Preparation And Utilization Of Bioflocculant For Deep-treatment Of Straw Papermaking Wastewater

Papermaking industries consume large amount of fresh water and discharge wastewater with heavy pollution. Expecially, straw papermaking wastewater contains high concentration of COD and color, which is difficult to remove with normal secondary treatment technologies. In addition, large amount of excess sludge is generated through biological treatment process. However, it is required by cleaner production specifications that the quantity of fresh water as well as wastewater should be reduced significantly by papermaking industry. It is obvious that wastewater reuse after deep treatment and the utilization of excess sludge may help to achieve this goal.In this paper, the preparation, application and mechanism of a bioflocculant (Papermaking sludge bioflocculant, PSBF) prepared by excess sludge obtained from biological treatment process of straw papermaking wastewater were studied. Results showed that, alkaline hydrolysis was the best preparation method comparing to ultrasonic, thermal and alkaline-ultrasonic treatment, and the optimal alkali dosage was 2.25 g/g TS. PSBF was used for straw papermaking wastewater treatment at optimal dosage of 1 mL·L-1 of PSBF, 110 mL·L-1 of CaCl2 (1% w/w), and pH value of 11. Pilot scale tests showed 68% of COD and 85% of color reduction averagely. Infrared spectra together with other analysis indicated that polysaccharide was the major active component of PSBF for flocculation, which endure temperature fluctuation and long time storage. The flocculating mechanism of PSBF can be explaned by ionic bond and adsorption bridge theory.