies, underscoring their established roles in environmental remediation processes. Additionally, the study measured alterations in water quality parameters within an artificial wetland (AW) designed for wastewater treatment. Cattle farm effluent was collected during the cleaning and washing of the animal farm. Macrophytes were collected within a 500m diameter area of the pond using the systematic random sampling technique. The selected macrophytes were grown in identical plastic tanks filled with cattle farm effluent. Following a 21-day growth period, the harvested plants were subjected to drying at 70°C and were then ground into smaller particles to be transformed into fertilizer. The collected water samples were analyzed for residual phosphate concentrations and other water quality indicators, including pH, temperature, conductivity (EC), total dissolved solids (TDS) and dissolved oxygen percentage (DO%). Measurements of water quality indicators were replicated three times to report the average data and standard deviations. In this experimental setup, different water samples (AW I, AW II, AW III and AW IV) served as the experimental units, with corresponding dilution factors of 1:3 for AW I and AW III, and 1:2 for AW II and AW IV. The plant species involved in the study were Salvinia for AW I and AW II, and Pistia for AW III and AW IV. Statistical analysis employing Minitab 17 software enabled quantitative comparisons. Results demonstrated a consistent reduction in phosphate concentrations within the AWs over time, affirming their phosphate-removing potential. The phosphate removal efficiency of Salvinia was 37.87±6.50% and 35.69±1.32% for AW I and AW II, respectively. Similarly, for AW III and AW IV, Pistia demonstrated remarkable removal rates of 84.32±4.26% and 47.51±3.98%, respectively. Phosphate content in the fertilizers derived from Salvinia was 35.71±1.48 mg/kg and 29.44±0.91 mg/kg for AW I and AW II, respectively, while Pistia fertilizers from AW III and AW IV contained 38.00±2.29 mg/kg and 31.56±1.23 mg/kg, respectively. Furthermore, the investigation underscored the effectiveness of AWs as a potent phytoremediation technology for wastewater treatment, as evidenced by the water quality parameter analysis. This study not only highlights the promising potential of aquatic plants for sustainable phosphate management but also underscores the vital role of AWs in addressing phytoremediation potential in aquatic ecosystems.