Reduction of solid content in starch industry wastewater by microfiltration

Wastewater obtained in the production process of wheat starch and vital wheat gluten was treated by microfiltration through a ceramic tubular membrane with 200 nm pore sizes. The consumption of process water would thus be reduced, the starch would be recovered to a greater extent and the wastewater problem would consequently be solved. Reduction of the occurrence of polarization layer on the membrane and the constant wastewater permeate flux through the membrane was maintained by inserting of the mixer Kenics inside the membrane tube. The maximum value of the permeate flux (24 L m⁻² h⁻¹) without the use of a static mixer was achieved at 3 × 10⁻⁵ Pa and at a flow rate of 150 L/h, for wastewater samples initially allowed to settle for 4 h prior microfiltration. Under the very same conditions of the working parameters, the use of a static mixer enables a flux that is up to two or three times more intensive compared to the values obtained without using a mixer. Microfiltration reduces the wastewater dry matter from 11 000 to 4000 mg/L, lessens the chemical oxygen demand by 74%, i.e. from 21 000 to 5100 mgO₂/L and significantly decreases the values of the suspended matter, namely from 9000 to 300 mg/L.