A simple spectrophotometric method to determine phytic acid in poultry wastewater without acid digestion

ABSTRACT

Frequently, wastewater from treatment plants associated with animal husbandry, mainly animal feeding operations, are used to irrigate near agricultural lands based on nitrogen requirements. To avoid soil phosphorus accumulation owing to its long-term application, it is necessary to achieve lower levels of total phosphorus; one of the methods involve eliminating dissolved organic phosphorus (DOP) in treatment systems. The DOP in effluents and manure wastewater streams is commonly quantified without the identification of individual phosphorus species. Nevertheless, characterisation of the DOP is particularly important, because removal techniques, as well as soil sorption capacity and phosphorus transfer in the runoff to water bodies, differ for different DOP compounds. Particularly, phytic acid (PA), the main DOP compound in animal wastes, can strongly bind to soils making it unavailable for plant uptake. This work evaluates the application of a simple analytical procedure to the determination of the PA concentration in manure wastewater. The method does not require a prior acid digestion stage; in addition, sample colour removal, as well as the removal of potentially interfering compounds are not required. The results are in agreement with results obtained using ³¹P NMR. PA recoveries ranged between 87% and 97%, relative standard deviation was <8.5%, while the limits of detection and quantification for phosphorus as PA were 0.18 mg·L⁻¹ and 0.55 mg·L⁻¹ respectively.

KEYWORDS:

• Phytic acid
• wastewater
• organic phosphorus
• manure

Acknowledgments

The authors thank Johanna Duarte, Axel Dullak and Fátima Díaz for their invaluable assistance. The excellent technical support from the Nuclear Magnetic Resonance Laboratory of Chemical Faculty (UdelaR) is also appreciated.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the CONACYT through PROCIENCIA Program Fund resources for Excellence in Education and Research – FEEI from FONACIDE, Paraguay Projects [14-INV-282 and 14-INV-392]; National Researcher Incentive Program (PRONII); National Agency for Research and Innovation (ANII) [POS_NAC_2014_1_102893].