EFFICIENCY OF FERRIC SULPHATE FOR REMOVAL OF PHOSPHORUS FROM MEAT PROCESSING WASTEWATER

Abstract

Meat processing wastewater is heavily contaminated with phosphorus. It can be removed from wastewater by the use of flocculants. Phosphorus removal efficiency was estimated by treating wastewater with ferric sulphate flocculant, containing 11.5 percent of the active ingredient Fe³⁺ by weight. The research was conducted with wastewater pretreated in an aeration tank. Wastewater, containing 41.0 ± 3.5 mg l^-1 of total phosphorus (TP), was dispensed into calibrated 1.0 liter containers with the following concentrations of flocculating agent: 0, 30, 75, 120, 150, 300, 450, 600, 750, 900 and 1,050 mg/l. The study showed that TP removal efficiency depends on the flocculant dose used for treatment. Increasing the flocculant dose decreases the efficiency of TP removal. One gram of Fe³⁺, given the flocculant dose of 40 gFe³⁺/m³, removed 0.5 g/m³ of TP, while 120 g/m³ of the flocculant removed around 40 percent less. According to the dependence of total P removed on the flocculant dose calculated by its active ingredient Fe³⁺, ferric sulphate flocculant is the most effective at doses of up to 60–80 g/m³ of Fe³⁺. The use of ferric sulphate may be limited by its impact on pH and sulphate concentrations in the effluent wastewater. If pH is not additionally adjusted, a maximum concentration of 70 gFe³⁺/m³can be used in order to maintain the pH of wastewater above 6.5 and to keep final sulphate concentration below 300 mg/l. In summary, a maximum of 70 gFe³⁺/m³ can be used based on the total P removal efficiency and limiting factors. Such dose could remove 28 g total P/m³ from the wastewater. Since the permissible total P concentration in effluent wastewater is 4.0 mg/l, it is reasonable to use the ferric sulphate flocculant, containing 11.5 % of Fe³⁺ as an active ingredient, for treating wastewater with an initial total P concentration of up to 32 mg/l.

Keywords: ferric sulphate, meat processing wastewater, total P removal.

Article DOI: http://doi.org/10.15544/RD.2015.077