pH Control during the Struvite Precipitation Process of Wastewaters

Diyan Radev¹, Gergana Peeva^2*, Valentin Nenov²

¹Department of Chemical Engineering, Burgas Asen Zlatarov University, Burgas, Bulgaria.
²Department of Chemical Engineering, Burgas Asen Zlatarov University, Burgas, Bulgaria.
²Department of Water Treatment, Burgas Asen Zlatarov University, Burgas, Bulgaria.

DOI: 10.4236/jwarp.2015.716113                

Abstract

The high concentration of phosphorus and nitrogen in wastewater and sludge could be lowered to a certain level by struvite (MgNH4PO4·6H2O) crystallization. One of the main factors for struvite formation is the solution pH. It can be adjusted by non-reagent carbon (CO2) dioxide stripping through the process of aeration. The intensity of the mass transfer between the air and the supernatant of dewatering sludge obtained from wastewater treatment plant is characterized by the volumetric liquid-side mass transfer coefficient, which can be estimated theoretically. It is found that the rate of pH increase depends strongly on the sparging area of the air distribution system while the air flow rate does not influence considerably the Dissolved Oxygen (DO) level which governs the CO2 stripping process. The theoretical calculated values of the volumetric mass transfer coefficient have been compared with those obtained experimentally. Based on the data obtained, relationships of pH/kLa (mass transfer coefficient) were developed. These correlations serve as a tool for prediction of pH during the struvite precipitation process.

Keywords

Wastewater Treatment, pH, Carbon Dioxide Stripping, Mass Transfer

Conflicts of Interest

The authors declare no conflicts of interest.

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