Effective removal of phosphorous from dairy wastewater by struvite precipitation: process optimization using response surface methodology and chemical equilibrium modeling

ABSTRACT

This study investigated precipitation of struvite from dairy wastewater. The results indicated that pH of the solution exhibited a significant effect on phosphate recovery and purity of struvite. Results showed that 95% of phosphate was recovered from solution at MgO:P molar ratio of 4:1 and pH 9.5. Furthermore, struvite precipitation was optimized using response surface methodology; Visual MINTEQ was used to identify the speciation and precipitation potential of solid phases at different pH. Economic evaluation study revealed that recovery of struvite from phosphorous rich wastewater considerably reduces the chemicals requirement and associated sludge transportation and disposal.

Graphical abstract

KEYWORDS:

• Dairy wastewater
• phosphate recovery
• struvite
• response surface methodology
• visual MINTEQ

Novelty of this research article

The main objective of this paper is to recover struvite from dairy wastewater and optimize the process parameters using RSM and chemical equilibrium. Even through many researchers were worked on struvite precipitation, very few studies only reported the recovery from dairy wastewater. In this study, chemical equilibrium model was used to test the purity of the synthesis, which is novel in this study.

In this study, different possible species that are existing in aqueous phase as well as in solid phase were reported, and also the variation of species concentration with pH was described. The economic estimation of the present study was also investigated, which reveals that the sludge disposal problem can be reduced to greater extent. Almost $30,000–$40,000 can be saved per year by using the present study.